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Dim3nsioneer

Horizontal banding on UM2

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Didn't read through every post since some are really long. Here are some of my personal experience. Since I usually print overnight, I realized than the banding issue at night is quite a bit worse than during day. Though after I laser cut and installed an acrylic door (nothing on top, yet), almost all banding issues disappeared.

Perhaps, it is cause by wind creating variation in temperature. This temperature causes inconsistent shrinkage of plastic after printing. Or maybe even inconsistent extrusions.

Another possible explanation is that the door actually slows down the speed of convection of hot air so it created an ambience of slightly higher temperature which allows less and more consistent shrinkage of plastic.

Maybe you can try adding a door and eventually a top. Maybe even a heated chamber.

 

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I noticed when I switched to Cura 14.03 that the cylinder had a slight hourglass curvature inwards for the first half a centimetre but this corrected itself

 

That inward curve is something unrelated. You can read about it here (5th picture down on left column of pictures):

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide

 

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Well your theory about the Z axis being off would explain what you see. And this is a COMMON problem for the Z axis to move not enough on some moves and too much on other moves.

But for it to happen exactly on every other layer for 10 consecutive layers? That is unheard of. Anyway this is worth investigating...

Connect your printer through USB to a computer and install pronterface (aka printrun) from here:

http://koti.kapsi.fi/~kliment/printrun/

 

Then use that to do experiments where you move the Z axis up and down. Also try moving it up and down with the power off by lifting hard at the rear 2 corners - one with each hand.

Is there grease on the Z screw? Your UM2 may have come with a small packet of green grease. That is meant for the Z screw.

 

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I will install pronterface asap and give it a whirl - thanks for the heads up!

I did use the green grease shipped with the printer and applied some to the Z screw, which did seem a little bare on the last couple of inches towards the top. When the printer is off I can move the bed up and down by hand (by the back corners). The bed will almost move downwards without pressure along the threads, except at the top couple of inches where it still needs a little downward force to move it.

 

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I've been getting a lot of horizontal banding lately as well and I can't find the cause. It's driving me crazy. It MUST be hardware related because I'm using the same gcodes and firmware as I always have and i was getting perfect prints before.

At this time I've checked just about everything I can check, from what I reckon. My last remaining things are:

 

  • Faulty feeder giving uneven amounts of plastic
  • Worn nozzle (doesn't really look worn though)
  • Loose belts (hard to know how tight is enough... I can move them easily up and down but they're not "floppy". Tried attaching a belt tightener but the belts are too tight to get it on there so I might have to make a custom one.)
  • Z-motor or axis problem. I DO hear an unveven "grinding sound" when I manually press the build plate DOWN.. sounds a little like in the video you linked above... like there is sand in the mechanism. But I don't really hear any grinding when I LIFT the bed manually... only when I push it down. I wonder... when I first got my UM2, the threaded Z-axis nut was faulty, causing the bed to drop several mm in intervals. This also placed a bit of sideways pressure on the z-screw. Maybe that extra pressure has caused the motor to break down prematurely?

 

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Hi joatrash,

That grinding "sand" sound you mentioned was the type of noise I started hearing one day as the bed/printhead moved into position immediately following the initial release of filament just prior to beginning to print the object. It was very noticeable and was not something that I'd heard before. On my machine it seems to still be present but has become less obvious.

UM's support team has just gotten in contact with me and want me to take a look at cleaning and re-greasing the Z-screw as well as making sure the Z shafts are still lubed up. They've mentioned that if that doesn't work they will send me a new Z-screw and Z-motor.

 

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Well your theory about the Z axis being off would explain what you see. And this is a COMMON problem for the Z axis to move not enough on some moves and too much on other moves.

But for it to happen exactly on every other layer for 10 consecutive layers? That is unheard of. Anyway this is worth investigating...

Connect your printer through USB to a computer and install pronterface (aka printrun) from here:

http://koti.kapsi.fi/~kliment/printrun/

 

Then use that to do experiments where you move the Z axis up and down. Also try moving it up and down with the power off by lifting hard at the rear 2 corners - one with each hand.

Is there grease on the Z screw? Your UM2 may have come with a small packet of green grease. That is meant for the Z screw.

 

Hi gr5 - just wanted to touch base regarding pronterface. Life has kept me from my printer the last couple of weeks, but I have it installed and read through what little documentation I could find. I am guessing that I can use it to manually move the printer head up and down to see if it steps correctly? If that's the case I'm not entirely sure how to gauge whether the steps are even or not, given how small the actually vertical movement is for each layer.

 

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Hi guys !

I am updating this post cause I have encoutered same problems as described here previously.

After a careful read of all the posts and the same symptoms, I did a complete calibration of the buildplate axis, printhead axis and belt axis.

Then, software modification (acceleration decrease, maximum speed decrease...) did a slight amelioration but nothing legendary !

Finally, after checking visually during printing, the flanged bearing F688-2RS of the back panel (corresponding to X axis) are not flat onto the panel. In fact, the bearing is out of its emplacement and produce a 1 or 2 degree of movement.

So I have unmouted the flanged bearing, clean the emplacement with a screw and put back the bearing in a perfect flat alignment with the panel and TADAAAAAA, banding lines disappeared.

This can explaine why an acceleration increase reduced the lines because the "ovoid" behaviour of the shaft and pulley was then reduced.

Hope this will help !

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Finally, after checking visually during printing, the flanged bearing F688-2RS of the back panel (corresponding to X axis) are not flat onto the panel. In fact, the bearing is out of its emplacement and produce a 1 or 2 degree of movement.

So I have unmouted the flanged bearing, clean the emplacement with a screw and put back the bearing in a perfect flat alignment with the panel and TADAAAAAA, banding lines disappeared.

EDIT: got it

Edited by Guest

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