Learning as I go - Plastic Injection

Let me start with, this has all been a learning process and like anything I like to learn what I am doing and test as much as possible. I finally got my resin mold up and going for the torso and had a few little mishaps, some I should be able to fix with minor setting changes.

I was able to fit the mold under the nozzle but needed to prop it up closer to the nozzle a bit more than it was. The little metal lift or wood stand that I was using for the smaller pieces ended up not working for this one. It was just too big so I thought by putting a soft cover book and some cardboard I would be able to lift it high enough. All in all it works but because the book/cardboard pieces bend when the extrusion is happening it created issues with consistent pressure as it was buckling.

You can see the book and cardboard pieces a bit better there. I would not recommend doing it this way as it created un even results. I plan to get a few pieces of hardboard which I already have cut to size and stack until I get it closer to the nozzle (hardboard will not buckle under pressure once it is stacked up). Clamping the mold was actually really easy and convinient.

It filled the mold but the pressure was not consistent because of the book/cardboard buckling under it and not enough pressure from my air compressor. I am currently running it at 60 PSI, my machine caps out at 90 PSI. I will be redoing the tests with this one with a higher PSI, starting with 70 next and comparing the results. This was a failed piece but did learn a lot from it. From better mold support to higher pressure so I will go ahead and tweak those first and test again. I plan to raise the heat up just a bit more so the plastic has less resistance when it goes into the mold. There is a lot of flashing as I am still learning what is "too much" and what is not enough.

I will admit I was a bit impatient and pulled the rods that create the undercuts in the leg/arms of the toy and ruined them. It bound so tightly to the model that once I pulled it just separated the pieces inside the model. All in all it was my mistake, I used compressed air to cool the part and in turn I am pretty sure I made the pieces brittle making them snap off easier. Thankfully I can easily re print more which is not an issue. Also use mold release, I have a spray on oil that is meant for this sort of work and helps a ton. I should of added more on the rods but left them a bit dry which was also my mistake.

I did a few more tests with other plastic pellets I had in hand, most of the results suffered from the same issues. So I am going to adding 10 more PSI of pressure, using hardboard to prop the mold up, re printing the rods to replace the ones that broke, and being more generous with my mold release. The main mold has worked out well so no real issues there. If this mold does work out well and I want to keep it for a while I may still debate in getting it made out of metal if I can find the right price. it just all comes down to how long the main mold will last.

On another note I decided to order a full face mask to do this work. Since I am working with pressure, hot plastic and resin that "could" break I rather be extra safe. I currently use a gas mask and my glasses since this stuff releases very nasty fumes so need to be extra safe. So a full facemark which should be comfier should arrive by tomorrow.

More tests and findings soon :)