# _Skin Imaging_: A Digital Twin for Geometric Deviations on Manufactured Surfaces
## 6 Conclusions  
The _skin imaging_ methodology provides an enriched 2D digital twin of the _actual_ geometric deviation of any manufactured 3D surface including analytical geometries and sculptured surfaces. It is a new paradigm for DZE cyber component of IIS that employs intensity variation to model geometric deviation. The in-process inspection of the geometric deviation of the surface provides live data about the probable manufacturing errors which would be dynamically feed backed to the manufacturing site in order to modify or improve the manufacturing processes or compensate the errors. Skin image can technically provide a rich set of information generated from raw 3D data points into a 2D image, which is much easier and faster for any process. In this paper, the three main steps of _skin imaging_ on any surface, which are Deviation Coordinate system generation, skin matrix generation and skin image generation, have been totally explained. Afterwards, the implementation of the methodology is thoroughly discussed when studying the geometric deviation of cylindrical and spherical surfaces due to their wide application in industry. It was also  
Figure 25: (**a**) Skin image of the cylinder of Figure 24, (**b**) illustration of the detected defect (in red color) and the PC of the segmented defect (in cyan color) on the _skin image_, (**c**) the detected defect in DCS, (**d**) the detected defect on the original cylinder in the scanner coordinate frame (in red color).  
demonstrated that all the 3D information is preserved through _skin imaging_. Moreover, it has been demonstrated through industrial case studies that _skin image_ is capable and efficient at providing valuable information to any manufacturing process upstream or downstream regarding the most likely locations of manufactured surfaces that are susceptible to critical geometric errors, such as out of cylindricity or out of sphericity. It also accurately reports the magnitude of these errors. Additionally, in the SG estimation step of the cylindrical surfaces, an efficient and accurate approach to determine the optimal axis for the best fitted cylinder on the PC is proposed. The _skin imaging_ methodology has been fully implemented and is compatible with the inspection of data points acquired from any kind of metrology devices that provide XYZ information of the measurement points. Future works will deal with other applications of _skin imaging_, such as its utilization in dynamic improvement of other cyber components of IIS in closed-loop metrology.  
Conceptualization, E.G.K., M.M. and A.B.; methodology, E.G.K., M.M. and A.B.; software, E.G.K.; validation, E.G.K., M.M. and A.B.; formal analysis, E.G.K., M.M. and A.B.; investigation, E.G.K., M.M. and A.B.; resources, E.G.K. and A.B.; data curation, E.G.K.; writing--original draft preparation, E.G.K.; writing--review and editing, E.G.K., M.M. and A.B.; visualization, E.G.K.; supervision, M.M. and A.B.; project administration, E.G.K.; funding acquisition, A.B. All authors have read and agreed to the published version of the manuscript. This research received no external funding.  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
The authors declare no conflict of interest.