Injection Moulding
27 Apr 2012 11:50 #19582
by BigJohnT
Injection Moulding was created by BigJohnT
How feasible is it to make a short run injection moulding machine using hydraulic jacks for some PVC parts? I'm talking about making 100 parts by hand...
I hope Wizard69 and anyone else that works in the injection moulding industry chimes in...
John
I hope Wizard69 and anyone else that works in the injection moulding industry chimes in...
John
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27 Apr 2012 13:46 #19584
by ArcEye
Replied by ArcEye on topic Re:Injection Moulding
Hi John
I know nothing about the subject in practical terms, but looking at these, I'd say highly feasible
www.mediummachinery.com/
www.injectionmolder.net/
www.lindsaybks.com/dgjp/djgbk/inject/index.html
regards
I know nothing about the subject in practical terms, but looking at these, I'd say highly feasible
www.mediummachinery.com/
www.injectionmolder.net/
www.lindsaybks.com/dgjp/djgbk/inject/index.html
regards
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27 Apr 2012 15:18 #19585
by BigJohnT
Replied by BigJohnT on topic Re:Injection Moulding
ArcEye,
Thanks for the links I passed them on to Erik. The first one was more like what I was thinking about.
John
Thanks for the links I passed them on to Erik. The first one was more like what I was thinking about.
John
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28 Apr 2012 00:41 #19600
by arch dude
Replied by arch dude on topic Re:Injection Moulding
I know nothing about injection molding except what is available at Wikipedia:
en.wikipedia.org/wiki/Injection_molding
en.wikipedia.org/wiki/Injection_molding_machine
Injection molding requires a large mount of force for two separatebut related reasons. First, you must compress the plastic feed material to about 13,000psi. Next, you must clamp the two pieces of your mold to prevent the plastic from forcing them apart. If the cross-section of the plastic at the interface beween the two mold pieces is one square inch, then you need 13,000 lbs (7.5 tons) of force to keep the two pieces together.
See:
www.moldingmanual.com/
For an excellent explanation. If I were to actually use injection molding, I would send this guy some money just to acknowlege his contrbution.
For high volume, It's clear that the clamping force dominates. But for low volumes. I think that you should be able to use brute-force clamping methoda, such as multip.e nuts and bolts. Sure, thsi meabs that you can only produce 5 parts per hour instead of 20 parts per minute, but this is uirrelevant whe you only need 100 parts.
en.wikipedia.org/wiki/Injection_molding
en.wikipedia.org/wiki/Injection_molding_machine
Injection molding requires a large mount of force for two separatebut related reasons. First, you must compress the plastic feed material to about 13,000psi. Next, you must clamp the two pieces of your mold to prevent the plastic from forcing them apart. If the cross-section of the plastic at the interface beween the two mold pieces is one square inch, then you need 13,000 lbs (7.5 tons) of force to keep the two pieces together.
See:
www.moldingmanual.com/
For an excellent explanation. If I were to actually use injection molding, I would send this guy some money just to acknowlege his contrbution.
For high volume, It's clear that the clamping force dominates. But for low volumes. I think that you should be able to use brute-force clamping methoda, such as multip.e nuts and bolts. Sure, thsi meabs that you can only produce 5 parts per hour instead of 20 parts per minute, but this is uirrelevant whe you only need 100 parts.
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28 Apr 2012 19:21 #19614
by BigJohnT
Replied by BigJohnT on topic Re:Injection Moulding
Thanks for the links, some good reading. I was thinking hydraulic jack technology might be the best for short runs to supply enough pressure.
John
John
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19 Jul 2012 16:03 - 19 Jul 2012 16:05 #22212
by tenaja
Replied by tenaja on topic Re:Injection Moulding
John, I think you will run into speed issues with hydraulic jacks. The mold should be cold enough to freeze the plastic, and it should be able to do it within a few seconds--certainly less than half a minute.
For reference, a one-oz part on a "real" machine typically has a 45 second cycle time when run slow, and that includes open, eject, close, inject, & hold (freeze).
For home-made stuff, they usually use a mechanical lever to apply pressure, if not an air cylinder. I think speed will be more important that maximum pressure, unless you are trying to eliminate sink from a mediocre design, or you are trying to fill thin deep slots. If you need, you can add a long stroke air cyl to your long lever so you get pressure and consistency.
For reference, a one-oz part on a "real" machine typically has a 45 second cycle time when run slow, and that includes open, eject, close, inject, & hold (freeze).
For home-made stuff, they usually use a mechanical lever to apply pressure, if not an air cylinder. I think speed will be more important that maximum pressure, unless you are trying to eliminate sink from a mediocre design, or you are trying to fill thin deep slots. If you need, you can add a long stroke air cyl to your long lever so you get pressure and consistency.
Last edit: 19 Jul 2012 16:05 by tenaja.
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25 Sep 2012 04:24 #24597
by gandalf69
Replied by gandalf69 on topic Re:Injection Moulding
A long time ago we used to encapsulate relay coils with Polypropylene (PP) using a manually operated toggle link platen and a hand operated spoked wheel (~600mm dia) driving the rack and pinion injection ram (~20mm dia).
Slow going, hard work but it did the job just fine. It would work with PVC too.
Slow going, hard work but it did the job just fine. It would work with PVC too.
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