3D printing aides in increasing the customization when it comes to design, reducing the Construction schedule, the labor required on site and the cost that goes into construction. Currently, there is the potential to 3D print large-scale buildings, while there are also limitations such as the development of Building Information modeling, the desire to be able to customize in large numbers and the high life cycle cost of printed projects.
The effort is being made to increase customization, reduce the construction schedule and make the 3d printed buildings more affordable. Labor productivity issues, work-related injuries, and illnesses of the workers can be greatly reduced with the process. The focus is also towards finding out different ways to automate the construction process, accelerate the rate of production and reduce the waste produced during the construction process.
Keywords: Computer aided system, customization, large scale buildings, construction schedule, life cycle cost, labor issues.
According to Klot et al. (2007), buildings consume 36 percent of total energy used, 30 percent of raw materials used, and 12 percent of potable water used. The construction Industry is also perceived to be a low-tech industry with very low levels of innovation. That trend is slowly changing as the building process becomes more automated .
3D Printing Process
The selection of appropriate printing process depends on the budget, time needed for printing, the accuracy of the printed model and the material options available for distribution. Five types of 3D printing process 1. Stereolithography 2. Fused Deposition Modeling (FDM) 3. The inkjet powder printing process 4. Selective Laser Sintering (SLS) 5. Contour Crafting (Peng Wu et al. 2016)
3D Printing Technology In The Building And Construction Industry
Material deposition method
Contour crafting is an additive fabrication technology, that prints a building in place. The system includes a Gantry and a nozzle. As the printing material comes out of the nozzle, computer-controlled trowels are used to apply and spread the concrete. Maintaining a uniform level of viscosity is a challenge in Contour Crafting.
D-Shape is a factory gantry-based powder-bed, which can print up to 6m x 6m x 6m of Architectural structures. The technology has a smaller resolution of deposition 94- 6mm regarding layer depth, thus allowing control of internal and external geometries. The printer works on a powder deposition process, where the binder is used to harden selective layers of printing material.
According to Peng Wu et al. (2016) the practical obstacles that were identified when WinSun printed a 2-storeyed villa and a five storied apartment in 2014 were, 4.1. Indirect process Construction components are printed in a closed factor or an off-site location, then transported to the site and put together like a puzzle block. While installing precast concrete components, direct contact was often used instead of joints that are usually used in conventional buildings.
For load bearing components and construction components which p horizontally such as slabs, staircases, adding glass fiber to concrete to increase its strength, also made the concrete too brittle to solve the purpose. For it to work, the material had to be printed as molds. One of the intents behind the use of 3D printing is to eliminate demoulding. Even in case of C-Fab printing process, the use of Carbon fiber also lead to the brittleness of printing material. (Moltich-hou, 2015)
Exclusion of Building services
As Building services such as electrical and plumbing were not included in the 3D printing process, additional work had to be done on the already printed 3D model which causes structural integrity related issues.
3d Printing And Building Information Modeling
3D modeling essential goes through 6 steps - digital modeling, exporting, slicing, connecting, printing and finishing (Peng Wu et al. 2016). The advantage of using BIM is it covers not only the geometric information, but also critical information such as material performance, spatial relationships, and manufacturer information. Aids in the construction on complicated structures with complex geometries that might not be possible to build efficiently using conventional construction process.
Integrating BIM process helps reduce the lead time by combining each step in the process of design into the final building output. Building information modeling also proves to be a very effective communication tool between different stakeholders such as designers, owner, contractor and sub-contractors. While making the model two critical issues need to be addressed. The first issue is to know the 3D printer’s capabilities, the materials that can be printed using the device.
This information is vital when deciding if the model can be printed as one unit or if it has to be printed as fragments and then assembled. The second issue is to check for clashes in the assembly using BIM before making the actual model on site. Different systems in the buildings must be tested in relationship with each other. Design for Manufacturing approach (DfMA) is an approach that emphasizes the inclusion of manufacturing and assembly knowledge during the design phase (Lyon, 2011). This approach leads to simpler and more reliable products which are less expensive to assemble and manufacture. (Boothroyd, 1994).
The two-story house in China, measuring 400sq.m, built by Beijing based Hua Shang Tengda in 2016 (3dprint.com)
Office building in Dubai, UAE measuring 250 sq.m. 2016, by Chinese construction company Winsun. The building was printed using a 120 x 40 x 20 feet 3D printer, featuring the automated Robotic arm (cnet.com 2016a, Media office.ae 2016)
Interior of a hotel Suite measuring 12.5 x 10.5 x 4m, in the Philippines, completed 20 September 2015, by totalKustom (Totalkustom.com 2016a)
The five-story apartment Building in Suzhou, China finished in Jan 2015 by Winsun (cnet.com 2016).
Also in Suzhou, China, an 1100 sq.m villa, by Winsun, completed early 2015.
Children's castle, Minnesota, USA, ended August 2014, by total Kustom (Totalkustom.com)
Series of 10 houses, in Suzhou, China, by Winsun 2014. Printed with a massive 150 x 10 x 6.6m printer (Wu et al. 2016).
The plastic canal house
2014 DUS Architects (a Dutch firm) built a canal house out of 3D printed plastic in Amsterdam. Kamer maker, which is a giant crane-like printing arm was used for the process. Indirect process of 3D printing is used where each room is printed separately on site before its assembled into one house. The rooms are thus tested in a safe and easily accessible manner. Each printed room is then joined together as large Lego-like blocks.
The 3D printed walls have in-built provision for connecting cables, pipes, communication technique, wiring etc. (Head, Heather. “A History of 3D Printing in Construction & What You Need to Know.” Connect & Construct, connect.bim360.autodesk.com/3d- printing-in-construction.)
The primary source of risk on site is a collision with the machine, falling and the engine running over. Existing workers who are already trained in the conventional building system might need to be taught again on the latest 3D available technology.
The scale of the project printed is a significant limiting factor as the selection of 3D printing technology used depends hugely on it. With the ongoing researches on exploring different materials used in 3D printing - their properties such as quick hardening, strength, and stability, selecting the right combination of elements and integrating it with the technology can prove to be difficult. To verify if the 3d printed building can withstand adverse climate is another enormous challenge.
Dust from 3D printing. Concrete in its presetting state for the duration of the printing session. The buildability is limited, as it depends on the relatively low stiffness and strength of the printed green; filament. A huge challenge would be to integrated building code with the 3D printing process. Figure out how to effectively integrate different aspects such as insulation, fireproofing, wind loads, foundations.
As the technologies in 3D printing become more evolved, factors such as cost, the precision of the model, reliability of the machine will get better, thus making it a more common means of construction.
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