[DBMacKay]

Hi All,

I am trying to find a suitable material to machine silicone molds out of. The material has to have pretty good density as well as carving characteristics as I need to carve fairly fine detail in the positive. I have been looking about for such a product and the best I have found is High Density Urethane that comes in a couple of brand names such as Sigh Board (sign industry) or Modelling Board (auto industry). I am living in AB (Edmonton area) and so far have been unable to find any retailers for this product. So the million dollar question is does any have any idea where I might acquire such material? I was considering using Delrin but it is pretty pricey for a toss away mold and I am not sure if it would work in the first place. I tried UDPE but the results were less than sterling for the detail although it cut rather nicely.

Short of finding a source of HDU does anyone have any suggestions as to what I might use and where to locate it?

Thanks,

Dan

[bhurts]

Hdpe cuts very well and takes good detail. It's big drawback is it is more prone to warping. Depending on what your molding its probably worth a try. Uhmw is another one you might also want to try. I actually make molds for casting and don't use silicone at all unless the part has undercuts that have to be molded. I machine my molds directly from polypropylene. The drawback for polypropylene is it melts if not machined correctly. Usually when I'm done machining the mold there's a fuzz on the cut areas that seems impossible to remove. The good news is the first pour once removed actually cleans all that off the mold for me. Good luck. Hth

Ben

[awerby]

High density urethane is at least as expensive as Delrin. It's big advantage is the fact that it cuts better, without leaving feathers or toolmarks, and it sands well. Sign board is actually a medium-density urethane; for mold masters you want a much higher density, so you get a part without visible pores. One I've used for this is called "butterboard". I'm not sure about Canadian sources, but try here: High Density Urethane - High Temp - Precision Board Plus HDU ; https://www.goldenwestmfg.com/foam-board.html