So I'm first going to cover the problem. Then what I've tried. Any suggestions besides what I've tried are welcome.
Basically my rigidbot normal is experiencing Y shift backwards. The problem appears to happen at similar points sometimes but in my most recent testing got a lot worse with the machine constantly printing. As in I printed something and it got probably 40 layers high then started shifting.. Tried it again and immediate shifting. When I first observed the problem it only happened once on a large print. Then it became a more frequent problem.
Here's everything I've looked in to:
-There is no belt slip or pulley slip on the shaft of the Y stepper motor. I drew sharpie marks and have printed a good 20 hours with the problem and they still line up perfect.
-I have checked bed levelness. If anything it's a little low so I don't think the nozzle is dragging on the print material. I also have slic3r configured to retract on movements.
-I have tried rotating my prints and changing common settings but am still experiencing the shift.
-I tried a new mainboard from Rigidbot to confirm it wasn't a failing stepper chip. Both react the same.
-I tried lowering stepper amperage slightly but this didn't seem to have an effect.
-I moved the mainboard away from the printer with a 120mm fan blowing on it to keep it cool so I've ruled out the stepper chips being too hot.
-After a good 5 hours of printing I checked the Y motor with an infrared temp gun and it said 120F on the hottest part.
-I've tried new filament.
I think that's about it. Keep in mind it was printing fine for a couple months.
Also I have noticed my printer seems to have more vibrational noise with the bed moving. Maybe a bad bearing but I really don't think that would effect layer shifting in only one direction.
I have attached some pics. From Left to right: Original piece (made it quite far before shifting), 90 degree shift same settings, 90 degree different settings, Original piece again.
So I think it's heat related... but if its' the stepper motor does it make sense it would only fail in one direction? Also it's shifting within layers too. Not just the entire layer shifting but throughout a layer.