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.
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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