Almost any reasonable computer-aided design (CAD) structure can get a development team through its first prototype. However, the real test comes later.
Requirements change. Suppliers introduce new components. Interfaces move. Product variants appear. Meanwhile, more engineers begin working on the design. As a result, a manageable collection of parts and assemblies can become increasingly difficult to modify without affecting something unexpected.
As we discussed in The Most Expensive Decision Happens Before Prototype 1, some of the most consequential development decisions occur before engineers have much hardware to evaluate. Unplanned CAD architecture can turn those early decisions into costly complications as development progresses.
Define the architecture before the model defines it
A CAD architectural strategy establishes how the team will represent, control, change, and manage the product design.
How will engineers divide the product into assemblies? Where will they define critical interfaces? Which geometry can other components reference? Which dimensions carry design authority? How will the team manage variants and shared reference geometry?
For many programs, a short CAD architecture plan may be enough. For example, the plan might include an assembly map, reference strategy, interface ownership, configuration approach, key modeling rules, and assigned responsibilities.
By documenting these decisions early, the team can avoid creating dependencies that become increasingly expensive to change.
Control how change propagates
Consider a pump mounted to a chassis inside an enclosure. During early development, an engineer might locate an enclosure connector using an edge from the pump housing simply because the geometry is readily available.
This approach works until the pump supplier changes the housing.
If brackets, tubing, and enclosure features depend on that geometry, a small supplier change can trigger broken references and unexpected downstream changes. Instead, a more scalable architecture establishes controlled mounting planes and interface geometry. Consequently, the supplier can modify details within its boundary without unnecessarily disturbing the rest of the product.
Controlled interfaces also establish dimensional authority. As discussed in GD&T as a Communication System, communicating design intent requires clear definitions of critical features, their relationships, and allowable variation. A sound CAD architecture provides the foundation for that communication.
One useful way to evaluate an architecture is its radius of change: when one interface changes, how much unrelated geometry must engineers update or repair?
Good architecture cannot eliminate change. However, it can contain its consequences.
Put flexibility where it creates value
Parametric modeling provides powerful tools for creating relationships. Nevertheless, more relationships do not automatically produce a more scalable design.
For example, consider a product offered in three enclosure lengths. A controlled parameter that drives the enclosure, rails, and mounting locations may help engineers manage those configurations efficiently.
However, connecting dozens of unrelated components to the same master model can create a tightly coupled system. Consequently, a simple modification may affect features throughout the assembly.
The objective is intentional connectivity: engineers should create relationships that represent durable engineering intent.
Make sure the CAD environment supports the strategy
CAD architecture also depends on the software and data-management systems that support it.
CAD platforms differ in their support for top-down design, master or skeleton models, external references, product configurations, and concurrent development. Furthermore, product data management (PDM) and product lifecycle management (PLM) systems influence how teams control, share, release, and revise models.
Even an elegant architecture can become difficult to maintain when it relies on methods the selected systems handle poorly. Therefore, the architecture should reflect both the product’s requirements and the practical capabilities of the CAD environment.
Give the architecture an owner
Teams should define CAD architecture early, document it at an appropriate level, and revisit it as the program evolves.
On complex programs, a chief engineer, system architect, or designated CAD/design lead should champion the architecture and maintain consistency as the team grows.
However, architectural ownership does not require someone to prescribe every modeling decision. Instead, it ensures engineers understand where design authority resides, how to create dependencies, and how the model should accommodate change.
Because if nobody owns the CAD architecture, the feature tree eventually will.
Is Your CAD Architecture Built to Scale?
A65 Consulting offers a free CAD architecture review for medical device development teams. We evaluate assembly structure, critical interfaces, reference and dependency strategies, configuration management, and architectural ownership to identify where early CAD decisions may create unnecessary complexity as the product and development team evolve.
If your team is establishing its CAD architecture, preparing for prototypes, adding product variants, or managing increasing design complexity, contact A65 Consulting to schedule a complimentary CAD architecture review.
When leadership transitions, rapid growth, or an urgent program stretch your engineering organization, A65 Consulting provides experienced fractional engineering leadership to set direction and drive execution.
Email: sdonnigan@a65consulting.com
Or schedule your review online
References
- Pahl, G., Beitz, W., Feldhusen, J., & Grote, K.-H. Engineering Design: A Systematic Approach. 3rd ed. Springer, 2007.
- Ulrich, K. T., Eppinger, S. D., & Yang, M. C. Product Design and Development. 7th ed. McGraw Hill, 2020.
- Whitney, D. E. Mechanical Assemblies: Their Design, Manufacture, and Role in Product Development. Oxford University Press, 2004.
- PTC. Top-Down Design and Skeleton Models. Creo Parametric documentation.
- Siemens Digital Industries Software. Product Configurator and Reuse in NX. Siemens NX documentation.
- Dassault Systèmes. SOLIDWORKS PDM: Managing Product Data and Design Changes. SOLIDWORKS technical documentation.