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braddock

Noticeable Banding in Z

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Hi guys,

This last weekend I've been running some test prints and I've been getting some noticeable horizontal banding in Z.

Still using Cura 14.01

This part was printed at 0.05 so should be very smooth. I was getting great smooth prints just last week.

Any ideas on what's causing this?

Cura 14.01

Temp - 230 (also ran one as 220 - same result)

Bed - 65

Layers 0.05

 

banding

 

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My first guess would be that some sort of clog is developing in the hotend.

My second guess would be that your filament has some physical or chemical quality issues.

I would run some material through the machine by hand and see how extrusion feels. I would also try the exact.same.print with a different filament and do a direct comparison.

 

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Thanks Nick, I've had fantastic prints with this same spool of filament, and I also ran 2 perfect extrusion cylinder tests, so I'm really not sure what this is.

It gets better the further it moves up, interestingly once the islands for the supports I put in are no longer printing.

I have a theory but need to wait till tonight to test it.

 

 

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The smaller the layer height, the more likely you can hit Z accuracy issues. It's why I prefer printing at .2mm layer height for most prints. There is usually a layer height where if you go any smaller it starts to get worse again.

Anyway so my point is that I'm guessing that your Z layer movement isn't consistently .05mm and sometimes it is a little less and sometimes a little more. But this theory could be wrong - your layering in your photo is not quite what I expected. But at this thin a layer height maybe this is how Z accuracy error looks - because a layer that is thinner than .05 will overextrude and create a thin tiny bulge line and a layer where the Z axis moves more than .05mm will look just like underextrusion.

 

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I have a few thoughts on this, firstly, i've had many great prints at 0.05, 0.06

I bought a 3d printer to do high resolution prints, I never would have considered an ultimaker if not for the claimed resolution of 0.02

0.2mm is not an option, there's detail in this model in particular that isn't even captured at 0.05

If Ultimaker claim the UM2 can print 0.02 layer heights accurately, then that's what I'd expect, if anyone from UM, officially suggested I print at 0.2 - or even 0.1 I'd be screaming for a refund!

Your analysis does seem to explain what i'm seeing though, but this doesn't mean I accept it, it should be better.

 

 

 

The smaller the layer height, the more likely you can hit Z accuracy issues. It's why I prefer printing at .2mm layer height for most prints. There is usually a layer height where if you go any smaller it starts to get worse again.

Anyway so my point is that I'm guessing that your Z layer movement isn't consistently .05mm and sometimes it is a little less and sometimes a little more. But this theory could be wrong - your layering in your photo is not quite what I expected. But at this thin a layer height maybe this is how Z accuracy error looks - because a layer that is thinner than .05 will overextrude and create a thin tiny bulge line and a layer where the Z axis moves more than .05mm will look just like underextrusion.

 

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Well the UM1 and UM2 can definitely achieve .05mm but it's more difficult. Do you have an Original or UM2? I forgot, sorry.

But my point is that I suspect Z axis issues. Maybe acceleration or jerk is too high. Maybe you need to add more grease. Maybe something is sticking. For the Original there are all kinds of issues with the Z nut and how it is held in place that can cause banding like this.

If you want high resolution, it seems silly to use a .4mm diameter nozzle hole and then use .05mm layer height. To get really good resolution in Z seems a little bit of a waste if you aren't getting it in X and Y. For really amazing resolution it would be good to get a smaller nozzle - maybe a .25mm nozzle.

 

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I have a UM2

Good point regarding the nozzle. I do make larger parts though, so really the 0.4mm nozzle is probably the happy medium

There's another thread discussing the magic layer height being 0.04

Ultimately this kind of work is better suited to a different process, like DLP but i'm trying to get the best possible results out of my UM2

 

 

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I print at 0.07mm on UM1's all the time with results that are worth the increased time.

It sounds like retraction is exacerbating the underextrusion problems, which is definitely a sign that there is friction/stiction in your hotend somewhere. After spending some time fixing a friend's UM2 last weekend, my suspicion would be your teflon piece has begun to creep or deform, causing it to restrict filament flow more than it should. I'd open up the hotend and make sure everything is looking normal with the teflon and filament can pass through it easily.

Also give yourself the best shot at success by clipping the (likely now deformed) filament that is currently in the machine, because the extra force the extruder was putting on it while trying to overcome your underextrusion won't help you get smooth results during your troubleshooting.

 

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I've been through all the under extrusion problems, and my printer is printing perfectly, other than this part on the weekend. Just this morning, printed a perfect extrusion cylinder without pulling anything apart beforehand.

So, I can only assume it's more what gr5 is suggesting.

0.07 might not amplify the issue quite so much.

 

 

There's also the possibility that dust on your filament has started to collect in the nozzle and cause a blockage, but I think that is pretty unlikely to cause a slow failure instead of a sudden plug. My bet is the teflon piece.

 

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