GB967999A - Method and device for numerical control - Google Patents

Abstract

967, 999. Numerical control systems. SVENSKA AEROPLAN A. B. Sept. 25, 1961 [Sept. 29,1960] No. 34266/61. Heading G3N. In a numerically controlled milling machine the command signal is recorded and compared with incremental pulses generated by the worktable slide decade by decade, the significance of an incremental pulse being appropriately reduced at each stage. The machine has four controlled movement axes, all identical, and consisting of a motor e.g. 77 and a pulse generater e.g. 78 which emits one pulse for every one hundredth of a millimetre movement of the work-table. One axis only is controlled at a time. The first binary coded numeral read from the tape 1 determines the axis in use and the direction of the movement; the signal being routed by a distributer 5 to set both a selector 33 for energizing the required motor via an unspecified controller 48, and to set a selector 29 for connecting the appropriate pulse generator to a decade counter 94, 95, 96, 97. The second and third coded numerals on the tape indicate tool spindle speed and tool feed rate and these are routed by the distributer 5 to selectors 49 and 63 respectively to affect the controller 48 in an unspecified manner. The fourth, and subsequent coded numerals until the final'stop' indicate the orders of magnitude of the displacement command signal and are all routed by distributer 5 to a selector 64 connected to the decade counter 94, 95, 96, 97. If for example, the first of these codes indicates that the units in use are decimetres, then the selector 64 connects an amplifier 4 to the final output of the decade counter so that one pulse is provided for each decimetre of work-table movement, i.e. the pulse train from 78 is divided by 10<SP>4</SP>. Each pulse supplied to the amplifier 4 causes the tape 1 to be advanced one step. The tape is left blank for as many steps as there are decimetres of work-table movement, and then the next order of magnitude code, e.g. centimetres, is recorded. The selector 64 is moved to the appropriate level of the decade counter and the process continues by stages down to the smallest increment available, at the end of which, the amplifier 4 is stated to stop the work-table motor 77. It is also stated that the feed speed is reduced for the smaller measurement units. In a modification, Fig. 8, (not shown) a separate counter is used to store the incremental command pulses in accordance with a recorded signal instead of using the tape reader as the counter by stepping off the blank steps. In a further modification, Fig. 12, (not shown), the pulse generator 78 is a photo-electric arrangement in which concentric rings on a disc interrupt the light falling on co-operating photocells in the required ratios.