Y axis jumping

[fmcatalan]

Hi. I'm struggling with something very strange. I get an error in my prints where I get a offset in my prints on ly in the Y axis. It looks like a missed step, but I'm fairly sure it's not. It's only on the Y axis. I swapped Drivers, then cables, then motors, with the X axis, so I expected to see the error change directions, but no, it remains in the Y axis. The rods are smooth as silk. I have measured and leveled the frame to the tenth of a mm, the gears and the belts are perfect, they are not elongated or missing a tooth. Is not allways, I can run 25 calibration cubes succesfully, and on a print I can get 90% right, but get a skip on one of the final layers... I slowed the speeds, to a very very bare minimum... nothing seems to correct the problem.
Yesterday I printed a Spool Holder, perfect,

IMG_20190909_104747.jpg (115.63 KiB) Viewed 9090 times

the second one, got a skip on the 20th layer, very little skip, like maybe half a mm,

IMG_20190909_104816.jpg (130.43 KiB) Viewed 9090 times

and then I printed 2 holders at the same time and left them overnight at very low speeds, today I found them with one skip, near the end, but a very big one, like 2 mm and then another one near the top in the opposite direction.

IMG_20190909_104828.jpg (149.14 KiB) Viewed 9090 times

Could it be the GT2560 board?
What else can I try?

[William]

Hi, Regarding layer shifting, you can do the following checks:
1. Check if the belt of each shaft is loose, and adjust it properly;
2. Check whether the bearing and the pulley are issued (the card can be lubricated for lubrication);
3. If the printing speed is too fast, you can make appropriate adjustments.
Reference range 30-60mm / s;
4. Check the voltage of the driver board, whether it is within the range of 0.8-1.2V, and adjust it properly;
Increase clockwise and decrease counterclockwise.
you can refer to this:

A4988 测量位置.jpg (192.77 KiB) Viewed 9077 times

I hope this can help you.