Research On Reconstruction And Optimization Of Five-Axis Cnc Machine Tools Accuracy Test Specimen’s Type Surface

"S" shaped test piece is a new standard specimen designed for detecting the dynamic accuracy of multi-axis machine tools. By machining "S" shaped piece and measuring its surface errors, not only geometric errors like machine positioning errors and each axis’ reverse errors can be detected, but also the multi-axis machine tools’ comprehensive evaluation precision, servo response performance, interpolation precision and dynamic stiffness of machine performance. Now the "S" shaped test piece has been applied importantly on multi-axis machine tools, but according to ISO standard proposed universal, simplified and engineering requirements, there are still some deficiencies. Firstly, the current "S" shaped test piece?s upper and lower baselines are defined by each 50 data points, which are too complex and inconvenient to promote. Secondly, the process of generating model needs to calculate the control points by data points, as the inverse calculation algorithm is not unique, the resulting model isn?t unique too. Finally, the existing related papers didn’t give a clear definition on the generation methods of the "S" shaped test piece’s type surface. Therefore, conducting research on reconstruction and optimization of its type surface has important theoretical and practical value. Starting from the definition of the "S" test piece, the main research contents are follows:1. Based on Cubic uniform B-spline curve interpolation theory, this paper analyzed the "S" specimen baseline generating method and its shortcomings, re-interpolated and redefined the upper and lower baseline. By reducing and adjusting the control points, the baseline was simplified and reconstructed, retained the various characteristics of the original baseline as more as possible.2. The "S" shaped test piece surface generation principle was analyzed based on the theory of ruled surface interpolation. Two "S" shaped test piece surfaces were generated by using different parameters and their differences were analyzed and compared. By comparison, the method of generating "S" shaped test piece surface was determined, which achieved the simplification and Reconstruction of "S" shaped test piece, provided a theoretical support for the uniqueness of "S" shaped test piece.3. Based on differential geometry theory, some typical geometric characteristics between the former and new "S" shaped test piece were analyzed comparatively, Such as the curvature of the upper and lower baseline, surface continuity, the opening and closing angle and so on. The analysis results show that the distribution of typical geometric characteristics between the former and new "S" shaped test piece is consistent with the overall but some subtle differences in the local area.4. UG software is applied to program the “S” shaped test piece. Then Based on CNC machining theory, an analysis and comparison on processing characteristics of different "S" shaped test piece was made, likes the ideal speed, acceleration, singular point and other features, which proved the feasibility of the reconstructed "S" shaped test piece.