[dude_chevy]

I have noticed during heavy cuts, my z seams to drop. It's almost like the slack in my Z is sliding down during the cut. My backlash setting is .018" in my Z. With stock screws is there a way to reduce the backlash in Z? Do yall have any other ideas for me?

G0704 using stock screws.
KL-6050 stepper motor drivers
C-10 parrallel break out board
KL 600-48 48VDC/12.5A Switching CNC Power Supply
nema 23 570 oz (KL23H2100-50-8B)

David Branch

[bikedude987]

.018 is pretty bad backlash. What is probably happening is your z is tight enough that the head stays at the 'top' of the backlash after a -Z move then vibrates down to the 'bottom' of the backlash during the cut.

If you can't go to ballscrews I would either preload the head (up or down), preload the lead screw with another nut, adjust the gibs so that the head moves freely enough to stop at the bottom or tight enough to stay at the top.

backlash comp doesn't happen until the motor reverses direction, so it's doing nothing for you here.

[dude_chevy]

Dose anyone know what size the thread is on the z leadscrew?

David

[LeeWay]

Just an opinion here, but using double nuts on the original screw would probably be a waste of money.
The Z axis is the most used way on a mill. It typically has the most weight and cutting forces applied. If you put any money at all in it over the stock system, your money is probably better spent with an upgraded screw.
It's not only the cost of the nut you are looking at, but also the time and extra effort needed to tear it all down and then figure out how to get the second nut installed on the original screw so that it would act like a typical spring loaded anti backlash nut.

This is without my knowing what material and type or size your original nut is. I have a larger HF round column geared head mill and it has very poor split cast brass nuts. Un-useful for anything but manual milling. Check out Hoss's thread to see what he used. Might give you some good insight.