车身测量系统能力(英文)(pdf 30页)

Preface …………  . . . . vi
Executive Summary ………… . . . . . . . . 1
1.0 Introduction ………… .. . . 3
2.0 Body Measurement Systems …………  . . . . . . 4
2.1 Measurement System Applications ………… . . . 4
2.2 Part Locating System (GD&T) ………… . . . . . . . 5
3.0 Gage Capability …………………… . . 7
3.1 Gage Capability for Checking Fixture Data . . . . .. . . 7
3.2 Gage Capability for CMM Data ………… . . . . . . 9
4.0 Measurement System Analysis ………… . . . . . . . . . . 11
4.1 Gage Error and Type of Part ………… . . . . . . . . 11
4.2 Gage Error and Dimensional Characteristics . . . .. . 11
4.3 Effect of Dimensioning and Part Locating System (GD&T) on Accuracy . . . . . . 14
4.3.1 Case Study I: Effect of Clamping Sequence . . . .. . 15
4.3.2 Case Study II: Effect of Additional Clamping Locators . . . . . . . . . . . 17
4.4 Gage Variability and Part-to-Part Variation . . . . . . . . 19
5.0 The Effect of the Measurement System on Dimensional Evaluation Processes . . . 21
5.1 Gage Capability and Tolerances ………… . . . . . 21
5.2 Constrained versus Over constrained Clamping Systems . . .. . . . 21
6.0 Conclusions ………… . . . . 22
Figure 1. Measurement Systems…………………… . . . . . . . . .4
Figure 2. Body Coordinate System…………………… . . . . . . .5
Figure 3. The 3-2-1 Locating Scheme…………………… . . . . .6
Figure 4. Number of Locator Clamps at Company C versus Company E . . . . . . . . . . . . . . . .6
Figure 5. Histogram of Gage Standard Deviation for Checking Fixtures . . . . . . . . . . .7
Figure 6. Distribution of % Gage R&R (Goal < 30%)………… . . . . . . . . . . . . .8
Figure 7. Percent of Gage Variation Explained by Repeatability Error…………8
Figure 8. Static versus Dynamic CMM Gage Repeatability Error………… . . . .9
Figure 9. Distribution of Gage Error for Small Simple and Large Complex Parts . . . . . . . . . . .11
Figure 10. Correlation of Gage Error for Right and Left Coordinated Dimensions . . . . . . . . . . .12
Figure 11. Histogram of CMM Gage Variation for a One-Piece Body Side Outer Panel . . . . . . .12
Figure 12. High Gage Error vs. Datum Scheme………… . . . . . . . . . .13
Figure 13. Gage Error by Part Area…………………… . . . . . . . .14
Figure 14. Dimensional Measurements for an Inner Quarter Panel………… . . .15
Figure 15. Differences in Mean and Variation for Alternate Clamping Sequence . . . . . . . . .16
Figure 16. Effect of Clamping Sequence on Dimension #4………… . . . . . . . . .16
Figure 17. Body Side Conformance and Clamping Strategies………… . . . . . . .17
Figure 18. Contribution of Gage Variation to Part-to-Part Variation………… . . . .20
Table 1. Gage Variation by Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Table 2. CMM vs. Checking Fixture Gage Repeatability for One-Piece Body Sides . . . . . . . .10
Table 3. Mean and Variation Conformance by Clamping Approach . . . . . . . . . . . . . . .18
Table 4. Effect of Measurement Instrument on Mean Values: CMM vs. Feeler Gages . . . . . . .18
Table 5. Effect of Measurement Instrument on Variation: CMM vs. Feeler Gage Data . . . . . . .18
Table 6. Inherent Gage Error and Minimum Tolerance Requirements . . . . . . . . . . . . . .21

This report is one of a series published by the
Auto/Steel Partnership Body Systems Analysis
Project Team on stamping and assembly variation,
body measurement systems and process validation.
These reports provide a summary of the project
research and are not intended to be all inclusive
of the research effort. Numerous seminars
and workshops have been given to individual
automotive manufacturers throughout the project
to aid in implementation and provide direct technical
support. Proprietary observations and implementation
details are omitted from the reports.
This automotive body development report,
“Automotive Body Measurement System
Capability,” updates ongoing research activities
by the Body Systems Analysis Project Team and
the Manufacturing Systems staff at The University
of Michigan’s Office for the Study of Automotive
Transportation. The purpose of this report is to
quantify the capability of various body measurement
systems and to examine the impact of the
measurement system on dimensional evaluation……

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