Multi-Physics and Metrology May Reduce or Eliminate Need for Physical Prototyping
The ability to reduce the need for physical prototypes is revolutionizing product development across various industries. As advances in computing power have paved the way for more accurate simulations of engineering processes and higher fidelity representations of as-built components, it is now possible to improve designs and optimize manufacturing processes in the virtual realm -- saving time and materials and improving final product quality.
While OEMs and their suppliers face continuous pressure to reduce product development costs and shorten timelines, modern assemblies are increasingly complex. Wherever flush fits and dimensional accuracy in production or assembly are critical, advances in digital twin technologies paired with computer-aided engineering (CAE) software tools are accelerating the innovation and product development cycle.
Conforming virtual prototypes replace expensive physical build prototypes.
As the individual sub-disciplines have been around for a long time, the practitioners are typically from either metrology/QA or from the process engineering side, which traditionally uses computer-aided engineering-based tools. Recent tech advances have enabled those disciplines to be taken to the next level and combined in digital twin workflow solutions that address long-standing market needs.
For example, in aerospace, digital twins are being used to virtually test aircraft components, analyzing aerodynamic properties and structural integrity without physical prototypes. At the other end of the spectrum, consumer electronics giants are also using digital twins to adapt to market trends more quickly as they develop new products without needing to create multiple physical prototypes.
The Challenges of the Traditional Metalworking Approach
Whether in automotive, rail or aerospace, the traditional methodology was to fabricate each individual component as close as possible to nominal. Various stampings, castings or extrusions would then be joined into sub-assemblies using spot welding or other joining techniques -- again attempting to hold nominal. This process would repeat with sub-assemblies being married together, to create the completed assembly.
Status quo complex physical check fixture
The challenge however is that each as-stamped component will be a bit out of nominal. Yet conformance of each individual component does not actually guarantee that the assembly will also meet the specification. Each step in the assembly process contributes further dimensional variation and divergence evolves from nominal so that root causes become more and more difficult to identify.
While this effect has long been known, the complexity of the problem was challenging computationally. Engineers still rely on intuition, experience and trial and error to achieve their desired outcomes, making prototyping and testing of the assembly process one of the most costly and time-consuming stages of new product development.
In recent years, software advances have made it possible to simulate manufacturing processes with the required speed and accuracy necessary for practical and efficient workflows. It is now possible to create a digital twin of the manufacturing process that leverages metrology data to morph CAD nominal designs and then apply the effects of gravity, clamping, and assembly in multi-physics process simulations. Onerous parts of the workflow such as meshing and process modeling are now relatively easy to apply. Using such solutions, OEMs and their suppliers can save significant costs while cutting months from product launch timelines.
Comparison of nominal CAD with physical scan data
For example, Hexagon's Smart Assembly Shop (SAS) is a solution built using expertise in both high-fidelity computer-aided engineering (CAE) and metrology. Thus, it enables engineering teams to accurately evaluate the aggregate effects of the manufacturing process and take steps to mitigate issues before the first tool is cut or after non-conformance is observed.
To significantly reduce cost and time in the product development and launch process, engineers must minimize the number of part-specific physical prototypes and iterations required to achieve dimensional conformance of the final assembly. They also want to reduce the quantity and complexity of fixturing. These market needs are addressed with new Virtual Fixture and Virtual Assembly applications.
Virtual Fixture Workflows
During the traditional prototyping or production process engineers load parts or assemblies into a check fixture. After positioning the part or assembly, usually using locating pins and clamps, the engineer uses various analog or digital tools to check dimensional conformance. The more components are included in the assembly, the more elaborate these fixtures become. In general, check fixtures are large, expensive, take time to build, and are costly to handle.
Using a Virtual Fixture -- a virtual version of the physical counterpart -- one can reduce the time and cost required to perform dimensional checks. Components do not need to be transported to the check fixture's physical location and the quantity of physical check fixtures can be reduced or eliminated -- minimizing the cost to build and store over time.
Virtual Fixture Workflow
A Virtual Fixture workflow typically starts with the scanning of physical parts. Using scan data alone to generate non-nominal geometries does not work well. Instead, it is much better to use the scan to morph the original CAD model to obtain a clean non-nominal representation of the part geometry. Next, manufacturers need to take into account the effect of gravity and clamping, both of which lead to part deformation.
Hexagon's technology accurately represents physical realities digitally, can account for these components and parameters, and then remove them so the part naturally settles into equilibrium. It is then re-oriented into the virtual check-fixture or, in the case of automotive assemblies, "car-body" orientation, and the effect of gravity in this orientation is applied.
The next step is to fit the digital part up onto the Virtual Fixture and clamp it using the same locating schema or Reference Point System (RPS) as would be used in the physical process. When multiple components are fit-up on the same Virtual Check Fixture, engineers can accurately evaluate the absolute positions of key features, check feature alignments or approve the flush and gap outcomes up to full body-in-white assemblies.
Virtual Assembly Workflows
Only when a solution is able to take direct inputs from dimensionally non-nominal components, and accurately simulate the multi-physics of clamping, welding, and joining processes would it be technically feasible and robust to create a Virtual Assembly workflow aiming at reducing or eliminating physical prototypes. Hexagon's virtual assembly solution uses advanced multi-physics to accurately handle non-linear behaviors and realistically predict physical contact and interactions between materials.
Virtual Assembly Workflow
Furthermore, within the workflow, engineers can evaluate each stage of the assembly process just as they would during physical production. Engineers can visualize the process and zoom in on specific locations and points in time to understand the key aspects of the process that have the greatest impact on the assembly process.
The goal is to support manufacturers who want to 'shift left', i.e. test and optimize designs and manage quality earlier in the product development process, because this allows them to reduce their investments in prototyping and create more robust processes. This is central to the zero-prototyping movement, which is about reducing or even eliminating the need for physical prototypes in the product development process.
Is a zero-prototyping future a realistic vision? In computer-aided engineering, the saying goes: all models are wrong, but some are useful.
In manufacturing, there are many sources of error -- materials, process, tool setup, tooling wear, even changes to the temperature of the tooling throughout the shift. This means eliminating prototypes all together is a very ambitious goal.
Physical scan of a part with a simple, flexible fixture
However, with virtual assembly solutions, manufacturers can already start to significantly cut lead time and reduce physical prototype costs from the product development process. Moreover, it allows engineers to identify areas for design or process improvements early, before it is too late or too expensive to change.
Where to Begin and What to Look For
Companies investing heavily in physical tryouts, prototyping, or testing can gain significant advantages from virtual prototyping solutions. In particular, dimensional/quality engineers and tool designers can benefit from the new breed of virtual check fixture and virtual assembly solutions.
Ideally engineers desire solutions that offer a strong combination of high-fidelity computer-aided engineering features, advanced metrology and an accessible modeling experience. A scalable solution will interface with any existing metrology hardware and software, like laser scanners, portable measuring arms, laser trackers or CMMs. Most important is that solutions deliver flexible and intuitive workflows and accurate process simulation in a cohesive, purpose-built solution from a company with a strong track record and an inspiring vision for the future.
[Authors: Jeff Robertson, Director Global Business Enablement for Virtual Manufacturing Solutions and Dr Ingo Hahn, Product Manager for Virtual Assembly and Virtual Fixture Solutions at Hexagon Manufacturing Intelligence]
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