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Bottom Layer Very Rough


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Posted · Bottom Layer Very Rough

Good evening,

 

I am new to Cura and new to the forum as well. 

 

I have a problem with the bottom (first) layer.  The direction of the extruder is perpendicular to the length of the part.  This looks rough and very busy.  There are "crinkled worms" in a repeating pattern all along this layer as well.  I don't know if they are being formed by the layers above or where.  I used a raft which printed very smoothly.  I am trying to figure out how to make the first layer print parallel to the length of the part.  In order to make the part fit on the print bed, I need to rotate them corner to corner.  I have discovered this has an effect on the pattern of the first (and all) layers.  Because, when I make the parts parallel to the print bed, the first layer prints at approx. 45 deg.  I do not think other slicers I have worked with do this.  I am hoping it is a setting!  I am using matte black PLA printing at 210C and 50d build plate temp.  The part is ¾” square and 11.5” long.

I hope the Cura.3mf file and photos are helpful.  If someone needs more, please let me know!  I really appreciate your help.

 

 

Perpendicular Print.jpg

First-Bottom Layer.jpg

Raft Only.jpeg

Frame Uprights.3mf

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    Posted · Bottom Layer Very Rough

    There are settings for "Line Directions" for Infill, Top/Bottom, Support Infill and Support Interface.  They go into square brackets.  The default for Top/Bottom is [45, 135] which gives you alternating directions at 90° to each other and at 45° to the build plate.  You could put in a single angle as [135] and all the layers would be laid down parallel.  That won't be as strong as a cross-hatch pattern though.

     

    If you have rotated the part 45° you could make the Top/Bottom line directions [0, 90] and they would once again be at a 45° angle to the sides of the part.  You can get fancy with something like [15, 30, 45, 75, 90]  but there isn't actually much of a point to that.

     

    In regards to the initial layer quality...if you look at the walls of the first layer they don't really look flat and welded together nicely and instead of being completely flat they still have a bit of a sausage look.  Either the nozzle is too far above the build surface at the start, or it's simple under-extrusion.

    Have you calibrated the E-Steps (and NOT used a single wall calibration cube!)

     

     

     

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    Posted (edited) · Bottom Layer Very Rough

    Cura bases the "E" numbers in a gcode file on some simple math.  The volume of filament that is pushed by the extruder is dependent on the "Material Diameter" that is entered in Cura.  Most filament is either 1.75 or 2.85 as advertised, but that isn't always true.  A precise measurement of the filament diameter gets entered into the "Printer Settings" (which you must manually load from the MarketPlace).  For example, my Matter Hacker regular PLA is always 1.72 diameter.  It doesn't sound like a big difference, but it would under-extrude by 4% if I had Cura set to 1.75 diameter.

    The printer-processor sees those E-values and spins the extruder motor a number of "steps" to push the amount of filament requested.  A line in the Gcode like "G0 F2400 E100" would cause the printer to send however many steps it thinks are required to push 100mm of filament.  So now we have "Steps/mm" to deal with.

    My Ender 3 Pro came stock with a setting of 93 steps/mm for the E.  After calibrating, it's 97 steps/mm.  Between that 4% under-extrusion and the under-extrusion caused by the filament diameter I would be under-extruding by about 8%.

    I'll explain what I do with my printer.  (If you have a direct-drive you will need to pull the nozzle.)

    • Heat the hot end to 180° to both allow you to pull the filament from the hot end, and to keep the "Cold Extrusion Preventer" in the firmware from preventing the extruder from turning.
    • Pull the filament and disconnect the bowden tube from the extruder.
    • Put the filament back in and snip it off flush with the end of the bowden tube fitting on the extruder.
    • Use the LCD and ask for 100mm of filament.
    • Snip the filament sample off flush with the bowden tube fitting.  Measure the length of the sample as accurately as you can.
    • In the LCD go to the menu with steps/mm.  On my Ender it's under Control/Motion/steps/mm.  Use the formula "RequestedLength / ActualSampleLength * CurrentESteps = NewESteps" and enter the new number in the Esteps/mm menu on the LCD.
    • Do all that over again to check.
    • When you are done - use the LCD menu and select "Save Settings".

    When you do all of that then the "Volume of Filament In" will be exactly equal to the "Volume of Extrusion Out".  By definition that is a Flow of 100%.  If you find that "Hey, these E-steps/mm are exactly the same as they were" then your leveling is off and the initial gap between the nozzle and the bed is too tall.  That has exactly the same effect on the initial layer as under-extruding does.

     

    Edited by GregValiant
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