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  • Home made injection press

    I was looking through here and someone mentioned making a home made injection press.
    I am thinking about doing some small rubber molds for motorcycle parts which are no longer available.
    Where would I find some info on making my own injection press ?
    Thanks,
    Martin

  • #2
    here....
    http://www.lindsaybks.com/

    very good books....

    -- jerry robinson
    dvideo

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    • #3
      you might think about harbor freight and their presses... it would be a nice mix.

      -- jr
      dvideo

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      • #4
        Yeah, I'm building one now. I started with the Gingery book fro Lindsey but I couldn't take all that angle iron. So I redesigned it until I liked it. Plus he would make statements like: the piston may stick when you first start to pull it down so use your other hand to guide it. That's just screamed to me... poor design, and dangerous.

        I have some drawings here and will be posting photos shortly.
        http://www.vers5d.com/metal/molder/

        Basically you're looking at a big hot-glue gun. They're pretty simple at this level. Probably the most inportant part is temperature control. Don't want to burn the material but it needs enough latent heat to flow completely through the mold.

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        • #5
          Beginning in the May/June 1991 HSM, there was a four-part article by Rodney Hanson called "Hand-operated Plastic Injection Molding Machine." Those issues are no longer available but the article is included in the "Projects Five" book or photocopies of the article could be purchased through our circulation department (800) 447-7367.

          Neil

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          • #6
            I did something like this years ago only I used a 2 1/2 ton arbor press. I turned a 2.0 dia bore injector from brass with a .125 sprew. Heated it to the right temperature for my material (polypropelene) in a toaster oven. Popped it in the press, put a six foot booster bar on the press and hung my 220 lb ass on the end. The injected part was about 4.0 sq by .5 thick. Takes a lot of hydralic pressure to inject the plastic and a LOT of clamping pressure to keep the mold from opening up. Successfully made around 60 parts for less than $20.00. A local prototyper wanted $3200.00 for the job. Bob.
            PS: Look into arbor presses, might save you some fabrication.

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            • #7
              What kind of quality can be expected from a homemade machine like this?

              Are the fumes of the plastic hazardous to health in any way?

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              • #8
                The quality depends more on the mold, and if there are fumes the heat is probably too high.

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                • #9
                  YES the fumes are hazardous. But if there is a lot of smoke it is too hot. I worked where they extruded polypropolene into a sheet, then cut it into string then wound it into carpet fiber. The process was not too complicated, just a heater block with thermocouple control and gear pumped extrusion. Constantly they were taking temperature off the line thou.
                  (powdercoat paint gives off similar fumes from the polyester base and will give you a sore throat is proper ventilation is not followed)

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                  • #10
                    I remmeber the fumes from my work at a cabelfactory, nasty!

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                    • #11
                      Axel,
                      The quality of your part is more of a function of your mold than your injector. If the mold is finished nicely, fillets and rounds where appropriate, good metal finish, enough draft angle so the part can be removed from the mold... your parts will be nice. If the molder has a large enough shot, and it heats up enough, you'll get good parts. The design of these small inj molders has a lot to do with how easy it is to make multiple parts.

                      I've made a few different styles, and they are great fun to use.

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                      • #12
                        I know nada about injection molding! but have thougt about trying, making parts for models and guns. Can any kind of plastic be used? are there any restrictions?

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                        • #13
                          I discussed this topic with my wife. If you ever, ever want to have a conversation that will make you laugh for years, this is a good candidate.

                          It started well enough. I told her I wanted to buy a used Boy machine. This got a funny look. She said we had boys. No.. NO.. I mean for plastics injection. It's a good, small, well supported machine done by web savy people. I can get parts. This whole line of talk devolved to "we can't afford to make shoes in this country" to "are we going to make shoes?" - and then still further downhill.

                          Bottom line... I have my mills and lathes. I can build a hacked Gingery design with the Harbor Freight Presses this summer.... and make molds with the smallest daughter. Plastic animals first. Shoes come later.

                          -- jerry
                          dvideo

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                          • #14
                            Martin, try a search on the web for injection molding plastics and you will get info on lots of places to start learning about it.
                            I have used ABS and high density polyethylene for small high-strength parts and it is easy to work with. You can buy small quantities of virgin(new) or recycled plastics in granular form. They all melt at about 475F to 500F (245-260C).
                            There are lots of sizes of injection molding machines. I picked up a 30 year old machine with a 2 ounce capacity out of the newspaper for $250, but they are not that complicated to make.
                            The big thing will be making the mold. You have to learn to think backwards and inside out! And the finish on the part is only as good as the finish on the mold. Check your library or local technical school for textbooks on making molds. They will tell you how thick the part can be, sprue design for incoming molten plastic, etc. It's fun, try it!


                            [This message has been edited by ShavingMaker (edited 03-01-2003).]

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                            • #15
                              Duplicated post, can't figure how to delete second message. Sorry

                              [This message has been edited by ShavingMaker (edited 03-01-2003).]

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