One of the most frustrating parts of 3D printing – other than failed prints – is print speed, or lack thereof. 3D printers are getting progressively faster, but overall, they’re still slower than most people would consider ideal, especially when it comes to large prints. I, personally, have never really paused to consider the mechanics of print speed, but researchers at MIT and Binghamton University have, and they discovered that slow print speed is an equal opportunity offender – it doesn’t discriminate between professional and desktop FDM 3D printers.
A team led by Professor John Hart of MIT’s Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity discovered that when printing at a 0.2 mm thickness, both desktop and professional FDM 3D printers tended to build at a rate of about 10 to 20 cubic centimeters per hour. One of the main reasons, they found, has to do with the feed mechanism, namely a pinch wheel that feeds the filament into the extruder. The wheel is limited in that it can only exude about 60 newtons of force and feed the material at a rate of about 9 mm per second in order to fully melt the filament.
“We found that the rate at which a polymer melts is limiting in many implementations,” said Scott Schiffres, Binghamton Associate Professor of Mechanical Engineering. “The pressure required to push the polymer through the nozzle is a sharp function of temperature. If the core is not hot enough, the printer will not be able to squeeze the polymer through the nozzle.”
Knowing that means that 3D printers could potentially be manufactured differently in order to address the issue. The central issue sounds like an easy fix – heating the polymer before it’s fed into the extruder. Of course, re-engineering 3D printers to do so isn’t so simple, but the knowledge is a start, and the MIT and Binghamton researchers hope that their work leads others to consider 3D printer design in a new way.
The research is documented in a paper entitled “Rate limits of additive manufacturing by fused filament fabrication and guidelines for high-throughput system design,” which you can access here.
“The work has implications for how to scale up additive manufacturing and the trade-off between higher-resolution printing and speed. We hope it will inspire future work to investigate pre-heating of the polymer, and printing with multiple extruders,” Schiffres continued.
“While additive manufacturing (AM) advances rapidly towards new materials and applications, it is vital to understand the performance limits of AM process technologies and to overcome these limits via improved machine design and process integration,” the researchers stated. “…[Our] approach validates the build rate performance of current FFF systems, and suggests that significant enhancements in FFF build rate with targeted quality specifications are possible via mutual improvements to the extrusion and heating mechanism along with high-speed motion systems.”
Additional authors on the paper include MIT graduate students Jamison Go and Adam Stevens. The research was supported by a grant from Lockheed Martin, as well as by the Department of Defense, the MIT International Design Center (IDC) and MIT MakerWorks. Discuss in the Print Speed forum at 3DPB.com.[Source: Binghamton University]