Sometimes there is no way to fully scan a part that has features hidden from sight. Since optical scanners are analogous to spray-painting with light, you must have line of sight on any feature that you want to “paint.” In many of these cases, the only viable option will be to use an industrial CT scanner. The cost and facilities requirements of CT scanners can be prohibitive for most companies, however, and outsourcing to a CT service provider might delay a project or pose IP issues that take time to resolve.
We’ve already covered techniques for creating models using the auto-surface tool combined with solid primitives. That approach works well for models that are predominantly free form in shape but have some critical areas that need to be expressed as proper CAD features. But what about the inverse?
Most CAD users are familiar with the relative difficulty of modeling organic shapes and complex curvature using traditional CAD tools. While some CAD programs and reverse engineering programs have automated surfacing techniques to better deal with these geometries, they are not conducive to downstream editing. They also typically do not create perfectly prismatic features like true planar faces and cylinders. Because they are based on splines, they also have trouble defining sharp corners. This makes them often unsuitable for expressing mating surfaces, areas with mechanical function, and other key features that require perfect definition.
Assembly scans are useful in several ways. They are typically more detailed and complete than single scans and can include features that would not be visible or scannable without disassembly. They are useful for viewing internal components and can even be used for diagnosing motion systems.