# Construction of mould geometry error and surface morphology dynamic model for roller and centrifugal casting

There are two types of excitation on the rotor of rotating machinery, one is the excitation force acting on the rotor directly, the other is the motion of the foundation. Among the exciting forces acting directly on the rotor, the most common one is the unbalanced centrifugal force. In addition, there are the electromagnetic excitation track of the rotor in the motor and the fluid excitation of the rotor in the turbomachinery. In fact, the shape error and surface topography of two relatively moving contact surfaces will also cause vibration of the system. Due to the influence of processing accuracy and other factors, there is a certain shape error (roundness error) in the outer circle of mold and roller, and the surface of centrifugal casting mold and roller is not completely smooth, but has a certain surface roughness. Both surface shape error and surface roughness can affect the vibration of the mold to a certain extent.

In order to simplify the theoretical calculation, the following assumptions are made

(1) The relative motion between roller and mold is pure rolling;

(2) In order to determine the excitation caused by surface shape error and surface topography, it is necessary to calculate the coordinates of the actual contact point between the roller and the mold first, and the elastic deformation of the roller in contact with the mold is not considered when calculating the contact point between the roller and the mold;

(3) When studying the influence of surface shape error, it is assumed that the actual contour of each cross section of roller and mold is the same along the axis;

(4) When studying the effect of surface roughness, it is assumed that the actual surface morphology of each cross section of the roller and mold is the same along the axis.

Based on the vibration model of centrifugal casting machine, considering the surface shape error and surface roughness of roller and mold, the calculation model of excitation caused by surface shape error and surface roughness of roller and mold was established. Combined with the vibration model, the transfer matrix method was used to construct the mold vibration performance meter which can consider the geometric error and surface roughness of roller and mold Finally, the influence of geometric errors between roller and mold surface on the vibration performance of mold rotor is discussed through an example.

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