Free form surface operation
Typical free form surface programs are created using CAD systems or through digitilization of a specimen workpiece. They usually consist of a large number blocks, each with a block length between 0.01 and several mm. Ideally, the programmed contour is moved along at a high feed rate and without velocity variations. The contour error is very small, even at longer cycle times. With respect to a high surface quality, contour errors may be tolerated under certain circumstances if they result in smoother path curves. The requirement profile that results from those conditions can be summarized as follows:
Boundary condition | Requirements to the control |
|---|---|
Contour description via many short blocks | High throughput, high machining velocity of the individual NC blocks. |
High feed rate without velocity variations. | Adjusting the path velocity to the data supply; swift provision of the blocks in the interpolator. |
Minimum contour error | Interpolation as exactly as possible on the programmed contour. |
High surface quality | Using splines for smoothing the vertex sequence, observing the resulting contour error. |
In free form surface programs, the short block lengths usually result in a large data quantity that must be processed. With an increased cycle time, the distance between the interpolation vertices is so large that several blocks will be skipped. Removing redundant blocks, at least partly, seems therefore to be logical. This is the task of data reduction. The saved computing time leads to a better data throughput and, in certain cases, to shorter processing times.