Columbia Engineering has developed a new laser inversion technique for 3D printing objects with multiple materials at the same time.
According to the scientists, this could potentially change the way we build circuit boards, electromechanical components, and perhaps even robots.
Selective Laser Sintering (SLS) is one of the most widely used 3D printing processes in the industry today.
It prints parts out of micron-scale material powders using a laser: the laser heats the particles to the point where they fuse together to form a solid mass.
The catch with this technology is that it is limited to printing with a single material at a time: the entire part has to be made of just that one powder.
Columbia Engineering professor Hod Lipson and his PhD student John Whitehead have now used their expertise in robotics to develop a new approach that helps overcome these limitations.
They have managed to invert the laser so that it points upwards, enabling SLS to use – at the same time – multiple materials.
According to Whitehead, this is really exciting as any part can be easily fabricated at the press of a button:
“It could enable objects ranging from simple tools to more complex systems like robots to be removed from a printer fully formed, without the need for assembly.”
In order to make their invention a reality, the scientists had to first eliminate the need for a powder bed.
They hence set up multiple transparent glass plates, each coated with a thin layer of a different plastic powder.
A print platform was then lowered onto the upper surface of one of the powders, and a laser beam directed up from below the plate, and through the plate’s bottom.
This process selectively sinters some powder onto the print platform in a pre-programmed pattern according to a virtual blueprint.
The platform is then raised with the fused material, and moved to another plate, coated with a different powder, where the process is repeated.
This allows multiple materials to either be incorporated into a single layer, or stacked. Meanwhile, the old, used-up plate is replenished.
The working prototype has so far generated a 50 layer thick, 2.18mm sample out of thermoplastic polyurethane (TPU) powder with an average layer height of 43.6 microns and a multi-material nylon and TPU print with an average layer height of 71 microns.
These parts demonstrate both the feasibility of the process and the capability to make stronger, denser materials by pressing the plate hard against the hanging part while sintering.
The researchers are now experimenting with metallic powders and resins in order to directly generate parts with a wider range of mechanical, electrical, and chemical properties than is possible with conventional SLS systems today.
Image and content: John Whitehead/Columbia Engineering