High density polyethylene (HDPE) resins from LyondellBasell are thermoplastics made from the polymerization of ethylene in gas phase, slurry or solution reactors. Polymerization takes place under low-pressure conditions with the support of catalysts. HDPE is characterized by a linear polymer chain with few branches, and contains smaller amounts of comonomers such as butene, hexene or octene. HDPE grades are used in a variety of processing techniques such as extrusion, extrusion blow molding, injection and rotational molding. HDPE forms the largest product family in polyethylene, and is used in numerous customer applications such as pipe, plastic fuel tanks, industrial packagings, bottles, healthcare articles, containers, toys, films, tapes and fibers.

This can save you a boatload of cash if you don’t need parts that are extra rigid or fiber reinforced. It’s urethane so it’s reasonably safe to work with also.

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Home Injection Molding: This Instructable explains how to make real injection molded plastic parts using a simple hand-operated machine. I realize most of you reading this don't have one of these machines, but I decided to post here anyway just to...

Wow, great replies! Thanks everyone. Looks like my timing was perfect too, seeing as the white paper was release just days later.

I made a big gasket for my champaign bucket vacuum chamber using a four-section printed mold. IMG_20150521_161846.jpg3264×2448 1.54 MB IMG_20160902_225718.jpg2448×3264 1.06 MB I’ve since added another stick-on seal to the urethane, as busting it out of the mold was not too kind to it, and it had a couple rough spots that leaked a bit…

3D printed molds can be used for injection molding low-volume production plastic parts. Learn how with the Formlabs white paper.

It is not difficult to do the injection molding - you can see this under https://plasticlabs.wordpress.com/2016/09/06/how-to-bring-a-3d-printed-2-cavity-injection-mold-to-life-part-1/

it’s surprisingly easy for small parts! We just finished up a collaboration with Galomb Inc and shared our findings in the whitepaper which went out today.

Pauline, injecting wax should be easier than plastic. With the much lower melting point, your mold will experience much less stress, should last longer, and not require as much engineering consideration.

I sent in a ticket to Formlabs and they are checking for me to see if there would be a reaction between Polyurethane resin and the Formlabs resin as I was thinking of using the tough or Flexible resin as a Mold and just pour in the Poly replacing the need for Silicone Molds. (I use Smooth-On 321 and a few others) If a person can get more then 50 parts from a printed mold this may be a viable alternative. Main reason I am thinking is I do a lot of thin parts and experience a lot warping whereas a printed mold can have a thicker outer wall thus eliminating the warping. Here is a couple of screen shots of one of the items what I make for the hobby industry.

Yes it can be done. How difficult? No clue, but let us know if you try!! I assume outsourcing to someone like Fathom who already has this set up would be a good use of outsourcing. If you think you will be doing this sort of development a lot though, then I am sure bringing in a manual machine would be beneficial. I wouldn’t expect it to be as plug n play as a Form 2 though.

Hand operated injection molders for DIY injection molding. Ideal for R&D, materials testing, STEM programs. 3D print your own molds.

I’ve molded smooth-on simpact urethane resins (Shore A 60 and 85 IIRC) in printed molds before. You MUST really, really, really release them well prior, polish up the released surfaces with a soft cloth, and re-release/polish before every pour.

Definitely interested to see how others want to push this forward and try more elaborate things so please share your results on the forums! Happy to talk more about your specific application if you need any help figuring out the best approach.

I made the mistake of not releasing my first mold for simpact because I’d molded silicone parts a bunch of times in printed molds, and they came right out. With simpact, and no release agent, I had to basically break the mold off with a hammer!

How difficult would it be to DIY rapid injection mold (plastic parts)? My understanding is that rapid injection molding means injecting hot plastic into a mold which was 3D printed. Seems this would be possible with a machine like this:

I’m thinking this would be helpful to do in-house, after functional prototype tests and before short runs with a service like QuickParts or ProtoLabs. I think I’ve only seen one example of this with a Formlabs printer: