Feed Rate?

[Jjones]

Ok... I hope this is the correct place for this post. I am thinking of purchasing a few of the 1/16 tapered carving bits to run in a commercial CNC machine to do some large scale carving. Can anyone tell me what rpms and feedrate to run at? I have run my Dad's compucarve and I know the guys at Carvewright have the speeds down pat because after 2 hours of carving the bit was just room temperature:D EXACTLY the way it should be. Can anyone shed some light on this subject? Any help would be appreciated,

John Jones

[Jeff_Birt]

I've found that precisebits.com has a lot of good reference information on there website concerning this subject. For example: http://precisebits.com/Reference/precisefedsped.asp

CW had to play it safe since they could not know in advance what type of wood somebody would be running (and we have no control, yet, to adjust feeds and speeds on the CW).

[Jjones]

That information can't be right. I ran the calculations fot he 1/16" bit at .313 deep in Walnut and it came out 24" per minute. When I put that into my software for the part I want to carve it says it will take a VERY long time to carve a part that is 10 7/8" x 18 9/16". What step over does the compucarve use? I thought it was .005 and .010 but at .005 it says it will take 35 HOURS to carve the above piece at that speed? I am so confused! Any information would be appreciated. I figured this job on a few carvings I did on my Dad's Compucarve which took about 1 1/4 hours per square foot to carve. If I have to run it at this speed I am dead! Anybody have any suggestions?

[Jeff_Birt]

If the larger machine doing everything with vector toolpaths it may well take a long time. Not sure what your other machine is or what other softwre you are using to generate tool paths, you can probably speed things up conseiderably by doing a roughing pass first with a larger end mill.

[Jjones]

I am using cut 3d and doing a roughing pass with a 1/2 ball end bit stepping over .125". I also told it to only leave .01 clearance for the 1/16" taper to clean out. After looking at the information that you sent me again I did some checking and found out that the bit they were refering to was a 2 flute bit and the bit I would be ordering from then would be a 4 flute bit. Also I figured that the deepest the bit would be cutting is like 1/16" so basically it should just be skimming the part. Any idea as to what step over the Compucarve is using? Is is .005 and .010? Thanks for the help,

John Jones

[rjustice]

John,
On the speeds and feeds link that you looked at notice that it says MINIMUM.. this is to keep the tool from burning up. If you feed too slowly it doesnt cut, it burnishes, rubs, and simply creates heat. The Compucarve is using a .005 stepover if memory serves me correctly. This is what it uses to do a raster type cut. IMHO the tapered tool is very robust, and you could easily leave more material and it wouldnt hurt anything. As far as the feedrate, depending on your spindle speed, I would start your feedrate at 50ipm and see how it looks.

Hope that helps,

Ron