1.3.3. Methods of printing by injection into a particle bed 18.104.22.168. Presentation of this method The method of printing via an injection of fluids into a bed of particles is a printing method based on those developed for polymers and metals. The goal of this is to spread out a bed of particles of a given thickness, and then to make injections in the locations dictated by the numerical model of a fluid, allowing the grains to be agglomerated (Figure 1.17). Figure 1.17. Sequence of the execution of 3D printing by injection into a particle bed: 1) spread of a layer of particles, 2) lowering of the tray and 3) localized injection of the fluid [LOW 18] Two primary methods have been developed for cement-based materials. The first is to inject a very fluid cement paste into a bed of granulates (sand and/or gravel) [PIE 18, LOW 18]. The second method consists of injecting water (including some adjuvants if necessary) into a granular bed containing the cement-based binder and the granulates [LOW 18, SHA 17, WEG 16]. The second method has also been used for Geopolymers [XIA 16]. The pioneer of this method in the field of building materials is Enrico Dini, creator of the D-Shape method [LOW 18, CES 14]. These methods theoretically allow complex structures to be obtained with a precision of the contours on the order of magnitude of the diameter of the largest grain found in the granular mixture. This allows
3D Printing in Concrete: General Considerations and Technologies 23 it to obtain an excellent printing resolution. Figure 1.18 shows the surface quality obtained as a function of the size of the granulates used. Figure 1.18. Surface condition obtained as a function of a particle bed with granulates of the size: a) 0.2 mm; b) 2 mm; c) 4 mm [LOW 18] 22.214.171.124. The different scales of execution The method of injection into a particle bed can be used at the same time to make small components (Figure 1.19) [PIE 18]. For this type of execution, a small printer holding in a volume of one cubic meter is sufficient (Figure 1.19). Figure 1.19. Example of small productions and the printer used [PIE 18] y x z Comment [BR4]: Should this be “small components”?
24 3D Printing of Concrete It is interesting to note that the object printed in Figure 1.19 contains a sudden change between a vertical structure and a horizontal structure. The bed of particles acts in this case as a support, which allows the fluid to be kept in place, and allows total freedom in the forms produced (as is not the case for printing by extrusion/deposition). The works of Enrico Dini have also made it possible to create objects and structures on larger scales ([LOW 18, 44]). The D-Shape printer that he designed (Figure 1.20) has made it possible to build a pedestrian walkway and a structure several meters high, both at the same time (Figure 1.21).
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- Spring '19
- SHARAM DEROGAR
- General Considerations and Technologies