Case Studies

Case Studies

Measurement Systems Analysis – 3D Non-Contact

These papers examine measurement systems analysis issues in the application of 3D Non-Contact measurement. In the first case study, we compare measurement system error (repeatability, reproducibility and accuracy) between an Optigo 3D Non-Contact System and a traditional CMM. In the second case study, we review several common alignment or registration methods and provide a metric to assess systematic alignment error. Using a case study, we show that for the same basic datum scheme provided on engineering drawings, the potential systematic alignment error may be a far more significant issue for problem solving than repeatability error or equipment accuracy.
Click here to read case study 1 (PDF) | Click here to read case study 2 (PDF)

Functional Build

This paper explores the use of functional build techniques for manufacturing process validation and discusses its implementation at several manufacturers. When functional build is used, manufacturers may realize substantial cost savings over a traditional process development approach. These savings result from eliminating unnecessary process rework during the validation phase. Under functional build, rework decisions focus on meeting final assembled product objectives and not necessarily on conformance of detail components to their original specifications. For additional information on Functional Build, please contact us or reference the research by Dr. Patrick Hammett at the University of Michigan.
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Datum Transformation Analysis/Exterior HeadLamp Fit

This paper presents a comprehensive dimensional validation methodology, known as datum transformation analysis (DTA). The DTA approach utilizes 3D non-contact (3DNC) measurement to obtain a full part dimensional representation at all critical matching interfaces of a part assembly to the vehicle. Next, a part measurement re-alignment process is applied to identify new positions for the assembly datum locators that optimize the overall product quality at these matching interfaces. Next, datum locations are adjusted at the component level (at the same physical location as the corresponding assembly) to improve mean conformance of the assembly dimensions. The adjustments to the datum locators at the component level are not necessarily made to improve component quality, but rather to optimize final part assembly. This DTA methodology is demonstrated using an automotive headlamp assembly. In this case study, we identify tooling rework moves using DTA to increase the percent of critical assembly dimensions whose mean values are within ±0.25 millimeters from 20% to 90%.
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Sheet Metal Stamping Die Tryout and Rework

This report summarizes automotive body die tryout performance, based on a survey and interviews with die manufacturing experts from automotive body manufacturers and die suppliers, The report explores opportunities for more effectively integrating new 3D non-contact optical measurement technologies during the die tryout process to improve performance. It provides basic guidelines for optical measurement data collection for stamping dies and resultant parts as well as analysis methods.
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Dimensional Slow Build Study – Fabricated Metal Assembly

This paper describes a methodology known as a Dimensional Slow Build to determine the root cause of dimensional changes from components through in-process assembly steps and ultimately a final assembly. A front door assembly process is used to illustrate the approach. Among the key findings in this study are the importance of understanding the effects of the datum-locating scheme and the significant influence of assembly processing variables, rather than stamping component variability, on the final door assembly dimensional quality.
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3D Non-Contact/Scanning Metrology

This report examines the usage of 3D non-contact measurement technology and how its adoption could impact traditional North American automotive body dimensional evaluation strategies from die tryout through PPAP. The report includes several WL measuring studies involving a longitudinal analysis of door components and their resultant assembly throughout the preproduction process. It provides several recommendations for new part measurement strategies and business processes for automotive body stamped parts and subassemblies. The recommendations support a part quality evaluation process that places a greater emphasis on measuring overall part shape and feature conformance as well as intra-panel correlation patterns (e.g., twists and feature-to-feature relationships) versus process capability conformance of discrete points to individual specifications. These recommendations include adopting percent in specification metrics such as PIST, reducing measurement sample sizes for both tryout runs and PPAP, and utilizing new methods for analyzing and reporting part dimensional data. These new methods are aimed at providing more comprehensive part quality representation to increase the utility of dimensional measurement data for end-users.
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Tolerance Modeling and Analysis

This report provides a methodology for tolerance analysis and adjustment of multi-dimensional components. The application of this methodology was developed for and has been adopted by a North American OEM as a standard practice for dimensional evaluation and revision of sheet metal stamped components. The methodology was validated during a vehicle program launch by calculating tolerance recommendations for several stamping parts. The results showed that the methodology was able to predict over 90% of the actual variation levels and subsequent process monitoring demands observed later in production.
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Past Clients

MVS (through direct contracts or University of Michigan research projects) has provided dimensional engineering, quality integration, functional build and training services for several large clients including: General Motors, Harley-Davidson, Chrysler, Ford Motor Company, Visteon, The Vehicle Production Group, Fuji Technica, CogniTens, Hexagon Metrology, ASC, Innovative Body Solutions, NUMMI, Renault, and International Truck.

MVS’ largest activities have involved dimensional engineering and manufacturing validation support for new vehicle launches. Here, MVS provides measurement and process improvement support, lead dimensional slow builds, and provide top down analysis relating key final vehicle metrics to individual components. In addition, MVS performs Fixture-Fixture Repeatability Studies, Weld/Heat Deformation Studies, Digital Assembly Evaluations, and Functional Master Part Feasibility studies including reverse engineering and surfacing using Tebis and Polyworks Software.

MVS’ largest dimensional engineering project involved the highly successful GM HHR launch. Here, MVS supported the development of the body dimensional control strategy, the functional build event plan, managed the welds for the entire body, provided GD&T and check point drawings, and created master data models to ensure weld, datum, and check point coordination.