Abstract
In the evolving landscape of 3D printing, the quest for a more portable, efficient, and innovative printing solution led to the creation of the Positron V3. This compact, upside-down 3D printer, designed by KRALYN, redefines portability and performance in 3D printing. Unlike traditional printers, the Positron V3 can be folded and packed into a filament box, making it an ideal companion for makers and inventors on the go. With its remarkable speed, compact design, and cutting-edge features, the Positron V3 emerges as a pioneering solution in the realm of 3D printing, catering to the needs of those requiring efficiency, portability, and high-quality printing in a compact form.
Design
The Positron V3 stands out with its unique upside-down printing design, where the extruder pushes material up onto the underside of the print bed, a departure from conventional 3D printing methods. This design choice is not merely aesthetic but functional, aimed at maximizing the printer's portability. The Z-axis rail, the only part that protrudes above the bed when zeroed, can fold down, allowing the entire printer to fit within a standard 1kg filament spool box. This innovative approach ensures that the X and Y axes remain square, eliminating the need for recalibration after transportation, thus preserving precision and ease of use. The Positron V3's design embraces unconventional materials and structures, such as synchromesh chains instead of GT2 belts and a custom transparent build plate made from borosilicate glass, to enhance its functionality and performance. It boasts a maximum print speed of 250mm/s, with a travel speed of up to 350mm/s and an acceleration of 9800mm/s^2. Despite its folding compactness, it does not compromise on build volume, offering a generous 180x185x180mm space. The printer's lightweight design, weighing between 2700 to 3100 grams, further complements its portability. Its hotend can reach temperatures up to 250°C, with the build plate capable of heating up to 90°C.
Manufacturing
I started building this printer the day after the files were released which proved to cause me some challenges. Because the design was just released people have yet to start producing some of the custom machined parts required for the printer, meaning I would have to machine these parts myself. Unfortunately I just sold my last CNC Mill meaning I would have to build another specifically for these parts. I found some Thompson linear actuators at work and had some stepper motors lying around. For control I had an extra duet 3d printer controller that could be reused for this purpose. The spindle was very experimental using a RC car motor and a block of aluminum drilled out for some bearings. This proved to be the machines weak point but I was able to get all the necessary parts machined.
The next manufacturing challenge was the hotend. Kraylin used an extremely complicated machined part which I knew would be to much of a challenge to machine on my small CNC. I decided to design my own hot end and have it 3d printed out of 303 stainless steel because it was much cheaper than aluminum ($50 vs $150). Steel doesn't conduct heat as well as aluminum but I figured It was worth a shot to save some money. One major change from Kraylin’s hotend I made was adding a rounded filament path. This ended up working very well, and I never had any problems with filament flow, temperature stability, or jamming which other positron first adopters did have Issues with.
The rest of the parts were either bought, 3D printed, or ordered from SendCutSend. Sourcing some of the specialty parts proved to be quite the challenge, especially the synchromesh belts and pulleys. I ended up designing and 3D printing pulleys for a larger belt size as it was all that was available from the manufacturer. Kraylin used a custom PCB bed heater but I decided to just use an off the shelf one from robotdigg. The downside of this was unlike Kraylin, my bed was not see through so it was harder to gauge first layer adhesion.
Conclusion
I built this printer in order to have a small and portable printer that was easy to take with to college. Although the printers overall reliability leaves something to be desire, I was largely successful in this task. And hopefully I can work to improve the reliability in the future.