Falling X-Gantry without powered steppers

mbuh

Hey!

I am using the D2Wifi on a CR-10. Since I use both Z-motors independently, my X-gantry falls on the heavy side about 2mm when the power@steppers is switched off. Previously, when the steppers where in series, that didnt happen. Is that due to wrong wiring? I already tried to tighten the pulleys, but without success.

If I use then G32 to adjust the gantry, i must repeat ikt approx 5-6 times until it is leveled. Is that the algorithm, which makes no bigger compensation, or have I sth wrong in the command?

bed.g:
G0 X150 y150 Z5 F360
G30
G30 P0 X20 Y150 Z-99999 ; probe near a leadscrew, half way along Y axis
G30 P1 X280 Y150 Z-99999 S2 ; probe near a leadscrew and calibrate 2 motors
G0 X150 F24000

config.g:
M671 X-27:333 Y150:150 S5 P3 ; leadscrews at left and right of X axis

dc42

Whether or not the gantry falls when you turn off power depends primarily on the detent torque of the motors and the pitch of your leadscrews. So the best fixes are motors with higher detent torque or finer pitch leadscrews.

If the motors do start dropping when power it turned off, there is a small amount of braking force produced by the back emf of the motor. This isn't usually enough to stop the motor dropping, because if it slows down the motor then the braking force reduces too; so it usually just slows down the rate of fall. But in your case I think the detent torque is just high enough to keep the motor stopped if there is some initial braking. When the motors are wired in series, the braking force is greater than when they are wired to individual drivers.

If G32 consistently under-corrects the leadscrew levelling, you can use the M671 F parameter to over-correct deliberately.

A Former User

@mbuh

hardware-possibilites that came to my mind:
(Edit: sorry read it now that you have probs with the x-axis)

get leadscrew nuts that can be preloaded
sync the leadscrews with a belt (with the belt-pulleys loose but in place, then calibrate to plate, then with current on motors tighten the belt-pulleys to have an even sync)

Edit: There are lots of CR10 groups in various forums (facebook, thingiverse, google-groups, etc.) I am sure they also have some good ideas...