DIY HDPE mold for making rings

[ttallos]

I want to make rings from black HDPE. I need to know if this idea it is possible. My HDPE ring looks like a large washer 18" wide outside diameter with the hole in the middle 6 1/2" wide and the whole ring being 3/4" thick. My thinking was I could make an aluminim mold with an adjustable lid that can be tightened down to 3/4" from 1 1/2". I place HDPE pellets into the mold then heat the mold itself to 350 degrees and begin to clamp down on the lid till the HDPE oozes out the small holes on top of the lid. Can this idea work? If so, I have to make another ring 22" wide outside diameter with the hole in the middle 8 1/2" wide and the whole ring being 3/4" thick as well.

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[cordvision]

I don't see this working at all. You should look at resin casting instead, or mill, waterjet cut the rings from a solid HDPE sheet.

[ttallos]

I bought deep dish pizza pans with a 2" lip 18" as a form, cut up 5 gallon buckets and stuck them in an oven at 350 after adding till the desired thickness I baked it for 1 hour and presto the whole thing melts nicely. After it shrunk and cooled for around 15-30 minutes I clamped it with a 5/8" board on top and bottom with 8 C clamps and let it cool till morning! I am going to set up a stove outside to experiment with mixing colors next time. If I could make 4-5 at a time it may be worth it. By the way I still have to plane and mill it it may be better to just get the cut rings from China. Tanks for offering an alternative idea I will check it out.

[cordvision]

I'm curious how this worked out. Any chance you have a picture to post? Are you getting an acceptable surface finish and no air bubbles etc? How's the strength of the ring itself since the HDPE is not molded under large pressure? What you are doing sounds almost similar to compression molding, but this is usually done with several tones of clamping force.

[ttallos]

Here are 3 pictures the ring is made from 5 gallon buckets cut up the cost was $12 I want to try using recycled buckets some day. The blue side with small bubbles is the bottom I will mill this out. The smooth black is the top side it will be milled just lightly. All the milling will be done with a bosh router by hand using jigs (a sled for planing and circle cutting jigs for the rest). The next one of these rings I make I want to try HDPE/FDA pellets. The bubbles will be milled down and sit upside down in a tank so it doesn't matter if there are any imperfections. Let me know what you think and if there are any ways to do this that come to your mind.

[Rabs2014]

It sounds like you are trying to do a simplified compression moulding process, which is often used to make rubber parts like wellington boots (gumboots) and rubber bungs and grommets. Googling compression moulding might turn up some useful information.