Browsing by Subject "Design guidelines"
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Item A compilation of design principles and guidelines for selective laser sintering(2016-05) Pradhan, Nivedita; Seepersad, Carolyn; Crawford, Richard HThe term Additive Manufacturing (AM) is used to describe several manufacturing technologies that share the same basic principle of producing parts directly from their CAD models without the need for special tooling, by adding material selectively one layer at a time. Current research focuses on one such technology called Selective Laser Sintering (SLS) where thin layers of powdered thermoplastic material are fused using a laser beam. With no part-specific tooling required, the product development cycle is drastically shortened. This lack of tooling, coupled with freedom of placement of material, opens the door to several design opportunities unique to AM such as increased geometrical design freedom and the ability to manufacture low production volumes economically. Gradual improvements in process accuracy and selection of materials over time have resulted in a shift in application of AM from rapid prototyping to direct manufacturing and even ‘democratization’ of the product development process in which even non-professional users can rapidly manufacture products as long as there is a CAD model for the part. However, the move to direct manufacturing of end-use parts also means that part quality in terms of conformance to product specification becomes important for the product to successfully perform its function. The research in this thesis is focused on documenting these manufacturability capabilities and limitations for Selective Laser Sintering. It focuses specifically on thermoplastics, especially Nylon 12 polyamide materials known by the trade names PA 2200 and Duraform PA. While several design resources have been created based on industry best practices developed through experience, they are scattered throughout the literature and are not readily available to designers. It is also difficult to compare and draw quantitative inferences from existing guidelines as they are developed independently under dissimilar process conditions. Therefore, a prime focus of this research is to synthesize and compile existing guidelines into a comprehensive document. The first objective of this research is to compile a user-friendly resource, in the form of design principles and guidelines, to help designers make early process selection decisions, optimize part quality and minimize manufacturing cost. A systematic literature review of available guidelines, exploratory studies and case studies is conducted to develop actionable design recommendations that are within the scope of the designer. The second objective of this research is to address the lack of adequate process tolerance information that can reliably predict the quality of parts produced by the selective laser sintering process. This information is important to accurately evaluate the process during early process selection. A test part is proposed to measure dimensional deviations for various features (such as holes, gaps, cylinders, walls, clearances, etc.) across a range of dimensions and along different orientations. Finally, a sampling plan that represents sources of variability in the process is put forward to collect statistical data in an economical manner.Item Flow in multitasking : the effects of motivation, artifact, and task factors(2014-08) Park, Ji Hyun, active 21st century; Bias, Randolph G.The aims of this dissertation study are 1) to examine how the interplay of motivation, artifacts, and task interconnectedness affect users' flow experience, 2) to understand users' multitasking patterns by analyzing approaches and strategies in multitasking environments through a participatory design session, and 3) to come up with design insights and implications for desired multitasking environments based on findings from the quantitative and qualitative data analysis and synthesis. This dissertation employed the PAT (Person-Artifact-Task) model to examine factors that affect users' flow experience in computer-mediated multitasking environments. Particularly, this study focused on users' flow experience - sense of control, focused attention, curiosity, intrinsic interest and interactivity - in the context of multitasking. The dissertation begins with perspectives on human multitasking research from various disciplines. Emphasis is placed on how researchers have defined the term multitasking and the scope of previous multitasking research. In addition, this study provides definitions of the term task switching, which also has been used to describe human multitasking. The second section of this dissertation focuses on the literature, which characterizes factors and theoretical frameworks of human multitasking research. In this section, human multitasking factors were classified into internal and external factors to analyze factors from the micro to the macro perspective. More detailed definitions and comparisons are also addressed. To summarize and conclude the literature review, this study provides a synthesis framework of internal and external factors of human multitasking contexts. In section III, this dissertation introduces theoretical frameworks that include the constructs of the PAT (Person-Artifact-Task) model and flow model. The next three sections present the research design and two research methods - the experiment and participatory design. The results and discussion section includes the implications of interpreting people's flow experience with motivation, artifact (technology affordance type), and task interconnectedness through the PAT model. The study findings and implications should extend our understanding of multitasking behaviors and contexts and how the interplay of person, artifact, and task factors affects humans' flow experience. A concluding chapter explores future work and design implications on how researchers and designers can take contextual factors into consideration to identify the most effective multitasking in computer-mediated environments.