The innovative conversion of a treadmill into a giant 3D printer with an endless print bed has captured the imagination of the maker community, pushing the boundaries of 3D printing technology. Reported on May 31, 2025, by outlets like Tom’s Hardware and TechEBlog, this project, led by makers Ivan Miranda and Jon Schone of Proper Printing, transforms a standard gym treadmill into a belt-driven 3D printer capable of producing objects of theoretically infinite length. By leveraging the treadmill’s moving belt as a continuous print bed, the creation overcomes traditional size constraints, enabling feats like printing a 2-meter-long I-beam and plans for a full-size kayak. This exploration delves into the project’s mechanics, its significance, challenges, and its place in the evolving landscape of 3D printing.
The Ingenious Concept
The treadmill-based 3D printer, dubbed a “belt printer,” was born from a collaboration between Ivan Miranda and Jon Schone, who saw potential in repurposing a gym treadmill’s continuous belt to address a persistent limitation in 3D printing: build volume. Traditional 3D printers are confined by fixed bed sizes, often requiring large objects to be printed in segments and assembled, a process prone to imperfections. As described in a May 31, 2025, Tom’s Hardware article, the duo mounted linear rails, a gantry, and a custom large-scale extruder onto a treadmill’s frame, using its belt as a moving print bed. The extruder, angled at 45 degrees and mounted on the treadmill’s handles, deposits filament onto the belt, which advances to move completed sections away, allowing continuous printing.
The printer’s operation was demonstrated in a YouTube video uploaded by Miranda, showcasing a 2-meter-long I-beam printed over 36 hours, a feat that highlights the system’s capacity for large-scale projects. The belt’s movement ensures prints detach naturally as they curl under the machine, eliminating manual removal. Plans to print a full-size kayak, as noted in a May 31, 2025, TechEBlog report, underscore the project’s ambition to tackle complex, oversized objects in a single run. The setup, controlled by a SAM E70-based Duet 3 Main Board, as mentioned in a June 1, 2025, X post by @MicrochipMakes, required custom hardware and slicing methodology developed from scratch.
Technical Innovations and Challenges
The treadmill printer’s design incorporates several unique features. The treadmill’s motor, typically used to drive the belt at running speeds, was repurposed to move the belt at a controlled pace synchronized with the extruder, ensuring precise layer deposition. Stepper motors and a control board, likely running open-source firmware like Marlin, manage the system’s operations. The belt, acting as the print bed, requires careful calibration to maintain adhesion and flatness, critical for print quality. A Reddit discussion from 2021 highlighted challenges with belt leveling, noting variances up to 10 mm, which Miranda’s team addressed by reinforcing the belt’s substrate to ensure a stable print surface.
Challenges include maintaining belt adhesion and managing the weight of large prints. A 2021 Reddit post described concerns about stepper motors struggling to pull heavy prints without skipping, suggesting pulley adjustments to balance torque and speed. The treadmill’s original motor, designed for high-speed human weight, provides more torque than needed for slow printing, allowing smaller stepper motors to suffice with proper gearing. Bed adhesion, crucial for preventing print failures, was improved using isopropyl alcohol cleaning, as advised for Creality’s CR-30 belt printer, indicating a transferable solution. The 45-degree extruder angle, a hallmark of belt printers, mitigates vertical nozzle limitations, enabling overhangs and continuous printing but complicating print geometry, as noted in a 2022 Reddit thread.
Context in 3D Printing Innovation
The treadmill printer builds on the concept of conveyor belt 3D printers, which emerged in the early 2010s but gained traction recently. Creality’s 3DPrintMill (CR-30), launched in 2020 with Naomi Wu’s involvement, was among the first consumer belt printers, offering a 200 x 170 x ∞ mm build volume using a nylon conveyor belt. Blackbelt 3D, a professional-grade belt printer since 2013, has printed objects up to 16 meters long, demonstrating the technology’s industrial potential. These systems, like Miranda’s, use a tilted bed to facilitate continuous printing, with prints detaching automatically as the belt advances, reducing labor compared to traditional print farms.
The treadmill project, however, stands out for its DIY ethos. Unlike commercial belt printers like the IdeaFormer IR3 ($579) or Blackbelt 3D (€4,748), which cater to professionals, Miranda and Schone’s creation repurposes existing equipment, making it accessible to hobbyists., A 2017 Hackaday article noted early attempts at infinite build volume printers, but the treadmill approach simplifies the concept by leveraging pre-existing hardware, avoiding the need for custom conveyor systems. The project’s success, as seen in its 2-meter girder, aligns with the growing interest in large-scale 3D printing, exemplified by Builder 3D’s Extreme 3000 PRO, which offers a 1100 x 1100 x 820 mm build volume for industrial applications.
Public Reception and Future Potential
The treadmill printer has garnered significant attention, with X posts reflecting enthusiasm. On May 31, 2025, @tomshardware highlighted its “endless print bed size,” while @DenjinK on June 1 called it “genius,” reflecting community excitement., The project’s appeal lies in its audacity and accessibility, inspiring makers to rethink 3D printing constraints. However, limitations persist. A 2022 Reddit thread questioned the viability of belt printers for hobbyists, citing high costs and print quality issues compared to traditional printers. The treadmill’s belt, while durable, may wear over time, and achieving consistent adhesion across a moving surface remains a hurdle, as noted in reviews of Creality’s CR-30.
Future plans to print a kayak suggest the team aims to push the system’s limits further. Such ambitions align with belt printers’ potential for continuous production, ideal for props, cosplay, or industrial prototyping, as noted in an Amazon listing for the CR-30. The technology could also inspire hybrid designs, like linked build plates resembling tank tracks, as suggested in a 2022 Reddit discussion, enhancing flexibility for batch printing.
A New Frontier for Makers
The treadmill-turned-3D printer represents a bold leap in overcoming traditional print size limitations, offering a glimpse into a future where massive, single-piece objects can be created without industrial-scale equipment. Its DIY approach democratizes access to infinite build volume technology, inspiring hobbyists and professionals alike. While challenges like belt adhesion and print quality persist, the project’s success in printing a 2-meter I-beam and its potential for a kayak demonstrate its transformative potential. As the maker community continues to innovate, the treadmill printer stands as a testament to creativity, redefining what’s possible in the ever-evolving world of 3D printing.
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