Problems of forming stepped axles and shafts in a 3-roller skew rolling mill

The paper focuses on a new method for forming axisymmetric parts of considerable length in a CNC skew rolling mill. The laboratory rolling mill was used to conduct rolling tests for car axles (in scale 1:5). Although produced parts are free from internal defects such as fracture and shrinkage porosity, there occurs a local pile-up of the material leading to an increase in the workpiece diameter, as well as spiral grooves are formed, predominantly on conical surfaces. The impact of basic parameters of the skew rolling process on the formation of identified internal defects is assessed analytically and numerically. Experimental tests are performed to determine the effect of spiral grooves on the quality of final products, particularly forgings produced from skew rolled preforms.