Problem- Best material for ultrafine detail work?

[MarkU]

I have a Taig DSLS3000 CNC machine, I am looking to use it to machine very fine details into a master for casting silicone rubber. For example, using a 60-degree V-cutter, I want to cut a V-groove with the sharpest possible detail (limited by the cutter, not the material). I would like to keep most defects under ten microns (~0.4 thou), or even one if possible. I realize the precision of the mill is lower than that but smoothness is more important than exact location here.

Since I'm casting silicone from it, any swarf or flakes etc left in the bottom of the groove will mess up the pour and / or tear up the rubber when I pull it out. Polyurethane leaves little slivers sticking out of the bottom, same with brass, the best I've found so far is epoxy but a) I have to clean it up by hand with a syringe needle afterwards to scrape out the compacted powder and b) it's epoxy and I'd prefer not to have that dust floating around, even though I have dust collection.

What is the best material for milling sharp features with minimal / no touch-up required afterwards? Or are there other approaches I should try (a grinding bit in glass or something)? Since it's for casting I don't really care about the other material properties unless it's toxic, too fragile to handle, or likely to catch fire in the mill or something.

Thanks

Mark

[hub]

As hard a material as your mill & cutter can handle.

[awerby]

I use that for masters, if I'm going to be making silicone molds. No problem with sticking, it cuts cleanly, and the chips don't adhere. Also, once you're done you can melt it down into another block and use it again.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[MarkU]

Originally Posted by awerby I use that for masters, if I'm going to be making silicone molds. No problem with sticking, it cuts cleanly, and the chips don't adhere. Also, once you're done you can melt it down into another block and use it again. Andrew Werby ComputerSculpture.com — Home Page for Discount Hardware & Software

Thanks! What brand / type do you use?

[awerby]

because it's cheapest. You can get it from Freeman Supply or Machinablewax.com There's also a green kind that's a little harder, which might be best for more critical applications; I think Freeman sells it too.

You can also mix your own, using paraffin (candle) wax and LDPE (low density polyethylene, the material clear plastic produce bags are made from). Use an electric deep-fat fryer to melt in (the kind with an infinite range control, not just hi med lo ) and about 1 part plastic to 3 parts wax by weight. Melt the wax first, get it really hot (but not smoking) then stir in the plastic. Be careful about emptying the pot when it's hot - the residue will burst into flames. If that happens, have the lid handy to cover the pot with, and try not to set your house on fire...

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[flyinchips]

To minimize the effect of swarf, you might consider a jet of air on the part during cutting to blow the swarf away from the piece and tool. Yes it is messier, but if you really want the best finish, seriously consider this option.