White light measurement: a catalyst for change in automotive body dimensional validation. Measurement strategies for stamping and body assembly from tryout through PPAP

This report examines the usage of 3D non-contact white light (WL) 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.General Motors Corporation, Body Manufacturing Engineering North America, Pontiac, Mich.http://deepblue.lib.umich.edu/bitstream/2027.42/15514/1/99394.pd

Fuel-saving technologies and facility conversion: costs, benefits, and incentives

Includes bibliographical references (p. 42)Technical report. 2003-2009National Commission on Energy Policy, Washington, D. C.Michigan Environmental Council, Lansinghttp://deepblue.lib.umich.edu/bitstream/2027.42/3129/2/98560.pd

Identifying Sources of Variation in Sheet Metal Stamping

Manufacturers using traditional process control charts to monitor their sheet metal stamping processes often encounter out-of-control signals indicating that the process mean has changed. Unfortunately, a sheet metal stamping process does not have the necessary adjustability in its process variable input settings to allow easily correcting the mean response in an out-of-control condition. Hence the signals often go ignored. Accordingly, manufacturers are unaware of how much these changes in the mean inflate the variance in the process output.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45507/1/10696_2004_Article_5122944.pd

Integrating 3D non-contact measurement in the die tryout business process

Based on two surveys of manufacturers, this report summarizes several automotive body die tryout buyoff criteria, rework processes, and 3D non-contact measurement strategies. Relative to historical die tryout performance levels, a significant reduction in the number of iterations is clearly achievable through the following: Improved ability to create die compensation models to create new machine files to rework parts closer to nominal without significant unintended consequences. Changes to existing die and production source part approval processes to make better decisions about when rework is needed to produce a dimensionally acceptable body. Related to these improvements is the need for an effective business process integrating 3DNC measurement with new part approval processes to help manufacturers reduce the number of die rework iterations. A cowl top case study demonstrates the application of this process in effective use of 3DNC measurement to reduce the number of tryout iterations to only one rework loop.Center for Automotive Research, Ann Arbor, MINational Institute of Standards and Technology, Gaithersburg, MDhttp://deepblue.lib.umich.edu/bitstream/2027.42/61820/3/102173.pd

Improving die rework capability: Opportunities for using 3D non-contact measurement technology to reduce die tryout iterations to resolve dimensional issues

This report summarizes automotive body die tryout performance, based on a survey of and interviews with die manufacturing experts from automotive body manufacturers and die suppliers, The report explores opportunities for more effectively integrating new 3D noncontact 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. For medium-complexity parts, the study participants estimate that a typical number of die tryout iterations is five to nine over a nine to 14 week period using typical North American tolerances and part acceptance criteria. The key enablers to reduce die tryout time were advancements in die forming and simulation software, particularly for complex materials, as well as advancements in virtual assembly tools.Center for Automotive Research, Ann Arbor, MINational Institute of Standards and Technology, Gaithersburg, MDhttp://deepblue.lib.umich.edu/bitstream/2027.42/61821/1/102174.pd

Datum transformation analysis for production part approval using 3D non-contact measurement

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%.Visteonhttp://deepblue.lib.umich.edu/bitstream/2027.42/61819/1/102172.pd

Quantifying alignment effects in 3D coordinate measurement

The use of fixtureless, non-contact coordinate measurement has become increasingly prevalent in manufacturing problem solving. Manufacturers now routinely use measurement systems such as white light area scanners, photogrammetry, laser trackers, and portable laser scanners to conduct studies that require measuring upstream supplier parts, tooling, or in-process subassemblies. For part measurements in these studies, certified fixtures with alignment features such as tooling balls often are not available. Instead, manufacturers rely on ad hoc part-holding fixtures or measure parts without fixtures and perform alignments mathematically. Here, advancements in software are providing operators with numerous alignment options, and users are actively using this functionality. Naturally, these additional capabilities have led to inconsistencies in the alignment method used across measurement studies, often affecting dimensional results. This paper reviews several common alignment or registration methods and provides a metric to assess systematic alignment error. To demonstrate alignment effects, we present a measurement system study of a moderately complex part requiring an over-constrained datum scheme. We first measure the part using a conventional fixture-based method to establish a baseline for static and dynamic repeatability. We then compare these with results from two mathematically-based iterative alignment methods based on fixtureless measurement. Next, we assess the systematic alignment error between the different fixture/alignment alternatives. We show that for the same basic datum scheme provided on engineering drawings, the systematic alignment error is a far more significant issue for problem solving than the repeatability error or equipment accuracy.http://deepblue.lib.umich.edu/bitstream/2027.42/69245/1/99983.pd

Patterns of HIV prevalence among injecting drug users in the cross-border area of Lang Son Province, Vietnam, and Ning Ming County, Guangxi Province, China

BACKGROUND: To assess patterns of injecting drug use and HIV prevalence among injecting drug users (IDUs) in an international border area along a major heroin trans-shipment route. METHODS: Cross-sectional surveys of IDUs in 5 sites in Lang Son Province, Vietnam (n = 348) and 3 sites in Ning Ming County, Guangxi Province, China (n = 308). Respondents were recruited through peer referral ("snowball") methods in both countries, and also from officially recorded lists of IDUs in Vietnam. A risk behavior questionnaire was administered and HIV counseling and testing conducted. RESULTS: Participants in both countries were largely male, in their 20s, and unmarried. A majority of subjects in both countries were members of ethnic minority groups. There were strong geographic gradients for length of drug injecting and for HIV seroprevalence. Both mean years injecting and HIV seroprevalence declined from the Vietnamese site farthest from the border to the Chinese site farthest from the border. 10.6% of participants in China and 24.5% of participants in Vietnam reported crossing the international border in the 6 months prior to interview. Crossing the border by IDUs was associated with (1) distance from the border, (2) being a member of an ethnic minority group, and (3) being HIV seropositive among Chinese participants. CONCLUSION: Reducing the international spread of HIV among IDUs will require programs at the global, regional, national, and "local cross border" levels. At the local cross border level, the programs should be coordinated on both sides of the border and on a sufficient scale that IDUs will be able to readily obtain clean injection equipment on the other side of the border as well as in their country of residence

Prehospital ticagrelor in ST-segment elevation myocardial infarction

Background:The direct-acting platelet P2Y receptor antagonist ticagrelor can reduce the incidence of major adverse cardiovascular events when administered at hospital admission to patients with ST-segment elevation myocardial infarction (STEMI). Whether prehospital administration of ticagrelor can improve coronary reperfusion and the clinical outcome is unknown. Methods: We conducted an international, multicenter, randomized, double-blind study involving 1862 patients with ongoing STEMI of less than 6 hours' duration, comparing prehospital (in the ambulance) versus in-hospital (in the catheterization laboratory) treatment with ticagrelor. The coprimary end points were the proportion of patients who did not have a 70% or greater resolution of ST-segment elevation before percutaneous coronary intervention (PCI) and the proportion of patients who did not have Thrombolysis in Myocardial Infarction flow grade 3 in the infarct-related artery at initial angiography. Secondary end points included the rates of major adverse cardiovascular events and definite stent thrombosis at 30 days. Results: The median time from randomization to angiography was 48 minutes, and the median time difference between the two treatment strategies was 31 minutes. The two coprimary end points did not differ significantly between the prehospital and in-hospital groups. The absence of ST-segment elevation resolution of 70% or greater after PCI (a secondary end point) was reported for 42.5% and 47.5% of the patients, respectively. The rates of major adverse cardiovascular events did not differ significantly between the two study groups. The rates of definite stent thrombosis were lower in the prehospital group than in the in-hospital group (0% vs. 0.8% in the first 24 hours; 0.2% vs. 1.2% at 30 days). Rates of major bleeding events were low and virtually identical in the two groups, regardless of the bleeding definition use

Changing automotive body measurement system paradigms with 3D non-contact measurement systems

Notes: December 5, 2003Full Text: http://www.osat.umich.edu/cmm%5Foptigo.pdfGeneral Motors Corporation, Small Car Divisionhttp://deepblue.lib.umich.edu/bitstream/2027.42/1549/2/98008.0001.001.pd