i3 shifting on Y-axis (tried quite a few things :-D)

Hey!
I am building/using a Prusa i3 in the "Achatz"-edition (reprapuniverse.com/catalog/product_info.php?products_id=90) and so far most things worked nice.

But I am still having massive problems with shifts on Y-axis. They only occur when I have lots of movement in Y-direction, or better when I have several direction changes in Y-direction. Printing small cubes, circles, hollow boxes etc. works fine. I also already printed a squirrel which came out fine, but more "complex" things fail due to the shifts.

I already tried:
- Loosening the belt
- Tightening the belt
- Raising stepper driver voltage (and so the maximum current of the motor)
- Lowering stepper driver voltage (to prevent overheating and though skipping steps)
- Lowering the speed of printer in Slic3r (perimeter speed, zig-zag-fill-speed etc.)
- Lowered the acceleration and jerk values in the firmware
- Change stepper drivers between X and Y-axis to make sure the driver is not damaged (it is not)
- Flattened the motor shafts and fixed the pulley really tight to prevent slipping
- Oiled all rails to make them run smoother

Last thing I tried (this morning): Changing the stepper motor.

There came Wantai 42BYGHW811 steppers with the printer kit which are rated for 2,5 A. That is of course much to high for the Pololus. I thought that maybe the steppers can´t reach full torque due to the relatively low current setting around 1.5 A (got fans on the board, don´t worry). Now I got another stepper (this one: [www.watterott.com]) which should be strong enough but rated at a much lower current.

I switched the Wantai with the new one, set up the Pololus and tried printing. Small box works fine, but there are still really bad shifts, when I get to objects with direction changes on the Y-axis.

To be honest I am slowly at the end with my knowledge and ideas of what could be wrong or what I could improve, so it´s up to you now.

Thanks!

Best regards from Germany
Florian

Hi buddy could you put a vid of this happening

I will try to do that, but it takes me a moment. :-D

Yeah, that was so clear. It works when somebody is filming...

It has only minor drift so far, but there are still some layers to come (9/22 now). I will upload the video to YouTube and take some pictures. You probably don´t need sound, do you?

Here are already some of the previous tries, I think you can see what happens/happened.

I had the same problem as you and tried everything you tried yourself, almost drove me nuts!

I solved the problem by changing the jerk settings like this:

#define DEFAULT_XYJERK 10.0 // (mm/sec)
#define DEFAULT_ZJERK 0.4 // (mm/sec)
#define DEFAULT_EJERK 5.0 // (mm/sec)




Hope this helps!

Thanks for your reply!

I already set them to 5.0, 0.4, 5.0.

Don´t know if 5.0 is now just too little for XY. Any ideas?

Pictures of the print I just finished. Seems like now there was the major shift in the last layer, but that ruins it, too.

The crippled overhang is another thing for itself, I think.

Video is uploading, will take about 200 minutes. -_-
Great internet connection here...

Anyway it shows the complete print process, speed up to 600%. Hope this can be helpful.

[youtu.be]

Anyone got any ideas so far? :-/

check if your motor is ok conected, , also check if limitswitch is ok, maybe it sends triggered signal during print.

Du kannst fasuchen alle y axis kabel austauschen, villeicht is irgendwo schlehte konntakt.Dammin dennke ich auf motor und limit kabbeln.

and yes, in english, i think its only one option left, to try change motor and limit switch cables.

Hey! Thanks for your ideas!

I checked the motor cables, they are all fine and do not get too hot or something like that. So this seems to be fine.

I also tried to push the endstops while printing and nothing happens in that case. I think the printer only uses them once to check where he is (homing) and ignores their input after that.

So, good ideas but no change at all. :-(

You do not tell which speeds you are printing at.
Try to make a print at really low speed 10-20mm/s max on all settings and see what happens.

Are you sending the file from the computer or printing from SD card. I have had a skip on mine when I use the computer for other thing while the printer is running. From SD card never a problem.

I am sending the data from Repetier Host on my Windows 7 laptop.

I used to have 30 mm/s printing speed and most of the standard values in Slic3r, but I´m currently printing with 10 mm/s for all parameters. Will take a while, I´ll report back. :-D

Okay, didn´t take long. Did a major shift in layer 3 (5 mm in Y-) and I canceled it.

Possibly it´s worth to mention, that he is always shifting to Y-.

In your slicing software, adjust 2 settings. Check your speed for "Non Print Moves", try lowering this number. They are usually set a higher number then print moves to help fight "ooze bane". But if your motors can't keep up with that speed, it will "skip" steps. Second, if you have the option, try turning off random starts for each layer. This setting was to prevent a "seam from forming up the side of a print from starting in the same location for each layer. Turning this off will help prevent large non print moves where your motor can't keep up.

In your first post, you mentioned everything you tried "mechanically". But I didn't notice you mentioning if the bearings are gliding smoothly. You won't be able to tell with your belt on the motor because this is creating a resistance. With your belt disconnected, your axis needs to be able to slide just from gravity (not with help from pushing on it) when the machine is tipped on it's side.

Edited 1 time(s). Last edit at 08/01/2014 02:10PM by KingRahl.

Didn´t think about rotating, that fixes that problem, right.

Anyway. I checked Slic3r and the non print moves are set 10 mm/s already, so that´s out. Also the random start seems to be turned of right from the start now. Found that option, but it was not checked, so I got that going, too.

Well, I think they are gliding quite smooth. I filmed them: [www.youtube.com]

What you notice is, that the carriage gets "pushed" or "pulled". That comes from the cables, running under the bed. I´m not 100% sure, but I don´t think that´s an issue, cause that won´t happen, when the belt is on the motor...

The last thing that's possible it to check out your end stops again. Whether they are wired in the "always on" or "always off" positions, if the signal becomes disconnected, the axis will only move in one direction. Check all the wiring on the end stop, switch with another axis, check the solder joints, and check the plug to make sure it is tight and coming in contact with all the pins on your board. Worse case scenario, you have a bad end stop and need to replace it.

No, the end stops are not the problem. As already mentioned, they are only used for homing the printer. I was just printing, held the Y endstop down, but he moved the bed forward and backward like nothing.

Anyway, that print also got shifted.

This sucks. :-(

Only when they are working properly. You mentioned you activated the end stop during the print and nothing happened. What happens when you unplug it completely? It should only move in that axis in one direction. Try unplugging it during a print for a second. Is it shifting in the same direction? When the board doesn't sense the end stop, that axis stops working properly. An intermittent connection will disengage the end stop for a short time, only move that axis in one direction, then re-engage and continue as normal.

When I unplug it completely, it only moves into Y+-direction, because it doesn´t knows where it´s home position is. So far, so clear.

When I unplug it completely while printing nothing happens. It just prints, as if nothing happened...

Does it make any noise when it skips steps? Did you check to see if the belt was binding at the stepper pulley or the idler bearing? What's your accelaration setting? Is it possible the glass plate is slipping on the heatbed causing mis-alignment? Is it possible that the HBP wires are catching on a protruding part of the printer frame? Try doing a couple of fast non-print moves by sending it gcodes to see if you can reproduce the problem without printing. If it's skipping steps at 20mm/s try doing a g1 y150 f10800 after homing the Y axis. That will ask it to move it 150mm across the Y axis at 180mm/s (which it should be able to do easily, but not if there's a problem). Try it a couple of times. Another thing, it could even be the PSU or a bad solder joint on the electronics board for all we know.

Hey!

No, there are no strange noises or sth. like that. I also checked the belt which runs fine, too. And the glass plate is tightly fixed with bulldog clamps. No problem there, too.

Here are some relevant settings

#define DEFAULT_AXIS_STEPS_PER_UNIT   {80,80,4000,645}  // default steps per unit for Ultimaker
#define DEFAULT_MAX_FEEDRATE          {500, 500, 5, 25}    // (mm/sec)
#define DEFAULT_MAX_ACCELERATION      {180,180,10,200}    // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for Skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION          60    // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION  60   // X, Y, Z and E max acceleration in mm/s^2 for retracts

// The speed change that does not require acceleration (i.e. the software might assume it can be done instantaneously)
#define DEFAULT_XYJERK                5.0    // (mm/sec)
#define DEFAULT_ZJERK                 0.4     // (mm/sec)
#define DEFAULT_EJERK                 5.0    // (mm/sec)

I tried your G-Code and that just works fine, too. Copied it several times, made a "back to 0" command in it and taped a pen next to it. Scribbled some nice lines here on the paper, but no problems with Y this time...

What I don´t get on this whole thing is, that I can print cubes and cylinders etc. just fine. They look really good I think. But whenever I print something more complicated it gets totally f*cked up. Honestly, that can´t be something mechanical or electrical, I think. Otherwise it would happen on those prints, too...

Tried another thing.

Put my stepper driver voltage for Y up really high, so that I could get 1,9 A for the stepper itself and lowered all the others a bit. No change at all, still shifting.

try 8 microsteps

I think I found it.

I never wondered about that, although I should really have done. My E3D hotend was always kind of loose. I tightened the mounting plate really well and thought everything was fine.

Yesterday I sat here and looked at the printer and realized, that the hotend may not move, when you push it...

Long story short:

The "mounting area" at the E3D v6 is 6 mm high, the mounting plate is 2 mm thick.

That gives enough space to move forward and backward, causing shifts, when you change direction and the hotend "sticks" to whathever for just a moment...

I got someone build me a new mounting plate and I think it will be fixed then. I will report back, when I got the new plate.

I had the same problem but much worse. I connected an LCD 2004 and eliminated the use of the computer and it worked perfectly. I bought mine from geetech.com.