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Feature Request: Physical leveling bed in X axis automatically during Z probing.

Posted by huckl3b3rry 
Placed the same request on GitHub, but didn't know if that was the correct place.Sorry for the poor description, but I'm not sure how to better describe it.

To try to simplify the explanation of the request please imagine a Cartesian printer where the "left" side is the 0 point on the X axis, "right" side is the other end of the X axis; the "front" is the 0 point of the Y axis so "back" is the far end of Y. The "bottom" of the printer is 0 point of the Z axis and "top" is far end of Z. This would be for a Prusa style printer with two steppers for the Z axis, one on the "left" and one on the "right." The Y carriage is the "bed."

Here is a feature request: Because stepper mirroring is now an option I was thinking we could take advantage of this to to adjust the bed level along the X axis during Z probing. Instead of connecting both Z steppers to the same stepper driver we would use the mirroring with two separate drivers. During Z probing the first point would be on the left side of the printer (possibly at the front of the bed) the next point would be on the right. When the second Z probe sample is taken on the right the firmware would know the difference in Z between the two points. The Z stepper on the right could then be independently manipulated without moving the left Z stepper to correct the bed level in this axis. Of course this wouldn't fully level the bed because a difference in Z could still exist in the Y plane, but it would help reduce the amount of compensation the firmware has to perform during the print. The auto leveling could then move on to take the 3rd point at the back of the bed in the middle of the axis. Performing the Z probing a second time may be necessary for another fine adjustment.

I have a related question, I did change my Z steppers to the mirror configuration and it works great except I noticed that seems to skip (on both steppers equally) at very high speeds or acceleration, but speeds that worked OK at in the none mirrored configuration. This was not expected as I would have though that each stepper having it's own driver would improve performance not degrade it. Any idea why?
Re: Feature Request: Physical leveling bed in X axis automatically during Z probing.
April 24, 2014 10:43AM
Ok, will answer here for all places you posed.

No I will not implement it.
1. X-Carriage should be perpendicular to z to reduce friction on the spindle.
2. Complicated to implement and handle and have no printer to test.
3. Would still need to change for different y as you already saw.

Simple solution if it is too much is to modify bed height coarsely and recalibrate.

Regarding your degradation I'm not really sure why that should get worse. One reason might be that now each motor gets more current. Also you might think that is a good thing, it is only good within some limits. Too high current has a negative impact on force transmittable. When you had both on one you got only 50% of the current and as you saw it was better. So try reducing it a bit and check if it gets better. Use a multimeter to measure start position and to make sure you have the same settings on both.

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Thanks for the reply. I was thinking of a times with my printer where over time one of the Z steppers has lost steps and the bed is level but the x axis isn't. To correct then I manipulate the one stepper by hand to correct it. However, your reasons for not implementing make sense. Of course I could also just tune it so it never loses steps. smiling smiley

I will try to tinker with the current and see if that fixes the issue in the Z axis. It's a minor degradation so I'm not too worried about it, but I had only thought of increasing current, not reducing it.

Thanks for the great software. I sent a donation.
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