Yesterday I went to Home Depot and sorter through their 1/2” steel shafts looking for a straight one bu rolling then against each other and looking for gaps as they turned, indicating a crooked one. Found two bought one.
Dissembled the Z axis removing the stepper, it’s mounting plate, and flange bearing. Unbolted the anti backlash nut Backed the acme thread out.
Made an aluminum piece and put it in the hole where the AB nut was. Out the shaft down from the top through the aluminum piece and into the bottom bearing.
Put the flange bearing back on, the flange bearing turned easily and smoothly by hand and at speed). Th three points of contact were in line the shaft could be rotated and raised and lowered smoothly with and friction or binding. So far everything looks good.
I wanted to simulate the stepper like I did the AB nut, so I took some 1/2” aluminum plate and laid out and drilled the stepper bolt pattern and made a 1/2” hole in the center where the 1/2” rod would go through and bolted them together, then bolted the the stepper plate together with the plate I made back to the top of the Z assembly.
Put the test rod down through the above assembly, and it wouldn’t go through the flange bearing 2” below it. Removed the test rod and unbolted the stepper plate with the plate I made still attached, and just let that assembly sit on top of the Z assembly without and bolts.
Slid the rod through the assembly and moved the assembly around until the rod went through the flange bearing, the AB aluminum part I made and into the bottom bearing. Continued to move the assembly around until the test rod could be lifted and lowered without any drag. There is was The plate that the stepper mounts to was 0.100” off in the minus Y direction, the X direction was right on.
How did it happen, drilling and tapping the holes in the Z stepper mounting plate in the wrong location, most likely a mental error in simple math.
The flange bearing has mounting holes that were made for 5/16” or 3/8” bolts, and I used 1/4” button head Allen screws with a larger washer, thinking that extra clearance would allow for alignment.
A couple of weeks ago I had the Z axis out to machine flats on it. And had the flange bearing out and removed the Z stepper and it’s mounting plate as a unit. When reassembled I left the flange bearing loose so things would self align. Put the Z stepper stepper and it’s mounting plate on as a unit then tightened the flange bearing. The spring coupler is made of steel and has two spring sections and a solid harrow section in the center this makes it quite flexible, but still rigid enough to cause the stepper to work harder, I think I got it more misaligned after that teardown than it was before.
The problem, misalignment of the X mounting plate causing more load on the stepper, and loosing steps. And that one start acme screw had to spin a lot more than a five start I will shortly have.
My five start parts will be here soon, and I’ll just elongate the mounting holes on the Z plate when I assemble the five start parts, then cut a new Z axis mounting plate, and I’ll be doing all math using a pencil and paper.
Thank you all in sticking to this “Mystery Saga”. I’ll let you know how the story ends in hopefully a few days.