Methodology and Tools for Testing, Numerical Analysis and Design of the 3D Printed Moulds

Abstract

The large-scale 3D printing technology created by a group of partners led by DUS Architects allows fabricating components made of thermoplastic polymers with Fused Deposition Modelling technique. These components can be used as moulds for concrete elements, providing freedom of form and unprecedented optimization opportunities. In this report the author investigates general applicability of the concept and makes an attempt to establish the relationship between laboratory tests, computational modelling and the design of an end product. This is achieved by developing a streamlined framework for processing the experimental outcome and using it in finite element simulation to find mould geometry, which deforms into the desired shape after casting the infill. The content of this report is contained in three factual sections. First of them covers preparation of the experiments and interpretation of their results. Main focus is put to mechanical response of the 3D printed cross sections in property tests (tensile, flexural, shear, creep, thermal sensitivity) and scale mould setups. Systematization of the output includes introduction of the print quality classes, which is a way to accommodate high variability in geometrical precision of the printer. Second part of the document describes and validates the proposed numerical approach using a triple-layer composite shell element with adjustable layer thicknesses. Implementation of the latter is driven by the inconsistence in cross-sectional stiffness parameters of an extruded wall in each direction. Next, the design method utilizing mentioned modelling technique is proposed. It is based on the principle of applying initial negative deformation, which compensates the excessive deflections that occur after casting the concrete. The above solutions are implemented with Python programming language and wrapped together in Rhinoceros 5.0 software with Grasshopper plugin. Finally, applicability of the framework is validated by the case study experiments on predeformed moulds. The discussion and conclusions argue that the use of the 3D printed components as forms for small concrete elements is feasible, but it is likely to exhibit issues with scalability. The test scheme is considered sufficient yet the print quality issues are highlighted. Likewise, numerical modelling technique and design method are acknowledged along with their drawbacks being mentioned. In the end, a list of potential improvements is given, including extension of the test scheme, development of a custom element formulation, changes in software implementation or alteration of the design procedure to enable its application to other problems.