Fixture design is an important consideration in all manufacturing operations. Central to this design is selecting and positioning the locating points. While substantial literature exists in this area, most of it is for prismatic or solid workpieces. This paper deals with sheet metal fixture design. An “N-2-1” locating principle has been proposed and verified to be valid for deformable sheet metal parts as compared to the widely accepted “3-2-1” principle for rigid bodies. Based on the “N-2-1” principle algorithms for optimal fixture design are presented using finite element analysis and nonlinear programming methods to find the best “N” locating points such that total deformation of the deformable sheet metal is minimized. A simulation package called OFixDesign is introduced and numerical examples are presented to validate the “N-2-1” principle and optimal sheet metal fixture design approach.

Manufacturing of lithium-ion battery packs for electric or hybrid electric vehicles requires a significant amount of joining such as welding to meet desired power and capacity needs. However, conventional fusion welding processes such as resistance spot welding and laser welding face difficulties in joining multiple sheets of highly conductive, dissimilar materials with large weld areas. Ultrasonic metal welding overcomes these difficulties by using its inherent advantages derived from its solid-state process characteristics. Although ultrasonic metal welding is well-qualified for battery manufacturing, there is a lack of scientific quality guidelines for implementing ultrasonic welding in volume production. In order to establish such quality guidelines, this paper first identifies a number of critical weld attributes that determine the quality of welds by experimentally characterizing the weld formation over time. Samples of different weld quality were cross-sectioned and characterized with optical microscopy, scanning electronic microscopy (SEM), and hardness measurements in order to identify the relationship between physical weld attributes and weld performance. A novel microstructural classification method for the weld region of an ultrasonic metal weld is introduced to complete the weld quality characterization. The methodology provided in this paper links process parameters to weld performance through physical weld attributes.

Automotive battery packs for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (PHEV) typically consist of a large number of battery cells. These cells must be assembled together with robust mechanical and electrical joints. Joining of battery cells presents several challenges such as welding of highly conductive and dissimilar materials, multiple sheets joining, and varying material thickness combinations. In addition, different cell types and pack configurations have implications for battery joining methods. This paper provides a comprehensive review of joining technologies and processes for automotive lithium-ion battery manufacturing. It details the advantages and disadvantages of the joining technologies as related to battery manufacturing, including resistance welding, laser welding, ultrasonic welding and mechanical joining, and discusses corresponding manufacturing issues. Joining processes for electrode-to-tab, tab-to-tab (tab-to-bus bar), and module-to-module assembly are discussed with respect to cell types and pack configuration.

Fixtures are used to locate and hold workpieces during manufacturing. Because workpiece surface errors and fixture set-up errors (called source errors) always exist, the fixtured workpiece will consequently have position and/or orientation errors (called resultant errors). In this paper, we develop a variational method for robust fixture configuration design to minimize workpiece resultant errors due to source errors. We utilize both first-order and second-order workpiece geometry information to deal with two types of source errors, i.e., infinitesimal errors and small errors. Using the proposed variational approach, other fundamental fixture design issues, such as deterministic locating and total fixturing, can be regarded as integral parts of the robust design. Closed-form analytical solutions are derived and numerical examples are shown. By employing the nonlinear programming technique, simulation software called RFixDesign is developed. This paper presents a new procedure for robust fixture configuration design that contributes especially to fixture designs where deformation is not influential.

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Sheet panels, represented as freeform surfaces in a CAD system, are widely used in manufacturing processes. Locating blocks and pins, collectively known as locators, are the most common fixtures for the joining and assembly of sheet panels. In this paper, a robust design approach is utilized to optimize the pin layout so that the sheet panel variations, expressed as translational and orientational variations at certain key product/process characteristic points (KPCs), are minimized. The advantage of this approach is that the locating variations at any given point on the panel can be obtained quantitatively, and hence, the optimal pin design can be selected from among an infinite set of feasible designs. Based on the analyses, some useful pin design guidelines will also be proposed.

This paper aims at providing a state-of-the-art review of an increasingly important class of joining technologies called solid-state (SS) welding, as compared to more conventional fusion welding. Among many other advantages such as low heat input, SS processes are particularly suitable for dissimilar materials joining. In this paper, major SS joining technologies such as the linear and rotary friction welding (RFW), friction stir welding (FSW), ultrasonic welding, impact welding, are reviewed, as well as diffusion and roll bonding (RB). For each technology, the joining process is first depicted, followed by the process characterization, modeling and simulation, monitoring/diagnostics/ nondestructive evaluation (NDE), and ended with concluding remarks. A discussion section is provided after reviewing all the technologies on the common critical factors that affect the SS processes. Finally, the future outlook is presented.

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