Sustainable Process Planning for Subtractive and Additive Manufacturing Unit Processes

Proceedings of the ASME 2016 International Manufacturing Science and Engineering Conference MSEC2016 June 27 to July 1, 2016, Blacksburg, Virginia, USA MSEC2016-8517 SUSTAINABLE PROCESS PLANNING FOR SUBTRACTIVE AND ADDITIVE MANUFACTURING UNIT PROCESSES Barbara Linke, Destiny Garcia, Gurpreet Kaur, Farhad Ghadamli University of California Davis Davis, CA, USA ABSTRACT Sustainability in manufacturing implies regarding economic, environmental and social aspects and is of increasing concern to companies and consumers. Traditionally, process planning decisions were mainly based on costs and quality. This paper shows a method to compare different process chains in terms of sustainability indicators. It proposes to include non- value adding steps such as quality control or transport. The method is explained with a case study, where students design, plan, manufacture, and test models for water table experiments. Common additive and subtractive manufacturing processes are applied. INTRODUCTION Sustainability includes an economic, environmental and social dimension, which is of increasing importance to manufacturers [1, 2]. Common factors considered are energy and material efficiency, emissions, waste, costs, productivity, investment, impacts on society, safety, health, etc. [3]. Product design including material and necessary manufacturing tolerances are a big lever for impacting a factory’s sustainability [4]. These choices are covered by product design and planning, covering which product types and versions are produced. Still, it needs to be detailed how the products are manufactured in terms of processes and parameters. In process planning the following questions are answered: - How many products are made in total and in which frequency and batch size? - Which manufacturing processes are used? - What are the parameters, machines, tools, auxiliary materials for each process? Process planning is an optimization problem to find the optimal process sequence with the associated optimal process parameters with minimum cost [5]. This offers great potential for sustainability improvements. The first decision is about which unit processes are chosen to manufacture the part. The same part can be made with many different unit processes and process sequences. For example, a tube can be cast or sintered near-net-shape, extruded from semi- finished parts, or bent and welded from sheet metal [6]. The evaluation criteria in process planning are plentiful: processing time, quality, availability, costs, energy, etc. [7]. It is often difficult to decompose the planning process into smaller steps, because most steps are influencing all other steps [8]. Also most manufacturing processes lack physical models that can be used to compute fast and accurate solutions, so human expertise is needed in process planning [8]. Additional challenges come from the new cloud based manufacturing environment in which decisions on process planning might become web-based, distributed and collaborative [9]. At UC Davis, a new course on integrated STEM education in aerospace design and manufacturing is under development, funded by the NSF IUSE (Improving Undergraduate STEM Education) program. This course will teach undergraduate students with simple mathematics what makes airplanes fly, while also showing how computer simulations, manufacturing, and experimental validation are integrated in the modern engineering world. To visualize the airflow, a water table experiment will be used to show shock waves around airfoils and other models (Fig. 1). The model surfaces need to be smooth to avoid turbulences. The dimensional accuracy is critical for the comparison between the computational simulation and the water table experiments. The students will need to produce the models during the course duration while considering sustainability in manufacturing. This is a relevant and timely topic. Airfoil Circle Diamond Bell-shaped nozzle FIG. 1 SHAPES FOR THE WATER TABLE EXPERIMENTS Copyright © 2015 by ASME