Surging refers to oscillation specific to a coil spring. When an external force having a frequency component close to the spring's natural frequency acts upon the spring, an oscillation phenomenon called surging occurs owing to the mass of the spring. When high-speed compression or tensile forces are applied to a coil spring by a cam, surging occurs by the spring itself resonating with the high-frequency components of the cam's head-discharge curve.

(1)What is surging

	-	When a coil spring absorbs shock, the coil wire undergoes torsion, which is transmitted as a shock wave. This shockwave is called a surge wave.
	-	The amount of time (T) in which this surge wave moves along the spring wire and travels back is called surge time. The surge time and speed can be calculated using the following formula:
	-	When a coil spring is subject to forced oscillation, the resonance phenomenon surging occurs if the cycle corresponds to the surge time T or becomes the half or one third of the surge time T.

(2)How to prevent surging

(1)Changing the cam shape

Change the cam design to minimize the amplitude of vibration generating from the spring's natural frequency and cam's rotation speed in the resonant frequency range.

(2)Adopting a variable pitch spring

Variable pitch springs have the characteristic of a change in deflection altering their natural frequency. Surging can be avoided by adopting a variable pitch spring that does not cause resonance.