It seems likely that polymers companies will be driving growth in the 3D printing industry over the next five years. Major players such as Sabic Innovative Plastics (ABS) and NatureWorks (PLA) have both announced initiatives in recent months to focus R&D on optimizing materials for additive manufacturing processes. No wonder. Materials sold into 3D printing are priced multiples higher than resins sold into industrial injection molding markets. Also 3D printing, while overhyped, still maintains sold growth rates.
Now comes word of a significant materials’ development.
The German chemicals company Wacker announced in its most recent quarterly report that it has developed a process and special material that will allow 3D printing of silicones for the first time. To date, the process has been limited to thermoplastics and metals.
Silicone is a thermoset and cannot be melted by heat in the same way as thermoplastics or metals. As a result, it cannot be deposited as a powder, and melted by laser beam to a three-dimensional shape.
In the Wacker process, a robot deposits tiny droplets from a nozzle side by side and then the silicone is vulcanized with UV light. “The homogeneous objects that are produced have virtually smooth surfaces. The material is biocompatible, heat resistant and transparent – opening up a wealth of potential industrial applications in automotive and medical technology, or in household appliances and optics,” says the Wacker report.
Wacker scientists developed the process with engineers at enders Ingenieure GmbH, a product development and prototyping company based in Ergolding, southern Germany. A custom program was required to control the robot. The developers hope the process can be optimized to print 100 grams an hour, certainly no threat to injection molding for series production, but fast enough for surgeons to wait while a custom prosthetic implant is printed.
The silicone strip is about 0.6 millimeters wide, and only half as thick. Surface finishes are described as very fine, and much better than surfaces of 3D printed thermoplastics.
Ernst Selbertinger, a research chemist, created a formulation that can be dosed as tiny liquid droplets that immediately remain stationary at the place they were deposited. “Think toothpaste – it flows under pressure as you squeeze it from the tube, but is firm when on the brush,” says the chemist. He would only disclose that the mixture contains a platinum catalyst that crosslinks the molecules under UV light.
Potential applications are custom fit eyeglass pads, respirator masks, shoe insoles and hearing aid components.
“We have a lot of ideas, and we want to provide our customers with much more than just silicone for additive manufacturing,” says Bernd Pachaly, head of silicones research at Wacker, which says it will be able to soon provide a complete system: machine, software and materials.