Router spindle speedup

For background, here's the CNC router I built. More here

The previous evolution of the spindle involved a timing belt drive, which worked OK, but was a bit inherently noisy and had (due to it being recycled) one pulley bore just a little off center. This resulted in some low (motor RPM) speed vibration that reverberated in the enclosure.

Since Keith did such a good job on the v-pulleys for the X2 conversion, I got him to make up a set for me. I made the decision to go for a bit more speed and changed the drive ratio from 2:1 to 3:1 while we were at it.

I haven't clocked it, but it should be doing something like 9KRPM now.

The improvement in noise was as expected. A little more high frequency noise, a lot less low frequency noise and about 50% louder when cutting metal. Happy with that.

The problem I had now though, was high frequency chatter. The finish on the part was terrible. At first I thought it might be the belt slipping, there isn't much wrap on that little pulley. I tweaked the mount to get some more serious tension but it didn't make a lot of difference. I concluded that the new speed must be exciting some resonant mode in my machine and made up the new spindle nose collar you see in the second pic. Always hated the little one I originally made; too thin and only two slots for the C spanner. The new one weighs about 4 times the old and has two more slots.

Anyhow, this made all the difference. Cuts at 50% more feed rate (600mm/min) now looked really nice. In fact I get reasonable cuts all the way up to 1000mm/min! The extra mass at that speed gyroscopically stabilises the spindle, compensating for the flimsy gantry, bonus!

PK