Specific feed speed rates for specific wood

[mcArch]

I am working on a project where I am carving a relief into a sheet of plywood, they are forms for the sides of some custom concrete blocks. I am trying it with 3/4" pressure treated plywood, it's pine, (the other option is birch veneer which I think has a softer core like poplar or similar). Anyhow, I'm using a 1/2" endmill, 3/8" x&y step, and have tried with a cut pass depth of 1/8" at 20ipm, that smoked the place up. I tried a faster cut speed at like 60ipm with a cut depth of .07", that seemed to work ok while it was doing straight passes, but smoked up the place again when it started to contour into uncut wood. Am I going about this right to just find the right combination of feed & cut depth? The router is a Porter Cable & is a single speed, I think like 11,000rpm (not sure of that, but almost) here's an image of the sheet I'm trying to cut, it's 8' long & about 3' wide & will be cut out of a 4x8' sheet. You may not be able to make out the cut file image, but maybe you can get the idea.

This is something that can be done w/ the router right? I just have to find the right combo of cutting tool, feed & cut depth?

Oh yea, the end mill was a 4 flute solid carbide & I did try a 1/2" carbide straight flute too, same results w/ that. I'm pretty sure that for starters I should try a 2 or 3 flute solid carbide. . . ??

That third image is of the machine cutting a test panel out of EPS (styrofoam).
Thanks in advance for any comments or advice.

--Mike.

[ger21]

If it's a single speed router, it's probably around 23,000 rpm.

The smoke is from feeding way too slow. At that rpm you should be cutting at 200-300 ipm, or even faster with a 4 flute tool. As for depth of cut, cut as deep as you can without stalling the router.

[mcArch]

Thanks Gerry, that was a great help, I figured I just needed to try some diff. feeds, so here's what I've got working pretty well now. I re-shaped the 4 flute end mill to a 2 flute (the ones I ordered are on backorder!) and I'm running at 100ipm cutting .07" pass depth. I could probably run a little deeper passes but the 3/4" pressure treated plywood is not the flattest and I am only using screws at the edges to hold it down, I don't have a vacuum table, so I have to consider that first pass may run a little deeper in some spots.

I'll post a few pics of the cut panel here tomorrow or so when I can get some uploaded. The blocks are turning out pretty sweet, I have a bunch that I cast in styrofoam forms earlier, but the wood form blocks are much sweeter (cast 2 of those so far). I think I may be able to get 120ipm from the machine but that's pushing the limits of the Y axis motor at that point & I don't want to risk losing steps.

Thanks again for the input Gerry.