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New technique of 3D printing promises to bring order to the assembly

A technique that promises to revolutionize the 3D printing and, of step, you might end up with a large part of the assembly processes of components of electrical circuits or electro-mechanical components, was developed by researchers at the University of Columbia.

During the last decade, 3D printing, also called additive manufacturing, has registered a growth of 20 per cent a year, printing parts ranging from aircraft components and automotive parts to medical implants and dental metals and engineering polymers.

One of the manufacturing processes most commonly used is the selective laser sintering (SLS), which prints parts of a powder material at micron-scale using a laser. In this process, the laser heats the particles up to the point where they fuse together to form a solid mass.

The problem is that the technologies SLS have been limited to printing with a single material at the same time: all the component must be made of the same dust.

“How many products are made of a single material? The limitations of the printing in a single material have been tormenting the industry and blocking your expansion, preventing it to reach its potential,” says Hod Lipson, of the Faculty of Engineering Mechanics of the University of Columbia.

The team, led by Lipson used his experience in robotics to develop a new approach that allows to overcome these limitations. To reverse the laser so that it points upward, developed a mechanism that allows the SLS to use multiple materials.

The functional prototype, along with a printed sample that contained two different materials, was recently published by Additive Manufacturing as part of its edition of December 2020.

“Our initial results are exciting, because they hint at a future in which any part can be manufactured with a press of a button, where you can find objects ranging from simple tools to more complex systems such as robots, with no need to assemble,” the researcher said John Whitehead, who also participated in the development.

The technology has the potential to print circuits, electro-mechanical components, parts of robots, among others, ahead of the researchers.

Difficulties

The selective laser sintering has traditionally involved the fusion of particles of material using a laser that points down in a bed of printing heated. It builds a solid object from the bottom up, with the printer by placing a uniform layer of powder, and using the laser to fuse selectively some of the material in the layer. Then, the printer deposits a second layer of powder on the first layer, the laser merges new material with the material of the previous layer and the process is repeated again and again until complete the piece.

This process works well if you only used one material in the printing process. But to use multiple materials in a single print has been very challenging, because once that layer of dust is deposited in the bed, does not remove or replace by a dust different.

The technique

The researchers decided to find a way to completely remove the need of a bed of powder. Installed multiple plates of clear glass, each coated with a thin layer of a powdered plastic different.

Fell a printing platform on the top surface of one of the powders, and directed a laser beam from below the plate and through the bottom of the plate. This process sinters selectively a little dust on the printing platform in a pattern preset in accordance with a plan virtual. The platform rises with the molten material and moves on to another plate, which is coated with a powder different, where the process is repeated. This allows multiple materials to be incorporated in a single layer or stacked. Meanwhile, the plate old and used is replenished.

In the document, the team demonstrated their prototype is functional to generate a sample of 50 layers thick, 2,18 mm of powder of thermoplastic polyurethane (TPU) with a layer height average 43.6 μm and a printing of nylon and TPU multi-material with a layer height average of 71 microns.

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