Quill Control

Rick,

Didn't you put a stepper on the knee as well?

JT

John,

Yes I put a stepper with a 10 to 1 gearbox on the knee using the stock setup.
I only use the W (knee) for positioning work so the slow speed is not a problem and with the mass backlash is not an issue.

Rick G

Hmm... I was thinking of having an air power cylinder that is constantly trying to pull the quill up. Then have the motor driving it direct drive or pulley. I would think that would eliminate the backlash? The motor would then always be working against that tension.

?

BigJohnT wrote: Is a SuperMax similar to a Bridgeport Series 1 mill?

Yes, pretty much.

This is the only photo I have with the lid off the BP Z axis.



The block with the pointer attached to it is attached to the quill and the ball screw.

JT

Hi

I too have a knee mill with a ballscrew quill.

The knee is manual and I just move the bed up and down to account for the size of the workpiece and roughly touch off to the cutter.
All the fine adjustment and cutter movement throughout the program is done via the Z axis ball screw and it is very accurate.

One method of retrofit I have seen (which is sometimes also used in purpose built machines built upon an existing manual one) is to mount the stepper and ballscrew on the side of the spindle head.
The quill is held in a heavy clamping plate, which is drawn up and down by the stepper actuated ballscrew.

Retrofitting using the existing gears acting on the rack gear cut into the back of the spindle tube was quite common for the RF40 RF30 type of manual mill, but was never very satisfactory because of the
inherant slop which was impossible to eliminate.
The biggest single difference I noticed when I moved from a RF40 manual mill to a CNC one with ballscrew Z axis, was an accuracy of depth of cut I could never previously achieve

regards