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IndustryArena Forum > Material Technology > Plastic injection > 20 Ton press for injection molding machine
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  1. #13
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    Re: 20 Ton press for injection molding machine

    Quote Originally Posted by LeeWay View Post
    Okay. I hooked up the electronics and heater. Man, that heats up fast. Before I could get the controller set correctly, the heater blew out. I knew I should have disconnected it first.
    I considered the heater part to be consumable anyway. I have a few more on the way, but USA made ones too. A couple Chinese and a couple USA made should keep me going. I don't think the heater should have burned out, so it probably had a factory issue anyway. It was only up around 300 C, which is hotter than I will typically be using, but within operating range on the heater.

    The controller works great though. I was thinking that I might need two heat bands on this? No way. Now my pipe is 5" long. I have ordered a 3.5" instead. I think that will be a more suitable length.
    I also ordered the next size up for the ram. I will go ahead and bore out the new SS pipe nipple anyway. I am sure that will help eliminate some messy situations I could have had with standard pipe nipples.
    Since I already had the press, this is turning out to me one of the simpler things that I have made or tried to make. I still have a couple more projects that are in limbo for one reason or another, but still on the to do list.
    Hey Lee thats pretty neat what your doing. . I may eventually try some molding also. Oh and btw I have mfg electric heaters for a living last 24 years and yes here in the USA baby. You ever in need of a heater, T/C or controller just PM me and I can set you up.
    If you want really HOT I'd use a mineral insulated type nozzle band heater. The mica bands are good for barrels in larger diameters but the watt density is low like 30-40
    MI's can go to 150 watts/sq-in
    And ya hooking a heater up across the line and letting it rip will end badly.

  2. #14
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    Re: 20 Ton press for injection molding machine

    Thanks, Paul.
    I think I am covered on heaters for the moment, but I am interested in what you make.
    I will shoot you a PM and give you my email.

    Here is the first iteration of the mold for these knobs.
    I did a draft analysis in Fusion 360 and I did get a little orange on the part. Just a little red around the letters, but it is so shallow that it should not be an issue.
    I only drafted the sides of the knobs 1 degree. Where I did get some red was in the runner, but that should not be a problem. This is for a single color knob that gets no overmolding. It does get a stainless flange nut inserted into the part. It will thread onto a screw through the bottom holes and the screw will protrude into the molded knob about 1/2" depth. I include slots to help with the initial opening of the mold. Then unscrew the two screws a bit and tap them and the knob should pop loose.
    To reset, just spin another nut onto the screw. The two pins inside each knob just act to displace the plastic. I think I will add a third one right in front of the gate. I didn't want to disrupt the flow and not having any experience with it, I left it out. If it impedes the flow too much, I can just plug the dowel holes there.
    Anyway, there is quite a bit that goes into these molds, but F360 is certainly up to the task.

    Click image for larger version. 

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    Lee

  3. #15
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    Re: 20 Ton press for injection molding machine

    A little more about my thoughts on this mold.
    It will have some vent channels. Very shallow vent grooves running to the outside at the extents of the part. I will mold those in and they will be on the top half of the mold.

    I can use the bottom half of this mold with several different top halves if I want to do other knobs. As long as they are three lobe knobs. I was thinking about a red under molded knob as shown with raised letter. Then overmold that with black rubber or TPE. You would basically have to use two top halves for such a mold. The knobs would easily realign in the bottom mold. The base and letters would be visible and red and the rest would be rubberized plastic with grips molded in. I have no idea how much a bunch of knobs like that would cost in the grown up World, but I think it would be both fun and challenging from a hobby standpoint.
    Lee

  4. #16
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    Re: 20 Ton press for injection molding machine

    I have accumulated most of the stuff I need for this project.
    A few things still outstanding, but on the way. Switches and 1/16" end mills. I had a few, but all were too short.
    I will get to make some progress on it soon hopefully.
    I plan on machining the mold next week in the evenings.
    Stay tuned.
    Lee

  5. #17
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    Re: 20 Ton press for injection molding machine

    Well, my Son took his vacation this week and went hunting. That leaves only two of us here for production, so did not make any progress on this project. I will get the mold machined out this weekend. I want to turn a few items on the lathe too. Assuming everything is cool with Fusion 360, there should be a showing soon. Still looking for a good source for bright red ABS pellets. I have a good source for black TPE already.
    I found some nice red polyethelene. Too expensive. Polypropylene would probably be okay. I am tempted to chop up some 3D printer filament.
    That stuff is everywhere.
    Lee

  6. #18
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    Re: 20 Ton press for injection molding machine

    I'm actually selling a molder similar to what you are looking into building:

    http://www.cnczone.com/forums/tormac...8-tormach.html
    For Sale For Sale: Injection Molder | Panjo

    I hope you have a lot of patience. Injection molding is harder than it appears at first sight, especially with a hobby type machine. Your biggest issue will be that the injection speed is too slow and you will have to heat up the mold to a very high temperature just to be able to fill it (unless you are only doing tiny parts). Also, keeping the mold clamped shut might be a problem, the forces can be ridiculously huge. "Real" molders have huge amounts of clamping force (my new one has 50 tonnes). I would suggest to start with a mold with just one nest and a direct gate, less stuff that can go wrong

  7. #19
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    Re: 20 Ton press for injection molding machine

    Thanks for the info and suggestions. I have no doubt that I will run into some issues with this. I think i will take your suggestion about using a single cavity mold to start with. Then I will know more about designing a two cavity mold with runners.
    I will be using a 4" machining vise initially on this. I don't know what tonnage it can clamp to, but I think it should do.
    You mentioned on thing about the speed of injection and that has concerned me as well.
    This is the jack that I have on this press right now.


    I have the older orange version, but basically the same thing. It is no speed demon, but I can shorten the throw to only what is needed for the ram and that would be a couple inches. It can cover that distance pretty quickly. I still have the original manual jack as well if I need to redign to be more like the Medium Machinery design and get 20 tons of clamping pressure on the mold.
    I think that would be way overkill though.

    I would eventually like to design a small horizontal machine that would use a hydraulic pump and rams with an actual screw. That would be miles down the road though.
    Anyway, my current ambitions are only hobby grade at this point and this hot press should be enough to play with a few design elements.

    I would like to see your current machine though. Sounds like a nice one.
    Lee

  8. #20
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    Re: 20 Ton press for injection molding machine

    You can find a couple videos of my molder here: https://www.instagram.com/cordvision/ It's the yellow machine with Boy 50T written on it. I bought it used.

    About the speed: It really depends on the part. If it is thin walled, you need quite a bit of speed. Yours looks like it is solid all the way through, which will help but will take a very long time to cool off and you might have problems with sink marks. On a side note, make sure to have plenty of draft, especially if you have a big core, else it will be very difficult to remove the part from the mold.

    Those jacks move fairly quick when there is no load on them, but they slow down a lot with a load put on them.

  9. #21
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    Re: 20 Ton press for injection molding machine

    Thanks for that. Very nice upgrade.
    The proper drafts and what would work best for this type of part will be some of the learning curve.
    Of that I have no doubt. That will be part of the fun in it.

    I have seen quite a few different small hobby and benchtop setups.
    I haven't seen any of those that were rated for 20 tons, so one of the issues I may have is too much pressure.
    I would probably need to cap the air pressure while still maintaining the ram speed. I have seen those type valves, but have no clue how they work. I bought a big 1/2" pressure regulator for this, but I have already hijacked it to use in my whole shop air system.
    The one for this will just have to come a little later. I do have some smaller ones and will use one inline temporarily with quick disconnects.
    I was working on machining the plasticizer this evening, but while my collect seemed like it was holding the rod well, it slid some and so I have broken my first threading insert. The first of many I think.
    So, tomorrow evening I will install my lathe chuck for the first time and go from there.
    Lee

  10. #22
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    Re: 20 Ton press for injection molding machine

    Before buying my larger machine, I was thinking about modifying the medium machinery machine I had. I'm still wondering if it would have worked. I think there are two possible opions: Making it manually operated like the one seen
    at the end of this video: https://www.youtube.com/watch?v=kNNYcXK4Dmo . This would give you a much higher injection speed but you would loose a lot of injection pressure. It might also possible to somehow make a semi manual machine, where
    you start the injection process manually and just use the ram to pack the mold once it is full.

    Another option that I was thinking about was to pre-load a huge spring (think car suspension) that will store a lot of energy that could then be used to power the injection ram. I'm just not sure how you would control injection speed etc. and having
    a lot of energy stored in a big spring can be dangerous. Still like the idea though....

    BTW, it is a whole lot easier to inject HDPE or PP than ABS / PC-ABS. HDPE has usually a higher mold flow index but I'm not sure if it would be suited for your part.

  11. #23
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    Re: 20 Ton press for injection molding machine

    Now that is what I call a manual machine.
    I do have a decent model started on what my intentions are so far with this hot press.

    Attachment 304546

    The vise shown is a 6" and I will be using a 4".

    Most of the knobs I use are polypropylene, so I will probably just end up using that material. They are strong enough to do the job. ABS is just something I am familiar with.

    I have been considering using a rather large short ball screw. They come up on EBAY often enough.
    Then drive it with a double chain sprocket from a gear head motor. That might give me all the strength and speed I would need for the ram. That is if the air hydraulic jack doesn't do the job. Mold heating or cooling should not be an issue at the hobby level.
    If I wanted to produce a number of these, I would make more molds.
    I have also considered a large air cylinder, but until I have some numbers or an idea how much pressure the ram may need, I would not know what size to buy. Plenty of large US made ones on Ebay. If I had to go that route though, I would just make a full fledged horizontal bench to sized machine.
    Now that would be a project. I would look around for a smaller used machine before tackling something like that.
    Lee

  12. #24
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    Re: 20 Ton press for injection molding machine

    To be honest, financially speaking it would probably be better to just buy a small molder or mill the knobs/out source them. If you are doing it as a hobby it is of course an entirely different story. ABS is usually injected with 4500-15000 psi. If you know the projected area of your part (including runners etc.), you can now calculate how much force you need to keep your mold clamped shut. But as I said earlier... your main issue will be speed. Smaller parts like your knob are usually injected within 1-2 seconds, a hydraulic car jack is just not nearly fast enough. Check youtube, there's a bunch of small molders that use air cylinders which are much faster but usually aren't too strong.

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