Cura Layer Inaccuracies

[iverstaylot00 0]

Hi there, although this is only my first post on these forums, I have been using cura for many years for schooling and personal hobby. Recently, in the 4.5 update to cura, I have had issues reminiscent of the other forum topic I linked below from 2014. After a lot of testing on my end and researching other topics, I have narrowed these issues down without an inch of doubt to cura, as no other slicer I tried has this inaccuracy. Attached gcode of one of the models I printed that has this issue. I've attached a picture of the printed version of a similar model. Please note, it is NOT because of any machine flaws like loose belts or the sorts, I have near-perfect walls on other prints. 

 

Some Experimenting I've already tried to no avail:

Lowering travel to as low as 80mm/s

Lowering max deviation from the stock 0.05 to 0.035 (it's a multiple of my steps per mm)

Lowering print speed & accel/jerk

Different layer heights 

Many printing orientations

Drastically different print profiles to make sure it wasn't one or two particular settings causing this 

Tightening belts, lubing parts, (just to triple check no machine errors)

 

 

Some settings that may interest those who are way smarter than I am:

Layer Height: 0.2mm

Max Deviation: 0.035mm

Printed on: Ender 5 with TL-Smoothers & PTFE bowden

Accel: 350mm/s/s

Jerk: 6

Base Speed: 70mm/s

Outer Walls Printed @ 35mm/s

Inner Walls Printed @ 52.5mm/s

Travel Speed: 150mm/s

I know these speed settings are VERY conservative for an ender 5, however I like my print quality. Also, I hope this topic doesn't rub off as rude. I absolutely adore cura, and that's the reason I've been using it for years. I assume I am not the only person having these issues, but after a lot of googling I oddly enough wasn't able to find another topic like this other than the one below. If I've forgotten to attach anything important, feel free to ask. I tried to include everything relevant (and then some)

 

Also, as a last note, I know the attached image is not of the same model I submitted the gcode as, however it's sliced with EXACTLY the same print profile. I have the printed version of the submitted gcode, however my phone really struggles to capture the errors. The errors are easily visible on this portion of the model, the flat trapezoid shaped area really brings it out. The forum topic from 2014 I linked has some wonderful representations of the gcode causing these errors.

 

 

 

Main Turret.gcode

[burtoogle 510]

Hi, I have looked at the gcode in a viewer and it doesn't look lumpy-bumpy so I am guessing that the issue is not due to the gcode having poor coordinates (i.e. the corners are where they should be). UM Cura releases do have some bugs in the code that simplifies the wall polygons (the code that uses max resolution and max deviation) but I don't think that is causing your problem.

 

 

What I think is more likely is that the settings that you are using combined with the path that Cura generates is causing the print head to "wobble", i.e. it's a mechanical issue brought on by how Cura is driving the printer.

 

Do you have some sample gcode from another slicer for this part that doesn't produce the same variations in line positions?

[iverstaylot00 0]

38 minutes ago, burtoogle said:

Hi, I have looked at the gcode in a viewer and it doesn't look lumpy-bumpy so I am guessing that the issue is not due to the gcode having poor coordinates (i.e. the corners are where they should be). UM Cura releases do have some bugs in the code that simplifies the wall polygons (the code that uses max resolution and max deviation) but I don't think that is causing your problem.

 

 

What I think is more likely is that the settings that you are using combined with the path that Cura generates is causing the print head to "wobble", i.e. it's a mechanical issue brought on by how Cura is driving the printer.

 

Do you have some sample gcode from another slicer for this part that doesn't produce the same variations in line positions?

I do not have some comparison GCODE for that particular part, however I do have a pair of the Creality dogs! (I don't feel like reprinting a 30 hour print just to test, lol)

 

dog-2.5H is done with S3D, and has none of the seen inaccuracies (however the zseam is not configured properly, ignore that. I do not own S3D, a friend does and sent this to me)

 

cura-dog is sliced with my profile. They both have identical layer heights and very similar speeds, and other things. The only other major difference besides the zseam is the fact that the S3D model prints with a raft (which does not solve my issue, I have tried it but forgot to mention it)

 

I can get some photos for comparison if you'd like in about 8 hours, as I just left for uni and won't be back until dinner

dog-2.5H.gcode

cura-dog.gcode

Edited March 1, 2020 by iverstaylot00
Uploaded wrong gcode for cura dog

[burtoogle 510]

Don't worry about the photos.

 

[burtoogle 510]

BTW, using small values of max deviation with UM cura releases can give rough results. You may get better results using one of my releases that can be found at https://www.dropbox.com/sh/s43vqzmi4d2bqe2/AAADdYdSu9iwcKa0Knqgurm4a?dl=0

Please read the README.md file there for more info.

 

Also, you may want to disable the overlap compensation as that tends to cause artifacts.

[iverstaylot00 0]

Just now, burtoogle said:

BTW, using small values of max deviation with UM cura releases can give rough results. You may get better results using one of my releases that can be found at https://www.dropbox.com/sh/s43vqzmi4d2bqe2/AAADdYdSu9iwcKa0Knqgurm4a?dl=0

Please read the README.md file there for more info.

 

Also, you may want to disable the overlap compensation as that tends to cause artifacts.

Thank you so much for your help! I will try this after I get home from class and inform you how it goes!

[gr5 2,097]

So you are talking about those horizontal lines on that flat area?

 

Those are (seemingly random) over and under extrusion issues. 

 

It bother's me that your inner shell is a different speed versus your outer shell print speed.  Any time you change speeds you get over or underextrusion and if some of those horzontal lines were created some left to right and some right to left that would explain the issue.  But I suspect they are all printed in the same direction.  Still if the print head starts that outer shell sometimes near the flat area, and sometimes on the "back" side of the model then that alone (speed changes) could explain your issue.

 

Another common possibility with horizontal lines - the most common cause - is a dirty Z screw(s).  It's good to clean this occasionally.  You can either do a quick cleaning with some WD-40 and a qtip or even just a paper towel wrapped around a screw driver while you drive the screw up and down.  Or you can do it right and take it apart (very easy on an Ultimaker - just 4 screws hold the Z screw and stepper in and it just slides out the bottom of the printer) and clean it over some newspaper with lots of WD-40 and then reapply grease (just one pea sized drop of grease for each Z screw).

 

Note that the Z screw on pretty much every 3d printer in existence is typically a *triple* helix so if you clean in one track/thread you still have 2 other's to clean.  Sometimes 4 helixes.

[gr5 2,097]

Oh and to explain what Z screw has to do with this - you are doing 0.2mm layer height.  This will be incredibly accurate on average but each layer may be a little lower or higher than 0.2mm.  If some are 0.19 (doesn't move enough due to sticktion) and then one is suddenly 0.21 then the 0.21 will appear underextruded (not stick out as far - a mini valley).

 

Whenever the distance between nozzle and bed move less than 0.2 it will be slightly over extruded and stick out and the other's will be slightly underextruded and stick in giving you these horizontal lines.

 

This effect is MUCH worse if you switch to 0.1mm layer height.

 

This effect tends to be pretty repeatable as the dirt on the Z screw doesn't typically move around much print to print.  So you can print a Cube and then a pyramid and typically they will have mostly the same horizontal lines in the same spots.

[iverstaylot00 0]

9 hours ago, gr5 said:

Oh and to explain what Z screw has to do with this - you are doing 0.2mm layer height.  This will be incredibly accurate on average but each layer may be a little lower or higher than 0.2mm.  If some are 0.19 (doesn't move enough due to sticktion) and then one is suddenly 0.21 then the 0.21 will appear underextruded (not stick out as far - a mini valley).

 

Whenever the distance between nozzle and bed move less than 0.2 it will be slightly over extruded and stick out and the other's will be slightly underextruded and stick in giving you these horizontal lines.

 

This effect is MUCH worse if you switch to 0.1mm layer height.

 

This effect tends to be pretty repeatable as the dirt on the Z screw doesn't typically move around much print to print.  So you can print a Cube and then a pyramid and typically they will have mostly the same horizontal lines in the same spots.

Wouldn't a simple change between slicers excuse away the dirt problem? And also, I clean my machine very often so I doubt that's the issue. However, the fact I print my walls in 2 different speeds may be causing over/under extrusion definitely peaks my interest. I'll try out printing some test prints at a uniform inner/outer wall speed after I'm done trying out burtoogle's release and see if that helps. The thing I find odd though, is that I never had this issue until I updated to 4.5. Which confuses me even more. I've been printing with that profile for about 6 months now

 

10 hours ago, burtoogle said:

BTW, using small values of max deviation with UM cura releases can give rough results. You may get better results using one of my releases that can be found at https://www.dropbox.com/sh/s43vqzmi4d2bqe2/AAADdYdSu9iwcKa0Knqgurm4a?dl=0

Please read the README.md file there for more info.

 

Also, you may want to disable the overlap compensation as that tends to cause artifacts.

I've downloaded your release, running a test print now! Thanks again for your help 🙂

[gr5 2,097]

4 hours ago, iverstaylot00 said:

Wouldn't a simple change between slicers excuse away the dirt problem?

oh.  Yeah.  But I thought maybe this is a new problem that just started and if you go back to the old slicer the problem might still be there now.  Just one theory - easily disproved.

[iverstaylot00 0]

Hi all! Sorry for the late reply, I got absolutely swamped with labwork for midterms.

 

@burtoogle your custom build worked beautifully, and as per your suggestion I disabled wall overlap compensation in the main cura release. However, your anti-resonance feature has me hooked! Probably will be sticking with your build!

 

@gr5 I cleaned out my z screw and and applied fresh ptfe. Found a tiny bit of dirt that may have been a bit of a culprit in the over/under extrusion. I also tried out uniform wall extrusion speeds, and I noticed an improvement in the zseam! Also, I have a slight suspicion youve been the mod approving my posts, so thanks for that as well

 

Thank you both for your suggestions, I can post my test print results if you would like, however I think you can imagine what a creality dog looks like

 

Tl;dr to anyone reading this who had similar issues, try disabling wall compensation, or try out burtoogle's release

[burtoogle 510]

Hi @iverstaylot00, glad things have turned out better and that you are enjoying some of the extra that my builds provide. Have a go with the gradient infill sometime, I haven't had much feedback on that yet.