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Jon_S

Details/Features on STL causing Z-Axis Banding/Stripes

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Hi first post here so apologies in advance for being a clueless noob..  :)

I have been reading around the forum for a while and it's been really helpful but I've reached the point where I need to ask about a specific problem I am having with my Ultimaker Original + that I recently bought 2nd/3rd hand.

It seems that surface detail and features on STL files is causing banding/stripes in the z-axis, almost like a change in the toolpath for the nozzle is resulting in under/over-extrusion.

Here it is at 70micron layers:

70_Micron.thumb.png.a1b459b1befa42e638655bbcbb7c5883.png

I thought that printing thicker layers (100Micron) might hide any inconsistencies if the z-axis wasn't moving up and down quite the right amount during retraction but it is more pronounced:

100_Micron.thumb.png.140040cc22e46574c481007bc6e73470.png

I also tried the same settings but with retraction disabled and it was pretty much the same:

100Micron_Retraction-Disabled.thumb.png.450bc17fe6ee3691783da4143de67a1b.png

Also here on one of my own models you can see it at the top of the hand:

Al_Banding2.thumb.png.e9c2ec4778124b25b97fd13cb6f4b5d2.png

I was wondering if anybody else has had this problem and could they give me any clues or ideas to try?

I feel like maybe it's a Software vs Firmware issue,  I am using the latest Cura but the firmware is from http://marlinbuilder.robotfuzz.com/  because the printer has a DIY heated bed.  

Would I be better off using an older version of Cura that might match the firmware better?  or maybe customizing a newer firmware?  

Is this just what the Ultimaker Original does and should I stop whining? ;)

Any tips would be greatly appreciated or if this has been discussed before and you can remember the thread please send me over there to read it

Hardware Things I have tried so far:

New PTFE coupler as the old one had nearly worn a hole in the side-  quality improved

Dismantled and rebuilt the z-stage, cleaned and greased rod, checked the platform moved freely on the bars (at the upper end the cable for the heated bed was giving some tension pulling the platform back but the cable has more slack now)

The brass nut was jammed in kind of skewed so I repositioned that

nut.thumb.jpg.951e54963be53629d41282f0318fa178.jpg

After 20+ atomic pulls I attempted to take the nozzle assembly apart but I broke the isolator tube.  There were two gaps in the assembly full of carbonized material so I bought a new nozzle assembly and the print quality is much better.

Aligned the x-y axis.

Things I need to do:

The long belts in the x-axis need to be tightened.  They are much looser than the y-axis (which moves smoothly) the x-axis is a bit more sluggish.

Thanks for reading!

Jon

70_Micron.thumb.png.a1b459b1befa42e638655bbcbb7c5883.png

100_Micron.thumb.png.140040cc22e46574c481007bc6e73470.png

100Micron_Retraction-Disabled.thumb.png.450bc17fe6ee3691783da4143de67a1b.png

Al_Banding2.thumb.png.e9c2ec4778124b25b97fd13cb6f4b5d2.png

nut.thumb.jpg.951e54963be53629d41282f0318fa178.jpg

Edited by Guest

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It's the loose belts thing. Also make sure the short belts are tight. The issue you have in the robot photo is called "backlash" and it is also called "play". I recommend you read about it in wikipedia.

Also scroll down to the photo with the green lines that talk about backlash here:

https://ultimaker.com/en/community/2872-some-calibration-photographs

Now the other problem with the model with the hand - I think that's underextrusion - most likely due to the Z stage moving too far occasionally but it could be filament tangles, sudden nozzle temperature changes, who knows what else. I think that's going to be a more serious problem and harder to fix for you. First compare all models you have printed and see if the problems tend to occur at the exact same height (mechanical problem) or different heights (tangles in filament or Z stepper overheating issues (this is common)).

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Thanks for your reply, I will get reading and have a look at the belts.

I should have mentioned the problem with the hand, that model was printed before I rebuilt and cleaned the z-stage and put more slack on the heater cable and added the new nozzle.

I have only printed those robots since and the quality is much better but I need to print some more different test cylinders or tall cubes and models for comparison. The problems seem to occur where changes in geometry/features begin and end.

Most of the time the nozzle temperature seems stable at 230deg but I have noticed that it sometimes fluctuates by +/- a degree. Could this mean the true temperature is actually fluctuating a lot more?

I noticed today the temperature for the heated bed is set at 70deg but climbs up to 74deg then drops back down to 69deg and then back to 74deg.. I will keep an eye on that too.

Thanks again for your help

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So I had a go at tightening the long belts using these: http://www.thingiverse.com/thing:17058/#comments

The belts are now tuneful when plucked (like the video on youtube) but they are not all singing the same note. I don't know how important that is but I'm guessing it's best if they are as close as possible to the same tension so I will have another go with that maybe print out some different size increment to what I already have.

I have tightened the short belts as much as I can without adding some kind of extra tension device.

I printed out a quick tower test model I made:

Tower_Test.thumb.png.96638d167584d4052935bd31d25d984e.png

There is some regular banding to it but nowhere near as deep and pronounced as the robot and also a different frequency. Its not a bad print I guess, a bit of spraypaint would cover it up :)

I also did another robot same file/settings as before. It seems like my efforts to tighten the belts didn't change anything:

Robot_Tower_Test.thumb.png.a665a5cc0c3d5cf4717bc9c5c144d98a.png

Tower_Test.thumb.png.96638d167584d4052935bd31d25d984e.png

Robot_Tower_Test.thumb.png.a665a5cc0c3d5cf4717bc9c5c144d98a.png

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