Full Version: Failed Experiment with PMC
From: nick (STUDIO-N) [#1]
6 Nov 2005
To: ALL
Howdy All,
you can learn a lot from a failed experiment so here are the results from my recent one:
First a little background on what Precious Metal Clay is: PMC is basically microscopic Silver (or gold) particles suspended in an organic binder and water. You work it like clay to the shape, including piercings and cuts, that you want and then let it dry. The dry clay looks like ceramic bisque. You then fire the clay at 1100 degrees and the binder will burn off leaving a silver piece of 99.9% silver. It is a quick, though not cheap, method of prototyping without doing metalsmithing or for doing 1 piece.
So anyway, I got the idea that if the clay could be engraved, then a great amount of deatil could be put into these silver pieces. So I got the PMC and laid out 3 one inch squares about 3/32" high and let them dry. I laid out several squares on the PMC at various power levels and speed and passes. This is for my ULS 45 watt M300.
I eventually was down to full power (45 watt) and 2% speed with 5 passes over the same area. Bottom line - DIDN'T EVEN SCRATCH THE SURFACE! Never mind trying to cut through.
In examining the PMC square I could feel that the silver was retaining heat. Not enough to burn, but hot enough. A secondary result was that the PMC square began to warp. It did not seem to reflect the laser, only aborb it. It may be that there was enough heat that the silver began to 'fire'. This might account for the warping since PMC shrinks when fired and the shrinking may have cause the warping.
Well anyway, I consider the experiment dead but it give me an opportunity to try something new. remember, if you're not failing (or succeeding even), you probably aren't doing anything. Just sharing an experience. peace.
Nick S.
From: Rodney Gold (RODNEY_GOLD) [#2]
6 Nov 2005
To: nick (STUDIO-N) [#1] 9 Nov 2005
You can do this with a laser without using that stuff , essentially you make a master out of anything that can be engraved and withstand either Room temeperature vulcanising rubber or Spin casting rubber that is vulcanised with heat. For spin casting , pex is fine , the master gets destroyed and the mould is perfect , the item can then be spun cast in low melting point stuff like tin , pewter , zinc based casting metal etc.
For the other process (lost wax) , you can use ANYTHING that engraves well and then make a mould in a rubber that cures at room temp , VERY easy to do. You then use the rubber mould to cast multiple wax items and you put these wax items on a sort of tree and cast plaster of paris around them , the plaster of paris or investment material is then put in a furnace that melts all the wax which comes out the trunk of the tree , the empty cavity is now filled with molten precious metal and when cooled , you break away the plaster of paris and you have a metal tree with the items you can pick off.
I do 100's of masters for the spin casting industry in perspex.