Cedar Burl Burning when routing.

I have a cedar burl that I would like to carve into using my cnc machine yet it is burning when I attempt to do so. I am using sharp bits, fast feed rate and have tried various spindle speeds to no avail. Even when flattening with my surfacing tool at 150 ipm and only shaving of .001" of material I still get the burning. I was able to sand that off but when I attempt to carve into the wood (even at shallow depths) the burning continues and with carving the sanding is not an option. I have not experienced this on any other wood type that I have carved in the past. Does cedar generally cause this much of an issue? The grain pattern is quite tight and wild if this is a concern.

Thank you for any and all help.

Greg

It almost sounds like the motor is running backwards. Any chance its that simple?

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Originally Posted by Christopher Giles

It almost sounds like the motor is running backwards. Any chance its that simple?

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Really trying to use my ESP but its still fuzzy, its not clear what machine and router/spindle are you using.

I am using a spindle from automation direct. It is an air cooled 2.2 kw off shore brand that has not caused an issues thus far. I have however ordered another of the same in case that is the problem (bearings?) The cnc is a self built Mechmate that has performed very well thus far. I will check the spindle rotation but that has never been changed in the 6 years I have had it and there have never been any performance issues until now.

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Good timing. I just finished a landing net using cedar burl for the handle. No burning issues but is soft and porous. Finish is spray on poly and is the usual deep red/brown color. Pic doesn't show it that well. 1st pic is the remaining hunk and some offcuts. Bandsaw but no rotary tooling. Shaped with rasps and sandpaper, Even tho it's a bit soft I would think a sharp bit wouldn't leave burn marks. High RPMs and low feed rate are all I can come up with.

Not familiar with the capacity of CNCs other than watching sheet goods cut down for cabinets. What type of CNC--how many axis(es?)--would be needed to mill out the curved shape of the handles, or other 3D milling. Retiring soon and I could convince my wife to buy me one just to keep me in the shop and out of the house!!

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Originally Posted by Greg Fairweather

I am using a spindle from automation direct. It is an air cooled 2.2 kw off shore brand that has not caused an issues thus far. I have however ordered another of the same in case that is the problem (bearings?) The cnc is a self built Mechmate that has performed very well thus far. I will check the spindle rotation but that has never been changed in the 6 years I have had it and there have never been any performance issues until now.

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A three phase motor could be running backwards, but you can check that easy enough. Reversing any two output phase leads with the power off of course would correct. I doubt your spindle has bad bearings as the cause. Air cooled spindle should not run below 9,000 rpm because it needs that speed for air cooling the motor. Since the minimum speed is still pretty fast I would experiment with the feed rate or try another bit.

Up-cut or down-cut? Down-cut are prone to burning because they do not evacuate chips from the cut line...'just asking because it's certainly a possibility.

Thanks to all for the assistance. It appears Christopher was correct and that somehow the spindle was turning in the reverse direction. I will have to test later today on the burl but that is certainly a relief.

https://qaf05a.sn.files.1drv.com/y4m...&cropmode=none

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Originally Posted by John C Bush

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Good timing. I just finished a landing net using cedar burl for the handle. No burning issues but is soft and porous. Finish is spray on poly and is the usual deep red/brown color. Pic doesn't show it that well. 1st pic is the remaining hunk and some offcuts. Bandsaw but no rotary tooling. Shaped with rasps and sandpaper, Even tho it's a bit soft I would think a sharp bit wouldn't leave burn marks. High RPMs and low feed rate are all I can come up with.

Not familiar with the capacity of CNCs other than watching sheet goods cut down for cabinets. What type of CNC--how many axis(es?)--would be needed to mill out the curved shape of the handles, or other 3D milling. Retiring soon and I could convince my wife to buy me one just to keep me in the shop and out of the house!!

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John:

That would be a simple cut for a (typical) 3-axis machine.

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Tony