Useful articles and use cases of 3D scanning

FreeCAD: Reverse Engineering of Mechanical Forms

Reverse engineering is often used to create virtual copies of bracketsentire race car engines and other mechanical objects. This method can help with design or quality control of various industrial products and their parts.

In this tutorial of the Reverse engineering for beginners series we are going to show you how to use FreeCAD for reverse engineering of a mechanical object. FreeCAD is an open-source parametric modeler that is very popular among enthusiasts in the areas of 3D scanning and additive technologies.

FreeCAD allows you to:

  • easily modify your design by going back into the model history and changing its parameters;

  • sketch geometry constrained 2D shapes and use them to build 3D models;

  • customize the program by adding various modules and recording macros;

  • work with many file formats such as STEP, STL, IGES, and others;

  • study robot movements using a built-in robot simulation module.

In this article we show you:

  • how to import 3D scans in FreeCAD for reverse engineering;

  • how to perform reverse engineering in FreeCAD.

We look at the following points:

  • Works with Meshes module;

  • checking the mesh scale;

  • aligning the object in the coordinate system;

  • creating a contour and a solid body;

  • making a thread.

Every step of the process is illustrated with screenshots.

The process of reverse engineering

In order to demonstrate how reverse engineering works in FreeCAD, we have found a tiny nozzle and scanned it. Mechanical forms are usually simpler than organic ones. Take our nozzle: it’s symmetrical and geometrically simple.

Let’s see how FreeCAD can help us turn this blurred 3D scan into a working model.

1.  Let's start reverse engineering with Work with Meshes:

2. Import 3D scan data (.stl):

3. We need to check the scale of the mesh by measuring a known distance:

4. Align the object in the coordinate system:

5.  Switch orthogonal views and move the mesh until it is set it in the desirable position:

6. Let's copy the mesh to make a section with the Trim tool:

7. Assign different colors for these two meshes:

8. Switch to the Part module to create a trimming tool. Construct a plane through the point of origin and define its position and size:

9. Trim the mesh with the plane:

10. Let's use the cross section for construction:

11.  Now we need to switch to the Part Design module to create an external contour:

12. Let's choose a sketch plane:

13. We can adjust the grid if we want to use it during construction:

14. We're going to divide the detail into two parts to demonstrate how a Boolean operation works. Create a profile of a first part:

15. The construction process is accompanied by the automatic constraint imposing:

16. Let's create the top of the body by revolving the profile around the part axis:

17. Construct the bottom in the same way:

18. Combine the two parts together:

19. Create a body with a hexagon profile:

20. Perform trimming:

21. Construct a body with a conic part and subtract it from the workpiece:

22. Now we need to make a thread. Define a profile (a triangle) and a path (a helix) for a sweep operation:

23. And attach the thread to the main body:

24. As a final step, we create fillets according to the mesh:

25. The model can be saved as .stp or .igs:

The results of reverse engineering

The result of our work is the exact 3D copy of the nozzle. The shape and scale of the copy match the characteristics of the real part since we used a 3D scan. Now it can be used to produce another part or to continue the design process. We’ve learned how to perform reverse engineering in FreeCAD, and now we can repeat those steps with any other mechanical object.

Other articles in the Reverse engineering for beginners series:

Rhinoceros: The Use of RhinoResurf in Processing of Organic Forms

SolidWorks: Reverse Engineering of Organic Forms

Geomagic Design X: mesh processing