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IndustryArena Forum > MetalWorking > Moldmaking > DIY Injection Moulding
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  1. #1
    Join Date
    Nov 2008
    Posts
    37

    DIY Injection Moulding

    Hi everyone, hope you're all doing well.

    I've been doing a bit of research into bench top/hobby injection moulding machines as I've got an application in mind which will require small runs of parts to be manufactured (runs of 100 or so). Machining them isn't an option due to the complexity of the parts.

    I've already got a cnc mill and making the actual mould shouldn't present any major issues for me.

    It seems like most of the bench top moulders are understandably smaller shot sizes (under 20g) and the injecting force is provided by a hand operated lever. I'm after something a bit more capable than that. Just for info the largest part I can envisage manufacturing would be a suspension arm for an R/C car at approx dimensions of 100mm x 40mm x 10mm weighing around 40g.

    Now here's my question.......

    If the limitation on part size is merely related to the force available to push the plastic into the mould, then it seems like a fairly straightforward job to design a machine that utilises a hydraulic ram or bottle jack to provide much more force

    Draper 12 Tonne Hydraulic Bottle Jack 39057 from ToolLine << This is a 12tonne rated bottle jack for not much money.

    Am I missing something here? Besides the obvious issues of safety.

    Thanks for your help,

    Rich

  2. #2
    Join Date
    Jan 2006
    Posts
    2985
    You obviously need enough volume of molten plastic to fill the mold. I think the more important parameter is speed. The plastic cools almost instantly when it hits the mold so you need a large force and a fast stroke. A hand pump hydraulic jack is not going to cut it. The plastic will solidify before the mold is full. I would think you could use something like a log splitter setup that would give you a quicker cycle time. Even that I am not sure is fast enough. The faster it goes in the better.

    Matt

  3. #3
    Join Date
    Nov 2008
    Posts
    37
    Thank you for the advice, that all makes perfect sense. I guess I could use the bottle jack to preload some die springs, releasing those would give me the speedy action I'm after. Best start sketching something up!

  4. #4
    Join Date
    Mar 2012
    Posts
    378
    I have been working on an injection machine that has a chamber with a 1/2" diameter and a 6" stroke. Would be easy to make it a little bit bigger if needed. It is based loosely on the one in the Vince Gingery book "Plastic Injection Molding Machine". I have been swamped with other projects so I have just made the main block and head so far. The chamber was drilled and reamed on my lathe. (I did it on the lathe because the vise, 6 1/4" tall block, and long reamer were a bit tall on my milling machine) One end was threaded for a brass pipe plug that was made into the injector head. I have a 300W cartridge heater from McMaster Carr that goes in the second hole to heat it up. I have not built the frame yet.

    Mine will probably have a manual pull handle. It would not be hard to use an air cylinder to actuate it. If you can't find one with a big enough bore you can get more leverage putting it on the end of the manual handle. I have two 2" bore, 14" stroke air cylinders from Automation Direct as lifting springs on my Bridgeport CNC conversion and they were something like $120 each.
    Attached Thumbnails Attached Thumbnails IMAG0219-1.jpg   IMAG0220-1.jpg  

  5. #5
    Join Date
    Nov 2008
    Posts
    37
    That looks very interesting. I'll get hold of that book too, seems like a good place to start.

    Thanks for the help everyone!

  6. #6
    Join Date
    Aug 2011
    Posts
    0
    hello, i have 15 years experience as a moldmaker and diecaster, u need speed to push the plastic into the mold before it begins to harden or u will have porosity in your parts that u want to create, u also need controlled pressure or u will begin to blow the mold open and cause excessive flashing.......a hydraulic pump, regulator, valve and cylinder would be best

  7. #7
    Join Date
    May 2010
    Posts
    34
    Rich,

    I have purchased several injection molders starting with a very small one with a had clamping mechanism. When I started selling my first product there was no way to keep up with the demand. I had people in my garage hand cranking parts for 18 hours a day and they left with sore arms and fingers. What a joke! I bought a real molder with pneumatic toggle and it paid its self off in a few days.

    I would like to point out that you may be able to make your own machine but you will waste a lot of time that you could have been making parts. There is no reason to re-invent the wheel.

    Consider buying the one I just posted on ebay or buy a broken one and fix it.

    SP3 Injection molding machine & mold like Morgan Press | eBay

    The cycle time on this machine can be in the seconds where one with a hand clamped mold is in the minutes.

    This video might be helpful to you

    SP3 injection molder for sale - YouTube

  8. #8
    Quote Originally Posted by Hyrum View Post
    Rich,

    I have purchased several injection molders starting with a very small one with a had clamping mechanism. When I started selling my first product there was no way to keep up with the demand. I had people in my garage hand cranking parts for 18 hours a day and they left with sore arms and fingers. What a joke! I bought a real molder with pneumatic toggle and it paid its self off in a few days.

    I would like to point out that you may be able to make your own machine but you will waste a lot of time that you could have been making parts. There is no reason to re-invent the wheel.

    Consider buying the one I just posted on ebay or buy a broken one and fix it.

    SP3 Injection molding machine & mold like Morgan Press | eBay

    The cycle time on this machine can be in the seconds where one with a hand clamped mold is in the minutes.

    This video might be helpful to you

    SP3 injection molder for sale - YouTube
    Nice video ! thanks for sharing this video and providing some knowledge related to injection molding.

  9. #9
    Join Date
    Apr 2010
    Posts
    6
    Excellent video, thanks very much, as a newbie i gave me a very good idea how the process works. What is the brand name, tonnage and max. injection volume? Is it still available?

    Jacques

  10. #10
    Join Date
    May 2010
    Posts
    34
    Quote Originally Posted by jjjac View Post
    Excellent video, thanks very much, as a newbie i gave me a very good idea how the process works. What is the brand name, tonnage and max. injection volume? Is it still available?

    Jacques
    That machine is very old and is probably the last of its kind still around. I have not seen another like it. I sold it a year ago but a comparable machine is a Morgan Press. A new one is about $20k but I have seen used ones go for 2-8 thousand dollars depending on condition. I got mine for $800 from a guy that found it cleaning a house and didnt know what it was. The customer support is very good and spare parts ar available for them even if they are 30+ years old!

  11. #11
    Join Date
    Jul 2017
    Posts
    1

    Re: DIY Injection Moulding

    We have the silicone injection molding capability to cost-effectively construct your multifaceted components with utmost accuracy and efficiency.

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