Compensation for machining defects due to spindle dilatation

Defects are a common occurrence in industry when it comes to prolonged machining tasks (machining moulds, series of work-pieces, etc.). The relatively long machining time is generally what gives significant value added to the work-piece. We therefore need to avoid having to produce test work-pieces as much as possible [NC Machines, Hermes Paris (1997)]. This article considers dispersions introduced by dilatation of the spindle during machining on NC machine tools. Such dispersions are obviously prejudicial to obtaining accurate dimensions along the Z-axis of the machine. Firstly, we introduce the context of the study and the problem we had to confront. Secondly, the experimental study enabled us to highlight those parameters having an influence and quantify defects. By expressing dilatation and relaxation in the form of an equation, we were then able to calculate defects at a given instant. This enabled us to generate an algorithm for processing of the N.C. program so we could correct errors by compensating for defects during machining. We completed the study by machining a series of work-pieces using the programme integrating compensation for dilatation so as to validate the approach.