INJECTION MOLDING HELP
When make a plastic box. We alway see a hole like that. Maybe it is the gate area in the injection molding.
Please explain to me what this hole use for (in red sign). Can we make the box without this hole. I mean make the box with almost flat.
now no one can explain to me
thank you very much.
2 Answers
That is called a "cold slug well".
Between shots, the molten plastic at the tip of the nozzle of a 'direct gate' type part will freeze off a little tiny bit, and when the next shot occurs, this little "slug" of already hardened plastic will get captured here so it doesn't cause problems elsewhere in the part.
Google "cold slug well" for a more technical explanation, I'm kind of winging it with my description.
Parts that aren't directly gated (sub gated) also have cold slug wells, but they are put into the runner geometry instead of the part geometry.
Do you mean the slight indent in the bottom? This is because of direct injection. They created the indent to offset the sprew/gate to prevent an unwanted sink.
You could inject slower, with higher pressure, and that could help get rid of it, but being a box, might cause issues elsewhere. You could also not have the sprew go directly into the part, create a runner system and inject in a few spots. Again because of the shape of the box, not an ideal solution. Those are 2 ways off the top of my head how to solve the issue.
