GB1455709A - Numerical control for machine tools - Google Patents

Abstract

1455709 Automatic control of machining cycles SIEMENS AG 31 Dec 1973 [29 Dec 1972] 60191/73 Heading G3N In a numerical control system for controlling relative movement between a tool and a workpiece (in a deep drilling operation), the tool penetrates and retreats from the workpiece in a sequence of cycles (a, bc, d, ef), Fig. 2 (not shown), the infeed, for each cycle excluding the first, taking place initially at a rapid feed to a location adjacent the maximum excursion of the previous feed, followed by a machining feed for an incremental distance (Q), the machining feed at the last in-feed being terminated at the required penetration (BT). The first in-feed takes place at machining feed. At the commencement of each intermediate cycle, the content (Q) of increment register 8 receiving its content from tape reader 1 is added to the content of register 9, the latter having been counted up by the feed-out pulses from pulse source 3 during the previous cycle, the incremented count of 9 thus representing the depth of the next in-feed. The content of register 8 is marginally incremented (50 to 50.5) (Fig. 2) to provide a clearance, and infeed is instigated at rapid feed until, as detected by comparator 11, the content of register 8 exceeds that of register 9, the latter's content being decremented by the feed-in pulses also supplied to drive 6, whence, a signal from the comparator 11 being fed to source 3, further in-feed takes place at the machining feed, until a null content of 9 is detected by unit 12, whence after a pause, rapid out-feed is instigated. The in-feed pulses are counted by register 10, and, during the rapid out feed the content of register 10 is reduced by the out-feed pulses to zero, whence, via null detector 13, the out-feed is terminated, and gate 18 is opened to allow the count in register 9 to be incremented for the next cycle by the content of register 8, the latter having been reset to (Q) at the commencement of the out-feed. For the first cycle, in-feed pulses decrement register 2 until its content, detected by unit 5 is zero whence out feed takes place while register 9 is incremented by the out-feed pulses. After the first cycle, the decrement register 2 is set to the required penetration BT, the drilling operation being terminated by a final rapid out-feed subsequent to the attainment of zero by the register 2. A cycle store 4 is used when a repeated number of like holes are to be drilled. Registers 9, 10 may be set to count in either sense about a predetermined, non-zero number detected by units 12, 13.