As the crankshaft rotates, the crankpin swings in a circle around the shaft. 随着曲轴的转动，曲柄销绕主轴作圆周摆动。
The former causes forced vibration at the circular frequency of the crank shaft and the latter causes transient vibration at the natural frequency of the press. 惯性力激发的振动是以曲轴转速为频率的强迫振动，加工力激发的是以压机固有频率为频率的过渡振动。
