GB1217961A - Automatic numeric machine tool control systems - Google Patents

Abstract

1,217,961. Programmed control of machine tools. GENERAL ELECTRIC CO. March 29, 1968 [April 24, 1967J, No. 15315/68. Heading G3N. A numerically controlled machine tool control system, having a pulse rate modifier comprising a commanded rate register and an interconnected multiplier, is provided with one or more sensor of the physical condition of the tool or workpiece which, through logic circuitry, modify the action of the multiplier. As shown, data relating to a machining operation is read from a tape or punched cards and fed from a unit 19 into an electronic control 20 wherein the pulses from a clock 21 are converted in a unit 26 into a pulse train representative of a commanded feed-rate as modified by a manual feed-rate override 25. The feed-rate pulse train is transformed in a function generator 22 into X and Y axes co-ordinate velocities which, through servo-controls 12, determine the operation of X and Y axes feed drives 23, 24 positioning an element of a machine tool 18. The feed-rate is modified in response to selected ones, or combinations, of the sensed values of vibration, from sensor 27; temperature, from sensor 28, and torque, from sensor 29, through switch contacts 30d-30f of a selector 30. The selected values are fed through diodes 333 to an algebraic combiner 34 in which they are compared with a reference value from a source 38 connected by switch contacts 70a of a selector 70; alternatively the sensed values are compared with corresponding reference values sources 45-47 connected by switch contacts 30a-c of the selector 30. The error between reference and sensed values is applied through an operational amplifier 48 to level sensors 50-53 which determine the sign of the error and whether it is greater than first and second limits. The error level signal from the sensors 50-53 control a pulse-rate selection logic 54, connected to the clock 21 through pulse-rate dividers 55, 56 a pulse rate line 59 and a count up or count down signal on line 61, 62 which alters the feed-rate, from the overide 25 to the unit 26, in a modifier 60. The modified feed-rate, through a digital to analogue converter 67 is additionally applied to a control spindle drive 65. The choice of direct, or modified adaptive control is determined by switch contacts 63a, 63b of a selector 63. When the degree of modification exceeds a set value a switch control 69 opens a contact 69a to terminate the operation of the machine tool.