Mold operation sequence

In certain processes (such as rubber tire manufacture and plastic injection molding operations), it is common for a valve sequencing system to first provide hot steam followed by cold cooling water and thus for cross-contamination to occur. The result may be the stripping of passivated cooling system surfaces by steam and for the condensate to be infiltrated by cooling water. 

Mold (Mz) Different from the previous three operations, this operator is not a symmetry transformation. The upper layer is molded down to generate the lower sheet. Figure 7.7 shows an example of this operation, in which the single sheet is used to generate the double sheet building unit for the structure of ZSM-5. ZSM-5 structure can be produced from this sheet by a combined MzIMzI operator sequence. 

Figure 7.9 Sequence of mold operations. (a) Plastics material is injected into the closed mold. The mold remains closed while the molding cools, b) The mold opens, leaving the molding attached by shrinkage to the core, (c) The ejector plate is moved forward, causing ejector pins and stripper bars to push the molding off the core.

Blow molding is a process for converting thermoplastics into hollow objects. Like injection molding, the process is discontinuous or batchwise in nature, involving a sequence of operations that culminates in the production of a molding. This sequence or cycle is repeated automatically or semi-automatically to produce a stream of molded parts. 

Hand molds are used primarily for experimental runs, for small production items, or for molding articles which, because of complexity of shape, require dismantling of mold sections to release them. Semiautomatic molds consist of units mounted firmly on the top and bottom platens of the press. The operation of the press closes and opens the mold and actuates the ejector system for removal of the molded article. However, an operator must load the molding material, actuate press controls for the molding sequence, and remove the ejected piece from the mold. This method is widely used. 

During the ejection operation the controls coordinate the sequence of movements performed by the clamping unit and ejector. The ejectors cannot be allowed to move too quickly because this might cause them to pierce the molding. The movement opening the mold in the parting plane should also start slowly to avoid damaging the molded article. 

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