The S test piece is used to test the dynamic accuracy of multi-axis machine tools. The test piece is mainly composed of an "S"-shaped thin-walled edge with a wall thickness of 3~8mm and a rectangular base, as shown in the figure below.
For a long time, the accuracy of multi-axis machine tools has been mainly measured by the NAS 979 standard test piece in the United States. However, with the development of the aviation industry, a large number of complex thin-walled surfaces have appeared, making it possible to pass the NAS 979 standard test piece to achieve the corresponding machining accuracy. Machine tools are still unable to meet the processing requirements of high-precision curved surfaces. Therefore, the international standard proposal "S" test piece for machining centers proposed by AVIC Chengfei after years of experience was passed at the 74th international meeting of ISO/TC39/SC2.
The S test piece is an equal-thickness flange with an S-shaped twisted surface. The surface changes complexly. When using an end mill to process, the cutting edge of the tool is close to the flange surface, which requires that the tool axis must change back and forth at all times. The machine tool can It responds well to the command of the 5-axis back and forth change, and generates motion, so the S test piece can reflect the geometric accuracy, positioning accuracy, dynamic characteristics and reverse error of the machine tool in a concentrated manner.
