injection molding side actions: in depth

If you don’t know what a side action is, that cool. Check out these two brief videos on how side actions work. You also would do well to check out what Protomold (parent company of First Cut) has to say about side actions here and here.
 

Recently I had occasion to dive into mold-making techniques in order to resolve a conflict with a molder about where the parting line (where two parts of a mold meet) on a side action would be. It had been a bit since I had thought deeply about cam/pin interactions vs. straight pull side actions, so I dug through some old notes and found  written by Mark Scanlan of PFA.

It’s written from the perspective of a tool-maker so it occasionally wanders into the esoteric (want to know what happens when pressure plastically deflects the steel core during the injection cycle?), but at 8 pages between the two PDFs, it’s a quick read.

And valuable. If you are using a low-rent molder they might push you towards a cam/pin action which, while it is sometimes the best call, has less flexibility with witness lines than a straight pull.

If you don’t follow that last sentence, don’t worry. Mark explains it better. Not only that, he ends with recommendations like this:

Use compression fit/zero movement cylinder only (requires full hydraulic pressure during injection) or the modular core compression side-action systems previously discussed (where hydraulics are not needed during injection) for:

• All high quality part requirements.

• Core areas greater than 0.5 square inches.

• Long stroke cores.

• Equal exposed core face to body areas.

• Moderate to small slide cross sections.

• Slide lengths greater than 2″.

• Off parting line cores.

• Cores angled to the parting line.

• Core movement prior to mold opening.

Nice.

To read the articles in their entirety, hit the jump.

Related posts:

  1. how side actions work: two brief videos
  2. injection molding plastic part design guide (GE)
  3. Reaction Injection Molding (RIM) design guide

Tagged as: cam, Injection Molding, plastics, product design, side action

Article by chris loughnane

Chris is Design Engineer + Sustainability Advocate at a Boston area design consultancy and has written 150 sweet posts for the Product Development Notebook.

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