The chipload data from that source stopped at .125. For tiny tools like .0625 the real limit set by not wanting to break the tool. So I don’t worry about chip load for the tiny tools and just keep the speed at 30 to 40 ips and the DOC to no more than .03. The Dewalt speed can be a little higher but I would never take it over 3.
I don’t remember where I found it, but I’ve always shot for a target of .003-.005" in hardwood and .003-.010" in softwood. After doing feed and speed testing with each bit and wood, I also feel the bit to see if it’s warm. Usually, after 2-3 minutes it’ll be slightly warmer than when it started, which is good. If I burn my fingers, I know I need to either drop the RPM or increase my cut speed.
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Allen
I had some quality time in an airport
so I spun the spreadsheet and added a tab which calculates the optimal feed rate based on drop down inputs for:
- DeWalt Speed
- Number of flutes
- Material type
- Tool Diameter
The file is attached; the work I did is is the tab ‘Feed Rate Calcs’.
CNC Speed Calculator for Dewalt.xls (58.5 KB)
I note that the minimum feedrate I can see is around 65.
What do you think the max feederate of a properly tuned Carve is?
do we have any empirical evidence from existing users what federates they have been able to sustain?
The max possible feed rate depends on what is being cut and the DOC.
I have cut high density foam at 140 ipm with no problem, but I would never try to cut hardwood faster than 90 ipm (with a decent DOC) and that is more than I would normally do, I get the most reliable cuts in hardwood closer to 60 ipm. But that is just my machine.
What shows up immediately when you start looking at the chipload numbers is that the Dewalt min RPM setting is just to damn fast. Your spreadsheet demonstrates that really quickly,
If I tell it I am cutting hardwood at a speed setting of 1 with a quarter inch tool, it is recommending a feed rate of about 300 ipm. The X-Carve can’t even get near that. You really need a spindle that can run at about 8,000 rpm
Thank you kindly for the excellent article Milbot.
I had bought a new automated cnc, and I went through ore than a dozen end mills.
The solid carbide ones would overheat and become dull after a few sheets of materials, and the carbide tipped ones would break.
I kept slowing the feed down, and increasing the spindle speed, but nothing helped.
After reading your article, I realized that I was doing thinks backwards. Using your formula, I slowed my spindle down, and doubled the feed rate.
Now, I am making very nice cuts, and the end mill is not getting hot anymore.
Thanks gain,
Jalal