Concrete 3d printer

University essay from Lunds universitet/Produktutveckling

Abstract: In this project the aim was to design a concrete 3d printer. This report focuses on the extruder part of the printer and the printing material. The basic principle of 3d printing is that it is an additive manufacturing technique, on the contrary to the traditional subtractive manufacturing techniques. The potential benefits of concrete 3d printing compared to the techniques that are used today are that it could be a cheaper, faster and more environmentally friendly manufacturing process. The methodology used to develop the design was taken from Ulrich & Eppinger`s Product design & development. A modified version of the general product development process was used for the project. The product specification from the start was that the concrete 3d printer would be able to create a line of concrete, 30-40 mm wide and 10-20 mm high. When this had been achieved it was thought that the printer would be able to manufacture street furniture. To accomplish the product specification some key features of the extruder were considered. They were the orifice shape, side trowel design and flow creating mechanism. From evaluation matrices it was decided that the conceptual design of the extruder would have a square orifice, two rectangular side trowels and a rotating auger to create a flow of concrete. To assess how well the design fulfilled the specification a prototype were manufactured that abled testing in reality. The first test was carried out with a sand- and water mixture due to its recyclability. In the early stages of testing it was observed that a) a more powerful motor was needed, b) that instead of a planar bottom part a cone-shaped bottom part was necessary and c) an overall need for more robust materials for the extruder was demanded. After each test improvements were made on the extruder to be followed by additional tests. When a design that worked in principal was found different printing materials were tested such as mortar, standard concrete and EPS-cement. It was found that in order for the extruder to work the material could not be too viscous and thereby block the orifice. However, it was also understood that the material would have to be viscous enough to be able to support itself and build several vertical layers. Therefore a special mixture of concrete was needed to satisfy both these requirements. A special mixture of concrete was tested and the results were very good. It was able to be extruded but also had the ability to build vertical layers. A chair made of the concrete was printed. The conclusion of the tests was that the working mechanism of the extruder is suitable for this application. However, there is need for a specially mixed concrete like the one used in the project for it to be both extrudable and buildable.

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