Patent GB-1180969-A (GB)
Title: Improvements in or relating to Automatic Control of Machining Operations.
IPC: G06F7/66
Filed: 1967-08-15
Abstract: 1,180,969. Programmed control of machine tools. NEW ZEALAND GOVERNMENT PROPERTY CORP. Aug.15, 1967 [Aug.16, 1966], No.37490/67. Heading G3N. Controlled relative motion between a workpiece and a tool in dependence on a point to point stored programme is effected by generating a pulse train, determining distance between successive points, which is converted to co-ordinate pulse trains, representing values to be stored in sine and cosine registers, and pulses are derived from the register for control of axes drive motors; a single instruction from the programme causing straight or arcuate motion and the desired distance of motion causing termination of the pulses and a request for further information. In the control of a milling machine a straight line cut is effected by counting pulses, proportional to the cutting velocity, until the count equals the length programmed. The angle of cut is that initially set in to sine and cosine registers and for an arcuate cut the angle of cut is progressively varied, in dependence on the angular velocity of cut, by adding incremental cosine values to the sine value and subtracting incremental sine values from the cosine value. As shown, a tape reader 1 reads commands in computer language on an 8 hole paper tape 2 and one of seventeen command circuits 3 selected. The pulses from an oscillator 4 are fed to a pulse separator 5 having a plurality of output leads whereby a train of pulses at the input appears sequentially and repetitively on separate output leads. The pulses on the output leads are fed to a sine/cosine generator 7, comprising multi stage reversible binary registers, in which programmed sine and cosine values are inserted, and sine and cosine binary register tails. For a straight cut sine and cosine values are added, least significant number first, respectively to the values in the cosine and sine tails. When a tail is full an output pulse is produced from the last stage and fed on lines 8, 9, by-passing binary coded decimal rate multipliers 11, 10 to output leads 13, 12. For an arcuate cut, the tail pulses are also added or subtracted to the values initially stored in the reversible binary registers and the radius of cut set in manually or from a command circuit 3, tool radius values being set in from switches 14. The pulse trains on leads 12, 13 are fed into servo-amplifiers 15, 16 which control the rotational velocity of printed circuit D. C. motors 17, 18, driving through lead-screws the work-table of a milling machine, not shown. Slotted discs attached to the motor shafts actuate vane switched oscillators 19, 20 producing feedback pulses to the servos 15, 16. A store 21, set from a command circuit 3 and BCDRM 10, counts pulses from the pulse separator 5 and at a certain state stops the input from oscillator 4 to the pulseseparator. Facilities are provided for the manual control of oscillator 4 to determine the cutting speed, the manual rotation of the angular co-ordinates of a programme to a desired angle and the automatic slow down at the end of a cut.