Machining arrangement for closed curve on workpiece - uses photosensor head following curve on drawing, with run-in and run-out lines arranged to obtain optimum join

摘要

The arrangement is intended for machining a workpiece along a closed curve, whilst the tool feed is controlled by a sensor head (26) following a corresponding curve (27) with run-in (31) and run-out (33) line on a drawing (11). The head is rotatable about an axis and carries two photo-resistors with a gap equal to the drawing line thickness between them at a distance ahead of this axis, the resistor signals being used to keep the gap aligned on the line (31,32,27,34,33) of the drawing. The lines (31,33) converge (29) at an acute angle on to the curve (27) whilst the run-in line (31) is at an obtuse angle (e.g. 120 deg.) to the start (32) of this curve and bisects the angle between the end (34) of that curve and the run-out line (33). The distance between the axis and the gap centre exceeds a specified value to ensure that the head (26) crosses over the line (33) as it enters (32,32) the curve (27).