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Feeder skips back every couple of seconds


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Posted · Feeder skips back every couple of seconds

Hello, sometimes when printing I notice my feeder on the back will push the filament up for a couple seconds and then skip back about 120 degrees pulling the filament back too. Sometimes I get under extrusion, however I am not sure if it's linked. Is this a normal thing; is the printer programmed to do that to regulate material flow? Or is this something that shouldn't be happening?

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    Posted · Feeder skips back every couple of seconds

    There are two different behaviours with the feeder:

    1. The feeder skips a step, you will hear a "tick" sound, the filament isn't pulled back, this happens when for a reason or another the feeder can't push the filament as it should. This prevents the feeder from grinding the filament. It can happen for multiple reasons: partially clogged nozzle, bad filament (too wide), worn out teflon, bad print settings (too cold, too fast).

    2. The feeder pulls the filament back, no tick sound is heard, this is due to retractions, they happen on purpose to prevent the nozzle from oozing and dripping on the print.

    What it the behaviour you're experiencing?

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    Posted · Feeder skips back every couple of seconds
    couple seconds and then skip back about 120 degrees pulling the filament back too

    This has many names - such as "feeder skips". It's by design. The current sent to the feeder is purposely reduced such that it will skip back before hopefully before grinding the filament. On the UMO it tends to grind the filament.

    As a result you get gaps for several seconds where it's not printing much.

    The normal fix, for a working printer, is to print a bit slower or a bit thinner layers or a bit hotter. Although it's possible your printer is defective. In general this issue is called underextrusion. Anyway if you have the nozzle hotter, the plastic is less viscous and you can pass more volume of plastic through the tiny nozzle. At lower temperatures you can pass less. It's not recommended to go over 240C for PLA.

    Here are top recommended speeds for .2mm layers (twice as fast for .1mm layers):

    20mm/sec at 200C

    30mm/sec at 210C

    40mm/sec at 225C

    50mm/sec at 240C

    The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion.

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    Posted · Feeder skips back every couple of seconds

    Please also indicate that you have a UM2 and what country you live in on your profile. This information affects the advice you will get on this forum as support options vary from country to country and the names of products and where to get them (like rubbing alcohol) vary also.

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    Posted · Feeder skips back every couple of seconds

    I've got an something special.

    Unleveld bed prints perfect 33 pieces on 1 bed. Leveld bed with 0.1mm print gets always later skip back

    Print layer: 0.2 mm

    Speed: 50

    Retraction 40 4.5

    Temp: 215

    Pla

    Before it printed perfectly also cleaned noozle. may to cold with a correct leveld bed? I unleveld it and later when i am at home i will see if ut works again with unleveld bed.

    @gr5

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    Posted · Feeder skips back every couple of seconds

    If it skips on the first layer then maybe your bed is to close. This would explain why it works with an unleveled bed (assuming it's not to far from the nozzle, so quite leveled)

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    Posted · Feeder skips back every couple of seconds

    It skips only later when speed up with a leveld bed unleved it does work.

    I leveld with 0.1 mm metal feeler gauge

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    Posted · Feeder skips back every couple of seconds

    5a3318c48cd15_Foto23_02.16150241.thumb.jpg.04189cc65f2411b71b006a2354c420f8.jpg

    5a3318c46ecf7_Foto23_02.16150239.thumb.jpg.d686086d4c5e4f0d872f8d9950112b7c.jpg

    5a3318c48cd15_Foto23_02.16150241.thumb.jpg.04189cc65f2411b71b006a2354c420f8.jpg

    I think i found the Error lol. May this also can cause a Skip Back?

    I replace it and bed level

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    Posted · Feeder skips back every couple of seconds

    It could block the bearing or something like that so indeed replacing that piece would be a good idea ;)

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