low pressure inj molding

[jimzz]

i want build a low pressure inj. machine.

i was thinking of using a hydraulic cylinder or air cylinder and heating it, however, the problem is with the seals handing up to 400f.

is there already something or maybe some synthetic seals if they can be found.

 

[MikeHalloran]

How big a part do you want to mold?


Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

Heating an air cylinder to power an injection stroke could result in some interesting control problems.

Teflon seal might work at those temps.

Regards
Pat
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[jimzz]

the size of the mold is roughly 2"x4"x4", a dome, sort of. i have made a wood one to test it, now i want to go to production

 

[jimzz]

well this is true, i was also thinking of some kind of gear pump

 

[MikeHalloran]

I knew a guy who made a machine like that. I don't think the injection cylinder had any seals at all. It was just a long heated vertical cylinder with a funnel at the top, and a really big air cylinder above that drove a close- fitting ram into it from above the funnel to force an injection.

He could make very good parts by precisely choreographing the cycle, all done by hand.
- Insert mold
- Measure and pour granules
- Wait for granules to melt
- Inject
- Withdraw ram, release mold clamps
- Disassemble the mold with an impact wrench
- Extract the part
- Reassemble the mold with an impact wrench
- repeat

His cycle time was usually around a minute. He'd tell you it was longer while negotiating prices, but you could hear the air cylinder in the background and time it yourself.

His molds were 'laminated', i.e. made from pieces of aluminum plate, keyed and bolted together, with no draft.

I think there are a few other guys who do things similarly. If you just need parts to use or sell, it would be cheaper to find one of those guys and work with him. If you're intending to go into the business, you'll need to accrue a lot of odd skills to get started.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

Like Mike says, a simple ram can work. A hydraulic ram gives a lot more control than an air cylinder though, and I think is a lot safer with regard to hot plastic potentially squirting out if the injection stroke is fired without the nozzle having a good seal with the mould.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[jimzz]

mike-pat,
yep, my thought was to use another powered cylinder to operate the ram for the plastic.

i am adding a low volume molding line to our machine shop.

and i didn't want to invest in a auger type machine.

just needed to bounce the concept.

any contact info for these guys.

thanks so much

 

[MikeHalloran]

Meister Tool Co Inc
King Hill Rd
Greenville, NY 12083
(518) 966-8295

I don't know who will answer the phone; it's been a long time.




Mike Halloran
Pembroke Pines, FL, USA

 

[HDS]

did you make your mill from scratch? get a used press or find a better process like FDM or thermoforming.

Here is a place to start looking (besides ebay).

http://www.stopol.com