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Old 06-14-2014, 09:01 PM   #91 (permalink)
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Subscribing to this thread. In the early '90s I worked in a extrusion blow molding plant as the mold setter. I always thought how simple it would be to make hoppers in a 2.5 lb shot machine. Most of the equipment the company used was made by Sterling and sizing was from 2.5 lb all the way up to 50 lb shot. Somewhere I have a video I took of a 10lb dual head machine cranking out traffic barrels 2 at a time every 2 minutes. A good mold maker could create a pair of molds with 4 chambers per mold or more if the part was small like a 50 rnd Winchester hopper and a good machine could crank out 6000 per shift. Hey Doc got any experience making molds?
If you find your video, I'd love to see it. I have seen so many of them on YT, but I always like to see new stuff. I like to study the process and see what I might run into and the solutions that might have been long discovered.
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Old 06-15-2014, 12:53 PM   #92 (permalink)
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Old 06-15-2014, 01:29 PM   #93 (permalink)
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The heater wiring is all done inside the box. Just need to hook up the hot side of the solid state relay and the electrical is done.

Remaining tasks:
Set up air hoses/regulators/flow restriction valve
Make funnel shaped hopper

Then I need some molds.
Molds maybe a challenge as we use shell molds with frames to hold it together. The psi to blow a bottle uses low pressure with a stretch rod to put a preform or parison is near 120 psi and high pressure of 400+ psi has the plastic to hit the mold.

How will you handle psi and clamp pressure?


There was a guy on nation that molded in an oven HDPE in clay shells to make a Tippmann hopper shell. This maybe easier...



No psi, you can lay flake instead of melting pellet so the shape isn't blow molded but lay molded, and you can get the 350+ F temp in an oven so its fire controlled.

Just trying to help. Most machines on a low end cost several thousand dollars so I doubt there is a cheep option to blow mold.
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Old 06-15-2014, 01:45 PM   #94 (permalink)
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My design is based off of a molder I saw on YT. He is getting really good results with his. Mine only has minor tweaks that would be more suited for paintball parts.

For clamp pressure, I'm not overly concerned. The molds will be held together with fasteners. Nuts will be used instead of threading into the molds for longer life. I don't expect ay issues since I should be coming nowhere near the tensile strength of the fasteners.

There will be a decent amount of trial and error, but I don't expect that to go on for very long before finding my ideal temps and pressure/feed rate.

Here is the video of mine:
http://www.youtube.com/watch?v=k0TMSxEo9kM

Here is the machine mine is based off of. He has since made another one that is beefier, or just looks that way because those are his cooling blocks. I don't really want to fuss with cooling yet and another guy who made a molding machine has given up on preheating his molds. He said that with some trial and error, he found the temp that suited his plastic and was able to get rid of the pre-heating.

The differences in mine:
1. I didn't like his centering system. My molds will be centered and running horizontal, not vertical. If I want to save costs on material, I will use pins in the mold to make the overall width proper.

2. The control box was good, but not linear in temperature. I have a PID box controlling my heater. That box is based off of another molder with additional tweaks. The SSR is elevated on .500 aluminum standoffs to help dissipate any heat that might build up. There is also a computer fan that runs any time the SSR is on. That and the pegboard top and back will circulate air to keep things reasonable.

3. He has a spring return on his valve. It's neither good nor bad, I just preferred to not have that. My valve does not have the spring return so I can keep it in place as long as I want. My fills will be larger/longer on the shells, so I wanted to be able to plunge and not have to hold it in case it's a longer wait.

4. My valve has threaded ports on the exhaust side too. I plan on running lines into a padded box to muffle the noise a little. It's not terrible, but I'd be wearing ears as it currently sits. There is a high pitched whoosh and I'd rather protect my hearing.

5. My material chamber, and the bore and stroke of my cylinder are larger. This wasn't a pissing contest. It was based off of the volume of the shells. The material chamber is almost double what the shell volume is. I don't expect to ever use the full stroke of the plunger, it can't bottom out anyway. Close, but not quite.

That said, here is the inspiration for my molder:

http://www.youtube.com/watch?v=T3Q6Q8vtZMQ
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New advertising tagline: "Simon Stevens said that will be totally fine and nothing bad could ever happen. Ever."
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Last edited by desertT1; 06-15-2014 at 02:18 PM.
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Old 07-03-2014, 02:08 AM   #95 (permalink)
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Forgot I never posted the pics of the little plastic injection machine we used to use to prototype parts (long before 3d printing existed). Looks to be close to the same size as the one your building.


The lower lever lifts the mold up to the nozzle, which is right below the little temp gage at the bottom.


Plastic is poured into the little cup (Yellow Arrow). Mold sits in the tray on the bottom (green arrow).



What the molds look like. About 7in long 3in wide
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Old 07-03-2014, 11:59 AM   #96 (permalink)
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Very cool. I'm trying to get the first batch of loaders sent out ASAP, then I'll put a little more time into designing/programming/CNC'ing the first mold for mine.
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