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UM2 hot-end not getting hot enough...

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I've been trying to solve this problem for a month now.

When I first got the UM2 I was so happy, everything worked fine.

After a couple of prints with different filaments I had major underextrusion, took apart the nozzle, cleaned, 20 times if not more. Support did send a new glass inforced teflon insulator.

That didn't solve it, then I got a complete new hot-end. After this I was able to print but with way higher temperatures and slower speed than before. What used to work fine with 210 degrees, 50/mms, needs to be adjusted now to 220/228 degrees with 80-90% of 50/mms. Also I need to increase the feeder pressure a notch.

The ultimate test came with colorfabb xt, which used to work perfect on 250 degrees and 50/mms but is unable to print nice and shiny threads with 260 degree and 85% of 50mm/s

The question is what is wrong? The temperature is not getting high enough, is this a hardware/software/firmware problem, and how do I fix it?

Thanks in advance, it's opening a whole new area in my brain committed to frustration and despair...


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Your diagnosis of improper temperature sounds possible.

1) When you got the new hot end did you also get a new temperature probe?

2) Consider doing one more test to prove temperature error - set temp to 110C - let it sit at 110C for a full minute and then put a drop of water on the nozzle tip. Does it boil? A drop of water from my finger will boil away in about 4 seconds. You can see it bubbling. If I squirt water onto the block through the crack in the fan shroud it boils quite noisily and the temperature quickly drops to 99C but never lower than 99C.

3) Also if the printer has been off for an hour do the bed and nozzle report the same temperature? About 20C?


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I think the temp sensor is *way* off. Does it register 20C at room temp? Or 50C?

It should be at about 108 ohms at room temp.

Here is the table of resistance versus temp:


142 ohms is 110C 152 ohms is 140C. Maybe there is a 10 ohm extra resistance somewhere in the wiring. That would mean it should show about 47C when it is actually at 20C (room temperature).

I would test it at room temperature and if it's reading 30C or so too high, then power it off and turn UM2 on it's side and remove larger cover and locate temp probe and disconnect from board and measure resistance there. It should be around 108 ohms at room temp (not 118).



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I've seen a few printers that are roughly correct at room temperature, but off by about 10% at normal printing temps. This can make the difference between completing the extrusion test happily at 10mm³/s, and failing at 7 or 8mm³/s.

I'm not sure however if this is something that degrades over time.


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the temperature of the nozzle and heater bed are the same, about 20 degrees.


Too bad. That would have been an easy fix. I still think your nozzle is cooler than it thinks it is at 110C (and 220C). I think you should try to get another one from UM.


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Ah yes, so I went to the Ulti-evening, couldn't be fixed. Brought it to the UM office. The feeder was replaced, the hot end replaced (number 3) and it prints at normal temperatures now, so happy!

Wonder how long it will last.

thanks for all the help... :)


I have the same problems so I would like to go to this UM Office also to have it fixed. Is it in Holland and can you just go there ?


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I am having a similar issue. I hope it makes sense to tag on the end of this thread rather than starting a new one. I wonder if anyone has insight while I wait for a response from UM support?

Maybe the new pt100 needs calibration (see below)

Maybe the connector is bad (I did multiple plug/unplug operations to see if maybe the contact would improve but this didn't help.

I have received an olsson block and I have ordered a new heater and probe from 3DSolex which I really hope will be arriving today. Maybe all my problems will go away, when I upgrade the full hot end but I am really worried from what I have seen so far that the new probe won't help and maybe it's the Arduino A/D circuit or something??

Here is the message I sent UM Support:


My Hot end is clearly too cold, I am under-extruding even though the readout says 210 / even when I set to 230 it's still not hot enough

I ordered a new sensor here in the UK but they are on back order, and ordering direct is too slow for me so in the meantime I purchased a sensor from RS and wired it in with new cable (soldered the connector on)

6117845 Pt100 wirewound 2.8x15mm (100ohm)class A


However I am getting exactly the same behaviour as before, Identical in fact. So I suspect that even when I get the Proper part this will not help me.

What else can I try?

I can tell it's not hot enough because I can't even wipe PLA off the surface of the nozzle, and a wet cloth barely sizzles.

There is a mention in the docs about calibration, but it is simply "TODO":



(correction, even when I set it to 240 it is not hot enough.)

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Well no responses but my UM2 is still down and Ultimaker support still haven't responded at all. What has happened to UM support? It used to be really good.

I swapped the temperature probes around and also stuck the nozzle probe to the bed then put some paper on the back as insulation and heated it up to 80 deg and let it settle to do a comparison. The temperatures were 2-3 degrees different at ambient, and similar at 80, but I didn't expect them to be exactly in sync at 80. (if you reading this beware! If you do this do NOT heat the nozzle without the probe installed, you will overheat it!)

That doesn't really tally with the fact that I am heating the nozzle to 250 now on the dial and it still seems like it is not getting quite hot enough to extrude smoothly.

I am just waiting for my heater and pt100 to arrive, but have also come to the conclusion that it could be the heater. It measures 24 Ohms but maybe under temperature and load it is breaking down and not supplying enough heat.

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After fitting my New Olsson block, the new heater and probe, I could tell the temperature issue was fixed, but I was still under extruding a little. I had replaced my Bowden tube already, but I had not yet installed the new bowden clips which I had ordered from 3DSolex. I noticed that they were moving stlightly, and after I replaced those my printer is like new again.


Now I'm off to the London 3D Printshow.

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