3D scanning and airfoil selection.

3D scanning and airfoil selection
3D scanning is the process of identifying the geometrical information of
the object using 3D scanners. 3D scanners collect the geometrical
information of the object and send it to the computer. Here the different
types of software tools are used to develop the CAD model of the object.
(Barrett and Ning, 2018) (Bhosale, 2018) There are several techniques are
available for scanning the objects. Among them, 3D scanning technology
is used in this project.
In the 3D scanning process, the geometric information of the object is
converted as a set of coordinate values. It is done by the principle of light
emission and recapturing. Here the coordinate values gathered using the
laser or light is called as cloud data. There are a different number of
software packages are available to covert the cloud data into the solid
models. This method has some limitations (Burek, Jamuła and Flejszar,
2019) (Chaudhary and Roy, 2015). Even this method is more accurate
than the other methods like coordinate measuring technique etc. This
method takes some time. Here the sheath of light or laser is used to
capture the data clouds.
System and software description
Hexagon Romer Absolute Arm 7325OSI is a fully integrated 3D scanning
system. It works by projecting a laser light line onto the surface. The
scanner collects geometrical data as points via a laser line. (Cheng, Song
and Tsai, 2012) (De Maesschalck, Lavagnoli and Paniagua, 2013). The
laser line goes through the area until the whole surface is captured. The
scanner movement is done manually and measures very fast
Collecting millions of dots and generates a large number of data in a point
cloud During the printing operation, the blade shall not be shifted. The
scanner is moved manually across the scanning surfaces. (Dhert, Ashuri
and Martins, 2016)
The Hexagon Arm is connected to the software and when scanning is
complete, the software will digitalize and visualize.
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Through the optical scales, in the arm where the scanner is integrated,
the system recognizes the position of the scanner and the angle to the
part. The reverse engineering software used for the data collection and
the data acquisition is following Innovmetric Polyworks works standard
reverse engineering package.
 Fully support all high-density point cloud 3D digitizers
 Includes mesh generation and editing
 Includes parametric 2D sketching tools
 Collecting and Editing the point cloud
Scanning procedure
Firstly, the blade must be fastened into a surface of a scanner so that it is
available to the scanner in all side geometry. (FEA Optimization of
Constructional Parameters of a Wind Turbine Blade Made of Composite
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Material, 2016)The areas of the blade used for the mounting should be
kept to a minimum as they will not be scanned. For this work, The blade
was put on the top of the granite board and the scanner is mounted and
stabilized on the side on the table(Guntur and Sørensen, 2014). To scan
the part and collect data from the point cloud the blade Hexagon Romer
Absolute Arm 7325OSI 3D Laser scanner was used with Polyworks
software. In this way allowed to coordinate the scanner’s speed, distance,
and angular position to optimize point collection without noise and gaps.
Scanning Parameters.
The laser concentration is adjustable according to the blade surface. (He,
2013) (Herrema, Kiendl and Hsu, 2018)The scan has been done
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automatically by pointing the laser at the part and simultaneously.
Immediately, the system adjusts the laser parameters according to the
surface.
The data of the point cloud is organized into a grid in this software. The
area between the grids is set by interpolations steps. The smaller the size
of the grids is set the more detail will be captured. (Herráez, Daniele and
Schepers, 2018)The downside of using a high level of detail is that the
scanner needs to be moved very slowly to capture the necessary detail.
The angle of the camera will constantly change by moving the scanner
around the blade. (Johny K, Solomon and Kumar C, 2017)To scan the
surface that is not directly visible by the camera, it approached by
sideways. This contributes to laser reflections, which are registered as
noise in the point clouds. (Jost et al., 2018) In order to eliminate this
influence, the maximum angle parameters were adjusted. By running
multiple scanning test using different angles, it observed that collected
data are sufficient enough to create a model.
The above figure shows the solid model developed by the software
(Kiatpanichgij, Afzulpurkar and Kim, 2014). The software converts the
cloud data points into the solid works model. The recovered model is not
an exact model of the actual object. It has some defects. (Lin, Wang and
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Dai, 2005) Before carrying out the numerical analysis there is a need for
cleaning and corrections.
Data collection and point cloud
The scanner is manually moved across the blade in order to collect the
data with laser and generate a cloud point(Mohammadi et al., 2015).
(Montlahuc et al., 2019) The blade must not be moved during the entire
scanning process. The scanner collects geometric data as laser line a
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point. The system identifies the position of the various scan positions and
the angle to the blade via the optical scale of the arm in which the
scanner is integrated. The software allows real-time scanning progress on
the objects. The collected point is created together to form a surface.
Processing of the paint cloud
The creatted cloud point is procces using Polyworks software
Cleaning and reducing data
The next necessary step is to remove any captured noise from reflections
which are not needed for further processing. (Montrone, Wever and
Zheng, 2004) (Pourrajabian et al., 2016) The Polyworks software provides
some simple tools for deleting unnecessary data. It was suggested to
reducing the file size by creating a polygon mesh and to continue
developing the CAD model. (Płocica et al., 2015) The Polygon allows to
reduce overlapping of clouds and keeps only clouds of points in areas
where the scan are connected. As shown figure
In order to evaluate the scan accuracy, A histogram analysis is described
as the performance and quality of the scan(Ramesh et al., 2017) (Selvaraj
et al., 2017). A good alignment must be a normal Gaussian distribution in
order to be correct or erased the scanning data, from histogram result
makes possible to recognize.
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For further elaboration, the polygon sections enable to reconstruct the
blade surfaces and sides in order to close gaps and holes. Optimization of
Polygons is built in such ways where the angles, vectors, and size keep as
uniform as possible. (Shaaban, 2017) For this reason, the software offers
tools like automatic hole filling without changing any dimensions. For the
large holes, the software offers interactive hole and gap filling
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From the above figure, we can see the defects. Mostly defects are present
in the edges and the joints. Other than the joints and edges there is no
possibility to occur defects. Now we need to correct these defects
manually. (Singapore Wala, Ng and Narasimalu, 2018)For correcting the
defects hole filling technique is the most suited technique. In the below-
given figure, the hole filling technique has been illustrated.
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