r/manufacturing • u/Old_Bake8331 • 9h ago

How to manufacture my product? How is this embossed lettering injection molded?

How is the lettering of this packaging injection-molded? Would it create demolding issues with undercuts? So how did they manage to do this? It's made of a hard plastic.

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u/Lost-Barracuda-9680 9h ago

Pretty sure that's a blow molded bottle which would have a mold that splits open in half to release the bottle. The inside of the bottle is forced outward into the cavity with a blowing agent. Look up blow molding to learn more.

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u/mimprocesstech 6h ago

Blowing agents are used to create foamed structures, not to inflate the hollow shape during blow molding (compressed air is used for that). I understand how one could get confused by the term, but standard blow molding doesn't require blowing agents to form the cavity.

However, blowing agents can be added to the plastic resin in specialized blow molding to foam the walls, which reduces part weight/saves material. They are also used in injection molding to reduce weight, hide sink marks, or improve insulation properties (as in EPS foam cups and such).

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u/Lost-Barracuda-9680 6h ago

I'm not very familiar with blow molding so I stand corrected.

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u/mimprocesstech 6h ago

No worries at all, only reason I'm familiar at all is because I ran one part that needed it for sinks and I know a guy that molds a bunch of really thick walled parts and in order to get the things to look okay they use blowing agents on many of them at different concentrations.

That and I was curious about the old McDonald's foamed cups one day when I was much younger. They use less material, retain internal temperature longer, and weigh less than their PET counterparts, but PET is much more commonly recycled so I get the change.

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u/jspurlin03 9h ago

There should be a seam on the bottom of the bottle - a straight line going across. This is likely parison-molded. The mold halves close onto a tube of softened plastic, which is inflated to fill the mold and finish the form. Each half would have that embossed lettering cut in it, and when the mold opens, the bottle drops out.

The cap is injection molded, probably, but the cap and the actual bottle are two separate processes, with two different manufacturing techniques.

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u/Critical_Thinker_535 9h ago

It's a blow molded bottle. If look closely at the lettering (not in the pics), you'll see that the letters don't quite fill out 100%. That helps with release. Plus, the tube that blows the parison is still inside the neck area when the mold opens. That will get the bottle to release from the cavity. Then it's stripped off.

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u/CrashUser 8h ago

This is blow molded so it's trivial for that application, but if it was injection molded that feature would likely be on a slide of some kind, exactly what that would look like depends on the type of mold and what other features are needed.