I have 2 problems that are related, but opposite. I'm periodically underextruding.

3D Printing
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I have 2 problems that are related, but opposite. I’m periodically underextruding.

I’m noticing periodic slippage and skipping steps in the extruder of my Printrbot Simple.

I’ve marked the bearing with lines (using a marker) and can see that sometimes the bearing isn’t turning (and sure enough, the line thins out) but only for a second or 2 and then it goes again.

I also sometimes (and this is independent of the first symptom) hear and observe the stepper skipping steps.

I have cleaned the teeth on the hobbed wheel, and increased the tension, but there’s still period stalling of the feed.

I have increased the current to the stepper, and it now runs much warmer, and there are still times when it skips steps.

I’m printing black PLA at 195C.

Thoughts?

2

A partial clog, maybe? Got some pictures?

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Partial clog might explain the skipping steps, although it’s so brief that it barely shows up in the prints. That happens somewhat randomly.

The “slipping” seems fairly rhythmic - I’m wondering how long the hobbed gears last. As in, I wonder if some of the teeth are worn and not biting as well?

I just switch to a new spool of filament. We’ll see how that does.

4

Oh, and as mentioned - it’s black. Got to be the hardest thing to get a good picture of…

5

I second the partial clog idea. Also, make sure the extruder motor isn’t overheating. That can cause the clicking and skipping too.

6

My ubis is 1.5 years old. Never had it apart or changed the tip. Am scared it will break if I try removing the tip. Suggestions?

7

Warm it up first. It should come apart easier.

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Try a cold pull, (heat to 50c), pull out filament, snip off 3 inches.

9

Make a dragon

10

If you had your printer for about a year, your bearing might be dry and even stoke, check all the bearings in you printers head,

11

@Alexander_Pritchard Kinda tried a cold pull just now (switched filaments again). Could not pull filament out until head reached ~100C and then the filament just snapped off inside the head.

I did crank the heat up to 213 and it seemed to extrude very smoothly. Maybe this PLA (black) just needs to run hotter…

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@Alex_Wiebe ​ Sounds like brittle filament.

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I had some PLA that just printed better at over 210C. It really just depends on the actual composition of the filament.

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@Alex_Wiebe ​ You might try feeding some manually and see how hard it is to push through

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100C is a little too low for a successful cold pull (from my experience). Try raising it a bit more so it won’t break off.

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@Alexander_Pritchard That might work - except I don’t have a base feel for normal back pressure.
@Keith_Applegarth I printed a couple small parts with some left over black PLA from a different supplier, and it seemed to work better. Might have to re-slice at a higher temperature. (Would be nice for host/firmware to support a temperature variance so you don’t have to reslice just to tweak head temp).

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@Alex_Wiebe Just see if you have to push hard, my pla goes though with a slight effort at 200c

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Just found out that Repetier Host lets you adjust the temperature on the fly. I was printing at 195, resliced and started printing at 197 (probably too small to make a difference), then saw the “slider” on the temperature gauge in RH. Bumped it up to 203. The bearing is still stalling periodically.

I have ordered a new hobbed pulley to make sure I get a good bite, and a new nozzle. Printrbot recommends changing the nozzle every 6 months - not sure how many hours or meters of filament that might be. I’ve run almost 10kg through the original extruder and hotend.

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@Alex_Wiebe I would grab yourself a new bearing while you are at it, that will also probably help.

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So while waiting for parts, I’ve continued to observe (when around) and tweak. Running the black PLA 5-7C hotter (203 vs 195) seems to reduce the problem almost to the point where I’m wondering if it is happening or not. The parts I’m printing don’t have a lot of fine detail requiring retract/prime steps, so I’m not sure how bad the higher temps will affect stringing, but for now I’m printing without the extruder clicking and the bearing seems to keep on turning.