Thermal model calibration | Prusa Knowledge Base

Starting from firmware 3.12.0, the Original Prusa MK3/S/+ has Thermal model protection. This results in better operation when dealing with thermal errors.

How it works

During the print, the printer is constantly comparing the temperature measured by the thermistors to a thermal model of what is expected from the printer. In case the measured temperature does not follow the model, the printer will beep and show the warning THERMAL ANOMALY, but the print will continue. If the anomaly disappears the warning goes away after 20 seconds. In case the anomaly continues, the printer will turn off the heating and activate an error. If you choose to continue the print after it stops, it is recommended to stay near the printer.

This will help in cases where the temperature issue is temporary, like when a window is opened near the printer. Also, in case the printer has a blob that wraps around the hotend, the thermal model should be able to stop the print before any damage is done to the hotend cables.

If you're interested in further details of how the thermal model works, check the Dev diary blog.

The printer knows only that something is wrong, i.e., when the system is not performing as expected. It is up to the user to inspect the printer and check for issues.

Calibration

When installing the new firmware, the printer will start the calibration. In case it does not go in the printer menu to Calibration -> Temp Model cal. It takes around 12 minutes, after which your printer profile is automatically saved.

The Thermal model also works for third-party components. Note that if you switch components in your printer often, the Thermal Anomaly error might start to appear more often. If this happens, run the calibration again.

If you are using an enclosure, the Einsy-board needs to be inside the enclosure for the Thermal model to work, or it will cause false triggers.

Troubleshooting

In case the Thermal anomaly message keeps showing, try the following steps.

A visual inspection

Ensure that the printer is completely cooled down and switched off before proceeding with any of the next steps. Heated parts can cause severe burns!

Make sure that the hotend is perfectly inserted in the extruder. Make sure the heatsink is slotted into both slots, the short side of the heaterblock is facing forward, with its wires running back alongside the left side of the heaterblock.
Inspect the hotend thermistor and hotend heater for any visible damage, especially on the part closest to the heaterblock. Make sure the hotend thermistor cables are going above the heater cables.
Inspect the nozzle position compared to the rest of the hotend. There must always be a gap (~0.5 mm) between the nozzle and the heater block. The nozzle must be tightened and secured in the heater block, and is locked against the heatbreak while heated. Among other issues, such as filament leaking, an incorrectly positioned nozzle can cause thermal anomalies. For more details on nozzle installation, please check the dedicated nozzle replacement article.
Inspect the heaterblock, especially its lower part. To raise the print head, navigate to LCD Menu -> Settings -> Move axis -> Z. Filament residue on the heaterblock is a cause for thermal anomalies. To clean it, heat the nozzle for 5 minutes, then disable heating by pressing the Reset button. Immediately after that, use a small brass brush to clear away any old plastic stuck on the nozzle and heater block. Be extra careful around the hotend heater and thermistor wires, avoid touching them with metal tools, as there is a risk of damaging them irreversibly.

PID tuning followed by another temp model calibration

Perform a PID tuning, using the temperature you use most often for printing.
In the printer menu, navigate to Calibration -> Temp Model cal., and perform the calibration again.

Measuring resistance with a multimeter

Ensure that the printer is completely cooled down, and switched off before the next step.

It is possible to test the hotend thermistor, and hotend heater resistance values using a multimeter. Please check the dedicated guide for multimeter usage.

At room temperature, the hotend thermistor should have a resistance in the range of 80 kΩ - 125 kΩ.The hotend heater has an expected resistance in the range of 12.3 Ω - 15.1Ω.

Limitations

Since the thermal model was developed on a model of a factory-assembled extruder, it may not work correctly on some modified or after-market extruders.

Starting from Firmware 3.13.0, it is possible to use a printer equipped with a Revo hotend with the thermal model enabled. This requires a dedicated Revo firmware that is located on our GitHub i3 firmware page.

If you experience issues during the calibration process, start the process described in Crash dump, and after the logging starts, reset the printer and enter the sequence:

M310 ;report current temp model settings
M155 S1 C3 ;enable advanced temp and fan logging
D70 I1 ;enable temp model debug logging
M310 A F1;run temp model calibration

In case you run into issues during the printing process, use the process described in Crash dump, and after the logging starts run the sequence:

M310 ;report current temp model settings
M155 S1 C3 ;enable advanced temp and fan logging
D70 I1 ;enable temp model debug logging

Disabling the Thermal model protection

The thermal model protection can be disabled by connecting the printer to your computer (Octoprint, PuTTY...), and sending M310 S0. An additional M500 will save the setting and the Thermal model protection will remain disabled after the next restart.

30 comments

ian dunne

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I had this problem: the machine would not do anything, as it could not even heat the nozzle to the required temperature. I checked the wire run of the heater and thermister and the resistances. The heater was right at the top end of the values, and the thermister was at 200kohms.

I ordered a new hot end assembly, and it turned up quickly. Fitted it and the machine recalibrated first go. Did a couple of test prints and a 36 hour print. I have noticed that the back part of the extruder surround has melted slightly, so the pid sensor is not sitting parallel to the print plate. Also the hot end when printing does not hold a steady temp as well as it did, occasionally going 15C out of range. The print still looks good.

Ludo B

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Ik denk dat Prusa er expres een bug heeft ingestoken zo dat je niet verder kan en een nieuwe moet kopen????? Ik heb alles vernieuwd en nog steeds een THERMAL ANOMALY.
Ik heb de PID op verschillende temperaturen gezet maat ook dat help niet. Ik kan niet meer verder. Ja zolang ik niet boven de 220 graden ga kan ik nog printen.

I think Prusa deliberately put a bug in it so that you can't go any further and have to buy a new one????? I have renewed everything and still a THERMAL ANOMALY.
I have set the PID to different temperatures but that doesn't help either. I can't go any further. Yes, as long as I don't go above 220 degrees I can still print.

Jan Kratochvíl

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Hello. Please contact our support team for help.

Yaroslav

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I am using Prusa MK3S+ with all original parts and I faced the same issue, during 3 hour print I recieved THERMAL ANOMALY error around 50 times. I checked wiring as was proposed, but then found that turning off fan reducing number of errors(it is not helping, but number of errors really decreasing). I faced error at 270C for nozzle and 100C for table. Problem starts once I tried to use Specrtum PET-G HT100, that requier 250-280 temperature of hotend and 100-110 temperature of the table. Before I was working with lower temperature fillaments (nozzle up to 240 and table up to 80) and never faced that issue. My bottom part of hotend and plastic around had white frost-like sediment, I removed it, but it didn`t help. Then I start First layer calibration and it was absolutley the same as I saw in official Guide. As for me - it happened cause of temperature sensor and sofware (I updated 3.13.1-6876 after a week it was released), it is lagging at high temperatures. Theory: when fan blows on sensor with cold air from the room - temperature decrease extreamly and your soft think something happened. But in next 20 sec nozzle trying to reach set temperature and jump +- 7C around set temperature, but still continue the process and it happens cause of huge difference between temperature in the room and temperature of the nozzle, looks like 265C is very close to the critical temperature and senors value becomes less accurate. So what I did: -I set temperature to 255 for first layer and 260 for other instead of 270 for all -I decided to set automatic fan mode (30-70%) After that I didn`t heard beeping. Additionally after sucsess I did full service as lubricating, cleaning, checking wires, etc...
I am going to make more test with different high temperature fillaments and will get back to you with new results

Alessandro Pantaleo

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Hello, thank you for your comment and for the detailed feedback. With this aspect of print fan speed, it's also possible that there might be a very slight issue with the positioning of hotend components, or it's possible that the fan shroud might be pointing too much toward the heater block (the cool air should point towards the print, not the block), which could be also due to a misshape on the fan shroud.

This doesn't fully exclude some other possible hardware causes or at least contributors, for example on hotend thermistor, hotend heater, or the combination of the two, or possible residue on heater block.

I'd recommend checking these aspects in more detail with our Technical Support, that way we can better evaluate it on your specific printer with pictures and videos and tackle the specific cause.

Yaroslav

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I made few more test. May be it is not connected, but my models unstuck from the bed (with and without special 3D print glue). I am trying to prevent it (change z axis position and increasing temperature).
I think you are right, cause I faced error even at 260 degrees during one of the test. But it was only one error during 4 hoursIn the same time I have no any issues with low temperature PETG, its printing well without errors.
Also last time I faced error - temperature was stable, so visually it was really strange
I will contact Technical Support, thanks

Lawyer_layer

•

Lots of complaining, not so much fixing :)
Here's a list of things to check + try/consider (MK3S+):
Firmware - Check your firmware version and make sure it's the current one (https://help.prusa3d.com/downloads) --> update firmware to the latest version This seems to have helped some folk. Downgrade to a pre-13.10.X version. This seems to have helped other folk.
Wiring. Check the wiring. Turn on "Preheat" then gently move the wires in textile wrap that run from the hot end to the Einsy door. If the get an error and wild fluctuations in temp, it's probably wiring. -->
Sleeve) Open the textile sleeve and see that all wiring is intact. Try rearranging it and replacing the sleeve.
Hotend wiring) Take off the cable ties, arrange the 4 hotend wires exactly like shown in Step 14 (https://help.prusa3d.com/guide/how-to-replace-a-hotend-mk3s-mk3s_161575). Note especially i) how the wires sit in the groove of the cable holder, ii) length of wire exposed before it is wrapped in the sleeve and iii) spacing of the two red hotend wires on the side of the hotend.
Einsy box wiring) Check that the sleeve bundle is correctly installed as in Step 15 (https://help.prusa3d.com/guide/how-to-replace-a-hotend-mk3s-mk3s_161575). Or try without the holder altogether.
Hotend. Visually inspect the hotend like it matters. Check the hard-to-see spots for anything --> Clean the hot end very thoroughly. Use a microfibe cloth or toothbrush (when cold). Use cardboard or a brass brush (when hot).
Calibrations. Once done, do all the calibrations to jiggle the wires. Self test, belt test, PID calibration, thermal model calibration - do them all.

daniel3334

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I think anyone that gets this alarm should thoroughly check the heater and thermistor wiring near the hot end. I replaced my heater cart about 2 months ago. Kept getting the alarm, even after PID tuning, and running calibration again. Low and behold, I had a print get grabbed a while back and ripped from the bed. Finally found some frayed wiring. It may not be EVERYONE, but quite a few of us, probably need new heaters and just haven't known it, because the older FW didn't detect it. Don't think it's just a FW issue because it just started happening.