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pm_dude

Irregular gaps on top/bottom shell

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Hi,

It's been a while since I have posted for an issue but I cant seems to get that one out anymore.

Since a few weeks now I have been seeing this effect on top/bottom shell where I get very irregular gaps or sections with lines not touching even at low speed. These are printed with:

colorfabb white (same results with 2 different spools)

30mm/s

0.4mm nozzle

0.15mm layers (same thing with 0.1mm layers)

same result between 205C and 220C.

 

IMG 20150126 201053

IMG 20150126 201039

 

I have to raise the flow to 115-120% in order to not see those and unfortunately that cause the places that are usually ok to be over extruded.

I also seems to be starting to have shell perimeter not touching. This gab is between the inner shell and the outer shell.

I checked the short belts and they are fine (made them tight). The print head is easy to move with a finger and the rods are all well oiled. The nozzle and teflon are in good condition and I have completely cleaned, burned, polished the nozzle back to try to fix the issue with no luck.

Could this be a feeder problem (I have Roberts feeder)? The marks on the filament seems very constant and no sign of sliding/grinding.

Any thoughts are welcome :)

 

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14.12.1 I tried with 15.01 RC11 as well. Even stuff prepared with 14.07 do the same.

Firmware is still on 14.07 I'll update on 15.01 when its stable.

Last night I removed the X and Y stepper motors, oiled and tighten the screw. I noticed a play or about 1mm on the X axis rods (front and back rods) that I corrected. I did my usual test to validate tension on the feeder and everything is fine.

I'll have to test with a different color.

 

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I saw the exact same thing on a print I did a few days ago. I thought it was due to some things I was experimenting with and didn't think much about it (more than being disappointed it looked so crappy). IIRC I used 15.01-RC8, 0.2mm, 50mm/s, 225C and Colorfabb white.

 

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Just a random thought... maybe try it again with the same filament but with another slicer? Just to see whether it's Cura or the printer?

I've always had more issues with white filament than any other colour I've used. I wonder if that's to do with the particular colorant ?

 

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Is there any other free slicer? I dont see how a different slicer will make a difference on calibration parts I sliced in the past and worked for every filament I used it with.

Its not the first time I read that white is a difficult material to use and yet these past weeks have been the first time I actually see this because I never had other part with so wide top shells.

 

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So I made more tests tonight. Sorry Chris I could not test other slicers yet.

My test was made with a cylinder of 50mm wide and 2mm thick, 100% infill, 50mm/s, 0.1mm layers, Colorfabb Dutch Orange (and I did it with white also last night).

1. The first half was done at 210,215,225C and I did not really see much difference except that the outer shell would contact better at higher temp.

2. Then I switched to 230C. When the temp was stable I was still seing the same issue but with a little less occurence.

3. Then I switched the fans off (I have zetoff shroud) and the nozzle temp raised from 230C to 242C before dropping to 222C and stabelizing took a really long time (more than 3-4 minutes). Once the nozzle temp was stable (constant ~1-2 deg variations) the surface was better but was still having the gaps here and there for a few strokes which were not really in sync with the temp variations.

4. I then set the bed temp out from 60C to 0C and then I started having a more uniform surface even if previously the nozzle temp was stable it could not achieve that quality, I still have one or two strokes per layer that are not perfect but its not even comparable. Also the side wall of the cylinder is perfectly aligned from one layer to the other which in my latest prints I can tell they are not.

5. I then set the fans on again and it took for ever to get stable temp (...zetoff shroud). The surface quality came to a 50/50 between without fans and without bed and with only the fans off. In other words in my case I get better quality without the heated bed than without fans.

This bring me to the conclusion that:

- I need to look at the best way to set the PID values for the nozzle temp (bed near nozzle, fans on, then do the PID commands)

- I'll make a change to the zetoff shroud to include the following:

 

  • Find a thin metal plate I can drill holes in to protect the nozzle from the air flow like the OEM fan mount.
  • Change the design to support that metal plate properly

- I need to update the Firmware and to the tests again.

- Bang-Bang mode on the heated bed need to be looked into if issue persist.

This seems to come in line with issues @Dim3nsionner had for a while with outer shell consistency from layer to layer.

 

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I think you've nailed it pm-dude. Both the zetoff and venkels fan shrouds have 'open bottoms' and at nozzle heights close to the bed the backwash from the fans end up cooling the heater block. At heigher head heights this doesn't happen as much - unless you're printing large flat surfaces... I should have thought of that - apologies!

Most likely the other slicers won't help at all with this, but they're useful to have around. I've found KISSlicer is pretty good at generating supports - so that may be useful at some later date :-)

 

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On the filament side I do find white more different than others rather than difficult. I use Faberdashery white and it seems to flow thicker (cannot think of another way of describing it) than all my other filaments. So I print it at least 5 degrees cooler, even up to 10 degrees.

On the Colorfabb Dutch orange, which I have used a lot, I think that if you need to print .100 & 50mm/s at a temp higher than 210 then you are probably masking a problem somewhere.

 

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I've been experiencing the same exact problem for a few weeks now and still don't have a clue what to do.

Eventough my teflon coupler has been replaced 2 months ago, I put in a new one, but not even that helped. Aside from that I did everything you did as well. Tightened the belts, oiled the rods and the leadscrew, cleaned the nozzle and the feeder, calibrated everything just to be sure. The only difference I can see is that I'm using the stock feeder. Aside from that our cases are identical.

I'm experiencing this with all my Colorfabb filament. Most of the spools are at 70-80%, so I'm not even close to the inner coils (not that it'd matter at printing speeds of 40mm/s).

The weird thing is that all of these spools (Dutch Orange, White, Ultramarine Blue and the Blue Gray) printed perfectly when I unpacked them.

I'm printing with the rest of my Faberdashery filament now, which seems to reduce the problem significantly. I don't need those higher temps or increased flow anymore. The problem isn't completely gone, but basically reduced to 2-3 slightly underextruded lines per surface. The walls are much cleaner and more even as well.

Have you tried any other brand besides Colorfabb? Just to get a comparison. Are your walls kind of "wobbly" and uneven as well?

I just don't get how this could happen more or less over night. I store my filament in a dark, dry room and some of the spools are only 1 month old. Plus, like I said, they printed fine in the beginning. The diamenter is unchanged, 2.84-2.86mm.

Going back to Faberdashery is an option I'd like to avoid as I still hate that loose filament, even after going almost a kilometer. That and the fact that I have 12 spools of Colorfabb filament... which I'm now too afraid to use.

The one thing I didn't check or exchange is the bowden tube. If it's a frichtion problem that might explain why the Faberdashery filament is less problematic (as it's much smoother and harder).

 

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Going back to Faberdashery is an option I'd like to avoid as I still hate that loose filament, even after going almost a kilometer. That and the fact that I have 12 spools of Colorfabb filament... which I'm now too afraid to use.

The one thing I didn't check or exchange is the bowden tube. If it's a frichtion problem that might explain why the Faberdashery filament is less problematic (as it's much smoother and harder).

 

The loose faberdashery filament has a natural curve to it (as so far supplied) that more closely follows the 'general' curve of the UM's bowden than the tighter coiled filament supplied on spools does, so there's less effort spent by the feeder in having to overcome the force spent in pushing ('straightening') a more tightly curved coil into following the bowdens larger curve. Faberdashery are now supplying filament on spools though, but personally I'll be sticking with the loose stuff.

I've tried pushing loose faberdashery filament by hand through the bowden and it's notably easier to push through than the more tightyl coiled spooled filament was.

Both times, these were filaments that had already been through the feeder so they both had the hobbed gear tooth marks on their upper surface, i.e that surface which rubs the most along it's travel in the bowden. Just as well the teeth marks appear there, as I suspect that will also help in lowering friction rather than a smooth surface sliding past another smooth surface ?

 

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pm_dude: My original UM filament behaved like that from the day I unboxed the printer. Did yours print fine before all this?

I just don't understand how this turned into the current problem so quick. I've used up 3 spools of Colorfabb so far and, most importantly, the 5 spools the have that problem right now were great until this point.

Regarding extra friction from the spooled filament in general: After going through the feeder my CF filament isn't any more coiled than the loose FD material.

Just to make sure the bowden tube isn't the problem, I ordered a new one for testing (PTFE this time). After all I already went through roughly 1600m material if the printer stats are correct.

 

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Do you have horizontal banding on your prints? I mean more than the first prints?

I have the impression that the heated bed is causing more power fluctuations on the nozzle over time.

As mentioned before when putting the heated bed off the gaps reduces and so does the horizontal banding.

http://umforum.ultimaker.com/index.php?/topic/6907-horizontal-banding-on-um2/

 

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Chris, I used to run them at 100% at a height of 0.5mm or 1mm. But since this test I'm capping them at 50% in the material settings and have less issues. I haven't done overhang heavy prints or a lot of prints with bridging though.

PM

 

I think that may be too fast, especially at low head heights? Have you checked the nozzle temperature when the fans start up? Does it hold it's temperature ok?

 

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The fan starts fairly slowly. at 0.1 layers it give plenty of layers to start and the temp is sort of stable (+-1-2 deg variations).

Since I changed the rear fan for a more silent one, I can now hear the side fans making a really annoying sound on the first few layers layers until they get to at least 30%. I'll need to change those as well at some point. The good news is that those are 12V fans and I have plenty of those at the local electronic store.

Now I just need to get that metal plate to protect the nozzle from the air flow.

 

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