What does a bad hotend sensor or thermal runaway look like

Is there a way to upload a screen shot here?

What is the problem?

Never seen this in my year of printing and so have no idea what i should double and tripple check here.

During the initial Hotend warmup from room temp. The hot end sensor values appeared to report no change for about 10 or 15 sec and then comes back with a jump in temperature. i would guess this is what a thermal runaway risk looks like but is this really how it manifests is self in the data? (again would love to post the screenshot)

Hello @jolly_m!

You may have a look on this:

OK that's a good start.

OK so from what I'm seeing a movement or short or dissconnect in the sensor would manifest differently then what i saw. Not to mention the 60 sec threshold isn't going to trigger anything from my 10 to 15 sec blip.

Because the Hotend heats up to 148° and then holds at that value for 15 sec then jumps to 170° and carries on like normal.

I'm begining to think the Heat graph in Octopi uses real time client side script, where if you loose wifi for 10 sec the data point values are frozen until the browser regains a connection to the live data from the octopi. (a solution that saves having to continuously refresh the page but can result in a stagnent data point stream)

I think i can test that theory by starting a print from room temp and dissabling wifi on my desktop and see if the graph values freeze but time continues to tick. And then reenable wifi and see if the real time temp values jump. Or if the page goes directly to a 404 after turning off wifi.

(would be so much easier to post a screenshot)

It's the holding for 10-15 sec which is confusing.

Maybe you should perform a PID-autotune:

That can be a reason for the "jump". If you are dependant on using WiFi, you may change the channel of the Wifi in your router.

Even easier way to test your theory is to refresh the page, which comes with all the history data in one go, if the graph now looks right (as in, a line with no jumps) then you pretty much have nothing to worry about.

Yes the data is graphed as it is received from the server, if you have intermittent issues whether this is client speed, connectivity or a ghost then it can lead to these jumps.

I recently was getting printer halted thermal runaway errors on my 3D printer that has been printing since 2017. It would get part way through prints and halt. Marlin firmware.

I spent a lot of time trying to track it down. Maybe some of my experience will help you.

First I had to figure out if it was hotend or bed and the error said E0 which was hotend.

So then it was figuring out if it was sensor or heater. I preheated the hotend and wiggled wires and watched what happened. I didn't see any sudden drops or changes in the temperature which is what I would expect for a sensor issue. So I figured it was heater related. This is where patience comes in because you have to wiggle and WAIT (not my long suit...) and see what happens. After a few wiggles I was pretty certain I had nailed it down to where the wires connect to the heater. I re-crimped those and put it back together with utmost confidence only to have my first print fail same way. At the same time I recrimped the wires I ordered 5 new heater sensor assemblies from Amazon because they are cheap and it was only a matter of time before the heater failed. New heaters arrived so I made up a fresh heater and sensor on a totally new hot end extruder and figured th was resolved... same story...
Turns out my printer had a connector near the hotend for all connections and THATS where my wires had broken due to flexing. Ran my heater sensor wires all the way back to the controller and all resolved.

Well, if you want to see how it looks like and if your printer has firmware in which this protection is enabled, simply disable the sensor-cable from the hotend to your mainbed during printing. It will show then hopefully.
That results in a real stop from printer and from Octoprint and it will tell you clearly.

The graph is getting the info about the temperatures from the printer.
Well, if the printer is somehow doing a command (like on some printer doing auto-leveling for example which can take minutes) in which it is not responding en giving a temperature back to Octoprint, you will have these sudden jumps in temperatures. You could look in de log-files or in the terminal to see what the printer tells to Octoprint.
Some commands are pretty time-consuming for a printer but the firmware on the printer is still monitoring the temperatures, just not telling Octoprint.

1 Like