Six Sigma Course: Robust Tolerance Analysis

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Robust Tolerance Analysis (2 day)

A modern approach to engineering product/process variation

Instructor

Dr. Wayne A. Taylor

Course Description

Design offers the first and best opportunity for reducing variation. This seminar teaches you a practical approach for selecting targets and tolerances for both products and processes in order to improve quality and reduce costs. Many real world examples are worked in class including the design of a pump and the setting of a process window for a heat seal machine. The course provides practical strategies and tools for dealing with real-world complexities.

As part of the course, the VarTran^{^Ò} software package is used to perform all the required calculations. This allows the course to concentrate on the key concepts, strategies and issues.

This course addresses all the classical tools of tolerance analysis including worst-case tolerancing, statistical tolerancing, simulations, and sensitivity analysis. However, it goes beyond the classical tools to cover new tools for selecting optimal targets that optimize performance and reduce variation. This results in robust designs.

What You Will Learn

You will learn to achieve higher quality products and processes while simultaneously reducing costs by learning:

What Six Sigma quality is and how to achieve it up front in design through tolerancing.
How to predict the performance of a product or process early in the design process before investing in equipment, tooling, etc.
The five critical pieces of information driving DFSS
How to use the five critical pieces of information to set specifications limits.
How to perform the two classical approaches to tolerancing, worst-case tolerances and statistical tolerances, along with their pros and cons.
A unified approach to tolerancing that combines these two approaches and solves the dilemma of worst-case versus statistical tolerances.
How to identify the critical tolerances that must be tightened to improve quality and how to identify tolerances that can be widened to reduce costs.
How to design manufacturable products based on machine and supplier capabilities.
How to handle tough nonlinear problems and other complications such as component wear, process cycling, and unstable processes.
How to avoid having to tighten tolerances by designing the product or process to be robust to variation in the components and conditions. This is done by simply clicking a button and asking the software to determine the targets optimizing P_pk, Taguchi loss, percent defective, etc.

Intended Audience

This course is intended for all engineers, scientists, and technical management involved in product or process design. It is also equally applicable to plant engineers involved in process improvement. No special statistical or mathematical background is required.

Course Outline

DAY 1- AM

Optimization & Variation Reduction

The goal is to optimize product/process performance while at the same time reducing variation.

Four types of problems: larger the better, smaller the better, closer to target the better and closer to target function the better.

The cause of variation.

Variation Reduction and Robustness

The three approaches to reducing variation.

Finding the cause of the variation.

Robustness and its importance

Using robustness to improve product reliability

Benefits of reducing variation

Cost reduction opportunities

Variation Transmission Analysis

A procedure for designing high quality low cost products and processes

Case study - Designing a pump

Strategy

Lessons learned

Obtaining and Entering Information

Introduction to VarTran software

Entering data

Viewing the data

Performing Analysis

The 3-step process

Evaluating the initial design

Finding the optimal targets

Selectively tightening tolerances

DAY 1 - PM

Capability Studies (C_p, C_pk, 6s)

Understanding C_p and C_pk

Six sigma quality

Understanding the results

Effects tables

Plots

Optimization, Prediction & Simulation

Methods of optimization

Methods of predicting the variation

Monte Carlo simulations

Design of Experiments

Case study - Heat sealer

Dual response approach to robustness

Using VarTran to perform the dual response approach

VTA Following an Experiment

An alternative approach to robust design using tolerance analysis

Advantages of this approach

Combining the two approaches

DAY 2 - AM

Review of Day 1

Three Approaches to Robustness

Taguchi's inner/outer array approach

Dual response approach

Tolerance analysis approach

Comparison

Tolerance analysis approach is best demonstrated practice

Tolerances

What is the designers intent?

The ACHILLES' HEEL of the design process

Worst-Case Tolerances

Linear case

Nonlinear case

Clear intent

Overly expensive

Statistical Tolerances

Linear case

Nonlinear case

How they lower costs

Difficulties interpreting

Danger of using

DAY 2 - PM

Process Tolerances

A new approach where requirements are specified for the process producing the product

A unified approach to tolerancing that combines both the previous methods

Using process tolerances to combine worst-case tolerances and statistical tolerances in the same analysis. No longer longer are you forced to choose

Deciding what type of tolerance to use

Accurately describing the behavior of a variable

Using process tolerances to ensure product quality while lowering costs

Reliability and Special Applications

Relationship between reliability and variation

Using robustness to achieve high reliability without adding product cost

Putting It All Together

Software Used

VarTran

Prerequisites

None.

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