Strange x axis shift

Hello,

I'm having a rather strange x axis shift that seems to have started out of knowere and is wreaking havoc on many of my prints. Rather than the typical situation which involves a permanent shift due to slipping, overheating, etc., this one seems to correct itself, at least partially. That is, it shifts to one side gradually for a couple of layers, then shifts back gradually until it goes straight for a while. No giant shifts, but overall they make the x axis walls look far worse than the y side, and also cause a problem for any parts that require straight geometry.

Hardware: My printer is a prusa i3 rework with a ramps 1.4/arduino mega combo, running off Marlin firmware from Pronterface.

Wall facing X (left) and Y axis (right) wall of the same print. The y looks much better, though there a couple of blemishes, seemingly about on the same level as the major x defects:


The x motor driver is fairly cool to the touch, so I doubt it's stopping due to heat. I thought the x motors might be underpowered but increasing the current (I haven't gone too far yet), but that doesn't seem to have improved the situation. Belt tension seems ok, though I'll try experimenting with it next (I see no visual or indication or sounds of slipping belts). I don't think uneven z lift is the problem (the distortions would be symmetrical about both x and why, and they are clearly not). Has anyone encountered something like this before? Could frame rigidity possibly be an issue (printer does shake quite a bit during prints)? Thanks in advance.

Edited 2 time(s). Last edit at 04/04/2015 08:44PM by anvoice.

If frame rigidity is worrying you, try a test print at a slower speed to see if the problem goes away.

---

[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Your GT2 belt gears might be too loose and slipping.

Check that the X motor pulley grub screw is tight.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
solomondg
Your GT2 belt gears might be too loose and slipping.

Doubt it, checked and they're quite tight. Besides, that doesn't explain how it returns to the original position.

Quote
dc42
Check that the X motor pulley grub screw is tight.

It is.

Incidentally, I stopped having this problem after wrapping my printer in Saran wrap to act as a makeshift heated chamber. Perhaps it was due to uneven cooling after all. Thanks for the feedback.

This happened to me today. I was using Printrun-win-slic3r-03Feb15 and used the "print speed" setting. I was printing at 158%. That seems to have been the only thing I changed and the only time it has happened to me.

If you're using auto-leveling, and your bed isn't level, then play/hysteresis in the Z axis can cause shifts in the X and/or Y axes.

What happens is that, to compensate for the different heights of the bed at different places, the Z axis needs to move up or down as the head moves in the X or Y axis. Imagine if printing a vertical cylinder... the head should move in a circle at each layer. On one side of the circle, the head is moving upwards, the other side it is moving downwards to compensate for the slope of the bed. At the 'high' side of the circle, the Z changes direction from up to down, and at the 'low' side it changes back again. In these areas, the Z motor will move but the head itself won't move up or down, causing the cylinder to lean.

Just to add another variable to this equation.
Is the head secure in the extruder mount?
My Hexagon was doing this until I put a shim in the mount to stop the movement.

Hello,

I have the same problem using auto bed leveling. Did u find a solution for this?

Ok, it turned out the x-axis slider wasn't sliding smooth enough so very small steps did not do anything. I modified the carriage and lubed the rods and the problem is fixed.

I’m having a similar problem. Can anyone maybe identify the issue with a photo?
For the majority of the print, it was printing out great. Only in the last 3rd or so of the print,
It started shifting and ended up like this.

Quote
He3dsky
I’m having a similar problem. Can anyone maybe identify the issue with a photo?

That is almost certainly skipping steps on one axis. the controller is telling the print head to move, and for whatever reason (usually a mechanical jam) it isn't/can't.|

Is there some unusual noise happening with this?