Bambu Lab A1 NTC thermistor fire and meltdown hazard
The Bambu Lab A1 NTC thermistor fire and meltdown hazard is an ongoing product-safety defect in which the negative-temperature-coefficient thermistor on the AC distribution board of older Bambu Lab A1 3D printers overheats to approximately 140 C according to independent measurements[1] and Bambu Lab has acknowledged that a damaged NTC can reach 160 C and soften or melt nearby plastic.[2] Bambu Lab acknowledged the defect in January 2026 but attributed it to external power-grid surges, claimed the confirmed incidence rate was "well below 0.1%," and stated there had been "no reported cases of fire."[2] In February 2026, a consumer reported that a stock A1 Mini caught fire mid-print.[3] The company removed the NTC thermistor from newly manufactured boards in the third quarter of 2025.[2]
Background
[edit | edit source]The Bambu Lab A1 is a consumer 3D printer. In June 2024, Bambu Lab recalled roughly 12,800 A1 units under CPSC Recall 24-264 after 19 reports of a defective heatbed cable that could spark or cause electric shock.[4] That recall covered the heatbed cable, a separate component.
The current defect involves the AC power-distribution board inside the A1's base. The board uses an NTC thermistor to restrict inrush current to the heated bed; when the printer powers on, the NTC suppresses the surge and generates heat.[1]
AC board failures and melting incidents
[edit | edit source]Consumers reported in late 2025 and early 2026 that the NTC thermistor on their A1 printers was overheating and melting the plastic chassis.[1][5] A user who purchased an A1 Combo in April 2025 reported that after about ten minutes of operation the printer emitted a burning-plastic smell and began melting.[5] Grant Posner of the independent repair channel 3D Musketeers measured the NTC at 140 C with a thermal imager; Posner told Tom's Hardware the measurement was unacceptable for an electronic component.[1] Grant Posner, who runs the channel and a Tampa, Florida prototyping company, told Tom's Hardware:
It is clear there are some issues with part quality, consistency, or local power that are causing machines to catastrophically fail.
Tom's Hardware published a report on January 2, 2026 on the resurfacing hazard, noting consumer photographs of "a small bulge on the printer's bottom near the NTC thermistor" and a melted spot atop the housing.[1]
A user on the Bambu Lab community forum quoted an official company statement dated January 5, 2026, in which Bambu Lab attributed the failures to "abnormal surges or overvoltage events (such as lightning)," confirmed that a damaged NTC can reach 160 C and soften or melt nearby plastic, but asserted that "it does not lead to ignition or sustained combustion."[2] The same statement also claimed a confirmed incidence rate "well below 0.1%" and stated that "there have been no reported cases of fire."[2]
In February 2026, a consumer reported that a stock A1 Mini caught fire mid-print, producing real and sustained flames that had to be manually extinguished.[3] The official BambuLab Reddit account responded that the fire was an "accidental component failure on the toolhead board" and offered replacement parts.[3]
In April 2026, a user reported that the replacement printer Bambu Lab had sent subsequently melted in March 2026 from the same AC-board defect.[6] The user stated that customer support delayed the refund for over a month and initially offered a store gift card instead of a cash refund.[6]
Bambu Lab's response
[edit | edit source]Bambu Lab's public response has centered on three positions, all stated in the January 5, 2026 company statement that circulated on the community forum: the failures are caused by external power surges, the risk of fire is minimal, and the issue has already been fixed for new production.[2]
Bambu Lab stated:
After reviewing field data, we determined the benefits of NTC-based inrush protection were outweighed by potential downsides under rare surge conditions. As a result, we implemented a design change in Q3 2025 to remove the NTC from the circuit.
The company disclosed the Q3 2025 redesign to the press by January 2, 2026, and an official statement circulated on the community forum on January 5, 2026.[1][2]
Consumers reported in early 2026 that replacement printers subsequently failed with the same AC-board defect.[6] At least one consumer reported that Bambu Lab support denied a preventative replacement request, telling the user the original board was "designed to handle such things."[7]
Consumer and independent response
[edit | edit source]An engineering analysis posted on the Bambu Lab community forum noted that "The temp rise on the component is probably the most concerning part of this whole wall of text."[8]
See also
[edit | edit source]References
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- ↑ Denise Bertacchi (January 2, 2026). "Reports of the Bambu Lab 3D printer being a fire hazard resurface, but for a new power board component issue". Tom's Hardware. Retrieved May 19, 2026.
- ↑ "A1 Fire risk due to thermistor overheating". Bambu Lab Community Forum. January 5, 2026. Retrieved May 19, 2026.
- ↑ "Bambu Lab Recalls A1 3D Printers Due to Electric Shock and Fire Hazards". U.S. Consumer Product Safety Commission. June 13, 2024. Archived from the original on May 19, 2026. Retrieved May 19, 2026.
- ↑ "My A1 Melted - fortunately i was home. (Potential fire hazard issue)". Reddit. December 18, 2025. Retrieved May 19, 2026.
- ↑ "A1 Mini Fire Incident – Be Careful Running Unattended". Reddit. February 26, 2026. Retrieved May 19, 2026.
- ↑ "My A1 board melted, the replacement printer bambu sent then melted a few months later. Now I've been waiting over a month for a refund". Reddit. April 19, 2026. Retrieved May 19, 2026.
- ↑ "BambuLab says A1's are safe". Reddit. January 8, 2026. Retrieved May 19, 2026.
- ↑ "A1 Fire risk due to thermistor overheating". Bambu Lab Community Forum. January 5, 2026. Retrieved May 19, 2026.