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Top layers over and under extruding in the same print


Sonic3389
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Posted · Top layers over and under extruding in the same print

Hi Guys,

 

Recently switched from S3D to Cura and getting vastly better prints now, PETG stuff came out just amazing - however on PLA I've had a bit of an issue.

 

I print on 1mm nozzles as my prints are always large functional parts and I had something I've not experienced before, in the same print one top layer was over extruded and another was under extruded. I have attached an example, you can see the upper part of the piece is over extruded, and the lower part is under extruded. I can't see any settings in Cura that might help with this, does anyone have any suggestions please?

 

I'm printing on a Creality CR-10s Pro v2.

pla.JPG

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    Posted · Top layers over and under extruding in the same print

    Post the Gcode and I'll look at the E numbers.  In the mean time, check your Z mechanicals (coupler, threaded rods, wheels, X beam is rigid, etc.) .  Extrusion problems like that can happen when the Z gets dirty or hangs up instead of moving to the new position.

    Did you have Z-hops enabled?

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    Posted (edited) · Top layers over and under extruding in the same print

    Thanks GV,

     

    I've attached my gcode - it's not exactly the same as the object in the photo as I don't have that gcode any more, that was a smaller test print of a larger object. I've attached the gcode for the new object though the Cura settings are all exactly the same. Just the object is longer now. 

     

    Z-hops are off, I've not touched this since installing Cura, the x-axis is solid, no wobbles or jams in anything there. I'll take a look at the Y axis rods etc though in general the print quality is perfect, the sides of the prints are 100% fine its only the top layer(s) I'm having this issue with.

     

    Markus.gcode

    Edited by Sonic3389
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    Posted (edited) · Top layers over and under extruding in the same print

    I don't see anything in the Gcode file that would account for that.  Your flow at 20mm/sec print speed is only 6.4mm³/sec and so you aren't stressing the hot end.

     

    The Skins account for 35% of the plastic used in the models.  The overall amount of filament calculated by the length of the extrusion moves in the Gcode file came out to 100.5% of what Cura said it would be.  Your photo shows under-extrusion on the order of 20 to 25% and with 35% of the print consisting of Skins, that amount of under-extrusion should have shown up in the analysis.

     

    Looking at layers from the side is not a good way to judge over/under extrusion.  It's the skins that tell the real story.

    When I zoom into your first image I do believe I can see that the layer below the top skin is also under-extruded.  I happen to have a microscope and looking at a print through it taught me what I was really looking at.  A magnifying glass can work as well.

     

    I see you had the flow in Cura set at 99.4% which is close enough to 100% for me.  You may want to go back and double check the E-step calibration on your printer.

     

    Edited by GregValiant
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