If I have to make an injection mold (for resin based raw material) using 3D printing, what raw material should I choose – PLA, ABS, HIPS etc.
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$\begingroup$ My gut instinct is that it doesn't matter what material you choose, and that any 3D printable material would be equally unsuitable for this. $\endgroup$– Tom van der ZandenCommented May 10, 2018 at 11:54
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$\begingroup$ @arvind-gupta None, injection mold is based on Metal Dies. Some polycarbonates may help but they aren't printables. $\endgroup$– Fernando BaltazarCommented May 11, 2018 at 17:34
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2 Answers
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P20 mold steel is one standard. Hardened parts are required for long life, depending on the service and material (some materials are quite abrasive).
You can get a small number of relatively poor quality shots out of epoxy if it is properly supported by a metal box. Your best bet if you want to include 3D printing in the equation is probably to use epoxy or lost plastic casting from a 3D-printed master. Aside from the requirements of core and cavity with sufficient strength, there are requirements for vents, cooling tubes (bubblers and such like) ejector pins and slides that complicate most real molds. Productivity demands a high heat transfer rate, for very small quantities of expensive parts, thermal design may be less important.
Temperatures and pressures are very high in injection injection molding- high enough to melt the materials you mention, and the pressures are in the 10K PSI range, so a 4" x 4" projected cavity will have a pressure in the 80 ton region.
If you have sintered and filled metal 3D parts they may be suitable, but from the prices I've seen you'd be better off to use conventional machining. Finish is also very important if you want the part to come out of the mold, with hours of semi-manual polishing not uncommon. If you don't have fine surface finish you will need extreme draft angles.
The requirements can be considerably relaxed if you are molding soft parts such as the PVC or TPE overmolds on cables. The pressure is less and the finish less important because the plastic is soft, but the temperatures are still quite high. This is sort of a sub-category of injection molding and specialized machines are used.
answered May 11, 2018 at 16:50
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Answers above are correct that no plastic mold will work for actual injection molding. Injection molding by definition requires pressure, pressure that would explode a plastic mold. If on the other hand you really just want to print a mold that you can pour epoxy into to get a shape, then you just need to consider a couple factors.
- How hot things are going to get since epoxy is exothermic and the thicker the cross section the hotter it'll get.
- How to keep the epoxy from sticking.
For issue 1 I would pick the material that's available to you with the highest glass transition temperature so it doesn't melt or deform.
For issue 2 I would use mold release compound before you pour in the epoxy and probably pick the plastic with the lowest surface energy.