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Plastic Injection Molder

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cs900

maker of chips
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Do I have a use for one? Nope...
Was that going to stop me from making one? Absolutely not....

So I did...
20161025_205516_zpsefehlldg.jpg

It has an 80/20 frame (I love that stuff!) which started out life as some drill press chip guards that my old employer was throwing out. What a waist. Slap a few 1/2 aluminum plates on it to hold it all toghether and you've got yourself a nice sturdy frame.

Then came the fun task of making the heater barrel. I ended up using an old shock absorber tube as the main chamber. It already has a nice polished inside and was sized for standard orings. It made sense at the time and was free. I machined a cap for the tube which has a countersunk taper on the inside, and welded it together. I then machined an aluminum heat sink which is press fit over top of the steel shock tube. Slapped a few band heaters on it (which are way overkill!) and a flat mounting flange at the top and off I went. I wanted the heater to be out of the way when not in use so I mounted the heater assembly to the frame via 2 shoulder bolts with springs. The springs hold the heater assembly up when not in use, but as the plunger moves down during the injection cycle it hits the plastic "charge" which provides enough back pressure that it pushes the assembly down onto the mold. Of course once on the mold the heater can't move any more so the cylinder proceeds to push the plastic charge into the mold. Mission accomplished!

Only parts to make after that were the nozzles and the plunger head. Having absolutely no knowledge about injection molding I made 2 nozzles, one with a .125 orifice and the other with a .090 orifice. Can't tell you if there is an advantage of one over the other yet, but time will tell. The plunger itself is a large brass slug that threads into the air cylinder shaft. It has a mating countersink angle to the heater tube cap to ensure that I can extract as much plastic out of the barrel as possible. It also has a very high temp oring installed. No idea if the oring will last or not, but I thought it might be a good idea anyway.

Moving to the funny looking enclosure next to it we have a full PID heater apparatus which runs a solid state relay to power the AC band heaters. the LED lights next to the control indicate that the heaters are under power. Next to those is the cylinder control, which is just a 3 way, non-returning valve. And of course we have the main power switch and power indicator.

So I tested it out last night. Nothing overly exciting, but it worked great!:excitement:
20161025_213932_zpsss6hjiuh.jpg
looks like I should preheat my aluminum mold a bit before hand, but otherwise it filled completely and holds the small machining marks even. I'm pretty happy for a first go around. Although I did crush my coffee can spacer, haha. Better stick with wood from here on out.:eek 2:
 

quickcut

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Neat machine, What type of plastic are you using. On top of your temperature controller there are some pellets(I think) is that the plastic you are using? Secondly your preset temp shows 400 (f) . Have you found an ideal melting temp? Thanks

charles
 

cs900

maker of chips
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Messages
241
The parts i've done so far are ABS, and that is what is on top of the controller.

as far as temperature, I'm still playing with that. The thermocouple currently is mounted into a hole drilled into the side of the heat barrel, but I still don't think it gives an accurate inside temperature. So I really need to play with it a bit more before I know for sure what temps I can run reliably.
 
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