This is a guest contribution by Vasilii Kiselev, Founder and CEO at Top3DGroup

Cincinnati Incorporated, a mechanical engineering company famous for their giant BAAM (Big Area Additive Manufacturing) 3D printers recently produced likely the largest composite 3D printed part in the world, using recycled granulated composite materials.

The part is seen in the image above. It’s a component of a formwork that was not post-processed at the time. Such formwork is used for producing concrete panels with window frames for New York apartment buildings. 3D printing of a 400-pounds (180 kilograms) part with the length over 9 feet (3 meters) took just 7 hours. This proves the efficiency of the BAAM 3D printers that were developed with the help of ORNL.

The BAAM additive systems are constantly under improvement regarding their efficiency and compatibility with different materials. Earlier versions were capable of 3D printing with granular polymers and composites using a screw extruder. Carbon-filled ABS plastic is usually chosen as a material. The most known example of using such equipment is additive manufacturing of car bodies in Local Motors automotive company.

New experiment used a new version of the BAAM 3D printers that can simultaneously print with two materials thanks to a switching mechanism. The developers highlight this, since the solution is cheaper than a full two-extruder system and makes it possible to upgrade existing systems to the new mechanism without significant reworks.

“The source of material fed into the extruder is switched on the fly at specific times during a print by sliding two material ports back and forth over the infeed to the extruder. […] The system also includes a material blender outside the frame of the machine that can blend specific amounts of different materials and fillers on the fly for specific custom material grades,” explains Alex Ristenberg, a product manager at Cincinnati Incorporated.

The formwork is made from a mix of recycled and virgin granules of carbon-filled ABS, as well as syntactic foam that is also ABS-based. The experiments achieved two goals: demonstrated a large-scale 3D printing with two and morematerials with programmed mechanical parameters and the ability to use recycled materials that result in saving resources and improved environmental friendliness of the products. Bringing the formwork as an example, it’s easy to save money printing working surfaces with expensive constructional materials, while using low-cost polymers for producing fillings and supporting structures.

“Studies have shown that by using multiple materials within a structure, new mechanical responses and multi-functionality can be achieved. This includes lightweight structures with tailored mechanical properties, soft and rigid segments within a part, and impact-resistant structures”, says Vidya Kishore, a material scientist at ORNL.