Homing causing drifting?
I’m having an issue where homing the printer causes the opposite axes to get offset. The offset gets worse after each homing. Including both independent x, y homing as well as the home all function, it creates an offset.
For example, after the printer homes x and attempts to return position, it offsets in the y direction. Similarly, after homing in y, and it returns to the centered position, it gets offset in x.
Is this because of uneven belt tension?
Any suggestions on how to home to center and not create offsets? (Essentially there is drifting when homing)
21 Replies
Sensorless homing?
Even when running the command for setting center kinematic position, we see this drifting when adjusting any axis position like moving any amount x automatically moves y (ranging from slightly to a lot)
@miklschmidt Does sensorless homing isolate the axes better? Not sure if it’s a config settings microstep issue, or a belt tension mismatch but tried both of those.
No, worse. If tuned poorly it can lead to what you're describing when it's supposed to trigger.
That sounds like loose pulley(s).
Alternatively bad motor wiring (but that would be associated with awful wrong sounding noise when moving).
@miklschmidt What’s the best way to tighten loose pulleys? Motor wiring seems fine, there are no awful noises. We noticed that adjusting the x stepper to 49 and y stepper to 52 lead to repeatable centering for y but offset centering for x. It still makes a slightly less offset movement for the other axes but still creates an offset drift when moving either axis to the other axis.
@miklschmidt What’s the best way to tighten loose pulleys?by screwing down the grub screws...
We noticed that adjusting the x stepper to 49 and y stepper to 52 lead to repeatable centering for y but offset centering forAdjusting what?
Are these the grub screws? (One on each side?)
And that was for adjusting the belt teeth (default was 40 for a 20 tooth belt for both x and y stepper motors)
Those are not pulleys. Those are belt tensioners.
You're talking about rotation distance. 20 tooth pulleys with a belt wiht 2mm belt pitch = 40. do not change this, this is a value determined by hardware specs.
Oh ok I’ll put those back
But are those the grub screws?
No. You're not even looking at the correct part.
The pulleys are located on the shafts of your X and Y motors
Those are the ones that drive your belts.
If those are loose, your positioning is effed
They don’t seem like they’re loose (belt is pretty snappy), but you recommend disassembling the x and y motor assemblies to tighten the pulleys more?
Belt tightness have nothing to do with it.
Do not disassemble anything, there are windows in the motor cages where you can reach in and screw down the 2 grub screws on the pulley.
So tighten this set screw?
Or this one on the front side?
The set screws holding the motor drive in place are tight and do not move
yes. Not just that one, there are 2 on each pulley - one of them should be orthogonal to the D-flat on the motor shaft.
No that's not a grub screw, it also has nothing to do with the pulleys
This is all in the build guide btw: https://ratrig.dozuki.com/Guide/05.+CoreXY+Motor+Assemblies/138#s935
Rat Rig
05. CoreXY Motor Assemblies
Thanks for pointing this out I was able to determine that it was the idlers that were installed upside down causing the belt not to catch on the left side. ✅
The picture on the guide was shown as the same on both sides so I was misled in the installation. If the left and right side pictures were shown correctly I would have installed it correctly