3D Scan to CAD - learning the basics

3D scanning is an excellent way to bring your real-world object into a digital space for 3D printing, machining, or modifying for new designs by creating mesh files. But it also carries over any imperfections from the real-world part through the scanning process. Or, the mesh file can't be imported into your software and needs to be a solid or surface CAD file for CNC machining. The good news is that mesh files can be made into CAD files with different methods! In this blog, we'll discuss the different methods of Scan to CAD conversion workflows to help you learn what method may be best for your project.

A mesh file converted to CAD - making perfectly sized threaded holes or specific curves.

Mesh file vs. Solid file

3D Scanners produce graphical mesh files by default. This can be helpful for most applications like rendering, 3D printing, or inspection. And the mesh can still be sculpted in programs like Zbrush or Blender - bypassing the need to possibly even convert it into a solid. But if you want to add new features to the model, like threaded holes, this won't be possible without converting it into a solid body first. Converting a mesh into a solid may also be needed to create CnC tool pathing, as many programs can't run collision detection on graphical mesh data.

Solid files also allow you to have perfect dimensions and surface angles for 3D printing or machining. A scanned part will typically include small bumps from natural wear or imperfect shapes. By converting a mesh into a solid CAD body, adjusting dimensions of features or making proper 3D printable features can be achieved.

Converting Mesh to Solid CAD

Mesh to CAD conversion can be done through different methods, but there are three methods that are standard for most parts: Auto-Surface -

By using auto-generated sketch lines, the software will attempt to convert the polygon mesh into a solid body through a series of surface patches. Small imperfections like bumps or scratches will also be included, however, in the new solid/surface body. Additionally, the solid made from this isn't editable like standard CAD files would be; they are a single solid feature and may lose some detail depending on the generated sketch lines.

A mesh file next to an auto-surfaced version. Very similar, but the auto-surfaced solid can be exported as a .step.

If you are attempting to convert a statue into a solid for machining, getting dimensions for drawings, or making a mold, this may be fine for your application. It is the quickest and often seen as the most "one-to-one" conversion of scan data into a solid or surface body, depending on the scan.

Design Intent -

Using the 3D scan as a reference, you can create ideal dimensions and surfaces that match the scan data by using surfaces, sketches, or features extracted from the scan data to drive your design. Making a proper "intended" CAD design of the part. This is the most common method of reverse engineering and is used by anyone looking to manufacture a part or make large changes to a design. This prismatic model can be modified by adjusting dimensions, having new features like threads or text added, or used for assembly design.

A 3D-scanned part that has been converted to a CAD solid with modifications done to certain features for use in a new design.

This method is suitable for most applications and is often seen as the ideal method of converting mesh to CAD models. By using the 3D scan, you can ensure your model's features are in the correct location or check clearances. Keep in mind, however, this is a manual CAD process and requires having software capable of importing mesh data and creating CAD features like sketches or extrusions.

Hybrid Model - Combining both auto-surface and design intent modeling, you can create solid bodies that can keep complex natural shapes but have a properly dimensioned feature combined with it. This method is ideal when most of the object doesn't need to be changed beyond a few features - such as creating flat surfaces to print from, through holes for drilling, or cuts for mounting.

The 3D scan on the left had closed holes at first. Cylinders were added and removed from the mesh data to create through holes.

If you aren't looking to make major changes to an object, this could be a fit for your needs. It allows you to keep as much detail from the scan as possible but clean up some unideal features created from scanning, such as hole diameters, to make future design/printing easier. It is also typically available in sculpting software such as Blender or Zbrush and doesn't require CAD software.

Why convert to CAD

While not all applications need a mesh file to be converted into a solid body, most engineering and manufacturing applications do. It is an important step if you're considering 3D printing, machining, or making new parts from scan data. Additionally, not all programs can read mesh files (.stl, .obj, .ply) and require some form of solid-body data to load properly. 3D scanning allows you to remove much of the CAD guesswork, however, and streamline the design process! Using 3D scans and CAD software, any part can be recreated. If you have any questions or would like to begin a scanning project with us please reach out via arkify3d@gmail.com or using the Contact form on our website!