UM3 extended - suspicious heat spikes on print core 1

[Muggebadscher 2]

Hello,

 

we are facing some problems with our UM3 by random under extrusion during printing. So far, we cleaned everything and it works now. BUT: when we looked thoroughly to the temperature graphs, we see only on print core 1 peaks up to 700°C. This mainly happens,  when the heating is reduced shortly before the second print core is about to print, but not only. We tried to use a different print core, but the same thing happened.

So my questions are:

-what is the reason for this peaks and is this an issue?

-is there an explanation for the temperature graph, e.g. the units for the heater and so on?

 

Thanks in advance.

[SandervG 1,521]

Hi @Muggebadscher, thank you for your post. If I understand it correctly, after cleaning the contacts everything works fine again? About the graph and your findings; what firmware are you on?

Perhaps you have seen it; we've released a new firmware for the Ultimaker 3 yesterday, which I would recommend you to install. A few years ago some of these spikes in graphs were more common but it was addressed in an older firmware version. So updating might help. 

 

Secondly, the spike upwards to 700ºC is not an actual representation of the temperature, it could never reach it so quickly and your print core would not survive. It is most likely due to a communication error in the API, very briefly. It looks like the heater also responds to it, you can see a very brief dip. Because you are not getting a temp error the communication error must be so brief that you probably wouldn't need to worry about it. Hope this helps!

[robinmdh 100]

like @SandervG said the 700 degC is not a real temperature.

But 2 things are happening here:

One thing is that before the printcore switch, the printcore that is about to be switched off is intentionally set to a lower temperature (note the dotted target lines changing first). The other printcore is brought up to temperature, the exact timing and temperature varies by material and flow rate. This is a feature of Cura and can probably be tweaked there.

Secondly the PID temperature controller is momentarily believing that 700degC is the current temperature and therefore it stops the heater because the set-point is lower then 700degC.
The sub cause is intermittent breaks in the connection between the printcore and the printer. this can be due to the Pogo pins (cleaning those and the pads on the back of the printcore can help) or breaks in the cable* or the connector moving during printing, contact spray might help. But in the end it will occasionally happen.

This was fixed by discarding the 700 degC in the S5 and S3 software in the 5.4.2 version, but I don't see any mention of that bug-fix in the recent UM3 release. So it might not have been included, I'll have to check with my colleagues.
*EDIT: I found out that this specific spike ignore fix was not included in this update. we'll have to discuss internally if that would warrant an update at some point down the line.

From what I see in your graphs I think this fix is not in your version (based on the downward spike in the heater output at the time of the 700 degC spike in the temperature measurement) but it is hard to tell without the ability to zoom in.

The result of one 700degC spike is a cool-down of around 5 degrees which has a very minor impact, but more sustained spikes can cause a bigger visible defect in the print.

The units for the heater in the graph are between 0 (off) and 255 (which would be heater full on).

I hope that at-least answered some questions @Muggebadscher ?
 

Edited August 6, 2021 by robinmdh
update after checking with a colleague

[Muggebadscher 2]

First of all thank you for your responses.

I haven't installed the latest firmware, but i will do so today.

The problem with the randomly underextrusion was fixed by cleaning the feeder and the bowden tube.

I cleaned the print core contacts on the core itself and on the print head. No change so far.

 

I will keep you updated if the firmware update did the job.

By the way, can you somehow export the temperature graph to excel or some other tool to have a better look at it?

 

Again, thanks so far.

[robinmdh 100]

3 hours ago, Muggebadscher said:

By the way, can you somehow export the temperature graph to excel or some other tool to have a better look at it?

yes, you can download a CSV file version of this data by pointing your browser to: http://192.168.178.42/api/v1/printer/diagnostics/temperature_flow/5000?csv=1

Where the ip address has to change to your own printers. and you can change the number 5000 to get more or less data points, but the buffer is not infinitely large.
So if you are looking at more long term trends you might have to periodically get this and splice the files together based on the timestamps/first column.

[Muggebadscher 2]

@robinmdh: thank you so much, this is what i was looking for.

[CarloK 205]

The 700C degrees spikes are often caused by a communication error to the print head.

Short error bursts have little impact, but when your printer is one of the early UM3 models, then it's good to know that Ultimaker improved the tension relief on the cable in newer models to reduce these errors. 

The replacement parts are 202053 and 202071, costing about €2,50 together.

[Muggebadscher 2]

Thanks Carlo. How can i determine, if i have an early model UM3 ext?

[xuyao 0]

Hi @Muggebadscher, thank you for posting the temperature graphs. I am curious how you get the temperture graphs? I have also been trying to get a temperature graphs of the UM3, but haven't been able to find a way. As far as I know, I can not connect the UM3 to the computer. Thanks in advance.

[CarloK 205]

@xuyao These graphs are available from the printer's webpage. From the printer's menu find it's ip-address. Then, on your computer type this address and check all available info.

[xuyao 0]

Thank you @CarloK, I will try in this way.