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2012
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MSc Mechanical Engineering
Digital Design & Analysis PG
Christos Kalavrytinos
Reverse Engineering of a CAR Headlamp
Reverse Engineering of a CAR Headlamp
ABSTRACT
The aim of this project was to reduce the weight and cost of the MGF's headlamp
assembly using reverse engineering as the means. Data from a 3D scanner were
used as a basis for the CAD model to be produced using generative surface design
techniques.
The designer considered the implementation of Design for Manufacture and
Assembly (DFMA), Finite Element Analysis (FEA) and Failure Modes and Effects
Analysis (FMEA) methods.
New materials were considered and chosen for the new design. More specifically, the
glass for the lens was replaced by polycarbonate (PC), although PMMA was also
considered. The reflector assembly was simplified and the parts were reduced from
four to one using the segmented reflector design. The lens is now bonded with a
special adhesive to the casing instead of using 5 clips and a seal.
The overall weight reduction achieved was 63.2% mainly due to the polycarbonate
lens which contributed to a 40.4% reduction on its own. The remaining reduction was
due to the segmented reflector design.
The casing design was also simplified to reduce weight and cost of manufacture.
The FEA analysis performed showed that the part can withstand a 3G plus 30%
safety factor vertical acceleration that simulates the vehicle travelling over a speed
bump. The stress and deformation were low thus allowing for certainty that the part
components will not fail even if vibrations and fatigue is considered.
Christos Kalavrytinos Page
Reverse Engineering of a CAR Headlamp
CONTENTS
ABSTRACT............................................................................................................................... I
CONTENTS.............................................................................................................................. II
1.0 INTRODUCTION................................................................................................................1
1.1 OBJECTIVES.....................................................................................................................1
2.0 RELEVANT THEORY.........................................................................................................1
2.1 REVERSE ENGINEERING....................................................................................................1
2.2 RAPID PROTOTYPING.........................................................................................................2
2.3 PRODUCT DESIGN SPECIFICATION.....................................................................................3
2.4 PDS FOR HEADLAMP:.......................................................................................................3
2.5 DESIGN FOR MANUFACTURE AND ASSEMBLY......................................................................4
3.0 MATERIAL SELECTION...................................................................................................6
4.0 COMPUTER AIDED DESIGN.............................................................................................8
4.1 CASING AND LENS ASSEMBLY..........................................................................................10
4.2 REFLECTOR DESIGN........................................................................................................11
5.0 FINITE ELEMENT ANALYSIS.........................................................................................12
6.0 FAILURE MODE AND EFFECTS ANALYSIS..................................................................15
7.0 RESULTS AND CONCLUSION.......................................................................................16
8.0 RECOMMENDATIONS.....................................................................................................16
REFERENCES....................................................................................................................... 18
Christos Kalavrytinos Page
Reverse Engineering of a CAR Headlamp
1.0 Introduction
This project concerns the process of reverse engineering a headlamp assembly of a
1995 MGF car. The headlamp assembly was scanned using a Konica Minolta 3D
scanner and the scan data, otherwise known as point cloud, were processed and
imported in CATIA V5. The main surfaces of the lens were duplicated along with the
more important mounting points of the casing.
1.1 Objectives
In order to successfully complete this reverse engineering process, the following
objectives have been set:
3D scanning of the assembly
Research of reverse engineering, rapid prototyping, headlight design,
regulations
Production of the new Product Design Specifications (PDS)
Application of Failure Mode and Effects Analysis (FMEA)
Consideration of Design For manufacture and Assembly (DFMA)
Produce Computer Aided Design (CAD) solids
Perform Finite Element Analysis (FEA)
Discuss results and recommendations
2.0 Relevant theory
2.1 Reverse engineering
Reverse engineering is a process of measuring, analysing, and testing to reconstruct
the mirror image of an object or retrieve a past event. It is a technology if reinvention,
a road map leading to reconstruction and reproduction. It is also the art of applied
science for preservation of the design intent of the original part.
Reverse engineering can be applied to recreate the high value commercial parts for
business profits. To accomplish this task, the engineer needs an understanding of
the functionality of the original part and the skills to replicate its characteristic details.
(Wang, 2011)
In the case of the headlamp, the engineer is interested in reducing the weight and
cost of the components by redesigning some of the parts and, possibly, materials.
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Reverse Engineering of a CAR Headlamp
Since producing a CAD design from the beginning is difficult, 3D scan data and
reverse engineering of the mounting points and important surfaces will be used as a
basis for building the CAD model.
2.2 Rapid prototyping
Rapid prototyping is the automatic process of constructing parts or components of a
product (sometimes in scale) within a reasonably fast time span, usually by the
additive manufacturing technology. This technology analyses a CAD part and
transforms its shape into a toolpath so that the part can be manufactured by adding
different types of liquid materials which are then cured/ fused.
This technology can be described as "3D printing" as it produces a part without the
requirement of special tools and is, therefore, very flexible and fast.
It is primarily used in various stages of the design process for:
Visualisation
Testing (e.g. packaging constrains)
Increase effective communication
Decrease of development time
Decrease costly mistakes
Minimise sustaining engineering changes
Extent product lifetime by adding necessary features and eliminating
redundant features early in the design
Rapid Prototyping decreases development time by allowing corrections to a product
to be made early in the process. By giving engineering, manufacturing, marketing,
and purchasing a look at the product early in the design process, mistakes can be
corrected and changes can be made while they are still inexpensive. The trends in
manufacturing industries continue to emphasize the following:
Increasing number of variants of products
Increasing product complexity
Decreasing product lifetime before obsolescence
Decreasing delivery time
(www.efunda.com)
In the case study of the headlamp, a rapid prototype can help with testing the
tolerances and packaging limitations on the actual car. Then the parts can be
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Reverse Engineering of a CAR Headlamp
redesigned to eliminate any flaws. This iterative process is the key to obtaining a
quality product within the Product Design Specifications.
2.3 Product Design Specification
Stuart Pugh was one of the first engineers that analysed the design process and split
it into the most important categories. These are the areas that the design team must
consider before they produce the Product Design Specification documents. These
categories can be seen in Fig. 1.
Figure 1, Pugh's wheel (Pugh, 1991)
2.4 PDS for Headlamp:
1.0 Introduction The goal is a quality product that is environmentally friendly
throughout its lifecycle and is lighter and cheaper than the original headlamp made
by Valeo. Only the most important characteristics that will be altered are mentioned
in this PDS.
2.0 Operational Requirements
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Reverse Engineering of a CAR Headlamp
2.1 In Use
2.1.1 The headlamp must weigh approximately 10% less than the original part
(2160.7g).
2.1.2 The headlamp must withstand high temperatures, especially the parts near the
light bulb.
2.1.3 The casing mounting points must be the same with the original part.
2.1.4 The lens must be the same shape as the original part.
2.1.5 The lens material must have good optical quality and resist oxidation from UV
rays.
2.1.6 The reflector must be adjustable in angle.
2.2 Safety
2.2.1 The lens must behave in a safe way during impact, to protect pedestrians.
2.2.2 The sensitive parts should be sealed properly in the casing.
2.2.3 Ventilation holes must be designed to allow for heat dissipation.
2.2.4 Operational and safety instructions must be provided to the user through the
user manual.
2.3 Maintenance
2.3.1 The product must be of high quality and carry a 3 year manufacturer’s warranty.
2.3.2 The change of light bulbs must be easy with proper access points.
3.3.3 It must be made known to the customer that if an attempt to fix the product by
disassembling it will void the warranty.
2.5 Design for Manufacture and Assembly
Design for Manufacture and Assembly (DFMA) is the process of designing a product
while considering the raw material, the tools and processes used for manufacture as
well as the resources needed for assembly of the product. It has a big effect by
decreasing development time and cost.
“It a system comprised of various principles that, when used properly, will improve
the ability for a design to be easily manufactured and assembled. It is most beneficial
to consider these principles during the design phase of new product development.
This system can be divided into three major sections. The first is the raw material…
Second is the machines and processes used to work the raw material…Third is the
assembly of the product. It is during the assembly of the finished product that
provides the greatest opportunity to apply DFMA principles.”
Christos Kalavrytinos Page 4
Reverse Engineering of a CAR Headlamp
(johnyater.hubpages.com/hub/DFMA)
The aim of this report is not to perform a full DFMA analysis. However, the most
important considerations that would be implemented in the DFMA analysis must be
stated.
It is known that the main components of the headlamp assembly will be
manufactured using injection molding since polymers will be used throughout the
parts. The general design guidelines for this specific process are analysed bellow.
Figure 2, Draft angles and ribs (Youssefi, K.)
Figure 3, Rib thickness and sharp corners (Youssefi, K.)
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Reverse Engineering of a CAR Headlamp
Figure 4, Transitions and bosses (Youssefi, K.)
3.0 Material selection
Choosing the correct material for each component of the headlamp assembly is a
very important stage of the design process. Sticking with the same material chosen
by the original manufacturer, Valeo, can reduce development time, but in this case
changing the materials is the only way to produce a lighter and cheaper product.
Research shows that the majority of car manufacturers have switched from glass
headlamp lenses to polymer ones, mostly Polycarbonate (PC). This is an effort to
reduce the weight of the lens, reduce the chances of cracking caused by small rocks/
gravel, and increase the safety of pedestrians during a crash.
The polycarbonate lenses are thinner and more flexible when compared to the glass
lenses, illustrated in Fig. 5, which are thicker, heavier and more brittle.
Figure 5, MGF headlamp lens
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Reverse Engineering of a CAR Headlamp
The CES Edupack material selection software can be used to set limits and analyse
possible material choices for a certain application. In this analysis, the software is set
up to look for polymers with good and excellent optical properties that can withstand
temperatures of up to 100 degrees C so that their prices can be compared. The trend
of the automotive industry at the moment is the use of Polycarbonate for the lenses
of the headlamps and Polymethylmethacrylate (PMMA) for indicators and rear lights.
This is mainly due to the better refractive index of PC (1.54-1.58) compared to PMMA
(1.49-1.5) as shown in Fig. 6.
Moreover, the impact strength of PC (9-10 kJ/m^2) is a lot higher than PMMA's (2.6-
2.9 kJ/m^2) which is a governing factor as far as safety is concerned.
Figure 6, CES Edupack material selection for lens
The casing is made of Polypropylene that withstands high temperatures (100-115
degrees C) is fairly cheap and easy to produce injection molded components from it.
The reflector material is probably a BMC composite with Polyester and other
additives such as glass fibres. All the material information can be found in the
Appendix.
Table 1, Bill of materials
Part No. Part Name Material
1 Casing Polypropylene (PP)
2 Lens Polycarbonate (PC)
3 Reflector BMC composite
4 Cover Caps Polypropylene (PP)
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Reverse Engineering of a CAR Headlamp
4.0 Computer Aided Design
Computer Aided Design (CAD) is the process of designing parts and components
using a computer programme. The headlamp components are designed using CATIA
V5 R20 which produces the 3D solid models as well as an assembly with full
drawings.
The basis of the design is the point cloud (Fig. 7) that was obtained using data from
the 3D scanner (Fig. 8)
Figure 7, Point cloud in CATIA
Figure 8, 3D Scanner and headlamp
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Reverse Engineering of a CAR Headlamp
Using the 3D scan data as a basis, the surfaces of the components can be
duplicated. This can be done by splitting the part using a plane, and following a
curve and extruding it through a guide curve. This procedure can be seen in Fig. 9.
The basic mounting points are also designed first for the casing as they are the only
constrain for the headlamp to fit in its place properly.
Figure 10 illustrates how the surfaces are modelled to be approximately the same as
the point cloud.
Figure 11 shows the surfaces generated for the front of the lens and other surfaces
used to cut and blend the ellipses to obtain a smooth outcome.
Figure 9, Cut part by plane
Figure 10, Lens and casing
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Reverse Engineering of a CAR Headlamp
Figure 11, Surfaces
The casing, lens, reflector and back cover caps were modelled. The exact shape of
the casing was not duplicated as it was simplified in order to reduce weight,
complexity of mold and therefore cost.
4.1 Casing and lens assembly
The casing and lens assembly in the original part was done through the use of metal
clips and a rubber seal. In order to reduce weight, cost and the risk of humidity in the
headlamp, the lens is going to be bonded on the casing using a special adhesive that
when heated a lot, can be removed and the lens can be separated from the casing. A
disassembly method is shown in Fig. 12.
Figure 12, Lens-casing disassembly
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Reverse Engineering of a CAR Headlamp
4.2 Reflector design
In the original design included a 2 part reflector joined with a smaller lens and a seal.
The whole assembly of 4 parts weighed 520 grams. A new trend for reflector design
uses the reflector as a lens too focus light therefore the lens and seal is not needed.
This technology is called segmented reflector design. An example can be seen in
Fig. 13, and Fig. 14 shows the reflector designed in CATIA.
Figure 13, Segmented reflector example
Figure 14, Segmented reflector in CATIA
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Reverse Engineering of a CAR Headlamp
5.0 Finite Element Analysis
Finite Element Analysis (FEA) is the analysis method of dividing a part into small
elements and nodes, so that local stresses and strains can be calculated. It is a
useful tool during the design process, as it can point out weak areas of a part that
need to be redesigned to withstands the specification loads before a prototype is
manufactured.
The general procedure of the analysis is to define the material properties, create a
mesh for the part (i.e. divide it into small elements), apply constrains and degrees of
freedom, apply loads and calculate the results (i.e. stress, strain, deformation).
In order to carry out the FE analysis for the headlamp, the mounting brackets were
considered areas of interest. Therefore, the geometry of the casing was exported
from CATIA as an .stp file and imported into ANSYS. Figure 12 shows the material
properties that were used as found in CES Edupack (edited from Poluthylene) and
Fig. 13 illustrates the geometry of the component and the generated mesh. The
constrains (i.e. fixed supports) and loads applied can be seen in Fig. 14. An
assumption was made that a vertical acceleration of 3G plus 30% safety factor is
applied on the components to simulate the vehicle travelling over a speed bump or
pothole.
Figure 15, Polypropylene properties
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Reverse Engineering of a CAR Headlamp
Figure 16, Geometry and mesh
Figure 17 Fixed supports (blue) and acceleration (yellow)
The model is then solved to obtain values for stress and deformation. Figure 15
illustrates the results for maximum stress at 2.3 MPa and the maximum deformation
of 0.05mm can be seen in Fig. 16.
Therefore, the stress of 2.3 MPa is well within the yield stress for the material used at
37.2 MPa and that ensures the components will not fail in a speed bump scenario
and that it can withstand the fatigue from the vibrations of the vehicle.
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Reverse Engineering of a CAR Headlamp
Figure 18, Maximum stress
Figure 19, Maximum deformation
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Reverse Engineering of a CAR Headlamp
6.0 Failure Mode and Effects Analysis
Failure Modes and Effects Analysis (FMEA) is the process of analysing the ways in
which a part might fail as well as the effects of that failure. The process looks at the
part functions, failure modes (e.g. corrosion), the effects of the failure (e.g. the lens
becomes hazy) and the consequences of the failure occurring (e.g. MOT failure).
These failures are then weighed in terms of the severity of the failure, the probability
of occurrence and the difficulty of detection. These numbers are then multiplied to
produce a Risk Priority Number (or RPN). Therefore, the design team must focus on
the high RPN scores first in order to eliminate design flaws.
An FMEA analysis for a product such as the headlamp, could be very long and time
consuming and therefore only example of possible considerations for the failure
modes and effects are mentioned.
Example: Headlamp lens
Function: Provides protection of interior headlamp components and is transparent
Potential Failure Mode: Oxidation of polycarbonate due to UV radiation (Fig. 15)
Potential Effect: Reduced optical quality, increased glare, MOT failure
Figure 20, Failure mode- foggy lens
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Reverse Engineering of a CAR Headlamp
7.0 Results and Conclusion
The main goal of this reverse engineering process is to reduce the weight, complexity
and cost of the headlamp assembly. Nowadays, there is a trend in the automotive
industry for reducing the weight of the car components to increase fuel efficiency and
reduce cost. As far as headlamp design is concerned, the main breakthroughs over
the past years were the change from the use of glass in the lenses to polycarbonate
as well as the use of the segmented reflector design to reduce the number of parts
used and therefore the weight and cost.
However, this trend has led to the need for the whole assembly to be replaced in
most cases.
Just by changing the material of the lens from glass to polycarbonate, the weight of
the assembly was reduced by 40.4% from 2160.7 kg to 1186.4 kg. Moreover, a
further reduction of the reflector assembly from 520 gr to 30 gr was achieved by
implementing the segmented reflector technology thus achieving an overall weight
reduction of 63.2%.
Furthermore, since the complexity and sharp corners of the casing were reduced, the
manufacturing cost, as well as the tooling (e.g. mold complexity) cost could be
decreased.
In addition, the FEA analysis showed that the part performs within the design
specifications and when subjected to a vertical acceleration of 3G plus a 30% safety
factor, the stress is well below the yield point of the material and thus allows for
certain behaviour even under repetitive loads and fatigue.
8.0 Recommendations
In order for this piece of work to be improved, more careful design according to
Design For Manufacture methods must be completed, in order to introduce features
such as ribs and bosses that can help to further reduce the material used and reduce
the weight.
Moreover, a better quality point cloud could have been achieved if the scanned parts
were sprayed to a matte surface as the reflective surfaces interfere with the scan and
produce false points.
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Reverse Engineering of a CAR Headlamp
The most important factor in the outcome of this report was the personal judgment
since the way each engineer duplicates the surfaces is different ways.
If this project was an actual automotive industry project, there would be a team of
engineers and they would have a chance to produce a rapid prototype to check
tolerances and fits. This feedback would then help to redesign the components
eliminating any flaws and improving the design. This is an iterative process and is
usually performed at least three times before an acceptable outcome is achieved.
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Reverse Engineering of a CAR Headlamp
References
Pugh, S (1991). Total Design: Integrated Methods for Successful Product
Engineering. Addison-Wesley.
Wang, W (2011). Reverse Engineering: Technology of Reinvention. CRC Press.
Youssefi, K. Design for Manufacturing and Assembly Notes. San Jose State
University
Christos Kalavrytinos Page 18