Layers slightly misplaced on Y bed axis after 3 or more

[mediaklan]

Hi everyone !
My prints are almost fine, apart from a strange problem, and I'm not sure where to look to solve it. Here's the issue :
Print always start good, but after 3 or 5 layers (sometimes a little more, 9 or 15), the bed seems to move a little too much (always messing in the same direction), misplaced two or three layers, but then everything's fine again. For now, I can't post a photo to illustrate the problem, but I will as soon as I can.
Bed leveling doesn't solve this, since it's not happening for the entire object, just 2 or 3 layers max. I'm thinking it could be something in my slic3r settings, but I'm not sure where I should look.
I'm using a 0.4mm nozzle, and two pieces of glass one below the other for the bed and at first, I thought the two pieces of glasses were moving (too heavy maybe ?), but I made sure there were not, and still have the issue.

[zhangxueyou]

I met this problem ever. Because the filaments wound together, so it was stuck that the motor had not enough power two pull those wound filament. So it printed in the wrong position.

[mediaklan]

hmm... it makes sense. I'm having trouble to get the filament reach the extruder without pressure. I will try with a filament guide of my own creation and a spool bushing (http://www.thingiverse.com/thing:759559), to see if I can put less burden on the motor. Just for me to know, do you have to level the bed after each print ? For some reason, it seems I always need to check the leveling after each print (which is becoming quite tiring). It's not always off after a print, but it happens a lot nevertheless.

[zhangxueyou]

No, for me, I only level the bed for once.
It may be better to let the axes auto home first, then raise z axis properly, and auto home again before printing.

[mediaklan]

(...) then raise z axis properly (...)

Interesting! Not sure I understand though : raise z axis after an auto-home, ok, but raise z properly ? To what ? Auto-home isn't enough ?

[zhangxueyou]

(...) then raise z axis properly (...)

Interesting! Not sure I understand though : raise z axis after an auto-home, ok, but raise z properly ? To what ? Auto-home isn't enough ?

I am afraid that even after you printing, the z endstop is still triggered. When you choose "auto home", the z axis can not move but it actually has raised a bit. So I suggest you raise z properly to make sure z endstop is not triggered, and autohome again.

[mediaklan]

Recently, I've customized the latest marlin firmware (marlin-1.0.2-1) using the configuration.h I've received from Geeetech. The printer is working very good, better than before, with less stepper noise, and more accurate printing ... apart from one thing : Y bed axis shifting problem is back, and even worse than before ! (which of course totally mess up the prints at some point).
I don't think tighten the belt will do anything now, as I've already tried a couple of times...
Do you guys think it could be related to a certain conf/setting in the configuration.h file ? Am i missing something ? Any idea ? Thanks !

PS : for testing purpose, I'm gonna tried with the geeetech firmware I was provided and tell if it goes differently.

[zhangxueyou]

No, you don't need to tighten the belt. I mean, when somewhere of the filament is stuck , x motor has not enough power to pull it, so x axis can not move to correct positon to print. I met the same problem before, and that's the reason.

[mediaklan]

OK, I found out I had not one but multiple problems :
- Not enough lubrification on Y axis and X axis. As soon as I oiled them a little, that was already better.
- Marlin configuration for acceleration was way too high for my prints. I'm still struggling with it but the major Y layer shifting is gone.

Configuring the Marlin firmware is quite fun, but it's not that easy to come up with the settings I'm hoping for. Examples :
- Z axis is a little too fast when homing for example, I want it to be faster than before (faster than the Geeetech settings I mean), but not that fast...
- Got a small problem with extruding filament setting, which might not be enough (there's sometimes tiny gaps in my prints).

[zhangxueyou]

You don't need to change the firmware we sent you, it has been well set.

If you want to change homing speed, you can change it in "configuration.h", find:

Code: Select all

#define HOMING_FEEDRATE {50*30, 50*30, 4*30, 0}  // set the homing speeds (mm/min)

From left to right is the homing speed of x, y, z and extruder. You can decrease the 3rd value slightly.

To disaappear the gaps, you can raise the hot bed when printing.