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snowygrouch

Gap between infill and outer wall

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Hi,

Been printing for 2 weeks since building the machine, printing a bracket with 100% infill.

Two questions....

1) I turned on raft (using PLA) because the print seems to not extrude enough plastic for the first

say 100 mm travel, so by using a raft it comes out nice and even by the time the main object appears.

Is there a better way to deal with that ?

2) On the bottom couple of layers (so above the raft, I`m talking about the actual part here), there is a gap

between the infill and inside edge of the outer wall. Ideas on how to fix that ?

Picture attached.

Thanks

Calum Douglas

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The first problem is most likely that the printer head is empty, you could modify the start.gcode to get more initial extrusion, or enable some more skirt lines.

The outlines not touching the infill is most likely a problem with belt tension, it's quite common on the UM and easy to fix with some extra belt tensioners.

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Ok thanks guys,

I have printed tensioners on the x-axis, (the wave type) but cannot fit them to the Y-axis because

they foul the rod-blocks and also rub on the inside face of the top panel. So still working out what

to do about that one.

I will check the infill overlap parameter when I get home from work, but I think I did stick that up a bit.

So looks like belt tension.

But why does this only occur on bottom couple of layers ? Once it gets into it a bit, the infill merges very

well with the outer wall...? Hmmm

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I too am having issues with my infill not touching the perimeter. My belts are very tight so I don't think that's the problem. I have not tried any software other than Cura though. I suppose I should try something like Slic3r just to confirm that it's not my printer. My infill overlap % is set to 15% so I suppose I could try increasing that. I'll have to do some more tinkering.

-Matt

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Are you sure your short belts are also tight? People tend to forget those. You could also have a slipping pulley, so make sure those are tight. And finally, you could have slipping filament, causing under-extrusion. But this should be very visible on your prints as the 2 outer walls also won't touch.

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Would loose belts cause under-lap on one side of the infill (with the other side overlapped)?

I get such an issue every now and again, though I know that my long belt tension is on the low side. The steppers shouldn't be slipping though because the layers are consistent one after the other.

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Would loose belts cause under-lap on one side of the infill (with the other side overlapped)?
Yes, this is because loose belts cause a backlash effect, which causes the outlines to be moved depending on the previous movement direction.

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Are you sure your short belts are also tight? People tend to forget those. You could also have a slipping pulley, so make sure those are tight. And finally, you could have slipping filament, causing under-extrusion. But this should be very visible on your prints as the 2 outer walls also won't touch.

Sorry for the delayed reply. Yes, I'm sure the belts are quite tight as I recently updated to new belt tensioners and since they required lowering the entire gantry system I decided to go nice and snug on the belts.. if anything they may be too tight.

I'll have to double check my pulleys but I would think I would see this as an irregular pattern of lines that aren't quite where they should be. In my case the infill doesn't touch the wall all the way through the part (it's a flat part that's basically just an extrusion of a 2d shape) You can see right through the part on some areas where the infill doesn't touch. I'll see if I can post a picture as that might help make it more clear. I've had my fair share of underextruding and I don't think this is it. Usually the outside layers are all whispey and look "foamy" when I get under extrusion. I'm not seeing that in this part.

-Matt

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Here's a picture of the issue I'm seeing.

IMG_20120915_175630.jpg

I think this is really a slicing issue. When I looked at the toolpath in cura it doesn't appear any attempt was made to fill in the area between the inner and outer perimeter of that circular feature. The other gaps (seen around all the letters) aren't as obvious when looking at the toolpath but clearly it's not an under extrusion problem since the perimter walls are pretty much perfect.

Any ideas? I can send you the STL if you want to try to reproduce the issue I'm seeing. I'm printing at 0.2mm layer height and 50% infill. In fairness, I did scale down my model by 0.75 to reduce the printing time. I later tried another print at full scale and 100% infill and increased the infill overlap to 20% (up from the default of 15%) in the expert settings. The print looked better but there were still areas that did not receive infill.

-Matt

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Here's a picture of the issue I'm seeing.

IMG_20120915_175630.jpg

I think this is really a slicing issue. When I looked at the toolpath in cura it doesn't appear any attempt was made to fill in the area between the inner and outer perimeter of that circular feature. The other gaps (seen around all the letters) aren't as obvious when looking at the toolpath but clearly it's not an under extrusion problem since the perimter walls are pretty much perfect.

It is a known issue (if you have rules out belt slack and good enough infill/overlap) with cura and slic3r. less so with cura, more so with previous releases of slic3r.

you can try a couple of things: reduce the number of outlines or the wall thickness, to trigger cura to use infill at that point. or increase the wall thickness and reduce the nozzle size until you see an extra inner loop filling the gap.

kisslicer doesn't have this problem, and I can't remember seeing this issue from netfabb, so you could give those 2 a try.

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Thanks for the reply. I tried to slice and print with kisslicer using the configuration files that have been floating around but it had retraction enabled and I started stripping filament so I gave up on that last night. I'll see if I can adjust the settings (turn off retraction) and see what happens.

I would love to try netfabb but can't bring myself to drop €150.00 just to see if it works. I can't seem to find a eval/demo version that will let me actually print. Maybe I'm missing something though :) But either way, I guess it's good to know I'm not the only one with this issue. I'll continue to tinker with cura settings to see if I can make this type of print work. I really prefer the integrated workflow of cura vs slicing in some other tool then printing with printrun.

-Matt

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