# Calculation results of critical speed of mold for centrifugal casting machine

Through programming calculation, the first four critical speeds of centrifugal casting machine can be obtained. It can be seen that because the stiffness and damping of the support in the horizontal and vertical directions are not equal, the calculated critical speeds in the two directions are also different. The working speed of centrifugal casting machine (3000rmin-1) is below the first critical speed, which is about 75% of the first critical speed. It is safe to operate at the working speed.

From the previous calculation results, it can be seen that the change of roller support angle will cause the change of support stiffness and damping, and then the critical speed of rotor system will also be affected. Fig. 1 shows the influence of roller support angle on the critical speed of centrifugal casting machine: the critical speed in X direction increases with the increase of support angle α, and the critical speed in Y direction decreases with the increase of support angle α. This is that with the increase of N, the support stiffness in X direction increases, while the support stiffness in Y direction decreases.

Figure 2 shows the effect of support position on critical speed. It can be seen that the value of the first-order critical speed is the largest when the support span L3 = 2.8m, so it is reasonable to design the machine with the support span of 3M, which is conducive to the working speed as far away from the critical speed as possible, so as to ensure the smooth operation of the machine.

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