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Bad walls


Kibox

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Hi there,

 

I must admit, I am not using an Ultimaker printer, but I built one myself. I am using the wonderful Slicer Cura, which (as I think) is the best one on the market.

 

Overall, my printer prints beautifully, but lately, I discovered a new problem. I had not printed in a long time and I am not sure when this problem first arose. I am printing quite a complex part, about 19 hours to print in total (picture 2). I am using a bowden extruder. Some parts of the model are printed really well and smoothly without any reason for complaints. But some parts (especially the ones with holes in it) are printed with missing material. The wall thickness also seems to differ. I would suppose that it had something to do with retraction, but reducing retract / prime speed did not solve the problem. Also, I do not understand, why this problem occurs only on certain parts of the model. Picture 1 shows another model with a similar issue, but overall much better quality.

 

I tried to reproduce and isolate the problem (picture 3) by printing a very thin wall (0,5 mm). Here it can be seen clearly that somehow some parts of the wall are printed thicker.

 

I am still doing testing, but I feel a little bit lost here. I hope you can help.

 

Details:

Material: PLA

Print temperature: tried 200 °C, 210 °C, 220 °C

Print speed, outer / inner wall speed: 30 mm/s

Infill speed, travel speed 40 mm/s

Small feature speed: 10 mm/s

Small feature max length 20 mm

Retract amount 6,5 mm

Retract / prime speed 20 mm/s

Layer height: 0,2 mm

Nozzle diameter 0,4 mm

 

Kind regards

René

print_issue1.jpg

print_issue2.png

print_issue3.jpg

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    Posted · Bad walls

    I did some further testing. I also printed a "normal" part without any holes and it looks quite good. So I would assume that the problem is not a mechanical one of my printer, but of the slicer settings. It does not really look like the classical underextrusion, but I am not sure. I allso attached the G-Code of the example bad part, maybe someone would like to test if they observe the same behaviour?

    example bad part.jpg

    example good part.jpg

    Test_Underextrusion4 v2.stl CFFFP_Test_Underextrusion4 v2.gcode

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    Posted · Bad walls
    15 hours ago, Kibox said:

     

    print_issue3.jpg

     

     

    Ok this seems to be another problem. I printed a wall that is 0,5 mm and the nozzle size is 0,4 mm. So the extruder printed the first line ~0,4 mm and had to place a second line with 0,1 mm next to it. Therefore it had to adjust the extrusion speed. It seems that some calculations interfere with the small feature setting. So when a small feature is printed, it slows down the movement. When it now calculates the extrusion speed, there seem to be slight differences to the parts that are not small feature. So the problem with this part seems to be unrelated to the wall problem of this topic.

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    Tip: Instead of *.stl and *.gcode file attach the cura project file [strg]+s. It includes all information one need to review print settings from Cura. The file have the extension *.3mf. It will be as well extremely helpful to know what kind of printer are you using and what Cura version you are working with.

     

    Good is relative (post 2). I still see a lot of imperfect walls in the last two pictures. Looking to the wall pattern I do think you should do a pid tuning for your bed too. But it can be everything, from print speed, mentioned  wrong PID, retract settings, wrong tuned in extruder stepps up to wet filament.

    Make a print with all (!) speed entries set to 30mm/s (except travel) and 100% flow

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    Posted · Bad walls
    On 3/12/2022 at 1:53 PM, DivingDuck said:

    Tip: Instead of *.stl and *.gcode file attach the cura project file [strg]+s. It includes all information one need to review print settings from Cura. The file have the extension *.3mf. It will be as well extremely helpful to know what kind of printer are you using and what Cura version you are working with.

     

    Good is relative (post 2). I still see a lot of imperfect walls in the last two pictures. Looking to the wall pattern I do think you should do a pid tuning for your bed too. But it can be everything, from print speed, mentioned  wrong PID, retract settings, wrong tuned in extruder stepps up to wet filament.

    Make a print with all (!) speed entries set to 30mm/s (except travel) and 100% flow

    I did not know that I could save the project. Thanks for the advice!

    CFFFP_Test_Underextrusion4 v2.3mf

     

    Before I set the print speed equally to 30 mm / s, I did another test and disabled retraction. There the problem still persists:

    313805398_noretract.thumb.jpg.1abe53690d46f678e875a6f9daaee0fc.jpg

     

    I think my printer might have problems, if the extrusion speed changes too abrubtly. I set all the print speed to 30 mm / s and changed small feature speed to 50 %. Before, Small feature speed had been 10 % and I think that was probably waaay to slow. now it looks like this:

     

    163282514_smallfeaturespeedchanged.thumb.jpg.6ae267840f9698fca57a9e18b6595ae3.jpg

     

    Of course, the print is less than good, I think the edges show signs that the fans are not cooling the extruded material quickly enough, but I will adjust the fans later and this is not such a big problem. I find it curious, that there are visible changed in the thickness of the part next to the holes. But so far it looks way better than the first part I posted.

     

    I am going to print a bigger model now and see how this turns out with 50 % small feature speed.

     

    I will work on the PID tuning later.

     

    I am using the newest Cura Version (4.13.1).

    And because you asked about my printer:

    own_printer.thumb.jpg.691aea1011d07b0e8d93f38b8e9ceb74.jpg

     

    It has the electronics of the Geeedtech Prusa I3 Pro W (I guess the cheapest printer there is on the market^^), but I replaced most of the original parts. It has a 2 in 1 bowden extruder and the firmware has been upgraded to the newest available.

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