It is assumed that the geometric errors of the left roller, the right roller and the outer circle of the mold vary according to the law that can be expressed by a certain function

As shown in Fig. 1, when considering the errors of the supports at both ends, it is assumed that the surface geometric errors of the rollers and the mold at the supports at both ends are the same and change synchronously according to the same rule. Through programming calculation, the amplitude frequency response of the cast rotor in X direction can be obtained when the roller speed is in the range of 0-2000 r.min (- 1), as shown in Fig. 2.

It can be seen from Fig. 2 that when the geometric errors of the left and right rollers and the mold cylindrical shape change regularly according to the assumed function, the maximum amplitude of the rotor appears multiple local peaks when the driving roller speed is in the range of 0-2000 r.min (- 1). When considering the geometric error of the roller and the mold table at both ends, there are six peaks, and the corresponding roller speeds are about 250r. Min (- 1), 350r. Min (- 1), 600r. Min (- 1), 1020r. Min (- 1), 1150r. Min (- 1) And 1450 r.min (- 1). If only considering the geometric error between the roller and the mold surface at one end, there are seven peaks, of which six corresponding roller speeds are the same as those considering the two end error, and the other corresponding roller speed is about 1375 r.min (- 1). When considering the geometric error of the supports at both ends, the maximum amplitude occurs at the roller speed of 1450 r.min (- 1), reaching 0.21 mm, which is the same order of magnitude as the maximum amplitude caused by the unbalanced force in the figure. This shows that the geometric error of the roller and the mold surface has an important influence on the vibration of the mold rotor.

As shown in Fig. 3, when ω 1 = 2000r / min, the rotor shape of the mold is caused by the geometric error between the roller and the outer circle of the mold. It can be seen from the figure that when the geometric errors of the roller and the mold surface at two supporting positions are considered at the same time, because the geometric errors of the two supporting positions are equal, the resulting excitation force is also equal, so the shape of the mold rotor is symmetrical about the center of the mold, and the maximum amplitude is at the end of the mold, with the maximum amplitude of 4.96 μ M. When only considering the geometric error between the roller and the mold surface at one supporting position, the shape of the mold rotor is asymmetric, and the maximum amplitude is 4.78 μ m at the end of the mold, which is much larger than the vibration caused by unbalanced centrifugal force.