Determining the machining allowance for WAAM parts
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PRODUCTION PROCESS
Determining the machining allowance for WAAM parts Christina Fuchs1 · Daniel Baier1 · Thomas Semm1 · Michael F. Zaeh1 Received: 10 June 2020 / Accepted: 1 September 2020 © The Author(s) 2020
Abstract In order to decrease mass, and thus fulfil the targets for airplane traffic emission reduction, the amount of titanium alloys used for structural components is rising. With the conventional milling process, low material utilization and short tool life lead to high manufacturing costs. Therefore, a process chain consisting of wire and arc additive manufacturing (WAAM) and machining is developed. To realize its full potential, the machining process needs to be adapted to the near-net shaped components. A special focus lies on the machining allowance, since it influences both processes and in result the final part quality. In this paper a method to model the machining allowance is proposed and verified by analysing the changes from waviness to surface roughness occurring during peripheral milling of WAAM parts. Keywords Machining allowance · Milling · Ti-6Al-4V · WAAM · Additive manufacturing
1 Motivation The European Commission’s objective to reduce the amount of nitrogen oxides (NOx) and carbon dioxide (CO2 ) per kilometer flown leads to a need to lower the fuel consumption of airplanes considerably [1]. Reduced airplane weight helps to achieve this goal, which in turn compels the increasing use of lightweight titanium alloys such as Ti-6Al-4V [2]. The conventional machining for airplane structural components made from Ti-6Al-4V is mainly done by milling from slab. The ratio of the raw materials’ weight to the weight of the material used in the aircraft is called the Buy-to-Fly (BTF)ratio. For structural components this ratio, depending on the part, can approach 37, when a conventional milling process is used [3]. Due to the contamination of the chips with cooling lubricants, this leads to a large amount of material waste [4] and, since Ti-6Al-4V is a difficult to machine material [5], to high manufacturing costs. In order to reduce the production costs for these parts, a process chain, which consists of additive manufacturing and machining, was developed. Since the machine tools for conventional machining already are present in * Christina Fuchs [email protected] 1
Institute for Machine Tools and Industrial Management, Department of Mechanical Engineering, Technical University of Munich, Garching, Germany
most manufacturing companies, a sequential setup on two machines, one for additive manufacturing and one for machining, was preferred over one specialized hybrid machine tool. For the additive manufacturing process wire and arc additive manufacturing (WAAM) was selected, because this process allows the production of structural components with large outer dimensions [6]. To ensure that the final part quality is met, the minimum amount of material needed to be removed from the near-net shaped part has to be determined. Otherwise, not or notsufficiently machined surfaces remain on
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