QIDI

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In early 2025, a consumer reported a catastrophic house fire allegedly caused by a Qidi Tech Plus 4 3D printer. The incident gained widespread attention after the user claimed their report was censored on the company's official subreddit. The subsequent public outcry led to a community-driven technical investigation that identified potential systemic design flaws, including an under-specified Solid-State Relay (SSR) and the absence of a thermal fuse, which could lead to thermal runaway. In response, Qidi Tech initiated a program to provide replacement parts and released firmware updates, though the adequacy of these solutions was debated within the 3D printing community.

Background

Zhejiang Qidi Electronic Co., Ltd., operating as Qidi Tech, is a Chinese manufacturer of 3D printers founded in 2014. The company produces a range of Fused Deposition Modeling (FDM) and resin-based printers for hobbyists and professional users.

The product at the center of the controversy is the Qidi Tech Plus 4, a CoreXY 3D printer. A key feature of the Plus 4 is its large, fully enclosed build volume with an actively heated build chamber capable of reaching temperatures up to 65°C. This feature is critical for printing with engineering-grade materials like ABS and Nylon, which are prone to warping without a consistently hot environment. The high-power electrical system required to heat the chamber became the focal point of the subsequent safety concerns.

The incident: House fire and censorship allegations

The controversy began on March 31, 2025, when Reddit user u/ProgressLocal1511 alleged that their Qidi Tech Plus 4 printer had catastrophically failed and started a fire that resulted in the complete destruction of their home. According to the user's account, the printer was operating with PETG filament. Approximately 15 to 30 minutes after a routine check, smoke alarms were triggered. The user discovered dense smoke and flames emanating from the rear of the machine, and the fire escalated too rapidly to be controlled with a home fire extinguisher.

The incident's scope expanded significantly when the user reported that their attempts to warn other owners on the official r/QidiTech3d subreddit were censored. They claimed their posts were removed and their account was permanently banned from the forum. This action was perceived by the broader community as an attempt to suppress critical safety information, triggering the "Streisand effect," where the effort to censor the report amplified its reach across social media and 3D printing news outlets.

Community technical investigation

A collaborative, community-driven technical analysis emerged, identifying two critical design flaws in the printer's chamber heating system that presented a systemic fire risk.

Solid-state relay (SSR) failure

The primary component identified as a point of failure was the Solid-State Relay (SSR), an electronic switch that controls power to the mains-powered chamber heater. The investigation concluded that the SSR was under-specified for the electrical load, particularly in regions with a 110V power grid. The higher current draw at 110V caused the SSR to operate near its maximum rating, leading to overheating and a high likelihood of failure.

Crucially, a common failure mode for an SSR is to fail "closed," meaning it becomes permanently stuck in the "on" position. This allows unregulated power to flow to the heating element, causing a thermal runaway where the temperature rises uncontrollably until a component ignites.

Absence of a thermal fuse

Compounding the risk was the absence of a thermal fuse. A thermal fuse is a low-cost safety component that physically breaks an electrical circuit if a dangerously high temperature is reached. It acts as a hardware-level failsafe against a thermal runaway event caused by a failed SSR. The omission of this standard safety component, which is common in other consumer heating appliances, was widely condemned by the technical community as a significant design oversight.

Qidi Tech's response

Following public backlash, Qidi Tech acknowledged a problem with the "heater power boards" in printers operating in 110V regions. The company's official statement attributed the issue to "high temperatures" causing "accelerated aging of the inductor" but asserted there was "no fire risk associated with this issue".

As a remedy, Qidi Tech initiated a program to ship "optimized replacement heater power boards" to affected customers and released firmware updates with "optimized chamber heating logic." However, these solutions were criticized by many commentators as an inadequate software patch for a fundamental hardware safety flaw, arguing that no firmware could prevent a fire if the physical SSR component failed.

Consumer and media reaction

Media coverage

Leading 3D printing news publications, including Fabbaloo and All3DP, covered the story in detail, criticizing the initial censorship and calling for greater transparency. Influential YouTube channels, such as 3D Musketeers and Ricky Impey, produced in-depth videos explaining the technical issues, which were instrumental in pressuring Qidi Tech to publicly address the problem.

Community-developed solutions

In response to the perceived inadequacy of the official fix, technically skilled users designed and shared their own safety modifications. These community-driven guides detailed how to replace the under-specified stock SSR with a higher-rated component and, most importantly, how to add the missing thermal fuse to the heater circuit. This proactive response created a decentralized, open-source repair program that provided a more robust safety solution than the one offered by the manufacturer.

Current status

In the months following the incident, Qidi Tech reportedly began shipping newer batches of the Plus 4 printer with the updated heater board pre-installed. However, the community-developed SSR and thermal fuse upgrades remain a popular modification for owners seeking a higher level of hardware safety.

While the possibility of legal action was discussed among consumers, as of late 2025, no public records indicate that a lawsuit was filed in direct connection to the reported house fire. The incident highlighted the significant jurisdictional hurdles consumers face when seeking recourse against foreign-based manufacturers.