While several companies have developed 3D printing materials and processes with similar properties capable of simulating silicone, so far 3D printing with actual silicone materials hasn’t been possible. However, 100 year old chemical manufacturing giant WACKER CHEMIE revealed in their recently released Q2 Report that their WACKER SILICONES division has developed new technology making it possible to use silicone 3D printing materials with additive manufacturing technology. The new technology was developed alongside German product development company Ingenieure GmbH, and will have applications in markets as diverse as the medical industry, automotive parts, contact lenses and consumer products.
The reason that 3D printing with silicone hasn’t been viable until now, has to do with the materials properties that make it such a desirable material in the first place. This is because silicone cannot simply be heated up and printed into shapes the same way that thermoplastics or metals are. Traditionally, silicone parts could only be produced using an injection-molding processes, which is quite costly unless being used to manufacture large production runs of products. But the cost of developing molds makes the process far too expensive for general prototyping, customisation and product development needs. In order to make it possible to use silicone for those purposes, WACKER researchers needed to develop a completely different process.
The process that they ended up developing is similar to traditional 3D printing, but uses a glass printing bed, a special silicone material with a high rate of viscosity and UV light. A printing head similar to an inkjet printer lays a thin player of tiny droplets of silicone side by side on a glass printing bed, then the silicone is vulcanized using the UV light. The process is repeated until the desired object is complete, each new layer simultaneously being vulcanized to the layer beneath it. The final objects have virtually smooth surfaces and just like traditionally manufactured silicone parts, are completely biocompatible, heat resistant and transparent.
“Until now, it had been impossible to print elastomers – i.e. rubbery materials. There were just no suitable processes available. Injection molding is the established process for series production, and will remain so. But people who design prototypes or only want to make a few copies of a part can now very rapidly and flexibly modify such small series to meet changing demands. That is the unique advantage of the process,” explained WACKER SILICONES head of silicones research Dr. Bernd Pachaly.
The key is printing with very small drops of silicone, fed through a small, specially designed printing nozzle. Because the drops need to be so small and precisely placed on the printing bed, standard 3D printing software wasn’t an option, so the developers needed to develop their own customized program. By the time the first layer is printed in place, the silicone drops have merged into a fine line, which the UV beam then vulcanizes in less than a second. This burst of UV light cross links the silicone molecules into a solid, but flexible, elastomeric material. While the process is still slower than WACKER feels is currently marketable, they believe that will eventually speed up the process to produce objects at a rate of 100 grams of silicone per hour.
The silicone 3D printer is capable of printing in extremely fine detail, with each strip of silicone measuring 0.6 millimeters wide, and only 0.3 millimeters thick. WACKER researchers say that the finished objects look almost identical to products that have been injection molded. In order to create that level of detail, they developed a silicone material that can be printed as a liquid, yet remain completely stationary when deposited onto the printing surface. WACKER silicone developer Dr. Ernst Selbertinger described the properties of the material they developed, explaining, “Think toothpaste – it flows under pressure as you squeeze it from the tube, but is firm when on the brush.”
In their comprehensive Q2 Report, WACKER detailed several immediate uses for their new technology, including custom printed silicone respirator masks, hearing aids and nose pads for eyeglasses. Because silicone is transparent, WACKER SILICONE is also devising other optical applications, such as contact lenses that can be 3D printed to order. They also will be able to develop a process to create silicone insoles for running shoes, customized individually for a specific users foot. Eventually they believe that there is the possibility of at home uses, such as customized silicone baking pans, and other consumer products that can be designed and printed on home 3D printers.
Currently WACKER has not provided any significant detail about the chemical make-up or mixture of their silicone product, however they did say that the material contains a platinum catalyst that encourages cross linking of the molecules when exposed to UV light. You can find out more about the process by checking out WACKER CHEMIE’s Q2 Report. Let us know what you think the possibilities of 3D printable silicone are over on our Silicone 3D Printing Technology forum at 3DPB.com.