dovetail mill column vs spindle servo

[cncJerry]

I have a new Grizzly G0519 (R45 type) mill and I have ordered 1100 oz/in servo's and gecko drives to convert it to cnc. I plan to drive the screws with a 3:1 reduction timing belt and pulley train. should have enough torque.

I had originally planned to put the Z axis on the quill and then after reading how others did it, I changed my mind to putting it on the column leadscrew.

I am now leaning back to the quill. The headstock on this thing weighs in at over 200lbs and adding the dovetail friction, it just seems like a lot of effort to get reliable action on the leadscrew. Counterweights and gas shocks are a lot of work and have their own pro's and con's. I plan to put ballscrews on it which seem like a great price-performer but might do it after I get the motors all running.

Anyway, the quill on the G0519 has 5" of travel and doesn't seem to have much backlash though there is no adjustment that I am aware of.

Most of the machining I have been doing on my other CNC mill fits easily in the "cutting" envelope of 5" of Z. Also, most drills aren't that long and I have yet to see an endmill with that LOC. Setting aside ever rotating the head for horizontal face-milling, the only advantage to me of putting it on the Z leadscrew would be not having to crank the head up and down but I have an adapter for my VSR drill that works great.

So, what do you guys think? Put the ball screws on right away and do the leadscrew? Stick with the easier quill?

thanks

Jerry

[BobWarfield]

Most of the R45 conversions I have seen (like the Industrial Hobbies) motorize the column rather than the quill. Check the accuracy of your quill. Most of the square columns have pretty poor quill accuracy. Also, the rigidity of the mill will be less with the quill extended.

With your big steppers, I would think you can successfully drive a 200lb head. It isn't that hard to rig up a counterweight system to make it work even better.

Well adjusted gibs and lube are also important to smooth operation.

Best,

BW