The VTLAXS Command [M]

The VTLAXS command defines angular tolerances that can be used by the post-processor to eliminate or reduce rotary motions that have an insignificant effect on the tool-to-part orientation. The following VTLAXS command functions are available:

Rotary Axis Tolerance

Large rotations and oscillations of a rotary axis can occur as that rotary axis approaches a “singular” orientation. This happens when the tool axis is parallel or is nearly parallel to the axis of rotation of a rotary axis. These rotations, although large, have very little effect on the tool-to-part orientation. The following command defines an angular tolerance to help eliminate unnecessary rotation:

\textbf{VTLAXS / ANGLE}, \begin{pmatrix}\begin{array}{l} \mathit{toler} \\ \textbf{ON} \\ \textbf{OFF} \end{array}\end{pmatrix}

The toler value specifies the angular tolerance in degrees, measured as a conical half angle from each rotary axis of revolution. When the tool axis falls within this cone, it will be adjusted (i.e., snapped) parallel to the rotary axis of revolution and the corresponding rotary axis will be marked as singular and no longer rotated. The choice of appropriate tolerance is a function of the CAM system vector word size (in the CL file) and manufacturing tolerances. For example, if ijk vector data is output to 4 decimal places in the CL file, then a tolerance of 0.006 degrees (i.e., arc tangent of 0.0001) is necessary to ignore round-off errors that may affect the rotary axis position. Generally the error is not due to the ijk word size, but is instead due to internal manufacturing tolerances used by the CAM system. In this case the tolerance may have to be set experimentally to produce the least amount of unnecessary singular rotation while still respecting part angular tolerances. The accumulated travel summary at the end of the GENER listing can give an indication of the effectiveness of various tolerance settings.

OFF inhibits the angular tolerance feature. ON re-enables the last specified tolerance.

Tool Vector Tolerance

Very small changes in tool axis vector can cause unwanted movement of the rotary axes. The following command defines a vectorial tolerance to help eliminate unnecessary rotation caused by slight changes in tool vector orientation:

\textbf{VTLAXS / TLVEC}, \begin{pmatrix}\begin{array}{l} \mathit{toler} \\ \textbf{ON} \\ \textbf{OFF} \end{array}\end{pmatrix}

The toler value specifies a vectorial tolerance in degrees. When this tolerance is active, the rotary axes will not move provided that the compounded change in tool axis orientation is smaller than the specified vectorial tolerance value.

OFF inhibits the vectorial tolerance feature. ON re-enables the last specified tolerance.