Using a recently assembled rostock max v2, assembled to the guidelines in the assembly manual v2, and then following the v3 manual(mine has the older melamine carriages and non-ball arms). Repetier firmware, the only variables I changed were jerk to 30 and acceleration to 1600(unlikely to be factors).
There are two separate symptoms which I have which might be related.
The first is that sometimes, when I use the "pause" function on the LCD menu, the printer tries to raise the carriages/arms but before reaching the end stops the machine starts to grind quite loudly. I suspect one of the belt or belts might be grinding against the drive gear(s) making a loud grating noise.
I tried manually pressing the end stop but the grinding didn't stop immediately.
It stopped grinding on its own after a few seconds.
At this point, any attempts to "resume" the print result in the platform staying at the same height, moving around and extruding filament some 25cm or so above the print(the Z height is completely thrown off).
This only has happened during the pause function on the LCD, not on any other Z movement(maybe the pause function movement somehow clashes with the printers current movement, or it uses a much higher speed/acceleration than other z moves?), and has happened a handful of times.
I tightened the belts' tension but it still seems to happen, albeit not all the time. Now I try not to use the pause function since it might cause print failure.
The second problem is with layer shifting. I have encountered a persistent problem where in the middle of larger prints(10+ hours) the layer would shift noticeably to the left by about 0.5mm and also slightly toward the front of the printer(facing the printer from the LCD side).
In such taller prints, sometimes the first few levels would be very straight and well aligned, and then there might be slight perturbations perpendicular to the direction of the Z-axis, going upward, increasing in frequency the higher the print goes. Then eventually there might be a part where the print head shifts to the left.
It doesn't happened with shorter prints(<2cm), and it seems the layer perturbations set in more the higher a print goes. After a while, a major leftward and frontward shift happens.
Sometimes, the print head would seemingly overcompensate, and a couple of layers later, it would bounce back to the right and to the back. This would often be severe and sharp, exceeding the original shift. This bounce back resulted in one shift of over 1.1mm to the right.
However, I have also printed a tall print which had no layer shift issues.
After the first two layer shifted prints, I tried tightening the belt tensioners and this did no seem to resolve the major layer shifting (0.4mm). While it does seem to get rid of the smaller perturbations, the larger layer shifts still happened. The reason I believe this problem and the pause problem might be related is because I had one of these pause-grind events just before attempting a the 3rd print where the layer shift happened again.
I found a couple of other threads describing layer shifts here:
http://forum.seemecnc.com/viewtopic.php ... 63&p=82222" onclick="window.open(this.href);return false;
http://forum.seemecnc.com/viewtopic.php ... 17&p=82597" onclick="window.open(this.href);return false;
If I do have to take out the stepper motors, grub nuts, belts, arms, etc for inspection, is there a good way to go about doing this without removing the towers/base, cutting wiring, etc? Right now, to my mind, there are a lot of things that could have gone wrong, but I don't know a good process to rule out possible causes. I don't want to rush headlong into disassembling and maybe cause more problems.
I have attached a couple of photos of the various layer shifting/perturbations.
