ADAPTIVE CONTROL SYSTEM FOR NUMERICAL CONTROL OF A CUTTING TOOL

• US 3,746,955 A
• Filed: 03/23/1971
• Issued: 07/17/1973
• Est. Priority Date: 03/24/1970
• Status: Expired due to Term

• Current Assignee: Kengo Kobayashi
• Original Assignee: Kengo Kobayashi
• Inventors: Kobayashi, Kengo
• Primary Examiner(s): Vlachos, Leonidas
• Application Number:
  US05/127,221
• Time in Patent Office: 847 Days
• Field of Search: 82/2B,DIG.4,DIG.9 318/571,570,561
• US Class Current: 318/561
• CPC Class Codes: G05B 19/4163 Adaptive control of feed or cutting velocity without NC B23Q15/12
• CPC Class Codes: Y10T 408/08 with means to regulate operation by use of templet, tape, card, or other replaceable information supply
• CPC Class Codes: Y10T 408/16 with control means energized in response to activator stimulated by condition sensor
• CPC Class Codes: Y10T 82/2502 with program control

Abstract

A detector detects the state of load of machine, for example, the torque load of the spindle or the cutting resistance of the tool. Control means connected to the detector compares the detected load with an allowable magnitude and moves the tool away from the workpiece in a specific direction to reduce the load when the detected load exceeds the allowable magnitude thereby providing cutting of the workpiece by the tool at a state of load maintained at a magnitude very close to the allowable magnitude by not exceeding such magnitude.

Claims

1. An adaptive control system for numerical control of a cutting tool cutting a workpiece mounted on a machine spindle rotated about its axis, said control system comprising program means for controlling the movement of the tool in accordance with commands recorded on tape;

a detector for detecting the load condition Q of the machine;

a function generator for generating an allowable load condition q;

a comparator connected to the detector and the function generator for comparing the magnitudes of the load condition Q and the allowable load condition q;

a variable frequency oscillator connected to the comparator for generating compensation pulses having a frequency proportional to the difference between the load condition Q and the allowable load condition q only when the load condition Q is larger than the allowable load condition q;

a pulse distributor;

a reversible counter connected to the pulse distributor and to the oscillator for providing an addition of one to its contents every time the variable frequency oscillator generates the compensation pulses and providing a subtraction of one from the contents thereof every time the pulse distributor generates a distribution pulse in a +X longitudinal axis direction;

drive motors;

a drive circuit connected to the pulse distributor for receiving distribution pulses in +X, -X, +Z and -Z cross axis directions from the pulse distributor and controlling the drive motors in each axis;

a gate connected between the pulse distributor and reversible counter and the drive circuit for blocking the distribution pulse in the +X axis to be supplied to the drive circuit until the contents of reversible counter becomes zero, the compensation pulses being supplied to the drive circuit when the load condition Q in a machining process controlled by a tape command implying an adaptive mode is larger than the allowable load condition q, so that the cutting tool is moved in the +X direction and the load condition Q is reduced, the machining process ends and the cutting tool is returned to the start point of the machining process in the adaptive mode when the contents of the reversible counter reach zero, the command tape, the program means including rewinding means for rewinding at the same time, to the top of the machining process commands to repeat the same processes as those of the first machining process, the end of all the processes in the adaptive mode contained in the command tape being indicated when the compensation pulses are not generated within a machining cycle or when the reversible counter has contents of all zeros within a machining cycle.

2. An adaptive control system for numerical control, as claimed in claim 1, further comprising a Z-counter connected between the pulse distributor and the drive circuit for providing an addition of one to the contents thereof whenever the pulse distributor generates a distribution pulse in the -Z direction, an X-counter for providing an addition of one to the contents thereof whenever the pulse distributor generates a distribution pulse in the +X direction and an oscillator at the cutting tool for providing restoration motion wherein pulses generated by the oscillator are supplied to the drive circuit so that the cutting tool is moved in the +Z direction, and at the same time, one is subtracted from the contents of the Z-counter everytime the pulse is generated, the end of the cutting tool restoration in the Z-axis direction is indicated when the contents of the Z-counter reach zero, the pulses generated after the completion of the cutting tool restoration in the Z-axis direction are supplied to the drive circuit to move the cutting tool in the -X direction, one is subtracted from the contents of the X-counter every time the pulse is generated, and the completion of thE tool restoration is indicated when the contents of the X-counter reach zero.

3. An adaptive control system for numerical control as claimed in claim 1, further comprising means for adjusting the parameters of the speed of revoltuion of the main shaft, the distance between the tool and the center of the main shaft and the type of cutting tool thereby permitting variation of the allowable load condition q.

4. An adaptive control system for numerical control as claimed in claim 1, wherein the load condition Q is divided into three regions in accordance with magnitude of the load condition Q, the three regions comprising a region L wherein the load condition Q is smaller than the allowable load condition q, a region H wherein the load condition Q is larger than the allowable load condition q but smaller than a level which may cause the cutting tool to be broken, and a region D wherein the load condition exceeds the limit to prevent breaking of the cutting tool or the limit at which a protection fuse may blow, the distribution operation of the pulse distributor being temporarily stopped while the load condition Q is in the D region.

5. An adaptive control system for numerical control as claimed in claim 2, further comprising means for command-controlled movement of the cutting tool for a specified period immediately after the reversible counter reaches zero and followed by restoration motion of the cutting tool thereby preventing damage of the cutting tool due to contact with the workpiece in restoration motion.