Haeseong Jee

Robust fixture layout design for a product family assembled in a multistage reconfigurable line

Reconfigurable assembly systems enable a family of products to be assembled in a single multistage system by adjusting and reconfigurabling fixtures according to each product. The sharing of fixtures among different products impacts their robustness to fixture variation and process disturbances due to frequent reconfiguration. This paper proposes a methodology to achieve robustness of the fixture layout design through an optimal distribution of the locators for a product family. This objective is accomplished by: (1) the use of a multistage assembly process model for the product family, and (2) minimizing the combined sensitivity of the products to fixture variation. The optimization considers the feasibility of the locator layout by taking into account the constraints imposed by the different products and the processes (assembly sequence, datum scheme and reconfigurable tools workspace). The high dimension design space makes the problem challenging from the optimization point of view. A case study where three products are assembled in four stages is presented. The sensitivity of the optimal layout was benchmarked against the ones obtained using dedicated assembly lines for each product. This comparison proves that the proposed approach does not significantly sacrifice robustness while allowing the assembly of three products in a single reconfigurable line.Copyright

Surface macro‐texture design for rapid prototyping

Rapid prototyping technologies can create a physical part directly from a digital model by accumulating layers of a given material. Providing tremendous flexibility in the part geometry that they can fabricate, these technologies present an opportunity for the creation of new product attributes that cannot be made with existing technologies. For this to be possible, however, various design environments including different fabrication processes need to be considered at the time of design. This paper proposes an extended design automation paradigm for design and fabrication of a new product attribute, surface macro‐texture.

A method for modularity in design rules for additive manufacturing

Purpose As the technology matures, design rules for additive manufacturing (AM) can help ensure manufacturability, which can be viewed as compatibility between designs and the fabrication processes that produce those designs. Though often informal, current rules frequently provide direct guidelines or constraints for designing AM-destined parts. The aim of this paper is to standardize how design rules are developed and conveyed in AM by presenting design rules as sets of modular components and associated formalisms. Design/methodology/approach The proposed methodology decomposes fundamental geometry, process and material relationships into reusable modules. Independent of context, modular representations can be more easily interpreted and efficiently implemented than current one. By providing task-specific context, components are specialized to represent process-specific parameters for different AM builds and processes. This method of specialization enables designers to reconfigure design rules, rather than create new rules from scratch, thus preserving fundamental AM principles while supporting customization and explicit representation. Findings Modularity and formalisms provide both structure for the generalizations and a means to tailor that structure for a specific process, machine or build. The adoption of principles and formalisms that allow us to modify, extend, reconfigure or customize generalized rules as needed – instinctively and deliberately. Originality/value This method of specialization enables designers to reconfigure design rules, rather than create new rules from scratch, thus preserving fundamental AM principles while supporting customization and explicit representation.

Tolerance Design for Parts of a Sliding-Type Mobile Phone to Improve Variational Quality of Its Side Gap

Received 10 September 2012; received in revised form 6 November 2012; accepted 7 November 2012ABSTRACTThis paper investigates the tolerance stack-up in a commercial sliding-type mobile phone modeldeveloped by a Korean electronics company, with focus on the dimensional quality of the gapbetween the sliding top and the main body. The tolerance analysis in this study is done using acommercial software package, which runs Monte Carlo simulations to produce the statistical dis-tributions of the gap size at desired locations. Such an analysis revealed that the original designdid not yield the desired dimensional quality of the gap. Through a series of systematic analy-ses and syntheses, an improved design is proposed for the nominal dimensions and tolerances ofselected features of the parts. The proposed design was validated, through tolerance analysissimulation, to meet the desired requirement of the gap quality.Key words:Computer-Aided Tolerancing (CAT), Datum Flow Chain (DFC), Gap, Mobile phone,Tolerance analysis, Tolerance design

Design Rules for Additive Manufacturing: A Categorization

Additive manufacturing (AM) is gaining popularity in industrial applications including new product development, functional parts, and tooling. However, due to the differences in AM technologies, processes, and process implementations, functional and geometrical characteristics of manufactured parts can vary dramatically. Planning, especially selecting the appropriate AM process and material requirements can be rather involved. Manufacturability using AM processes has been well studied; however, gaps exist in the design process when catering to the needs of manufacturability. Designers today are challenged with a lack of understanding of AM capabilities, process-related constraints, and their effects on the final product. Challenges are compounded by the ambiguity of where design for AM ends and process planning begins. These ambiguities can be addressed through design principles and corresponding design rules for additively manufacturing parts. The purpose of this paper is to categorically present relevant and reported efforts in design and process planning with design rules in AM. The overarching goal of the review is to offer insights to extract and categorize fundamental principles for derivative rules for different AM processes. Identifying such fundamental requirements could potentially lead to breakthroughs in design and process planning.

Tolerance Analysis Considering Weld Distortion by Use of Pregenerated Database

A general and efficient methodology has been developed to analyze dimensional variations of an assembly, taking into account of the weld distortion. Weld distortion is generally probabilistic because of the random nature of welding parameters such as the welding speed, maximum welding temperature, ambient temperature, etc. The methodology is illustrated by a very simple example of two perpendicular plates fillet-welded to each other. Two steps comprise the methodology: establishment of a weld-distortion database, and tolerance analysis using the database. To establish the database, thermo-elasto-plastic finite element analyses are conducted to compute the weld distortion for all combinations of discrete values of major welding parameters. In the second step of tolerance analysis, the weld distortion retrieved from the database is used in addition to the dimensional tolerances of the parts. As a result of such an analysis, sensitivities of the assembly’s dimensional variations to the part tolerances and weld distortion are obtained, which can be help improve the dimensional quality of the assembly.Copyright