Roller Trace Design in Multi-Pass Conventional Spinning Based on Cylindrical Part

 Conventional spinning is a kind of ancient revolving process which controls the product’s shape by roller trace design. It is also widely used in civil, military, automobile, aerospace and other fields. Unlike the power spinning process, the roller trace used in conventional spinning is complex. Both thickness uniformity and crack defects are affected by it. However, roller trace design is still based on experience without a solid theoretical basis. This paper established four different roller trace curves: involute curve, circular curve, Bezier curve and conchoid. Experiments using superalloy GH3030 were conducted in conjunction with a multi-pass conventional spinning simulation model. Blank thickness variations, mandrel and roller forces of different roller traces in the first pass are analyzed and assessed through the verification experiments. The results suggest that for roller trace design, setting the starting point of the roller trace at the bending zone of the blank and using the clockwise or counterclockwise rotation of the original curve trace and adding the pass pitch can greatly simplify the roller trace design process. By using this method, it can be easily programming in NC codes and the designers may apply more complex curve traces in conventional spinning. The curve trace parameters play a key role on the product thickness uniformity. Comparing several roller traces, the conchoid roller trace proposed in this paper has a good forming effect and can be applied in industrial production. The tool forces of mandrel are much bigger than the roller. For both mandrel and roller, Z (axial) force is much bigger than the X (radial) force, while the Y (tangential) force can be ignored compared with the other two forces. The tool forces of different roller traces have big differences especially on the Z force of mandrel. So the axial force of mandrel is a very important factor in the design of tool load capability. The wall thickness distribution of the product is in annular distribution. And the distribution of Bezier and conchoid roller traces is more uniform than with other traces. With the effect of the moving roller, there is metal accumulation at the edge of the flange, and the thickness of the zone above flange (zone 2) is very thin. In the multi-pass cold conventional spinning of superalloy, cracks are easily generated in zone 2. Faster roller feed velocity and proper roller traces can reduce the thinning in zone 2 which may avoid the cracks.