Patent GB-1196633-A (GB)
Title: Machine Control System
Inventor: PAYNE ROBERT ADDISON
IPC: G05B19/25
Filed: 1967-06-23
Abstract: 1,196,633. Programmed control of machine tools. STEWART WARNER CORP. June 23, 1967 [June 24, 1966], No.29204/67. Heading G3N. A machine tool control system includes an arithmetical combining means responsive to a signal representative of a desired position relative to a reference position a signal representing direction of offset and a manually set signal representing actual tool offset, the combined signals, representative of the tool-size compensated desired position, is compared with a signal representative of the actual tool position to provide a signal for controlling relative movement of between a tool and workpiece to bring them to the compensated position. As shown, Fig. 1, a machine 102 is controlled by a punched tape responsive system contained in a console 100. A workpiece 111 is positioned with respect to a tool 109 by carriages 108, 110 driven by D.C. shunt wound feed motors 104, 106. The control system enables positioning for drilling, and straight milling cuts along directions parallel to the X and Y axes. The control system, Fig. 2, is responsive to a punched tape providing plus and minus X and Y dimension programming in four axes with respect to an adjustable or floating zero reference and the direction of tool offset. The tape is read by a reader 112 and set in co-ordinate command registers 200, 200a and combined with tool offset data from digital thumb-wheel switches forming control 202. The actual position of carriages 108, 110 is determined for each axis by the count in a register, such as 204, responsive to the output of a wheel 206,'driven by the feed motor 104, which produces a pulse for each increment of movement of the carriage. The position pulses are synchronized with the control system clock pulses by a circuit 207 and added or subtracted to the data in the register 204 by a circuit 208 in accordance with the direction of movement detected by a circuit 210 responsive to the phase-relationship of pulses from a pair of photo-cells spaced around the periphery of the pulse wheel. The data contained in the command register 200 is compared with the data in the position register 204 by a subtractor circuit 212. The difference output of the subtractor circuit is transmitted through a detector 214, which stops the carriage when the difference falls to zero, and a detector 216, which reduces the programmed feedrate at a predetermined minimum output, to a motor drive amplifier 218 providing a driving voltage to the motor 104. A reverse detector 220 control the direction of movement of the carriage in dependence on the sign detected by the subtractor 212. The feedrate signal is fed from the reader 112 to a feed speed generator 222 which determines the magnitude of the driving voltage from the amplifier 218. The tool offset demensions are set into the control system by the thumb-wheel switches in decimal form and converted digit-by-digit to a parallel sequence binary-coded decimal form which is combined with the corresponding digit read from the tape, as determined by the direction of offset data, and the result converted to binary rotation and stored in the command register 200.