plunge moulding disasters

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Blue Elephant
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plunge moulding disasters

Post by Blue Elephant »

Encouraged by any number of articles involving plunge moulding, I had several goes at it. I purchased some Evergreen 10thou clear sheets....they just dissolved into a big hole with a clear surround. Is this stuff unsuitable for the purpose or am I simply holding it too close to the source of heat (a birthday candle)? I've been having mixed results with other clear materials as well....scorching, wrinkling etc etc. I even went to the trouble to mount a plasticine block on a nail, and sunk into a pre drilled hole an old chopping board to give me some clearance when I lower the plastic sheeting over the master...................the plasticine block/nail was frozen solid aftera few days in our freezer... but still turned into a soft,sticky mess. Any advice would be gratefully received................I'm having trouble with stretching sprue also, but that's another tale of woe for a later date! :???:
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mattbacon
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Re: plunge moulding disasters

Post by mattbacon »

Well... your heat source is no good for a start. You need something that creates an even heat over the whole area you are going to stretch, and you DON'T want an actual source of ignition! The best heat sources are a grill that's been well heated, or a "heat gun" (hair dryer with attitude). You'll need to practise with either, though. With my gas grill, holding the sheet about 2" below it for about 20-30s was enough to get it to soften. You should also cut a hole slightly larger than the part you want to make out of a rather larger piece of thin plywood or stiff hardboard. Use drawing pins to attach your plastic sheet to the board in 4-6 places around the hole (but far enough away that there is a wide margin of plastic around the hole, which will be drawn in to some extent). Hold (with an oven mitt) the sheet, attached to the board, under the grill until you see it just start to "sag" into the hole. At that point, whip it out, rest the other end of the board on something solid (worktop edge) to support it, and plunge the male master through the hole, steadily, and only far enough so that you can see the sheet has conformed to the shape. It'll take a few goes to get rightl I find that the best material is clear packaging plastic, of the sort you get around Easter eggs (or in smaller amounts around a pack of "King of Shaves" razor blades)

bestest,
M.
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nashorn
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Re: plunge moulding disasters

Post by nashorn »

Hi Matt, great information, very helpful, thanks for sharing it.

Rich.
Rich.
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Dazzled
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Re: plunge moulding disasters

Post by Dazzled »

Seconded Matt. Thanks for the comprehensive and helpful instructions. :)
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mattbacon
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Re: plunge moulding disasters

Post by mattbacon »

Thanks, guys... a picture's worth a thousand words:

Image
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bestest,
M.
Nigel Foster
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Re: plunge moulding disasters

Post by Nigel Foster »

Do you know if most hairdryers work for this process?

Thanks

Nigel
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