3d print offset in Y-axis direction

[WJL 0]

I'm printing a large helmet shaped item (interior hollow) that is sized 176 by 183 by 170 mm  in XYZ.  It is basically the left side of the helmet.  I am  using ESUN PLA+ filament on a Ultimaker 2 printer with Cura 15.04.6 software.   Lots of successful smaller prints prior to this using regular PLA filament. 

 

This print has a shift in +Y (towards front of printer) at a height of roughly 1 and 2 inches.  The offsets in Y are 1/8 and 3/8 inches.   Shift is same on both exterior helmet edge and interior fill.  The print was stopped.     Print is largest at base.   Print is on glass plate without anything to help adhere such as glue or blue tape.  Printed using modified fast settings (0.15 mm layer height, 0.4 mm nozzle, 1.2 mm shell thickness fill density 10 percent.   I usually use fast settings without issue for my prints.   This time I upped the shell thickness from default 1 mm to 1.2 mm to make it a multiple of the nozzle size as recommended.  Issue is not the settings.

 

I had just started to use the ESUN PLA+ filament and added just a smidgen of oil 2 prints earlier.   One was an even larger helmet (over 190 mm in XY) that also shifted.   The second was a smaller helmet segment sized 64x176x128 mm in XYZ that was fine. 

 

Now, it could be that the print is too large and the print head is hitting something or just unhappy with software instructions, but I would have expected that at the base where brim and print is largest.

It could be that the print shifted on the glass plate, but it seemed to be adhered on plate until plate cooled (I did not stop the print, so did not see).  Having said that, the helmet has a small base where it adheres to the plate (with brim) on helmet flanks and then extends (with support) towards top of helmet shape.   So, certainly plausible it shifted.  There is no obvious evidence on plate that shift occurred.

 

It could be that a gear shifted or something causing a Y shift, but I'd expect that to happen more than just twice.  And it did not happen to the middle successful print.

It could be the cura software and firmware are too old and don't support large prints well and I should update or that I should use a plugin that extends max plate print size.

 

Lots of possibilities.   Anything obvious such as cura 15.04 does not support this large a print (176x183x170 mm)?    I know Cura does not like anything sized over 184 mm (if you check the scale, model turns grey).   I suppose I will have to divide and conquer such as trying glue stick on plate and seeing if it shifts.   Any comments?

 

Bill

 

 

[fbrc8-erin 287]

Hi, Bill,

To confirm, you're seeing a hard shift like this picture below?

 

 

This is a result of missed steps. If the printhead encounters resistance trying to move, the X (or Y) motor will miss steps/lose count and you'll see a shift--the printer counts all its steps based on the home position before printing. Normally if it happens once, I'd go ahead and lubricate your X and Y axes. You may also want to check your pulley and sliding block alignment. Also, when moving the printhead by hand, feel if one motor is giving you more resistance than the other one. 

 

If everything is lubricated, aligned, and your printhead doesn't feel hard to move by hand, it may be a one time glitch and usually doesn't come back. If you start seeing it across multiple prints after checking all of those things, then there may be a bigger issue at play.

 

[WJL 0]

In response to Erin, attached photo shows the offset in the support structure.   It occurs at roughly z = 1 1/8 in and 2 1/8 in.   There is no offset in the X direction, the surface is smooth at all heights (closest surface) .    The offset in the Y direction is about 1/8 inch at height of 1 in and 3/8 in at height of 2 in.

 

I have heard from someone where I work that I should be looking into "Layer shifting" and that it probably is a lubrication or belt problem.  I guess that is the same as "Missed steps" mentioned by Erin. 

 

The coworker suggested that there are max acceleration parameters that I could tweak. They don't show up on the older Cura (15.4)that I use.   They suggested that I should update to cura 3 to find these parameters.   Any suggestions on which parameters (as I slowly work through the machine hardware issues, printing slower to get it to work).     

 

They also said they had no problem running cura 3 gcode on the Ultimaker 2 printer with older firmware (15.4).   Thoughts on this?  I suspect all the dual head support and whatnot is for newer printers than Ultimaker 2.  Or do I really need to update firmware to match cura version?

 

Bill

[fbrc8-erin 287]

It sounds like we're both describing the same problem with different terms. This definitely looks like a "hard shift"/"missed steps" which different from "slanting/tilted" prints which are usually the result of a loose pulley set screw. A loose pulley would give you a gradual tilt rather than a hard shift.

You can play with the travel speed, which is usually the highest speed since it's not tied to extrusion. I would try lowering it.

 

The fact that you're only see the issue in one axis makes it more likely that it's hardware related rather than settings related. Definitely try lubricating the axes and check by feel to see if the Y axis is harder to move than the X. 

 

 

I would recommend updating the firmware and Cura versions. I recently worked on a printer that was still running it's original 2014 firmware...there have been a ton of changes since then.