Machine tools abstract
In a monitoring system for the process-accompanying monitoring
or detection of collision or overstress situations in machine tools
(1), comprising a machine control (2) with one or more sensors (4)
for detecting measured signals or measured signal curves, a monitoring
means (6) in which a comparison of the measured signals or measured
signal curves of at least one sensor (4) with stored monitoring
thresholds is performed, and a bidirectional interface (8) between
the monitoring means (6) and the machine control (2), it is provided
that the monitoring means (6), apart from detecting collision or
overstress situations in a machine tool (1) and transferring machine
stop or machine reaction instructions to the machine control (2),
also permanently stores the measured signals or measured signal
curves of the sensors (4) as measured by the sensors (4) before,
during and after a collision or overstress situation and the data
and statuses of the machine control (2).
Machine tools claims
What is claimed is:
1. A monitoring system for in-process monitoring of machine tool
events comprising: control means for controlling the operation of
a machine tool and providing actual data and statuses of the control
means, at least one sensor means for currently monitoring at least
one of machine tool collision events and machine tool overstress
condition events and providing current signal data, first means
for storing said current signal data of the at least one sensor
means for providing current signal data records of said at least
one sensor means, second means for storing threshold data for each
sensor means, means for comparing the current signal data of each
sensor means and the respective threshold data for each sensor means
for determining at least one of machine tool collision events and
machine tool overstress condition events and upon exceeding at least
one of the respective threshold signal data generating an event
detection signal, bidirectional interface means for operating the
control means to immediately control machine tool operation and
to provide said actual data and statuses of the control means in
response to the event detection signal, and means responsive to
the event detection signal for permanently storing a data record
of the event, consisting of the current signal data records of the
first storing means immediately before, during and after the generation
of the event detection signal and said actual data and statuses
of the control means provided by said bidirectional interface whereby
the cause of the at least one of the machine tool collision events
and machine tool overstress condition events is readily determined
on the basis of the said data record of the event.
Machine tools description
BACKGROUND OF THE INVENTION
The invention relates to a monitoring system for in-process monitoring
of collision or overstress situations or conditions by means of
event data recorders associated with machine tools.
Monitoring systems for the in-process monitoring of collision or
overstress situations at machine tools are capable of detecting
machine collisions in process and stopping the machine drives, mostly
only the feed drives, as fast as possible to avoid consequential
damage.
Such in-process monitoring systems are conventionally provided
with an electric interface between the monitoring system and the
machine control to monitor, in-process, the signals of the sensors
in monitoring sections predetermined by the machine control and
to stop the machine via the same interface if collision, overstress
situations or tool breakage, for example, is detected. So far, the
interfaces between the machine tool control and the monitoring system
have been substantially provided in the form of parallel input and
output signals for the SPC control.
Such a parallel interface between the SPC and a tool and in-process
monitoring by a collision and overstress detection system exists,
for example, according to the BAPSI standard (Brankamp-Artis-Prometec
standard interface) which already allows for the transfer of data
words as tool code or cutting code from the NC program to the monitoring
system.
A known control of the Siemens Company comprises a so-called tachograph
which logs operational processes. The latter control system is not
started by a measured or detected collision or overstress event,
but simply logs all operational processes, resulting in the disadvantage
that other reasons for machine damage caused by collision are not
detected.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a monitoring system
for in-process monitoring of collision or overstress situations
at machine tools which, in case of a collision or overstress situation,
not only intervenes into the machine control but moreover permits
a later judgment of the causes of such a collision and overstress
situation.
According to the invention, an in-process monitoring system is
provided for the in-process monitoring or detection of collision
or overstress situations by means of a large permanent memory forming
an event data recorder, e.g., a flash disc, and preferably a field
bus interface between the machine control and the monitoring system,
in connection with a data transfer between the electric interface
of the machine control and the monitoring system as well as in connection
with a sensor signal supplying collision-relevant measured signals.
The invention provides the documentation of collision or overstress
situations at machine tools by an event data recorder in order to
securely detect the causes of such collision and overstress situations
should they occur.
The invention is able to use the field bus interfaces (beside or
instead of the parallel interfaces) only recently offered by the
control manufacturers, which permits a more extensive exchange of
information between the machine control that consists of the stored
program control (SPC) or the NC control.
Such a system for documenting collision or overstress situations
at machine tools by an event data recorder in order to securely
detect the causes of such collision and overstress situations in
the event they occur is presently unknown.
In case of a collision or overstress situation, it has not been
possible, according to prior art, to later determine the causes
that have led to the situation. Since the economic damage by machine
shut-down or machine damage may be considerable in these cases,
the detection of whether technical or human failure was the cause
is of considerable economic importance.
Furthermore, the determination of the cause of damage permits the
detection of defects in the machine components, or in the operational
process, or mistakes of operating persons and avoidance thereof
in the future.
The monitoring system for the in-process monitoring and detection
of collision or overstress situations among machine components or
of tools with machine components or workpieces or of workpieces
with machine components or tools in machine tools at least consists
of (a) one or more sensors for detecting measured signals or measured
signal curves as may be produced at collisions, overstresses or
damage to machine tools, which are to be equated with at least one
direction of force, a resultant force, a pressure, a torque, a motor
output, a motor current, even if it is taken from the values of
the motor current sensor of the control, a vibration, an acceleration,
a distance variation or a structure-borne noise, (b) a monitoring
means consisting of monitoring hardware with software, wherein a
comparison of the measured signals or measured signal curves of
at least one sensor with stored monitoring thresholds is made by
monitoring and evaluating strategies of a known and random type,
such as static thresholds, dynamic thresholds, thresholds of signal
pattern curves etc. in order to provide a corresponding report from
the monitoring system to the machine control to immediately stop
the machine tool or at least its feed drives, and (c) a bidirectional
interface between the monitoring hardware and the machine control
(consisting of the SPC and the NC control), which effects a data
exchange between the machine and the monitoring system and is adapted,
e.g., to activate the monitoring system via a signal as soon as
a feed slide moves and even to transfer spindle-, tool- or even
cutting specific monitoring sections in the form of data words as
different numbers or instructions from the NC or SPC program to
the monitoring system for the purpose of dividing the monitoring
into different monitoring sections, and to transmit machine stop
or at least machine reaction instructions to the machine control
at the moment of detecting collisions or overstress situations.
Optionally, an operating means consisting of operating hardware
with software for operating and/or parameterizing the monitoring
system and/or for visualizing the measured signals may be provided.
Apart from detecting collision or overstress situations in a machine
tool and transferring machine stop or machine reaction instructions
to the machine control, the monitoring system of the invention is
also capable of permanently storing (a) the measured signal data
records (measured signals or measured signal curves) of the sensors
as measured by the sensors before, during and after a collision
or overstress situation and (b) the data and statuses of the machine
control that are of interest as to the detection of the causes of
a collision or overstress situation.
The measured signal data records of the sensors in the working
memory or working storage of the monitoring system are continuously
logged. Only at the detection of the collision or overstress are
the measured data transferred into the permanent memory of the monitoring
system.
The monitoring system continuously logs at least one measured signal
data record (measured signal or a measured signal curve) of each
of the sensors into the working memory or working storage.
Preferably, the monitoring system continuously logs two measured
signal data records of each of the sensors into different working
storage locations with respectively different resolutions as to
time, referred to as "long" and "short". This
means that one measured data record is stored in a small time window
with high resolution and one measured data record is stored in a
larger time window with lower resolution.
Upon detecting the collision or overstress situation, the measured
signal data records are immediately transferred from the working
memory into the permanent storage or permanent memory locations
of the monitoring system and thus to the machine control together
with the report of this situation.
The measured data records (measured signals or measured signal
curves) to be filed in the permanent memory location and having
the "long" resolution as to time preferably start about
2 seconds before the collision or overstress situation and end about
3 seconds thereafter.
The measured data records to be filed in the permanent memory location
and having the "short" resolution as to time preferably
start about 100 milliseconds before the collision or overstress
situation and end about 150 milliseconds thereafter.
Immediately with the report of a collision or overstress situation
from the monitoring system to the machine control, the latter begins,
by means of an appropriate software, to detect data and statuses
of the machine control that are of interest as to the detection
of the causes of a collision or overstress situation and to transfer
them to the monitoring system via the interface between the machine
control and the monitoring system in order to write into the permanent
memory thereof, which serves as an event data recorder, by means
of the software of the monitoring system.
Preferably, the interface between the machine control and the monitoring
system is a field bus interface, such as, for example, a process
data highway or an interbus (as bidirectional interface).
At least one of the following data records and/or status parameters
of the machine control is written into the permanent memory of the
monitoring system with respect to the detection of the causes of
a collision or overstress situation: program name or number that
has been active in the NC control, record number where the NC program
has been stopped by the monitoring systems, present tool number
in the form of the T or p number, operational mode of the machine
(setting, jog, automatic), programmed tool correction values from
the tool correction memory, programmed zero point displacement,
setting of the override switch for feed, setting of the override
switch for spindle speed, speed of the spindles, programmed speed
of the feed slides, present speed of the feed slides, programmed
feed of the feed slides, position or actual position values of the
feed slides, and date and time.
Immediately with the report of a collision or overstress situation
from the monitoring system to the machine control, the monitoring
system can write all states of the signals of the bidirectional
interface between the monitoring system and the machine control,
such as those according to the BAPSI standard, into the permanent
memory thereof.
Immediately with the report of a collision or overstress situation
from the monitoring system to the machine control, all monitoring-relevant
data of the monitoring means, such as, for example, the position
of the monitoring thresholds, the measuring ranges and gain degrees
of the sensors, the characteristic values for filtering the measured
signals, the monitoring mode, such as teach-in, setting etc., can
be written in the permanent memory thereof.
All the measured signal curves, signals, data and statuses to be
stored in the permanent memory of the monitoring system with respect
to a detected collision or overstress situation belong to an unmistakable
and marked data record.
All the measured signal curves, signals, data and statuses of a
data record concerning a collision or overstress situation can be
displayed and, if necessary, printed out by means of the operating
means (operating hardware and software) for operating and/or parameterizing
the monitoring system and/or visualizing the measured signals.
BRIEF DESCRIPTION OF THE DRAWING
The single sheet of drawing is a block diagram of the monitoring
system of the present invention, and depicts the manner in which
threshold and sensor-detected data are compared and utilized to
generate an event detection signal which in conjunction with a bidirectional
interface is utilized to control machine operation and through subsequent
permanent storage and like permanent storage of machine control
data and statuses can be utilized to readily determine the basis
for machine tool collision and/or overstress condition.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The monitoring system for the in-process monitoring or detection
of a collision or an overstress situation in a machine tool 1 with
a machine control 2 shown in the drawing comprises at least one
or more sensors 4 for detecting measured signal data records. The
measured signal data records are supplied to a monitoring means
6 in which a comparison of the measured signal data records of at
least one sensor 4 with stored monitoring thresholds is performed
for detecting collision or overstress situations. In case of the
measured signal data records violating the monitoring thresholds,
the monitoring means 6 supplies a set of instructions to the machine
control 2 in order to immediately stop the machine tool 1 or at
least its feed drives 3.
The machine control is composed of a stored program control SPC
for the machine tool 1 and a NC control for the drives 3. According
to prior art, it is possible to bidirectionally exchange data and
statuses between the stored program control SPC and the NC control.
Between the monitoring means 6 and the machine control 2 a bidirectional
interface 8 is provided, effecting a data exchange between the machine
tool 1 and the monitoring means 6.
The monitoring means 6 comprises a working memory 12 into which
the monitoring means 6 continuously writes at least one measured
signal data record of each of the sensors 4; in this connection,
it is also possible that several measured signal data records of
each of the sensors 4 are continuously written into different working
memory locations of the working memory 12 with a respectively different
resolution in time.
Apart from detecting collision or overstress situations in a machine
tool 1 and transferring machine stop or machine reaction instructions
to the machine control 2 the monitoring means 6 is also capable
of storing the measured signal data records of the sensors 4 as
measured by the sensors before, during and after a collision or
overstress situation as well as the data and statuses of the machine
control 2 in an event data recorder 14 consisting of a permanent
storage or permanent memory, e.g., a flash disc.
Furthermore, the monitoring means 6 may be connected to an operating
means 10. All measured signal curves, signals, data and statuses
of a data record concerning a collision or overstress situation
can be displayed and, if necessary, documented by printout by the
operating means 10 for operating and/or parameterizing the monitoring
system and/or visualizing the measured signal data records.
Although a preferred embodiment of the invention has been specifically
described herein, it is to be understood that minor variations may
be made in the invention without departing from the spirit and scope
thereof, as defined by the appended claims. |