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Machine with 4″ bore cylinder.
My current machine uses this 5″ bore cylinder:
I’ve also built a machine using a 4″ bore cylinder:
I’ll upload an image of that machine.
The smaller cylinder should be adequate for most parts. Small, detailed parts made out of HDPE require a lot of pressure, that’s what I built the larger machine for.
My air compressor has a 30 gallon air tank.
The cylinder has a 5 inch bore and my air compressor is capable of about 140 psi so……..
radius * radius * pi * 140 = force
about 2,750 pounds maximum.
Here is a video of the machine in action.
The tiles look great. I’ve often wondered about mixing PET with other plastics, but the general consensus seems to be never mix plastics. PET is everywhere and hard to work with on it’s own. What is PP policy on this?
Also, I like your mold designs. Bolts work way better than clamps for most of us. I’ve been injecting HDPE at very high pressures with my pneumatic PP injection machine. The parts are perfect right out of the mold, no flashing to remove.
I’ll work on making a video.
With the cylinder and adding a valve to the injection tube it’s possible to pressurize the system and do multiple injections by threading on a mould, open the valve, close the valve, repeat. The cylinder keeps advancing the plunger for you.
Thanks for your hard work. The injection machine is simple, strong, easy to build and modify.
Just plastic, no other ingredients. I think HDPE would be strong enough for a properly designed watch. Small, detailed parts require higher injection pressures and i think polypropylene is easier to inject. @riceandcarry made sun glasses frames from polypropylene. Ask under the “Questions?” topic and more people with more knowledge about this will see it.
Here’s a picture of a part just out of the mold. The part on the right is the first prototype.
The spindle is 1.5 KW. I was able to machine the pocket shown in 24 minutes with a very dull HSS end mill, the depth is 10mm and the volume is about 30cc. I ordered some carbide end mills and I think I can improve that.
Hi, @tathata, thank you for the kind words. The plastic is HDPE and I’m using a Precious Plastic injection machine built exactly to the plans and then modifying it slightly as my previous posts show. The nozzle temp is 210C and the barrel is 190C.
I also love cnc machines. I’m now building a cnc router with the parts I’ve made. I think it will be rigid enough to cut aluminum using a 1.5 KW spindle. I’ll post my results under “Share you creations” here in the forums.
I hope this helps.
Here is the updated design, a lot stronger, and how how I get the holes in the right place. The pins are easy to remove with a drill or a small arbor press or even a drill press.
I couldn’t upload a dxf file. Here is a image of my current mold design.
Hi, I have changed the design a little to add a little more rigidity, I’ll upload my current dxf file. The bearings are 625 (5mm bore, 5mm wide, 16mm diameter. I’m going to machine a new mold tomorrow. Allowing for some shrinking is a little tricky.
To get all the holes in the right place I milled grooves in each half of the mold and drilled the holes for the aluminum framing. I placed threaded rods in the grooves and bolts in the holes and removed them after injecting the part. I then drilled the holes to size. I’m going to try 5mm rods in my new mold and try to press them out with a small arbor press. If that doesn’t work well I’ll go back to threaded rods, they are easy to unscrew.
Yes, I drew some inspiration from MPCNC. I’ve built some machines using maker slide with the plastic rollers and I think this is more rigid, that was my intent. I designed the slides around larger tubing, 1.5″(38mm) tubing for more rigidity as well. Do you know if 38mm is a common size in Europe? 1.5″ tubing is easy to get and pretty cheap here in the US. I’ll share my results here when I finish a machine with these parts. An inexpensive machine to make molds is my intent.
Here are some pictures of my parts. They are bearing holders for linear slides for a cnc machine. They are 20mm thick and about 50cc of HDPE.
I added a heater to the top of the tube and moved the temp sensor below the hopper.