NC Machine for producing tangential entry to and exit from a compensated contour

An improved numerically controlled machine tool for controlling movement of a tool along a workpiece contour with compensation for tool radius, which includes an electronic control including:

• an input unit;
• a memory;
• a computer provided with means for arc interpolation and straight line interpolation;
• and a drive arrangement, responsive to the electronic control, for movement of the tool;
• wherein the improvement comprises:
• means for supplying first and second radii which define curvatures of arcs to be made by the tool before the tool comes into contact with the workpiece contour and after the tool leaves contact with the contour;
• means for supplying a rounding signal;
• means, responsive to the rounding signal, for transforming the first and second rounding radii into parameters required by the means for arc interpolation for pointwise calculation of respective entry and exit rounding arcs from the parameters, said entry rounding arc intersecting a starting point of the workpiece contour tangentially and passing via a first tangent to a first prescribed point, said exit rounding arc intersecting an end point of the workpiece contour tangentially and passing via a second tangent to a second prescribed point.