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PostPosted: Sun Aug 06, 2017 4:42 pm 
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Hello

I have been printing with the K8400 for almost a year now and have recently encountered a weird problem while printing.
When moving from point to point, the printer does not extrude properly and droops filament. To see a picture, click HERE.
The weir shape within the circles is supposed to be the second perimeter of the hole.

I tried the following:
- Recalibrate the Z-heigt (multiple times), moving the nozzle closer and farther away from the bed.
- Change retraction settings varying from 3 to 5 mm at 60 to 110 mm/s
- Printing speed of the first layer between 10 to 30 mm/s

None of the above helped solve the problem. I suspected it had something to do with either the nozzle-bed distance or the retraction settings, but changing these did not help.

Would anyone know what might solve this problem?

Kind regards
Ruben


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PostPosted: Mon Aug 07, 2017 4:16 pm 
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Check the screw on the pulley that mounts to the extruder motor.
If it's loose this could happen.


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PostPosted: Tue Aug 08, 2017 4:34 pm 
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Dear Ruben,

I would focus on another topic. On your picture you can see long stripes of filament where I suppose that the printhead should only move and not extrude.

If you agree with this interpretation then I would suggest to check the print temperature. If the temperature is too high, the filament becomes too liquid. When exceeding a certain limit it will flow out of the extruder even without explicit extrusion. When moving long distances you can loose a significant amount of material, which needs to be replaced. This will happen during the beginning of the next extrusion, where the lack of material is resulting in a poor printout.

You may test this structure with reduced temperature, but be aware, that the viscousity of the material will increase. If this will lead to clicking extruders, then you have to reduce your print speed. The extruder assembly is no longer feasible to provide the necessary pressure for the extrusion. With the clicking the filament is slipping back, resulting in a similar effect: reduced extrusion due to missing material.

Mabye this can help to overcome your problem.


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PostPosted: Fri Aug 11, 2017 11:05 am 
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Thank you both for the reply! I am sorry for responding this late, my account got deactivated after my original post.

I will try lowering the temperature even more (I was printing at 195C) and check the screw.
Is it possible that the thermistor is not reading the temperature correctly? I am under the impression that for every type of filament (PLA, PETG or ABS) I am printing at temperatures outside the advised range.


Last edited by RubenDenolf on Sat Aug 12, 2017 8:17 pm, edited 1 time in total.

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PostPosted: Sat Aug 12, 2017 7:06 pm 
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Check this post: http://forum.velleman.eu/viewtopic.php?f=59&t=17811

It may give you a sense about thermal control.


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PostPosted: Sun Aug 13, 2017 9:03 am 
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Thank you for that forum post on thermal control, it was a great help! Within a few weeks I will swap the printhead with an E3D v6. Hopefully that way the temperature will be more accurate and I can change the nozzle diameter easily.

I was able to resolve the problem by:
- Bumping up the travel speed from 120 to 180 mm/s
- Lowering the nozzle temperature from 195 to 185C

The screw on the extruder pulley was still tight enough so no problem there.


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