Thermal Grease: Small Cause -> Big Effect on printing results

Since most Bambu Lab printers are the same age, I can imagine
that this problem could affect several people here in the forum.

My printer has been producing imperfect prints from time to time lately.
After 3 weeks of vacation I wanted to use it yesterday and this is what I got as a result:

So I cleaned the nozzle according to the instructions and was in good spirits when the next print looked pretty decent at first glance.
When the printer stopped extracting filament after a few cm height (unfortunately no image), I cleaned the nozzle again.

But the following result wasn’t much better.

Then I remembered that I had already seen similar prints here in the forum.
So I removed the hotend and took a closer look.

The reason for the bad prints is so simple that it made me laugh:
The THERMAL GREASE had hardened.

There is a thin layer of thermal grease between the hotend and the ceramic heater for better heat transfer.
This was dry and crumbly.
So I cleaned the hotend, ceramic heater and thermistor with a dry sponge.
This was quick and easy. You just have to make sure that there are no remaining hard paste hiding in any cracks.
Then I applied fresh thermal grease (supplied with the spare parts).
More is better. :wink:

There are corresponding videos on the Bambu Wikipedia explaining how to do this.

Afterwards I had perfect prints again.

Best regards


had the same issue and i switch to thermal grizzly Kryonaut extreme for the thermal compound, it made a marked difference. the hot end heats up quite a bit faster and temps read better. not sure it will last as long but ill post if it drys out and fucks up the hot end lol

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The boron nitride is supposed to be the best for high temperatures, I tried some arctic silver left over from my overclocking days and it went dry and powdery after a short while.
Slice engineering is about the only easy place I could find BN paste to buy.

How many hours had you run the machine when you noticed this start to happen?

I bought the X1 Combo in January 2023 and printed +/- 15 kg of filament. It started two month ago with problems from time to time. When the printer was getting warm, the prints were better.

But after a 3 weeks vacancy it was worse.

I can’t help but scratch my head when I see ASI 388 as their reference pic for the wiki page on replacing the hotend. I honestly hope that’s not what’s being used.