Guest post from LiveWorx Sponsor Sigmetrix, James Stoddard, Executive Vice President, Product Development

Engineers and Designers are tasked with creating the specifications that will be used to create new products.  These new products may be based on existing products or may be a totally new concept.  Either way this new design has never been built.  To ensure success the engineer will capture every detail of the product within a CAD system.  They then perform various analyses to guarantee the structural integrity, the kinematic function, heat dissipation, etc.  These analyses are often done with a very high level of precision to gain understanding of whether the design will meet the requirements of the product. 

Sigmetrix Bridge Analysis Types P1

Even with all this engineering analysis the initial design rarely meets the desired requirements.  This has led companies to include prototype builds into the design process.  Some companies have as many as five prototype cycles before the design is finalized and ready for production.  With the ever-increasing globalization of manufacturing and the increased use of suppliers, these prototype cycles can lead to significant delays and cost increases.  With all these analysis and prototypes cycles there are still failures in the field.

What is missing? Why are we not able to better model reality?  Even though these analyses are based on sound engineering understanding and are performed at a very high level of precision they are dependent on the definition of the product within the CAD system which is modeled at perfect size and shape. When that design is produced, however, manufacturing variation is introduced.  The parts of the design are no longer perfect size and shape.  These variations, usually not considered in the detailed analyses that predicted a working product, can lead to failures in manufacturing or even worse in the field.

Sigmetrix Bridge Design Vs Produced

Engineers understand that manufacturing variation exists, but often they try to account for it by varying the parameters of their analysis or by applying a safety factor when comparing the computed results to the needed requirements.  This may account for some of the variation, but it is hard to predict if it is too little, falling short of the desired quality, or too much, introducing unwanted cost.  There is a better way. Variation or tolerance analysis is the missing analysis that accounts for the introduction of manufacturing variation and computes how that variation will propagate through the product to affect key product characteristics.

Variation analysis has value throughout the design and manufacturing process.  Understanding early on how variation might propagate through a design can lead to a design decisions that will minimize the impact of manufacturing variation.  A completed variation analysis can help eliminate costly and time-consuming prototype cycles.  In one case using variation analysis software in the design stage helped a company to limit the amount of rework and 2nd round prototype tooling. Reducing a physical prototype step for them saved as much as $10,000 and up to 2 weeks of time on a single design.  Another company was able to reduce the number of prototype cycles from five to one.  In addition, variation analysis can be used to run a root cause analysis after a problem has been found to identify the most significant contributors to the problem and help identify the proper corrective action minimizing impact on other key characteristics.

Sigmetrix Bridge Cetol P5

Variation analysis is the missing bridge between design and reality.  The understanding of variation impact together with the other analyses allows the designer to see a complete picture of what can be expected once the design is produced.

About James Stoddard 
Executive Vice President, Product Development at Sigmetrix

James is the top technologist for the creation of CETOL 6σ Technologies, advanced constraint systems, architecture and CAD integrations developed over 25 years of professional research going back to his work at Brigham Young University working with Dr. Ken Chase, founder of ADCATS, the Association for Development of Computer Automated Tolerance Systems. James is recognized by the top PLM companies and universities as the leading expert in advanced constraint technologies setting the benchmark for precise solutions necessary for addressing the next generation needs of tolerance optimization systems.

Sigmetrix is a provider of comprehensive, easy-to-use software solutions that help users achieve robust designs through tolerance analysis and the correct application of GD&T. With 25+ years of R&D and consulting experience, they are global experts in GD&T and mechanical variation. Products include CETOL 6σ, a fully-integrated 3D tolerance analysis solution enable designers and engineers to understand the impact of part and assembly variation on the fit and performance of their products, EZtol, a 1D analysis tool offering numerous advantages over spreadsheet-based analyses, and GD&T Advisor, an interactive tool that provides expert guidance on the correct application of GD&T to the models per relevant ASME and ISO standards. Sigmetrix also offers world-class GD&T and MBD/MBE training classes and a professional services team that that has years of experience in tolerance analysis and GD&T definition. 

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