In essence, reverse engineering is the process of taking a manufactured product and copying it. The term has gained currency in the last five to ten years, thanks to the new ability to take an existing part and turn it into 3D CAD data.

The reason to use reverse engineering is usually because a product exists in a physical format but not in a 3D CAD format. And we all know the benefits of having a 3D CAD model! For easy-to-model and machined parts, creating a 3D parametric model straight into the CAD system is usually the best approach. For parts with more complex surfaces, however, reverse engineering comes into its own.

The method involves scanning or digitizing the physical part to create 3D points, curves, and surfaces. Because today’s scanners and digitizers are easy to use and very accurate, capturing the information is actually the easy part. There are several hardware options on the market, differentiated primarily by technology used, accuracy, speed, and cost. As is often the case, the faster and more accurate the device, the higher the cost, but be aware that several low-cost choices are available.

Why Action Man?

The Concurrent Design Group has been working with Hasbro Europe on Pro/ENGINEER ® related projects for several years. Hasbro UK manufactures many new Action Man playstations every year—cars, bikes, canoes, moonbuggies and submarines, to name a few. Action Man has to fit on or in all these products, which initially could only be tested at the prototyping stage. After we reverse-engineered the entire doll, however, Action Man can now be tested for fit and function criteria at the CAD product design and development stage.

Methodology

One fundamental issue with reverse engineering is file size. A complex Pro/ENGINEER surface model may be 10MB; a reverse-engineered surface model could be as large as 300MB. For Action Man, we knew the file size for the full doll assembly would become unwieldy with all parts scanned in, so we decided to start with a “skeleton” man.

Using standard Pro/ENGINEER techniques, we created each of Action Man’s 17 parts as simple solid models and assembled the parts using coordinate systems. As such, Action Man was not a true bones-only skeleton, but one with no muscles. The scanned data would then give Action Man the body we all dream of! As the project progressed, each part was assembled as an interchangeable item—from complex part to simple part or vice versa.

Since the Pro/ENGINEER Action Man needed to be manipulated exactly like the doll itself, we had to create a mannequin with moving parts. Each limb and part of limb thus had to be constrained in the available degrees of freedom. We accomplished this using datum coordinate systems throughout (with MDX joints being the next stage of the process). We also programmed standard positions via a family table for standing, sitting, and walking.