The process of reverse engineering, or back engineering, is easy to grasp when framed by what science fiction tells us about cloning. From a digital copy or 3D data scan, the equivalent of DNA, data is synthesized to create an exact replica of an existing form or an improved version of the original.
For a local retailer’s new marketing campaign in Cincinnati, Ohio, Exact Metrology recently used reverse engineering on a small scale to demonstrate how the process can bring 3D data to life. The result is the skull plant holder (at right), created using Geomagic DesignX software and NURBS (Non-Uniform Rational B-spline).
“Reverse Engineering meets a fork in the road the instant the 3D data set has been acquired,” explains Greg Groth, division manager at Exact Metrology, the options being to design with intent or as-is.
“Design Intent is the process of reverse engineering the part with corrections built in to offset any manufacturing anomalies. If a hole in a part measures .495”, logic sets in and that feature is corrected to .500”. This sets the end result up for a traditional manufacturing process,” Groth says. “As-Is, is exactly that. As it is, regardless of the physical parts flaws or manufacturing outcome, an exact copy is desired. This, for example, would ensure any mating parts would exactly match.”
Geomagic Design X’s 3D software creates digital models of physical objects for industries such as archaeology, aerospace, medical and dental, tooling, foundry and sculpture and arts. For parametric modeling, Geomagic Design X performs a surface analysis. Afterwards, NURBS is inspected with a color map against the scanned data of Geomagic. Lastly, .stl files are rendered in Keyshot 3D. For the resulting skull, the process took two days.
The skull was scanned with a Romer Arm Laser scanner natively into Geomagic Design X (point cloud). The 3D data was processed into a mesh, then edited to fix any small anomalies and align it to a coordinate system. Once the 3D data was prepped, a NURBS surface was applied to the mesh and the built-in analysis tools were used to highlight and areas to be corrected. The curve network was corrected, and the final surfaces were applied, yielding the result you see today.
“Organic surfaces, such as the skull prove challenging to start from scratch with traditional CAD,” says Groth. “One would never successfully duplicate the intended design of a sculpture with traditional CAD data. 3D scanning it gets exact representation of the surface geometry in digital form. Those can be quickly converted to simplified, but extremely accurate, surface data with Design X.”