Patent GB-1341714-A (GB)
Title: Numerically-controlled machine tool apparatus with a tracer for generating control programmes
IPC: G05B19/42
Filed: 1971-08-06
Abstract: 1341714 Program control of machining CINCINNATI MILACRON Inc 6 Aug 1971 [6 Aug 1970] 37129/71 Heading G3N Numerically controlled machine tool apparatus, comprising electrically driven (or hydraulically driven using rotary motors and lead screws or a piston and cylinder) X, Y and Z slides Fig.1c (not shown) mechanically connected to rotary or linear feedback transducers 34, 36, 38, is provided with a tracer head (24) adjacent the Z slide and which is movable over a two or three dimensional template or model (29) of a workpiece. Machining is controlled either in a first mode by a punched tape program 20, Fig. 1a, or in a second mode by means of signals from the tracerhead (24) as it traces contours on the model (29), a corresponding model part program being simultaneously produced on tape 130 Fig. 1b for subsequent use as a part program to control either the present, or other, numerical control apparatus. A mode switch 22 is provided for determining the mode of operation. Much of the numerical control system is active in both modes. Operation under control of tape 20. For each slide, for Example the Z, displacement commands from generator 44 take the form of a string of pulses of frequency corresponding to desired tool speed and a signal indicating desired direction of motion fed to converter 52, including counter 66 driven by a high frequency oscillator (not shown), whose output, a pulse train, phase or amplitude modulated in accordance with the input pulse string and the direction signal which determines the sense in which the count of 66 is modified, is fed to comparator 80 whose other input receives a similar pulse train, derived from reference counter 68, whose frequency in the absence of desired slide movement is the same as that of converter 52, and phase modulated by the transducer 34 receiving from converter 72 a pair of sine waves inquadrature, which in converter 74 after modulation are reconverted to pulses. The analogue output of comparator 80, via gate 86 and servoamplifier 92, drives the Z slide until the phase difference between the input signals is zero. The displacement commands are also fed to accumulator 58 comprising a shift register which gives a continuous record of the position of the Z slide with respect to a reference origin. Operation under tracer control. As the tracer (24) moves over model (29) in predetermined coordinate directions, a signal for each slide, for Example (100) for the Z, via buffer amplifier 104 and gate 86 whose other control input is now inhibited by a signal from mode switch 22, provides the input for the servoamplifier 92, to move the slide. Consequent upon slide motion, signals derived from the feedback transducer 34 are fed to comparator 110, whose output in the form of a number of pulses proportional to the deviation, via gate 46, which is now enabled by switch 22 to pass only such output signal, is passed to converter 52 to ensure that its output continues in alignment with that of the transducer signals, as well as to accumulator 58 and hence to computer 116 which processes the information, with the possible addition, via teletype printer 118, of data concerning tool feed, spindle speed and linear curve fitting to provide a part program on punched tape 130 corresponding to the model (29). Checking of production parts. Such parts are inspected by the tracer (24), a selection of points being printed out and used to operate the machine under program control, tool position being monitored.