Case Study: Precise Reverse Engineering

Our client

Johnson&Johnson is a medical research company with more than 130-year heritage. J&J is famous for pushing the limits of modern medical sciences and developing applied methods that help people around the globe to fight various evolving diseases and health conditions.

 

Task

WaveCrest General View

WaveCrest CAD Model

To develop the accurate representation of the new generation of WaveCrest devices for further research purposes. The main difficulty is that the product design itself is not very CAD friendly. Some parts of these devices are produced from high precision laser-cut nitinol parts. The desired shape is achieved by twisting and bending the original patterns. So CAD / CAM Services had to 3D scan the assembled unit and then recreate it with precise professional 3D CAD modeling.

 

Solution

This could be just another reverse-engineer-from-3D-scan task, but this time things are more complicated starting from the scanning stage. As WaveCrest is designed to work inside the human body, it is very small, fragile and can be easily deformed. 

It also comes in various sizes, each with a different pattern which makes it necessary to recreate all the models separately.

Due to its size, it was impossible to get highly accurate scans keeping original shape, as all scanned objects need to be fixed during the 3D scanning process.

When high precision meshes were obtained (5 manufactured samples for each device size) with cutting edge CT 3D scanning technology with .0008” accuracy it was time to create 3D models. CT is the most precise 3D scanning technology available on the market. CT scans are much more accurate than the ones obtained with handheld 3D scanners.

To achieve the precise modeling goal our specialists had to perform thorough preparations. All incoming meshes were accurately calibrated. Due to the circular patterned geometry of the design, it was crucial to align it precisely with the internal CAD software coordinate system. 

assembly deviation

Deviation Analysis of the Whole Assembly

Even though it was one of the most precise scanning methods, it was inevitable that some artifacts occurred on such small shapes.

Circular pattern allowed our 3D CAD specialists to concentrate on finding the best parts of typical elements throughout the incoming meshes. All the best parts were assembled together which resulted in .001” precision on the selected ideal segments.

Constant quality control from J&J side and frequent meetings concerning the initial goal of these reverse-engineered models allowed us to produce all required 3D assemblies exceeding our customer’s expectations.

Part Deviation Analysis

Each Small Part was modeled separately

You can’t be too precise when working with this kind of complex geometries, so to obtain the most accurate model it was decided to try out two more ways of obtaining the geometry.

In order to make the most accurate representation of the CT scans all the five meshes for each size were averaged and used to create another set of 3D models.

Later on, to be completely sure and precise, we created another set of models from the CT scans provided by the client.

Constant meetings were held throughout the project in order to correct the overall way of reverse engineering so that we could understand the most and the least important elements of the model in order to provide the best experience possible.

 

Conclusion

 

Constant meetings and clear goal descriptions can make it possible to work fast even in non-standard cases. 15 scans resulted in 3 sets of models. Each set of 3 models was produced with .002” accuracy and took us about a week, scanning and meshing time excluded. 

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