X Carriage Alignment Tool for Geeetech Prusa i3 by DougInAZ

Last crawled date: 3 years, 1 month ago

Update 1/15/18 I added a version that might work better in tight spaces. It should be the same height as the shorter one, but it's always best to print a pair; one of the file here, and the other a mirror of that file.
This Thing includes two nearly identical tools and one that should fit tight spaces better. You use a pair of one of them to set the X carriage perpendicular to the threaded rods, and parallel to the horizontal plane of the printer. One tool grips the smooth rod tighter and may be taller. Since I only used the original, I can't comment on the other two.
I made these tools for a family member, but never used them at the time. I forgot about them until I recently had a reason to readjust my X carriage settings.
There are several steps here. If your printer is/was operating normally, start at step A. If you have removed or are replacing the X carriage, start at D and then restart at A.
A. WHEN THE ALIGNMENT GETS DISTURBED DUE TO A CRASH INTO THE BED OR A STEPPER MOTOR THAT DROPS STEPS.
If the carriage is noticeably no longer parallel to the bed, it is probably best to manually adjust one side to get the carriage reasonably close to parallel to the frame of the printer. With the printer power removed, turn the stepper motor coupler(s) Clockwise (as viewing the front of the stepper) to RAISE the Carriage. Turn Counterclockwise to lower the carriage.
Once it is acceptable, raise the carriage using the computer or firmware adjustment routines to place the alignment tools on the smooth rods. Then lower the carriage so it rests or is close to resting on the tools.
B. FINAL ALIGNMENT OF CARRIAGE
The final step is to adjust each stepper motor shaft to position the X carriage a few thousandths above the stepper motor coupler (the thickness of a piece of printer paper), ensuring that the coupler-spring is not compressed. Probably a good way to do this is to put a piece of paper between the top of the alignment tool and the linear bearing holder. Adjust the stepper motor position manually to lower it down on to paper and stop when the paper is touching the paper, but with minimal pressure. Both sides should get the same treatment, whatever scheme you use. You can raise the carriage using the motors and remove the tools now, or after the next step.
C. PLACING SYNC MARKS ON EACH STEPPER MOTOR COUPLER.
The carriage should now be parallel to the printer frame. The next step will add visual marking to the stepper couplers so that is easy to see if the stepper positions ever get out of sync (and upset the bed leveling).
This amounts to nothing more than a mark in the same position on each stepper motor coupler, see photo. Since the carriage is aligned, you can set it in any position for marking both couplers. Remove the tools if they are still present. FWIW, rather than marking, I like to loosen one coupler and position it so it matches the second one.
As you use the printer, the marks should always remain in the same angular position. There is nothing in the printer design that allows the printer to know if they get out of sync. A bad adjustment on a stepper motor driver potentiometer can cause a stepper to occasionally drop steps. YouTube contains videos on the adjustment procedure. All it takes is a voltmeter, a small screw driver, and maybe three hands.
END OF ADJUSTMENT
D. PROCEDURE FOR CARRIAGE INSTALLATION DURING INITIAL ASSEMBLY OR REASSEMBLY.
I haven't done this, and I'm writing this procedure from memory and recalling how clumsy it was as recommended in the build manual. If some steps don't work, please suggest some changes. I'm not likely to build another.
As you are getting ready to install the X carriage assembly, rather than install the threaded rods into the X carriage, set them aside and insert them later. Assemble the X carriage including the smooth rods. Attach the tools to each smooth rod near the bottom.
With the top plates removed, place the X carriage into position and lower the smooth rods into the hole in the frame, with each side of the X carriage resting on an alignment tool.
Loosely attach the top plates, placing the smooth rod through the hole for the smooth rod. With the top plates installed, the carriage will be stable, resting on the tool, which rests on the frame base.
I'm assuming the stepper motors and couplers are attached prior to the above steps, so now, the bottom coupler should be tightened onto the stepper motor shaft, and the upper coupling should be completely loosened to receive the threaded rod.
One at a time, remove the top plates and thread the rod down through the brass nut until it just enters the coupling but does not bottom out. Replace each top plate. Again, it does not have to be tightened, but the threaded rod should be able to be turned by hand with the top plate in place. If it binds, add a drop of oil.
At this point, the X carriage should be in-place, resting on the tools, with the threaded rod resting slightly above the bottom of the coupling cavity.
The next step is to thread the rods, one at a time, down until they just touch the bottom of the cavity, and before they start to lift the carriage more than a few thousandths off the tools. At this point the top coupling can be tightened, tightly!
There is more to do; the final steps will be accomplished, by restarting at step A.
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INFORMATION YOU CAN LIVE WITHOUT:
When I built my printer, I eventually came to the point where you had to level the bed. At the time I thought that the word level really had nothing to do with what we were doing, but I knew what they meant, and I didn't know a better name for it. What that adjustment does is adjust the printer bed so it is parallel to the X carriage travel (however good or bad that may be). It turns out there is a better word for the procedure and it is TRAMMEL. As a noun, it can be used to refer to a tool for trammeling. As a verb, it refers to making a mechanical alignment or adjustment, which is exactly what carriage/bed leveling is all about. Thanks to GZUMWALT, Thingiverse designer extraordinaire, for introducing me to a new word.