This is a project that was carried out to find methods of re-engineering capability of a given aircraft part. The component was measured using Coordinate Measuring Machine, Faro Arm and manufactured using CNC machine. The corresponding presentation is in the following link https://www.slideshare.net/Lahiru_Dilshan/reverse-engineering-of-aircraft-parts-with-faroarm-and-cnc-machine-169967041

1. Reverse Engineering of Aircraft
Parts Using FAROARM and CNC
Milling Machine

2. 1
1 Abstract
Reengineering process of aircraft component is discussed in this project. There is a
procedure of reengineering process and that involves high technology and computer software.
Here use FARO Arm and Coordinate Measuring Machine to collect data points from the
component and use SolidWorks, Geomagic software to model component. Problems
encountered during process, errors and solutions are discussed at the end.

3. 2
2 Table of Contents
1 Abstract .......................................................................................................................1
2 Table of Contents ........................................................................................................2
3 List of Figure...............................................................................................................3
4 List of tables................................................................................................................3
5 Introduction.................................................................................................................4
6 Procedure.....................................................................................................................7
6.1 Scanning Phase ....................................................................................................8
6.2 Modelling phase...................................................................................................9
6.3 Manufacturing phase..........................................................................................13
7 Occurrences of errors and minimizing errors............................................................16
7.1 During Scanning Phase......................................................................................19
7.2 During Modelling Phase ....................................................................................19
7.3 During Manufacturing Phase .............................................................................20
8 Results.......................................................................................................................21
9 Conclusion.................................................................................................................22

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3 List of Figure
Figure 1 - Reverse Engineering Process.............................................................................4
Figure 2 - Aircraft Component used in the project – view 1..............................................7
Figure 3 - Aircraft component used in the project – view 2...............................................7
Figure 4 - Scanning the component using FARO Arm ......................................................8
Figure 5 - Initial Point Cloud in Geomagic Software.........................................................9
Figure 6 - Processed Point cloud ........................................................................................9
Figure 7 - Finalized mesh model of the component .........................................................10
Figure 8 - Embossed symbols in meshed model ..............................................................11
Figure 9 - Embossed symbols in the original part ............................................................11
Figure 10 - Completed Mesh Model.................................................................................11
Figure 11 - Finalized solid model.....................................................................................12
Figure 12 - Rendered image of the finalized solid model ................................................12
Figure 13 - Define the stock .............................................................................................13
Figure 14 - Arbitrary machine tools used for simulation .................................................13
Figure 15 - Processes of defining the milling operation...................................................14
Figure 16 - CNC Simulation.............................................................................................15
Figure 17 - Drilling side holes..........................................................................................15
Figure 18 - Identify Critical Features ...............................................................................16
Figure 19 - Measurement of critical features....................................................................17
Figure 20 - Operating CMM machine ..............................................................................17
Figure 21 - Taking coordinates using CMM machine......................................................17
Figure 22 - Measurement of critical features from CAD model ......................................18
4 List of tables
Table 1 - Comparison of measurement.............................................................................21

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5 Introduction
Engineering processes can be categorized as forward engineering and reverse engineering.
Forward engineering is the traditional process that part is design and manufacture from its
initial stage. But in reverse engineering, an existing component is duplicated without its
original drawings, documentation, etc.
Reverse engineering is used in most of the engineering fields such as electrical, electronic,
mechanical, chemical. Sometimes conceptual designs can be directly converted to the
computer-aided design with the help of that. Decrease lead-time, reduce product develop time
make advantages to the competitive global market.
Depending on the contacting between measuring device and the surface of the product,
two methods of reverse engineering data collection can be defined as contact measurement and
non-contact measurement. Trigger data collection and continuous scanning data collection are
Figure 1 - Reverse Engineering Process

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parts of contact measurement. Non-contact measurement is divided into 2 parts as optical and
non-optical. Choosing the appropriate method of data collection is a key factor to reduce errors.
There are lots of parts of different applications in the industry manufactured based on
reverse engineering. But those parts should meet performance standards, the accuracy should
be high and parts should fit perfectly with other components.
The modern aerospace industry is depending on reverse engineering for several reasons.
1. To create parts and tools that haven’t CAD models.
2. To reduce problems encountered during data exchange and data integrity
3. To reduce problems between CAD models and actual tool.
4. To enhance quality and performance in inspections and analysis.
Coordinate measuring machine is a high-precision testing equipment which requires
higher measuring environment and a more frequently used in high-precision data acquisition.
That machine is used to measure the critical features of the original part and could be used to
measure the machined component. That is mostly important to compare the dimensions.
Data acquisition
Depending on the contacting between measuring device and the surface of the product,
two methods of reverse engineering data collection can be defined as contact measurement and
non-contact measurement. Trigger data collection and continuous scanning data collection are
parts of contact measurement. Non-contact measurement is divided into 2 parts as optical and
non-optical. Choosing the appropriate method of data collection is a key factor to reduce
errors.
CMM
Coordinate Measuring Machine (CMM) is a high-precision testing equipment which
requires higher measuring environment and a more frequently used in high-precision data
acquisition.
Faro Arm
The FaroArm renders traditional CMMs, hand tools and other portable CMMs obsolete.
This product is available in different arm lengths depending on the application. General
applications of Faro Arm are measuring inspections, reverse engineering and CAD-to-part

7. 6
analysis. In the aerospace industry, this product is used for tooling and mould certification,
alignment and part inspection. This portable device is designed for comfortable handles with
less overall weight optimization and quick between different probes without calibration. Faro
Arm can be identified as a portable optical scanner which is functioning based on non-contact
measurement method.
Data Processing
Variety of data processing applications are available for reverse engineering compatible
devices;
• Imageware – EDS
• Geomagic Studio – Raindrop
• CopyCAD – DELCAM
• RapidForm – INUS
Geomagic Studio software was used to generate mesh and SolidWorks software was used
to model the solid body. Two SolidWorks Add-ins were used, Power Surfacing and Solid-
CAM. Power surfacing tool was used to generate surfaces from the point cloud and Solid-CAM
was used to create G-Code to simulate the CNC machining.

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6 Procedure
Process of this reverse engineering project can be decided into several subsections as
follows.
1. Scanning Phase
2. Modelling Phase
3. Manufacturing Phase
Each phase has their unique settings and features. There are several software packages
involved for these processes. For scanning phase, used FARO Arm and Coordinate Measuring
Machine. Basically, FARO Arm is used to scan the 3D object and make surfaces from the files.
CMM was used to get the coordinates of the original part and manufactured component but we
couldn’t measure the completed part.
Figure 2 - Aircraft Component used in the project – view 1
Figure 3 - Aircraft component used in the project – view 2

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6.1 Scanning Phase
FARO Arm instrument is used for the scan the component. First of all, FARO Arm should
be calibrated. After that FARO Arm is connected to the Geomagic software through USB cable.
Then place the component on the table without any play. Component should be kept stable
until the whole scanning process complete. Laser strip is used as the scanning tool.
While scanning the component, point cloud is generated on the software in real time.
So, the operator can identify clearly which area is scanned and which area is not. When
scanning probe should be very slowly and uniformly to cover the entire surfaces also avoid the
repeatable scanning movement on same surface. Because when do overlay scanning, it caused
to increase number of points in the point cloud. When there is high number of points in the
point cloud, make very difficult to perform the post-processing. Because that need a Computer
with a powerful CPU and RAMs. So that, reduce of the points in point cloud is necessary in
order to speed up the meshing process.
Figure 4 - Scanning the component using FARO Arm

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6.2 Modelling phase
For the modelling process, first of all import the point cloud of the component to Geomagic
software. After import the point cloud to software it looks like as in figure 5.
Initial point cloud contains more than 2 million points including lot of unnecessary points.
So that, that point cloud need to arrange in the way that deleting unnecessary points. Higher
the number of points in the model, higher the computer power required. So that, reduce the
number of points also helps to increase the computational speed without loss of critical data.
After removing unwanted points, total number of points are around 80,000 and point cloud
is as in figure 6.
Figure 5 - Initial Point Cloud in Geomagic Software
Figure 6 - Processed Point cloud

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Based on that point cloud, mesh is generated as the first step of creating mesh. There are
several spikes, valleys and unevenness of the mesh and all of those overlapped points should
be eliminated and make smooth surfaces as much as possible. Also, there are holes on the
created surface because of the lack of points around those places. Such areas are filled to get
the smooth surface by adding materials by monitoring the geometrical relations. After
considering all these facts, the finalized mesh looks like as in figure 7.
The created mesh is saved in .stl format because, Power-Surfacing Add-in that used in
SolidWorks to generate surfaces is only compatible with that format.
Next step is generating a surface from the mesh. For that model was opened in Power-
Surfacing tool. There was embossed number in the component and that is not a critical feature
of the component as it seems like part number (Figure 8 and 9). So that was removed during
surfacing. Those embossed shaped cost time during machining. After smoothing all surfaces.
that looks like as in figure 10. Then we need to identify critical features of the component and
refine them using from SolidWorks.
Figure 7 - Finalized mesh model of the component

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Figure 8 - Embossed symbols
in meshed model
Figure 9 - Embossed symbols in
the original part
Figure 10 - Completed Mesh Model

13. 12
There are several features that can be considered as critical such as diameter and the center
of the holes. The body shape of the component is not much critical as the shape has not
geometrical features. These critical features should be reconstructed using SolidWorks in order
to get accurate dimensions in the final component.
The diameters of the holes are calculated using 3-point coordinates, measuring the
coordinates from solid model. So that straight holes can be created in the solid body. That
finalized model is as figure 11.
Figure 11 - Finalized solid model
Figure 12 - Rendered image of the finalized solid model

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6.3 Manufacturing phase
To get the part programming for the CNC machining phase and finalize the G-code, used
Solid-CAM Add-in in SolidWorks. First step is to define the stock which is initial work piece.
Here 100mm x 100mm x 70mm (LxWxH) block is defined. Next step is defining the coordinate
system. Typically, it placed in upper corner of the stock.
Next step is defining tools. For this case 1 face tool, 2 end milling tools and 2 drilling tools
is used. Here we use arbitrary and suitable values for tool dimensions. But in real situations we
need to check the available tools in the stocks and applied them.
Figure 13 - Define the stock
Figure 14 - Arbitrary machine tools used for simulation

15. 14
Next step is to define the milling operations. As the first operation in any CNC milling is
face milling. Here used the face milling tool and machined up to top surface of the part. Then
profile milling is done and that for machine the outer profile of the part. Its machine up to top
surface of the flat plate. Here when machining need consider several parameters like how much
step down should applied, technology (how tool is moving like hatching, spiral etc) , rough cut
and finish cut , tool compensation etc. It will tend to a better surface finish without any tool
damages. Next operation is 3D milling. Here a small diameter end mill is used machined the
complex surface of the part. As in profile milling, here also we need to consider same
machining parameters for a better finish and accuracy.
Next operations are drilling. Here 2 difference diameter drill bits are used. After drilling
operation finished, again define another coordinate system to machining the side holes.
Because always milling tool up down movements are lie on the Z axis. Therefore, need to
redefine another coordinate system. For this configuration 1 drilling operation and 1 pocket
milling operations are used (Figure 16).
In SolidCAM, there is a facility to simulate whole machining processes. It is very useful
to check how is the tool paths are made, how much time will take for each machining process.
If a tool or tool holder collides with workpiece simulation will indicate a warning message. It's
very useful to the operator to save tools, workpiece as well as CNC machine.
Figure 15 - Processes of defining the milling
operation

16. 15
We couldn’t complete the manufacturing stage because of the lack of materials. So that,
that phase is not completed in this project.
Figure 17 - Drilling side holes
Figure 16 - CNC Simulation

17. 16
7 Occurrences of errors and minimizing errors
The difference between accuracy and error should be identified. Accuracy can be defined
as the degree of agreement of a finished part with the required geometrical accuracy and
dimensional accuracy. The error can be defined as the deviation of the measurements of a
finished part with the theoretically required value to produce a workpiece of the specified
tolerance. [Real Time Compensation of Machining]
In this case, errors can be introduced mainly in three phases of the project which are during
scanning, during modelling and meshing and also during manufacturing. The identification of
the degree of error along with a comparison between the two parts can be done using
Coordinate Measuring Machine (CMM) followed by a simple procedure.
1. Identify critical features of the original part
Holes can be identified as the critical features of the given part as highlighted in
the figure.
2. Measure the critical features of the original part using CMM
The average measurement of the critical features was taken
Figure 18 - Identify Critical Features
1
9
8
7
6
5
4
3
2

18. 17
Figure 19 - Measurement of critical features
Figure 20 - Operating CMM machine
Figure 21 - Taking coordinates using CMM machine

19. 18
3. Measure the same critical features of the finalized CAD model
4. Measure the same critical features of the remanufactured part using CMM
Could not be completed as manufacturing stage is not completed in this project
Figure 22 - Measurement of critical features from CAD model

20. 19
7.1 During Scanning Phase
Most of the errors are caused because of human judgment so that, portions of the data will
be lost or there will be holes. Sometimes, the properties of the object will be the reason. These
errors can be reduced using more scanning angles.
Factors which affects to reduce the error of measurements taken from CMM can be listed as
follows,
• Machine should be clean before and after the work
• Standard temperature should be maintained
• Measuring equipment and workpiece should be placed with less vibrational
disturbance
• Air should be kept dry as far as possible
• Intrusion of oil water that has an impact on the machine should be avoided
Factors which affects to reduce the error of measurements taken from the Faro Arm can be
listed as follows,
• Reflection characteristic of the workpiece surfaces (reflectivity)
• Roughness of the part surfaces
To avoid and minimize these errors,
• Workpiece surface should be sprayed with suitable colored imaging agent
• A measurement site with appropriate lighting conditions and less noise should be
selected
• Reference points should be posted in a flat place with the number of at least 3, and
well distributed in the measurement area
7.2 During Modelling Phase
When someone trying to model a component with single scanned data, that will cause an
error. So, the best way of making multiple scanned files and merge them. During that process,
the individual data should be merged. Also, misaligned and overlapped data should be
eliminated. Otherwise, there will be peaks, valleys and make unevenness in the meshed model.
The surface of the model is represented by a mesh of triangles and polygons. That will
induce an error as the collection of those to generate an approximate shape of the original
object.

21. 20
There are several methods and techniques to reduce such errors and one is modelling the
mesh with Non-Uniform Rational B-Spline (NURBS), that creates the best fit over the mesh
and will give smooth surfaces. So, the error in NURBS is numerical and the software tries to
create the best NURBS surface on the desired tolerance. The parametric approach uses the
mesh as a guide for the model so that the errors will be introduced by the operators as the mesh
depends on human judgment.
7.3 During Manufacturing Phase
During the manufacturing process, it is critical to consider manufacturing tolerances as the
final objective of this project is to compare the original part with the remanufactured part.
Geometrical defects of the machine, wear of the cutting tool and vibration can be identified as
key factors which affect manufacturing tolerances.

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8 Results
The product could not be manufactured due to the limitations of manufacturing phase as
suitable material blocks with required dimensions was not available.
Table 1 - Comparison of measurement
Hole No. Original Part Measurement
(mm)
Remanufactured Part/ Model
Measurement (mm)
Deviation
1 6.2724 7.4800 19%
2 6.4620 7.5100 16%
3 6.2957 7.4900 19%
4 6.4700 6.5400 1%
5 6.3126 7.6500 21%
6 6.3435 6.5200 3%
7 6.3045 7.7100 22%
8 6.4350 6.4800 1%
9 6.2252 7.6900 24%
Some dimensions show a significant deviation from the measurements taken from the
original part using CMM. Higher variations are shown in several holes that are much closer to
the curve surface. Here we can say that, scanner couldn’t make accurate data points near such
places. That was totally because of the operator’s incapability as those critical places should be
scanned more precisely.

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9 Conclusion
This project is focused on the dimensional error in reverse engineering and aircraft
component based on FARO ARM and CMM measurement. Identified critical features of the
component are carefully redesigned and the challenges is that reverse engineering based on
scanning data. The accuracy of the re-engineered part can be improved using mean
measurement in the scan and improve the reliability of the process.
All of the process stages are challenges, capturing, meshing, modelling and simulation.
Most of the steps are based on the operators’ skill and judgment. So that the diameters of the
part are varied in the final product.
There are huge variations in the measurements between the original part and modelled
part. The main reason for that error is operators’ error because the meshing and modelling
phase use the point cloud data and those data completely depend on operator’s judgement. Here
we can see that the holes nearest to the body curves have higher deviations. Those errors can
be reduced by merging several scanned files together or rescanning the object.