it is an acadamic project about how to create complex geometry for heatsink. In this project i designed a heatsink by implementing thermal topology optimization technique using altair's hyperworks Optistruct solver and manufactured it using additive manufacturing to obtain complex geometry for convective heat transfer.

1. THE PROJECT ENTITLED
HEAT SINK USING ADDITIVE
MANUFACTURING
PREPARED BY
ANKIT SUTARIA 1001505011
UNDER THE GUIDANCE OF
DR. ROBERT. M. TAYLOR
DEPARTMENT OF MECHANICAL AND AEROSPACE
ENGINEERING
THE UNIVERSITY OF TEXAS AT ARLINGTON

2. HEAT SINK USING ADDITIVE MANUFACTURING
UNIVERSITY OF TEXAS AT ARLINGTON 2
TABLE OF CONTENTS
Introduction and Project Description 3
Additive Manufacturing Process Discussion 4
Component Design 6
Build Preparation 8
Build Execution and Post-processing 8
Conclusion 10

3. HEAT SINK USING ADDITIVE MANUFACTURING
UNIVERSITY OF TEXAS AT ARLINGTON 3
OBJECTIVE
To design a heatsink by implementing thermal topology optimization technique and manufacture
it using additive manufacturing to obtain complex geometry for convective heat transfer.
INTRODUCTION AND PROJECT DESCRIPTION
Additive Manufacturing (AM) is a layer-based approach used for the creation of parts directly
from Computer-Aided Design files. Rather than utilise subtractive methods to remove material
from a larger piece, parts are built by bonding successive layers of material typically through heat
input, a binder, or by chemical means. This approach made production of components with
complex geometries possible which were impossible to create using conventional manufacturing
processes. After decades of research additive manufacturing is now reached a stage of maturity
where additively manufactured parts are now compared to those well-established manufacturing
methods.
A heatsink are used to transfer heat of electronic or mechanical devices away from the device by
a fluid medium, often air or a liquid coolant. It transfers thermal energy from high temperature
device to low temperature device. Thereby regulating the device’s temperature at optimum levels.
For computing devices heatsink are used to cool CPU or GPU. It is also used in high power
semiconductor devices such as lasers and LEDs where component itself cannot moderate its
temperature. Heatsinks are designed such a way that it increases the surface area in contact with
the cooling medium surrounding it. The Most common heatsink materials are copper and
aluminium alloy with thermal conductivity of 401 and 237 [W/mK].
Historically, air cooling has been the preferred method to transfer heat due to its simplicity,
reliability, and lower cost of operation. Air cooling relies on the natural circulation of air caused
by density difference between hot air and the surrounding cold air environment. Figure shows
typically designed heatsink available in market for surface mount devices. The limitation with
these heat sinks is the surface area requirement of the design. The heat transfer rate can be
increased in these heatsinks by increasing surface area and applying forced convection, which will
end up consuming more space and external power requirements for fans also increasing the number
of fins in the same size of base area depends on the manufacturing device’s accuracy.

4. HEAT SINK USING ADDITIVE MANUFACTURING
UNIVERSITY OF TEXAS AT ARLINGTON 4
Topology optimization is a mathematical method used to obtain geometries which are objective
based such as minimizing thermal compliance, fixed volume contains, and boundary conditions
with the goal of maximizing the performance of the system. In this project Thermal topology
optimization is used to obtain the 3D geometry of the heat sink. An advantage of topology
optimization is that design concepts are produced quickly compared to the traditional approach of
using parametric analysis. Although the production of the optimized design is quicker, the obtained
design features may be complex to fabricate using conventional machining techniques. Thus, to
improve manufacturability, a fabrication constraint may be incorporated into the optimization
process. In some cases, even after applying a constraint, intricate designs may be challenging to
manufacture using conventional machining. To build complex parts, AM techniques are
considered.
ADDITIVE MANUFACTURING PROCESS DISCUSSION
The AM process required to produce copper heatsinks is Powder bed fusion process (PBF). Powder
bed fusion process does not require any support material as the powder in bed acts as a support
material. In metal PBF there are two processes, (i) Metal laser sintering (MLS) and (ii) Electron
beam melting (EBM). Metal laser sintering uses laser to melt the powder while EBM uses high
energy electron beam to fuse powder particles. This process was developed at Chalmers University
of Technology, Sweden, and was commercialized by Arcam AB, Sweden, in 2001.
Compared to MLS’s laser beam, the EBM process has more efficient electron beam gun. Which
is also more energy efficient than laser technology resulting less power consumption and lower
maintenance and manufacturing costs. The individual scan lines in EBM are indistinguishable
while in MLS the scan lines are easily distinguishable. Also, in MLS the bed is maintained at lower
temperature therefore elevated temperature grain growth does not erase layering effect. However,
in EBM the higher temperature of powder bed and the larger and more diffuse heat input result in
a continuous grain pattern. EBM parts are less porous than MLS microstructure. The residual
stresses are less in EBM parts than MLS parts. Less supports are required in EBM compared to
MLS. Due to these reasons EBM is selected for heatsinks over MLS.
The schematic diagram of EBM machine is shown in fig (b). EBM machine consists of filament,
grid cup, anode, focus lens-controls spot size, deflection lens-controls x-y motion, powder hopper,
vacuum chamber and build platform. The EBM machine selected to build the heatsink is Arcam
Q10 fig (a). The Arcam Q10 has maximum build size of 200*200*180 mm (W*D*H) which is
closest to the heat sink dimensions 100*100*100 mm.
The electron beam is generated in an electron beam gun at the top of vacuum chamber. The beam
is deflected using deflection lens to reach whole build area. Filaments emits the high temperature
electron which are then accelerates into electric field. Electron beam is controlled by two magnetic

5. HEAT SINK USING ADDITIVE MANUFACTURING
UNIVERSITY OF TEXAS AT ARLINGTON 5
fields which focuses the beam and deflects to desired point. Powder hopper spreads the powder
over the bed after each successive layer. Which is either by counter rotating roller or by a doctor
blade. The powder bed is maintained at high temperature for steady state uniform temperature in
the build tank resulting better grain structure.
EBM can produce parts faster by creating multiple melt pool and moving electron beam
instantaneously which can dramatically speed up production of overall product.
The EBM machine requires conductive materials which can transfer electricity faster so that the
powder particle should not become highly negatively charged. The geometry needs to be optimized
for EBM machine also it requires clean build place and proper placements of build on the start
plate. It requires proper vacuum chamber to manufacture the part.
Advantages of EBM
• Faster build speed due to high power

6. HEAT SINK USING ADDITIVE MANUFACTURING
UNIVERSITY OF TEXAS AT ARLINGTON 6
• Multiple melt pool can be achieved without moving parts resulting in high scanning speed
and low maintenance
• No impurities such as oxides and nitrides due to vacuum chamber
• Due to vacuum melt, high yield strength properties of the material
• Achieve high energy level in a narrow beam
Disadvantages of EBM
• Requires vacuum which increase cost of machine
• Post processing is required for better surface finish and for supports removal
• Only conductive materials are compatible
• Produces X-rays while in operation which requires shields inside vacuum chamber
Process Diagram
The above diagram consists of important part of the manufacturing process of heatsink. The CAD
file is generated according to heat transfer requirements and other specifications. After final CAD
odel is generated it need to be converted to stl file format. STL filr format does not contain
dimentions therefore before printing the part it need to be mentioned in the EBM machine. The
EBM machine generates the G-code for that stl file and determines the number of layers required
for print. The layer thickness and part orientation can be changes according to user requirements.
Then EBM machine starts to print the part and shows the estimated build time. After part printing
the part need to removed from the bed for post processing. After post processing the prt is ready
to be use for operation.
COMPONENT DESIGN
The heatsink need to be produce to increase heat transfer. Therefor the geometry of its stucture
does not matter as long as it improves heat within fixed design space. For the thermal topology
optimization Altair Hypermesh Optistruct solver is used. A 100*100*100 mm cube is taken for
primary part. Conduction and convection thermal analysis are solved by finite element method.
The heat flux and Conduction are applied on each face of each element. Temperature constraints
is applied on the small region of the bottom surface as 0C. The objective is implemented as
minimize the thermal compliance. The responses added are volume fraction(0.3) and thermal
compliance. After the optimization process the geometry of the heatsink was obatined wich is
CAD
convert to
STL
slicing and
GCode
preparation
EBM
process
Post
Process
Finished
Heatsink

7. HEAT SINK USING ADDITIVE MANUFACTURING
UNIVERSITY OF TEXAS AT ARLINGTON 7
shown in below fig. This geometry can only be produced by additive manufacuring due to its
complex branches like structure coming out of the body.
Boundry conditions
Optimized mesh geometry

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UNIVERSITY OF TEXAS AT ARLINGTON 8
BUILD PREPARATION
The above optimized CAD geometry was converted to STL file. The Stratasys uPrint machine was
used to make 3d printed part. The catalystEX software was used for slicing the STL file. the part
was scaled to 0.5% of the original vlume. The material used for the part and support was ABS.
estimated printing of the scaled down part was 6hour and 52 mins. The support structures ar
clearly visible in below figure in white color.
Stratasys uPrint SE part in slicing software
BUILD EXECUTION AND POST-PROCESSING
After all the settngs applied the machine was put to prin the part. The machine has two nozzles.
One foe build material and one for support material. as you can see in the below fig the layers are
clearly visible in printed part. The part still has the support structures around it. The post processing
of this part includes the support removal in chemical lye bath. The temperature of the lye bath is
set to 69C. The ly bath machine took arround 4 hours to remove supports from the part. as you can
see in below fig the part is finished and already has better surface finish. There is no need o do any
other post processing in the part.

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UNIVERSITY OF TEXAS AT ARLINGTON 9
Part Printing End of Part Printing
Lye bath Finished part

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UNIVERSITY OF TEXAS AT ARLINGTON 10
CONCLUSION
• In this project we discussed PBF process such as EBM and MLS.
• We compared both the process and concluded that EBM is appropriate for our part.
• The small branches of the Heatsink did not maintain to stay on the surface of the part
while post processing in the lye bath.
• While printing the FDM was not able to produce the infill correctly and some of the
portions of the part has both support material and part material printed into each other.
• We learned and saw how the parts are actually printed, why we require the support
material and how to remove these supports materials.
• Learned thermal topology in hypermesh optistruct and catalystEXsoftwares to generate
the topology and gcode file.
REFRENCE
• Dede, E. M., Lee, J., and Nomura, T., 2014, Multiphysics Simulation: Electromechanical
System Applications and Optimization, Springer, London.
• https://www.lboro.ac.uk/research/amrg/about/the7categoriesofadditivemanufacturing/po
wderbedfusion/
• Ian Gibson, David Rosen, Brent Stucker “Additive Manufacturing Technologies, 3D
Printing, Rapid Prototyping, and Direct Digital Manufacturing Second Edition”
• http://www.arcam.com/wp-content/uploads/Arcam-Q10.pdf
• Morgan Larsson, Ulf Lindhe, Ola Harrysson “Rapid Manufacturing with Electron Beam
Melting (EBM) – A manufacturing revolution?”
• https://images.google.com/
• Thermal Topology Optimization in OptiStruct Software by Xueyong Qu, Narayanan
Pagaldipti, Raphael Fleury, Junji Saiki
• Topology Optimization, Additive Layer Manufacturing, and Experimental Testing of an
Air-Cooled Heat Sink Ercan M. Dede, Shailesh N. Joshi and Feng Zhou