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Post by Roger on May 23, 2015 6:04:19 GMT
I've recently been told about Precious Metal Clay by someone who makes jewellery, and they said it was also available in Bronze or Copper. That got me to wondering if there was any mileage in using it to create parts for Model Steam Locomotives. The clay is moulded into shape, air dried and then fired to sinter it into a solid. I was wondering if a mould could be 3D printed and the clay pressed into it, dried and then fired to get the desired shape. Obviously it wouldn't be as subtle or fine as 3D printing to wax and investment casting, but for things like brake hangers or other small cast parts, maybe it would be satisfactory. If you google 'metal clay' and search on YouTube, there's quite a lot about it. And here's a link to a project for printing the stuff directly. Initially I didn't think the resolution of this was that good but they claim and X/Y of 10 microns and s Z of 2 microns which is much better than most 3D printers.
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Post by AndrewP on May 23, 2015 10:08:41 GMT
The shrinkage on pmc is 8-10% so needs accounting for. I find the finished product a bit "soft" and very porous - silver soldering on it it sucks up the solder like mad. I am not happy to sell items made with it to my customers so continue to do it the hard way - now pass the hammer. Andy
ps B****y expensive too !
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Post by Roger on May 23, 2015 16:42:29 GMT
Thanks for that Andy, I did wonder how strong it would be.
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Post by Roger on May 24, 2015 7:21:47 GMT
Just a couple more thoughts on this. I found a YouTube video what showed someone making his own Metal Clay from the same ingredients that they use for the commercial products. He was claiming that it was very much cheaper to make your own. Obviously Silver Solder is expensive, but is there a cheaper brazing rod that could be used to flood the voids and give it more strength? Would Soft Solder be used for that to make is stronger? I know soft solder is weak, but it might make a huge difference if it's between the grains. I feel some experiments coming on...
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Post by AndrewP on May 24, 2015 11:07:15 GMT
That is more interesting Roger, do you have a link to the video? I can't help with the solder I am afraid, my experience, and interest really, is with precious metals, mainly silver, so I don't have that choice. Experiment away and report back Andy
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Post by Roger on May 24, 2015 11:29:53 GMT
Hi Andy, Here's the link to that guy who mixes his own metal clay. I think it's an interesting concept, and not something I thought could be done at home. It clearly has a lot of limitations from a Model Engineering point of view but there might be the odd thing that could be usefully made from it.
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jem
Elder Statesman
Posts: 1,065
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Post by jem on May 24, 2015 17:11:27 GMT
I wonder if it would be any good for bearings?
Jem
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Post by Roger on May 24, 2015 21:23:20 GMT
I wonder if it would be any good for bearings? Jem That's an interesting thought, I guess it's similar to Oilite bearings. I presume you mean if it was soaked in oil for some time to absorb it. I would imagine you'd need to put it under a vacuum for that to work, I doubt if you'd get oil to get right into the heart of the structure without doing that.
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jem
Elder Statesman
Posts: 1,065
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Post by jem on May 25, 2015 17:00:30 GMT
I vacuum chamber is not very difficult to build. An old fridge provides the vacuum pump, also a small pressure pump by the way. and a chamber in perspex no problem, I made one many years ago for testing underwater cases etc. I would think that it would be a very useful piece of kit for the model engineer?
Jem
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pault
Elder Statesman
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Post by pault on May 25, 2015 18:26:02 GMT
I would have thought you would want to put the chamber under pressure rather than a vacuum to force the oil in. We used to soak oillite bushes in oil for 24 hours before fitting them. It was good enough for packaging machines
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Post by Roger on May 25, 2015 18:58:09 GMT
I would have thought you would want to put the chamber under pressure rather than a vacuum to force the oil in. We used to soak oillite bushes in oil for 24 hours before fitting them. It was good enough for packaging machines I know it seems counter intuitive but it's what they do with vacuum casting for the same reason. The air has to come out, so the metal has to fill the voids. Pressuring the air in the matrix will only make it want to expand when the pressure is released. I think the density of the sintering is pretty low in Oilite bushes, I would imagine these metal clay parts would end up denser and not as easily impregnated.
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pault
Elder Statesman
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Post by pault on May 25, 2015 19:23:14 GMT
on that principal I would have thought that you would cycle between vacuum and pressure to get the best results
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Post by Roger on May 25, 2015 19:40:52 GMT
on that principal I would have thought that you would cycle between vacuum and pressure to get the best results I really don't know, but vacuum impregnation seems to be a universal principle. They use if when they want to get varnish into motor windings too.
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jem
Elder Statesman
Posts: 1,065
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Post by jem on May 27, 2015 15:43:05 GMT
So why not vacuum the idem in an oil bath, this then gets the air out, and when the vacuum is cut, oil should rush into the voids!
jem
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Post by Roger on May 27, 2015 15:47:52 GMT
So why not vacuum the idem in an oil bath, this then gets the air out, and when the vacuum is cut, oil should rush into the voids! jem That's the usual procedure for vacuum impregnating anything.
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Post by chris vine on May 27, 2015 17:40:38 GMT
I think that if you just stood the porous metal in a thin saucer of oil, that the oil would wick into the spaces. It would gently push the air out as it wicked up. The only thing which would spoil things is if you completely immersed it in the oil, my instinct is that would somehow trap the air in!!
Chris.
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Post by Roger on May 27, 2015 19:38:25 GMT
I think that if you just stood the porous metal in a thin saucer of oil, that the oil would wick into the spaces. It would gently push the air out as it wicked up. The only thing which would spoil things is if you completely immersed it in the oil, my instinct is that would somehow trap the air in!! Chris. That might well work Chris, good thinking. I guess it all depends on how tiny the voids are and how viscous the oil is.
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