Working on uploading a video but the short of it is that the y axis “sticks”; i.e. the computer commands 10 steps but the motor only moves 5.
I have cleaned the rails and bearings. Checked that the bolts are tight attaching the stepper to the toothed gear (one was not!). Lubricated the rails with silicone spray on a rag (seemed to help).
Any other suggestions?
Thanks!
Andrew
While you’re waiting for more responses, please collect and provide more data.
What if you command 20mm…does it move 10, or 15?
Does it behave the same when moving +20 as compared to -20?
What if you remove the belts and just count stepper rotations? (put a piece of tape on the pulley face like a clock hand and watch the movement)
And, the obligitory:
What board are you using?
Series stepper wiring, or dual-endstop?
Also (and probably most importantly) is this a new build that has never worked right, or is did something change to upset a system that worked previously?
Is it moving freely or do you need to push hard to get it to move?
Thanks for the replies!
Gene,
Movement in the +Y direction is the problem. Regardless of the x position.
It is purely a mechanical issue.
I am using dual end stops (although I am pretty positive I have never set them up correctly as the machine has never gone to full + to find the end stops there.
I am using the Rambo 1.4
It was working before, but this is the first time moving to this extent in the Y direction.
Also I am not super happy with how “jerky” the motion is.
UndCon,
A gentle push is often all that is required to help it along with a commanded +Y move.
Thanks for the replies! Hopefully we can figure this out!
Andrew
OK, I’m not used to Rambo but are your voltage set correct on the drivers?
My idea of testing smoothness is how easy it is to push around before belts are attached?
Mine moves fairly easy, but I think it will soften up a bit more when/if bearings are worn in
(all brand new Chinese poop quality) and I haven’t even lubricated anything yet.
I would suggest beginning by removing the belts and verifying that you can manual move the carriage in both X and Y without any binding or sticking. If you’re binding up mechanically, that will need to be resolved first.
Assuming you can move easily without the belts. Before reattaching the belts, verify that your toothed-pulleys are tightly attached to the motor shafts. Try holding the pulley in place (with your hand) and send a command to move the gantry (in X or Y) to have the motor try to spin the pulley. The motor may skip (miss steps) or the pulley may turn in your fingers, but verify that the motor does not spin the shaft while the pulley remains still. Test all 4 pulleys this way.
Note - if the motors skip (miss steps) while you’re holding the pulley - this may be an indication of not enough current driving the motor. Or it may be an indication that you have very strong fingers. 
Assuming your pulleys are tight. Reattach the belts and try small movements in X and Y. Do they work or exhibit the same symptoms you saw before? If small movements work, try longer movements.
Report back on your results… Good luck!
Regarding the above statement. I’m pretty certain that in this context “dual end stops” usually refers to having an Xmin (or Ymin) end stop for BOTH X (or Y) motors. Not having min and max endstops on each axis.
Progress! (?)
The carriage jumps in the x direction once the carriage has moved to the problem y area.
Holy cow that doesn’t even made sense to me.
Carriage starts at ~+10" in moving to +11" the carriage jumps ~.125" in the -X direction.
It is almost like the tube(s) are warped.
Does that make sense?
I am going to drag the machine to the center of the shop so I can get around all four sides more easily.
Thanks for the clarification on the dual end stop. That makes me feel better.
Will keep you all posted on results!
Andrew
Posting photos of the build, the controller and wiring can sometimes help us skip a lot of questions. We’ve seen a lot of machines…
On a rambo, the current is set by the firmware.
A problem identified recently (on someone else’s build) was having the motors wired for the “dual endstop” configuration (separate drivers for each of the X and Y motors), but running the “standard” firmware which was only driving one of the motors on each axis. Running through the procedure I mentioned above, could eliminate this scenario…
Jeff is right though – there are a bunch of folks on here that can notice the weirdest issues, just from a few good pictures. Post some.
Good luck!
HOLY COW what a couple days!
Here is a video of me pushing the carriage. https://youtu.be/eAdWszHV9qI
Notice the clicking at the back of the range.
Thoughts?
Andrew
Here is a video of it sticking under its own power
So, it pauses/sticks at the same place every time under its’ own power, but when you power everything off, you don’t feel any hesitation at that same spot?
Have you verified that the rails are parallel? Also make sure they haven’t gotten bent.
I can feel the hesitation with power off and belts disconnected.
I am satisfied that the rails are still straight. I will measure for parallel shortly.
Upon further checking I found the left lower carriage wants to twist.
Will check parallel and get a video of the twist
Thanks again ya’ll!
Andrew
WOW! Despite all my careful measurements the frame was 3/16 wider in the back than the front!
Sounds like a tomorrow project…
Glad to hear you have found a lead. Let us know how it turns out.
I hope you get it sorted. If tubes are not parallel it will jam up at some point.
Well…
Morning ya’ll!
Squared up the tubes…
No change
Rotated the tubes…
slightly better
Loosened the big center bolt on the gantry…
slightly better
Overall… no change.
In really poking at everything I found the outer carriage bearings are not evenly loaded.
Suggestions there?
From the description in your video I’m wondering if you’ve tweaked (and over constrained) some of the parts while assembling? Perhaps try loosening all of the assemblies just a bit, letting everything ‘relax’, then re-secure/re-tighten it back up?
In case that doesn’t make sense (which it wouldn’t surprise me!) I guess I’m suggesting loosening the bits that hold all your tubes in place (leg pieces and carriage pieces), let the the tubes reposition themselves, then retighten.
From the video, if both outer bearings are very tight, that would seem to indicate that the two carriage bits are too close together - loosening their attachement to the top tube should allow them to relax and result in better bearing loading (I would think)…
Agree, you could see an improvement by loosening and tightening again, in particular if the outside bearing is more loaded than the inside, then it suggests that gantry rail is under tension. Loosen the motor plate from the roller to release the grip on the gantry rail, and you should find the inside and outside are mostly balanced and ideally not squeezing very hard – just enough to keep the bearings in contact. (If necessary, loosen the bolts holding the bearings that the belt rides on, so it squeezes the side rail less.) Then re-tighten the motor plate onto the roller.