[tshawkins]

Some high end cnc lathes use a technique called "Spindle Speed Variation", once turned on it continiously varies the speed of the spindle up and down (example:+-50rpm) over a fixed period, say 2 seconds. The theory is that it prevents harmonic vibrations building up between the tool and the material which extends tool life, reduces chatter and improves surface finish.

What is the general opinion on wether this would be of benifit on a milling machine as opposed to a lathe. Im working on an extension of the popular grbl firmware, where we have added an internal tachometer and adding this capabulity given the firmwear is now aware of the actual spindle rpm would be relativly simple.

Thoughrs?

[Jim Dawson]

I have done this on a CNC mill by manually adjusting the VFD while cutting and it seems to help control chatter under some conditions. Might be worth a try.