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axsdenied

Vertical wall delamination

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Hi

In my last few prints the outer walls are separating from the infill and also the layers of the wall are separating from "each other". Image below shows it nicely. The individual vertical wall-layers are quite nicely bonded in the z direction but not in x and y.

5a3310bb7083e_IMG_20150831_22090501.thumb.jpg.2d5c7592729a7375478ab3ce171ace69.jpg

Any hints what could be wrong? Everything else looks OK.

Printing XT @ 255 degrees, 0.2mm layers, 40mm/s speed but previously I have seen the same issue with PLA.

Thanks in advance.

5a3310bb7083e_IMG_20150831_22090501.thumb.jpg.2d5c7592729a7375478ab3ce171ace69.jpg

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It looks like underextrusion. Is this 2 shells, one sticking to the part, the other delaminated?

Did you change your "infill overlap" setting in Cura (default is 15% which should be fine)?

Underextrusion can be caused by either not having enough material flow because of calculation errors (Cura diameter not matching actual filament diameter), OR because of insufficient heating power put into the filament.

Simply put - maybe you have to reduce the printing volume or increase printing temperature. 255°C should be high enough though. You could try decreasing your cooling fan speed, that will actually raise the nozzle temperature because it gets cooled down less.

You could also try printing at 35mm/s to lower the printing volume (mm3/s).

Usually, with XT it is better to actually print 40mm/s or faster, because if the nozzle moves too slowly, it can melt the printed part underneath it. You could also (considerably) reduce the printing volume by printing thinner layers, maybe 0.15mm

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Thanks to everybody for replies.

I have previously re-tightened the short belts (as suggested in the troubleshooting guide) but nothing changed. Doing another print right now (half-way into 40h print)...

Jonnybischof, yes that particular print has 2 shells with one sticking to the part and the other one delaminated. I also had prints with 5 shells and they were delaminating from each other and from the infill... it looked like a pack of cards.

I am using simplify3D with overlap increased to 70%. Once this print is finished I will try cura to see how it goes.

Underextrusion is possible. The PTFE coupler has seen better days but I didn't think that mattered much with XT. I have slowed down the current print to 80% (i.e. 40mm/s), increased temperature to 260 degrees and turned down the fan. Fingers crossed.

Thinking of increasing the material flow as well.

Jonnybischof, when you said that nozzle can melt the layer below if moving too slowly, does that explain the black blobs that I ocasionally get?

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This looks like typical underextrusion. I don't know XT very well. I have seen printers that underextrude and if you cut the print speed in half and increase temp by 10C they still underextrude and the only solution is to increase flow. In your case I recommend printing a small 10mm by 10mm hollow box 50mm tall with no top/bottom and now infill (0% infill) and .8mm walls.

Then watch it carefully while in TUNE menu. If it looks bad try setting speed to 50%. If still bad try raising temp by 10C. If still bad go back to original settings and start increasing flow. Flow takes 16 moves to take affect so when you change flow listen for the change in pitch in the feeder or the tick tick ticking to speed up. Try 110%, 125%, 150%, 200%. Take notes.

I'm guessing you have one of those printers that inexplicably need higher flow.

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...

Jonnybischof, when you said that nozzle can melt the layer below if moving too slowly, does that explain the black blobs that I ocasionally get?

 

It's been some time since I've last printed XT. I wanted to preserve my hotend until I have my second printer ready - which has been pending for a long time now...

The best theory I have is that the blobs happen during retraction. The hotend usually stops for a short time while retracting.

XT is a very "gummy" and somewhat unstable filament when heated - compared to the very tame PLA that just softens up and flows. XT expands, so even during retraction the nozzle will still ooze.

Now, the blobs may either be caused by the oozing, or because during the time the nozzle pauses, the material underneath gets heated and expands.

You might try to increase retraction distance a bit. But if this leads to longer pauses while retracting, it might not improve the situation. In that case you might even want to decrease retraction distance.

I'm not sure if this pausing problem has been fixed in Cura, but I think it has.

Lately, my prints weren't really quality-sensitive. Just work-related technical stuff that didn't need to look pretty. So I didn't pay much attention to details.

Usually, you can see the "expansion from prolonged contact with the hot nozzle" on the print's outer edges which will create kind of a brim that expands upwards and outwards. It looks like overextrusion, but if you decrease flow you'll see underextrusion inside the print. So, it's not overextrusion, but thermal expansion!

Another thing that comes to mind - there are the usual blobs that happen, and there are these typical black blobs you mentioned.

Maybe the black blobs have nothing to do with what I described above. It could be caused by little air bubbles trapped inside the filament. Or maybe it's just debris from burned up filament that was stuck inside the nozzle and then comes loose again from time to time.

So many experiments to conduct, so little time :(

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XT also absorbs heaps of water. I had one roll that was so bad the bowden tube steamed up and had water droplets in it.and this was a 2 day old roll.

The water makes it expand even more and it underextrudes, decreases layer adhesion and prints real bad.

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Just a quick update, running it hotter (260 degrees) and slower (75% speed) and setting material flow to 107% on the printer fixed/saved the running print. It was underextrusion.

The print took 55h to finish :-)

Then I installed a new PTFE coupler. There was not much of the original filament left but it seemed to be working fine with the original settings (255 deg, 100% speed). With a brand new spool of XT it has been working fine (30h of printing so far).

I read somewhere that the PTFE coupler does not have that much effect on XT (and ABS) but it clearly did.

I thought that the

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I was using the extra large XT spool. 2.2kg of plastic on a giant spool :-)

It has been opened for less than 10 days.

It has a much larger radius of curvature than the normal spools so that being at the end probably does not matter too much. The radius at the end of the XL spool is larger than the radius at the beginning of normal-sized spools.

Have it sitting on bearings on a custom designed holder.

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Just a quick update.

gr5 was right, changing the flow to 115% in UM2 filament settings and to 115%-120% once the print starts seems to have fixed the problem.

I am in the middle of the large print so I cannot multiply/combine all of those into one to retest but it seems that my flow needs to be increased by over 30% to give the best results.

This also agrees with something I observed earlier. Simplify3D would calculate that I need, say, 1000g of filament for object 1 and another 500g for object 2. Previously the 2.4kg spool of XT would last 2x object 1 + 1x object 2 and there will be quite a bit of filament left. That is 2.5kg + lots of leftover material out of 2.4kg spool. The filament size seems to be correct.

I will retest with cura but I am sure that it was doing the same when I was printing with PLA.

Also of interest is that the black blobs completely disappeared. I had quite a few before (with XT only) but none now. Seriously, not a single one in over 100h of printing. No other parameters apart from the flow have changed.

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