Fixture Locators Error Compensation by Modifying NC Codes in Three Axis Machining

Fixture locators’ height error cause incorrect positioning of the workpiece in the fixture and inaccuracy in machined surfaces. This paper presents a new method for compensating the fixture locators’ height error effect on workpiece machined surfaces. In this method, the planes of workpiece Actual Coordinate System (ACS) are mathematically modelled in the workpiece Theoretical Coordinate System (TCS). Using the model, required Homogenous Transformation Matrix (HTM) for coinciding ACS with TCS and modifying machining toolpath for compensating the errors is generated. The presented model is used to develop a postprocessing fixture Locator Error Compensation (LEC) module, which can modify NC machining codes to eliminate the effect of fixture locators’ height error on the workpiece machined surfaces. For verifying the method, machining simulations using NX and VERICUT software have been performed. The results show that the method eliminates the effect of fixture locators’ height error on the workpiece machined surfaces considerably.

Keywords:

Error compensation , Fixture locator height error , Homogenous Transformation Matrix , Three axis CNC machining