Weird physical vertical bands on 2 opposite spots - symetrical to center. Not VFA.
 
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Weird physical vertical bands on 2 opposite spots - symetrical to center. Not VFA.  

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Moyrn
(@wmarek)
Active Member
Weird physical vertical bands on 2 opposite spots - symetrical to center. Not VFA.

Dear all. 

My first post. I'm quite impressed... I played for 6 months tinkering an anycubic mega i3 to some real success (deep modding). But not reliable enough. My nerves... lost the game.

I ended up with the mk3s i just built one week ago. I carefully followed the instructions, except on 3 points (attached the Y engine to the frame with a tie - i was feeling screws were not enought ; twisting belts which helped on the anycubic limiting vertical banding ; igus bearings... until i can go to misumi. I disliked the stock LMU that i did not even tried. I attached the igus with holders from https://www.thingiverse.com/thing:2969556 which add some compression as well). 

I spent a lot of time investigating on anycubic on the famous VFA (vertical fine artifacts) to few success. Another debate. I deeply and humbly salute Guy for and related mates for the deep investigation made on these (0.9 motors, etc...). I deeply read the 6+36 pages of forum and will play with this later on (misumi rods & bearings, trinamics, pulleys...), because while i'm happy with the mk3s features and 1 week reliability... i'm somehow disappointed by the quality. I expected better. Mainly because of the VFA... well another story. But i mention this because the issue i reflect here is not about VFA.

All was fine in the early MK3s printing, and i took the STL is used from Anycubic/Cura - using Prusa profiles and altering to my needs (mainly z-scar management, combing, temperatures, low acc/jerk...). But only on the i3 MK3s did i endured the vertical "relief" bands. They are on the side of my print, a round side where X & Y move together. It's not existing on pure square ( 100% X or 100% Y) shapes. I can feel them with the tip of my finger while i cannot feel the VFAs for instance. They are rather depressed (vertical hole i would say)

On the picture they are exactly where the light falls on the top print. sorry 

Vertical physical bands on the round sides

There are 2 bands. One on the front left, the other on the rear right, fully symmetrical to the object center. I thought it was skew compensation because i was not fully perpendicular. I spent a (too) long time figuring how to achieve pure orthogonal XY shape. I finally achieved today ... Yay ! But alas the two bands are still there. 

I finally draw a simple cylinder on sketchup to check their presence. They are still there. If I rotate my STL, they are still there.

I still use Cura; but these bands were not on the anycubic prints.

I tried obviously the standard profiles (unaltered).

This is not the zscar either (i placed it on a specific angle using user coordinates + wipe + coasting)... but i also tried using random placement. Same. The picture one is using random z-scar place.

I use now the 0.25 nozzle, but that was also on the 0.4

I played with E linear calibration (you can see the print). Nothing changed

Voila... I tried to be accurate as required to beg for your help. I guess there is something mechanical to do with my built... but i can't see anything after checking.

Merci beaucoup ! Sincere & deep thanks for your kind help...

Wilfried

Best Answer by Moyrn:

OK that was it.

- IGUS wobbling on X & Y

- X belt scratching on the guide due to pulley location (teeth far from motor > now teeth close to motor)

When printing the circle area, when X reached the max position and changed to the other direction, a wobbling was induced thus digging in the surface...

Topic closed. I took the time to explain... in case someone faces the same issue.

Wilfried

Posted : 23/08/2019 9:45 pm
Moyrn
(@wmarek)
Active Member
Topic starter answered:
RE: Weird physical vertical bands on 2 opposite spots - symetrical to center. Not VFA.

I spent some time on it today. Suspecting the sort of Y-wobbling I had due to the IGUS. Because the mark happens when a max has been reached on the side or the circle. So the head is changing direction. Possibly a wobbling issue then...

I printed the Y bearings supports in ABS again (far better look and accuracy now with the MK3s than with the anycubic). Tried -0.5, 0 and +0.5

On the +0.5 could accept the IGUS. That was wobbling less, but sliding less now... so i switched to stock bearings, but in the printed supports. Some bike oil to ease. All done. No wobbling at all.  See pic for illustration

 

 

 

 

 

 

 

Made a print. I thought i had it fixed. It is just slightly better... but i assume better nonetheless. The VFA however seem just slighly more visible than with the IGUS. 

I guess next try will be to remove the IGUS from the X axis to put stock LMU. And test again...

Posted : 24/08/2019 9:38 pm
Moyrn
(@wmarek)
Active Member
Topic starter answered:
RE: Weird physical vertical bands on 2 opposite spots - symetrical to center. Not VFA.

Today I removed all IGUS bearings from X and Z. I also reverted the 16T pulley from X axis (teeth now closer to motor), as it was twisting and doing some friction on the side of the printed part). IGUS wobbling + this belt friction on was possibly making an artifact when X changing direction (which was my case). All seems to be ok now. Except for the VFA... but this is another topic. And some minor additional noise... 

To be confirmed by further prints.

Posted : 25/08/2019 10:21 am
Moyrn
(@wmarek)
Active Member
Topic starter answered:
RE: Weird physical vertical bands on 2 opposite spots - symetrical to center. Not VFA.

OK that was it.

- IGUS wobbling on X & Y

- X belt scratching on the guide due to pulley location (teeth far from motor > now teeth close to motor)

When printing the circle area, when X reached the max position and changed to the other direction, a wobbling was induced thus digging in the surface...

Topic closed. I took the time to explain... in case someone faces the same issue.

Wilfried

Posted : 25/08/2019 7:10 pm
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