Michelle Rene Bezdecny

Stream-of-Variation Modeling—Part I: A Generic Three-Dimensional Variation Model for Rigid-Body Assembly in Single Station Assembly Processes

A stream-of-variation analysis (SOVA) model for three-dimensional (3D) rigid-body assemblies in a single station is developed. Both product and process information, such as part and fixture locating errors, are integrated in the model. The model represents a linear relationship of the variations between key product characteristics and key control characteristics. The generic modeling procedure and framework are provided, which involve: (1) an assembly graph (AG) to represent the kinematical constraints among parts and fixtures, (2) an unified method to transform all constraints (mating interface and fixture locators etc.) into a 3-2-1 locating scheme, and (3) a 3D rigid model for variation flow in a single-station process. The generality of the model is achieved by formulating all these constraints with an unified generalized fixture model. Thus, the model is able to accommodate various types of assemblies and provides a building block for complex multistation assembly model, in which the interstation interactions are taken into account. The model has been verified by using Monte Carlo simulation and a standardized industrial software. It provides the basis for variation control through tolerance design analysis, synthesis, and diagnosis in manufacturing systems.

Stream-of-Variation Modeling I: A Generic 3D Variation Model for Rigid Body Assembly in Single Station Assembly Processes

A stream-of variation analysis (SOVA) model for 3D rigid body assemblies in single station is developed. Both product and process information such as part and fixture locating errors are integrated in the model. The model represents a linear relationship of the variations between Key Product Characteristics (KPCs) and Key Control Characteristics (KCCs). The generic modeling procedure and framework are provided, which involves: (1) an assembly graph (AG) to represent the kinematical constraints among parts and fixtures; (2) a unified method to transform all constraints (mating interface and fixture locators etc.) into a 3-2-1 locating scheme; and (3) a 3D rigid model for variation flow in a single station. The generality of the model is achieved by formulating all these constraints with a unified generalized fixture model. Thus, the new model accommodates various types of assemblies. This model provides a building block for complex multi station assembly model, in which the inter-station interactions are taken into account. The model has been verified by using Monte Carlo (MC) simulation and a standardized industrial software. It provides the basis for variation control through tolerance design analysis, synthesis and diagnosis in manufacturing systems.Copyright

Additive manufacturing of PZT-5H piezoceramic for ultrasound transducers

This paper describes the development of a low-cost, high speed manufacturing process method for the fabrication of piezoelectric ceramic transducer elements in the 1-25 MHz frequency range. A modified multi-layer lithography process, is used to additively manufacture high-resolution netshape ceramic structures by photopolymerizing a ceramic-polymer slurry using structured light patterns. The paper elaborates on the key considerations in the development of the process including the selection and optimization of slurry materials for the deposition of PZT 5H materials, optical exposure parameters, debinding/sintering profiles and post-manufacturing processing. coupling coefficient in the range of 0.52-0.54. Ongoing work includes improvements to materials properties, improved throughput and geometric fidelity.

Prediction of Assembly Variation During Early Design

This paper presents the methods to move assembly variation analysis into early stages of aircraft development where critical partitioning, sourcing, and production decisions are often made for component parts that have not yet been designed. Our goal is to identify and develop variation prediction methods that can precede detailed geometric design and make estimates accurate enough to uncover major assembly risks. With this information in hand, design and/or manufacturing modifications can be made prior to major supplier and production commitments. In addition to estimation of the overall variation, the most significant contributors to assembly variation are also identified. In this paper, a generic framework for prediction of assembly variation has been developed. An efficient, top-down approach has been adopted. Instead of taking measurement everywhere, the variation analysis starts with airplane level requirements (e.g. load capabilities, orientation of horizontal/vertical stabilizers), and then assembly requirements (mainly geometric dimensioning and tolerancing callouts, quantifiable in Quality Control) are derived. Next the contributors to a particular assembly requirement are identified through Datum Flow Chain analysis. Finally, the major contributors are further characterized through a sensitivity study of Metamodels or 3D variation analysis models. A case study of a vertical fin has been used to demonstrate the validity of the proposed framework. Multiple prediction methods have been studied and their applicability to variation analysis discussed. Simplified design simulation method and Metamodel methods have been tested and the results are reported. Comparisons between methods have been made to demonstrate the flexibility of the analysis framework, as well as the utility of the prediction methods. Results of a demonstration test case study for vertical fin design were encouraging with modeling methods coming within 15% of deviation compared to the detailed design simulation.Copyright