MIT engineers design super fast desktop 3D printer

The team did away with the traditional nozzle design, which uses a "pinch-wheel" mechanism to feed through the plastic, replacing it with a screw mechanism that turns within the printhead.

0 December 18, 2017
Staff

Although 3D printing can speed up production times and make it easier to create products and components from scratch, MIT engineers are taking it one step further. The team has developed a new desktop 3D printer that performs up to 10 times faster than existing commercial counterparts.

Most common desktop 3D printers are able to print a few centimetres-sized blocks in an hour. However, the new design can print similar sized objects in a matter of minutes.

3d printer mini objects fast

Collection of objects and test samples printed on the new 3-D printer, including a miniature chair, simplified model of Building 10 at MIT, eyeglasses frames, a spiral cup, and a helical bevel gear. Image courtesy of Chelsea Turner.

The team incorporated two new, speed-enhancing components in the compact printhead: a screw mechanism that feeds polymer material through a nozzle at high force; and a laser, built into the printhead, that rapidly heats and melts the material, enabling it to flow faster through the nozzle.

In order to show off the machine’s capabilities, the team printed various detailed, handheld 3D objects in minutes. According to Anastasios John Hart, associate professor of mechanical engineering at MIT, the capabilities demonstrated with this new machine push the boundaries for 3D printing to become a more viable production technique.

“If I can get a prototype part, maybe a bracket or a gear, in five to 10 minutes rather than an hour, or a bigger part over my lunch break rather than the next day, I can engineer, build, and test faster,” says Hart, who is also director of MIT’s Laboratory for Manufacturing and Productivity and the Mechanosynthesis Group. Hart and Jamison Go SM ’15, a former graduate researcher in Hart’s lab, have published their results in the journal Additive Manufacturing.

In a previous paper, the duo identified underlying causes limiting the speed of the most common desktop 3D printers, using “fused filament fabrication.” Commercial desktop extrusion 3D printers, on average, print at a rate of about 20 cubic centimeters, or several Lego bricks’ worth of structures, per hour, which is really slow.

The team identified three factors limiting a printer’s speed: how fast a printer can move its printhead, how much force a printhead can apply to a material to push it through the nozzle, and how quickly the printhead can transfer heat to melt a material and make it flow.

“Then, given our understanding of what limits those three variables, we asked how do we design a new printer ourselves that can improve all three in one system,” Hart says. “And now we’ve built it, and it works quite well.”

replacing it with a screw mechanism that turns within the printhead. The team fed a textured plastic filament onto the screw, and as the screw turned, it gripped onto the filament’s textured surface and was able to feed the filament through the nozzle at higher forces and speeds.

The texture on the filament provides greater contact areas, which allows for a higher driving force — easily 10 times greater according to Hart.

The team added a laser downstream of the screw mechanism, which heats and melts the filament before it passes through the nozzle, melting more quickly and evenly.

Hart and Go found that, by adjusting the laser’s power and turning it quickly on and off, they could control the amount of heat delivered to the plastic. They integrated both the laser and the screw mechanism into a compact, custom-built printhead about the size of a computer mouse.

Finally, they devised a high-speed gantry mechanism — an H-shaped frame powered by two motors, connected to a motion stage that holds the printhead. The gantry was designed and programmed to move nimbly between multiple positions and planes.

The researchers did come across some challenges when speeding up the process, specifically with the temperature of the layers in the object. The extruded plastic is fed through the nozzle at such high forces and temperatures that a printed layer can still be slightly molten by the time the printer is extruding a second layer.

“So we have to cool the part actively as it prints, to retain the shape of the part so it doesn’t get distorted or soften,” Hart says.

The team is tackling this challenge and exploring ways to optimize the printhead.

“We’re interested in applying this technique to more advanced materials, like high strength polymers, composite materials. We are also working on larger-scale 3-D printing, not just printing desktop-scale objects but bigger structures for tooling, or even furniture,” Hart says. “The capability to print fast opens the door to many exciting opportunities.”

This research was supported by Lockheed Martin Corporation.

meche.mit.edu


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