US 4,131,837 AGranted

Machine tool monitoring system

AssigneeThe Boeing Company

InventorWilliam J. Whetham

Life of this patent

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Abstract

During machine tool operation a first set of sensors, referred to as cutter deflection sensors, provides data which is representative of the physical deflection of the cutting tool from a rest position, while a second set of sensors, referred to as position sensors, provides data which is representative of the position of the workpiece mounted on the machine tool relative to a reference or setpoint position. The cutter deflection and workpiece position data are combined to produce a resultant which is representative of the actual position of the cutting tool relative to the workpiece. This resultant is then compared with reference data which is representative of the desired position of the cutting tool relative to the workpiece. The difference between the actual and desired positions is then compared with a preselected tolerance value. The machine tool is then either (1) permitted to continue at its programmed speed, (2) slowed down or (3) stopped, depending on the value of the difference data compared to the tolerance value.

Claims7

Dependent claims

In a numerical control machine tool comprising:

(a) first means for supporting a workpiece relative to a machine reference position such that the position of the workpiece can be ascertained;
(b) second means for supporting a cutting tool means relative to said machine reference position such that the undeflected position of the cutting tool means can be ascertained;
(c) cutting tool means operable to remove material from the workpiece when the machine tool is in operation, said cutting tool means deflecting from a rest position during removal of material from the workpiece;
(d) means for moving said first and second supporting means such that the workpiece and the cutting tool move relative to each other;
(e) means for controlling the movement of the first and second supporting means in accordance with programmed instructions, so as to produce a product of selected configuration and size;
the improvement comprising:
(a) means for determining the position of said first and second supporting means relative to the machine reference position at a given point in time;
(b) means for determining the deflection of said cutting tool means from said rest position during operation of said machine tool at said given point in time;
(c) means for combining the position data and the deflection data in such a manner as to produce a resultant which is representative of the actual position of the cutting tool means relative to the workpiece at said given point in time;
and
(d) means responsive to (1) said resultant, (2) reference data representative of the desired position of the cutting tool means relative to the workpiece at said given point in time, and (3) a preestablished tolerance value to alter the operation of said machine tool, when the difference between said resultant and said reference data reaches a predetermined fraction of said tolerance value, in such a manner as to insure that said product will be within the preestablished tolerance.

8 more elements

A method for monitoring a machine tool operating under the initial control of programmed instructions, comprising the steps of:

(a) initiating machining operation in which a cutting tool removes material from a workpiece under the control of the programmed instructions;
(b) determining the change in position of the machine tool from a reference position at a particular point in time during machining operations, so as to determine the position of the undeflected cutting tool relative to the workpiece;
(c) determining the deflection of the cutting tool from a rest position at the particular point in time;
(d) combining the data obtained as a result of steps (b) and (c) above in such a manner as to produce a resultant which is representative of the actual position of the cutting tool relative to the workpiece at the particular point in time;
(e) calculating the difference between (1) said resultant and (2) a reference value obtained from the programmed instructions which is representative of the desired position of the cutting tool relative to the workpiece;
(f) comparing the difference obtained as a result of step (e) above with a preestablished tolerance value obtained from the programmed instructions;
(g) continuing the control of the machine tool exclusively by the programmed instructions if the difference of step (e) is within a first range relative to the tolerance value;
(h) modifying the programmed instructions to decrease the feedrate of the machine tool if the difference of step (e) is within a second range relative to the tolerance value;
and
(i) stopping the machine tool if the difference of step (e) is greater than said second range.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/815,150Filed 13 Jul 1977 · continuation in part
Priority: 17 Jul 1975
Granted: 26 Dec 1978
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G05B 19/4163
Characterised by control of velocity, acceleration or deceleration: adaptive control of feed or cutting velocity
G05B 19/4065
Characterised by monitoring or safety: monitoring tool breakage, life or condition
G05B 2219/34465
Director, elements to supervisory: safety, control of correct operation, abnormal states
Y10T 408/172
To control infeed: responsive to Tool