Severe y shift when printing test cube

[jklier]

I tried my first print today with the test cube file. My y axis is shifting consistently from layer to layer giving the cube a significant slope. My Y stepper voltage is a bit over 1.2v. I've checked the alignment on each side and it's dead on. I can slide the y axis easily with no noticeable binding. It' slightly harder to move than the X axis but I assume that's due to there being two rails and motors rather than one. Any ideas on what to check next?

[Wyvern]

Try removing the back panel and placing a small fan by the steppers, see if that fixes it, if it does, your stepper drivers are overheating.
If it doesn't fix it, try connecting the LCD (assuming you are using the SD card to print) with the short cables and see if that fixes it, if it does you need magnetic choke coils on the two ribbons.

Also what speeds are you printing?

[jklier]

I'm printing with Repetier. Speed is 40mm/s. Overheating could be it. My kit was missing the heatsinks for the stepper drivers. I was told on this forum they weren't needed but I went ahead and ask to have some shipped to me. I've had the case open with a strong fan blowing in. Maybe that's not enough without the heatsinks.

[Wyvern]

IMHO with the weak stepper drivers supplied, you need as much cooling as you can get, the heat sinks on mine got red-hot before I installed a 120mm A/C fan.

I since replaced the ramps with a duet 2- they have no sinks because they are rated for high amps and are soldered to a thick board to dissipate heat- but I still install sinks.

Another idea is to check to see how tight your belts are, and, since you got an extra stepper driver, swap and adjust it with the new one.

[jklier]

I went ahead and re-tightened the belts. They both play the same note when strummed now. I think I'll back off on any more test printing until those heatsinks come in. Will comment back if I'm still having the issue after installing them.

[carefudundae]

does it look anything like this:

I had the same issue that was corrected by slightly increasing the stepper voltage...
also, you need heat sinks on these and ample cooling, so you should still probably wait until you get the heat sinks, but if that doesn't fix it, try tuning the steppers up just a tad.

[jklier]

Yep, that's what it looks like. I tried getting that Y driver a bit higher but when I turned it past a certain position it would drop back down to .4 . I'll see if I can tweak it a bit higher after the heatsinks arrive.

[Wyvern]

With my kit only a couple drivers would go above 1V I had to cherry pick for the Y driver.

Adding a heat sink will not solve that problem, it's a resistor pot problem.

[viol8r67]

I have the same issue, but on the ft-6. It puts down the first layer perfectly and sometimes goes a few layers before shifting. I have checked the voltage, about 1.28, tried to raise it but a slight turn gives me 1.4, and the steppers are cold. X and Z are slightly hot and warm respectfully. I have tightened belts, slowed to 40mm/s and 75mm/s on travel and am trying a print now. Bed is as level as I can get it without a dial gauge to measure it, but as I said, it put down a perfect first layer. I do have a 80mm fan blowing on the drivers. I have also re-tightened all the bolts associated with the direct drive assembly. I have so many issues with this printer it isn’t even funny, like no USB options, filament jumping the spool because of distance, and wish for a cooling fan for the print.

[FRFT]

I struggled with this a few weeks ago too. If you got cooling, emi and voltage set then check the mechanicals of the axis. My Y rails were nasty sticky.
Disconnect the belts from the motors and slide the Y rail around. Is it smooth? Does it bind? Go slow, go fast, go back and forth in several spots. If your rail was rough to begin with it may be sticky now. If you find binding on one end of the motion maybe it us a rail to rail alignment issue? Are the rails coplanar?
If that does not help, diconnect the X cross bar and see if you can isolate which rail is the issue. Then you can try to clean the rail cartridge ir order a new one.

[Wyvern]

If you have a spare printer, print up some linear rail alignment tools. Those are looooong rails and a slight misalignment can cause major issues, just like the z axis.

[jklier]

Update - I got the Y shift issue fixed. Unfortunately I can't say for certain what fixed it. I normally would only try one thing at a time but since I was waiting on the heat sinks to come in I tightened up the belts and re-aligned and squared up the rails. I installed the heat sinks yesterday and it printed a near perfect test cube. I'm about 10 hours into a 11 hour print now and it looks fantastic.

So my issue was related to one of the suggestions in above in case anyone having this problem reads this thread.

Thank you to everyone who replied.