What are they?
An internal thread form is basically an undercut that does not allow free ejection from the mold. Low production prototype molds can be unscrewed by hand, but most molding is done automatically. Parts that have a suitable thread form and low modulus of elasticity, can be stripped off the threaded cores, because the undercut shape and flexibility allows this to happen. A collapsible threaded core can be used to mold internal thread forms and freely eject small to medium size parts. The majority of all thread forms (especially medium to large) are unscrewed before ejection takes place.
Why is Molding Internal Threads Important?
There are many different designs and methods for unscrewing style molds. How complicated the design becomes is dependent upon:
- The thread form shape, number of cavities, and mold life.
- The core and drive design used.
- The power required.
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