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andwew

UM2 Motor Slippin'

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Hi all-

Quick question.

Much like everyone else I am having under extrusion motor slipping issues. Especially on the first layer. :mad:

I'm doing my best to fix it by getting a better leveling of the bed and printing thinner (for that first layer), hotter, and slower. Seems to work... Sometimes...

My prints for the most part turn out pretty nice. But I wanted to ask how much motor slipping is too much motor slipping over the duration of a print?

I don't think I can spot it as an issue in the print, but it still slips throughout occasionally. Is this something that is suppose to be avoided entirely? i.e. bad for the printer over a period of time? Or is the occasional slip (once a layer-ish) to be expected?

Thanks guys! the community here is great.

 

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You want to print a thicker first layer if it is slipping - in other words your bed is a little too close to the nozzle if the first layer is causing the feeder to slip.

Slipping isn't bad for the stepper. There is absolutely no harm. Steppers have electromagnetic coils which create magnetic fields. There are no gears or anything that are skipping teeth - it's just like if you have two fixed magnets and one moving magnet that likes being near the 2 fixed magnets. When you push the moving magnet to the second fixed magnet it doesn't want to go but then suddenly slips/jumps. That's all it is inside the motor.

Skipping on the first layer is not a big deal if you are printing, say a UM robot where people don't look at the bottom much but if it is say a cell phone cover it is critical.

I haven't had *any* skips for several weeks. They shouldn't be hard to avoid. Especially first layer skips you just lower the bed a tiny tiny bit. Give that plastic more space to seep out.

Skips on upper layers are more of an indication that there is either something wrong with your printer or you are doing something wrong. What temperature/layer height and print speed are you going for? At 230C, PLA you should be able to safely print at 5mm^3/second. At lower temps, lower speeds. For example .1mm layer, .4mm nozzle, 100mm/sec is (can you multiply 1X4?) 4mm^3/sec. Should be doable without any skips at 230C. But not at 210C.

 

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Thanks for replying so quickly, gr5.

Nice to know that wretched sound (that kills my soul a lil everytime i hear it) is not bad for the printer.

I think it's safe to say i just get most slipping on the first layer. On some prints pretty bad. It gets underextruded and rips up layers it had laid down.

Right now I print my first layer at .2mm at 20mm/sec and at 230. The rest of the print at .09 at 40mm/sec. Print bed at 67.

Ever since I moved .3mm to .2mm on the first layer it has helped a little bit.

Those numbers sound good to you? If so, I imagine it's just really getting that bed leveling correct and then eventually building a better feeder and spool holder?

I shouldn't have to readjust the bed after every 10 hour print?

Thanks again. I know this stuff has been discussed hundreds of times...

 

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Hey for the first time after about 20 something prints I got my first perfect slip free base layer! You weren't kidding about the "tiny tiny bit". I stopped the print and tweaked the layer if the motor ever slipped. Eventually an 1/8th of a turn on the leveling screws made the difference. Thanks! let's see how long this lasts :D

 

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Regarding the print settings, if the print looks the way you want it and it is completed in the time you want, it's good ;) Really, there's so many trade-offs and differing opinions on what a "good print" is so it's very difficult to give a general rule.

No, you shouldn't need to re-level very often. For me the only times I've re-levelled is when I've been screwing around with the print head.

I think we've collectively come to the conclusion that the spring in the feeder is a bit too strong to have the tension screw on anything more than its weakest setting (meaning the little indicator dial is all the way up).

And yeah, a little goes a long way. Take out a caliper and measure out 0.1-0.2mm and look at it, it's tiny. That's the thickness of a single layer and there isn't a whole lot of room in either direction for the bed to match perfectly.

 

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Hey thanks LRobertl.

Your "good print" way of thinking makes a lot of sense, especially as of late. So many variables that it'll make your head spin. No time to be an OCD perfectionist. In a few years when we are printing in climate controlled vacuums with no gravity I'll regret having spent so much time fighting this uphill battle.

And I think adjusting the spring on the feeder helped already.

Hopefully, I'll have some prints to show soon.

 

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