Thank you in advance for any advice. We are cutting furniture frame parts for a client out of 3/4" plywood and have run into this before. The odd shape of the parts creates a "lingering" of the router in the corners when changing direction and causes heat build up resulting in a smoldering fire in the wood. This fire is not readily visible and, coupled with the air flow from the vacuum, quickly works its way through my spoilboard. This is quite obviously a dangerous situation what with dust collection, etc.

My question is, have others run into this issue and, if so, what steps did you take to alleviate this situation? We are using a 1/4" compression running at 400 inches/min and 16000RPM. This falls in the accepted chip load range. Am I missing something?

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How long does the bit "linger" at that spot? Are you cutting the parts in a single pass, or multiple?

My first thought would be to cut in two or three passes so the bit doesn't get as hot, but with that "sharp" of a point, it may not make a difference...

Dan,

Thanks for the comment. We are currently cutting in a single pass. I am hesitant to continue cutting the material without feedback from the community, but I will certainly change the number of passes. That just makes sense...something I should have thought of! Thanks.

How about pre-drilling those inside corners with the same radius bit? The vertical movement of the bit should keep it from burning. Then the cutting pass won't have any material to clear out.

This may or may not solve the problem. If not then try pre-drilling and then reprogramming the inside corner to cut at about a .03" smaller radius to keep the bit away from the sidewall of the cut.

Just a couple suggestions.

BH Davis

By the look of the rest of the cut, that bit should have been changed a LONG time ago. That's a horrible quality cut, and one pass with a 1/4" bit must really squall. Why the small diameter? Are you required to keep small inside corners? I'm not software whiz, but if it hesitates that long, it needs a tweak in the code.

Rich,

You are correct. The bit is dull and needs changing. This is obviously contributing to the heat issue and is something I will have to be more aware of. The small diameter is due to the programmer (client) trying to maximize pieces to the sheet. I normally cut melamine and use a 1/2" diameter.
I believe if I change from a single pass to two passes and am more alert to bit wear it will greatly reduce the fire risk.
Thank you for your suggestions!

Is the finish important?

It doesn't look like you're using a chip breaker or roughing bit. Either of those would generate less friction.

As far as saving material, my experience is that, other than crazy stuff, material is the least important factor in cost. Plywood is cheap. Halving your cutting speed in order to use a smaller diameter bit in order to save a $25.00 sheet of material is a false economy.

Dropout,

Finish is only important to the point that the edges will need to be cleaner than what you see in the image, for assembly. I don't have much experience in running material other than MDF and Melamine, so I'm naïve to the best tooling. Thanks for the information. I'll be talking to Vortex about that!

on my CNC ( a smaller lower end machine) i cut plywood with 1/4" down spiral at 22000 rpm @ 225 IMP ( this is a 3.25 HP PC router as a spindle). i do it in 2 passes

As long as my bit is not totally gone, i have never seen anything like that. seems like the g-code may be making it hang to long at that spot

Please post the CNC code or file for this program!!!