Smooth new approach to machining

Many companies whose engineering departments have `gone electronic’ have carried out CAM programming away from the shop floor, usually back to the CAD office. The obvious drawback with this development is that it fails to tap into a valuable resource: the years of skill and experience of the machine operator.

To allow experienced machine operators to make a contribution to the machining process, Delcam has developed PowerMill, a 3D machining package for the fast creation of cutter paths that contain Non-Uniform Rational B-Splines (NURBS) that can be interpreted by CNC machine-tool controllers to provide faster and more accurate performance.

The machining of curved surfaces can be carried out as a series of NURBS curves rather than the traditional method where a number of short, straight line moves and arcs are interpolated by the controller.

Because the spline information is calculated within PowerMill, it is possible to prevent the tolerance stack-up occurring from other systems when splines are fitted to normally generated straight line cutter paths.

The use of curves in tool path calculation ensures that data starvation of the machine is eliminated and tool movements are more consistent, minimising problems such as dwell marks.

File size can also be reduced. In a comparison made with linear machining, the spline equivalent of a linear file was 60% smaller. Delcam’s new method of spline fitting ensures that splines will never infringe on the part.

The new functionality is intended to exploit the power of new generations of machine tool controllers, such as those from Siemens, that are capable of interpreting the NURBS based data directly.

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