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vincentbaas

UMO+ hot end leaking above heater block

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I recently bought a new UMO+ and I am very satisfied with it so far. However, I still have a problem that prevents me from getting perfect prints. The problem: there's PLA leaking on top of the heater block (printing in Ultimaker Silver metallic at 200 C), which ultimately leaks down the block and onto my nozzle and prints. Also, I noticed that the heater block is able to rotate a bit.

I already tried the following:

 

  • Letting it be, hoping it would seal itself. Didn't help, PLA keeps leaking out.
  • Cleaning and tightening the nozzle. Again, didn't help.

 

Since the heater block can rotate, I'm afraid I messed up when assembling the hot end and didn't tighten everything enough. So any suggestions on what I might do to fix this? Or any instructions on properly disassembling and reassembling the hot end?

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It all needs to be tighten...

Note that the nozzle should not be flush against the bloc -- here is how it should look like:

pic-001.thumb.jpg.0b4f9d0bf3e4d6442d9f28bf0c2c226b.jpg

(It is an E3D nozzle, but it doesn't matter).

If your nozzle is currently mounted like this, then it is very easy: tight it and all will be fixed (I would recommend a torque of 0.5Nm).

It your nozzle is already flush against the bloc then it is a bit more complicated as you can't tight it more... In that case you will have to disassemble the bloc so you can screw the brass pipe further in the bloc, and then tight the nozzle against the brass pipe.

pic-001.thumb.jpg.0b4f9d0bf3e4d6442d9f28bf0c2c226b.jpg

Edited by Guest

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I was thinking of doing one more print before taking things apart for comparison, but after seeing smoke from burnt plastic rise from the print head I decided to skip that step ;-)

Removed the fan shroud and took some pictures of the situation:

IMG_1694.thumb.JPG.5470eddcc9da8b077b4204fc0204b3e9.JPG

IMG_1695.thumb.JPG.573f6b4c350ca725fe4302c7ab29bf3e.JPG

IMG_1698.thumb.JPG.325171ec00f21207dc8661e6dcce5490.JPG

IMG_1700.thumb.JPG.f078abc6385082abb52eb93c1f0cc9bf.JPG

So it looks like my nozzle is indeed touching the block, but that I did install the isolator tube in the correct direction. Full hot-end disassembly it is then? Any tips on how to do it, besides following the assembly manual in reverse? I guess there's solidified filament in the nozzle that will make disassembly harder?

Oh, and thanks for the gloves tip, noted ;-)

IMG_1694.thumb.JPG.5470eddcc9da8b077b4204fc0204b3e9.JPG

IMG_1695.thumb.JPG.573f6b4c350ca725fe4302c7ab29bf3e.JPG

IMG_1698.thumb.JPG.325171ec00f21207dc8661e6dcce5490.JPG

IMG_1700.thumb.JPG.f078abc6385082abb52eb93c1f0cc9bf.JPG

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Ohh in reverse!

That reminds me a bad weekend I had.. well if you are lucky the leak is only inside the aluminum block, if the leak is inside the peek, well, it will be a mess since you will need to make the cleaning with 100C-110 if is pla or 130-140 if is abs.

Men, you have a big weekend ahead.

First do atomic pulls, as many as possible to leave all out as possible before disassemble it.

Then you will need to unscrew nozzle and barrel while hot 130C or more so nothing breaks, and very fast so the goo doesn't cold before removing it. Gloves, tweezers, and be careful.

Also, you will need a hairdryer pushing hot hair on the peek to clean the inside if the leak got there.

Other path... you could just...

Only remove the nozzle, heat to 150-160, insert filament from the nozzle entrance) (but dont go much futher, and then cool to 100-110 and pull out the filament goo.

Basically you will be doing a reverse atomic pull to clean the threads of the aluminum block. This is important because the block suffers very fast if the threads get too much force.

For the blob on top do the same, heat, put filament, cool, pull. That with patience and care will leave the parts as clean as possible so you can remove all and reassemble it right later.

Don't do my mistakes like:

- Boiling peek on oil to clean it (never do that, it becomes a goo and releases toxic materials)

- Don't overdo the aluminum block, the aluminum dies fast and you could end having to buy another.

- Use sodler gloves.

And if you get tired of this... Move to a um2 hotend, is much easier to clean, maintain and the tfm coupler last 500-2000h instead of 50-200h...

Edited by Guest
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As the heater and temperature cartridges looks very clean, here is what I would do:

With everything cold:

- Remove the cartridges, so the heater bloc can now move freely.

- Hold the peek with a wrench and unscrew heater bloc.

Depending on how the plastic 'seals' everything together, you will get either the 3 parts (brass pipe, bloc, nozzle), or the brass pipe might stay in the PEEK.

If the brass pipe stays in the PEEK, you will have to remove it using pliers. Be careful it is fragile. Best is now to unscrew the metal base plate and take the PEEK out, you will be more comfortable to work on it.

Now, use @korneel's method decribed here to cleanup the nozzle, bloc and pipe. They will be like new and ready to go!

Edited by Guest

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I would really avoid that method for the aluminum block since alu melts at 660C, but brass can go up to 1000C. A lighter like that can easily get metal to 900 if not very careful. Kornells method is nice but even anders did melt /deform a brass nozzle doing that.

Edited by Guest

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IMO the umo hotend assembly explanation of the manual is just bad bad. No hotend can get perfectly assembled while cold, much less aluminum that expands much more than brass.

But I bet that due diy european regulations they can't explain that the hotend should/must be finally assembled while hot. Also, well most people don't check the goo that can happen and since the extruder is way overpowered it can actually keep printing, bad, but prints.

Maybe a pro user like @amedee could make a video of how to properly assemble one, I know I always wanted to make a video showing it, but time is a b...

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Wow, thanks for all the input! I was thinking the same for the hot end assembly, I found it a bit strange that all nozzle issue instructions suggest hot tightening while the manual tells you to do it while cold :S

As I don't have pure alcohol and a gas torch laying around, I'll give the method suggested by @neotko a try, and see how clean I can get things before unscrewing them. I'll let you know how it goes!

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Easiest is to mount and tight it cold, then when it is in place on the printer, warm up the nozzle and tight it one last time.

Re. The torch cleaning method, I fully agree with @neotko: if you burn too much it will deform, but used wisely it is still my preferred method -- but indeed not too hot, if you get it red, it is way too much ;)

(I'll put the video on the list, but right now, I am already running double shifts...)

Edited by Guest
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Ok, when the instruction says gently, it of course means gently :p When trying to unscrew the nozzle (after 3 atomics that came out clean) I applied too much force and broke off the nozzle in heater block. Shit happens I guess, and I'll take it as a learning experience ;-)

[media-thumb=32847]

I assume the next step is completely replacing the nozzle, aluminum block and barrel, while salvaging the PTFE coupler, PT100 and heater element? Any tips on safely removing the still usable parts?

And since I have to order new parts anyway, suggestions on which ones to order? I already came across suggestions on UM2 hot-ends, Olssen blocks or ED3? [/media-thumb]

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Temperature was set at 160 C when it broke off, so maybe not hot hot, but at least hot.

Managed to get everything disassembled now (screw holding the heater and sensor in place was a pain in the ass, but it worked), besides the broken nozzle from the block. I'll see if I can get my hands on the screw removal tool, but in the meantime a new block might be the best way to go then. Thanks for the support!

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I've seen many people breaking the brass pipe, but it is first time I see a broken nozzle.

I guess you tight it way too much to avoid leaks (which did not help)...

Check all your parts, if they are all good, then you just need a heater block and a nozzle. For the nozzle, I would go for an E3d or an Olsson one, they exists in different diameters and are interchangeable, while the Ultimaker one is bigger.

In case the brass pipe and/or the PEEK look damaged, then buy an "hot end pack", it will probably be cheaper and you will have some spares with the leftovers...

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Vincent, you must go to the same fitness center as Arnold Schwarzenegger...I've never seen a broken nozzle!

I just did the entire hot end replacement on my non-plus UMO. It wasn't a terrible process, just awkward. I had to cut the heater wires and trim them back some more, so the wires would fit into the crimp blocks on the main board. You'll want to remove the wooden top part to make running the wires a lot easier (I tried with it still on...not fun!)

@amedee , looking at the assembly instructions (page 45), the brass pipe shown is not threaded. Mine was and I suspect Vincent's is too. Given what we know now, what gap would you suggest between the nozzle and block? Then the brass pipe just goes in a little further. (I might make this adjustment too)

I also found getting the aluminum and wood piece to be parallel tough. Maybe this is because of years of use? Despite carefully threading in the long rods, looking at the print head from the side, the side without the nozzle goes up very, very slightly.

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@amedee , looking at the assembly instructions (page 45), the brass pipe shown is not threaded.  Mine was and I suspect Vincent's is too.

 

It is just 'rendering' in the manual, the nozzle isn't threaded either...

 

Given what we know now, what gap would you suggest between the nozzle and block? Then the brass pipe just goes in a little further. (I might make this adjustment too)

 

Not a lot, half a millimeter is probably enough...

Let me try to explain: if you follow the manual, you will get the nozzle tight against the pipe. So far so good. But after that you will need to get the brass pipe tight and this is an issue, because it is not easy to get a good grip on it, if it is not tight enough it will leak, and a bit too much torque it will break...

And even if you get it right, if you want to change the nozzle there is no way you can put it back without taking it apart as you never know if you tight against the block or the pipe.

So the idea is the following: you put the pipe and the nozzle in place with your bare hands (no tools). If the nozzle comes against the block, unscrew a bit the nozzle and screw the pipe; if the nozzle is too far do the opposite. Do small adjustments until you have 0.5 - 1mm (1/32") between the bloc and the nozzle. That way, when you tight the nozzle you can hold the block and you are sure you always tight against the pipe and it won't leak.

Now that it is place, set it tight. If you have a torque wrench 0.5 Nm is more than enough (You can also print Anders' torque key)

When the hot-end is in place, get it warm and tight it again gently.

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After I got my replacement parts today, used them to reassemble my hot end. Everything went well, no leaks so far halfway through a 1:30h print. So I guess the leak was caused by not tightening the nozzle while hot (or: following the manual too closely :p). I'll try to clean the leftover pipe someday and maybe try to find a way to salvage the block, so I can use them as spares. But for now: back to printing :p

Summary of learnings (so others don't make the same mistake :p ):

- Don't literally follow the assembly manual, especially assembling screwing in hot end parts while cold ;-)

- Don't go Schwarzenegger on your brass parts while disassembling ;-)

- Leave space (0.5-1 mm) between block and nozzle, then tighten nozzle while hot (per amadee's instruction)

Thanks for the support!

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