Additive manufacturing

Additive manufacturing offers good prospects for composites industry

The market for additive manufacturing processes (AM) is developing at warp speed. From rapid prototyping through rapid tooling for the tool shop to mass production of parts (rapid manufacturing): this manufacturing method commonly known as 3D printing boasts enormous growth potential.

Global sales of AM goods have multiplied almost eight-fold between 2003 and 2014. For the coming years, further exponential growth is expected, according to a study published by VDI / VDE Innovation + Technik GmbH in 2016 and commissioned by the Federal German Ministry of Economics. The study “Additive Manufacturing Methods – Stage of Development, Market Perspectives for Industrial Use and ICT-specific Challenges for Research and Development” puts the proportion of German companies in global sales of AM goods at 15% to 20% in 2010, corresponding to approximately US$ 260 million.

Enormous growth trend for desktop 3D printers

Another clear indication of the enormous opportunities for this industry are the annual sales figures for industrial 3D printers and desktop 3D printers, which have soared since 2010. According to the study, desktop 3D printers have experienced particularly drastic sales growth since 2011. “While the number of industrial 3D printers sold between 2010 and 2014 doubled, the sales figures for desktop 3D printers have multiplied more than twenty times.” In Germany a similar trend can be observed. Here, sales of industrial-scale 3D printers have more than tripled between 2010 and 2014.

The additive manufacturing market also offers a promising outlook for the composites industry. According to the analysis, new materials and compounds will remain a key driver for making additive manufacturing a well-established process in the future. Here composites will occupy an exceptional position. This refers primarily to fibre-reinforced powder or filaments, which are only offered to the market in isolated cases and have not been developed to market readiness yet.

3D printing also possible with composites

This field is led by the Fraunhofer-Institute for Production Technology and Automation (IPA) in Stuttgart. As early as 2016 scientists succeeded in developing the “3D Fibre Printer” thereby creating the preconditions for using composites as printing materials and enabling the use of high-strength lightweight construction materials in additive manufacturing. Thanks to its novel nozzle endless fibres can be incorporated into the plastic strand while printing. This means composites can be printed for the first time.

Since endless fibres rather than fibre segments are used in the composite the component is given additional stability. Compared to the plastics used in additive manufacturing today, ten times the strength could be reached, says the Fraunhofer-Institute. Moreover, the technology significantly extends the range of materials suitable for 3D printing. All thermoplastic materials that can be molten with a nozzle are possible, the Institute says, as well as the combination of numerous fibres including glass, aramid or carbon. Even bio-based plastics and natural fibres can be processed.

New process: additive free-form casting

On top of this, the IAP researchers have developed a new process that fuses the benefits of 3D printing and injection moulding. To this end they have combined the additive process with a casting process. For this so-called “additive free-form casting” the shell of the component is first made out of the water-soluble plastic polyvinylacetate (PVA) by means of Fused Layer Modelling and subsequently filled automatically with a precisely dosed amount of two-component polyurethane or epoxy resin, which dries fast. This saves time, increases component stability and allows new materials to be printed.

After drying the component can be expanded vertically following the same principle. Once the process is completed and the component has solidified the shell is removed in a water bath. What you get is a 3D printed component with properties similar to injection moulding. The IPA researchers have incorporated a special dosing unit for 2K materials in the 3D printer to cast the filling material into the shell. This layout allows the complete process – i.e. printing the shell and filling it – to be executed “in one go”. The printing process does not have to be interrupted and can be controlled in full digitally just like conventional 3D printing.  

Benefits of this process also include the possibility of processing 2-component resins and using heat-resistant thermoset plastics as construction materials. Furthermore, the component is built a lot faster and proves substantially more stable since the material fills the shell completely without any porosities or trapped air. According to the scientists the new method is suitable for a wide variety of applications and industries including insulating components such as power outlets or foams and paddings as required for safety components.