A new desktop model 3D printer can print objects as much as ten times faster than other 3D printers currently commercially available. This allows, for example, a prototype that can normally be printed in an hour to be printed in just a few minutes.
The new 3D printer was developed by researchers at the Massachusetts Institute of Technology (MIT). The printer is based on a technique called fused filament fabrication, which is another name for fused deposit modelling (FDM). This involves printing layers of molten plastic on top of each other to create an object.
Prototype printing
3D printers based on FDM have been around for some time and are popular. Among others, printers from well-known brands Unimaker and MakerBot use the technology. Such printers are used by both companies and consumers and can be used to produce prototypes of new designs, among other things. This is usually faster than having a prototype produced via a traditional manufacturing technique, allowing the prototype to be tested earlier and speeding up the development process.
Despite the speed gains such 3D printers provide over traditional manufacturing techniques, the relatively slow print speed of conventional FDM-based 3D printers remains a major limitation, according to MIT. "Every year, hundreds of thousands of desktop printers using this process (ed: fused filament fabrication) are sold worldwide," explains Anastasios John Hart, professor of mechanical engineering at MIT. "A major limitation to the feasibility of 3D printing is the speed at which you can print something." For example, Hart and his team point out that printing objects the size of a few Lego bricks quickly takes an hour. This makes printing larger prototypes in particular relatively time-consuming.
"If I can get a prototype of a part, such as a bracket or a gear, in five to 10 minutes instead of an hour, or after my lunch break instead of the next day, I can design, build and test faster," Hart said. "If I am a repairman and have a high-speed 3D printer in my vehicle, I can print a replacement part on-demand after I find out what is broken. I don't have to go to the warehouse to get it from stock." Hart therefore argues that the new 3D printer his team has developed makes 3D printing a more useful technology.
Newly designed print head
The speed gain achieved by the team at MIT is due to a newly designed print head. This features two components that increase printing speed: a new screw mechanism that pushes the polymeric material - also known as filament - through the nozzle - also known as a nozzle - at high pressure, and a laser that can heat and melt the material in a short time. This combination allows material to flow through the nozzle faster, allowing the 3D printer to print the material faster.
The new design is based on the team's previous research into the causes of the limited speed at which 3D printers can print. Three factors were found to be involved: the speed at which the printer head can move, the amount of pressure that can be applied to a material to push it through the nozzle and the speed at which the print head can transfer heat to melt and flow the material.
New screw mechanism
For example, the average 3D printer uses two small wheels in the print head between which filament is placed. These wheels rotate and push the filament through the nozzle. This method is fine for low print speeds, but causes problems at higher speeds. If the wheels turn too fast to speed up the printing process, the wheels lose grip on the material and the filament is not pushed through the nozzle properly.
The researchers have therefore replaced these wheels with a new mechanism, which consists of a screw that rotates inside the print head. This rotating screw grips the filament and pushes it through the nozzle thanks to its spinning movement. This working method allows filament to be pushed through the nozzle with more pressure and higher speed. "Thanks to this screw mechanism, we have much more contact surface with the laced texture of the filament," Hart says. "This allows us to achieve a much higher pressure. The pressure is easily ten times higher."
Heating with a laser
In addition, a conventional printer uses a so-called heater block, which is often referred to by the English term 'heater block'. This block is heated and transfers heat to the nozzle, melting the filament. This method is fine for low print speeds, but cannot heat up the material fast enough at higher print speeds.
In the new 3D printer, the team at MIT therefore uses a laser, which is placed under the new screw mechanism. This laser heats up the filament and melts the material before pushing it through the nozzle. This allows the material to melt not only faster, but also more thoroughly than a conventional heater block does. The exact temperature to which the material is heated can be regulated by quickly turning the laser on and off.
Print head moves faster
In addition to the print head, the frame and motors that move the print head have also received an upgrade. This enables the 3D printer to move the print head fast enough to keep up with the faster rate at which filament is pushed through the nozzle. "We designed the print head to have high pressure and high heating capacity, and to be moved faster through the printer than existing desktop printers can," Hart said. "These three factors enable the printer to be 10 times faster than commercial printers we have tested."
Researchers are currently optimising their design. For instance, they encounter that layers of printed material do not cool down fast enough and therefore do not harden in time. This causes deformation of layers and thus the final object. "We have found that as soon as you complete a layer and go back to start the next layer, the previous layer is still too hot. We therefore need to actively cool the part while it is being printed to maintain the shape of the part and prevent it from becoming deformed or soft," Hart said. The researchers also plan to apply their technique to larger-scale 3D printing systems.
Author: Wouter Hoeffnagel
Source: MIT
Source photo: Pixabay / lppicture
