New 8mm Lead Screws not keeping x axis level

Hey all.
I did a Prusa i3 x axis carriage hack on my MendelMax 1.5 printer and the lead screws seem to no want to keep the 10mm rods level. The Lead screws are plumb(level),The 10mm z axis vertical rods are plumb(level). For the life of me I can hold one coupler still to move the other up and down but then once I start moving the z axis to set the stop, goes back to out of level. I don't have crazy tension on the x belt tensioner and everything is running smooth as can be. Sure I can bring the heat bed up on the one side but not what I want to do. Do the brass nuts on the lead screws always have slop in them? I had a different setup with the MM 1.5 and first time for me using the brass nuts. Any help or direction would be so helpful to me... Thanks!!!!

Without more description, it sounds like two possible problems- the screws are getting out of sync or you have backlash, possibly both.

If the screws are getting out of sync, one motor is slipping (electrically), or the screw on that motor is slipping(mechanically). Check the mechanicals and if they look right, start looking at the wiring to the motor. Are both motors driven by the same driver? Are they in parallel or series? Check motor current. The ultimate fix is to belt drive the two screws using a single motor. They can never get out of sync that way, keeping the X axis aligned. You may still have backlash problems even if you do this.

It is normal for there to be some slop in the nut that rides on the lead screw. If the mechanism is set up so the Z rails are truly parallel, nothing will bind and the nuts will rest against the screw threads because of the weight of the X axis. If things aren't aligned so well, when you move the X axis downward you may have some backlash in one or both of the lead screws. There are two fixes- align things properly and/or use antibacklash nuts on the lead screws. Aligning things properly is always a good idea.

My machine uses plain plastic (delrin?) nuts on the Z axis acme screws. The screws are belted to a single motor and since I aligned the X axis, I have never had to touch it again. Gravity prevents backlash in the Z axis.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I've been tweaking different sections of my printer and found my left vertical 10mm was out about a smidge and I had a low corner on my heat bed. Think I solved that just need to get my need settings dialed in so my prints aren't stringy. I've had the MM 1.5 running about 3 yrs and decided to mess with it. Back to the beginning I guess.

So I found so great info and changed some things in my Marin code that really kicked this thing into a better place. Skipping Steps.... feedrate, acceleration, retraction. All were from my old setup with 1/4" lead screws and now with the 8mm ones it was just hopping up. On my way to better things!

Edited 3 time(s). Last edit at 02/14/2016 10:46AM by grtbaldini.