As the pressure builds up at the die entrance due to the movement of the material, the rotating screw begins to move backward under this pressure to a predetermined distance (volume of material).

• 由于原料的运动拉模的入口喇叭处（到模具的主浇道的入口处）压力增大，旋转螺丝钉（螺杆）在这种压力下（一边旋转一边）向后移动到预定的距离（材料量）。