material between parts

[DIY3D]

Hi all,

I have a question about a small issue. I printed the parts below and they looks fine but as you can see there is some material between the two parts.
Anyone who can explain what happens during this printen and how I can solve this issue. These parts are printed in PLA at 200C and 0.15mm layerheight

http://1drv.ms/1yKeqUf

Kind regards,
Marco

[ednisley]

The strings look much worse than the usual retraction mis-setting and they're mirrored just like the parts. Take a look at the G-Code using gcode.ws and I think you'll find the printer is doing exactly what the G-Code calls for: extruding in mid-air.

Most likely, you have a non-manifold solid model that's triggering weird slicing issues.

Look for flipped surface normals and missing faces, which are easy to get if you're using a mesh modeler, then update the model to eliminate those errors.

That's better than handing the model to an automatic mesh repair program, because the auto-repair algorithms don't know what the object should look like. They sometimes convert a non-manifold model of the thing you want into a perfectly good model of something entirely different...

[insta]

The strings look much worse than the usual retraction mis-setting and they're mirrored just like the parts. Take a look at the G-Code using gcode.ws and I think you'll find the printer is doing exactly what the G-Code calls for: extruding in mid-air.

Most likely, you have a non-manifold solid model that's triggering weird slicing issues.

Look for flipped surface normals and missing faces, which are easy to get if you're using a mesh modeler, then update the model to eliminate those errors.

That's better than handing the model to an automatic mesh repair program, because the auto-repair algorithms don't know what the object should look like. They sometimes convert a non-manifold model of the thing you want into a perfectly good model of something entirely different...

Ed that's just a high ooze (old, moist filament) with a slow travel speed. My guess is his extruder has a loose set screw on the drive gear so retractions aren't going as they should.

[DIY3D]

Thank you Ed for your comment.

gCodeViewer is an interesting program even though I do not immediately perceive the mid-air extrusion in the Gcode.
What I do see is that the object is not manifold. Around that extra material I see tiny holes so I think I'll treat the object with a stl cleaner program.

Kind regards,

Marco

[ednisley]

high ooze (old, moist filament) with a slow travel speed

I'd expect that to cause horizontal strings, rather than vertical beads built up dot by dot, layer by layer, out there in mid-air.

In any event, we now know the model has problems around the base of the mystery dots. If fixing those holes makes the dots Go Away, then I'd say it was a geometry failure. If they remain, then you've surely spotted the mechanical problem.

[insta]

high ooze (old, moist filament) with a slow travel speed

I'd expect that to cause horizontal strings, rather than vertical beads built up dot by dot, layer by layer, out there in mid-air.

In any event, we now know the model has problems around the base of the mystery dots. If fixing those holes makes the dots Go Away, then I'd say it was a geometry failure. If they remain, then you've surely spotted the mechanical problem.

I see what you're thinking, and you're being much less inflammatory than I am about it

I've gotten the exact same artifacts when I print in Nylon, namely because it's oozing so much. The ooze starts as a booger, then when the hotend is returning the travel ooze catches on the booger, building a 30-degree artifact like that. It's partly the slicer, since the model is so symmetrical it's choosing the same part to jump between them. I'd expect to see the same artifacts if he was printing two cylinders 1-2" apart, especially if a feature like "minimize crossing perimeters" was chosen, in coordination with "aligned seams".

[ednisley]

building a 30-degree artifact like that

Huh. Learn something new every day...

You folks run off much more aggressive stuff in more different plastics than I do; right now, everything around here looks like a magenta PETG bracket.

Marco: you hear that? You've got a loose screw! [grin]

[insta]

Here's an example from a stress test print. The model was 100% manifold and I do not have a loose screw It was just foamy Nylon.

IMG_20150314_185849.jpg (144.73 KiB) Viewed 13367 times

[DIY3D]

Hey There,

I've checked the model in Blender and it is manifold. I also checked the set screw of my extruder and did not find a problem. Perhaps humidity and the quality of the used PLA has been the problem. Last week we had high humidity because of the many rain and the PLA already hung ample time to the printer. Today I printed the same part (with a different color) and here I barely saw the phenomenon.

Thanks for the help, and happy printing

Kind regards,
Marco

[akkrolnik]

I read this post with great interest. I am seeing a lot of strings left when the print head moves from one part of my print to the other. I had already read somewhere else that lowering extruder temperature could reduce this. I did that and I am still seeing the strings. I think I can still reduce the temperature further to reduce this more. My current print is PLA at 205C. Is there a minimum temperature that folks would suggest for PLA? I don't want to go too low and plug the nozzle. The other thing that caught my eye is the comment about the change in material improving the situation.

Perhaps humidity and the quality of the used PLA has been the problem. Last week we had high humidity because of the many rain and the PLA already hung ample time to the printer. Today I printed the same part (with a different color) and here I barely saw the phenomenon.

In my part of the world, its been pretty humid lately. I just swapped to this older roll (first kg of black MG filament sent with the machine). I had it stored in a plastic freezer bag with the desiccant from the new roll that I put on when it was removed. I know this is not the "best" method to keep my material fresh, but at the time I hadn't developed my long term storage plan. Parts are coming for this, but that is a side topic. Hence my question, "Is there anything that can be done to dehumidify a roll of material to improve print consistency?" I'm planning to get a large quantity of silica desiccant beads that can be recharged in the oven for my storage solution. Would it be as simple as leaving the roll in the sealed container until it dries out? Or is there a more active way that I can fix up a roll that has absorbed too much moisture?