AKROPOLYS - IAMHH e.V. Collaborative Project

In the face of advancing climate change, Germany is also participating in the implementation of the global sustainability goals of the United Nations 2030 Agenda for Sustainable Development. New laws are constantly being developed in Germany and the EU to comply with and regulate products produced and sold in the EU. In particular, there is a need for a sustainable circular economy in the industrial production of polymer components.

A key requirement here is the preservation of material and product quality across several recycling stages and a clear recycling concept for the reuse of materials in production and of products that have to be reprocessed at the end of their life cycle. To date, however, there has been a lack of reliable findings on the recyclability of additively manufactured (AM) components, particularly with regard to the entire process chain from material production to the end of the product life cycle.

Establishing a circular economy for additive production with polymers (polymer components)

In the AKROPOLYS project, a cross-product and cross-technology circular economy for AM processes with the material polyamide 12 (PA12) is being established with partners from the Hamburg metropolitan region and various industries, taking into account the product life cycles. The aim is to recycle as much of the materials and products as possible by preparing the used powder from the SLS process and processing it further in the injection molding and material extrusion processes (FFF, FGF). The applications under consideration are highly functional lightweight construction products, production aids and consumer applications as well as innovative designs in the art sector.

The concrete starting point for this pilot project by IAMHH e.V. is the foreseeable sustainability requirements of the EU. According to these, all plastic components in a vehicle will have to be made from a certain proportion of recycled polymer components in future. As part of AKROPOLYS, six Hamburg partners - three small and medium-sized companies and two research institutions - are building a circular economy for additive production with polymers (polymer components). Hamburg-based Lehmann&Voss&Co KG is leading the project as consortium leader - and sixth partner. 

»AKROPOLYS bundles the expertise available in Hamburg in an ideal way to provide the industry with sustainable materials for challenging applications.«

Dr. Stefan Schulze, Director 3D Printing Materials bei Lehmann&Voss&Co. KG

The recycled materials and end products must not only meet EU requirements, but also industry standards. These include color and haptic as well as mechanical properties. This is where the four associated partners of the pilot project, including two large industrial end users from the mobility sector, come into play. They specify products and product features in which the recycled materials are to be processed.

The AKROPOLYS joint project, with a total project sum of around 2.5 million euros, has received a funding commitment of around 1.75 million euros from the Hamburgische Investitions- und Förderbank (IFB) of BWI.

Our role in the project

• Testing the extrusion performance and material properties of filaments prepared from SLS used powders in the FFF process
• Development of a system based on laser diodes that can be directly integrated into the process for direction-independent smoothing of inner and outer surfaces
• Investigations into the flowability, mechanical and surface properties of FFF components made from recycled materials
• Development of a digital sustainability passport that enables digital identification of the materials, documentation of the process history and CO₂ consumption as well as verifiable compliance with legal regulations
• Participation in design concepts with a focus on simple recycling “Design for Circularity”
   

Material and process development

During the course of the project, PA12 powder from SLS printing was successfully converted into processable granules and filaments. This recycled PA12 was examined at the IAPT with regard to LuMEx technology. A series of spectroscopy experiments identified suitable wavelengths that allow laser processing of white material. The lasers selected on the basis of these tests were used for smoothing tests with white recycled PA12 filaments. Surface roughness measurements show a significant reduction in roughness from as-built surfaces (Ra = ~17 µm) to Ra < 3 µm for LuMEx-smoothed surfaces. This value corresponds to the quality of conventional surface finishing processes.

Microscope images of printed samples made from recycled white PA12:

Digital Product Passport

The digital product passport creates transparency throughout the additive circular production of polymers, from the materials used to the carbon footprint. The structured collection and provision of product and process data in standardized asset administration shells (AAS) enables traceable and EU-compliant documentation. A web-based platform allows easy access to this information in order to obtain essential product information and share this information between suppliers and users. In this way, the DPP makes an important contribution to sustainable and digitally networked production. At the current stage, the technical basis has been successfully implemented: the AAS structure has been implemented in an executable form, data communication has been established, and the web-based front end for user-friendly access is under development.