Generating reversible interlocking structures for non-compatible FDM polymers

Abstract

In the field of 3D printing, Multi Material Additive Manufacturing (MMAM) has gained substantial recognition, as it offers interesting new possibilities. MMAM allows the combination of diverse polymers to create products with enhanced, composite properties. However, a significant challenge emerges when chemically incompatible polymers are combined within this technique, which complicates recyclability. This research addresses the issue of connecting these polymers while preserving strength, durability, and the capacity for disconnection, which facilitates efficient recycling at the end of a product’s life cycle.

Polymers, while versatile and widely used, often prove to be chemically incompatible due to their distinct chemical compositions and inherent characteristics. This incompatibility becomes a major bottleneck in the field of MMAM, as it obstructs the effective adhesion of polymers to each other. The result is products that are exceedingly challenging to recycle, perpetuating a long-standing issue in the 3D printing domain. Conventional industry solutions, primarily reliant on mechanical interlocking methods, lack the necessary flexibility for disassembly, rendering the materials inseparable and hindering recycling. This issue has long hampered the establishment of a sustainable 3D printing ecosystem.

To conquer this challenge, this research introduces the “Z-pin” connection, a novel reversible interlocking method. The Z-pin method serves as a bridge connecting chemically incompatible polymers and offers an approach that exceeds current alternatives. The introduction of the Z-pin’s design helps the joining of different polymers while still facilitating their clean separation when necessary.

The Z-pin method is most novel in its remarkable capacity for disconnection. By subjecting the polymer connection to controlled heating, within a range of 60 to 95 degrees Celsius, this method facilitates the simple, clean, and efficient separation of materials. Most notably, this process can be executed with basic tools and, in certain scenarios, by manual disassembly.

The developmental process of the Z-pin method comprised three phases. The first phase involved the initial design and evaluation of a range of connection methods. Two methods that demonstrated great potential were selected for further refinement in the second phase. Here, an optimisation process took place, including geometry, print parameters, and material properties. The third phase was dedicated to implementing the enhancements identified in phase two, culminating in a comprehensive and finalized design. This iterative methodology addressed the extensive range of possibilities uncovered during preliminary research.

The research affirms the performance of the Z-pin method over conventional solutions, including the hacksaw and alternating layer methods. The Z-pin method has an impressive tensile strength, positioning it as a contender within the MMAM domain. Furthermore, its straightforward geometry affords scalability and adaptability, enabling it to meet the specific prerequisites of a diverse array of applications.