Catching the spoil board on fire

[gillian]

I have had a vacumme table for my shopbot for about a year. This month I started to catch the table on fire. We have been cutting puzzle pieces with tight circles but curves also smolder. Why does this happen? How can I stop it?

[rcnewcomb]

Short answer: the feed rate is probably too slow for the bit/material combination which causes excess friction/heating.

What changed this month?
Did you change to a different batch or brand of bits this month?
Did you switch to a different type of material?

Another possibility:
Have you replaced your collet recently? If you haven't then you may need to.

[gillian]

I am using the defalt rates that the bits use in parts wizard. I have replaced the collet recently. What has changed is really tight cutting where the bit seems to sit in the same place while it cuts around a corner. Is ply wood harder than mdf?

[zeykr]

It would probably help folks give you a speed and feed reccomendation if you can tell people what material and thickness you are cutting, what bit size, style, and depth of cut, and what RPM and move speed you are using, and possibly info on what size of pieces you are cutting.

Basically though as Randall says, you're either going to have to move faster or spin slower, probably both.

[rcnewcomb]

quote:What has changed is really tight cutting where the bit seems to sit in the same place while it cuts around a corner.
If you could also post your ramp values that might help. It sounds like it may be slowing down too much on the curves.

Keep us posted. We all learn from this.

[chuckster]

I am a pro at starting my spoilboard on fire. Everyone is correct in their posts. It is ramp speeds, rpm speeds, cut speed, friction. I drill LOTS of holes. Too slow = fire! Be sure to keep a dry fire extinguisher or at least a sqeeze bottle of water handy!