Ivan Miranda and Jón Schone from Proper Printing have come up with an inventive way to turn an old treadmill into a working 3D printer, tackling one of the biggest limitations in 3D printing: bed size.
Instead of relying on a static print surface, they use the treadmill’s moving belt to serve as a continuous print bed. This approach lets them build parts of virtually any length in a single run. It’s a novel example of how a fresh perspective on existing equipment can address common challenges in home-based fabrication, bypassing the need for large-scale industrial machines.
Engineering the build platform and precision controls
According to TechSpot, the project began by taking the treadmill down to its basic components, keeping only the sturdy frame and the rubber belt. Linear rails were mounted directly onto the frame to guide a custom gantry supporting the print head. That print head was also modified with a larger extruder, designed to handle the increased volume of plastic needed for extended prints.
While doing all this, maintaining precise motion control was important. As a result, stepper motors were added to coordinate the movement of both the extruder and the belt. Custom wiring and control modules connected these parts, making sure they operated smoothly as one system.
Now, fine-tuning the belt’s speed to work in step with the extrusion process was also crucial. If the belt moved too quickly, the plastic layers wouldn’t stick properly. Too slow, and prints could become distorted. Another hurdle was getting the filament to grip the moving belt during printing, yet still release cleanly when finished. Miranda and Schone worked through these issues with repeated testing and adjustments.
In a test run, they created a 2 m long I-beam over 36 hours, according to Tom’s Hardware. They plan to apply the same approach to print a kayak, to further explore the system’s practical uses. Having adapted a piece of exercise equipment into a 3D printer, Miranda and John have demonstrated a new way to create large-scale parts using accessible materials and tools.
Their setup highlights how modifying existing machinery can help meet specific production needs, offering a pathway for makers to tackle projects that would normally require industrial-grade solutions.
A DIY take on conveyor belt systems
The DIY treadmill-based system shares the moving surface principle with commercial conveyor-based printers, yet it stands apart from commercial systems designed for specialized applications.
For instance, Israeli start-up Sprybuild introduced a new Stereolithography (SLA) 3D printer that uses a patented continuous build process on a conveyor belt and a rigid optical interface.
Designed to address common obstacles in 3D printing, such as material costs, workforce gaps, and design complexities, the printer ensures a stable resin flow and high-speed printing by avoiding issues related to oxygen and light. In tests, the system 3D printed dental models at 55 mm/min and reached up to 150 mm/min, significantly outpacing typical resin printers. According to the start-up, applications span dental models, orthopedic insoles, and various production molds.
Back in 2020, German startup iFactory3D launched the iFactory One Plus, an upgraded version of its original conveyor belt 3D printer, the iFactory One, with improvements aimed at serial production. The company reworked the extruder nozzle, adopted a direct drive configuration to replace the Bowden extruder, and implemented a redesigned cooling system.
These upgrades allowed the One Plus to handle flexible filaments, operate at higher temperatures, and print up to three times faster than its predecessor without compromising quality. A revised belt tensioning system also offered users more precise adjustments, ensuring smoother operation and more reliable prints.
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Featured image shows a 3D printer made out of a treadmill. Photo via Tom’s Hardware.
