Heavily used machine, extrusion problems

[PyramidHead76 0]

Hi all,

 

I have an UM2+ (upgraded from UM2 by previous owner) in addition to 4 other 3D printers, and the Ultimaker is easily the machine that I've used the most. As per the machine stats, 3KM of filament has passed through it.

 

But, I've started having extrusion problems in the last month on files which worked before. The machine just stops extruding, except at very slow print rates. As you can see, the machine hasn't had an easy life and it's probably time to replace some components. That's fine. I've worked through https://ultimaker.com/en/resources/11704-extrusion-problems many times in the printer's life, but it doesn't help this time.

 

So, I've replaced or cleaned quite a lot already, it's still not working properly and I'm not sure what to replace next.

What I've already done:

 

* Atomic clean

* New PTFE coupler

* New PTFE bowden tube

* Disassembled, cleaned, reassembled the extruder on the back of the machine, making sure the cogs are all seated correctly. There's little visible wear here, but it's a UM2+ addon, so has only been fitted for a smaller % of the machine's lifetime.

 

Possible next items:

 

1. New nozzle (I can manually push material through so I don't think it's this)

2. New thermistor

3. New hot-end entirely

4. ???

 

So, for other long-term UM2+ owners in particular: What would you suggest as the most likely problem?

 

Thanks!

Neil

 

 

[geert_2 557]

Have you checked these?

 

- Check if the little nozzle-cooling fan at the back of the head still works? If not, or if too slow, this would cause the heat to travel up into the filament, soften it, and make it hard to get through the teflon coupler. Sometimes filament strings and hairs get sucked into it, slowing it down.

 

- Does the feeder wheel not slip on the drive axis? Write a colored mark on both, and see if they stay aligned? I have read that this occasionally happens.

 

- With a fine needle (with rounded edges so you don't damage the nozzle) gently and carefully poke through the nozzle?

 

- Bad filament that is too hard to unroll near the end of the spool? This could act as a very strong spring, trying to pull the rolled-off filament back onto the spool. Also, filament with a too tight bending radius causes very high friction in the bowden tube and in the nozzle. This is why near the end of a PLA spool, I manually unroll a few meters of filament, straighten it, and roll it back onto the spool very loosely.

 

- Bad filament with incorrect (too thick) diameter?

 

- When manually heating the nozzle, I guess the temperature readings are okay and stable? But if you can easily push filemant through manually, it should be okay.

 

PS: if you would like a more gently method of atomic pulls, without brutal pulling and risk of displacing nozzle-components or bending rods, you might try my method: disconnect bowden tube at front, manually heat the nozzle, manually insert and extrude some material (preferably PLA), let cool down very well until at room temp (blow compressed air to speed this up, if available), then gently wiggle and rotate the filament to dislodge dirt, heat up again to 70°C, and gently rotate while gently pulling the filament out. No brute force. For me this works equally well as the traditional atomic pulls, but it is easier on the machine.

 

For the full manual and photos, see (and then scroll down a bit):

https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

 

[PyramidHead76 0]

2 hours ago, geert_2 said:

 

- Check if the little nozzle-cooling fan at the back of the head still works? If not, or if too slow, this would cause the heat to travel up into the filament, soften it, and make it hard to get through the teflon coupler. Sometimes filament strings and hairs get sucked into it, slowing it down.

 

 

Thanks for your detailed suggestions. I think this was the key one, or at least started me on a chain of cooling-related things & it seems to be working again now.

 

Although the fan *was* working, both it and the heatsink were pretty dirty. I took it all apart, cleaned it up with IPA (when cold, obviously), and while I was at it, added some fresh thermal paste around the isolator, and the equivalent aluminium piece connected to the top of the PTFE piece on a 2+.

 

Before doing that, I noticed that your slow pull technique, and an earlier 'atomic' pull resulted in a almost-break high up the filament where I wouldn't expect one to be (see pic) - I guess what I was seeing here was that there was too much heat up above the PFTE break, and that was probably causing everything to go wrong at the first retract?

 

Anyway, I'll see how it goes...

 

 

[silver-girl 1]

Hi, wondering if this fixed it for you? I'm having a similar problem:

 

I'm printing 25 or so of the same 19hr file, PLA on a 0.6mm nozzle. While I was still prototyping, I had a nasty leakage which I cleaned up, but the extrusion has never been as good. On Thursday I finished a print and went to change the filament, and the extrusion, after initially coming out fine, went down to almost zero.

 

At first the filament extrudes fine, then after after 30secs it becomes very very slow. The feeder starts clicking and grinding as there's nowhere for the filament to go. (See pic)

 

- worked through the extrusion problems list

- tried various filaments including ones I've used before, new and old

- atomic clean several times

- dismantled and cleaned Bondtech feeder

- cleaned and inspected Bowden tube

- I changed the PTFE coupler a few weeks ago, but am getting a new TFM tomorrow just in case

- cleaned the fan and heatsink

 

Any other suggestions? I'm getting pretty desperate - need to have these done by next week!

 

P.s. I've always had atomic cleans that look like this - is this normal? I've never seen anyone else's looking like this.

Edited October 6, 2019 by silver-girl
correction

[PyramidHead76 0]

Hi. Well, what I thought had fixed it hadn't, it failed again 75% through the next print.

 

Then I switched to a brand new roll of filament and that worked 100% fine. I unrolled the problematic filament, wrapped it losely around a chair to try to reduce tension in it - And over the next 24h literally every winding just snapped under its own tension. I guess as geert_2 said, when that tension is all in the bowden tube & extruder it's just too much for the printer.

 

Really all of these things we've changed are interdependent and help a little bit, but there are many combinations of things that might not quite add up to a successful print.

 

But back to your specific problems: Your atomic pull results definitely look "interesting", with the twin tails at the end. It seems like maybe the filament is just about squeezing around a blockage maybe?

 

If you don't have another nozzle to try, one other thing I've done before with a different printer, was to remove the nozzle, hold it over a gas stove (with long, insulated pliers) and physically poke the contents out with a metal rod. It's a shame there's no magic chemical that dissolves PLA in the way that Acetone can be used for ABS.

[geert_2 557]

@silver-girl: are you sure you have a standard nozzle? I think there are a few printers with split internal channels in the nozzle, like a snake-tongue. Maybe you have such a one?

 

Standard atomic pulls should look somewhat like these below.

 

Here the big blob in the white indicates that the teflon coupler (UM2-printer) is worn out (=internally deformed) and needs replacement.

 

The orange at the bottom is what an optimal result should look like. Orange/white colors shades are due to doing the atomic pulls as part of a filament color change.

 

 

@PyramidHead76: yes, underextrusion can be the result of the sum of lots of little things. Added up resistance in the unwinding of the spool, spool friction, bowden-tube friction, nozzle friction,... What I usually do is unwind a bit, straighten it by rolling it up in inverse direction on a skater wheel (7cm diameter), immediately release again, and wind it loosely up again on the original spool. So the tension is off. Indeed, often I see small cracks due to the straigthening. But I do *not* let it sit under straightening stress for longer periods of time, because that causes these cracks to grow and break the filament. So after straightening, you should immediately release the stress. Especially for hard and brittle PLA filaments.

 

Microcracks in straightened colorFabb PLA/PHA (color: natural) filament:

 

Straightening filament with a skater wheel, then releasing it. So it sits very loose around the spool, and is prevented from falling off by the yellow slider on the edge of the spool. The bending radius is now almost identical to that of the bowden tube, causing very little friction in the tube and nozzle. This especially helps for the old UM2 (non-plus). My prints normally take 2...3 hours, and consume 2...3 meters, so I can easily do this (might be inconvenient for day-long prints). Try manually moving both unstraightened and straightened filament through bowden tube and nozzle to feel the difference in resistance.

 

[silver-girl 1]

Thanks for the tips - it was the PTFE coupler, in the end, which I replaced with a TFM one. This is odd as I only replaced it a few weeks ago and can't have done more than 200 hours printing on it. It didn't look burnt at all (like the pic in the online guide), maybe a tiny bit deformed. I think it could be a combination of printing many long prints at a high temperature plus being a bit too fierce on my pull technique.

 

The tips about the atomic pulls are really helpful thanks. Yes, I have a Matchless nozzle which has twin channels. I found that @geert_2 slow wiggle technique didn't work for this type of nozzle as the channels just break off and get stuck in the nozzle. But it's definitely a good idea to be a little more gentle both on insertion and on pull.

 

Thanks also @geert_2 for the photos what a deformed PTFE coupler will look like on a pull. I've attached my before and after (coupler change) pulls for comparison.

 

A new Bowden tube and nozzle arrived in the post today. Annoyingly the nozzle has a different socket size to the others so I can't try it out yet!

 

A few more questions:

Temperature: The default setting (not sure whether Cura or UM) for 0.6mm nozzle is 230ºC - do you think this is too high? I've dialled it down to 220º and it seems to come out fine.

 

@PyramidHead76 What is thermal paste, is there a brand I should get, and where exactly does it go?

 

Fans: I printed overnight and I came in this morning to a perfect print - but the side fans were still on despite the nozzle being room temp. Never happened before. Currently printing now and I can't adjust them off 100%. Thoughts? 

[geert_2 557]

Yes, obviously an atomic pull by rotating and wiggling is not going to work on split channel nozzles.  :-)  At the time of writing that manual, I didn't even know such nozzles did exist.

 

For temperatures, I think the best is to try lowering and increasing temp in steps of 5 or 10°C on the fly, while doing a testprint. And then see when it starts to underextrude, or get too liquid. And then find something inbetween that works best for your typical models, speeds, materials, nozzle, and printer model. All these have an influence. Start from the default values for your situation.

 

Thermal paste is thermally conductive paste, to get a better thermal contact between components, to heat up or cool down things more efficiently.

 

Often people use thermally conductive but electrically insulating paste between microprocessor chips and cooling plates in computers. This is usually white or grey paste.

 

Sometimes we use paste that is both thermally and electrically conductive. This is often copper paste, which is also used to prevent bolts and nuts to get stuck and corrode. Copper paste lubricates a bit, and makes movement easier, *but it can cause short circuits!* So it depends where you want to use it. Copper paste is more often used on screws in bolting together heavy equipment, like gear boxes, engines, pumps, piping in chemical plants, etc...

 

I have copper paste between the nozzle and cooling plates on my UM2. It is the dark color shade (barely visible) at the bottom of the inox ring with round holes, just above the lowest thick aluminum plate, and just below the tiny red marker line.