General plastic parts from the mold cavity, both the original single release, such as the top block, pipe jacking, the top rod or roof, or the combination of several demoulding demoulding of the original, the release action is a complete. But sometimes, with a top is not smooth demolding, which use two stripping mechanism.
  1.the two time ejection purposes. In an ejector action is completed, the plastic is still difficult to release, or not free to fall down, the need for a two time ejection. To ensure the quality of plastic parts, plastic parts ejection resistance of some large, an ejection of some excessive local stress of the plastic parts, so that the plastic deformation, two out of the top can disperse the force, the deformation of plastic parts is reduced, so as to ensure the quality of plastic parts.
  2.two time ejection requirements. There must be two or two groups of ejector stroke has certain difference of ejection parts early stop motion. The three top if not act at the same time, stroke larger parts lag motion.
  3.two time ejection characteristics. Release reliable, for the deep cavity plastic parts, an ejector often difficult to release, while the two ejector can ensure the smooth demoulding. Do not damage the plastic parts, ejector effect is good. Even a top plastic parts mold, if the two time ejection will get more reliable results. More complex structure, the two push out by two groups of elements to release purposes, so structure is more complex. Installation of high precision, convenient for two groups of ejection mechanism work well, we must make the coordination, the sequence and fitting precision requirements higher, otherwise it is not up to good effect. Two secondary ejection mechanism classification. The two top institutions of its structural form, can be classified as follows. Single ejector plate two stripping mechanism. Its characteristic is the only one set of ejection device, but you need to complete the two top action is a kind of widely used structure form. Double plate two stripping mechanism, which is characterized by the use of two sets of ejection device has action to complete the two release. Pneumatic and hydraulic two stripping mechanism. It adopts pneumatic or hydraulic to complete two stripping