Reverse engineering is a procedure for creating an accurate 3D model of an object. In the reverse engineering process, raw 3D scans are stitched, processed, and then transformed into a three-dimensional model. Such a model can be printed on a 3D printer or used for further design.

Reverse engineering is used in a wide variety of industries, from jewelry to large-scale projects in machinery and shipbuilding. This method can be used in the process of developing expensive and high-precision parts of a wide variety of mechanisms. However, reverse engineering is also used when working with organics, for example, for prosthetics.

We continue the series of articles "Reverse engineering for beginners". This time we will talk about the reverse engineering of organic objects in Autodesk Fusion 360.

Fusion 360 is a professional cloud-based CAD/CAE/CAM platform for industrial design and engineering engineering. It is well suited for combining all project development processes. Many hardware startups and companies in the fields of 3D scanning and 3D printing work with it.

The Fusion 360 platform allows

• you to import 3D scans in STL and OBJ formats and refine them.;
• Prepare models for 3D printing, automatically create supports for overhanging surfaces, and view the product structure.;
• Use the built-in CAM system to calculate the best milling paths for manufacturing machine parts.;
• pre-assemble parts and see how the movable joints will behave, and much, much more.

But let’s focus on the functionality for reverse engineering. In this article, we explain in detail how:

• create a surface and align its edges;
• drag the vertices of the surface to the grid points;
• complement the surface and stretch it according to the shape of the grid;
• correct errors and refine the construction of the surface;
• use the result to design a new object.

We illustrate each stage of the work with screenshots.

We chose the human foot as the object for reverse engineering. This may seem like an arbitrary choice, but 3D foot scanning has many real-world applications. Such 3D scans are needed to create prosthetics according to individual patterns, for medical research and diagnostics.

In addition, 3D scanners are used in shoe design. That’s exactly what we’re going to do now. First, we will create a 3D model based on our scan, and then use the result to design the perfect insole that will exactly repeat the smallest curves of the foot. So, let’s launch Fusion 360.

1. To create a 3D scan model, use the T-Spline tools (Create Form, SCULPT menu):

2. Use the available Quadball primitive. Let's choose a plane and determine its center:

3. Determine its approximate size and set the number of control elements using the slider:

4. Adjust its position relative to the grid:

5. Hide the grid and remove unnecessary elements:

6. Make the source data transparent to better see the constructed surface.:

7. Use the FLATTEN tool to align the edges of the surface.:

8. The EDIT FORM tool will help you change the shape of the surface to bring it closer to the shape of the source data.:

9. This approximation is needed to make the PULL command work better. It attracts the vertices of the surface to the nearest grid points.:

10. Now, using the EDIT FORM, we will extend the edges of the surface to form new rows of control vertices.:

11. Use PULL to pull new points to the grid.:

12. Use FACE to complement the surface (grid binding must be enabled):

13. The surface display will only change during the operation of this tool.:

14. Pull out the surface by selecting the desired edges:

15. Use the FACE again to finish the section and get an edge for stretching:

16. We will pull out the resulting edge, scale and align it.:

17. In the same way, we "tighten" the surface of the remaining part of the grid. We use the FILL HOLE to close the end face:

18. Apply the REPAIR BODY function to automatically fix T-Spline errors.:

19. We use PULL to refine the constructions:

20. Drag the selected faces to the end of the grid:

21. To get an additional control, add a new edge:

22. Using the edge to refine the surface:

23. We will remove the folds by removing the control elements:

24. The surface is ready. Now we use it to make a blank for the insole.:

25. Use OFFSET to get a new surface at a distance of 5 mm from the built one.:

26. Let's make two sketches in parallel planes to build a secant surface on them.:

27. We use the LOFT method to build this surface.:

28. Using BOUNDARY FILL, we transform a space enclosed by surfaces into a body.:

29. To see it, we'll hide the surfaces.:

The reverse engineering of the foot has been completed. We built an exact model of it based on the scan and used this model to design a suitable insole. Now this insole can become the basis for creating individual shoes for our foot. And we've learned how to reverse engineer in Fusion 360.

Other articles in the series:
FreeCAD: реверс-инжиниринг механических форм
Geomagic Design X: выравнивание и редактирование сетки
Geomagic Design X: реверс-инжиниринг органических форм