Overview of additive manufacturing technologies using silicone

The term "additive manufacturing" refers to the production of parts by successive layers of a material with no initial shape. This makes it possible to "print" objects in 3 dimensions, with a wide variety of shapes and fillings, and even objects that cannot be produced using subtractive processes.

Since its inception in 1985, 3-D (3D) printing has been steadily expanding, both in the professional world and among individuals, thanks to the open-source 3D printer.

Materials and printing techniques are keeping pace with this evolution, and new materials are appearing every day, as in the case of silicones.

Silicones can be processed by injection molding, compression molding, extrusion, calendering or coating. Each process uses its own catalyst or cross-linking agent. Rheology also varies according to the transformation process: HCR (high concistency rubber) solid silicones are preferred for compression molding and extrusion processes, while LSR (liquid silicone rubber) liquid silicones are preferred for injection molding.

It was in 2015 that silicone saw the light of day in the additive manufacturing industry and was officially printed. Two companies presented their technologies at the Kunstoff trade fair in Düsseldorf: the German company ACEO with a drop-on-demand deposition method, and the French company STERNE with an LSR filament deposition process that cross-links under ultraviolet (UV) radiation. Other players are following with similar technologies, but using different materials and cross-linking methods.

This article begins by providing a better understanding of the cross-linking, or change of state, of silicones intended for 3D printing. Next, the technological solutions for producing parts by additive manufacturing are described. Finally, the value chain describing the capabilities, design rules and quality of existing parts and processes is presented.

At the end of the article, readers will find a glossary and a table of acronyms.