Easiest non-porous materials to mill?

[swissmiss]

Hi All, I'm new here (and to CNC) and planning on purchasing a pro machine with 4th axis attachment. I'm looking to get into CNC because I am a maker of silicone molds, and I am looking to expand my capabilities in the silicone mold making world.

I'm trying to figure out what the best materials are for milling that are cheap, clean, accurate, and non porous. I will be making positives and then using liquid silicone to cast molds onto those positives, so they ideally need a smooth surface that I can coat with a thin layer of mold release. I am imagining if I use a wood, the wood would just absorb the mold release for example. I have considered delrin but it is quite pricey especially at the lager sizes I would be looking for. Any thoughts on other options?

Also, I am looking for suggestions for materials that would work well on the 4th axis attachment. I want to find materials that come in standard sizes ideally, so I can easily churn out multiple different designs one after the other.

Help is greatly appreciated!

[Gary Campbell]

Look into machinable wax. Cuts like a dream and you can remelt and reuse both the chips and the plug when done. You can also make your own from parafin and grocery bags.

[swissmiss]

Oh very interesting... Do you know if this material would be brittle with the risk that small details would break off? I want to be able to cast multiple silicone molds on one part.