(SOLVED) Layer shifting (again)

[Kevig 0]

Hello,

 

first of all, yes i read tons of  articles about this and tried the solutions.

i design with openscad then slice with cura 3.6.0, save it on an sd card and finally print with the TEVO black widow.

 

the problem is every now and then i get a layer shift.

thirst i tried all the sollutions, but the i started to experiment.

- when i start the same print again i get the same layer shift at exactly the same location and the same shift.

- when i slice again with cura there could be no layer shift or a new layer shift

(this with the exact same setting in cura)

 

so

- if it is a loose pully it should happen more randomly.(even if i wanted i could not get a loose pully to skip at axactly the same spot twice at a row)

- if it is a defective SD card, it would be solved by changing the card (tried 3 cards withe and without extra formatting)

- if it is a setting in cura, it should happen exactly the same after re-slicing withe the same settings

- if it is in the printer firmware, it should happen with every print.(re-installed the firmware, and it was the same firmware with the previous cura version wich worked fine)

 

in my opinion it starts to look like a bug in cura, evenmore because it started from cura 3,6,0 and didnt happen in 3.5 or 3.4.

now i have a big thing to print (3days printing and a lot of filament) and have to gamble

will it print or shift......

and if it shift will it be will it be 0.4mm or 10 cm (both happend, 10cm overnight and we all know the mess i found next day....)

 

anyone any suggestions?

 

Henk

 

 

 

Edited January 17, 2019 by Kevig

[Smithy 1,135]

If it is Cura, you should see the layer shift in the layer view, but you have to zoom in extremely. 

 

But I would install 3.51 again and do the print with the older version if you think it was just coming with 3.6. Especially if you have a 3 days print in the queue.

[Misant 0]

I have experienced the same sort of problem. (Ender 3, marlin 1.19, BLtouch, Cura 3.6)

I have this stl. I sliced it with Cura 3.6, it looks good and made 1 print.

I get shifting layers.

I tried again, fixed the STL in FReeCad, sliced it with Cura 3.6. I get shifting layers exactly at the same layer and of the same exact amount of shift. The STL looks good when sliced in Cura 3.6.

Trying to see if it was the Y-axis, but shift at the exact same layer twice would be very strange for a slipping pully, I decided to just rotate the STL 90 degrees in Cura 3.6. Sliced STL looks good again. I print it, expecting layer shift in the Y-axis again at the same layers at the 2 attempts before but now.... it prints perfectly, no layer shifts, not in Y not in X.

 

I looked in the gcode and the layers co-ordinates for the shifting layers are the same, gcode looks good. Rotating the object 90 degrees and printing it is proof of that and I manually checked the gcode of the object.

 

I had this happen to another small object, shift were also in the Y-axis, solved that by choosing another object which was the same as the small object but a taller version, cant remember if I rotated that 90 degrees compared to the small object.

 

Kevig, if you contact me, we can share some information and try to solve this.

 

I attached the file that has shifting layers, but when rotated 90 degrees, shifting layers disappear.

CE3_case-bottom-d-fixed.gcode

case-bottom-d-fixed.stl

[Misant 0]

A thread also describing our problem, lets continue there.

[Kevig 0]

i noticed:

- rotating the object 90 degrees seems to solve the problem

(did not try  smaller rotations or 180 rotation)

- re-clising changed the location of the shift, not the ax

- the problem occeurs often the layer before or after a change in design
(ie i had a keychain with cutout characters, the layer after the characters shifted or with a fanduct exactly at the end of a internal screw hole)

 

in the next couple of days, i am going to try different angles and cura 351

 

henk

[Smithy 1,135]

21 minutes ago, Kevig said:

i noticed:

- rotating the object 90 degrees seems to solve the problem

(did not try  smaller rotations or 180 rotation)

- re-clising changed the location of the shift, not the ax

- the problem occeurs often the layer before or after a change in design
(ie i had a keychain with cutout characters, the layer after the characters shifted or with a fanduct exactly at the end of a internal screw hole)

 

You have a problem with your printer hardware, loose belt, loose pulley or something like that. Check the tension of your belts, check if the belt itself is ok. I am sure you have some play on one axle and due to a direction change, the layer will be slightly shifted a little bit.

[gr5 2,005]

This is almost always a slipping pulley.  Does your printer have belts?  That go over pulleys?  If so tighten the hell out of the set screws that keep the pulley from slipping on the shaft.  Also mark the pulley and the shaft with a marker to see if it is moving after your next layer shift.  Usually it's the pulley that is hardest to get to such as the one on the motor.

 

[Kevig 0]

@smithy and Gr5

off course i checked my pulleys and belts, they are ok

(i broke my allenkey on it)

 

and also it is virtually impossible to get a slipping pulley or belt to slip twice at exactly the same place, and exactly the same amount of shift and on top of that, no shifting besides that.

and if i rotate the same model 90 degrees, reslice and reprint no shifting occeurs at all

 

if it is a loose pulley/belt, it should shift randomly or the shift same amount every time the pulley is in the same position.

and it should do the same after rotating the model

 

when printing the keychains (as shown in the pictures) i tryed to simply reprint (turn of printer, turn it on again, load the model from SD card and start printing) and it shifted exactly at the same layer and the same amount

 

so i think i can rule out: Pulley, Belt, SDCard and Open scad

left over: the merlin firmware or CURA 3.6.0.

 

henk

[tinkergnome 924]

It's just a guess, but it is well possible that Cura 3.6 generates a different tool path (compared to the older versions).

Perhaps with higher accelerations or faster direction changes and your printer cannot keep up and loses steps at some point...

The y-axis has a greater inertial mass and is more prone to this problem. That's at least a possible reason why it works sometimes better with a rotated model. 🤷‍♂️

Edited January 2, 2019 by tinkergnome

[Kevig 0]

Found it.
my Vref on the stepper-drivers was to low.
as a result the motor did not got enough power to move the printbed and skipped steps
(printbed is the heaviest part on my printer)
i increased the power from 0.72 to 8.7 and the problem dissapeared
the temp from the drivers rose from 55deg to 59deg
Henk

[CamiloZuluaga 0]

On 1/17/2019 at 7:13 AM, Kevig said:

Found it.
my Vref on the stepper-drivers was to low.
as a result the motor did not got enough power to move the printbed and skipped steps
(printbed is the heaviest part on my printer)
i increased the power from 0.72 to 8.7 and the problem dissapeared
the temp from the drivers rose from 55deg to 59deg
Henk

 

Great you find the answer. Before find your post I arrived to the same conclusion, It wasn't about something mechanical. did you change the power in the firmware or did it moving an internal potentiometer? I saw a video of someone doing it. 

 

Thank you!

[Kevig 0]

i had to turn a potentionmeter
i used the video on youtube
henk

[powersd89 0]

I am late to the conversation, but i wanted to share my experience as well. On my ender 3 V2, i measured the Vref for the Y-Axis at 1.20V. I lowered this to 1.00 and my problem has disappeared for my first 8 prints.

 

Thanks to Kevig for getting me down the right path on what to investigate. 

[hubbs 0]

@SandervG - This sounds almost identical to my issue. Any tips/ideas?

[OPC 2]

Had a similar issue with my UM2 ext+ mark2, checked all the obvious mechanical problems (loose belt, pully..etc) and practically rebuilt the entire top end when I upgraded to the mark 2 tool changer. I found lowering the acceleration and decreasing friction of all sliding components by adding some sowing machine oil fixed the problem for me. I have travel and print accell set at 1500 mm/s^2.  If I Increase it above 2500 the layers start shifting again. I also had one of the brass(?) sleeves seize on the Y-Axis shaft from using improper oil that collected crud and gunked up. so make sure they're clean and you're using the recommended lubrication for your printer.