Large Injection Mold

Hi team, I am looking to make a large injection mold (approx 300mm x 20mm x 20mm box and am looking for some advice on how to adapt the injection mold to fit.

I was considering a double injection i.e. 2 barrels, 1 hopper to avoid cooling of the plastic when it enters the mold. Has anyone had any experience with this technique?


On the finished part, where would your preferred sprue be? The best place in my mind would be in the middle of a 300x20mm side. I don’t think that there would be a need for a second nozzle with a block this size. If you’re worried about the plastic cooling too quickly, I would suggest heating the mold a bit before injection.

The double injection idea intrigues me, so I’ll be working on some preliminary ideas on this for a little while. My initial idea would be to keep the two nozzles as isolated systems, only linked by the handle. My thought on nozzle-to-mold connections would be flanges, but I’m not sure how well this would work out in practice. especially looking at fabrication costs these days.

I’ll post an update when I finish modeling one.

Hello Edward,
Molding such a big piece would be a challange on hand molding. I would suggest using the compression machine. See the link .

But to answer the question, here are a few calculations (Assuming all in SI units).
Part Size = 300mm x 20mm x 20mm
Thickness = 3mm
Part Volume = 63 mm³
Part weight (PE) = **59 gm

**That is alot of material to be pushed through a hand molding. and not to forget the amount of clamping force required.

If you want to go for the two gate system , woul would end up with a weld line in between the part. That would be a weak spot.


What is it exactly you you are trying to make?

Just “the box” or is this just the box size of the mold?


I’m not an expert, but I do get a lot of information from the forum, so if I knew what you are looking for, I (or anyone watching) could better point you in the right direction.


An image or two might be very informative.

Are you in Tanzania?