[Spinnetti]

Tried a cut today that the machine could not quite handle. .5" 2 flute coated carbide .8 DOC tapered cut with max radial engagement of .175 in 6061, 5100RPM and 25ipm. Didn't seem like that big a cut, and the spindle slowed down at the deepest part of the radial cut. The part came out fine, and I'll adjust the speed down to get the torque up, but just curious if the feed rate automatically slows as the spindle slows? Also, is that a big cut? its a tapered cut from .050 radial doc to .175 over 4" or so, and didn't seem like that big a cut.

[SCzEngrgGroup]

Do you mean *radial* engagement, rather than axial? Otherwise, your numbers don't make sense, as you say 0.8 DOC, then axial engagement of 0.175. Which one is it?

Assuming 0.8" DOC, radial engagement going from 0.05" at the end of the tool, to 0.175" 0.8" up the tool at 25 IPM, that's an MRR of about 6.75, which is WAY more than any 1.5HP machine should be expected to do - by almost 2X. You're lucky you didn't break the tool.

And, no, the feed is NOT reduced just because the spindle slows down. It will try to maintain the programmed RPM and feedrate, and has no way of knowing if EITHER has dropped due to excessive load. You need to program RPM and feeds and DOCs/WOCs that the machine is capable of performing.

Regards,
Ray L.

[nitewatchman]

Trust me on this -- it most assuredly does not.

We run a part that uses a 5/8" long end mill to counterbore for a 2-1/2" shoulder bolt. The cutter cuts through a 7/16" thick web, rapids down through air for 1-3/4" and then counterbores 1/2" deep. The Horsepower meter is a must here. If the cutter dulls and the torque started to climb, it will run in the yellow and kick into the red but it won't run in the red for more than a few seconds. Spindle stalls, feed keeps pumping and you start loosing steps in a VERY LOUD and irritating fashion. Sounds like you just stripped second out of the transmission on the Ford. Cutter don't like it much either.


nitewatchman

[quapman]

I think one of the newer Tormach upgrades is automatic feed reduction with high spindle load. They have a fancy term that evades me right now. Once I get my 1100 up and running, I'll be able to give better details.

[Spinnetti]

K, thanks.. just wanted to know if it would compensate. I do have the load meter, but my eyes were glued to the part (its got a bunch of ops)... It just slowed down some, but the cut quality was unchanged. I adjusted feed/speed down a bit and it should be fine. I bought good quality coated carbide cutters and wow, do they cut better than plain HSS ones!.

(fixed first post)

[BAMCNC.COM]

I have a new Tormach, I haven't seen anything about the spindle load meter doing anything but showing me an analog value of colors. I have a video on YouTube showing what a Tormach can do happily, but it would never do it at that spindle RPM, that is your first problem. NYCCNC and I had a little competition.

https://www.youtube.com/watch?v=diyCUSwO-lw

[rlockwood]

There are systems to do as you describe, but they typically suck. You might start losing steps, but otherwise your axis motors are doing everything they possibly can to maintain the desired position regardless (or in spite) of what the spindle is capable of..

[Spinnetti]

I finished my part tonight.. came out fine. I'll slow things down a bit when using the .5" cutter....

[BAMCNC.COM]

Nah, just add more flutes!