500吨金属成型四柱液压机带动工作部件运动时，因运动件的质量较大，运动速度较高，则在到达行程终点时，会产生液压冲击，甚至使活塞与缸筒端盖之间产生机械碰撞。为防止这种现象的发生，在行程末端设置缓冲装置。现介绍几种从用的缓冲结构。
When the buffer column race at the piston end of the 500-ton metal forming four-column hydraulic press moves into the cylindrical oil chamber in the direction of the end cover, the oil enclosed between the column race and the end cover is squeezed out from the annular gap. Since the gap is very small, it acts as a throttling buffer. It is suitable for hydraulic system with little motion inertia and low motion speed.