Milling HDPE

I have been tasked with making some patches for my son’s organization. They want “soft” rubber instead of cloth. I searched around and found a suitable silicone rubber form Smooth-On. Now I need to make a mold. I was considering HDPE, because the release would be much easier than say MDF treated to seal the pores. The patch will be approx 3 in dia, and does have some small detail. The new laser I have would be great, if you could laser MDPE, but no, unless someone has a suggestion for other material.
So my question is what kind of settings speed and feed am I looking for? Most likely will use a 1/16 endmill. Depth of cut is 1 to 1.5 mm deep.

Any input is appreciated

Should be pretty easy to cut. Single flute for sure, at 1mm DOC you should be able to go pretty fast to prevent the melting. I’d say leave a little bit of material all around for a slower finish pass with a low stepover to make it as smooth as possible. That silicone will pick up EVERY detail. Is this thing to be 2.5D or a full on 3D carve?

I made an epoxy mold from silicone using a buck i cut on the cnc a few years ago. Cut it from wood and sealed it with polyurethane. Worked out great, but did require some sanding of the polyurethane a few coats.

Good luck, and please post back how the hdpe turns out.