Guest post by LiveWorx Sponsor Sigmetrix
There is a lot of discussion about Model-Based Definition and Model-Based Enterprise. Most of the industry easily acknowledges the need to move forward with these initiatives. Who doesn’t want to reduce cost, improve product quality and get to market faster! The challenge becomes figuring out how to best unlock this potential.
Every company has a slightly different version of what MBE looks like, but, generally speaking, everyone agrees that a fully defined 3D model that captures design intent for use by downstream analysis, manufacturing, inspection, and field service is at the foundation. This model needs to contain not only 3D geometry but associative PMI and other machine-readable attributes as well.
This comprehensive model acts as a repository for the product requirements that will flow through the product lifecycle. Those requirement definitions must be both human and machine readable to realize the full power of MBE. With this expanded view of how requirements are captured and consumed we must look at whether traditional practices are up to the challenge.
For years companies have relied on +/- dimensions to capture the size and shape of parts along with a definition of the allowable variation, but there is some inherent ambiguity in this definition. Are you locating the axis to a surface, or locating the surfaces to an axis? Most people will assume one or the other based on convention and reasoning, but can we expect a computer to be able to do the same reasoning? The problem we are facing gets compounded when dealing with real variation on the produced part. The idealized flat surfaces that the dimension references are no longer flat. What are you supposed to measure? What is the solution? Using geometric dimensioning and tolerancing (GD&T) can clarify the situation. GD&T (referred to as GPS internationally) is the language for MBD. It was developed to remove ambiguity in dimensioning parts. It’s a standard based language that defines the limit of variation in terms of boundaries, clearly defines what is being measured to specific references, and allows explicit control of all aspects of feature variation (size, location, orientation and form). If properly applied it can be machine readable downstream.
So now that we have established the correct language for MBD, creating a comprehensive machine-readable design should be a breeze, right?? Have you ever tried to learn a second language? It can be difficult to understand and to remember all the grammar rules. GD&T is no different. Millions of dollars are invested each year in training, books, and guides to educate people and refresh the knowledge of GD&T. Despite this retention and understanding is low. Few engineering programs teach GD&T, and even if they did, without regular use the skill set would diminish over time. Some studies have shown that as many as 80% of engineering change orders are the result of improper GD&T.
Not only is the syntax of the language itself difficult to remember, but a lot of work goes into creating all the proper semantic references to the geometry. The workflow to create the references in most CAD systems can be difficult. Complicated parts with many features pose additional challenges. Can you look at the part below and easily see if all the features are properly constrained? Have all the controllable aspects of those feature been controlled? Are there redundant controls? This can be a challenge whether you are fully dimensioning a part or using a minimally dimensioned part approach.
Achieving proper syntax and semantic connections is difficult. Ensuring complete and proper constraint is difficult. What is an engineer or designer to do? Many have turned to software tools to facilitate the application of GD&T. Sigmetrix developed GD&T Advisor which has been a very popular and helpful tool. In fact, it was so game-changing that PTC partnered with Sigmetrix to have this technology embedded within the Creo 4.0 release to help overcome the complexities historically associated with GD&T. It offers guidance for correct syntax and semantics, a streamlined workflow for native annotation creation, visual indication of what is properly constrained, and feedback describing what is not correct or complete. Designers and engineers now have a tool that can help them unlock the potential of MBD.
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 10 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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