Volumetric Compensation Through The Machine Controller

Compensation is a cost effective method of correcting for machine tool systematic errors. Although controller manufacturers are providing increasingly more sophisticated compensation, they do not include for all geometric sources of error for the variety of 3- and 5-axis configurations that exist today. A small number of comprehensive PC-based compensation systems exist, requiring hardware modifications and interface electronics to interact with the position control loop, which can be expensive and difficult to implement. This paper describes a general purpose error compensation system that is located and runs inside the machine controller. The system has been designed to run on a modern open architecture Computer Numerical Controller, namely an Osai UK series 10 controller. One of the facilities within this controller is a DOS Real Time Interface, which allows a user to develop custom applications that can run and communicate with various parts of the NC system in real time. Compensation software, based on a 5-axis geometric error compensation system produced at the University of Huddersfield, has been developed to run in the DOS real time environment. The system has been applied to three machine tools and the volumetric accuracy significantly improved. Requiring only a simple software installation, the system is also shown to be inexpensive, simple and fast to implement.

This paper describes a general purpose error compensation system that is located and runs inside the machine controller. The system has been designed to run on a modem open architecture Computer Numerical Controller, namely an Osai UK series 10 controller. One of the facilities within this controller is a DOS Real Time Interface, which allows a user to develop custom applications that can run and communicate with various parts of the NC system in real time. Compensation software, based on a 5-axis geometric error compensation system produced at the University of Huddersfield, has been developed to run in the DOS real time environment. 

The system has been applied to three machine tools and the volumetric accuracy significantly improved. Requiring only a simple software installation, the system is also shown to be inexpensive, simple and fast to implement.