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Avoid the print to start each layer in the same area


CarlosG

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Posted · Avoid the print to start each layer in the same area

I have some issues due to stringing and I think temperature, speed and retraction are not the problem.

I heard in some slicers you can define that each layer starts in a different (random) area, so the defects don´t show up in the same area of the part.

 

Do you know how to do it with Cura?

 

Thanks

IMG_20180131_204603.jpg

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    Posted · Avoid the print to start each layer in the same area

    Usually you fix this by lowering the temperature which makes the pla more viscous so it leaks less.  And also slowing it down so the pressure in the nozzle is lower so it leaks less.  I recommend playing with these 2 parameters in the TUNE menu until it stops stringing or until it strings much less.

     

    Actually the print on the right with the least stringing looks the worst - something wrong with the Z I think where it didn't move the right distance and it then over extruded some of the layers - what kind of printer is this?  I think it has a problem with the Z axis sticking.

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    Posted · Avoid the print to start each layer in the same area
    12 hours ago, gr5 said:

    Usually you fix this by lowering the temperature which makes the pla more viscous so it leaks less.  And also slowing it down so the pressure in the nozzle is lower so it leaks less.  I recommend playing with these 2 parameters in the TUNE menu until it stops stringing or until it strings much less.

     

    Actually the print on the right with the least stringing looks the worst - something wrong with the Z I think where it didn't move the right distance and it then over extruded some of the layers - what kind of printer is this?  I think it has a problem with the Z axis sticking.

     

    Actually the less retraction I set, the best part quality I get but with lot of stringing.

     

    From left to right:

    LEFT: Retraction: 30mm/s 3mm  210ºC

    MIDDLE PART: Retraction: 35mm/s 6mm  205ºC

    RIGHT: Retraction: 50mm/s 8mm  210ºC

     

    When I added too much retraction stringing was almost eliminated but I got poor quality (like under-extrusion).

     

    I can try to lower temperature to 200º and print slower, thanks for the advice.

     

    Going back to one of the initial question, how can I set in Cura to avoid starting each layer in the same area and enter/exit the part in the same positions?

     

    Thanks again

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    Posted · Avoid the print to start each layer in the same area

    I wouldn't mess with the default retraction distance (4.5 on um2, 6.5 on um3) as that is basically perfect.

     

    You want it to completely remove all pressure within the bowden (have the filament resting on the bottom of the arc) but not actually lift any filament out of the nozzle.  If you retract too much then the filament moves upwards and air goes into the nozzle.  Then that bubble rises in the nozzle and heats and expands and overextrudes for several seconds (long after the retraction sequence is over).  Then a little bit later the air is forced out and you get underextrusion as well.  It's just a mess.

     

    So that explains exactly what I see.

    Make sure the bowden at both end is secure (doesn't move up and down by say 1mm on every retraction).  If the bowden is secure then the default retractions are as good as it gets.  If the bowden wiggles up and down by 1mm then either fix that or increase retraction by the exact same amount (1mm).

     

    Instead drop the temp to say 180C and the printing speeds all to 30mm/sec and you should see some great improvements in stringing.

     

     

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