Manufacturing plastic parts with undercuts brings tough challenges for moulders. Undercuts are recessions or protrusions in a part and once the part is made, undercuts prevent the mold from sliding away. These features hinder the core’s direct removal and as a result, it becomes vital to use additional mould piece, such as an internal core or a side-core lifter, to make it in the desired shape.
Undercut designs in the moulding industry are primarily used to manufacture threaded parts, for example, snap-on products such as containers for cosmetics, screw-on bottle caps, and a wide verity of medical, consumer, and automotive products. For instance, if I discuss about the caps, after the cap is made, the threads of the core and the part’s threads are intermeshed which must be disengaged prior pulling out the core and therefore the cap can be easily removed from the mould.
Mould services today have adopted a verity of methods for moulding undercut parts, from as simple as unscrewing the part using hands or machining the undercuts in an additional process in order to get higher efficiency at lower costs. Further, in this blog, I have discussed the trending technological advancements which have brought better and more cost-effective methods of manufacturing threaded or undercut parts.
There are majorly two ways to make threaded parts…
Jumping Threads:
Unscrewing Mould Mechanism -
In general, a molder can simply strip the part or pull out the core by jumping the threads over each other in case the material is very flexible. If not, they often get the support of unscrewing mould services that can unscrew the part from the core.
Unscrewing moulds are one of the most complex injection moulds as they require significant technical knowledge to build and maintain. They are built in such a way that they function for years. However, most brands rely on unscrewing mould services for their requirements of bottle caps and other unscrewing openers and closures. Appointing such services for such projects is considered a great investment as the products can be made quickly and that also in high-volume.
Though unscrewing mould technology has considerably developed it still holds a considerable number of limitations. It requires timely maintenance for issues such as damaged racks, water and oil leaks, and broken rollers, etc. Issues related to the quality of parts such as ovality, scuffing, flash, and grease contamination can also appear.
Unscrewing plastic injection molds are primarily used to manufacture parts in high volume where threaded parts are strictly required for products like…
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Bottle caps
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Consumer goods
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Pharmaceutical Supplies
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Shampoo bottles
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Nuts and bolts
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Container lids
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Automotive parts
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Medical Supplies
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Cosmetics packaging
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Sprinkler heads, lawn & garden parts
While there are challenges, moulders always come up with technology that steals the show.
Unscrewing mould services are the biggest example and can be considered the best solution in this requirement category to achieve reliably, cost-saving, and reduced production time.
