In manufacturing reverse engineering means to fabricate part(s) based on an original component. Modern manufacturing often requires a digital model as a starting point, so the first step of reverse engineering is usually to create such a model. Note that this model is a digital copy of the original part but as in many cases the part is damaged or worn, considerations need to be taken to prevent retaining errors from a worn part.
The digital model should provide enough information for manufacturing the part. For example, a Mesh model containing 3D surface information of vertices and edges is sufficient for processes like 3D printing. However reverse engineering in general requires a CAD model with defined geometry entities, so the model is adaptive to most manufacturing methods. What’s more, geometry entities in a CAD model can be edited easily if a design change is required later (refer to Reengineering).
To summarise, the first step of reverse engineering is to generate a 3D CAD model of the original part with sufficient geometry details. The CAD model should be as close as possible to the original intended design and considered of wear and tear errors. It can then be modified to suit a certain manufacturing process through CAD/CAM packages and edited to create a design variant if needed.
Taking measurements of the original component is key to reverse engineering. Unless accuracy is not important it is always recommended to use high end measurement tools. Arguably how to create a digital model from a part depends on its complexity. For a simple component, the intuition is to just measure its features with e.g. a CMM and sketch them in a CAD software.
The number of measurements increases significantly for complex components. In this case 3D surface scanners which can capture all measurements simultaneously are used to save time. For larger components and those cannot be physically placed onto a CMM, portable scanners are also favourable.
The downside of 3D scanners is that they can create a large amount of data at a high speed but many of the scanned surface points are redundant for the CAD model output. Only the measurements of features crucial to creating a CAD model are needed. The time spent on processing data and extracting features should also be addressed when using surface scanners for reverse engineering. There are software packages offering ‘Scan to CAD’ options but as we know, automatic feature extraction only works to some extent. This is even more difficult when the scanned data contain wear and tear errors from the part which prevent geometry features to be automatically recognised.
Therefore, creating a proper digital model of a complex component requires good 3D modelling skills in CAD. Advanced measurement and software tools can help but it is nonetheless time-consuming and there isn’t a universal approach.
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