Geometric Dimensioning & Tolerancing (GD&T) and Design For Six Sigma (DFSS)

Robert P. Jackson, P.E.

Course Outline

This course is basically intended to address two distinct, but related, areas of engineering design: 1.) DESIGN FOR SIX SIGMA (DFSS) and 2.) GEOMETRIC DIMENSIONING AND TOLERANCING (GD&T).  Both concepts have been viable approaches to design and detailing for some years and both are extremely valuable and useful tools for the practicing engineer.  DFSS is a statistical method of design that can serve as a predictive tool to greatly improve quality control; if used properly and consistently.  GD&T is a well accepted methodology of detailing the characteristics, dimensions and tolerances of a component or assembly of components.  The GD&T methodology is prescribed by ASME / ANSI Standards Y 14.5M-1994 and Y14.5-2009.   This course uses the tenants of 6-σ AND GD&T to fully define a mechanical component, or assembly of components, so that no more than 3.4 defects per one million parts will result when in use.   DFSS and GD&T are usually taught as separate subjects but they certainly complement each other as far as design tools.  It is much more difficult to achieve six sigma (6σ) results without using the DFSS approach.  By using standard linear dimensioning instead of GD&T, huge errors can be made that leave room for doubt when designing tools and dies for fabrication. This will become apparent as we address GD&T.  For this reason, I am structuring the course to include, and integrate, both methodologies.  I would like to state that the treatment of DFSS and GD&T will be somewhat general and not in depth as far as mathematical modeling, which sometimes accompanies courses of this nature.  There are excellent texts available on both subject but, none that I have found integrating both disciplines.  The combination of these two is definitely a logical presentation for “blue-collar,” goal-oriented, working engineers and engineering managers. 

This course includes a multiple choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the completion of this course the student will have accomplished the following:

• Will know the basic differences between Six-Sigma and Design for Six Sigma (DFSS);
• Will understand what is meant by Statistical Tolerancing and how the methodology provides a great benefit to DFSS and GD&T;
• Will understand how GD&T supports effective DFSS methodologies;
• Will understand the overall goals of DFSS and how DFSS it is applied to component and product design; i.e. DMAIC methodology;
• Will understand the role that Quality Functional Deployment (QFD) serves in the DFSS benchmarking process;
• Will understand the role that Failure Mode Effect Analysis (FEMA) plays in the DFSS process;
• Will become aware of what CAD, CAM and simulation software is available to minimize design time and aid lesser time to market;
• Will understand the basic tenants of Geometric Dimensioning & Tolerancing (GD&T );
• Will be able to recognize GD&T geometric  characteristic symbols  and tolerance modifier symbols;
• Will know how to combine DFSS and GD&T methodologies for effective problem solving;
• Will know how to construct a Tolerance Allocation Spreadsheet;
• Will understand the Tolerance Allocation methodology regarding assignment of tolerances and standard deviation;
• Will understand the importance of benchmarking in the “IDENTIFY” phase of DFSS;
• Will be able to read a complex engineering drawing to identify critical design features;
• Will know how to construct a loop or “gap” tolerancing diagrams;
• Will understand all of the  GD&T  Geometric  Symbols and how they apply to drawings;
• Will understand all of the GD&T Tolerance Modifiers and how they apply to feature control frames;
• Will understand the criticality of specifying  datums when dimensioning a drawing; and
• Will understand the importance of Six Sigma and process control.

Intended Audience

This five (5) hour course is intended for people participating in the following professions:

• Engineering Managers
• Mechanical Engineers
• Design Engineers
• Draftspersons
• Quality Engineers
• Quality Control Inspectors
• Manufacturing Engineers
• Machinists
• Anyone who may be required to produce or interpret complex engineering drawings.
• Green, Black or Master Black Belt practitioners
• Reliability Engineers

We are covering material that would be well within their field of expertise.   Both DFSS and GD&T are methodologies used by people in the professions given above.  More and more people in technical professions are relying upon statistical methods to quantify and analyze data.   This course is written around the need for applications supporting manufacturing processes.

Benefit to Attendees

By the end of this course, the student will have gained enough knowledge to do the following:

• Know the difference between “linear dimensioning” and GD&T
• Construct  QFD templates  allowing for the capture of the most desired consumer needs
• Be able to construct a Tolerance Allocation Spreadsheet
• Be able to interpret a Feature Control Frame used when dimensioning relative to GD&T
• Know how to find the USL and LSL from a normal Six Sigma curve
• Know how to interperate a drawing and read the GD&T symbols
• Be able to construct a loop diagram or “gap” diagram describing the tolerances for an assembly of mating parts
• Will know PPM vs Sigma information
• Will know how to correlate Rolled Throughput yield with Six Sigma values
• Will understand “defects per unit” (DPU) and “defects per opportunity” (DPO)
• Will understand the benefits of benchmarking and know how to start the process of benchmarking a component
• Will understand the importance of Six Sigma as a tool for analyzing data gained by observing production processes
• Will know how to “marry” Six Sigma and GD&T to benefit the process of improving a production process

Course Introduction

This course is basically intended to address two distinct, but related, areas of engineering design: 1.) DESIGN FOR SIX SIGMA (DFSS) and 2.) GEOMETRIC DIMENSIONING AND TOLERANCING (GD&T).  Both concepts have been viable approaches to design and detailing for some years and both are extremely valuable and useful tools for the practicing engineer.  DFSS is a statistical method of design that can serve as a predictive tool to greatly improve quality control; if used properly and consistently.  GD&T is a well accepted methodology of detailing the characteristics, dimensions and tolerances of a component or assembly of components.  The GD&T methodology is prescribed by ASME / ANSI Standards Y 14.5M-1994 and Y14.5-2009.   This course uses the tenants of 6-σ AND GD&T to fully define a mechanical component, or assembly of components, so that no more than 3.4 defects per one million parts will result when in use.   DFSS and GD&T are usually taught as separate subjects but they certainly complement each other as far as design tools.  It is much more difficult to achieve six sigma (6σ) results without using the GD&T approach.  By using standard linear dimensioning instead of GD&T, huge errors can be made that leave room for doubt when designing tools and dies for fabrication. This will become apparent as we address GD&T.  For this reason, I am structuring the course to include, and integrate, both methodologies.  I would like to state that the treatment of DFSS and GD&T will be somewhat general and not in depth as far as mathematical modeling, which sometimes accompanies courses of this nature.  There are excellent texts available on both subject but, none that I have found integrating both disciplines.  The combination of these two is definitely a logical presentation for “blue-collar,” goal-oriented, working engineers and engineering managers. 

The course is divided into four distinct divisions; i.e. 1.) DFSS Survey, 2.) GD&T Survey, 3.) Problem solving that shows how DFSS and GD&T interact and compliment each other AND 4.)  Teachable QUIZ.  Please note that I have chosen to construct the Quiz at the end of the course to be a learning experience.  Several of the questions have descriptive information important to understanding the basic tenants of Six Sigma and GD&T. This descriptive information may not be in the body of the text itself. 

I hope to achieve an interest that will provide impetus for engineers and engineering managers to adopt both disciplines for their companies.  I would also state that by using DFSS, GD&T AND the tenants of Reliability Engineering and Reliability Testing, a product  can be designed and manufactured to satisfy the most critical end user;  for either consumer or commercial products.

Course Content

The course content is in a PDF file:

Geometric Dimensioning & Tolerancing (GD&T) and Design For Six Sigma (DFSS)

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Course Summary

This five (5) hour course is presented to those individuals who wish to know more about Geometric Dimensioning and Tolerancing (GD&T ) and how this subject complements Design for Six Sigma (DFSS ).  We will cover the following major topics as we integrate both methodologies:

• Basic overview of Six Sigma approach
• The differences between Six Sigma and DFSS
• The importance of Six Sigma goals including the difference between sigma levels
• The importance of Rolled Throughput Yield
• DFSS tools including the use and importance of FEMA and QFD
• A presentation of several major simulation software packages used in the “DESIGN” phase of DFSS
• A presentation of t he DMADV methodology; i.e. Design, Measure,Analyze,Design,Validate.
• A list of those GD&T standards used in the United States and the standards used globally
• The significant benefits of GD&T usage
• GD&T geometric symbols
• GD&T symbol modifiers
• The importance of the Feature Control Frame and how it is used to specify a dimension or geometric symbol
• GD&T rules for use
• A presentation of Tolerance Allocation relative to component parts
• Examples of how to read a complex engineering when GD&T is used
• How to construct a tolerance allocation spreadsheet
• The importance of “benchmarking” a design
• The meaning of “statistical allocation”
• How to evaluate “gap” or “stackup” when considering an assembly of components.
• Examples of how DFSS and GD&T are “married” when working a design project

This course is written with practicality in mind and in the hopes that the student will consider each discipline with intent to learn more.   Both GD&T and DFSS complement each other, producing as a result, zero ambiguity relative to engineer designs. 

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

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DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.

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