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Molds

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This topic contains 1 reply, has 2 voices, and was last updated by  Nick 1 year ago.

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Butte Metz btmetz

Molds

23/10/2017 at 04:03

I previously built a different style injection mold machine based on the portable drill press adapter for hand drills.

It worked OK but the capacity of it was quite low and it was a bit lacking in leverage to get a good shot into the mold beyond an ounce.

However, One thing I got some experience at was making molds.

I came up with a couple different types of mold making techniques based on other peoples ideas I saw online.

One thing I tried and had good success with was casting a mold from epoxy resin. I didn’t have JB weld, but high grade marine epoxy worked just as well and is available locally here in the Philippines in up to one gallon pail sizes.

I tried several different methods.

One was to cut a block of pine in my router to hold the epoxy with registration pins.

It worked OK but it takes a lot of care to make work right. I had to add extra epoxy above the level of the wood block and then machine flat in the CNC router. This is because I was unable to get a smooth flat surface to mate the two mold halves together.

I also had to use a LOT of mold release spray.

In addition, a couple times, I did not get a good mold because I just didn’t cast it right.

Mold making is truly an art form.

Second type of mold I tried is 3D printing a sort of positive mold for RTV silicone.

I printed the entire mold block half as a negative then cast it in silicone. I even printed the registration tabs to align it.

This worked very good for resin casting, however I only had a soft RTV which makes it unsuitable to use for injection mold.

However I think if I was to use a decent fiberglass resin, cast into a printed mold master It should work pretty good.

there are of course lots of issues associated with this which are beyond the scope of this post. Namely compensation for resin shrinkage, mold release, mold draft, sprue, runners, venting, flashing, etc.

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In reply to: Molds

helper
06/11/2018 at 01:11
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@btmetz have you had any more experience/success with making fiberglass molds? I just thought of using it to make large rectangular sheet molds that I’d then press afterwards. Seems like it would be a lot cheaper than sheet metal. Not sure about temperature resistance, brittleness etc…

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