3D printing silicone can reduce costs and time

In its Q2 interim report, German giant, Wacker has revealed it is now able to 3D print silicone. Silicone is a useful material to be able to 3D print because injectionmoulded silicone is a favourite choice for prototyping. Seventy percent of 3D printers are used by companies, product developers and designers to manufacture prototypes. The rapid prototyping of consumer products is a USD433m market in 2015, expected to rise to USD1.8bn by 2025, according to IDTechEx Research in the report 3D Printing Materials 2015-2025: Status, Opportunities, Market Forecasts.

However, the range of materials is limited. Often a second round of prototypes are produced in silicone afterwards, because the silicone models are tougher, more durable, harder, and withstand a larger temperature range than the thermoplastics used for 3D printing prototypes. 3D printing in silicone the first time around could streamline this process, reducing design costs and time to market.

Until recently, silicone parts could only be produced by expensive injection-molding processes. Because of the costs for making the custom molds, the process is only worthwhile for large production runs or mass manufacturing. Injection moulding is likely to remain the established process for series production. Small series can be 3D printed to meet changing demands, or even each individual item can be customised.

Beyond this 3D printed silicone has potential industrial applications in automotive and medical technology, or in household appliances and optics, because it is biocompatible, heat resistant and transparent.

Silicone cannot be melted by heat in the same way as thermoplastics or metals. It cannot simply be applied layer by layer as a powder or melted by laser beam. Wacker use a system which rapidly deposits one droplet of silicone at a time on a base surface, then pauses and a UV beam scans over the tiny drops. The silicone then vulcanises in less than a second in the UV light, with the help of a platinum catalyst, crosslinking the molecules into an elastomeric material. The robot then applies the next layer of silicone droplets. This is similar to the ink-jetting of photopolymer used in Stratasys Objet printers and 3D Systems ProJet printers. It’s also similar to the technology Luxexcel use for ink-jetting then curing PMMA for optics.

However, 3D printing in silicone is not new. It is included as an emerging material in IDTechEx’s report, 3D Printing Materials 2015-2025: Status, Opportunities, Market Forecasts. Sheffield-based product design company, Fripp Design, began 3D printing silicone in January 2013. Fripp Design initially adapted a Z-Corp 510 printer to print different materials including starch-based and cross-linked polymers, and now have a fully functional silicone 3D printer. They opened a service bureau in Q1 of 2015 under the Picsima brand, to generate revenue and learn about market demands.

Before this development, it had been impossible to print elastomers. There were just no suitable processes available. Now there are some elastomeric thermoplastic filaments such as NinjaFlex by Fenner Drives and FilaFlex by Recreus for use in thermoplastic extrusion printers. The total market for thermoplastic filament in 2015 is $250m, according to IDTechEx Research, but 70 percent of that is either PLA or ABS, so currently flexible filament represents a small market with a large potential.

Fenner Drives made their first thermoplastic polyurethane (TPU) 3D printing filament in autumn 2013. And now sell via well-known 3D printer manufacturers including Printrbot, Leapfrog and Lulzbot. There is a large market in applications which require high elasticity, high impact resistance or high energy absorption.

There are some claims of being able to print flexible objects in vat photopolymerisation printers. Las Vegasbased Full Spectrum Laser were laser experts and then developed the Pegasus Touch SLA 3D printer. FSL offers its own calibrated resins including castable, flexible, and several colours. Stalactite is a start-up based in Barcelona, which offers four different materials including Elastic. IDTechEx consider that more varied materials for SLA and DLP printers will be a huge area of development in the near future, offering opportunities for highly precise objects with a wider range of mechanical properties.