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mcmarkus

UM2 help needed on first printings

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Hi guys,

this is my day 2 with UM2, and I need an help.

I've successfully printed several simple items, and now I want to print one bracelet for my daughter, is one of these items:

http://www.thingiverse.com/thing:195497

everything starts fine, but after a while, it seems to be a problem with the filament extrusion, because the PLA stops to flow out and I heard a "stock" coming from the filament stepper motor.

I've tried 3 times, with this result:

http://i1360.photobucket.com/albums/r658/GinoVannellis/20140109_143358_zps022cb432.jpg

After the printing abort, I've successfully manually moved the extrusion out with the maintenance menu, so there is no nozzle locked issue. I've used normal PLA parameters and one time I've increased the temperature up to 222Deg.

No way.

Where I'm wrong?

Any help will be appreciated.

Thanks in advance,

Marco.

 

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What speed and layer height are you printing at? It sounds like you may be printing faster than the extruder is happy with?

You should also check that the 3rd fan, on the back of the print head is on constantly - even when you aren't printing. It should come on as soon as the printer is powered on.

Filament isn't that sensitive to temperature, btw - don't bother adjusting the temperature by a degree or two; it's ok to change it in 10 degree increments, for the most part. 230 or even 240 should be fine for PLA, especially if you are printing fast.

 

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and I heard a "stock"

 

Maybe it wants to make a financial investment? :)

That is probably the extruder motor slipping backwards (losing steps). Fix this by printing a little bit slower or hotter. Try half the speed you were printing at before (turn feed rate to 50% if you want) and/or raise the temp to 240C.

The printer prints fine at 240C but you may get much more stringing - tiny strings across gaps. So slowing down the print might be the better solution for bracelets.

Also the bottom layer is the hardest because if you are printing it .1mm thick (thickness of paper - very thin) and you are off by just .03mm (1/3 thickness of paper) then the printer is putting out too much or too little plastic by 30%. So if possible try to print the first layer .3mm thick (I think this is default in Cura).

 

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I did not change the speed, so I'm using the default for PLA (100%). I've exported from Cura at low quality.

Well I will check the 3rd fan, but I remember I've seen it working fine.

So, I will try reducing the speed, 70% could be good?

Changing to mid quality on Cura can change something?

About the odd sound I heard from the stepper, is something I've to check?

Thanks,

Marco.

 

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Maybe it wants to make a financial investment? :)

That is probably the extruder motor slipping backwards (losing steps). Fix this by printing a little bit slower or hotter. Try half the speed you were printing at before (turn feed rate to 50% if you want) and/or raise the temp to 240C.

The printer prints fine at 240C but you may get much more stringing - tiny strings across gaps. So slowing down the print might be the better solution for bracelets.

Also the bottom layer is the hardest because if you are printing it .1mm thick (thickness of paper - very thin) and you are off by just .03mm (1/3 thickness of paper) then the printer is putting out too much or too little plastic by 30%. So if possible try to print the first layer .3mm thick (I think this is default in Cura).

 

Great!

Thanks for suggestions. I will try again this night.

I'm happy too because your thoughts guys meet my sensations about the issue - a special feeling is rising with my printer :D

Marco.

 

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I recommend you simply stop using the 'quickprint' settings in Cura. They probably aren't great settings for the UM2, and they get in the way of really understanding your printer.

Switch to the full settings mode (Expert -> Switch to Full Settings).

Then turn on retraction, and set the speed to 40mm/s and the layer height to 0.1mm. Leave shell thickness at 0.8mm (i.e., 2 loops around the outside of the print with your 0.4mm nozzle), and set the bottom/top thickness to 0.6mm (i.e., 6 layers of 0.1mm each).

That should get you started with a nice quality print, and then you can gradually learn from this and learn how to tweak other settings as needed. There are three places where you can change settings - the Basic and Advanced tabs in the main interface, and also the Expert -> Open Expert Settings dialog, but you shouldn't need to touch too much in that one to start with.

 

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In particular, none of the Quickprint settings enable retraction - which is where the printer pulls back the filament a bit before moving to a new area. Doing this helps avoid leaving trails of plastic across the print. For a print like the one you're trying, with lots of discrete parts (usually called 'islands') on each layer, retraction is essential.

Lol. It's a name I've used online for about 15 years now - it's a combination of 'illumination' and 'art' (while being a nod to the word 'illuminati' - the secret society so beloved of Dan Brown novels). It comes from my long-standing passion for, and collection of, large format art holograms. So now you know... :-)

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