MILLING
Attaching the spindle as an end effector to the head plate of an industrial robot transforms the robot into a precise milling machine, which can be especially useful for load-bearing elements.
Milling is defined as a tooling process using a high speed-rotating spindle with an attached tool that grinds a fi ed work-piece. It is one method of tooling used in the building industry everyday. Although milling is a highly fl xible kind of tooling, the process is time consuming and compared to other tooling methods such as cutting it produces large amounts of waste. Besides the properties of the chosen material, taking into account that a material with higher stiffness also owns a higher grade of hardness, which may result in a longer and less economical production process, the way workpiece and tool are fi ed and clamped influences the strategy of each individual tooling process. Attaching the spindle as an end effec or to the head plate of an industrial robot transforms the robot into a precise milling machine, which can be especially useful for load-bearing elements, designed to pass on compression forces from one surface to the next. The large double curved roof structure of the Centre Pompidou in Metz, France, where timber was chosen for its material properties, and the Mansueto Library at the University of Chicago is designed as a steel grid shell show the direct influence and impact of material properties on the milling process. In the case of steel the goal of milling was to achieve a precise geometry for jointing while timber allows milling an overall double curved shape. In both cases the correlation between hardness, machinability of the material and the amount of waste material was taken into account, and the strategy of handling digital data within the manufacturing process from design to fabricating numerous non-uniform elements was optimized.
ROBOT MILLED PROTOTYPES The ABB IRB 6660 is sits on a high precise traversing rail to reach a range of operation of 6.0m x 1.2m x 1.2m.
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Rethinking design and research at Technical University Graz, required a recontextualization of all existing facilities of model building and structural testing equipment in the architectural workshops and mechanical labs. The faculty of architecture and civil engineering established the Roboter Design Labor focusing on Resource-efficient nonstandard Structures2 and installed the industrial
robot ABB IRB 6660, whose specification targets high precision milling. A characteristic that the Lab wants to use for producing high performance dry joints to connect prefabricated elements made form ultra-high performance concrete (uhpc). One of the Lab’s research goals is to proof the usability of this fl xible milling facility in a quasi-industrial environment. Robot based milling, as a low cost alternative may be the key to return knowledge on using industrial robots from architectural research to the building industry. The two case studies featured here describe the on-going approach at the Roboter Design Labor at Technical University Graz, where prototypes are used for testing the machining facility as a milling machine. The ABB IRB 6660 sits on a high precise traversing rail to reach a range of operation of 6.0m x 1.2m x 1.2m, which is part of the customized machinery. Beside the stiffness of the machine and the working table, orientation of the tool-center-point has to be taken in consideration. All boundary conditions clearly influence the milling process and the final result. In order to minimize possible failure and to predict the result of best fitting and milled surfaces we developed a measuring and compensating procedure. Nevertheless the process is controlled and driven by an engineer and the result depends strongly on the experience and knowledge of the design team.