D-Shape

D-Shape is a large 3-dimensional printer that uses binder-jetting, a layer by layer printing process, to bind sand with an inorganic seawater and magnesium-based binder in order to create stone-like objects. Invented by Enrico Dini, founder of Monolite UK Ltd, the first model of the D-Shape printer used epoxy resin, commonly used as an adhesive in the construction of skis, cars, and airplanes, as the binder. Dini patented this model in 2006. After experiencing problems with the epoxy, Dini changed the binder to the current magnesium-based one and patented his printer again in September 2008. In the future, Dini aims to use the printer to create full-scale buildings.

The current version of the D-Shape 3-D printer sits in a 6m by 6m aluminum frame. The frame consists of a square base that moves upwards along four vertical beams during the printing process via stepper motors, which are used to repeatedly move a specified length and then hold in place, on each beam. Spanning the entire horizontal 6m of the base is a printer head with 300 nozzles, each spaced 20mm apart. The printer head is connected to the base by an aluminum beam that runs perpendicular to the printer head.

Before the actual printing process can begin, a 3-D model of the object to be printed must be created on CAD, a software that allows a designer to create 3-D models on a computer. Once the model is finished, the CAD file is sent to the printer head. The printing process begins when a layer of sand from 5 to 10 mm thick, mixed with solid magnesium oxide (MgO), is evenly distributed by the printer head in the area enclosed by the frame. The printer head breaks the 3-D model into 2-D slices. Then, starting with the bottom slice, the head moves across the base and deposits an inorganic binding liquid made up of a solution that includes magnesium hexahydrate, at a resolution of 25 DPI (1.0 mm). The binder and sand chemically react to form a sandstone material. It takes about 24 hours for the material to completely solidify. Because the nozzles are 20mm apart there are gaps that may need to be filled up. To fill in these gaps and ensure the sand is uniformly exposed to the binder, an electric piston on the beam that holds the printer head forces the printer head to shift in the direction perpendicular to the printer's direction of motion. It takes D-Shape four forward and backward strokes to finish printing a layer. After a layer is finished, the stepper motors on the vertical beams move the base upwards. From the hollow framework just above the printer head, new sand, which is cyclically refilled, is distributed into the area of the frame to create the next layer. During printing, excess sand acts as a support for the solidifying sand and can also be reused in later printings. The printing process is continuous and stops only when the desired structure is completely printed.

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Wikipedia