And yet it is possible – 3D printing from several types of light-curing resins in SLA technology

SLA – 3D printing technology from resins cured with a laser beam (or light emitted by a DLP projector or LCD screen), belongs to a small group of the most precise and accurate incremental methods. However, it has one quite significant drawback – 3D prints can only be made of one type or color of material. Meanwhile, scientists from Heriot-Watt University in Edinburgh have developed a new SLA printing technique, which, however, allows …

SLA is a form of 3D printing that works on the principle of photopolymerization of resins, where a light source (e.g. in the form of a laser beam) is selectively directed at a tank with liquid resin and hardens it layer by layer. To do this, special light-reactive thermosetting materials are used that react with specific wavelengths of light. In the SLA method, the laser continuously irradiates the resin in the X and Y directions while the build platform lifts or lowers the printed part from the tank, thus creating layers in the Z axis.

And here the problem begins… A standard photopolymer 3D printer consists of one resin tank. Resins cannot be mixed in a controlled manner, and it would be pointless to replace the resin in the container during printing – the inherent viscosity of the resin leads to potential contamination, and the design of 3D printers makes it virtually impossible to change tanks quickly and easily. Over the years, several design teams have created concepts for multi-material 3D printing from resins, but none of them have been commercialized. The latest discovery made by scientists from Heriot-Watt University has a chance to change this.

As described in an article published in the journal Applied Materials Today, the essence of the new discovery is the use of specially designed resins containing nanoparticles that support the optical conversion process. Optical conversion is a phenomenon where a material’s response to light is not linearly related to light intensity. This means that the laser light only cures the resin where the laser is focused.

By using optically convertible resin materials, the researchers were able to cure the material deeper in the resin tank than otherwise would have been possible. While traditional SLA 3D printers have a depth limit of 0.1mm, the new technique has a depth limit of more than 5.0cm.

With this better depth limit, researchers have opened the door to multi-material 3D printing by curing one material at certain depths, then adding a second material and curing it at a different depth. In this way, it is possible to print multiple materials in the same process.

A team of scientists from Heriot-Watt University believes they have finally found a solution that will enable cheap and commercially viable multi-material 3D printing. Although the results of their work look promising, time will tell if this is the solution the industry is waiting for? It will be necessary to carry out further tests and observations to determine whether the new technology will actually fulfill its promise and whether there will be an entity that decides to introduce a 3D printer of this type on the market?


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