Nozzle Dragging Through The Print

Hey Guys,

My Mini Kossel is showing a weird problem that I just cant seem to troubleshoot. So please help me with your inputs.








As you can see from the pictures attached, the nozzle is dragging through the print and is smearing the filament all over the place and the final product is coming out as a disgusting mess. The first layer prints absolutely fine, so does a couple of subsequent layers, so I believe this isnt a bed leveling issue. The issue starts from about the 5th or 6th layers and gets worse as it goes up. Now, I tried using Z-lift, but that doesnt help as this dragging is not just when the nozzle travels, it happens during infill too. Then I figured it might be overextrusion and I reduced my flow rate to 100% which was 105% earlier. I checked my extruder using a length test and it extruded the right amount. I played around with layer heights, changed the slicer from Slic3r to Cura but no luck.

Im printing 1.75mm PLA at 205C with a 60C Heated Bed using a 0.4mm nozzle.
I do not use a part cooling fan.

Any help is appreciated.

... it's massive overextrusion - try to reduce the extruded volume even more ...

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Viktor
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By reducing the flow rate furthur? Or are there any other options that I could tweak?

... it's a combination of speed, flow-rate, nozzle diameter, extrusion width and layer height -- some of the essential values you have to calibrate to get optimal results ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Thanks for the input.
I check my nozzle diameter and it is accurate.

I read somewhere that the extrusion width should be 1.4 times the layer height, do you think this is true? I printed a single perimeter wall with 0.42 extrusion width and 0.3mm layer height. But the actual wall thickness is coming out to be somewhere close to 0.50mm(cannot get better precision with my calipers). So I'm trying to print at a reduced flow rate.

BTW, How does the print speed affect over-extrusion? Should I print at higher speeds so that the extruder cannot push out so much filament and oozing is reduced?

Thanks in advance.

layer heights should not be more than 80% of nozzle diameter... with a .4 that is 0.32 layer heights.

definitely extruding far to much plastic.

Have you measured your filament diameter and entered that correctly into the slicer?
Have you calibrated your Extruder steps/mm? So that when you ask the machine to take in 100mm it really does take in 100mm of filament?

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Dust
layer heights should not be more than 80% of nozzle diameter... with a .4 that is 0.32 layer heights.

I never go bigger than 0.3mm layer heights. Usually print at 0.2mm.

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Dust
Have you measured your filament diameter and entered that correctly into the slicer?

Yes, I have done that. My filament was advertised for 1.75mm, but it measured only 1.65mm. Ive entered the measured value both into Marlin and into the slicer.

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Dust
Have you calibrated your Extruder steps/mm? So that when you ask the machine to take in 100mm it really does take in 100mm of filament?

Yes, in the OP I had mentioned that I had calibrated my extruder. My extruder put out 100.2mm instead of 100mm. But thats probably as accurate as that gets.

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OldJanmi

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Dust
layer heights should not be more than 80% of nozzle diameter... with a .4 that is 0.32 layer heights.

I never go bigger than 0.3mm layer heights. Usually print at 0.2mm.

... this could be a part of the problem - lower height means less space/volume for the amount of extruded plastic!

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

That amount over extrusion shows there is a large calibration issue somewhere

Either the filament dimensions, you say this is correct
the E steps/mm, you say this is correct
the Z steps/mm , make the machine move up and down 50mm and measure it, does it really move 50mm?
X/Z maths is wrong... due to delta calibration issues, incorrect arm lengths, distances and such. If you do a move on just the X or Y does it move the distance expected?
Generate the gcode for a test cube (standard 20x20x10) and post it somewhere (like pastebin) If its a decent slicer it will have a lot of the parameters in the gcode for examination

@Viktor

what up with you today?
You know very well that the slicer takes care of the amount of extruded plastic relative to the feed rates and the layer height, calculating the correct volume regardless of both.
At least it does when everything is calibrated correctly.

Edited 2 time(s). Last edit at 08/13/2018 07:11AM by Dust.

... yes, normally the slicer will calculate the extruder motor speed (or extruded volume) in relation to the set values - so a recalibration has to be done, to get more sound results.

But changing speed and layer height can change the results too, as the amount of plastic, extruded per time and moved length, is not linear ... but this is another "game" ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

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Yes, in the OP I had mentioned that I had calibrated my extruder. My extruder put out 100.2mm instead of 100mm. But thats probably as accurate as that gets.

Edited 2 time(s). Last edit at 08/13/2018 10:38AM by obewan.

Have you tried slicing and printing with a filament diameter of 1.75 as advertised and observed the result yet? Also what kind of caliper are you using, perhaps you could take a picture of it, maybe a picture of how you took the filament diameter measurement? If you incorrectly measure the filament at 1.65 and it is indeed 1.75 that could very well explain the over-extrusion as your printer would be trying to push more plastic (6% more, roughly) than necessary to compensate for the smaller diamter.

Edited 1 time(s). Last edit at 08/13/2018 12:24PM by obelisk79.

@obewan

yes I saw that too....

I decided that its an communication issue... if they really where measuring hotend output length then they would be under extruding by lots, not over extruding.

I had thought of that. But it doesnt make much of a difference at all in the print. Im using a 0.1mm precision digital caliper, so I superglued three stands of filament laterally and divided the value by three.

I guess you can try going to an extreme, like set your extrusion modifier to 50% and check the results. You definitely have a strange issue.

After playing around with the values a bit more, I got a few decent prints:



They are printed at 0.2mm layer height, everything else was with the same calibration settings I used earlier, except I changed my flow rate to 70%. Ive never seen flow rates below 85%. Doesnt this mean the problem is still somewhere else?

And yes, my print dimensions are also correct. I printed a 20mm test cube, it comes out to be 19.8x19.7x20.1mm.

Generally speaking your dimensions are off by enough I'd be concerned. I still think either you've got your filament diameter setting wrong, or your e-steps are miscalibrated. You shouldn't have to reduce your flow rate by 70%

Perhaps try following these instructions and see if it helps get your settings locked in?

[mattshub.com]

Maybe you have a bad/missing jumper for microstep setting?
Extruding with 1/16 or 1/8 and having the wrong filament diameter set sums up to ~70% error

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o_lampe
Maybe you have a bad/missing jumper for microstep setting?
Extruding with 1/16 or 1/8 and having the wrong filament diameter set sums up to ~70% error

Thanks for the suggestion. I will check it again once I'm free.

MatterControl doesnt have extrusion width it works it out for you.