Reports of the previously-recalled Bambu Lab 3D printer being a fire hazard resurface, new power board component issue identified as the cause — Bambu says the A1's issue has been addressed, affected units replaced or repaired

Concerns Raised Over Bambu Lab A1 Power Board Thermal Behavior — (Image credit: Future)

Concerns are being raised within the 3D printing community regarding the Bambu Lab A1 after a recent video by YouTuber Grant Posner (3D Musketeers) revealed a possible safety issue. Posner has seen an alarming number of A1 printers with charred or melted cases, which suggests that the A1’s AC power distribution board may be operating above normal temperatures, posing a risk of fire. The AC power board uses an NTC thermistor to limit inrush current and is active only while the printer is rapidly warming up. Posner claims this thermistor is being pushed too close to its rated limits.

Posner hosts the popular Print Fix Friday series on YouTube, where he analyzes 3D printing fails and offers practical advice. He told Tom’s Hardware that he has operated his Tampa, Florida-based business for 15 years, offering 3D prototyping, scanning, manufacturing, and printer repair services.

Several subreddits are echoing Posner’s concerns. One user on r/BambuLab reported “my A1 melted” with a photo of a small bulge on the printer's bottom near the NTC thermistor, while another showed a puddle forming on the top of an A1’s case. Meanwhile, Redditors on another thread suggest that Posner simply has an ax to grind with Bambu. A quick check of the 3D Musketeers channel reveals dozens of videos critical of the company.

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During a recent 3D Musketeers livestream, Posner examined an A1 printer with a thermal camera and clocked the NTC thermistor at 140° C, which he said was unacceptable for an electronic component.

After doing further research, Posner found out that the NTC thermistor is rated for 200C. He said the real problem is whether the surrounding components and the case itself can also withstand these elevated spikes in temperature that occur while the machine is heating up.

“While the component in question is rated for the temps we have directly measured,” Posner said, “it is clear there are some issues with part quality, consistency, or local power that are causing machines to catastrophically fail.”

Bambu Lab Responds to Allegations

We reached out to Bambu Lab for a statement on the melting A1 printers. A representative was quick to acknowledge the issue, but insisted that failure rates were extremely low (around .052%), directly connected to preventable power surges, and were fixed in Q3 of 2025 when the NTC was removed and the board redesigned. All customers who reported problems with the power board were provided with repairs or replacements.

The company stressed that no fires have been reported and that all Bambu Lab printers comply with applicable safety standards and use flame-retardant materials. “While a damaged NTC may generate sufficient heat to deform or melt adjacent plastic, it does not lead to ignition or sustained combustion. As a result, the risk of fire is considered extremely low.”

Bambu Lab said safety issues are taken very seriously and that an engineering team “conducted a detailed analysis of the affected units. We observed that these cases often correlate with regions and time periods experiencing severe thunderstorms, though other sources of grid surge cannot be fully excluded.”

“After reviewing field data and considering that the inrush current of the printer is relatively modest, we determined that the benefits of the NTC-based inrush protection were limited compared to the potential downsides under rare surge conditions. As a result, we implemented a design change in Q3 2025 that removes the NTC from the circuit in newer production units.”

I opened up my original Bambu Lab A1, a machine with nearly a thousand print hours, and found no signs of damage or overheating.

The red arrow below points to the NTC on the A1’s power board if you want to inspect your own printer. The Bambu Lab Wiki includes directions for replacing the AC board, which is a user-serviceable part.

Posner said that he has been in contact with Bambu Lab, and despite his conversation with the team at Formnext, he still believes the printer is a fire hazard and should be recalled. He suggests that anyone with an A1 should place a fireproof paving stone underneath the machine.

Bambu Lab told us that all 3D printers, like any valuable household electronic device, should be used with a surge protector to prevent damage from power spikes.

This would not be the first time the A1 came under scrutiny for safety-related issues. The 3D printer was subject to an official recall we reported on in January 2024. That recall was related to a cable design that could stress and arc when the machine was tilted backward.

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Denise Bertacchi is a Contributing Writer for Tom’s Hardware US, covering 3D printing. Denise has been crafting with PCs since she discovered Print Shop had clip art on her Apple IIe. She loves reviewing 3D printers because she can mix all her passions: printing, photography, and writing.

5 Comments Comment from the forums

Konomi

I'd say the issue is probably not that big of a deal. Sure, if things are melting that shouldn't, that's a design problem but also on the other side of the coin, people need to remember these aren't toys. Naturally you should have a well-ventilated workspace, use appropriate surge protection equipment and generally use common sense around such equipment.
Reply
edzieba

Meanwhile, Redditors on another thread suggest that Posner simply has an ax to grind with Bambu. A quick check of the 3D Musketeers channel reveals dozens of videos critical of the company.
That's somewhat of an understatement.
When the X1Plus team first discovered how to root the X1C's firmware, they shared this with a bunch of youtubers before making the custom firmware publicly available.
Posnmer put out a video making several claims, such as:
- Bambu using open source software in their firmware
- The printer connecting to Bambu servers in LAN mode
- The printer sending detailed logs to Bambu in LAN mode without user action
With no actual evidence ever provided.

Bambu subsequently fixed the vulnerability the X1Plus team found, whilst also adding the ability to downgrade to the vulnerable firmware for those who want to use the X1Plus firmware. The X1Plus firmware was subsequently released to the public, anyone can install it and have root access to their printers, examine all the software installed on them, examine what is logged, what the printer is connecting to (which could also be done before that with Wireshark and similar) and it was found... none of Posner's claims were actually true. He'd just made them up.
Reply
T3Kgamer

It's like the Ender 3 all over again.
Reply
3DMusketeers

edzieba said:
That's somewhat of an understatement.
When the X1Plus team first discovered how to root the X1C's firmware, they shared this with a bunch of youtubers before making the custom firmware publicly available.
Posnmer put out a video making several claims, such as:
- Bambu using open source software in their firmware
- The printer connecting to Bambu servers in LAN mode
- The printer sending detailed logs to Bambu in LAN mode without user action
With no actual evidence ever provided.

Bambu subsequently fixed the vulnerability the X1Plus team found, whilst also adding the ability to downgrade to the vulnerable firmware for those who want to use the X1Plus firmware. The X1Plus firmware was subsequently released to the public, anyone can install it and have root access to their printers, examine all the software installed on them, examine what is logged, what the printer is connecting to (which could also be done before that with Wireshark and similar) and it was found... none of Posner's claims were actually true. He'd just made them up.
Here if the proof you absolutely missed: f-IjIs4YA-4View: https://www.youtube.com/watch?v=f-IjIs4YA-4

Nothing we said was made up, there is plenty of evidence showing all the issues we specifically mentioned. You are welcome to go through that video and see the cloud calls with an offline machine and dig through your own logs if you would like. But I am tired of being called a liar when the proof has been public for over a year. Enjoy

I did not state that they used open source in their firmware. I said IF they did, then they are violating. There are open source repositories in their firmware, however it is not for things that are reasonably relevant and after it was brought to their attention, they acknowledged it.

-Grant
Reply
edzieba

3DMusketeers said:
You are welcome to go through that video and see the cloud calls with an offline machine and dig through your own logs if you would like.
I have, there are none. It's just a .log with a memory dump. A .log file that is not uploaded from the machine in LAN mode, and must be manually copied over to another machine by the user if they wish to submit a .log file (and even non- LAN mode machines require manual intervention to upload a .log). A half-hour gish-gallop of going through the data you'd expect to find in a memory dump.

As everyone else has tested and found no external connections (other than NIST NTP for time) from LAN mode machines via network monitoring, onus is on you to provide evidence of LAN-mode machines attempting to connect to external servers (let alone sending data to them), not everyone else to 'disprove' your unsourced claims.

3DMusketeers said:
I did not state that they used open source in their firmware. I said IF they did, then they are violating.
Do I really need to point out how silly that statement is? "I did not state 3DMusketeers are manufacturing untraced firearms, but IF they were that would be illegal" is an equivalent statement.
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