Rf45 clone glow up.

Kieran wrote:

How's the rigidity of the harmonic drive? 

My 4th axis is based on a 32-size HD reducer, and I've not had any problems with stiffness.  It has a 6" faceplate and is on a 1-1/2 riser, so I can swing approximately 8" diameter parts or stock.  Note that the reducer is mounted in a steel frame/housing - not aluminum - to increase rigidity.

I've never machined 8"dia stock, but I have drilled 3"-4" off the rotary centerline.  1/2" drill in mild steel with no torsional deflection noted - at least not enough to cause the hole to be non-perpendicular or out-of-round.

I expect a 40-series reducer would be fine for a 6" or 8" rotary axis... and perhaps 5hp-10hp spindle class machine?  Like a Tormac 1100/1500, VF-2, or Fadal 3016... but not VF-6 unless you baby the rotary axis.  Probably be fine on any 30-taper machine.

I'm pivoting my design since I just ordered a CSF 45 harmonic drive for the B. The 40 will be the 4th axis on the table. I put a 10ths indicator on the harmonic drive. It has no backlash, which is crazy cool, but does have maybe 0.0001 of "flex" backlash if I put lots of stress on it with a wrench. Seems pretty sweet.

I made some breaker bars out of alu to test it. about .001" springy with as much force as i can comfortably apply. not terrible at all. i had to lightly clamp it since its surprisingly easy to back drive.