GB1421272A - Thread cutting system in numerical control of machine tools - Google Patents

Abstract

1421272 Automatic control of thread-cutting OKUMA MACHINERY WORKS Ltd 6 March 1973 10726/73 Heading G3N A thread-cutting system in a numerical control unit for a machine tool employs a function generator employing two cascaded accumulators the output of which is applied to an arithmetic unit controlling the machine tool to produce a screw thread of progressively varying pitch. As shown, command signals F, L representative of the pitch and length of a threaded portion to be cut on a workpiece 12 are entered into a register 2 from a tape reader 1. The contents of the register and pulses N from a generator 11 coupled to a shaft 13 of a lathe are applied to a function generator 3 to produce varying command signals P which are compared with pulses B 1 from a generator 10 representative of the position of a toolpost 9. The comparision is effected in an arithmetic unit 4 and through a digital-to-analog converter 5 applied to a control unit 6 for a servomotor 7 driving the lead screw 8. The function generator 3 comprises a shift register receiving a signal representative of pitch variation per shaft revolution H and producing an incremental value # which is gated to an arithmetic unit. The contents of the arithmetic represents the present pitch and is held in a further shift register from which it is fed back to the arithmetic unit. The second shift register initially receives the pitch command from the tape and outputs a signal #x representative of the axial movement of the tool post 9 per main shaft pulse. The signal #x is fed through a gate to a second arithmetic unit in a closed loop with a third shaft register, initially fed from the generator 10 the contents of which represent tool position P and form an input to the arithmetic unit 4.