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  1. #1
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    Is there any way to melt plastic and squirt it into molds without expensive machinery? I'm talking about production runs of maybe 5-10 pieces. Taking the parts out by hand, no ejector pins or slides involved.
    steve

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    There used to be a small molding machine that would fit under a drill press spindle and the spindle force would shoot hot plastic into simple molds. I am sure someone in the forum has seen this. I don't have a link. Might try posting in the EDM forum..more mold builders in there.

    TMD

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    Done it myself! It's not that hard.

    There are a bunch of different appraoches to this. Depends on what kind of plastic you are trying to mold etc.

    If you are going to be working with a thermoplastic like a polyethalean (one of my personal favs) then you are going to want to whip up a basic heated cyclander with plunger.

    If you are going to be working with a resin based plastic, then you don't need the heat.

    I've done both these things, with jury rigged home shop style equipment with great success.

    If you could let us know more about what specifcally you are interested in creating I could give more specific suggestions... though I am certainly aware of the desire to avoid specificity in the developement of prototypes etc...

    B

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    Im not starting a business, so no secrecy here. I was just thinking of making something that clips onto the rails of the bottom of an HK USP40. Something that holds a tiny flashlight or a laser. Not sure of what type of plastic the frame is made out of, but I think it is resin.
    I worked as a moldmakers apprentice for a little over three years(about 5 years ago), but never got the chance to visit any of the shops where they actually made the pieces.

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    There's a book about injection molding small plastic parts on eBay:
    http://cgi.ebay.com/BUILD-AN-INJECTI...QQcmdZViewItem

    No connection with seller, blah, blah...
    Roger

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    Well, ok then. You've got pleanty of knowledge about how to make a mold, now all you need is a plastic. For small runs, I suspect that you'll best off using a resin based plastic. There are a lot ot choose from... and you'll need to get the appropriate release as well.

    Here are a couple of companies that you could check out...

    www.smoothon.com
    www.polytek.com

    They both sell various different resin set plastics with various different properties.

    If you are trying to get these things in through a fine sprue, you can mix the stuff up and then suck some up into a disposable syringe and then squirt the stuff into your mold. Even with the faster setting stuff you should be able to get a dozen or so sqirts in.

    Sometimes you'll get some air bubbles this way... if you do and you want to get rid of them, you'll be best off taking the mold after all your squirting is done and putting the whole thing into a pressure pot (grainger) and pressurizing the thing up to 50 psi. This will cause the air bubbles to desolve in the plastic and disapear.

    Good luck.

    B

  7. #7
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    It depends on what type of plastic your piece needs.

    There are two-part epoxies, polyesters and urethanes that only need to be mixed and poured. A little vibration or centrifugal force will get the air bubbles out. And parts can be cast from RTV molds. Simple and cheap.

    If it absolutely has to be a thermo-plastic, try that book mentioned above on building your own plastic injection-molding machine. This is a Lindsay Publication and is available at: http://www.lindsaybks.com/

    Wayne

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    You can Build one, not to much of a problem.
    First thing though, find out how many oz's
    each shot requires. If you are just doing a
    reload / shot method, then a simple plunger
    will suffice. If not then you are looking at
    a more complex injection group that you will
    have to fabricate. Requiring:
    Barrel, Feed Screw, Torpedoe, Check Ring,
    a Hydraulic Power Supply, Hydraulic Motor,
    Hydraulic Cylinder, 240V Heater Bands, Nozzel,
    Nozzel Heater Band, Required # of Controlers,
    Hydraulic Manifold, Presure & Flow Control Valves
    Presure Gages (aprox 3), Required Hydraulic Hoses
    And the required lengths of 1"x10" steel plate,
    and required hardware, to build the carrage.
    This is called an Injection Group, sounds hard,
    but I made one in about 2 weeks time a few years
    ago. Principals you must understand when injection
    molding, are cycle time, Injection presure,
    Holding Presure, Back Presure, Injection & Feed
    rates,& Clamping Presure, etc.. If you truely
    want to build an Injection Molding Machine, I
    have a few blue Prints of a few comercial machines
    Nissi, Engel, Battenfeld, that I could copy for
    you. Just email me.
    Good Luck in your endevour.
    Jim

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    low volumn urethane molding in silicone rubber molds is done all the time, you can do anything that can be done in injection molding but the piece price is much higher but low tooling costs. takes lots of skill to make first class parts.

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    One more thing I forgot to mention is that many of the 2 part plastics and rubbers are "Known to the State of California to" do all sorts of not great things to you before they are fully reacted, so do use rubber gloves and keep everything clean and under good control. If you are going to use a product with high VOCs (Polyesters and polyuratheans, among others) be careful with them too make sure you've got good ventilation, and wear a good organic vapor mask with good *fresh* cartriges. Just because you can't smell it, doesn't mean it's not strinking your gonads!!!

    But most of all have fun with this stuff... you can do really amazing things with the various castables.

    B

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    jimmech,
    I'm in the process of gathering parts to build a mini injection group based machine. It'd be great to have a look at some of those blueprints you have. My design exists only in my head, as I've been thinking about it for a couple of years now. I've been lucky to find plenty of items at my company that nobody wanted, such as heater bands, PID temp controllers, metal stock, etc. I'm not sure whether I want to build it using hydraulics or pneumatics yet. I know that pneumatics will give less force for molding and clamping(smaller shot sizes), but it should be a whole lot cleaner and easier, and I can always use a mechanical clamp for the mold. And my air compressor becomes a cheap power unit.

  12. #12
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    There are often some small lab/prototype benchtop injection molding machines for sale on Ebay.. I think one common brand is "Honajector" You can probably buy one of them cheaper than the components to build one, unless you just want to build one...

  13. #13
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    http://searcht.netscape.com/ns/boomf...bk%2Finject%2F

    This link works, sorry it is so long, just copy and paste or click on it. should work.

    TMD

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    Here is the machine I was looking for....

    http://www.morganindustriesinc.com/

    TMD

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    Okay, you want to hang a light on your HK USP40. Why don’t you try:

    http://www.streetpro.com/usp/surefire.html

    Before these fellows talk you into a $50,000 injection molding machine.

    My gut feeling is that a plastic part is not going to hold up for this application.

    Wayne

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    Default Low cost injection molding machine

    I came across this small plastic injection machine machine recently:

    http://www.techkits.com/pim

    Seems to be aimed for hobby use, prototyping or very small production runs.

    Ed

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    Quote Originally Posted by Metalmasta View Post
    I came across this small plastic injection machine machine recently:

    http://www.eatshit and die spammer.com/pim

    Seems to be aimed for hobby use, prototyping or very small production runs.

    Ed
    SPAMMER dredging up old post.

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    Default

    Looking at the dates it looks like Digger Doug dredging up an 8 year old spamming post to an even older post of 14 years ago.

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    Default

    The Net Police gotta police, ya know. No statute of limitations for the crime of spamming. :-)

  21. Likes Bill Simmons liked this post

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