Question: We perform annual laser calibration on all of our EDM machines. Does my Xermac CNC machine support cross-axis or volumetric compensation?
Answer: Yes, depending on the age of the machine. Xermac CNC machines use a Delta Tau Data Systems PMAC motion controller. Axis calibration data is stored on the PMAC board. Volumetric compensation is a relatively new industry term that is defined somewhat differently by different manufacturers. Essentially it implies that anywhere in the XYZ work cube, compensation will be applied to all axes so that position is accurate.
A simple example of this can be found on any of the Xermac ST machines. These stationary tank machines have the head attached to the Y-axis. As the Y-axis extends outward, it will dip down a small amount just under its own weight. Volumetric compensation will apply compensation to the Z-axis to correct for error in the linear scale. It will also add correction in the Z for the extension of the Y-axis, correcting for the sag in Y-axis when fully extended. Add to that a compensation for the Y axis as a function of X-axis saddle position and you have compensation everywhere within 3D space.
The very early Xermac CNC machines (Circa 1989) did not support the idea of cross-axis compensation. But by July of 93, with Delta Tau firmware V1.14, the system fully supported cross-axis compensation. Delta Tau called it a 2D leadscrew compensation table. By connecting the Y-axis to the X-axis saddle and connecting the Z-axis to the Y-axis arm, volumetric compensation can be achieved.
EDM Zap offers calibration services for your Xermac equipment.