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leon-grossman

About ready to toss my UM2 out the window (extrusion problems) - SOLVED

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OK, I've had my UM2 at my office since just after Christmas last year. When it works, this printer is fabulous.

However, I've had under extrusion problems from the beginning. When my printer arrived, the drive wheel pulley set screw was loose. It's just gone downhill from there.

PLA printing is a sometimes thing when I clean everything out just right and the extruder housing doesn't shed too much ABS plastic then I can get amazing PLA prints. Most of the time, however, the extruder just jams. I'll be trying vegetable oil next to see if that helps.

ABS printing usually works OK but that jams as well. I can currently print at a max of 50mm/sec at 0.1mm without problems with ABS. Anything higher and I get under extrusion.

So, yes, I guess I need to disassemble and clean the nozzle again. that would be great if the nozzle were removable. Instead, it's semi removable but you'll never get the heater cartridge out so what you can do is sort of let it dangle and hope that's enough to get in and clean everything out.

So, to sum up. The nozzle clogs, doesn't play nice with PLA, isn't replaceable, isn't easily cleanable, and the drive mechanism likes to grind up material to send up the bowden tube for later. Of course, you can't get to that to clean it out between filament changes.

I've posted about these problems here before and had lots of suggestions, which I've implemented with no improvement machine operation. In the end, I have a fantastically assembled XYZ axis* with a barely functional extruder and I'm getting royally annoyed.

Leon

(who had intended to buy two more for my company's other offices but not any more)

*Fantastically assembled in that the gantry was mis-assembled from the factory and I had to adjust one of the pulleys so the rod was in the hole and then realign the gantry to be square. It is now fantastic...

 

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Have you replace the white isolator? I'll have someone message you with a replacement if you want one. That part seems to be the most common problem with underextrusion but I'm going to guess only 50% of underextrusion issues are caused by that.

The heater and temp sensor only come out if you remove that long skinny screw that hold them in. If you remove that completely they should slide out with almost zero force.

 

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Leon- I did suffer from similar problems in the beginning. Here is what I did to get things running:

- I only print ABS. If I switch back and forth between PLA and ABS the nozzle will clog at some point. My guess is that residual PLA is incompatible with the higher ABS temperature. After you have cleaned your nozzle, my suggestion would be to stick to one type of material.

- Innofil ABS prints allot better than UM ABS. To me it seems as if Innofil ABS filament is softer and the feeder wheel has a much better grip on it. My simple conclusion is that the type of material you use matters. My knowledge here is limited (I have so far only printed UM and Innofil), but maybe someone on the forum can give us additional tips on that.

- The extruder has a few design flaws making it susceptible even to tiny variations, it is not very forgiving. I have switched to the glass filled insulator, but I cannot say if this is an improvement. So far I hadn't any problems with it.

- In my opinion a closed chamber is a must for high quality prints.

 

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If I switch back and forth between PLA and ABS the nozzle will clog at some point

 

Yes. I have heard this many times. Especially from ABS to PLA. I use "cold pull" at 130C when I finish with ABS and haven't had any trouble but I have only printed maybe 5 parts with ABS. I mostly print PLA. So I'm not an expert.

 

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I wanted to come by and make a quick update.

The cold end and white spacer have been replaced with the newer models and the nozzle was replaced with a fresh one.

I've been printing frequently for two weeks with only one annoyance (which I'll get to) and I've been able to switch back and forth between PLA and ABS with no issues. So, finally, this printer is living up to its promise.

The annoyance is pretty minor and that is that switching from ABS black to PLA doesn't seem to flush out of the nozzle easily. An hour into a three hour print, about 20 minutes of printing was mixed orange PLA with black ABS. I'm not sure how the black is getting trapped in the system for that long. That' said it's a minor annoyance that's probably solved by using a cold pull before printing.

 

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