Printing in 3D using metals is not the same as using plastics, and things get complicated when we want to use several metals at the same time.
When it comes to metal 3D printing, selective laser sintering (SLS) is used many times, and now they have invented a variation to print individual objects from different materials.
In lifelong SLS a laser beam is illuminated on a print bed filled with metal powder. As that beam moves back and forth in a pre-programmed pattern, it melts and fuses the powder into a solid, but only in selected areas. As more dust is added, the object gradually builds up, one layer at a time.
The problem is that switching back and forth between different types of metal powder is difficult, since different metals have different melting temperatures, they do not melt at the same time, and that affects the result.
Now comes the solution from Columbia University in New York with a system that makes the laser shine from below.
Initially, a metal or polymer powder of one type is deposited in a layer, on a glass plate. A flat build platform is then lowered onto that plate, so that the powder is sandwiched between the two. The laser is then illuminated through the glass plate from below, melting and fusing some of the powder in the desired pattern.
The idea is that when the build platform is subsequently raised, the solidified layer of material will adhere to it. That platform is lowered onto another glass plate, which is covered with a layer of a different powder.
As the laser moves in the same pattern as before, a layer of that material melts and coalesces over the existing solidified material. By going back and forth in this way, a single solid object can be printed from layers of two or more substances.
By printing in this way, the resulting object is constantly lifted from the dust, and users can see the shape it is taking. In contrast, in traditional SLS, the object is hidden by the surrounding dust – users cannot see everything until the printing process is complete.
Here you have it on video:
