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Collapsible core

ABIS Mold Technology Co.,Ltd Updated: Jul 22, 2016

It must be understood that the pin and the collapsible core                        sleeves float in the mold base and will be positioned in                        center by the retaining diameter. (Stripper ring,                        slides, or in the case of a side action the cavity and                        core inserts) This requires that the pin expands the                        fingers of the core while being contained to avoid                        unnecessary wear on the shut off of the core.

The                        molded part is required to be held centered during                        ejection, as the collapsible core is collapsed. This is                        so as not to hang the part up on one side of the core.                        This could be accomplished through the use of a part                        detail or molding part of the outside diameter on the                        stripper ring, etc. On side actions, the part needs to                        be held in place (centered) as the core is removed from                        the molding area. The mold function will dictate the                        most advantageous design.                                                                          

As                        with all mechanism with moving parts, venting must be                        away from the core. Preferably along the parting line,                        vent to the outside of the mold. In some cases, when the                        core is a side action, it may be necessary to vent along                        the outside diameter of the core. The fingers of the                        core have clearances of +0.0000/-0.0002�, this                        requires that the core remain clean of gassing and                        residue produced in the molding process.                                                  

The                        pin diameter has similar clearances to the inside                        diameter of the fingers of the core. As was stated                        earlier, the pin and the core are centered by these                        diameters fitting within the containment ring (stripper                        ring, side actions, etc.) You should never vent along                        the pin.                                                  

Cleanliness                        is essential to maintaining the endurance of the core.                        Mattering on the material being molded and the                        effectiveness of the venting, a schedule for cleaning                        the cores needs to be established. If the fingers become                        too dirty or gummed up with residue from the molding                        process, they will not close properly, which will cause                        damage to the core. It is better to clean the cores more                        often than to allow the dirt to build up to an                        unacceptable level. The mold design should incorporate                        an easy way for removing the cores for cleaning.                                                                          

As                        with all injection molding, having the mold close on a                        part that did not eject properly will cause damage. When                        the part is molded and hardens, the part shrinks smaller                        than the cavity. This situation will cause breakage to                        the core, since it will not be able to open the fingers                        into the molded part. There are many safe guards which                        can be installed to avoid this situation.

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