What Is Top-Down Design and Why You Should Already Be Using It

Top-down design is a methodology used in CAD to simplify the development of products with complex interdependencies and relationships between components.

Take an electric sports car, for example. As a machine, it needs to be functional and practical. The silhouette of the car is smooth and streamlined to lower drag and conserve battery power.

Beneath that exterior is the battery, along with a mess of wiring, computer chips, sensors, screens, and countless other parts.

How Top-Down Design Works

The first work is typically conceptual, concentrating on the overall shape and function of the car. Then various teams can work on details and motion, adding the gears and gadgets that give it power and allow for driver controls.

They can add a rudimentary drivetrain and other interior structural supports while others work on the headlights and fenders. Others work on the outer skin to ensure the panels all match up properly, while still others add mechanisms and other interior components that sit beneath them and attach to them.

Top-down design isn’t a literal definition of the method. It merely describes the process of designing from a basic sketch—that sits at the top of the model tree—and then adding more complexity. Your sketch can include whatever base components are necessary to communicate design intent and provide a platform for additional geometry.

The best part is that top-down design methodology can be applied to nearly any complex machine including large-format printers, MRI and other medical scanners, small appliances like hair trimmers, and more.

Save Time with Skeletons

That first basic sketch is known as a skeleton. It’s the central object to capture design intent, along with tracking references and interdependencies within the design. Skeletons can also have some early-stage motion, or kinetic features.

Top-down design gives you benefits in three distinct areas.

• The skeleton stores the important geometric design information, while dimensions and calculations are stored in engineering notebooks like PTC Mathcad.
• The data is shared to all the individual components, and their features, throughout the design.
• Relationships between all the components and features are also managed automatically.

Ultimately, what this amounts to is a lot of time and money savings. Without top-down design, a small change to any part of a model becomes a big job, because that change may affect dozens or hundreds of other components in the design. With top-down design, the data is propagated from the skeleton to all design components. Making small or large changes almost anywhere in the design is easier because it will be applied automatically to affected components. If the change affects calculations that are stored in the accompanying PTC Mathcad notebook, those will be updated, too.

See What It’s All About

Arnaud van de Veerdonk, PTC Creo Product Manager, went through top-down design in more detail, with visual examples, as part of a recent online skills-building webcast, “Tips from the Creo Pros.” Van de Veerdonk lays out the specifics of capturing and communicating design intent, managing the interdependencies in components, and how it affects validation and evolving content.

If you couldn’t attend the conference, you can still “Level Up Your Productivity” with the free replay at the link below. Sign in and select Top-Down Design & Design Exploration.

Product development is always evolving, so make sure you’re keeping up with the latest tools and techniques. Click the banner below to check out the webcast today!