Some of the objects created with the printer. MIT CSAIL
When you can 3D print with more than one material at once in the same printer, it makes creating complex objects a lot easier, removing the need for assembly once the print is finished. This is called multimaterial 3D printing, and it applies not just to creating objects with more than one colour, but also to creating objects that have both plastic and metal components, for example.
Researchers at MIT’s Computer Science and Artifical Intelligence Laboratory have demonstrated that it’s possible to build a 3D printer that can print in 10 different materials at once in a single print, and they were able to do so for less than $7,000 using off-the-shelf components.
Current multimaterial 3D printers are limited to three materials at one time and start at around $150,000.
But it’s not just the printer’s multimaterial capabilities that make it interesting. The team has also built machine vision into the printer, so that it can self-calibrate, self-correct and even scan already existing objects. This last point means that objects, like circuits and sensors for example, can be embedded directly into a printed object. The printer scans the 3D geometry of an object and is able to create a build around it. Or you could place a smartphone in the printbed and have the printer build a case for it.
But the self-correcting capabilities of the machine save time, effort and wasted material. As the printer builds an object, the printer scans it in 3D, checking to make sure the object matches the 3D model used to print it. If there are errors in the build, the printer can then adjust accordingly, correcting the build before the error means the object has to be scrapped.
To create the extruders, the team adapted piezoelectric inkjet printheads. These extrude microscopic droplets of polymer, which allows an ultrafine print resolution of around 40 micrometers, less than half the width of a human hair.
The materials used by the printer for the purpose of a paper accepted at the 2015 SIGGRAPH computer graphics and interactive techniques conference were all UV-curable photopolymers, or plastics that are printed, then cured under UV light. These include a rigid material, an elastic or flexible material, high refractive materials that are used as for anti-reflective coatings and image sensors, low refractive materials that are used for optical adhesives, and a support material.
However, the team has also performed experimental testing with co-polymers, hydrogels and solvent-based materials, indicating that a wide range of materials can be integrated into the one printer.
Using the printer, the team printed a range of objects, including a smartphone case, an LED lens, flexible fabric, a small multi-coloured tire, a microlens array, and a fibre optic bundle.
“The platform opens up new possibilities for manufacturing, giving researchers and hobbyists alike the power to create objects that have previously been difficult or even impossible to print,” co-author Javier Ramos said.
The potential user base of such a printer is broad. Home users could use it to create objects. Creators could use it for rapid prototyping. It could even be installed in stores so that people could submit their 3D files for printing without having to purchase a printer.
“Picture someone who sells electric wine-openers, but doesn’t have $7,000 to buy a printer like this. In the future they could walk into a FedEx with a design and print out batches of their finished product at a reasonable price,” Ramos said. “For me, a practical use like that would be the ultimate dream.”