Hello!
The printer began to interpret the nozzle temperature incorrectly. As the nozzle temperature increases, the deflection also increases.
At the very beginning I thought that the problem was in the nozzle or thermistor. The printer skipped extruder steps already when filling plastic at 250 degrees. But I changed 3 nozzles, 3 thermisters and 2 heaters. I examined the extruder more than once. But the problem remained. If you unscrew the nozzle and try to push the PETG plastic with your hands, it barely passes through the nozzle, even at 270C degrees.
Today, after purchasing a multimeter with a thermometer and measuring the nozzle temperature, it became clear that the problem is with the way the printer perceives data from the thermistor.
The multimeter’s thermometer error is unlikely, since I took several measurements in different places and placed the sensor directly under the silicone thermal sock.
Has anyone encountered a similar problem? Or do you have any ideas on how to deal with this problem?
Can this be solved by replacing the print head electronics? Or could the problem be deeper, in the main control board?
I also updated the printer and did a factory reset.
Thanks for your reply! Please tell me what is the difference between the old and new revision of the hot end?
Yes, I also tried the OEM hot end, with replaceable nozzles. And at some point it seemed that everything was working, but in the end it became clogged with plastic in the thermal barrier. And so far I don’t know how to extract PETG from it.
You are getting the heater flat on the hot end and not on the top or bottom metal lips and using the thermal paste correctly right ?
If that is all good I would remove the th boards and look if any of the solder joints are bad.
It also sounds like you are only using the oem hot ends then your next step is the tool head board. I would also get the usb tool head cable when you order parts because they have had problems with the usb cable and if you need one you will have one in stock.
Also you have the V9 board. I have the V9 dual red laser th board instock brand new if you need that version just message me but most likely you have the single laser model and they are very hard to get these boards …
The heater was indeed always installed correctly, I checked during assembly. I applied thermal paste.
I tested it on two original nozzles from the kit and on CHT nozzle V2.
Now I have reassembled the hotend using the original nozzle, performed a self-test, and then performed all the calibrations again. But it did not help. Which is quite expected. The temperature difference is the same as last time.
I checked the board visually (unfortunately without a magnifying glass or microscope), and did not find any visible problems.
An electronics engineer I know also checked it, but he also did not find any problems on the way from the thermistor to the controller on the board.
I’m still waiting for a response from support. I hope they answer soon. It’s already the fifth day of waiting.
For these measurements, do you need to get to the power supply under the back cover?
Yesterday I installed a new set of boards in the print head (TH Board Set V9). Replaced both boards and cable. But the problem persisted.
After the replacement, I did a factory reset and calibration.
Today I tried to downgrade to the previous firmware, after which I again performed a factory reset and carried out all the calibrations. Before these manipulations, I completely reassembled the hotend, replacing the thermal paste everywhere with the original one supplied with the printer. Unfortunately, this also did not improve the situation.
Are you 100% sure the extruder and motor are working correctly and the extruder is moving filament ok without the nozzle installed and if you put a load on the filament input side with your hand it is not skipping too easily ?
I think the meter thermistor will show a lower temp than the internal temp zone because they have the thermistor internal on the hot end so this meter test is not giving the true internal readings only the external readings but we don’t know how much temperature offset it will have so we have to work with the internal temp sensor.
.
Power Supply:
You can start at the power supply and see what readings you get then check the voltage at the tool head heater you might see a pwm signal or they can just switch the heater on and off @ 24 volts.
Thermistor:
My new oem thermistor sensor is @ 102.6 @ 24c in the room using the 200k ohms meter setting so they are using 100k thermistors.
Thank you for your help!
I decided not to touch the power source for now. And my thermistor gives readings within the normal range. Thanks for your measurements!
Yesterday I tried to compensate for the temperature difference by increasing the nozzle temperature by 17% (this is the difference between the thermistor and multimeter temperature sensor readings).The result was 295 degrees for PETG.
At first, the printer printed normally, but there was a slight lack of extrusion. I chalked it up to the fact that I didn’t do a filament calibration after resetting and calibrating the printer. But after a couple of small successful prints, the nozzle became clogged again.
Timelapse video: https://drive.google.com/file/d/1PZhLcC9qD8pZ6WX-ZsC20p9yNlJWI5kn/view?usp=sharing
Did you replace the usb c cable from the tool headboard to the ap board ?
I think the extruder motor is cutting out at times then the filament clogs the nozzle is what I think might be going on with your printer.
If the power supply had drop heater voltage at 295c then you would have seen nozzle temp error code being it sounds like your thermistor is reading ok and in specs.
One of these might be the bad guy because you have a new tool head board already so that rules it out. I would do the parts in this order.
The op has already replaced the tool head boards and it has a new FPC cable in the kit. I think op would have used the new cable also.
The MC-AP cable can fail but I would think the ap board would have a few problems going on or error codes popping up but this printer is mystery with info.
Sadly Bambu lab has not released wire diagrams and test specs to help us out.
I’m guessing it’s unlikely there’s a cable problem. My colleague found out that in the FPC cable the connections between the boards are duplicated (two lines per connection). Most likely, the situation is the same in the Type-C cable, since there are 24 contacts. But I’ll check by replacing the cable. Thanks for your help and support!
I also just received a response from Bambu support:
Hello,
Thanks for contacting the Bambu Lab support team.
I deeply apologize for the inconvenience you experienced. Our response times have been delayed due to a temporary shortage of staff. Please be assured that we are actively working to restore our regular operations as swiftly as we can. If you require any support, please don’t hesitate to get in touch with us – we’re here to help and will do our best to assist you and provide a solution to your problem.
So far have you only tried printing PETG or does this also happen on PLA?
By the looks of your testing, I am not sure if it’s caused by the hotend. To sum up you have already replaced all parts of the hotend assembly?
Thermistor
Heater
Hotend
Additionally, you also replaced the Toolhead boards.
Could you please make a video, showing the following process:
power down the printer
remove the hot-end from the extruder but leave the cables attached
remove the PTFE from the extruder
power the printer on
heat the nozzle to 220 degrees
insert filament in the extruder
use the buttons on the printer screen or the handy app to extrude and retract filament
Should this not work:
set the nozzle temperature to 0
power down the printer when the nozzle is cooled down <80 degrees
uninstall the extruder, but leave the cables connected
heat the nozzle to 220 degrees
use the buttons on the printer screen or the handy app to extrude and retract filament
make a video showing the extruder motor gear (does it move as expected or does it skip)
Yes they can run multi wires for a backup solution or to handle the extruder amp draw but they can also shut the extruder driver chip down if one of the wires is dropping voltage or signal we just don’t know 100% of how they designed the circuit to work let hope we get more information in the future so we don’t have to use parts to eliminate these problems.
Yep they want to run an extruder test to see if it is cutting out at times and you are not using pla with petg settings or the roll of petg you are using is tagged wrong and loaded with pla filament.
I would think by now you have already tested other filaments with the same results.
Keep us updated on what you find out in the end it will help others out and I hope you are up and running soon…
