Air cooled motors are better cooled at high rpms. So, what if I want to cut something at low rpms. What rpms are still OK for cooling? Is there any rules of thumb? Like do not go below 8000, or something like that?
Clearly, this will also depend on the load, but still, I need some base line here.
A lot of factors involved, like duration of the cut, depth of pass and step over. You’ll find at low RPM the spindle lacks some torque, so you will have to adjust things accordingly.
You are probably overthinking this, the only way to find out is to do some test cuts.
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Hi Derf, thank you for your comment. Yes, may be I think about it too much, but it is always good to understand what is involved. By the way, I looked at the Redline manual and they claim constant torque over the entire range, 0.47 Nm for the 65 mm spindle and 0.60 Nm for the 80 mm spindle (1.5 kW). How do you see the reduction in torque, you mentioned?
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I can’t speak directly to your question about air-cooling, but when I was setting up my Redline 80mm 1.5kw spindle and running the warm up routine, it was making a godawful screech at 6k which got better at 12k and disappeared at 18k.
Redline support told me that noise will sometimes be experienced below ‘operating’ rpm and was expected behavior of the ceramic bearings. And to be fair, if I ran a second warm up cycle the noise wasn’t present at any RPM.
All this is to say ‘operating’ RPM should be higher than 6000RPM. Anecdotally, if you are running 8K it would seem like that’s within the working rpm envelope of the spindle.
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You will always run a spindle warmup (in the manual) before first using your spindle for the day. This spreads the grease and removes the sound.
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Thank you for the information. That was helpful.
I am curious. Do I really need to warm up the spindle even if I only want to cut something for 10 minutes? Seems excessive to warm something up for 30 minutes to only use it for 10 afterwards.