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UM1 looks like under extrusion?

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I love my UM1, but it's not happy and I could use some advise on getting good prints again, I think I am having under extrution.

FYI just recently I had to switch to the "spare" hot end wire to correct a MINTEMP error fail. and now I think I am having under extrusion. please look at these pictures and see if you agree.

so far I have, quadruple checked the filament diameter, watched the printing temp on the LCD and that seems fine, bowden does move a bit on retraction but I don't think any more than it used to.plus one of my test prints has no retraction. checked the extruder tension screw..it's tight and ~11mm.

test print, UM1 is this under extrution?

bottom, UM1 is this under extrution?

top, UM1 is this under extrution?

test towers UM1 is this under extrution?


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The issue with the bottom of the print looks more like a bed leveling problem to me. You do seem to have some poor finish quality on the top surfaces too sometimes though. What infill setting are you using, and how thick are you making the tops/bottoms?

Is the roller wheel in the extruder in good shape? Can it rotate freely? Does the filament in your bowden tube have clean, uniform teeth marks in it, or are there any signs of the plastic slipping or getting chewed up?


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70mm/sec X .2mm layers X .4mm nozzle equals 5.6 cubic mm/sec flowing through that tiny nozzle.

That is doable with the UM1 but you will definitely get some underextrusion as you can see in *some* of your photos.

If you raise the temperature by 10C (I like to print at 240C when I print this fast as at 240 the PLA flows more like honey than toothpaste) it will help quite a bit. You don't mention what temperature you are printing at. Or you can slow it down a bit to say 40mm/sec. Or you can print thinner layers at .1mm.

The bottom layer was probably printed much slower and has more to do with leveling as Illuminarti says. If your first layer height is .3mm and your leveling is off by .1mm then you would get 33% over or under extrusion.


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Increasing flow to 107 was also smart - this compensates for slipping at the feeder. The feeder will slip about up to about 10 or 15% before it fails completely and starts grinding the filament to dust. Each brand of filament is different regarding how much it can take and spring tension matters a bit to keep from grinding too much but basically 5.6 cubic mm/sec is doable but approaching the limits - just keep that head hot. Max print volume is closer to 10 mm^3/sec on both UM1 and UM2.

I have an alternate nozzle of .65mm diameter that works much better when printing fast. They cost something like $5 on ebay. Illuminarti *might* sell you one as he made some but he is more expensive than the ones from China.


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thanks for the feed back, here what I have found based on your tips.

1. I think the plastic wheel has a dent, could this cause slippage?

2. The filament does not look like it's been ground up, but every so often I see lighter (shallower) teeth marks.

see photos. oh and I was printing at 220degrees.

roller dent

pfilament gearmarks


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