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Posted · Flow control in Ender 3

I have lost my best profile in Cura and in trying to get back to a reasonable print I keep encountering a slip in the filament drive every 5-10 seconds the drive slips with a loud click!  I can get it to stop by altering the flow figure in the Ender menu, but how or what do I alter in the profile to stop the slippage?  It seems to do with roo much filament being pushed into the nozzle, but do not know what settings alter this.

 

thank you

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    Posted · Flow control in Ender 3

    There are a lot of things that can affect the extruder "skipping steps".  The number that is involved is the "Flow Rate" in mm³/second.

    If you have a 0.4 nozzle and you are printing with a 0.20 layer height and a 0.4 line width, you should be able to print up to about 150mm/sec Print Speed.  150mm X 0.2 X 0.4 = 12mm³/sec.  That happens to be the upper limit for what my Ender 3 Pro can "pump".  I never print that fast because the machine beats itself up.  The faster you print, the more material is getting pumped through the hot end, and the greater the heat loss of the hot end.

     

    If you are printing at the cooler end of the material's range, then the material will be thicker (more viscous) than if you were printing at the top end of it's range.  You wouldn't be able to print as fast.  The more viscous material just won't move through the nozzle as fast.

     

    Then there is the extruder itself.  Most have an adjustment screw for the amount of tension that the drive wheel puts on the filament.  More pressure means that the filament is gripped harder and can be "pushed" harder.  Too much pressure can deform the filament as it passes through, and if you happen to have a bowden printer, the filament can get kinked in the bowden tube which in turn makes it harder to push through.

    A bowden system requires longer retractions than a direct drive.  Either way, if your retraction distance is too long for the machine setup, it will pull molten plastic up into the heat break where it will harden into an "O-ring" around the filament making it much harder to push through.

    There is also the extruder motor itself.  If it tends to run hot, the heat from the motor will go up the shaft and soften the filament.  Not so much of a problem with Direct Drive, but can be a problem on a bowden machine if you are printing something small that has a lot of retractions.  After the machine has been printing for about 1/2 hour, you should be able to hold any stepper motor comfortably between your thumb and a finger.  If you can't (too hot) then it might be a problem with the reference voltage (Vref) being supplied by the mainboard.

     

    For most printers the stock settings will work fine.  If you are skipping steps using a "Standard" or "Draft" profile, then it may not be a "settings" problem at all, but rather something is going on with the machine.  Taking the hot end apart and giving it a good clean-out can't hurt.  Pulling the bowden tube out and trimming it back 5 or 6mm, and then re-seating it so it's up against the back of the nozzle is normal maintenance.  It's why the bowden tube is considered a "consumable" part.

    "Everything affects Everything"

     

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