What you’ll learn
- Worst-Case approach
- Statistical approach (RSS)
- Six-Sigma approach
- Create the loop for tolerance analysis in 2D
- Estimate the quality level of the assembly
- Estimate the expected Defects Per Million of Opportunities (DPMO)
- Inflation factors for non-normal distributions (Ci)
- Process capablity index (Cp) from manufacturing
- Dynamic shift (k) for loss of performance over time
- Understand trade-offs for tolerance analysis
- Customer requirements (LSL, USL)
Stack up and Tolerance Design is all about quality, or in other words, the allowable parts to be rejected during the process. In escence, this results in an iterative process between the design department, manufacturing and the customer. In this course you will learn the concepts to master plus/minus tolerance stack ups in 2D. At then end, you will become a valuable member for your company because you will be capable to assess assemblies and propose changes to meet critical requirements. Although currently there are several software which run complex tolerance analysis in 3D, in my experience, most of the times you can simplify the problem with a 2D analysis, so as mechanical designer YOU MUST be capable of performing 2D analysis in order to save valuable resources to the company.
First, you will learn the basics: The definition of nominal value, tolerance, standard deviation, normal distribution and the importance of tolerance analysis in mechanical design.
Then. you will learn how to create the sketch (loop) to follow in the calculation of tolerance analysis. Several exercises will be provided so you can practice this process.
Next you will Learn how to perform a linear stack ups with three approaches:
- Worst Case: When no rejections are allowed. This apporach results in the most expensive, but it is used in critical applications.
- Statistical: Some rejections are allowed. The costs are reduced because some defects will always be presented.
- Six-Sigma: Complex considerations such as process distributions, process caapability and loss of performance are taken into account to improve the design at different quality levels.
Finally, for each approach I will provide you five assemblies with different requirements. You will need to apply the concepts to find the suitable design which meet the quality levels and solve the critical clearances. A template in excel will allow you to perform these calculations.
Please note: We will cover ONLY plus/minus tolerances. But the knowledge is also applicable for geometric tolerances.
This course is based in my own experience as designer in the aerospace industry for 10 years. I used this methods everyday to discuss initial changes with customer, find a suitable provider and reduce costs with manufacturing.