Methodology of off-line software compensation for errors in the machining process on the CNC machine tool
Zbigniew Lechniak , Andrzej Werner , Konstanty Skalski , Krzysztof Kędzior
AbstractOff-line software machining accuracy enhancement has been suggested based on the prediction of the machining error Δ→=[Δx, Δy, Δz]. It has been assumed that errors in the machine tool workspace can be analysed as a superposition of the components Δ→g, Δ→m, Δ→n where Δ→g results from the geometric surface description, Δ→m results from the limited machine tool stiffness and Δ→n results from the cutting tool deflection during machining. Geometric description error Δ→g=[Δxg, Δyg, Δzg] arises from the surface geometric modelling phase in the CAD system. The NURBS (Non-Uniform Rational B-Spline) technique has been selected as the most effective for the complex shape surface description, supported by the least square principle. Then the distances between the measuring points and the calculated points on the described surface patch have been determined and a function representing the inaccuracy of the surface description has been defined. The Δ→m=[Δxm, Δym, Δzm] error has been calculated based on periodic measurements of the machine tool positions while applying static forces to the spindle endpoint. The points in the factor have been selected according to principles of mathematical experiment planning. The polynomial regression-based relationships have been derived for Δ→m error description. The results have been validated using statistical correlation analysis. A similar approach has been adopted for the estimation of the cutting tool deflection error Δ→n=[Δxn, Δyn, Δzn]. The resulting Δx, Δy and Δz components have been introduced as compensation values adding up to the regular tool movements along the programmed tool path. A special postprocessing program has been developed for doing this job, herein called active task in order to differentiate it from standard postprocessing functions named as passive tasks.
|Journal series||Journal of Materials Processing Technology, ISSN 0924-0136|
|Keywords in English||CAD/CAM systems, Error compensation, Machining error, Postprocessing, Regression|
|Publication indicators||: 2006 = 0.615 (2) - 2007=1.133 (5)|
|Citation count*||54 (2015-12-01)|
* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.