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  1. #1
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    Default Rotational casting machine

    This is barely metalwork related, I'm afraid, but the machine I built is made from metals

    As some of you know, I restore old motorcycles. Once in a while, an issue with supplies of spare parts makes it worthwhile to set up tooling to make replicas of parts for a whole community of enthusiasts.
    This was the case recently with the coolant overflow bottles for 1978 to 1983 models Honda CX500 and 650 bikes (including the turbo versions). None of the 4 types used over those years are availalbe any longer new (for the past 10 years or more) and they are all getting brittle and unreliable now.
    Originally made by blow moulding of polyethylene, which is faaaar to expensive to set up for small runs. A quote by a friend was in the order of $12,000
    So I read myself into the various plastics manufacturing methods of hollow items and eventually landed on rotational casting for this purpose.
    In priciple, a thin flexible mould is made from silicone (called a ''glove mould'), supported by a hard shell made around the outside of it. The hard shell is arranged to be split and separated from the silicon glove. Once the original part - in effect the pattern - is removed for the arrangement and the mould reassembled, a quanity of liquid polyurethane is poured into the mould, the opening plugged and the whole assembly rotated in two axes to distribute the liquid plastic all around the walls of the mould. This is continued until the plastic sets (from minutes to hours, depending on the material properties).
    The usual arrangement is a rotation machine with a timer.
    So I set out to survey my scrap and useful spaces, and came up with a collection of materials that could be recycled into such a machine.
    The result may be of interest to others, so here is a picture and a video of it running (empty). The mould is fastened inside the inner rotating frame with rubber bands or metal straps or tape.
    One of the bottle shapes:
    Coolant Bottle1.jpg
    The machine:
    IMAG0021_28Small29.jpg
    A video:
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  2. #2
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    Jul 2010
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    Melbourne
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    Default

    Hi Joe,

    Looks good... but
    Isnt it going a little fast?
    Also I think you need to change your gearing, one side of your inner frame is almost always on top and the pattern repeats every 360'

    Of course I've not made one , maybe its up and running and working just fine.. in which case forget my drivel.

    Stuart

  3. #3
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    Default

    Hi Joe,
    Nice work, where did you come up with the idea from, was it something seen or own idea? Who's CNC machine did you rob for the framing??? Be interesting to see if the finished product turns out OK.
    Kryn
    To grow old is mandatory, growing up is optional.

  4. #4
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    Default

    Something to look for Stuart, testing will tell - its running at 20rpm. I can't see the pattern of inner frame yet..... it seems to be on top just as long as it is facing down - to my eyes. I'll put some colour on one side so it becomes more obvious if there is an uneven pattern.

    Kryn, I didn't invent anything, just adapted stuff I had. Plenty of documents and youtube videos on the subject.
    Mo CNC ever touched any part of my machine..... what made you think that?
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  5. #5
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    Hi Joe,
    Thanks for that. The reason I asked about the framing for your rotary moulding machine, is it looks similar material to what is used on a CNC machine.
    Kryn
    To grow old is mandatory, growing up is optional.

  6. #6
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    Melbourne
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    Quote Originally Posted by jhovel View Post
    I'll put some colour on one side so it becomes more obvious if there is an uneven pattern.
    That might help. Its not thats it uneven... in fact I think uneven is what you are after. Hard to explain, but it might be easier to see it if you shift the inner frame a little from where it is in the video so you start with the outer frame horizontal and the inner frame vertical. Turn the outer 180' which turned the inner 180'. So the side of the inner that started on top is back on top. Set up like that the "top" inner will never be "upside down". I don't think adjusting the start points will fix things, only changing the gearing ratio.

    Of course I could be wrong

  7. #7
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    Now you explain the motion like that, you are probably right. Changing the ratio is pretty easy: just turn down the fixed pulley a bit - that will reduce the speed a bit too.
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

  8. #8
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    Oct 2011
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    Norwood-ish, Adelaide
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    Quote Originally Posted by KBs PensNmore View Post
    The framing for your rotary moulding machine, is it looks similar material to what is used on a CNC machine.
    That stuff is Al extrusion and these days used in places rather than welded steel framing. Costs more but doesn't need painting is quick to put together and there are a whole bunch of accessories that can bolt onto/ into it. Theoretically it is reusable but most places I've seen it used may disassemble but to reuse uses more time than it costs to order new. Being Al it can be recycled though. See https://8020.net/action

    Michael

  9. #9
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    You are right on the buttom Michael. It came from the Bosch auction, where it was picked up by GregQ, who gave it to me when he moved North. So repurposed.
    Cheers, Joe
    retired - less energy, more time to contemplate projects and more shed time....

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