Machine tools abstract
A numerical control method for controlling various kinds of machine
tools by correcting for thermal displacement. Data relative to thermal
displacement, thermal displacement sampling time, and processing
cycle time is stored in memory. Before each process, the shift of
an absolute position of a machine origin is measured to provide
an initial value. The machine tool is energized and thermal displacement
data is gathered according to a sampling time. The sampling time
is varied according to the degree of thermal displacement. Processing
is performed on the data to correct for the thermal displacement
of the machine tool.
Machine tools claims
What is claimed is:
1. A numerical control method for controlling a numerical control
(NC) machine having an electrical power source for providing power
to operate said numerical control machine, a tool means comprising
a machine tool and a drive means for effecting the machining of
a workpiece, a measuring means for measuring machine tool position,
a memory means for storing data including at least previous-time
thermal displacement data and this-time thermal displacement data,
and a processing means, said processing means being operative by
periodic processing to execute a processing program, comprising
the steps of:
turning on said electrical power source;
storing a thermal-displacement sampling time (Tt) and a processing
cycle time (Tc), in said memory means;
selecting a measurement reference position to serve as a machine
origin;
storing data identifying said machine origin with said memory means;
measuring the shift of an absolute position of said machine origin
as a measurement reference position before every processing, so
that said shift of said absolute position serves as an initial value;
collecting data of an amount of heat generated thermal displacement
of said drive means for a duration of said stored thermal-displacement
sampling time and storing said displacement data in said memory
means as this-time data;
upon reaching said stored thermal displacement sampling time, concurrently
(i) executing adaptation processing which changes the sampling time
of the thermal displacement of said drive means, depending upon
whether or not the thermal displacement of said drive means is within
a range of an allowable error within said processing cycle time,
and (ii) comparison computation processing of the amount of thermal
displacement;
comparing said thermal displacement of said drive means and a minimum
movement setting unit with each other to determine whether or not
said thermal displacement is within a first allowable error;
executing a correction of said thermal displacement if said displacement
is not within said first allowable error;
rewriting said previous-time thermal-displacement data as this-time
data after correction of the thermal displacement; and
executing thermal-displacement correction for said drive means.
2. A numerical control method according to claim 1 further comprising
determining whether an interruption for correction is possible and,
if possible, interrupting said correction of the thermal displacement
of said drive means, including promise items of breaks in said processing
program of processing locations and processing groups during processing;
wherein, interrupting the correction of the thermal displacement
of said drive means always takes place at times other than said
breaks or during running other than automatic running.
3. A numerical control method according to claim 1 including the
steps of:
storing a machine position and moving position measurement time
(Tp) in said memory means;
initializing automatic correction after measurement of said machine
origin;
counting said measurement sampling time of the machine position
and the moving position and comparing said count to said stored
machine position and moving position measurement time;
upon expiration of said stored measurement time, concurrently:
(i) executing an adaptation processing which changes the measurement
sampling time of the machine position and the moving position depending
upon whether or not computation processing of the displacement of
the machine origin and the thermal displacement are within a second
allowable error within said processing cycle time; and
(ii) performing a machine origin displacement operation and comparing
the resulting error and an allowable error value per time with each
other to decide whether or not the machine origin is required to
be measured and corrected;
if correction is required, predicting the displacement of the machine
origin (MotTcf) on the basis of the following equation:
where P is a power exponent representing heat generation with respect
to heat emission; and where k is a machining constant;
comparing (i) a prediction value of the displacement of the machine
origin until the entire processing is completed and (ii) said second
allowable error with each other;
executing at least one of a warning during the automatic operation,
automatic judgement on interruption of machine halt, and the machine
halt, on the basis of said comparison.
4. The method of claim 3 further comprising executing the adaptation
processing of the measurement sampling time of the machine position
and the moving position so as to be repeated until an electric power
source is turned off, regardless of a main processing.
5. A numerical control method according to claim 3 including the
steps of:
executing the measurement and correction of said machine origin
every time interval sampling;
executing automatic judgement on the measurement interruption,
the machine halt, and the displacement measurement and correction
of the machine origin on the basis of the predicted displacement
of the machine origin;
measuring a shift of the absolute position of the machine origin
every measurement sampling time (Tp) of the machine position and
the moving position; and
executing the thermal-displacement correction including correction
processing of the machine origin on the basis of said measured shift.
6. The method of claim 1 further comprising allocating said memory
means such that a correction parameter can be input to said memory
means in order to execute zero-point correction of said measuring
means.
7. A numerical control method according to claim 1 further including
the steps of:
judging reprocessing after measurement and correction depending
upon presence of a finish margin;
bringing the reprocessing to alarm processing after n times; and
executing correction of the thermal displacement including processing
in which position displacement is predicted, warned, measured and
corrected.
8. A numerical control method for controlling a numerical control
(NC) machine having an electrical power source for providing power
to operate said numerical control machine, a tool means comprising
a machine tool and a drive means for effecting the machining of
a workpiece, a measuring means for measuring said machine tool position,
a memory means for storing data including at least previous-time
thermal displacement data and this-time thermal displacement data,
and a processing means, said processing means being operative by
periodic processing to execute a processing program, comprising
the steps of:
turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece
reference position;
storing at least data of a machine origin and said workpiece reference
position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece reference position with said measuring
means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the
measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece reference
position every processing cycle;
correcting for thermal displacement, comprising correction processing
of the workpiece reference position, during possible interruptions
of said program;
storing a thermal-displacement sampling time (Tt) and a processing
cycle time (Tc), in said memory means;
following said turning-on of said electric power source, collecting
data of an amount of heat generated thermal displacement of said
drive means for a duration of said stored thermal-displacement sampling
time and storing said displacement data in said memory means as
this-time data;
upon reaching said stored thermal displacement sampling time, concurrently
executing (i) adaptation processing in which the thermal-displacement
sampling time of said drive means is changed, depending upon whether
or not the thermal displacement of said drive means is within a
range of a first allowable error within a processing cycle time,
and (ii) comparison computation processing of the amount of thermal
displacement; and
executing correction of the thermal displacement of said drive
means on the basis of a comparison of the thermal displacement error
and a minimum movement setting unit with each other.
9. The numerical control method as set forth in claim 8 wherein
said method further comprises:
preparing for correction interruption of the thermal displacement
of said drive means, including promise items of breaks in a processing
program of processing locations and processing groups during processing;
executing an interruption for correction of the thermal displacement
of said drive means at time other than said breaks or during running
other than automatic running; and
storing in said memory means a plurality of thermal-displacement
data to this-time data after said thermal displacement correction
of said drive means.
10. A numerical control method for controlling a numerical control
(NC) machine having an electrical power source for providing power
to operate said numerical control machine, a tool means comprising
a machine tool and a drive means for effecting the machining of
a workpiece, a measuring means for measuring said machine tool position,
a memory means for storing data including at least previous-time
thermal displacement data and this-time thermal displacement data,
and a processing means, said processing means being operative by
periodic processing to execute a processing program, comprising
the steps of:
turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece
reference position;
storing at least data of a machine origin and said workpiece reference
position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece reference position with said measuring
means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the
measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece reference
position every processing cycle;
correcting for thermal displacement, comprising correction processing
of the workpiece reference position, during possible interruptions
of said program;
storing the measurement sampling time (Tp) of an allowable value
of a position error (D) for a machine position and a moving position
in said memory means; initializing automatic correction after measurement
of a workpiece reference position;
counting the measurement sampling time of the machine position
and the moving position;
upon reaching said value Tp, executing adaptation processing which
changes the measurement sampling time of the machine position and
the moving position if said counted sampling time is not within
said time (Tp) of an allowable position error;
repeating said counting and adaptation processing of the measurement
sampling time of the machine position and the moving position until
an electric power source is turned off, regardless of a main processing;
executing the correction of the workpiece reference position such
that the measured error and a second allowable error value per time
are compared with each other to decide whether or not the workpiece
reference position is required to be measured and corrected;
executing prediction of the displacement of the workpiece reference
position (MwtTcf) on the basis of the following equation:
where P is a power exponent representing heat generation with respect
to heat emission; and where k is a machining constant;
comparing a prediction value of the displacement of the workpiece
reference position with a measured value until the difference is
within a third allowable error;
executing at least one of a warning during the automatic operation,
automatic judgment on interruption of machine halt, and machine
halt on the basis of the results in which the prediction value of
the displacement of the workpiece reference position and said third
allowable error are compared with each other.
11. The numerical control method of claim 10 further including
executing said thermal-displacement correction, including processing
in which prediction, warning, measurement and correction are executed,
with respect to the displacement of the workpiece reference position.
12. A numerical control method for controlling a numerical control
(NC) machine having an electrical power source for providing power
to operate said numerical control machine, a tool means and a drive
means for effecting the machining of a workpiece, a measuring means
for measuring machine tool position, a memory means for storing
data including at least previous-time thermal displacement data
and this-time thermal displacement data, and a processing means,
said processing means being operative by periodic processing to
execute a processing program, comprising the steps of:
turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece-mounting
reference-block position;
storing at least data of a machine origin and said workpiece reference
position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece-mounting reference-block position with
said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the
measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece-mounting
reference-block position every processing cycle;
correcting for thermal displacement, comprising correction processing
of the workpiece-mounting reference-block position, during possible
interruptions of said program;
storing a thermal-displacement sampling time (Tt) and a processing
cycle time (Tc), in said memory means;
following said turning-on of said electric power source, collecting
data of an amount of heat generated thermal displacement of said
drive means for a duration of said stored thermal-displacement sampling
time and storing said displacement data in said memory means as
this-time data;
upon reaching said stored thermal displacement sampling time, concurrently
executing (i) adaptation processing in which the thermal-displacement
sampling time of said drive means is changed, depending upon whether
or not the thermal displacement of said drive means is within a
range of a first allowable error within a processing cycle time,
and (ii) comparison computation processing of the amount of thermal
displacement;
executing correction of the thermal displacement of said drive
means on the basis of a comparison of the thermal displacement error
and a minimum movement setting unit with each other.
13. The numerical control method as set forth in claim 12 wherein
said method further comprises:
preparing for correction interruption of the thermal displacement
of said drive means, including promise items of breaks in a processing
program of processing locations and processing groups during processing;
executing an interruption for correction of the thermal displacement
of said drive means at time other than said breaks or during running
other than automatic running; and
storing in said memory means a plurality of thermal-displacement
data to this-time data after said thermal displacement correction
of said drive means.
14. A numerical control method for controlling a numerical control
(NC) machine having an electrical power source for providing power
to operate said numerical control machine, a tool means and a drive
means for effecting the machining of a workpiece, a measuring means
for measuring machine tool position, a memory means for storing
data including at least previous-time thermal displacement data
and this-time thermal displacement data, and a processing means,
said processing means being operative by periodic processing to
execute a processing program, comprising the steps of:
turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece-mounting
reference-block position;
storing at least data of a machine origin and said workpiece reference
position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece-mounting reference-block position with
said measuring means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the
measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece-mounting
reference-block position every processing cycle;
correcting for thermal displacement, comprising correction processing
of the workpiece-mounting reference-block position, during possible
interruptions of said program;
storing the measurement sampling time (Tp) of an allowable value
of a position error (D) for a machine position and a moving position
in said memory means;
initializing automatic correction after measurement of a workpiece-mounting
reference-block position;
counting the measurement sampling time of the machine position
and the moving position;
upon reaching said stored value Tp, executing adaptation processing
which changes the measurement sampling time of the machine position
and the moving position if said counted sampling time is not within
said time (Tp) of an allowable position error, said adaptation processing
being conducted repeatedly until said electric power source is turned
off, regardless of a main processing;
executing the correction of the workpiece-mounting reference-block
position such that the measured error and a first allowable error
value per time are compared with each other to decide whether or
not the workpiece-mounting reference-block position is required
to be measured and corrected;
executing prediction of the displacement of the workpiece-mounting
reference-block position (MwbtTcf) on the basis of the following
equation:
where P is a power exponent representing heat generating with respect
to heat emission; and where k is a machining constant;
comparing a prediction value of the displacement of the workpiece-mounting
reference-block position with a measured value until the difference
is within a second allowable error;
executing at least one of a warning during the automatic operation,
automatic judgment on interruption of machine halt, and machine
halt on the basis of the results in which the prediction value of
the displacement of the workpiece-mounting reference-block position
and the allowable error are compared with each other.
15. The numerical control method of claim 14 further including
executing said thermal-displacement correction, including processing
in which prediction, warning, measurement and correction are executed,
with respect to the displacement of the workpiece-mounting reference-block
position.
16. A numerical control method for controlling a numerical control
(NC) machining having an electrical power source for providing power
to operate said numerical control machine, a tool means and a drive
means for effecting the machining a workpiece, a measuring means
for measuring machine tool position, an electric power source for
providing power to operate said machine, a memory means for storing
data including at least previous-time thermal displacement data,
this-time thermal displacement data and correction values, and a
processing means, said processing means being operative by periodic
processing to execute a processing program, comprising the step
of:
turning on said electrical power source;
storing a machine origin, a specific moving position, an allowable
value of position errors, each of a plurality of thermal-displacement
data, a plurality of sampling time data, and processing cycle time,
in memory means;
thereupon, (i) collecting data defining an amount of heat generated
thermal displacement of said drive means, (ii) counting of a sampling
time of thermal displacement, and (iii) measuring the machine position,
comprising one of the machine origin, the workpiece reference position,
and the workpiece-mounting reference-block position;
executing adaptation processing in which the thermal-displacement
sampling time of said drive means is changed, depending upon whether
the thermal displacement is within a range of a first allowable
error within a processing cycle time;
after measurement of said machine position, which is used as a
reference position, initializing an automatic correction;
counting the measurement sampling time of the machine position
and the moving position;
upon counting to a stored measurement sampling time Tp, concurrently
(i) executing adaptation processing of measurement sampling time
of the machine position and the moving position, (ii) executing
computation processing of the displacement of the moving position
and (iii) executing computation of the thermal displacement of the
machine origin;
on the basis of said corresponding execution step, deciding whether
or not measurement and correction of the moving position and machine
position are required;
if correction of moving position is required, executing prediction
of displacement of the moving position (MmtTcf) on the basis of
the following equation:
where P is a power exponent representing heat generation with respect
to heat emission; and where k is a machining constant;
if correction of machine position is required, predicting the displacement
of the machine position on the basis of the following equation:
where P is a power exponent representing heat generation with respect
to heat emission; and where k is a machining constant;
if correction of machine position is requried, predicting the displacement
of the machine position on the basis of the following equation:
where P is a power exponent representing heat generation with respect
to heat emission; and where k is a machining constant;
comparing the prediction value of the displacement of the moving
position and the allowable value with each other;
executing no correction in the case where the allowable value is
not exceeded;
executing at least one of warning during the automatic operation,
automatic judgment of whether interruption of the measurement is
possible, and measurement and correction of the displacement of
the machine origin, on the basis of the results in which the prediction
of the displacement of the machine origin is executed.
17. The numerical control method as set forth in claim 16 further
comprising:
using, as the moving-position measurement, at least one or in combination
of a reference-block three-fixed point method, a constant deciding
method due to actually measured data and a machine-outside measuring
method;
after correction of the thermal displacement, rewriting the plurality
of thermal displacement data to this-time data;
measuring the shift of the absolute position of the moving position
at each measurement sampling time of the machine position and the
moving position;
alternatively, operating a correction value of the moving position
by the constant deciding method;
reading the operated correction value; and
executing correction of the thermal displacement, including correction
processing of the moving position from a subsequent machine operation.
18. A numerical control method according to claim 16 further comprising
the steps of:
counting up the sampling time of the thermal displacement;
concurrently executing adaptation processing which changes the
sampling time of the thermal displacement of said drive means, depending
upon a fact that the thermal displacement of said drive means is
within a range of the allowable error within the processing cycle
time, and the comparative computation processing of the amount of
thermal displacement;
continuing said adaption processing until said electric power source
is turned off, regardless the main processing;
executing the correction of the thermal displacement of said drive
means by comparing the thermal-displacement error and the minimum
movement setting unit with each other;
preparing the interruption of the correction of the thermal displacement
of said drive means, including promise items of breaks in the processing
program of the processing locations and the processing group during
processing; and
executing correction of the thermal displacement at time other
than the breaks or during running other than automatic running to
execute correction of the thermal displacement including correction
processing of the thermal displacement of said drive means.
19. A numerical control method according to claim 16 further comprising
the steps of:
storing a machine origin, a workpiece reference position, a workpiece-mounting
reference block position, and a plurality of thermal displacement
data, in said memory means;
dividing an interior of the memory means so that input of a correction
parameter can be executed with respect to the memory means in order
to execute zero-point correction of measuring means;
measuring the machine position, comprising at least one of the
machine origin, the workpiece reference position, and the workpiece-mounting
reference-block position, when said electric power source is turned
on;
bringing a correction value entirely to zero with a value of the
measurement serving as an initial value;
counting up the measurement sampling time of the machine position
and the moving position;
executing the displacement correction processing of said machine
position and the correction processing of the displacement of the
moving position, in parallel relation to each other;
performing measurement processing with said machine position having
priority;
executing the correction of the machine origin such that, in the
case where the error is smaller than the error allowable value per
time, no correction is made;
executing prediction of the displacement of the machine origin
(MotTcf) on the basis of the following
executing at least one of warning during the automatic operation,
automatic judgment on interruption of the measurement, and measurement
and correction of the displacement of the moving position, on the
basis of the results in which the prediction of the displacement
of the moving position is executed.
20. A numerical control method according to claim 16 further including
the steps of:
judging reprocessing after measurement and correction depending
upon presence of a finish margin;
bringing the reprocessing to alarm processing after n times; and
executing correction of the thermal displacement including processing
in which position displacement is predicted, warned, measured and
corrected.
21. The numerical control method as set forth in claim 20 further
comprising:
judging processing continuation by an operator, after the machine
halt is automatically executed on the basis of the results in which
the prediction of the displacement of said machine position;
after correction of the thermal displacement, rewriting the plurality
of thermal displacement data to this-time data;
using means corresponding to each of the machine positions to measure
shift of the absolute position of said machine position before every
processing;
reading the shift; and
executing correction of the thermal displacement, including correction
processing of said machine position from a subsequent machine operation.
22. A numerical control method for controlling a numerical control
(NC) machine having an electrical power source for providing power
to operate said numerical control machine, a tool means and a drive
means for effecting the machining of a workpiece, a measuring means
for measuring machine tool position, a memory means for storing
data including at least previous time thermal displacement data,
this time thermal displacement data and correction values, and a
processing means, said processing means being operative by periodic
processing to execute a processing program, comprising the steps
of:
turning-on said electric power source;
storing a machine origin, a specific moving position, an allowable
value of position errors, each of a plurality of thermal-displacement
data, a plurality of sampling time data, and processing cycle time,
in memory means;
thereupon, (i) collecting data defining an amount of generated
heat of thermal displacement of said drive means, (ii) counting
of a sampling time of thermal displacement, and (iii) measuring
the machine position, comprising one of the machine origin, the
workpiece reference position, and the workpiece-mounting reference-block
position and (iv) bringing said correction values entirely to zero
and storing a value of the measurement as an initial value;
executing adaptation processing in which the thermal-displacement
sampling time of said drive means is changed, depending upon whether
the thermal displacement is within a range of an allowable error
within a processing cycle time;
after measurement of said machine position, comprising at least
one of the machine origin, the workpiece reference position and
the workpiece-mounting reference-block position, which is used as
a reference position, initializing an automatic correction;
counting of the measurement sampling time of the machine position
and the moving position;
upon counting to a stored measurement sampling time Tp, concurrently
(i) executing adaptation processing of measurement sampling time
of the machine position and the moving position, and (ii) executing
computation processing of the displacement of the moving position;
executing the correction of the moving position such that the error
and a first allowable error value per time are compared with each
other, to decide whether or not the measurement and correction of
the moving position are required;
if correction of moving position is required, executing prediction
of displacement of the moving position (MmtTcf) on the basis of
the following equation:
where P is a power exponent representing heat generation with respect
to heat emission; and where k is a machining constant;
comparing the prediction value of the displacement of the moving
position and a second allowable value with each other;
executing no correction in the case where the prediction value
does not exceed said second allowable value; and
executing at least one of warning during the automatic operation,
automatic judgment of whether interruption of the measurement is
possible, and measurement and correction of the displacement of
the moving position, on the basis of the results in which the prediction
of the displacement of the moving position is executed.
23. The numerical control method as set forth in claim 22 further
comprising:
using, as the moving-position measurement, any one or in combination
of a reference-block three-fixed-point method, a constant deciding
method due to actually measured data and a machine-outside measuring
method;
judging processing continuation by an operator, after the machine
halt is automatically executed on the basis of the prediction of
the displacement of the moving position;
after correction of the thermal displacement, rewriting the plurality
of thermal displacement data to this-time data;
operating the moving position or operating a correction value of
the moving position by the constant deciding method, every processing,
to correct the measured or operated moving position; and
executing correction of the thermal displacement including prediction,
warning, measurement, correction and the like of the displacement
of the moving position.
24. A numerical control method according to claim 22 including
the steps of:
counting up the sampling time of the thermal displacement;
concurrently executing adaptation processing which fluctuates the
sampling time of the thermal displacement of said drive means, depending
upon a fact that the thermal displacement of said drive means is
within the range of the allowable error within the processing cycle
time, and the comparative computation processing of the amount of
generated heat;
processing the collection of the data of the amount of heat generated
thermal displacement of said drive means, the counting of the thermal-displacement
sampling time, and the adaptation processing of the sampling time
of the thermal displacement of said drive means so as to be repeated
until said electric power source is turned off, regardless the main
processing;
executing the correction of the thermal displacement of said drive
means such that the thermal-displacement error and the minimum movement
setting unit are compared with each other to decide good or bad
judgment of the processing;
interruption of the correction of the thermal displacement of said
drive means, including promise items of breaks in the processing
program of the processing locations and the processing groups during
processing;
always executing the interruption of the correction of the thermal
displacement at time other than the breaks or during running other
than the automatic running; and
executing correction of the thermal displacement, including processing
of correction of the thermal displacement of said drive means.
25. A numerical control method according to claim 22 including
the steps of:
storing a machine origin, a workpiece reference position, a workpiece-mounting
reference block position, and a plurality of thermal displacement
data, in memory means;
dividing an interior of the memory means so that input of a correction
parameter can be executed with respect to the memory means in order
to execute zero-point correction of measuring means;
measuring the machine position, comprising at least one of the
machine origin, the workpiece reference position, and the workpiece-mounting
reference-block position, when said electric power source is turned
on;
bringing a correction value entirely to zero with a value of the
measurement serving as an initial value;
counting up the measurement sampling time of the machine position
and the moving position;
executing the displacement correction processing of said machine
position and the correction processing of the displacement of the
moving position, in parallel relation to each other;
performing measurement processing with said machine position having
a priority;
executing the correction of the machine origin such that, in the
case where the error is smaller than the error allowable value per
time, no correction is made;
executing prediction of the displacement of the machine origin
(MotTcf) on the basis of the following equation:
where P is a power exponent representing heat generation with respect
to heat emission; and where k is a machining constant;
executing prediction of the displacement of the workpiece reference
position (MwtTcf) on the basis of the following equation:
where P is a power exponent representing heat generation with respect
to heat emission; and where k is a machining constant;
executing prediction of the workpiece-mounting reference-block
position (MwbtTcf) on the basis of the following equation:
executing at least one of warning during the automatic operation,
automatic judgment on interruption of the measurement, and measurement
and correction of the displacement of the moving position, on the
basis of the results in which the prediction of the displacement
of the moving position is executed.
26. The numerical control method as set forth in claim 25 further
comprising:
judging processing continuation by an operator, after the machine
halt is automatically executed on the basis of the results in which
the prediction of the displacement of said machine position;
after correction of the thermal displacement, rewriting the plurality
of thermal displacement data to this-time data;
using means corresponding to each of the machine positions to measure
shift of the absolute position of said machine position before every
processing;
reading the shift; and
executing correction of the thermal displacement, including correction
processing of said machine position from a subsequent machine operation.
27. A numerical control method according to claim 22 further including
the steps of:
judging reprocessing after measurement and correction depending
upon presence of a finish margin;
bringing the reprocessing to alarm processing after n times; and
executing correction of the thermal displacement including processing
in which position displacement is predicted, warned, measured and
corrected.
28. A numerical control method for controlling a numerical control
(NC) machine having an electrical power source for providing power
to operate said numerical control machine, a tool means comprising
a machine tool and a drive means for effecting the machining of
a workpiece, a measuring means for measuring said machine tool position,
a memory means for storing data including at least previous-time
thermal displacement data and this-time thermal displacement data,
and a processing means, said processing means being operative by
periodic processing to execute a processing program, comprising
the steps of:
turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece
reference position;
storing at least data of a machine origin and said workpiece reference
position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece reference position with said measuring
means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the
measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece reference
position every processing cycle;
correcting for thermal displacement, comprising correction processing
of the workpiece reference position, during possible interruptions
of said program;
judging reprocessing after measurement and correction depending
upon presence of a finish margin;
bringing the reprocessing to alarm processing after n times; and
executing correction of the thermal displacement including processing
in which position displacement is predicted, warned, measured and
corrected.
29. A numerical control method for controlling a numerical control
(NC) machine having an electrical power source for providing power
to operate said numerical control machine, a tool means comprising
a machine tool and a drive means for effecting the machining of
a workpiece, a measuring means for measuring said machine tool position,
a memory means for storing data including at least previous-time
thermal displacement data and this-time thermal displacement data,
and a processing means, said processing means being operative by
periodic processing to execute a processing program, comprising
the steps of:
turning on said electrical power source;
selecting a measurement reference position to serve as a workpiece
reference position;
storing at least data of a machine origin and said workpiece reference
position in said memory means;
executing zero-point correction of said measuring means;
measuring said workpiece reference position with said measuring
means when said electric power source is turned on;
bringing correction values entirely to zero with a value of the
measurement by said measuring means serving as an initial value;
measuring the shift of an absolute position of the workpiece reference
position every processing cycle;
correcting for thermal displacement, comprising correction processing
of the workpiece reference position, during possible interruptions
of said program;
judging reprocessing after measurement and correction depending
upon presence of a finish margin;
bringing the reprocessing to alarm processing after n times; and
executing correction of the thermal displacement including processing
in which position displacement is predicted, warned, measured and
corrected.
Machine tools description
FIELD OF THE INVENTION
The present invention relates to a numerical control method of
controlling various kinds of machine tools, laser processing machines,
electric discharge machining apparatus, robots, measuring instruments
the like, that is, numerical control machines or the like and, more
particularly, to the correction of thermal displacement.
BACKGROUND OF THE INVENTION
It is a well-known that the thermal displacement of a machine tool
or a numerical control machine tool is influenced generally by the
temperature environment in which the machine tool is installed,
for example, the room temperature, the temperature distribution,
or the radiant heat applied to the machine tool. The thermal displacement
also depends on the heat generated by the machine tool per se such
as, for example, heat due to running of a spindle system, a drive
system or sliding parts. Other sources of heat may be heat from
a hydraulic-pressure generating apparatus serving as a power source
for the machine tool, heat of a hydraulic fluid transmitted to the
machine tool through piping and hydraulic control instruments, heat
generated due to machining or processing, heat of chips or machining
oil, heat generated from a driving motor or a control apparatus,
or the like.
As a countermeasure to prevent such thermal displacement, a direct
compensation system has been proposed in which thermal displacement
of a system is estimated. The system is then operated with an integrated
power given to a drive system. Position correction is applied to
correct for thermal displacement at each .delta.t, as disclosed
in Japanese Patent Laid-Open No. SHO 63-256336 entitled "A
method of correcting thermal displacement of a ball screw in an
NC machine". The periods .delta.t are identical in this conventional
embodiment.
Further, other indirect techniques are known. For example, there
is a method in which a cooling oil maintained at low temperature
is recirculated about a bearing structure for a spindle in order
to suppress generated heat of the spindle, a method in which a cooling
oil maintained at low temperature flows through a hollow ball screw
to maintain the ball screw at predetermined or constant temperature
in order to suppress generated heat of a drive system, a method
in which a cooling oil maintained at low temperature flows through
the inside of a sliding part to maintain the sliding part at predetermined
or constant temperature in order to eliminate generated heat of
the sliding part, a method in which a cooling oil maintained at
low temperature flows through the inside of each structural part
of a machine tool in order to cope with temperature distribution
within a room, to reduce influence of a difference in the temperature
distribution, a method in which temperature of a machining oil is
maintained constant, and the like, these methods have already been
put into practice in part.
In these methods, however, it is also a well-known fact that equipment
and/or installation costs is raised with an increase in the correction
accuracy. Further, where the above-described methods are used, it
is also a fact that the correction accuracy under changing machining
conditions fall short of expectations.
Prior to the present invention, thermal displacement in an existing
system has been measured by simulated operation with a machining
center serving as a model, according to the following methods and
with the following results:
I. Operation No. 1
A. Measuring Method:
(1) The machine used was a vertical machining center having: a
semi-closed feed-back control system.
(2) Simulated-running moving axes were X, Y and Z axes, as seen
in FIGS. 21(a) and 21(b).
(3) Displacement measuring axes were the X-axis/Y-axis (each of
which subject due to an absolute-value measurement by a laser-measuring
system) as seen in FIG. 21(a).
(4) A workpiece 102 reference-position measurement was made for
X-axis/Y-axis (both using the same first touch probe 101) and for
spindle 104 along a Z-axis (using a second touch probe 103) as seen
in FIGS. 21(a) and 21(b).
(5) The measurement procedure was executed in accordance with the
following steps: First, the vertical machining center, the measuring
instruments and the like were left alone in a room whose temperature
was 20.degree..+-.0.5.degree. C. for seventy-two (72) hours or more.
Secondly, a power source was turned on. Thirdly, returning to the
origin was practiced. Fourthly, a workpiece reference position was
measured: X, Y and Z. Fifthly, the laser measuring system was set
to 0 (zero). Sixthly, the machine was moved to a 0 (zero) point.
Seventhly, measurement was executed due to the laser measuring system
having an accuracy at which the machine is in the 0 position. Eighthly,
a workpiece reference position was measured. Ninthly, measurement
was done due to the laser measuring system at a position of a 6-12
drilled bore. Tenthly, simulated running was done, one or five times.
Eleventhly, the workpiece reference position was measured. Twelfthly,
a position of a 6-12 drilled bore was measured by the laser measuring
system. Thirteenthly, the above-described steps 2.about.12 were
executed repeatedly. Fourteenthly, an electric power source was
turned off.
(6) The simulated running conditions were such that a program was
prepared with a workpiece illustrated in FIG. 22 being assumed,
and idle-runs were conducted with the workpiece not being mounted.
Processing was estimated such that an upper surface was rough-processed
with five (5) divisions and was finish-milled, was 6-12 drilled,
was 7-8.2 drilled, and was 7-10 thread machining (tapped).
B. Results:
(1) A change or variation of the machine 0-point position accuracy
with time was experienced, as illustrated in FIG. 23 (X-Y measurement
using a laser measuring system). Specifically, the X-coordinates
move gently toward a minus direction through 4 .mu.m substantially
without fluctuation and, subsequently, are restored gently until
2.6 .mu.m. Also, the Y-coordinates move gently toward a plus direction
through 10.03 .mu.m substantially without fluctuation.
(2) A change in X, Y and Z workpiece reference positions with time
was experienced, as illustrated in FIG. 24. Specifically, the X-coordinates
generally and steadily change by +12 .mu.m over about eight (8)
hours without fluctuation. However, the Y-coordinates experience
an initial decrease with a gradual change of +11 .mu.m over about
eight (8) hours while the Y-coordinates are fluctuated a little
through 3.about.5 .mu.m. Thirdly, Z-coordinates retain a change
of -8 .mu.m over about eight (8) hours while the Z-coordinates are
fluctuated a little through 1.1.about.2 .mu.m.
(3) A change of a first bore, a fourth bore and a sixth bore of
the 6-12 drilled bores is as illustrated in FIG. 25 (measurement
is made by the laser measuring system). That is, first, a position
of the first bore changes through 2.38 .mu.m in an X-minus direction
and, subsequently, is restored to plus 0.47 .mu.m and changes through
6.83 .mu.m in a Y-plus direction. Secondly, a position of the fourth
bore changes through 8.22 .mu.m in the X-minus direction and changes
through 3.96 .mu.m in the Y-plus direction. Thirdly, a position
of the sixth bore changes through 2.22 .mu.m in the X-minus direction
and, subsequently, changes to plus 0.63 .mu.m; it also changes through
3.96 .mu.m in the Y-minus direction.
II. Operation No. 2
Another conventional measuring method will next be described below.
A. Measuring Method:
(1) The machine used was a vertical machining center having a semi-closed
feed-back control system.
(2) The simulated-running moving axis was the X-axis.
(3) The displacement measuring axis was the X-axis (an absolute-value
measurement due to a laser-measuring system).
(4) A workpiece 102 reference-position measurement was made for
the X-axis/Y-axis (both using the same touch probe 101) and for
the Z-axis (using a second 103 touch probe). Reference can be made
to FIGS. 21(a) and 21(b) regarding installation or arrangement conditions.
(5) The measurement procedure was executed in accordance with the
following steps: First, the vertical machining center, the measuring
instruments and the like were left alone in a room whose temperature
was 20.degree..+-.0.5.degree. C. for seventy-two (72) hours or more.
Secondly, a power source was turned on. Thirdly, returning to the
origin was practiced. Fourthly, a workpiece reference position was
measured; X, Y and Z. Fifthly, the laser measuring system was set
to 0 (zero). Sixthly, X-axis 10 mm-pitch position accuracy was measured
(using laser measuring system). Seventhly, machine 0-point position
accuracy was measured using the laser measuring system. Eighthly,
simulated running was conducted a) one time of 250* 300 block processing
program, b) continuously in accordance with a program of 250*300
block processing, c) continuously in accordance with a program of
movement of rapid traverse and cutting feed through five (5) cycles,
and d) continuously of a program of movement of rapid traverse and
cutting feed through ten (10) cycles. Ninthly, measurement of machine
0-point position accuracy and measurement of X-axis 10 mm-pitch
position accuracy due to the laser measuring system were executed.
Tenthly, the workpiece reference position was measured for axes
X, Y and Z. Eleventhly, the electric power source was turned off.
Twelfthly, the above-described steps 2.about.11 were executed repeatedly.
(6) The simulated running conditions were such that a workpiece
illustrated in FIG. 22 was assumed, and the aforesaid simulated
running a) and b) were such that only movement of the X-axis was
programmed, other axis movement was not practiced. Also, a program
was prepared by dwell timing in place of the axis movement and movement
energy of only the X-axis was the same as that of actual running.
In short an attempt was made so as not to be influenced from axes
other than the X-axis. The simulated running of the aforesaid c)
and e) was such that 100 mm of rapid traverse and 50 mm (F200 mm/min)
of cutting feed were repeated three times, and idle running was
made without mounting of a workpiece with the above repeating serving
as a program. Processing was estimated such that an upper surface
was rough-processed with five (5) divisions and was finish-milled,
was 6-12 drilled, was 7-8.2 drilled, and was 7-10 screw-drilled
(tapped).
B. Results:
(1) A change or variation of the workpiece reference positions,
that is, the X, Y and Z positions due to simulated running according
to conditions a) and b) above, and the X-axis machine 0-point position
accuracy is as illustrated in FIGS. 26 and 27. According to FIGS.
26 and 27 first, fluctuation of the workpiece reference position
at running of only the X-axis is not limited to the X-axis, but
fluctuates together with Y and Z. Secondly, if running is done continuously
at a constant cycle, the workpiece reference position is stabilized
or becomes stable. If, however, the machine is halted, the workpiece
reference position is fluctuated sensitively. Thirdly, the change
of the X-axis machine 0-point accuracy changes together with running,
but gradually becomes stable with running time. It will be understood
that a maximum value is about 7 .mu.m.
(2) A change of a position for each moving point due to the results
of the simulated running in according to conditions c) and d) is
as illustrated FIGS. 28.about.31. According to FIGS. 28.about.31
it will be seen that, first, the position of each part of the X-axis
is sensitively fluctuated with movement running of the X-axis; secondly,
a change in position of the X-axis is restored at the considerable
rate or ratio to the initial or early condition by halt of the simulated
running, and the restoring differs due to intervals of the halt
period or duration; thirdly, positional accuracy of X+200. mm is
fluctuated unsteadily even at the continuous running of a constant
cycle; and fourthly, the positional accuracy of X-250. mm becomes
substantially stable at continuous running of a constant cycle.
As appearing from the data of the above-described experimental
results which do not include cutting processing, in order to compensate
or correct the machine position and the moving position which vary
with time, i.e. hourly, use of only the simple methods proposed
until now cannot provide the necessary correction of the positional
fluctuation the entire machine. Further, it is impossible for the
simple method to execute automatic correction under the control
of an operator.
The conventional correction of thermal displacement is directed
to a method in which generated heat is removed, as described previously,
so that an objective temperature is approached as closely as possible.
Alternatively, the conventional correction uses a method in which
generated heat due to integrated power which causes thermal displacement
is compensated by multiple position corrections. Since the conventional
correction techniques do not compensate for compounded thermal displacement,
the conventional correction has several problems. First, the accuracy
of correction of the thermal displacement is low. Moreover, the
former case necessitates a cooling device and structures, making
the apparatus cost high.
In view of the aforesaid experimental results, it has been desired
to apply the numerical control apparatus to a system which can cope
with the above problems, in order to accurately or exactly grasp
the accuracy of the machine position and the moving position which
vary over time, to execute feed-back correction, and thereby to
provide machining at high accuracy.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
numerical control method which is capable of correcting compounded
thermal displacement with high accuracy and, further, is capable
of realizing such correction at low cost.
According to a first embodiment, there is provided a numerical
control method comprising the steps of:
possessing a plurality of thermal-displacement data, a thermal-displacement
sampling time and a processing cycle time in memory means;
causing a measurement reference position to serve as a machine
origin;
possessing data of the machine origin within the memory means;
dividing an interior of the memory means such that input of a correction
parameter can be executed with respect to the memory means in order
to execute zero-point correction of measuring means;
measuring shift of an absolute position of a machine origin as
a measurement reference position before every processing, so that
the shift of the absolute position serves as an initial value;
turning of an electric power source;
simultaneously executing collection of data of an amount of generated
heat of thermal displacement of a ball screw and counting of a thermal-displacement
sampling time;
counting up the thermal-displacement sampling time;
simultaneously executing adaptation processing which fluctuates
the sampling time of the thermal displacement of the ball screw,
depending upon whether or not the thermal displacement of the ball
screw is within a range of an permissible error within processing
cycle time, and comparison operation processing of the amount of
thermal displacement;
executing correction of the thermal displacement of the ball screw
such that the error of the thermal displacement and a minimum movement
setting unit are compared with each other to execute good or bad
judgment of the processing;
preparing interruption of correction of the thermal displacement
of the ball screw, including promise items of breaks in a processing
program of processing locations or processing groups during processing;
always executing the interruption of correction of the thermal
displacement of the ball screw at time other than the breaks or
during running other than automatic running; and
rewriting the plurality of thermal-displacement data to this-time
data after correction of the thermal displacement, to execute thermal-displacement
correction including processing of correction of the thermal displacement
of the ball screw.
The method of thermal-displacement correction according to the
first embodiment reduces positional displacement of the machine
origin, and reduces thermal displacement of the ball screw.
Advantages of the first embodiment are as follows. That is, it
is possible to bring the shift or deviation in position of the reference
position to a value within 5 .mu.m by the thermal displacement correction
of the machine origin, if the permissible value is designated in
the aforesaid experimental results. Further, it is possible to bring
the shift or deviation in position of the reference position to
a value within 5 .mu.m by the thermal displacement correction of
the machine origin, if the permissible value is designated in the
aforesaid experimental results, and it is possible to process the
thermal displacement of the ball screw with correction sensitivity
within the minimum moving unit.
According to a second embodiment, there is provided a numerical
control method including the steps of:
initializing automatic correction after measurement of the machine
origin;
counting the measurement sampling time of the machine position
and the moving position;
counting up the measurement sampling time of the machine position
and the moving position;
executing adaptation processing which fluctuates the measurement
sampling time of the machine position and the moving position depending
upon a fact that operation processing of the displacement of the
machine origin and the thermal displacement are within the permissible
error within the processing cycle time;
executing the adaptation processing of the measurement sampling
time of the machine position and the moving position so as to be
repeated until an electric power source is turned off, regardless
of a main processing;
executing the correction of the machine origin such that the error
and an permissible error value per time are compared with each other
to decide whether or not the machine origin is required to be measured
and corrected;
executing prediction of the displacement of the machine origin
on the basis of the following equation:
comparing a prediction value of the displacement of the machine
origin until the entire processing is completed and the permissible
error with each other;
executing warning during the automatic operation, automatic judgment
on interruption of machine halt, and the machine halt on the basis
of the results in which the prediction value of the displacement
of the machine origin and the permissible error are compared with
each other;
after the machine halt is executed automatically, judging processing
continuation by an operator;
preparing the interruption of the machine halt, including promise
items of breaks in the processing program of the processing locations
and the processing groups during processing;
always executing the interruption of the machine halt at time other
than the breaks or during running other than automatic running;
and
executing the thermal-displacement correction including processing
in which prediction, warning, measurement and correction are executed
with respect to the displacement of the machine origin.
The method of thermal-displacement correction according to the
second embodiment monitors the positional displacement of the machine
origin and acts to bring the thermal displacement to a value within
an permissible error.
Advantages of the second embodiment are as follows. That is, it
is possible to bring the shift or deviation in position of the reference
position to a value within 5 .mu.m by the thermal displacement correction
of the machine origin, if the permissible value is designated in
the aforesaid experimental results, or, in addition to this advantage,
it is possible to process the thermal displacement of the ball screw
with correction sensitivity within the minimum moving unit. In addition,
it is monitored whether or not it is possible to bring the displacement
of the machine origin to a value within the permissible error till
completion of the processing, and it is possible to prevent that
the workpiece is brought to defective one, by warning, measuring
and correction.
According to a third embodiment, there is provided a numerical
control method including the steps of:
executing the measurement and correction of the machine origin
every time interval sampling;
executing automatic judgment on the measurement interruption, the
machine halt, and the displacement measurement and correction of
the machine origin on the basis of results in which the prediction
of the displacement of the machine origin is executed;
measuring shift of the absolute position of the machine origin
every measurement sampling time of the machine position and the
moving position;
reading this shift; and
executing the thermal-displacement correction including correction
processing of the machine origin from a subsequent machine operation.
The method of thermal-displacement correction according to the
third embodiment reduces positional displacement of the machine
origin.
Advantages of the third embodiment are as follows. That is, it
is possible to bring the shift or deviation in position of the reference
position to a value within the minimum movement setting unit by
the thermal displacement correction of the machine origin, in the
aforesaid experimental results, and it is possible to process the
thermal displacement of the ball screw with correction sensitivity
within the minimum moving unit. In addition, it is monitored whether
or not it is possible to bring the displacement of the machine origin
to a value within the permissible error till completion of the processing,
and it is possible to prevent that the workpiece is brought to defective
one, by warning, measuring and correction.
According to a fourth embodiment, there is provided a numerical
control method comprising the steps of:
causing a measurement reference position to serve as a workpiece
reference position;
possessing at least data of a machine origin and a workpiece reference
position in memory means;
dividing an interior of the memory means so that input of a correction
parameter can be executed with respect to the memory means in order
to execute zero-point correction of measuring means;
always measuring the workpiece reference position when an electric
power source is turned on;
bringing correction values entirely to zero with a value of the
measurement serving as an initial value, to measure shift of an
absolute position of the workpiece reference position every processing;
reading the shift; and
executing correction of thermal displacement including correction
processing of the workpiece reference position, from a subsequent
machine operation.
The method of thermal-displacement correction according to the
fourth embodiment reduces positional displacement of the workpiece
reference position.
Advantages of the fourth embodiment are as follows. That is, centering
is made by the specific position of the workpiece, and this is called
"workpiece reference position", to execute processing.
It is possible to bring the shift or deviation in position to a
value within 5 .mu.m by the thermal displacement correction of the
reference position, if the permissible value is designated in the
aforesaid experimental results.
According to a fifth embodiment, there is provided a numerical
control method including the steps of:
possessing a plurality of thermal-displacement data, a thermal-displacement
sampling time and a processing cycle time in the memory means;
simultaneously executing, together with turning-on of an electric
power source, collection of an amount of generated heat of thermal
displacement of a ball screw and counting of sampling time of thermal
displacement;
counting up the sampling time of the thermal displacement;
simultaneously executing adaptation processing in which the thermal-displacement
sampling time of the ball screw is fluctuated, depending upon a
fact that the thermal displacement of the ball screw is within a
range of an permissible error within processing cycle time, and
comparison operation processing of the amount of thermal displacement;
executing correction of the thermal displacement of the ball screw
such that the thermal displacement error and a minimum movement
setting unit are compared with each other to perform good or bad
judgment of the processing;
preparing correction interruption of the thermal displacement of
the ball screw, including promise items of breaks in a processing
program of processing locations and processing groups during processing;
always executing the interruption of correction of the thermal
displacement of the ball screw at time other than the breaks or
during running other than automatic running; and
rewriting the plurality of thermal-displacement data to this-time
data after correction of the thermal displacement, to execute thermal-displacement
correction including correction processing of the thermal displacement
of the ball screw.
The method of thermal-displacement correction according to the
fifth embodiment reduces thermal displacement of the ball screw.
Advantages of the fifth embodiment are as follows. That is, centering
is made by the specific position of the workpiece, and this is called
"workpiece reference position", to execute processing.
It is possible to bring the shift or deviation in position to a
value within 5 .mu.m by the thermal displacement correction of the
reference position, if the permissible value is designated in the
aforesaid experimental results. Further, it is possible to process
the thermal displacement of the ball screw with correction sensitivity
within the minimum moving unit.
According to a sixth embodiment, there is provided a numerical
control method including the steps of:
possessing measurement sampling time of an permissible value of
a position error, a machine position and a moving position in memory
means;
initializing automatic correction after measurement of a workpiece
reference position;
counting measurement sampling time of the machine position and
the moving position;
counting up the measurement sampling time of the machine position
and the moving position;
executing adaptation processing which fluctuates the measurement
sampling time of the machine position and the moving position, depending
upon a fact that operation processing of the displacement of the
workpiece reference position and the thermal displacement are within
the permissible error within the processing cycle time;
executing the adaptation processing of the measurement sampling
time of the machine position and the moving position so as to be
repeated until an electric power source is turned off, regardless
of a main processing;
executing the correction of the workpiece reference position such
that the error and an permissible error value per time are compared
with each other to decide whether or not the machine origin is required
to be measured and corrected;
executing prediction of the displacement of the workpiece reference
position on the basis of the following equation:
where parameter "p" as used in this and other equations
throughout this disclosure is a power factor having a value in the
range of 0.5 to 10.0 and preferably 0.8 to 5.0 and is a measure
of heat generation over heat emission
comparing a prediction value of the displacement of the workpiece
reference position until the entire processing is completed and
the permissible error with each other;
executing warning during the automatic operation, automatic judgment
on interruption of machine halt, and the machine halt on the basis
of the results in which the prediction value of the displacement
of the workpiece reference position and the permissible error are
compared with each other;
after the machine halt is executed automatically, judging processing
continuation by an operator;
preparing the interruption of the machine halt, including promise
items of breaks in the processing program of the processing locations
and the processing groups during processing;
always executing the interruption of the machine halt at time other
than the breaks or during running other than automatic running;
and
executing the thermal-displacement correction including processing
in which prediction, warning, measurement and correction are executed
with respect to the displacement of the workpiece reference position.
The method of thermal-displacement correction according to the
sixth embodiment monitors positional displacement of the workpiece
reference position and acts to bring the thermal displacement to
a value within an permissible error.
Advantages of the sixth embodiment are as follows. That is, it
is possible to bring the shift or deviation in position to a value
within 5 .mu.m by the thermal displacement correction of the workpiece
reference position, if the permissible value is designated in the
aforesaid experimental results, or, in addition to this advantage,
it is possible to process the thermal displacement of the ball screw
with correction sensitivity within the minimum moving unit. In addition,
it is monitored whether or not it is possible to bring the displacement
of the workpiece reference position to a value within the permissible
error till completion of the processing, and it is possible to prevent
that the workpiece is brought to defective one, by warning, measuring
and correction.
According to a seventh embodiment, there is provided a numerical
control method including the steps of:
executing the measurement and correction of the workpiece reference
position every time interval sampling;
executing automatic judgment on the measurement interruption, the
machine halt, and the displacement measurement and correction of
the workpiece reference position on the basis of results in which
the prediction of the displacement of the workpiece reference position
is executed;
measuring shift of the absolute position of the workpiece reference
position every measurement sampling time of the machine position
and the moving position;
reading this shift; and
executing the thermal-displacement correction including correction
and processing of the workpiece reference position from a subsequent
machine operation.
The method of thermal-displacement correction according to the
seventh embodiment reduces positional displacement of the workpiece
reference position.
Advantages of the seventh embodiment are as follows. That is, it
is possible to bring the shift or deviation in position to a value
within the minimum movement setting unit, by the thermal displacement
correction of the workpiece reference position, or, in addition
thereto, it is possible to process the thermal displacement of the
ball screw with correction sensitivity within the minimum moving
unit. In addition, it is monitored whether or not it is possible
to bring the displacement of the workpiece reference position to
a value within the permissible error till completion of the processing,
and it is possible to prevent that the workpiece is brought to defective
one, by warning, measuring and correction.
According to an eighth embodiment, there is provided a numerical
control method comprising the steps of:
causing a measurement reference position to serve as a workpiece-mounting
reference-block position;
possessing at least data of a machine origin and a workpiece-mounting
reference-block position in memory means;
dividing an interior of the memory means so that input of a correction
parameter can be executed with respect to the memory means in order
to execute zero-point correction of measuring means;
executing measurement of the workpiece-mounting reference-block
position when an electric power source is turned on;
bringing correction values entirely to zero with a value of the
measurement serving as an initial value;
measuring shift of an absolute position of the workpiece-mounting
reference-block position before every processing:
reading the shift; and
executing correction of thermal displacement including processing
of the correction of the workpiece-mounting reference-block position
from a subsequent machine operation.
The method of thermal-displacement correction according to the
eighth embodiment reduces displacement of the workpiece-mounting
reference-block position.
Advantages of the eighth embodiment are as follows. That is, it
is possible to bring the shift or deviation in position of the reference
position to a value within 5 .mu.m by the thermal displacement correction
of the workpiece-mounting reference-block position, if the permissible
value is designated in the aforesaid experimental results.
According to a ninth embodiment, there is provided a numerical
control method including the steps of:
possessing a plurality of thermal-displacement data, a thermal-displacement
sampling time and a processing cycle time in memory means;
simultaneously executing, together with turning-on of an electric
power source, collection of an amount of generated heat of thermal
displacement of a ball screw and counting of sampling time of thermal
displacement;
rewriting the thermal displacement data to this-time data after
correction of the thermal displacement;
counting up the sampling time of the thermal displacement;
simultaneously executing adaptation processing in which the thermal-displacement
sampling time of the ball screw is fluctuated, depending upon a
fact that the thermal displacement of the ball screw is within a
range of an permissible error within processing cycle time, and
comparison operation processing of a thermal displacement error;
executing correction of the thermal displacement of the ball screw
such that the thermal displacement error and a minimum movement
setting unit are compared with each other to perform good or bad
judgment of the processing;
preparing interruption of correction of the thermal displacement
of the ball screw, including promise items of breaks in a processing
program of processing locations and processing groups during processing;
always executing the interruption of correction of the thermal
displacement of the ball screw at time other than the breaks or
during running other than automatic running; and
rewriting the plurality of thermal-displacement data to this-time
data after correction of the thermal displacement, to execute thermal-displacement
correction including processing of correction of the thermal displacement
of the ball screw.
The method of thermal-displacement correction according to the
ninth embodiment reduces thermal displacement of the ball screw.
Advantages of the ninth embodiment are as follows. That is, it
is possible to bring the shift or deviation in position of the reference
position to a value within 5 .mu.m by the thermal displacement correction
of the workpiece-mounting reference-block position, if the permissible
value is designated in the aforesaid experimental results. In addition
thereto, it is possible to process the thermal displacement of the
ball screw with correction sensitivity within the minimum moving
unit.
According to a tenth embodiment, there is provided a numerical
control method including the steps of:
possessing measurement sampling time of an permissible value of
a position error, a machine position and a moving position in memory
means;
after measurement of the workpiece-mounting reference-block position,
initializing automatic correction;
counting measurement sampling time of the machine position and
the moving position;
counting up the measurement sampling time of the machine position
and the moving position;
executing adaptation processing which fluctuates the measurement
sampling time of the machine position and the moving position, depending
upon a fact that operation processing of the displacement of the
workpiece-mounting reference-block position and the thermal displacement
are within the permissible error within the processing cycle time;
executing the adaptation processing of the measurement sampling
time of the machine position and the moving position so as to be
repeated until an electric power source is turned off, regardless
of a main processing;
executing no correction of the workpiece-mounting reference-block
position in the case where the error is smaller than an permissible
error value per time;
executing correction of the workpiece-mounting reference-block
position such that the error and the permissible error value per
time are compared with each other to decide whether or not the workpiece-mounting
reference-block position is required to be measured and corrected;
executing prediction of the displacement of the workpiece-mounting
reference-block position on the basis of the following equation:
comparing a prediction value of the displacement of the workpiece-mounting
reference-block position until the entire processing is completed
and the permissible error with each other;
executing warning during the automatic operation, automatic judgment
on interruption of machine halt, and the machine halt on the basis
of the results in which the prediction value of the displacement
of the workpiece-mounting reference-block position is compared;
after the machine halt is executed automatically, judging processing
continuation by an operator;
preparing the interruption of the machine halt, including promise
items of breaks in the processing program of the processing locations
and the processing groups during processing;
always executing the interruption of the machine halt at time other
than the breaks or during running other than the automatic running;
and
executing the thermal-displacement correction including processing
in which prediction, warning, measurement and correction are executed
with respect to the displacement of the workpiece-mounting reference-block
position.
The method of thermal-displacement correction according to the
tenth embodiment monitors displacement of the workpiece-mounting
reference-block position and acts to bring the positional displacement
to a value within an permissible error.
Advantages of the tenth embodiment are as follows. That is, it
is possible to bring the shift or deviation in position to a value
within 5 .mu.m by the thermal displacement correction of the workpiece-mounting
reference-block position, if the permissible value is designated
in the aforesaid experimental results, or, in addition thereto,
it is possible to process the thermal displacement of the ball screw
with correction sensitivity within the minimum moving unit. In addition,
it is monitored whether or not it is possible to bring the displacement
of the workpiece-mounting reference-block position to a value within
the permissible error till completion of the processing, and it
is possible to prevent that the workpiece is brought to defective
one, by warning, measuring and correction.
According to an eleventh embodiment, there is provided a numerical
control method including the steps of:
executing the measurement and correction of the workpiece-mounting
reference-block position every time interval sampling;
executing automatic judgment on the measurement interruption, the
machine halt, and the displacement measurement and correction of
the workpiece-mounting reference-block position, on the basis of
results in which the prediction of the displacement of the workpiece-mounting
reference-block position is executed;
measuring shift of the absolute position of the workpiece-mounting
reference-block position every measurement sampling time of the
machine position and the moving position;
reading the shift; and
executing the thermal-displacement correction including correction
and processing of the workpiece-mounting reference-block position,
from a subsequent machine operation.
The method of thermal-displacement correction according to the
eleventh embodiment reduces displacement in position of the workpiece-mounting
reference-block position.
Advantages of the eleventh embodiment are as follows. That is,
it is possible to bring the shift or deviation in position to a
value within the minimum movement setting unit by the thermal displacement
correction of the workpiece-mounting reference-block position, in
the aforesaid experimental results, or, in addition thereto, it
is possible to process the thermal displacement of the ball screw
with correction sensitivity within the minimum moving unit. In addition,
it is monitored whether or not it is possible to bring the displacement
of the workpiece-mounting reference-block position to a value within
the permissible error till completion of the processing, and it
is possible to prevent that the workpiece is brought to defective
one, by warning, measuring and correction.
According to a twelfth embodiment, there is provided a numerical
control method comprising the steps of:
possessing a machine origin, a specific moving position, an permissible
value of position errors, each of a plurality of thermal-displacement
data, a plurality of sampling time data, and processing cycle time,
in memory means;
simultaneously executing, together with turning-on of an electric
power source, collection of an amount of generated heat of thermal
displacement of a ball screw and counting of sampling time of thermal
displacement;
necessarily measuring the machine position (the machine origin,
the workpiece reference position, and the workpiece-mounting reference-block
position), when the electric power source is turned on;
bringing correction values entirely to zero with a value of the
measurement serving as an initial value;
counting up the sampling time of the thermal displacement;
executing adaptation processing in which the thermal-displacement
sampling time of the ball screw is fluctuated, depending upon a
fact that the thermal displacement is within a range of an permissible
error within processing cycle time;
after measurement of the machine position (for example, the machine
origin, the workpiece reference position and the workpiece-mounting
reference-block position, which is used as a reference position),
initializing the automatic correction;
executing counting of the measurement sampling time of the machine
position and the moving position;
counting up the measurement sampling time of the machine position
and the moving position;
executing adaptation processing of measurement sampling time of
the machine position and the moving position;
counting up the measurement sampling time of the machine position
and the moving position;
executing operation processing of the displacement of the moving
position;
executing the correction of the displacement of the moving position
such that the error and the permissible error value per time are
compared with each other;
deciding whether or not measurement and correction of the moving
position are required;
executing predication of displacement of the moving position on
the basis of the following equation:
executing judgment regarding the inside or the outside of the permissible
value, such that the predication value of the displacement of the
moving position and the permissible value are compared with each
other;
executing no correction in the case where the permissible value
is not exceeded;
executing warning during the automatic operation, automatic judgment
on interruption of the measurement, and measurement and correction
of the displacement of the moving position, on the basis of the
results in which the prediction of the displacement of the moving
position is executed;
using, as the moving-position measurement, any one of or using
in combination a reference-block three-fixed-point method, a constant
deciding method due to actually measured data and a machine-outside
measuring method;
after correction of the thermal displacement, rewriting the plurality
of thermal displacement data to this-time data;
measuring shift of the absolute position of the moving position
at each measurement sampling time of the machine position and the
moving position;
alternatively, computing a correction value of the moving position
by the constant deciding method;
reading the operated correction value; and
executing correction of the thermal displacement, including correction
processing of the moving position from a subsequent machine operation.
The method of thermal-displacement correction according to the
twelfth embodiment reduces positional displacement of the moving
position.
Advantages of the twelfth embodiment are as follows. That is, it
is possible to bring a shift or deviation in position of the moving
position to a value within the minimum movement setting unit.
According to a thirteenth embodiment, there is provided a numerical
control method including the steps of:
counting up the sampling time of the thermal displacement;
simultaneously executing adaptation processing which fluctuates
the sampling time of the thermal displacement of the ball screw,
depending upon a fact that the thermal displacement of the ball
screw is within a range of the permissible error within the processing
cycle time, and the comparative operation processing of the amount
of thermal displacement;
processing the collection of the data of the amount of generated
heat of the thermal displacement of the ball screw, start of the
counting of the thermal-displacement of sampling time and adaptation
processing of the sampling time of the thermal displacement of the
ball screw so as to be repeated until the electric power source
is turned off, regardless the main processing;
executing the correction of the thermal displacement of the ball
screw such that the thermal-displacement error and the minimum movement
setting unit are compared with each other to decide good or bad
judgment of the processing;
preparing the interruption of the correction of the thermal displacement
of the ball screw, including promise items of breaks in the processing
program of the processing locations and the processing groups during
processing; and
always executing correction of the thermal displacement at time
other than the breaks or during running other than automatic running
to execute correction of the thermal displacement including correction
processing of the thermal displacement of the ball screw.
The method of thermal-displacement correction according to the
thirteenth embodiment reduces the thermal displacement of the ball
screw.
Advantages of the thirteenth embodiment are as follows. That is,
it is possible to bring a shift or deviation in position of the
moving position to a value within the minimum movement setting unit.
In addition thereto, it is possible to process the thermal displacement
of the ball screw with correction sensitivity within the minimum
moving unit.
According to a fourteenth embodiment, there is provided a numerical
control method including the steps of:
possessing a machine origin, a workpiece reference position, a
workpiece-mounting reference block position, and a plurality of
thermal displacement data, in memory means;
dividing an interior of the memory means so that input of a correction
parameter can be executed with respect to the memory means in order
to execute zero-point correction of measuring means;
necessarily measuring the machine position (the machine origin,
the workpiece reference position, and the workpiece-mounting reference-block
position) when the electric power source is turned on;
bringing correction values entirely to zero with a value of the
measurement serving as an initial value;
counting up the measurement sampling time of the machine position
and the moving position;
executing the displacement correction processing of the machine
position (the machine origin, the workpiece reference position,
and the workpiece-mounting reference-block position) and the correction
processing of the displacement of the moving position, in parallel
relation to each other;
promising the measurement processing with the machine position
(the machine origin, the workpiece reference position, and the workpiece-mounting
reference-block position) having a priority;
executing the correction of the machine origin such that, in the
case where the error is smaller than the error permissible value
per time, no correction is made;
executing prediction of the displacement of the machine origin
on the basis of the following equation:
executing prediction of the displacement of the workpiece reference
position on the basis of the following equation:
executing prediction of the workpiece-mounting reference-block
position on the basis of the following equation:
executing warning during the automatic operation, automatic judgment
on interruption of machine halt, the machine halt, and measurement
and correction of the displacement of the machine origin, on the
basis of the results in which the prediction of the displacement
of the machine position (the machine origin, the workpiece reference
position, and the workpiece-mounting reference-block position) is
executed;
judging processing continuation by an operator, after the machine
halt is automatically executed on the basis of the results in which
the prediction of the displacement of the machine position (the
machine origin, the workpiece reference position, and the workpiece-mounting
reference-block position);
after correction of the thermal displacement, rewriting the plurality
of thermal displacement data to this-time data;
using means corresponding to each of the machine positions to measure
shift of the absolute position of the machine position (the machine
origin, the workpiece reference position and the workpiece-mounting
reference-block position) before every processing;
reading the shift; and
executing correction of the thermal displacement, including correction
processing of the machine position (the machine origin, the workpiece
reference position, and the workpiece-mounting reference-block position),
from a subsequent machine operation.
The method of thermal-displacement correction according to the
fourteenth embodiment reduces positional displacement of the machine
position.
Advantages of the fourteenth embodiment are as follows. That is,
it is possible to bring a shift or deviation in position of the
moving position to a value within the minimum movement setting unit,
or, in addition thereto, it is possible to process the thermal displacement
of the ball screw with correction sensitivity within the minimum
moving unit. In addition, it is possible to bring a shift or deviation
in position of the reference position to a value within 5 .mu.m
by the thermal displacement correction of the machine position (the
machine origin, the workpiece reference position, and the workpiece-mounting
reference-block position), if the permissible value is designated
in the aforesaid experimental results.
According to a fifteenth embodiment, there is provided a numerical
control method comprising the steps of:
possessing a machine origin, a specific moving position, an permissible
value of position errors, a plurality of thermal displacement data,
a plurality of sampling time data, and a processing cycle time,
in memory means;
turning on an electric power source;
simultaneously executing collection of data of generated heat of
the thermal displacement of a ball screw and counting of sampling
time of thermal displacement;
counting up the sampling time of the thermal displacement;
executing adaptation processing which fluctuates the sampling time
of the thermal displacement of the ball screw, depending upon a
fact that the thermal displacement is within a range of the permissible
error within the processing cycle time;
necessarily measuring the machine position when the electric power
source is turned on;
bringing correction values entirely to zero with a value of the
measurement value serving as an initial value;
initializing automatic correction after measurement of the machine
position (the machine origin, the workpiece reference position,
and the workpiece-mounting reference-block position);
executing counting of the measurement sampling time of the machine
position and the moving position;
counting up the measurement sampling time of the machine position
and the moving position;
executing adaptation processing of the measurement sampling time
of the machine position and the moving position;
counting up the measurement sampling time of the machine position
and the moving position;
executing operation processing of the displacement of the moving
position;
executing the correction of the moving position such that the error
and the permissible error value per time are compared with each
other, to decide whether or not the measurement and correction of
the moving position are required;
executing prediction of the displacement of the moving position
on the basis of the following equation:
executing judgment on the inside and outside of the permissible
value such that the prediction value of the displacement of the
moving position and the permissible value are compared with each
other;
executing no correction in the case where the prediction value
does not exceed the permissible value;
executing warning during the automatic operation, automatic judgment
on measuring interruption, and measurement and correction of the
displacement of the moving position, on the basis of the results
in which the prediction of the displacement of the moving position
is executed;
using, as the moving-position measurement, any one of or using
in combination a reference-block three-fixed-point method, a constant
deciding method due to actually measured data and a machine-outside
measuring method;
judging processing continuation by an operator, after the machine
halt is automatically executed on the basis of the prediction of
the displacement of the moving position;
after correction of the thermal displacement, rewriting the plurality
of thermal displacement data to this-time data;
computing the moving position or computing a correction value of
the moving position by the constant deciding method, every processing,
to correct the measured or operated moving position; and
executing correction of the thermal displacement including prediction,
warning, measurement, correction and the like of the displacement
of the moving position
The method of thermal-displacement correction according to the
fifteenth embodiment reduces positional displacement of the moving
position.
Advantages of the fifteenth embodiment are as follows. That is,
it is possible to bring the shift or deviation in position of the
moving position to a value within 5 .mu.m, if the permissible value
is designated in the aforesaid experimental results. It is monitored
whether or not it is possible to bring the displacement of the moving
position to a value within the permissible error till completion
of the processing, and it is possible to prevent that the workpiece
is brought to defective one, by warning, measuring and correction.
According to a sixteenth embodiment, there is provided a numerical
control method including the steps of:
counting up the sampling time of the thermal displacement;
simultaneously executing adaptation processing which fluctuates
the sampling time of the thermal displacement of the ball screw,
depending upon a fact that the thermal displacement of the ball
screw is within the range of the permissible error within the processing
cycle time, and the comparative operation processing of the amount
of generated heat;
processing the collection of the data of the amount of generated
heat of the thermal displacement of the ball screw, the counting
of the thermal-displacement sampling time, and the adaptation processing
of the sampling time of the thermal displacement of the ball screw
so as to be repeated until the electric power source is turned off,
regardless the main processing;
executing the correction of the thermal displacement of the ball
screw such that the thermal-displacement error and the minimum movement
setting unit are compared with each other to decide good or bad
judgment of the processing;
preparing the interruption of the correction of the thermal displacement
of the ball screw, including promise items of breaks in the processing
program of the processing locations and the processing groups during
processing;
always executing the interruption of the correction of the thermal
displacement at time other than the breaks or during running other |