Volumetric Compensation for Machine Tools

In recent years there has been a rapid development in machine tools but little has been done by the manufacturers to combat the geometric alignment errors and thermal distortion of the machine structure which has limited the commensurate increase in accuracy.

Volumetric Compensation Software has been designed to correct errors in the path of the cutting tools before they occur and improve the overall accuracy of the machined product.

A local company, utilising Osai 80 controller pound that there typical accuracies increased from 78 to 16μm with a reduction in cycle time of 15% and a 30% reduction in scrap. Additionally the machines were able to run faster and for longer periods without losing accuracy.

The system can be used on small multi axis machines through to larger long bed CNCs.

The software is also compatible with other types of controller.

The Volumetric Compensation Software runs as a utility in the background of a CNC system and improves the accuracy of a machine tool under CNC control – giving a corresponding improvement in component quality.

VCS makes extremely small and rapid corrections to the movement of the machine axes as they execute their programmed moves.  Using correction data from previously compiled tables in the CNC system, errors are cancelled dynamically, before they affect the work piece.

In metal-cutting machines with 3 axes or more the  VCS reduces machining error in small, high accuracy components, as well as larger machined components.  A version for 5 axis machines is in development, as are possible lathe and CMM applications.

In the normal machine calibration procedure correction is made for errors in axis positioning – which is only one factor governing volumetric accuracy.  VCS addresses additional factors.  For example, it works effectively to cancel both geometric and thermal errors (i.e. errors caused by thermal expansion and contraction of the machine structure).

The equipment can traditionally be calibrated by spending massive time and effort on geometrical alignments, only to tweak their machines and programmes even further in a quest for accuracy.  This intense and time consuming work increases downtime, without necessarily reducing scrap rate.

There are no drawbacks in the use of VCS as long as the machine has a compatible control system and is mechanically sound with good repeatability.  For older, incompatible machines, VCS can run on a supplementary PC interfaced between the machine and its controller.  VCS is completely transparent, requiring no operator input.

Copyright 2006 - Precision Technologies CIC - Designed by Interactive Solutions