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Dimensioning and Tolerancing Handbook Episode 2 Part 6

Tham khảo tài liệu 'dimensioning and tolerancing handbook episode 2 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 11 Predicting Assembly Quality Six Sigma Methodologies to Optimize Tolerances Dale Van Wyk Raytheon Systems Company McKinney Texas Mr. Van Wyk has more than 14 years of experience with mechanical tolerance analysis and mechanical design at Texas Instruments Defense Group which became part of Raytheon Systems Company. In addition to direct design work he has developed courses for mechanical tolerancing and application of statistical principles to systems design. He has also participated in development of a U.S. Air Force training class teaching techniques to use statistics in creating affordable products. He has written several papers and delivered numerous presentations about the use of statistical techniques for mechanical tolerancing. Mr. Van Wyk has a BSME from Iowa State University and a MSME from Southern Methodist University. 11.1 Introduction We introduced the traditional approaches to tolerance analysis in Chapter 9. At that time we noted several assumptions and limitations that perhaps not obvious to you are particularly important in the root sum of squares and modified root sum of squares techniques. These assumptions and limitations introduce some risk that defects will occur during the assembly process. The problem There is no way to understand the magnitude of this risk or to estimate the number of defects that will occur. For example if you change a tolerance from .010 to .005 the RSS Model would assume that a different process with a higher precision would be used to manufacture it. This is not necessarily true. 11.2 What Is Tolerance Allocation In this chapter we will introduce and demonstrate methods of tolerance allocation. Fig. 11-1 shows how tolerance allocation differs from tolerance analysis. Tolerance analysis is a process where we assign 11-1 11-2 Chapter Eleven tolerances to each component and determine how well we meet a goal or requirement. If we don t meet the goal we reassign or resize the tolerances until the goal is met. It is