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Moving Forward with Reverse Engineering

Reverse Engineering Process | FEA and CFD Consulting
April 8, 2016 By: Patrick Cunningham

Picture yourself in a Dan Brown novel. A mysterious person steps into your office and hands you an odd looking widget covered with dust. He tells you that this item was discovered recently in a pyramid somewhere and he believes it holds ancient engineering secrets. He needs you to reverse engineer it and save the world. Typical day at the office, right?

I’ve found myself in this situation many times, though usually without the drama and intrigue. Whether it was an evaluation of a competitor’s product, or the brain child of a long retired designer, I needed to reverse engineer it so I could understand it and improve on it. 

In the past, my process went something like this:

1)  Get a ruler and some calipers and start measuring.

2)  Create a geometry model in my CAD tool based on those measurements.

3)  Import the geometry into an FEA or CFD analysis tool and evaluate it. 

4)  Identify aspects of the design I could improve on.

5)  Modify the geometry and re-evaluate until I was happy with the new design.

This approach could be very time consuming in the geometry creation stage, as well as in the modification stage. The geometry could be defined parametrically, provided I had an idea of what aspects of the design I would be studying. Without that knowledge, the design iterations had to be updated manually. There was also the issue of measuring things I could not see or reach. In those situations, I had to make my best guess and hope that my analysis was close enough to the original design to be accurate.

Recently, scanning technology has become better and more readily available. Scanned geometry data is typically in STL form where the topology is made up of triangular faceted faces. The STL data can be converted to a solid model using CAD tools, but still requires a significant amount of cleanup before it can be used to create a finite element model. Changing the geometry is also difficult with most CAD tools because the STL model is imported and there is no parametric feature history.  With scan data, we have a more accurate way to reproduce the geometry but still no easy way to change it and perform design studies.

More recently, direct modeling CAD programs with reverse engineering tools have been introduced. Check out CAE Associates’ ANSYS SpaceClaim demonstration for more information. These tools are really good at extracting topology from complex STL files to create accurate and….wait for it….parametric solid models!  Direct modeling tools allow you to morph solid model geometry with ease. The method is interactive so you can modify virtually any aspect of the model with the click of the mouse. You control the design intent based on the design modifications you want to explore. The geometry changes can be controlled parametrically so that you can automate your design studies and fully evaluate the design sensitivities. 

Consider the example shown in the figure above. With a direct modeling tool, STL data from a scan can be used as the baseline to create a solid model. That solid model can be used to create a finite element or CFD model where we can evaluate the design. The analysis of the original gives us an idea of what characteristics of the design need to change to improve the performance. At this point, a direct modeler again comes to the rescue by allowing us to easily modify those characteristics. We then plug the modified design into the finite element solver in order to evaluate the design change.  This can be accomplished as a manual design study or automated by taking advantage of the parametric definition of the design modifications in the direct modeler. 

Is anyone out looking for ways to reverse engineer?  The tools you need are out there!