tobias.l
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local underextrusion

Thu Sep 14, 2017 7:45 am

[EDIT: It turns out, that the heated bed is totally warped in this area.]


Hello everyone,

I have a weird problem with local flow inconsistencys. My first thought was, that the first layer just doesn’t stick to the bed, in this specific area. But even the following layers show a discontinuous flow of material. Some missing spots of the first layer got covered, but also new faulty spots appear.
I actually can see and feel the extruder motor step back, right in the middle of the print. The unwanted retractions only occur between ~X150 and ~X200. The rest of the print looks pretty nice.

-Standart Prusa Settings for PLA.
-Bed is reconditioned with a kitchen sponge and cleaned with Acetone and IPA.
-Same failure with different CAD models, Slic3er PE versions and spools of PLA
-hobbed extruder pully looks ok (and if not, the failure would appear more often and in more areas)

I’m running out of ideas. Hopefully you don’t ;)
Attachments
WP_20170914_07_48_40_Pro.jpg
WP_20170914_07_48_40_Pro.jpg (1.25 MiB) Viewed 214 times
WP_20170913_16_16_31_Pro.jpg
WP_20170913_16_16_31_Pro.jpg (1.48 MiB) Viewed 214 times
WP_20170914_09_13_51_Pro.jpg
WP_20170914_09_13_51_Pro.jpg (1.42 MiB) Viewed 214 times
Last edited by tobias.l on Thu Sep 14, 2017 3:03 pm, edited 1 time in total.

henrik.w
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Re: local underextrusion

Thu Sep 14, 2017 8:14 am

Hello Tobias!

Could you send me the gcode file of the object you have printed in the pictures?
I'll try to see if the problem is situated in the gcode itself.

Could you also print the provided treefrog by Prusa on the spots where you have seen the problem appear? Just two layers would do.

/Henrik

henrik.w
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Re: local underextrusion

Thu Sep 14, 2017 8:21 am

Oh - I forgot - the treefrog has a small footprint for the first layers. Can you just print a slice of the body where it has the greatest area?

/Henrik

tobias.l
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Re: local underextrusion

Thu Sep 14, 2017 3:02 pm

Thanks a lot for your friendly offer, Henrik. The gcode fine is ok. It turns out, that the heated bed is totally warped in this area. I guess this is the main reason.
But it wasn't warped when the printer was new. Is this normal? The machine is nearly one year old now, and it was used a lot.

Does the bed tend to bend over time?

henrik.w
Posts: 125
Joined: Sun Aug 09, 2015 7:48 pm
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Re: local underextrusion

Tue Sep 19, 2017 6:41 pm

I can only guess the properties of the heated bed - but to compare what has actually happened to other plastic things that I own or have seen during a few years - here it is:

*An electric train from the fourties had actually shrinked in length during it's life - and how do I know that? Well it was a plastic shell embracing a steel frame - so the plastic shell looked like a banana.

*A lever to change the gears on a bicycle bent during it's 22 years of life - before i straightened it with a heat gun and some force.

So if you think of it - the heated bed is some reinforced material and combined with copper traces - it could as well shrink/grow with age and temperature. But I do not know if it is prone to this kind of shrinkage/growage.

/Henrik

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