First time cutting plywood using foam board as support, and it burns, melts, and produces enough smoke that I have to open the garage to ventilate it after every cut. There is no damage to plywood, but burning foam does not support the cut, thus leading to chip out. Here is the example of what it does:
The foam board is a major brand pink insulation from a big box shop. That seems to be the kind that I see being recommended for that purpose, but it appears to be a softer foam than the one it should be, the harder styrofoam-like substance (For instance, Kreg talks about rigid foam insulation). What chemical compounds should I get for this application, and what should I avoid?
I use 4600 rpm worm-drive Skilsaw with the track sled attached and thin kerf 40-tooth blade, so it shouldn't be an issue.
Best Answer
Never tried this, honestly don't see a point in doing it this way (expensive material, and yes, foam melts.)
Ignoring the option of using a blade that causes less problems, a supporting material that costs less and does not melt would be appropriate. OSB, or MDF for two, or hardboard, for another. Hardboard being the generic term for Masonite® which you might or might not know it better as. And I do recall mention of using it for exactly this purpose on difficult materials in some old woodworking text.
However, as a rule the combination of the correct (and sharp) blade and the correct depth of cut for that blade (so it's cutting into the surface, not stripping it off - this problem is usually associated with inadequate tooth projection from the cut material - the entire tooth down to the gullet should be sticking out below the sheet) are a more common solution that does not require a bunch of sacrificial backing material. A dull blade will tend to beat the wood more than it cuts it and aggravate this problem.