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Lappeenranta University of Technology
Faculty of Technology
LUT Metal Technology
BK10A0401 Bachelor’s thesis and seminar
Benchmarking of laser additive manufacturing process
Lappeenranta 03.10.2012
Ville Matilainen
TABLE OF CONTENTS
LITERATURE REVIEW .................................................................................................... 2
INTRODUCTION ............................................................................................................... 2
1.1 PRINCIPLES OF LASER ADDITIVE MANUFACTURING (LAM) ........ 3
1.2 Basics of CAD-processing ............................................................................. 3
1.3 Basics of laser additive manufacturing .......................................................... 4
2 BENCHMARK MODEL ............................................................................................ 5
3 TEST METHODS ..................................................................................................... 10
4 EXPERIMENTED PROCESSES ............................................................................. 10
5 RESULTS AND DISCUSSION ............................................................................... 13
5.1 Geometrical features and dimensional analysis ........................................... 13
5.2 Mechanical properties .................................................................................. 20
5.3 Reliability and economical aspects .............................................................. 24
6 AIM AND PURPOSE OF THIS STUDY ................................................................ 28
7 EXPERIMENTAL PROCEDURE ........................................................................... 28
7.1 Materials used in this study.......................................................................... 29
7.2 Lasers used in this study .............................................................................. 29
7.3 LAM machine used in this study ................................................................. 30
7.4 Analysis methods used in this study ............................................................ 31
8 RESULTS AND DISCUSSION ............................................................................... 32
8.1 Geometrical features and dimensional analysis ........................................... 35
9 CONCLUSIONS....................................................................................................... 44
10 FURTHER STUDIES ............................................................................................... 45
REFERENCES .................................................................................................................. 46
Appendix I Measurement data
Appendix II Diagrams of measurement results
2
LITERATURE REVIEW
INTRODUCTION
The laser additive manufacturing (LAM) has gained considerable interest in past few years. The
biggest issue on this interest is that the quality of the laser additive manufactured parts is on such
high level that the parts can be used in different industrial fields as functional parts. Also the
possibility to create geometrically complex parts and working prototypes has raised the interest.
Laser additive manufacturing is a powder based process that allows designer to create parts that
are hard or impossible to manufacture with conventional methods. Also the possibility to
optimize part weight and strength is an advantage of this technology. Parts are built layer by
layer as the laser beam melts the next layer on top of the previous one.
In this study the accuracy and quality of built parts is evaluated and measured. In literature
review, the part accuracy and quality is studied from four different cases and the measurement
and quality evaluation methods are applied in experimental part. In experimental part three sets
of test pieces are manufactured from stainless steel. The manufactured parts are evaluated and
measured in order to clarify the capabilities and resolution of state of the art LAM machine.
3
1.1 PRINCIPLES OF LASER ADDITIVE MANUFACTURING (LAM)
Laser additive manufacturing (LAM) process is layer-wise material addition technique which
allows manufacturing of complex 3D parts by selective solidification of consecutive layers of
powder material on top of each other. Solid structure is achieved by thermal energy supplied by
focused and computer guided laser beam. The process produces almost full dense parts and they
do not usually need any other post-processing than surface finishing. (Kruth et al., 2010, p. 1)
The advantages of laser additive manufacturing are geometrical freedom, mass customization
and material flexibility. The laser additive manufacturing can be used for building visual concept
models, customized medical parts and also tooling moulds, tooling inserts and functional parts
with long term consistency. This manufacturing process can provide consistency over the
products entire lifeline. It is also important that processes accuracy and ability to manufacture
complex geometrical structures are on a good level. Also the process reliability, performance and
economical aspects like production time and cost will play in a big role in order to use this
manufacturing technique in mass production. (Kruth et al., 2005, p.1)
Of course this technology also has challenges what comes to the part building. First of all, the
designer should know the limitations what this process have, for example that building
overhanging features is very difficult. Also creating thin walls and small features is a challenge.
(Gibson et al. 2010 p. 705) Post processing of the parts should be considered when designing the
geometry of the parts. For example, when building tooling inserts with internal cooling channels,
the channels should be designed in that way, that it is possible to get the loose powder out from
the channels. (Ilyas et al. 2009, p. 430)
1.2 Basics of CAD-processing
LAM manufacturing process starts with the creation of a 3D CAD-model of a desired object.
Then the 3D CAD-model is converted to STL-file. The STL-file defines optimal building
direction of the physical object. The STL-model is based on small triangles, which determine the
accuracy and contours of the whole object. When the STL-file is created and manipulated to
correct orientation or size, the created model is sliced. Sliced model is then transferred to
additive manufacturing machine, which now have the information how to build each layer.
4
Figure 1 shows the basics of model generation in laser additive manufacturing process. (Gibson,
Rosen, Stucker, 2009, p.4-5, Gebhardt, 2003, p. 31)
Figure 1. Model generation in laser additive manufacturing process (Bineli, Peres, Jardin,
Filho, 2011, p.3)
1.3 Basics of laser additive manufacturing
A thin layer of powder is spread across the build area using a powder-leveling blade in laser
additive manufacturing process. The part building process is performed inside a chamber filled
with nitrogen gas to minimize degradation and oxidation of the powder material. The powder
and the building platform are preheated to minimize the required laser energy and to prevent
warping and internal stresses caused by uneven heat distribution during the build. Figure 2
presents the principles of laser additive manufacturing process. (Gebhardt, 2003, p.31)
5
Figure 2. Principles of laser additive manufacturing process (Bineli, Peres, Jardin, Filho,
2011, p.2)
When a thin layer of preheated powder has been formed, a focused laser beam is directed onto
the powder bed and moved by using galvanometric mirrors in scanner so that it melts the
material and form a cross-section of the build part. Once one layer is completed, the build
platform is lowered by one layer thickness and a new powder layer is applied by using the
recoater blade. After that laser beam scans the next slice of the cross-section. This process is
repeated until the whole part is built. Finally, the finished parts are removed from the build
platform, loose powder is cleaned off and other finishing operations are performed, if necessary.
Finishing operations can include machining, sandblasting, sanding and polishing. (Gibson,
Rosen, Stucker, 2009, p.103-105)
2 BENCHMARK MODEL
The benchmark models found from literature were usually designed to analyze the process
accuracy and limitations. Process parameters can be optimized with assist of benchmark studies
in order to manufacture parts with higher quality and accuracy. (Kruth et al. 2005, p. 3)
Kruth et al. studies benchmark models with mechanical features such as density, hardness, yield
stress and Young’s modulus. Also the dimensional accuracy of the build features is studied. The
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benchmark model is shown in figure 3. Dimensions of the benchmark model are 50 mm x 50
mm x 9 mm (Kruth et al., 2005, p. 3-4)
Figure 3. Benchmark model (Kruth et al., 2005, p.2)
The benchmark model consists of sloping plane and rounded corner (see figure 3), where the
stair effect can be verified. It also have 2 mm thin plane where thermal distortions and warpage
can be studied. The precision and resolution of the used process can be tested with small holes
and cylinders (ranging from 0.5 to 5 mm diameters) and with thin walls (ranging from 0.25 to 1
mm thickness) as shown in figure 3. The sharp edges of the benchmark model can indicate the
influence of heat accumulation and possible scanning errors. The overhanging surfaces can prove
the ability to manufacture overhanging structures without support structures. All of the
geometrical features also measure the accuracy of the process in x, y and z-direction. The solid
half of the model is used for mechanical testing to figure out the mechanical properties of each
benchmark model. (Kruth et al., 2005, p.2)
Another benchmark model is presented by Castillo. This benchmark model is designed and
created specifically to study geometrical features and accuracy of different additive
manufacturing processes. Benchmark model and its measurements are shown in Figure 4.
(Castillo, 2005, p.6)
7
Figure 4. Benchmark model (Castillo, 2005, p.6)
Main goal of benchmark model of Castillo is geometrical and mechanical properties. Castillo
concentrates on the overhang features, heat distortions, building angles, and resolution in narrow
and high details and also in small holes and thin walls. The mechanical properties of the
manufactured models are also studied. Like Kruth et al, benchmark models of Castillo are
manufactured by different additive manufacturing methods and compared to each other.
(Castillo, 2005, p.6-9)
In article by Vandenbroucke and Kruth, the benchmark pieces were manufactured to evaluate the
suitability of laser additive manufactured parts in use in medical field. The benchmark pieces
shown in figures 5 and 6, are designed for evaluating the process accuracy and the suitability to
manufacture small details. (Vandenbroucke, Kruth, 2007, p. 198-199)
8
Figure 5. Benchmark piece for process accuracy evaluation (Vandenbroucke, Kruth, 2007,
p. 199)
Figure 6. Benchmark piece for evaluating feasibility to build small features
(Vandenbroucke, Kruth, 2007, p. 199)
Vandenbroucke and Kruth also studied surface roughness of manufactured pieces. In this study,
the laser additive manufactured pieces mechanical properties, such as density, hardness and
tensile strength were compared to bulk materials mechanical properties. (Vandenbroucke, Kruth,
2007, p. 199-200)
Geometrical accuracy is studied in article by A.L. Cooke and J.A. Soons. In this article, the
benchmark pieces are manufactured with electron beam and laser additive manufacturing. The
9
test part is Aerospace Industries Association (AIA), National Aerospace Standard, NAS 979
standardized test piece. The test piece consist circle-diamond-square features, with inverted
cone. The test piece is shown in figure 7 and 8. (Cooke, Soons, 2010, p. 2)
Figure 7. Geometrical features of benchmark piece (Cooke, Soons, 2010, p. 3)
Figure 8. Top view of the benchmark piece (Cooke, Soons, 2010, p. 3)
This test piece is originally designed for testing CNC-machines performance and machining
quality. This piece is measured for its features size, flatness, squareness, parallelism and surface
10
finish. The test part is not designed to highlight errors of AM systems, but it is used for
determine what kind of geometrical errors AM parts have. (Cooke, Soons, 2010, p. 2)
3 TEST METHODS
The dimensional accuracy was tested with digital caliper and the measurements were averaged
after five times measurements. Also the build quality of the geometrical features, such as thin
walls, small holes, small cylinders, overhanging features and build angles are evaluated visually.
Surface roughness is measured with surface roughness meter and solid part of the model is
mechanically tested. In article by Castillo, the benchmark pieces are also scanned and the
scanned data is compared to original STL-file. (Kruth et al., 2005, p. 2, Castillo, 2005, p. 19)
The benchmark pieces in article by Cooke and Soons are measured by using coordinate
measuring machine. The measurement data is compared to test pieces original STL-file. (Cooke,
Soons, 2010, p. 3-4)
4 EXPERIMENTED PROCESSES
The benchmark pieces were manufactured by using five different SLS/SLM machine in study of
Kruth et al. Machines differ in respect of laser source, optics, powder deposition, scanning
equipment and environmental control system. The process parameters are optimized for each
process depending on the applied binding mechanism and used powder material. Table 1 shows
specifications of the used SLS/SLM processes. (Kruth, et al. 2005, p.2)
Table 1. Specifications of experimented processes. (Kruth et al. 2005, p.2)
Nr Equipment Binding mechanism Material Laser
power
Layer
thickness
1 3D Systems
DTM
Liquid phase sintering (polymer
binder)
Polymer coated
stainless steel 10 W 80 µm
2 Concept Laser Full melting Hot work tool steel 100 W 30 µm
3 Trumpf Full melting Stainless steel 316L ≤ 200 W 50 µm
4 MCP-HEK Full melting Stainless steel 316L 100 W 50 µm
5 EOS Partial melting Bronze based 221 W 20 µm
The equipment and materials used by Castillo are shown in Table 2.
11
Table 2. Specifications of experimented processes (Castillo, 2005, p.10)
Nr Equipment Binding mechanism Material Layer thickness
1 Concept Laser M3 Linear Full melting Stainless steel 316L 30 µm
2 MCP Realizer SLM Full melting Stainless steel 316L 75 µm
3 ProMetal R2 Liquid phase sintering
(resin binder) S4 (60% Stainless steel+40% bronze) 100 µm
4 Trumpf Trumaform 250 Full melting TiAl 6 V4 50 µm
Studied processes vary by binding mechanism of the used powder (see table 1 and 2). Binding
mechanisms are: liquid phase sintering, full melting, and partial melting. Polymer or resin
coating of the powder grains act as a binder in liquid phase sintering. This coating liquefies by
the laser beam and binds the stainless steel grains. As an additional step, this process needs a
furnace cycle in where the polymer is burnt out and the part is infiltrated with molten bronze by
using the capillary effect to reach full density. The second binding method is partial melting,
which does not have a clear distinction between the binding material and the structural material.
Molten and non-molten areas can be noticed after fusing the powder. The third binding
mechanism is full melting where the metal powder is melted completely with laser beam. This
creates nearly full dense structures and minimizes the lengthy post processing steps. (Kruth et al.
2005, p. 3, Castillo, 2005, p. 4-5)
The benchmark pieces in article by Vandenbroucke and Kruth, were manufactured with M3
Linear machine by Concept Laser GmbH. The system was equipped with Nd:YAG laser with
maximum power of 95 Watts. The materials which were used were titanium alloy and cobalt-
chromium alloy. The titanium material was commercial powder, but the cobalt-chromium was
self-made with induction melting gas atomization process. Table 3 illustrates the optimized
process parameters for these materials. (Vandenbroucke, Kruth, 2007, p. 197)
12
Table 3. Optimized process parameters (Vandenbouck, Kruth, 2007, p. 200)
Material Ti-6Al-4V Co-Cr-Mo
Melting temperature 1650 °C 1330 °C
Laser power 95 W 95 W
Layer thickness 30 µm 40 µm
Scan speed 125 mm/s 200 mm/s
Overlap 35 % 30 %
Energy density 195 J/mm3
85 J/mm3
Build rate 1.8 cm/h 4.0 cm/h
Part density >99.8 % >99.9 %
Since the titanium powder is highly reactive with oxygen, nitrogen and hydrogen, the building
process was carried out with continuous flushes with argon gas. The cobalt-chromium powder
was processed in nitrogen environment. Because of the physical properties of the cobalt-
chromium material, the process was easier to control. That is also why the cobalt-chromium
material has higher density and build rate. (Vandenbrouck, Kruth, 2007, p. 196,199)
The fourth benchmark piece is manufactured by laser additive manufacturing and with electron
beam additive manufacturing. Table 3 introduces the specifications of experimented processes.
(Cooke, Soons, 2010, p. 3)
Table 4. Specification of experimented processes (Cooke, Soons, 2010, p. 3)
Process Test Part Material Number of Parts Layer thickness
E-Beam
A1 Ti-6Al-4V 1 100 µm
A2 Ti-6Al-4V 1 100 µm
A3 Ti-6Al-4V 1 100 µm
A4 Ti-6Al-4V 2 100 µm
Laser
B1 17-4 Stainless steel 1 40 µm
B2 17-4 Stainless steel 2 30 µm
B3 17-4 Stainless steel 1 20 µm
B4 17-4 Stainless steel 2 20 µm
Five test pieces were manufactured with electron beam additive manufacturing and other five
were manufactured with laser additive manufacturing in article by Cooke and Soons. All the
13
parts were manufactured by service providers who were instructed not to use any post
processing. The test part number B4 was solid piece and the others were built as hollow shells
with wall thickness of 3 mm. All the test parts were removed from the building platform and
therefore they might include some deformation caused by removal. (Cooke, Soons, 2010, p. 3)
5 RESULTS AND DISCUSSION
Main goal in studies represented in this paper has been to understand the possibilities and
limitations of laser additive manufacturing processes and to find potential manufacturing
applications, not comparing the techniques to each other. The main objectives of these studies
are to test build quality of geometrical features like overhangs, small holes and thin walls,
mechanical properties like hardness, tensile strength and densities of the parts. The dimensional
accuracy is also studied as well as the economic aspects such as production time and costs of the
processes. (Kruth et al. 2005, p. 3, Castillo, 2005, p.1, Cooke, Soons, 2010)
5.1 Geometrical features and dimensional analysis
The requirements of process accuracy increases all the time and it is a demand to build high
quality geometrical features. Process parameters have an effect straight on the build quality and
accuracy of the parts. (Kruth et al. 2005, p. 3, Castillo, 2005, p. 19)
Kruth et al. found that geometrical resolution with small hole diameter was 0.5 mm. That means
that it is not possible to build holes with diameter of 0.5 mm or less. This is because of the loose
powder is also melting by the surrounding heat. Minimum wall thickness is dependent on laser
spot size, which means that the thinnest wall that can be built has thickness equal to the diameter
of laser spot. The cylindrical features smaller than 0.5 mm cannot be built because of the
strength of small features are insufficient to resist forces of the powder spreading recoater.
Figure 9 shows different geometrical features of the benchmark pieces. (Kruth et al., 2005, p. 3)
14
Figure 9. Examples of geometrical features of benchmark pieces (Kruth et al., 2005, p. 3)
As it can be seen from figure 9 section a, the upper picture shows good build quality of
cylindrical features and sloping features, whereas the lower shows bad build quality. Section b of
figure 9 reveals good build quality of thin walls and holes. Section c shows the good and bad
build quality of sharp corners, where section d shows good and bad quality of overhang features.
(Kruth et al., 2005, p. 3)
The dimensional analysis was made to study the accuracy of the used processes. The
dimensional analysis is shown in table 5. (Kruth et al., 2005, p. 3)
EOS
Trumpf
Trumpf
Trumpf
Concept
Laser
3D
Systems
3D
Systems
MCP-
HEK
15
Table 5. Dimensional analysis of benchmark pieces (Kruth et al. 2005, p. 3)
Nominal dimension
3D Systems DTM
Concept Laser
Trumpf MCP-HEK EOS
Length 50 mm
50.59 50.08 50.12 50.78 50.16
Width 50 mm
50.22 50.09 50.11 50.73 50.18
Height 7 mm
7.05 6.96 7.12 7.12 7.03
Hole 1 Ø 5 mm
5.03 4.87 4.84 4.67 4.83
Hole 2 Ø 2 mm
1.96 1.97 1.95 1.72 1.77
Hole 3 Ø 1 mm
Badly built Badly built 0.95 Badly built 0.90
Hole 4 Ø 0.5 mm
Not built Not built Not built Not built Not built
Cylinder 1 Ø 5 mm
4.95 5.03 4.96 5.35 5.12
Cylinder 2 Ø 2 mm
1.90 2.05 1.97 2.23 2.10
Cylinder 3 Ø 1 mm
0.97 1.06 1.02 1.25 1.12
Cylinder 4 Ø 0.5 mm
Not built Not built Badly built 0.64 0.63
Wall 1 1 mm
0.97 1.23 1.04 1.34 1.16
Wall 2 0.5 mm
0.71 Not built 0.55 0.76 0.68
Wall 3 0.25 mm
Not built Not built 0.33 0.47 0.47
Stair effect
Bad Good Bad Bad Good
Curling Good Good Bad Good Good
Sharp corners
Too Short Good Too short Too short Good
Overhangs Good Badly built Badly built Badly built Badly built
As it can be observed from table 5, the features like holes and cylinders are very difficult to build
if the diameter is less than 1 mm. The stair effect on sloping planes and rounded corners varies
with different manufacturing processes. The stair effect generates from the layer thickness which
the process uses. A solution to decrease the stair effect is to decrease also the layer thickness.
Layer thickness is dependent on powder particle size which also gives some restrictions to part
resolution. (Kruth et al. 2005, p. 4)
16
The thermal stresses and curling of thin sections of the benchmark piece is avoided by using full
supports for supporting and attaching the part to the building platform. Only one experimented
process suffers from warpage and it is because the support structure was fine grid-like support
instead of full dense support. Also building of sharp corners is a challenge. The correct scan path
of the laser beam is crucial in order to create sharp corners. Otherwise the heat accumulates to
the tips of the corners and the corners build up too short. The overhanging features are difficult
to build in high quality. Near horizontal overhanging surfaces are very difficult to build without
support structures. Since the melted powder material have no support from below, the molten
material flows down and the bottom surfaces are not finished well as seen in figure 9 section d.
(Kruth et al. 2005, p. 4)
In benchmark study by Castillo, the same kinds of building defects were found. The overhanging
features were usually badly built and most of the benchmark pieces included support structures
in overhanging features. In figure 10 and 11 is shown details of one benchmark piece. (Castillo,
2005, p. 18)
17
Figure 10. Overhanging features with support structures (Castillo, 2005, p. 18)
Figure 11. Details of benchmark piece (Castillo, 2005, p. 18)
As it can be seen from figure 10 the overhanging features need support structures in order to be
built. Even though this benchmark piece includes the support structures, the overhanging
features and features that are built in angle suffer thickness defects and warpage. The figure 11
presents that the smallest features like cylinders and square tubes are missing. It can also be seen
that the smallest holes are not built. (Castillo, 2005, p. 17-18)
In article by Vandenbroucke and Kruth the feasibility to build small and complex features was
similar than what presented earlier. In this study was also found that the overhanging features
were built badly when they are not supported. The two main reasons for that are that the laser
beam scans in loose powder instead of solid material. Therefore the thermal conductivity
decreases and the temperature increases which leads to instable melt pools. The second reason is
that the instable melt pools form stalactite patterns because the molten material sinks in the loose
powder by the effect of gravity. This effect is always in building process where horizontal holes
are tried to manufacture. Also the small holes of diameter 0.5 mm were not built because the
enclosed loose powder melts because of the surrounding heat. Otherwise the build quality of the
manufactured pieces was in a good level and it was concluded that the parts made by this method
18
were accurate enough to use in most medical and dental applications. (Vandenbroucke, Kruth,
2007, p. 200-202)
In article by Cooke and Soons the dimensional analysis is performed with coordinate measuring
machine and the measurements are compared to the STL-file of the piece. The first comparison
is made with checking the circularity and size of the circle feature. Figure 12 shows the feature
that is compared. (Cooke, Soons, 2010, p. 4)
Figure 12. The circular feature is measured and compared to STL-file (Cooke, Soons, 2010,
p. 4)
The circular feature shown in figure 12 was measured three times at different heights of the
feature. Results of these measurements are shown in table 6. (Cooke, Soons, 2010, p. 4)
19
Table 6. Mean radius error and circularity of built feature (Cooke, Soons, 2010, p. 4)
Process Test Part Mean Radius
Error (mm)
Circularity
Peak to Valley (mm)
E-Beam
A1 -0.130 0.322
A2 0.157 0.249
A3 -0.602 0.214
A4 -0.095 0.352
Laser
B1 -0.084 0.156
B2 0.043 0.094
B3 0.006 0.095
B4 -0.010 0.121
As it can be observed from table 6 the mean radius error is much smaller range in laser additive
manufacturing than electron-beam additive manufacturing process. Since these two
manufacturing processes are not comparable, it can be said that both of these include errors. The
build errors can be seen better from figure 13, which shows the form and size errors of two parts
made with same manufacturing process and same process parameters. (Cooke, Soons, 2010, p. 4-
5)
20
Figure 13. The average of three error traces around the circular feature of two parts made by
the same system. (a) Electron-beam system and (b) Laser additive manufacturing
system (Cooke, Soons, 2010, p. 5)
As it can be seen from figure 13, the error traces show that the error is repeating itself on both
measured parts. This repeatability gives chances to compensate the parameters and optimize the
building process in order to achieve better build quality and accuracy. (Cooke, Soons, 2010, p. 5)
5.2 Mechanical properties
When discussing about the mechanical properties of laser additive manufactured parts, the
following issues should be taken to account. First of all the densities of the manufactured parts,
the surface quality of the parts and of course the mechanical properties which include for
example hardness, yield strength and tensile strength. (Kruth et al., 2010, p. 2-3)
The density issue, when using laser additive manufacturing method is the first and perhaps the
most important thing is this process. The density of the manufactured part determines the
mechanical properties of the finished part. This of course has an effect on the components
performance when it is used as a functional part. Of course the objective is to produce 100%
dense parts, but this is not so simple to achieve since there is no mechanical pressure which
would press the powder layers against each other, only gravity, temperature effects and capillary
force are affecting into the build part. When the laser beam has melted the powder material the
21
solidification starts, and since the solidification happens rapidly, gas bubbles may get entrapped
in the material. These entrapped gas bubbles forms pores to the build structure which may cause
a failure when the part is under stress. In figure 14 is shown cross-section of laser additive
manufactured part. (Kruth et al., 2010, p. 2)
Figure 14. Micrographs of cross-section of laser additive manufactured part with 4x
magnification and 10 x magnification (Kruth et al. 2010, p. 2)
As it can be observed from figure 14, the small black spots throughout the part are pores which
are formed during the manufacturing. The gas bubbles during melting and solidification is not
the only factor that can cause low density into manufactured parts. The insufficient surface
quality also effects on density. If the surface is very rough, the roughness peaks and valleys
prevent the recoater to distribute even, homogenous powder layer. This causes variation in layer
thickness and since the thickness is not even, the used laser power may not be high enough to
melt the new layer completely. (Kruth et al., 2010, p. 2)
In study by Kruth et al. (2005) the mechanical properties of the manufactured benchmark pieces
were measured and the measured values were compared to manufacturers stated values. The
10x magnification
4x magnification
22
densities of these parts were measured with Archimedes principle by weighing the samples in air
and subsequently in ethanol to measure and calculate the densities. Table 7 shows the
mechanical analysis of the benchmark pieces. (Kruth et al., 2005, p. 2, 4)
Table 7. Mechanical analysis of benchmark pieces (Kruth et al., 2005, p. 4)
Mechanical property 3D Systems
DTM
Concept
Laser Trumpf
MCP-
HEK EOS
Density (kg/m3) measured 7750 8025 7870 7900 7650
µ-hardness (HV0.100)
material data sheet value 187 420 202 - 117
µ-hardness (HV0.100)
measured 176 ± 10 398 ± 12 251 ± 6 233 ± 5
185 ±
20
Young’s modulus (GPa)
material data sheet value 137 - - - 80
Young’s modulus (GPa)
measured 37 62 49 54 30
Yield strength (MPa)
material data sheet value 305 1000 500 - 400
Yield strength (MPa)
measured 218 1410 535 598 320
As it can be seen from table 7, all these additive manufacturing processes can produce near full
dense parts. The micro-hardness is rather high for all processes since the melt pool cools down
very rapidly after laser beam has passed the area. The Young’s modulus is measured in this
article by bending test and that is the possible reason why measured values are much lower than
stated ones. The measured yield strength values differ slightly from the stated values, but they
still fulfill the strength requirements for manufacturing. (Kruth et al., 2005, p. 4)
The mechanical properties such as hardness and tensile strength were also measured in article by
Castillo. The results of these measurements are shown in table 8. The Vickers hardness tests
were performed according to EN-ISO 6507-1/98 standard. (Castillo, 2005, p. 28-29)
23
Table 8. Mechanical properties of benchmark pieces (Castillo, 2005, p. 29)
Mechanical property Concept Laser
Laser Cusing
MCP
SLM
ProMetal
3D Printing
Trumpf
Laser Forming
Hardness (HV)
measured 232.6 212.4 256.8 415.6
Hardness (HV)
material data sheet value 230 237 260-300 420
Tensile strength (MPa)
measured 648.76 626.82 358.73 1165.42
Tensile strength (MPa)
material data sheet value 650 627 682 1080-1090
Elongation at break
measured 30.52 20.84 0.56 3.59
Elongation at break
material data sheet value 25 24 2.3 5.8-6.2
As it can be observed from table 8 the measured values does not differ much from the
manufacturers material data sheets. The higher tensile strength and hardness of Trumpf Laser
Forming is because the material used with this process was titanium alloy. The tensile strength of
the Pro Metal manufactured part is quite low compared to other processes because the
manufacturing process differs from full melting processes. In this article, the densities of
manufactured pieces were not measured. (Castillo, 2005, p. 29-30)
In article by Vandenbroucke and Kruth, the mechanical properties of the titanium alloy
manufactured pieces were compared to similar bulk materials. The bulk materials were Ti-6Al-
4V alloys, where the other one was annealed and the other was solution treated aged (STA). The
laser additive manufactured part titanium alloy material links up best to the STA treated titanium
alloy. In table 9 is presented comparison of mechanical properties between laser additive
manufactured parts and bulk materials. (Vandenbroucke, Kruth, 2007, p. 200)
24
Table 9. Comparison of mechanical properties between LAM manufactured part and bulk
materials (Vandenbroucke, Kruth, 2007, p. 201)
Mechanical property SLM
Ti-6Al-4V
Annealed
Ti-6Al-4V
(Bulk material)
Solution treated aged
Ti-6Al-4V
(Bulk material)
Density (kg/m3) 4420 4430 4430
Hardness (HV) 410 (micro)
400 (macro) 350 395
Young’s modulus
(GPa) 94 110 110
Tensile yield strength
(MPa) 1125 920 1100
Ultimate tensile strength (MPa) 1250 1000 1200
Elongation at rupture
(%) 6 12 10
Young’s modulus (bending) (GPa) 93 110 110
Bending yield strength (MPa) 1900 1500 1800
Ultimate bending strength (MPa) 2000 1900 2050
As it can be seen from table 9, the mechanical properties of laser additive manufactured parts can
achieve similar mechanical properties than bulk materials. The hardness of laser additive
manufactured part is higher because during the build process the melt pool solidificates and
cools down very rapidly after the laser beam has passed. The elongation at rupture differs from
bulk materials because the ductility of LAM parts is lower than bulk materials. This is because
there encounters slight embrittlement due to the laser melting. (Vandenbroucke, Kruth, 2007, p.
200)
5.3 Reliability and economical aspects
The possibility to use lased additive manufacturing in industrial applications is not only
dependent on geometrical and mechanical properties of the parts, but also on reliability to
produce different parts and minimizing the production time and costs. As it can be seen from all
25
of previously presented studies, the geometrical and mechanical properties of manufactured parts
are on such level that the parts can be used in different industrial fields. (Kruth et al. 2005, p. 5)
Production time of laser additive manufacturing includes the machine and file preparation and
actual part build time. The actual part build time consists of powder deposition and the laser scan
time. The total build time is highly dependent on build height and the layer thickness. The higher
the part is the longer the build time is. The laser scan time is increased when there is geometrical
complexity and large areas to expose. The building times, of benchmark pieces shown in figure
3, are presented in table 10. (Kruth et al. 2005, p. 5)
Table 10. Building time of benchmark pieces (Kruth et al. 2005, p. 5)
3D Systems DTM Concept Laser Trumpf MCP-HEK EOS
27 h 9 h 4.5 h 8.5 h 4.5 h
The build times seems long compared to conventionally manufactured parts, but the freedom to
build complex parts with internal structures gives advantages to this manufacturing method.
Since those manufacturing times does not require manpower the costs are mainly determined by
machine costs. Also it must be remembered that if, more parts are manufactured during the same
build session, the production cost will decrease for each part. (Kruth et al. 2005, p. 5)
In article by Castillo, the building time of benchmark pieces was considered as the total amount
of machine hours and secondary operations, not including finishing processes. Post processes
such as support removal and removal from the building platform is not considered either.
Building time of manufactured parts is shown in table 11. (Castillo, 2005, p. 27)
Table 11. Building time of benchmark pieces (Castillo, 2005, p. 27)
ProMetal MCP Concept Laser Trumpf
65 h 38 h 60 h 39 h
As it can be observed from the table 11, it takes much more time to build higher and complicated
benchmark model compared to one from article by Kruth et al. If the post processing times were
included, the total manufacturing time of Castillo’s benchmark pieces would increase
dramatically.
26
In article by Vandenbroucke and Kruth, the building time of benchmark pieces was not
supported but the build time of dental prostheses framework was presented. The dental
prostheses framework is shown in figure 15. These frameworks are built from either titanium or
cobalt-chromium powder. (Vandenbroucke, Kruth, 2007, p. 202)
Figure 15. Dental prostheses framework (Vandenbroucke, Kruth, 2007, p. 203)
The building time per prostheses framework versus number of produced frameworks are
presented in figure 16. (Vandenbroucke, Kruth, 2007, p. 203)
Figure 16. Build time of prostheses frameworks (Vandenbroucke, Kruth, 2007, p. 203)
As it can be observed from figure 16, the build time per part is decreasing when the number of
frameworks is increasing during the same build. This is because the powder depositing time is
27
spread over all frameworks. Figure 16 shows that if eight frameworks are built during one
production run, the total build time is 16 hours or 2 hours per framework. This is almost half of
the time compared to building only one framework. As it can be seen from figure 16, it is more
economical to build as many parts as possible during on production run. (Vandenbroucke, Kruth,
2007, p. 202)
28
EXPERIMENTAL PART
6 AIM AND PURPOSE OF THIS STUDY
Aim of this study was to determine the limitations of laser additive manufacturing process
resolution and to determine the quality of parts build with state of art LAM machine. It was
decided to manufacture test pieces with different features such as thin walls, small gaps, and
holes which create overhangs. Test pieces were manufactured with prototype LAM machine,
similar to EOS EOSINT M-series machines. The laser used in this study was IPG 200 W
continuous wave fiber laser. All of the test pieces were manufactured from stainless steel
powder.
7 EXPERIMENTAL PROCEDURE
The built pieces included different features and all the pieces were manufactured in the way that
the pieces were placed parallel and in 45º angle against the recoater. The features of different
parts were measured with microscope software and the measurements were compared to 3D
models dimensions. All the parts were built with 5 mm solid supports, which were removed from
the parts when sawed off from the building platform. All of test pieces were manufactured with
building parameters optimized by machine manufacturer. In figure 17 is shown 3D models of
built parts.
Figure 17. 3D models of test pieces
29
7.1 Materials used in this study
Material used in this study was EOS StainlessSteel PH1 Stainless steel powder. The chemical
composition of the material is shown in table 12.
Table 12. Material composition of EOS PH1 (EOS Material data sheet)
Material Concentration
Iron < 80 %
Manganese < 1 %
Molybdenum < 0.5 %
Nickel < 6 %
Niobium < 0.5 %
Silicon < 1%
Carbon < 0.1 %
Chromium < 20 %
Copper < 6 %
This fine powder is a pre-alloyed stainless steel and it is characterized by having good corrosion
resistant and excellent mechanical properties. This type of steel material is widely used in
engineering applications where high hardness, strength and corrosion resistance is required.
Suitable applications can be found for example from medical or aerospace industries. Also this
material can be used for building functional prototypes, small series products and individually
designed products and spare parts. With standard processing parameters it is possible to use layer
thicknesses 20 µm and 40 µm. Mechanical properties of built parts are fairly uniform in all
directions when using standard process parameters. (EOS Material data sheet)
7.2 Lasers used in this study
The used laser in this study was 200 W IPG YLS-200-SM-CW fiber laser. The laser beam is
transferred from the laser source to the galvanometric scanner via optical fiber. The used laser
produces 200 W of power at a wavelength of 1070 nm and the focal length is 400 mm. The spot
size of the laser beam is 70-100 µm.
30
7.3 LAM machine used in this study
Laser additive manufacturing machine used in this study consists of laser unit, process chamber
and process control computer. It is possible to do adjustments to the process with computer. The
LAM machine itself is a prototype machine similar to commercial EOSINT M-series equipment.
The LAM equipment is presented in figure 18.
Figure 18. Prototype LAM equipment, similar to EOSINT M-series equipment
The building process takes place in the process chamber and the process is controlled by
controller computer. The building chamber is divided into three platforms, where the middle one
is the platform where the parts are built. The building chamber is presented in figure 19.
31
Figure 19. Process chamber of the LAM machine
The other two platforms serve as powder dispenser platform and as collector platform where the
extra powder is collected. The powder spreading is done with recoater which spreads the powder
evenly to the building platform. The building platform is heated with thermo elements. The
chamber is filled with nitrogen gas to decrease the oxygen level of the chamber atmosphere. The
level of nitrogen is 99.8 % during the process. Nitrogen works as a protective gas and it helps to
avoid oxidation of the stainless steel parts.
7.4 Analysis methods used in this study
The manufactured pieces were analyzed and evaluated visually. Dimensional analyses are
performed to check process accuracy. The dimensional analysis is made with Axio Vision
microscopy software. Measurements were taken multiple times and averaged. Geometrical
features such as thin walls, narrow gaps and small holes were evaluated visually.
32
8 RESULTS AND DISCUSSION
In this study, the evaluation of geometrical features and process accuracy are the main goals.
Specially building small features like holes, walls and gaps are investigated. This study is also
meant to give limitations and directions of what kind of parts or features can be built. All
measurement data is presented in appendix. In figure 20 is presented test pieces 1A and 1B.
Figure 20. Test pieces 1A and 1B with various wall thicknesses. Arrow shows the direction
of the recoater movement.
As it can be seen from figure 20, the direction of recoater movement has very big impact on part
build quality. The recoater does the recoating with such big power that the thinnest walls
collapse if the part is oriented in 90º angle against the recoater. Otherwise the build quality of
these parts does not differ much when visually analyzed from the top side. For more accurate
analysis the test pieces were visually analyzed from the bottom side also. Bottom side analysis is
quite difficult since the parts are sawed off from the building platform and the sawing might
effect on the small and fragile features. In figure 21 is presented the test pieces 1A and 1B from
bottom side. The test piece 1A (the left side) has also studs in different angles for testing the
minimum build angle.
33
Figure 21. Test pieces 1A and 1B bottom view in same position as in figure 20
As it can be seen from figure 21, the building process of the thinnest walls is not successful. It
can be also seen that the removing of the parts from building platform may break some of the
features.
Test piece 2A and 2B can be seen from figure 22. These test pieces include gaps with different
widths. Also these pieces were oriented to the building platform in such way that they were 90°
and 45° angle against the recoater movement.
34
Figure 22. Test pieces 2A and 2B. The arrow shows the recoating direction
In these pieces the visual analysis was much more difficult since the looks of the parts does not
differ that much. The three stripes which are raised from the surface of test piece 2B are built
because the recoater blade is worn and got some dents in it. Because of that the powder is not
spread evenly and it causes these stripes.
The third test piece set includes parts with different size holes. The test pieces 3A and 3B are
shown in figures 23 and 24.
35
Figure 23. Test piece 3A sides A and B. The arrow shows the building direction
Figure 24. Test piece 3B sides A and B. The arrow shows the building direction
These pieces were also built in the way that test piece 3A was oriented parallel against the
recoating direction and the 3B was oriented in 45° angle against the recoating direction. The
building direction can be seen from the figures 23 and 24 for these pieces. Building of holes is
challenging in this direction since big amount of overhangs are created. The marks and cuts
shown in test piece 3B B-side came from detaching the piece from the building platform.
8.1 Geometrical features and dimensional analysis
Because laser additive manufacturing gives possibilities to manufacture complex shapes and
features to the parts, it was decided to investigate the accuracy of this process with previously
presented benchmark pieces. Measurement data of test pieces 1A and 1B is presented in table 13.
36
Table 13. Measurement data of test pieces 1A and 1B
Wall 3D model dimension
[µm]
1A averaged
measurements [µm]
Difference
[%]
1B averaged
measurements [µm]
Difference
[%]
1 100 255.70 155.70 215.24 115.24
2 200 286.13 43.07 253.85 26.92
3 300 420.25 40.08 423.08 41.03
4 400 506.33 26.58 530.80 32.70
5 500 577.24 15.45 666.67 33.33
6 600 670.89 11.81 764.10 27.35
7 700 762.05 8.86 884.64 26.38
8 800 860.76 7.59 979.49 22.44
9 900 974.68 8.30 1012.82 12.54
10 1000 1068.37 6.84 1120.51 12.05
11 1100 1164.56 5.87 1230.77 11.89
12 1200 1281.01 6.75 1317.97 9.83
13 1300 1298.75 -0.10 1400.01 7.69
14 1400 1410.13 0.72 1494.88 6.78
small 1 100 broken - 228.21 128.21
small 2 200 broken - 323.12 61.56
small 3 300 broken - 556.44 85.48
small 4 400 broken - 602.56 50.64
small 5 500 582.30 16.46 694.90 38.98
small 6 600 660.76 10.13 751.30 25.22
small 7 700 688.63 -1.62 866.76 23.82
small 8 800 764.60 -4.43 974.36 21.79
small 9 900 911.43 1.27 1097.45 21.94
As it can be observed from the table 13, the wall thicknesses of the test pieces are usually thicker
than in the 3D model. The test piece 1A which was oriented parallel to the recoater has more
accurate wall dimensions than test piece 1B, which was oriented 45° angle against recoater. But
then again the small walls are collapsed in test piece 1A when the wall thickness is less than 500
µm. Small walls of test pieces 1A and 1B are shown in figure 25.
37
Figure 25. Small walls of test piece 1A and 1B
The walls of 1A are broken because of the recoater movement. When part is oriented in 45°
angle against the recoater, it is possible to build thin features. But as the figure 21 shows, the
thinnest walls of test piece 1B are not built completely. The first decently built small wall is
number 4 and the thickness of it should be 400 µm. But as it can be seen from table 13 the real
thickness of that wall is 602.56 µm. The dimensional comparison of the test pieces 1A and 1B
can be seen from figure 26.
Figure 26. Wall thickness comparison between test pieces 1A and 1B
y = 1.1317xR² = 0.9689
y = 1.0592xR² = 0.9683
y = xR² = 1
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
0 200 400 600 800 1000 1200 1400 1600
Me
asu
rem
en
ts [
µm
]
Model dimensions [µm]1B 1A Nominal Linear (1B) Linear (1A) Linear (Nominal)
38
As it can be observed from figure 26, the dimensions of test piece 1A are closer to the nominal
values of the 3D model. Wall thicknesses of both test pieces are thicker than in the 3D model.
This happens because the laser melts the cross section of the part, and the loose powder around
the cross section melts also and attaches to the contours. The difference of nominal wall
thickness and wall thickness of test piece 1A becomes less than 10% when built wall thickness is
700 µm. The same difference is achieved with test piece 1B in wall thickness 1200 µm. It seems
that these kinds of features are more accurate when the features are parallel to the powder
spreading direction. Comparison of the small wall accuracy is presented in figure 27.
Figure 27. Wall thickness comparison between test pieces 1A and 1B small walls
As it can be seen from figure 27, also the dimensions of small walls are closer to 3D models
nominal values in test piece 1A. It should be also noticed that the thinnest walls are not built well
in either of the test pieces. In case of test piece 1A it was not possible to measure the thinnest
walls since they were broken, as it can be seen from figure 25. Also the smallest walls were
badly built in test piece 1B as it can be seen from figure 28 where bottom sides of test pieces 1A
and 1B are presented.
y = 1.2869xR² = 0.9053
y = 0.9128xR² = 0.7618
y = xR² = 1
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
0 100 200 300 400 500 600 700 800 900 1000
Me
asu
rem
en
ts [
µm
]
Model dimensions [µm]
1B 1A Nominal Linear (1B) Linear (1A) Linear (Nominal)
39
Figure 28. Bottom sides of test pieces 1A and 1B
As it can be seen from figure 28 the smallest walls are built badly and some of the thinnest walls
are broken during the detaching from the platform.
The widths of small gaps are analyzed in test pieces 2A and 2B. The measurement data is
presented in table 14.
Table 14. Measurement data of test pieces 2A and 2B
3D model gap width
[µm]
2A averaged measurements
[µm]
Difference
[%]
2B averaged measurements
[µm]
Difference
[%]
100 92.31 -7.69 167.74 61.29
200 193.85 -3.08 241.94 20.97
300 301.54 0.51 329.12 -3.08
400 353.85 -11.54 383.87 -7.26
500 427.69 -14.46 474.19 3.23
600 507.69 -15.38 429.03 -32.80
700 600.00 -14.29 548.39 -21.66
800 664.62 -16.92 612.90 -25.40
900 781.54 -13.16 729.03 -26.52
1000 892.33 -10.77 822.58 -17.74
As it can be seen from the table 14, most of the gaps are smaller than in the 3D model. This is
because of the same reason as mentioned earlier. The enclosed loose powder is melted because
of the surrounding heat and that causes the smaller gaps. It also seems that the most accurate gap
widths can be achieved when the gap width is close to 300 µm. The comparison of the gap
widths is presented in figure 29.
40
Figure 29. Gap width comparison between test pieces 2A and 2B
As it can be seen from table 14 and figure 29 the gap widths are more accurate when the gaps are
parallel to the powder spreading direction. All of the gaps are built but the thinnest ones might
not be open all the way. Top sides of the test pieces 2A and 2B are shown in figure 30. The
bottom sides of the gaps can close up when the pieces are sawed off from the building platform.
The bottom sides of the test pieces 2A and 2B are shown in figure 31.
Figure 30. Top sides of the test pieces 2A and 2B
y = 0.8691xR² = 0.9934
y = 0.822xR² = 0.9125
y = xR² = 1
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
0 200 400 600 800 1000 1200
Me
asu
rem
en
ts [
µm
]
Model dimensions [µm]
2A 2B Nominal Linear (2A) Linear (2B) Linear (Nominal)
41
Figure 31. Bottom sides of the test pieces 2A and 2B
As it can be seen from figure 31, sawing off the pieces from building platform will cause the
clogging of the gaps. As it can be seen from figures 30 and 31 the gap building itself is not a
problem with this technology but since the accuracy of the gaps varies widely it would be
necessary to compensate the variation of the gap width somehow.
The third test set included two test pieces where the accuracy of holes with overhangs is studied.
The test pieces included different size holes from 100 µm diameter to 6000 µm diameter. The
challenge of these test pieces was that they were built in the way that the holes created overhangs
which are difficult to build. It was known that the accuracy of the holes is not very good when
they are built in this way. These test pieces were measured from sides A and B. The A and B
sides of the test pieces are presented in figures 32 and 33. The measurement data of test pieces
3A and 3B can be found in appendix.
42
Figure 32. A-sides of test pieces 3A and 3B
Figure 33. B-sides of test pieces 3A and 3B
As it can be observed from figures 32 and 33 the quality of holes is better in test piece 3B than in
test piece 3A. Holes seem to be much more circular in test piece 3B than in 3A. It can be also
seen that the smallest holes are not built since the tops of the holes collapses when built in this
direction. Also the heat melts the powder inside of the holes and the smallest ones are filled with
this powder. But as it can be seen from figures 32 and 33, the smaller diameter holes are built
better in test piece 3B than on 3A. The comparison of average hole diameters between test pieces
3A and 3B are presented in figures 34 and 35.
43
Figure 34. Average hole diameter comparison between test pieces 3A and 3B A-sides
As it can be observed from figure 34, the test piece 3B is more accurate than test piece 3A on A-
side of the pieces. The test piece 3B was oriented in the way that it was 45° angle against the
recoating direction. It seems that the part orientation has big influence on build quality and
accuracy in these kind of features.
y = 0.8258xR² = 0.9562
y = 0.8753xR² = 0.9883
y = xR² = 1
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000 7000
Me
asu
rem
en
ts [
µm
]
Model dimensions [µm]
3A 3B Nominal Linear (3A) Linear (3B) Linear (Nominal)
44
Figure 35. Average hole diameter comparison between test pieces 3A and 3B B-sides
Also the B-sides of the test pieces 3A and 3B differ from the nominal dimensions. As it can be
seen from figure 35, the test piece 3B is more accurate than the test piece 3A. Since the build
parameters are same in both pieces, the only distinctive factor is the build orientation in these
pieces. As mentioned earlier the build orientation is a big factor when these kinds of parts and
features are built. As it can be seen from the figures 34 and 35 the smallest holes that can be built
are close to 500 µm. When building holes in this way that the holes form overhangs it is
impossible to build absolutely round holes without support structures.
9 CONCLUSIONS
Aim and purpose of this study was to clarify the resolution and capabilities of laser additive
manufacturing. It was also important to study how the quality of laser additive manufactured
pieces are evaluated and measured. Purpose of the experimental part was to study the resolution
and quality of stainless steel test pieces manufactured with modern laser additive manufacturing
machine.
In literature review it was concluded that the laser additive manufacturing is very promising
technology for manufacturing parts for various field of industry. The possibility to create parts
y = 0.8082xR² = 0.9717
y = 0.8623xR² = 0.9923
y = xR² = 1
0
1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000 7000
Me
asu
rem
en
ts [
µm
]
Model dimensions[µm]3A 3B Nominal Linear (3A) Linear (3B) Linear (Nominal)
45
with complex geometrical features was considered as one big advantages of this technology. The
accuracy and mechanical properties of manufactured parts are on such level that the build parts
can be used from medical industry to aerospace industry. The evaluation of the build parts are
usually done visually and the dimensional analysis is done with calipers and with microscopy
software. The mechanical properties such as hardness and strength of manufactured pieces are on
a same level or better than bulk materials. It was also seen that the build errors have large level
of repeatability which provides chance to compensate the build parameters. This optimization
will increase the accuracy of manufactured parts. With this optimization, the microstructure of
build parts can also be tuned to fit in desired application.
In experimental part of this thesis it was concluded that the build orientation effects on the build
quality and accuracy of stainless steel test parts. It was shown that smallest and thinnest features
are challenging to build regardless of the build orientation. The dimensional analysis showed that
the parameter optimization is needed in order to get more accurate parts since the accuracy of
manufactured parts varied from the 3D models nominal values. The experimental part showed
also that accuracy and resolution of build parts have improved compared to the examples found
from literature.
10 FURTHER STUDIES
In future it would be very important to develop and optimize the build parameters in order to get
more accurate and precise parts. Also the process development should be done to speed up the
building process. The post processing of the manufactured parts should be also considered as
part of the process development. For example detaching of the parts from the building platform
is a challenge. This could be solved with optimizing the support structures in the way that the
detaching of the parts from building platform would be easier. This would also prevent part
breakage when detached from the building platform.
46
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0502.pdf [referred: 14.11.2011]
Castillo, L. Study about the rapid manufacturing of complex parts of stainless steel and titanium,
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[referred: 14.11.2011]
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material properties in selective laser melting of metals, 2010, ISEM XVI Keynote paper,
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203, Emerald Group Publishing Limited. ISSN: 1355-2546
Appendix I 1 (11)
APPENDIX I
Measurement data of test pieces
Table 1. Wall thickness measurements of test piece 1A
Test piece
1A Model dimensions Meas. 1 Meas. 2 Meas. 3 Meas. 4 Meas. 5 Average Diff. %
wall1 100 253.165 227.848 240.506 329.114 227.848 255.70 155.70
wall2 200 278.481 291.414 253.165 316.456 291.139 286.13 43.07
wall3 300 430.38 392.405 443.038 417.722 417.722 420.25 40.08
wall4 400 506.329 506.329 518.987 493.671 506.329 506.33 26.58
wall5 500 569.62 557.106 594.937 607.595 556.962 577.24 15.45
wall6 600 670.886 658.228 683.544 670.886 670.886 670.89 11.81
wall7 700 772.152 746.943 784.81 746.835 759.494 762.05 8.86
wall8 800 835.443 848.101 873.418 873.418 873.418 860.76 7.59
wall9 900 987.342 1000 987.342 974.684 924.051 974.68 8.30
wall10 1000 1075.949 1101.339 1063.291 1050.633 1050.633 1068.37 6.84
wall11 1100 1177.215 1151.899 1177.215 1151.899 1164.557 1164.56 5.87
wall12 1200 1303.797 1303.797 1240.506 1291.139 1265.823 1281.01 6.75
wall13 1300 1291.139 1316.456 1303.797 1303.859 1278.481 1298.75 -0.10
wall14 1400 1417.722 1430.38 1430.38 1392.405 1379.747 1410.13 0.72
small wall1 100 broken broken broken broken broken broken
small wall2 200 broken broken broken broken broken broken
small wall3 300 broken broken broken broken broken broken
small wall4 400 broken broken broken broken broken broken
small wall5 500 556.962 607.727 569.62 607.595 569.62 582.30 16.46
small wall6 600 658.228 670.886 607.595 683.544 683.544 660.76 10.13
small wall7 700 708.861 645.57 620.253 772.256 696.203 688.63 -1.62
small wall8 800 708.861 784.912 746.835 784.81 797.569 764.60 -4.43
small wall9 900 936.709 886.166 886.166 949.367 898.734 911.43 1.27
Appendix I 2 (11)
Table 2. Wall thickness measurements of test piece 1B
Test piece
1B Model dimensions Meas. 1 Meas. 2 Meas. 3 Meas. 4 Meas. 5 Average Diff. %
wall1 100 166.667 178.487 217.949 282.343 230.769 215.24 115.24
wall2 200 269.231 294.872 269.231 217.949 217.949 253.85 26.92
wall3 300 448.718 397.436 461.538 397.436 410.256 423.08 41.03
wall4 400 525.641 500.00 576.923 577.066 474.359 530.80 32.70
wall5 500 628.205 679.487 641.026 653.846 730.796 666.67 33.33
wall6 600 756.41 769.231 730.769 794.872 769.231 764.10 27.35
wall7 700 820.513 923.077 884.615 961.538 833.432 884.64 26.38
wall8 800 948.718 1102.564 987.179 948.718 910.256 979.49 22.44
wall9 900 935.897 1089.744 1064.103 961.538 1012.821 1012.82 12.54
wall10 1000 1051.282 1179.487 1179.487 1076.923 1115.385 1120.51 12.05
wall11 1100 1179.487 1217.949 1205.128 1230.769 1320.513 1230.77 11.89
wall12 1200 1243.656 1307.692 1320.575 1346.154 1371.795 1317.97 9.83
wall13 1300 1384.615 1397.436 1410.256 1397.495 1410.256 1400.01 7.69
wall14 1400 1500.00 1525.641 1500.00 1487.18 1461.60 1494.88 6.78
small wall1 100 217.949 217.949 243.59 243.59 217.949 228.21 128.21
small wall2 200 294.872 410.256 333.333 307.62 269.536 323.12 61.56
small wall3 300 525.641 705.128 525.641 474.532 551.282 556.44 85.48
small wall4 400 615.385 628.205 602.564 538.462 628.205 602.56 50.64
small wall5 500 717.949 743.59 730.769 628.336 653.846 694.90 38.98
small wall6 600 782.051 730.769 833.432 692.308 717.949 751.30 25.22
small wall7 700 871.795 910.617 935.897 794.975 820.513 866.76 23.82
small wall8 800 1012.821 987.179 987.179 923.077 961.538 974.36 21.79
small wall9 900 1076.923 1141.026 1128.205 1076.923 1064.18 1097.45 21.94
Appendix I 3 (11)
Table 3. Gap width measurements test piece 2A
Gap width in model 2A Meas. 1 Meas. 2 Meas. 3 Meas. 4 Meas. 5 Average Diff. %
100 107.692 61.538 92.308 92.308 107.692 92.31 -7.69
200 169.231 184.615 169.231 215.385 230.769 193.85 -3.08
300 307.692 292.308 276.923 307.692 323.077 301.54 0.51
400 307.692 353.846 338.462 384.615 384.615 353.85 -11.54
500 415.385 446.154 400 430.769 446.154 427.69 -14.46
600 538.462 507.692 492.308 492.308 507.692 507.69 -15.38
700 600 553.846 630.769 584.615 630.769 600.00 -14.29
800 615.385 692.308 676.923 661.538 676.923 664.62 -16.92
900 753.846 784.615 815.385 769.231 784.615 781.54 -13.16
1000 907.823 923.077 892.308 861.538 876.923 892.33 -10.77
Table 4. Gap width measurements test piece 2B
Gap width in model 2B Meas. 1 Meas. 2 Meas. 3 Meas. 4 Meas. 5 Average Diff. %
100 193.548 161.29 145.161 177.419 161.29 167.74 61.29
200 274.194 225.806 225.806 241.935 241.935 241.94 20.97
300 354.839 338.71 322.581 338.71 290.77 329.12 -3.08
400 403.226 370.968 354.839 419.355 370.968 383.87 -7.26
500 500 451.613 435.484 467.742 516.129 474.19 3.23
600 435.484 467.742 419.355 419.355 403.226 429.03 -32.80
700 548.387 532.258 564.516 548.387 548.387 548.39 -21.66
800 661.29 580.645 612.903 612.903 596.774 612.90 -25.40
900 774.194 774.194 693.548 741.935 661.29 729.03 -26.52
1000 870.968 822.581 774.194 822.581 822.581 822.58 -17.74
Appendix I 4 (11)
Table 5. Hole diameter measurements test piece 3A A-side
Hole diameter
in model 3A
A-side
Meas. 1 Meas. 2 Meas. 3 Meas. 4 Average Diff. %
100 0 0 0 0 0 -100
150 0 0 0 0 0 -100
200 0 0 0 0 0 -100
250 0 0 0 0 0 -100
300 0 0 0 0 0 -100
350 0 0 0 0 0 -100
400 0 0 0 0 0 -100
450 0 0 0 0 0 -100
500 0 0 0 0 0 -100
550 0 0 0 0 0 -100
600 0 0 0 0 0 -100
650 253.968 253.968 325.687 339.697 293.33 -54.87
700 206.349 285.714 308.198 206.959 251.81 -64.03
750 222.222 476.19 352.438 371.917 355.69 -52.57
800 253.968 539.638 506.446 250.974 387.76 -51.53
850 142.857 301.587 238.095 273.09 238.91 -71.89
900 269.841 555.556 370.559 498.423 423.59 -52.93
950 444.444 857.143 485.88 508.184 573.91 -39.59
1000 476.19 698.413 742.138 524.05 610.20 -38.98
1050 412.698 730.159 484.532 622.295 562.42 -46.44
1100 666.856 857.143 552.828 539.215 654.01 -40.54
1150 539.683 1000 577.786 573.409 672.72 -41.50
1200 761.905 1031.746 550.086 676.794 755.13 -37.07
1250 603.175 1079.365 784.069 640.649 776.81 -37.85
1300 682.54 1190.476 744.003 776.481 848.38 -34.74
1350 777.778 1206.349 806.405 785.995 894.13 -33.77
1400 761.905 1253.968 886.76 727.047 907.42 -35.18
1450 1000 1333.333 1024.394 864.315 1055.51 -27.21
1500 920.635 1396.825 1010.402 967.603 1073.87 -28.41
1550 1047.619 1396.825 1135.004 1134.116 1178.39 -23.97
1600 1079.365 1492.063 1089.241 1066.804 1181.87 -26.13
1650 1142.857 1507.937 1033.576 1032.844 1179.30 -28.53
1700 1174.603 1603.175 1184.961 1145.06 1276.95 -24.89
1750 1063.492 1619.359 1110.658 1092.013 1221.38 -30.21
1800 1238.095 1634.921 1241.854 1168.15 1320.76 -26.62
1850 1301.587 1619.048 1260.381 1403.394 1396.10 -24.54
1900 1492.063 1761.905 1498.467 1425.482 1544.48 -18.71
1950 1238.095 1777.778 1461.869 1380.952 1464.67 -24.89
2000 1492.063 1904.762 1392.49 1526.453 1578.94 -21.05
Appendix I 5 (11)
2050 1666.667 1936.508 1335.693 1291.97 1557.71 -24.01
2100 1603.175 1920.635 1517.264 1562.102 1650.79 -21.39
2150 1603.175 2015.936 1571.509 1314.397 1626.25 -24.36
2200 1587.302 2079.365 1571.99 1493.835 1683.12 -23.49
2250 1666.667 2126.984 1577.11 1621.846 1748.15 -22.30
2300 1809.524 2222.222 1650.259 1538.045 1805.01 -21.52
2350 1809.524 2206.349 2044.725 1551.501 1903.02 -19.02
2400 1857.143 2269.841 1718.176 1820.49 1916.41 -20.15
2450 1952.381 2317.46 1963.384 1831.185 2016.10 -17.71
2500 2031.746 2365.079 1866.548 1863.305 2031.67 -18.73
2600 2000 2476.19 1949.023 2004.027 2107.31 -18.95
2700 2047.619 2603.175 1910.177 2226.413 2196.85 -18.64
2800 2285.714 2619.048 2588.081 2089.579 2395.61 -14.44
2900 2476.19 2761.905 2396.615 2550.868 2546.39 -12.19
3000 2523.81 2841.27 2410.4 2582.379 2589.46 -13.68
3500 3047.619 3349.206 2796.535 2897.162 3022.63 -13.64
4000 3571.429 3920.635 3670.238 3451.021 3653.33 -8.67
4500 4095.238 4269.841 4006.357 4256.366 4156.95 -7.62
5000 4476.19 4841.27 4760.45 4425.014 4625.73 -7.49
6000 5446.318 5730.159 5325.249 5445.555 5486.82 -8.55
Appendix I 6 (11)
Table 6. Hole diameter measurements test piece 3A B-side
Hole diameter
in model 3A
B-side
Meas. 1 Meas. 2 Meas. 3 Meas. 4 Average Diff. %
100 0 0 0 0 0 -100
150 0 0 0 0 0 -100
200 0 0 0 0 0 -100
250 0 0 0 0 0 -100
300 0 0 0 0 0 -100
350 0 0 0 0 0 -100
400 0 0 0 0 0 -100
450 0 0 0 0 0 -100
500 0 0 0 0 0 -100
550 181.818 303.03 250.802 260.677 249.08 -54.71
600 227.273 257.576 291.051 268.058 260.99 -56.50
650 227.273 439.394 413.556 310.883 347.78 -46.50
700 318.182 378.788 374.215 386.289 364.37 -47.95
750 318.182 439.394 494.692 419.07 417.83 -44.29
800 393.939 454.545 353.716 450.487 413.17 -48.35
850 454.545 666.667 603.403 439.349 540.99 -36.35
900 424.242 636.364 525.956 493.298 519.97 -42.23
950 454.545 772.727 639.423 530.303 599.25 -36.92
1000 515.152 833.333 578.939 429.085 589.13 -41.09
1050 515.152 696.97 634.376 473.384 579.97 -44.76
1100 621.212 893.939 715.177 601.498 707.96 -35.64
1150 636.364 1000 667.355 782.03 771.44 -32.92
1200 712.121 909.217 797.436 653.626 768.10 -35.99
1250 863.636 1030.303 803.602 729.794 856.83 -31.45
1300 772.876 1090.909 854.551 846.453 891.20 -31.45
1350 666.667 1212.121 935.108 999.196 953.27 -29.39
1400 893.939 1272.727 900.082 985.897 1013.16 -27.63
1450 1015.152 1287.968 1103.983 932.157 1084.82 -25.19
1500 969.697 1318.182 985.897 1007.091 1070.22 -28.65
1550 954.545 1348.485 1073.301 1045.894 1105.56 -28.67
1600 1106.061 1424.242 1181.624 1093.011 1201.23 -24.92
1650 1075.758 1348.485 1129.067 1200.704 1188.50 -27.97
1700 1060.606 1469.697 1267.123 1157.282 1238.68 -27.14
Appendix I 7 (11)
1750 1196.97 1530.303 1313.384 1167.847 1302.13 -25.59
1800 1242.424 1606.061 1243.532 1307.252 1349.82 -25.01
1850 1257.576 1590.909 1332.817 1328.676 1377.49 -25.54
1900 1318.182 1651.515 1235.847 1493.866 1424.85 -25.01
1950 1287.879 1651.515 1552.273 1414.863 1476.63 -24.28
2000 1439.394 1742.424 1492.328 1574.956 1562.28 -21.89
2050 1424.242 1681.818 1459.587 1530.978 1524.16 -25.65
2100 1484.848 1893.939 1530.978 1566.552 1619.08 -22.90
2150 1621.212 1848.485 1649.916 1628.488 1687.03 -21.53
2200 1575.758 1939.394 1662.322 1565.526 1685.75 -23.38
2250 1590.909 1969.697 1651.168 1639.237 1712.75 -23.88
2300 1696.97 2090.909 1815.971 1668.388 1818.06 -20.95
2350 1712.121 2166.667 1934.297 1834.585 1911.92 -18.64
2400 1772.727 2121.212 1778.997 2017.201 1922.53 -19.89
2450 1833.333 2121.212 1765.2 2013.784 1933.38 -21.09
2500 1848.733 2045.455 1872.73 1912.935 1919.96 -23.20
2600 2015.152 2212.121 1946.542 2004.185 2044.50 -21.37
2700 2045.511 2439.441 2039.666 2113.894 2159.63 -20.01
2800 2151.729 2545.455 2304.077 2343.543 2336.20 -16.56
2900 2257.576 2560.606 2392.309 2282.655 2373.29 -18.16
3000 2318.182 2727.273 2476.01 2368.924 2472.60 -17.58
3500 2848.485 3166.667 2872.921 2861.551 2937.41 -16.07
4000 3242.424 3681.818 3392.316 3257.259 3393.45 -15.16
4500 3818.182 4151.515 4072.405 3868.862 3977.74 -11.61
5000 4196.97 4590.909 4358.688 4269.449 4354.00 -12.92
6000 5303.03 5575.758 5479.153 5272.314 5407.56 -9.87
Appendix I 8 (11)
Table 7. Hole diameter measurements test piece 3B A-side
Hole diameter
in model 3B
A-side
Meas. 1 Meas. 2 Meas. 3 Meas. 4 Average Diff. %
100 0 0 0 0 0.00 -100
150 0 0 0 0 0.00 -100
200 0 0 0 0 0.00 -100
250 0 0 0 0 0.00 -100
300 0 0 0 0 0.00 -100
350 0 0 0 0 0.00 -100
400 0 0 0 0 0.00 -100
450 184.615 200 305.376 218.656 227.16 -49.52
500 230.769 430.796 415.669 282.843 340.02 -32.00
550 246.154 430.769 298.715 446.154 355.45 -35.37
600 307.692 384.615 478.657 447.214 404.54 -32.58
650 430.769 461.538 569.439 500.414 490.54 -24.53
700 430.769 461.538 490.622 526.235 477.29 -31.82
750 446.154 538.462 589.052 534.048 526.93 -29.74
800 538.462 600 697.587 632.456 617.13 -22.86
850 569.231 661.538 696.228 784.465 677.87 -20.25
900 692.308 707.692 827.915 728.945 739.22 -17.87
950 692.308 769.231 871.372 807.656 785.14 -17.35
1000 600 815.385 862.088 829.344 776.70 -22.33
1050 723.077 815.385 870.557 944.62 838.41 -20.15
1100 738.462 892.308 866.586 861.126 839.62 -23.67
1150 969.231 953.846 1001.774 979.071 975.98 -15.13
1200 876.923 1046.154 1028.47 957.314 977.22 -18.57
1250 984.615 1030.769 1057.965 1079.667 1038.25 -16.94
1300 923.077 953.846 1076.923 1105.232 1014.77 -21.94
1350 1076.923 1107.692 178.104 1153.128 878.96 -34.89
1400 1169.231 1200 1198.421 1229.326 1199.24 -14.34
1450 1061.538 1276.923 1268.648 1230.481 1209.40 -16.59
1500 1046.154 1307.692 1295.418 1251.461 1225.18 -18.32
1550 1092.308 1307.692 1332.436 1371.39 1275.96 -17.68
1600 1307.692 1307.692 1405.4 1338.462 1339.81 -16.26
1650 1276.923 1430.769 1434.404 1426.13 1392.06 -15.63
1700 1323.077 1446.154 1520.9 1479.645 1442.44 -15.15
Appendix I 9 (11)
1750 1430.769 1507.692 1562.05 1589.611 1522.53 -13.00
1800 1446.154 1569.231 1588.867 1577.43 1545.42 -14.14
1850 1553.846 1630.769 1692.098 1667.298 1636.00 -11.57
1900 1415.385 1661.583 1645.579 1647.016 1592.39 -16.19
1950 1492.308 1692.308 1725.548 1690.419 1650.15 -15.38
2000 1569.231 1723.077 1747.695 1740.571 1695.14 -15.24
2050 1600 1738.462 1763.536 1755.532 1714.38 -16.37
2100 1676.923 1800 1831.028 1773.24 1770.30 -15.70
2150 1753.846 1830.769 1873.136 1784.615 1810.59 -15.79
2200 1846.154 1907.692 1882.023 1860.267 1874.03 -14.82
2250 1800 1969.231 1969.772 1982.885 1930.47 -14.20
2300 1815.385 1984.615 2056.768 2078.518 1983.82 -13.75
2350 1938.462 2015.385 2143.105 2045.633 2035.65 -13.38
2400 1923.077 2107.692 2157.634 2002.129 2047.63 -14.68
2450 2015.385 2123.077 2153.022 2164.862 2114.09 -13.71
2500 2061.538 2200 2198.439 2227.796 2171.94 -13.12
2600 2169.231 2292.308 2276.767 2295.403 2258.43 -13.14
2700 2123.077 2446.154 2462.019 2470.177 2375.36 -12.02
2800 2353.846 2523.077 2519.745 2443.007 2459.92 -12.15
2900 2461.538 2569.231 2654.459 2618.189 2575.85 -11.18
3000 2584.615 2707.692 2703.493 2683.282 2669.77 -11.01
3500 2923.077 3200 3253.582 3162.278 3134.73 -10.44
4000 3430.769 3630.769 3650.176 3693.109 3601.21 -9.97
4500 3923.077 4169.231 4305.631 4355.368 4188.33 -6.93
5000 4400 4584.615 4685.064 4553.534 4555.80 -8.88
6000 5384.615 5476.923 5516.967 5547.706 5481.55 -8.64
Appendix I 10 (11)
Table 8. Hole diameter measurements test piece 3B B-side
Hole diameter
in model 3B
B-side
Meas. 1 Meas. 2 Meas. 3 Meas. 4 Average Diff. %
100 0 0 0 0 0 -100
150 0 0 0 0 0 -100
200 0 0 0 0 0 -100
250 0 0 0 0 0 -100
300 0 0 0 0 0 -100
350 0 0 0 0 0 -100
400 0 0 0 0 0 -100
450 212.121 393.939 375.131 400.289 345.37 -23.25
500 242.424 393.939 257.576 366.778 315.18 -36.96
550 303.03 530.303 556.29 483.188 468.20 -14.87
600 333.333 469.697 454.545 567.929 456.38 -23.94
650 454.546 530.303 589.353 589.353 540.89 -16.79
700 530.303 545.455 580.127 601.498 564.35 -19.38
750 515.152 590.909 643.181 655.73 601.24 -19.83
800 515.374 530.303 632.201 664.252 585.53 -26.81
850 545.455 590.909 691.015 717.9 636.32 -25.14
900 712.121 696.97 710.023 760.751 719.97 -20.00
950 712.121 787.879 797.436 803.602 775.26 -18.39
1000 757.576 839.939 870.124 896.456 841.02 -15.90
1050 787.879 893.939 897.016 899.954 869.70 -17.17
1100 803.03 863.636 894.453 943.783 876.23 -20.34
1150 893.939 969.697 972.77 964.237 950.16 -17.38
1200 969.697 1000 1032.084 1008.003 1002.45 -16.46
1250 954.545 1060.606 1009.141 1050.821 1018.78 -18.50
1300 1030.303 1075.758 1104.815 1093.011 1075.97 -17.23
1350 1075.758 1060.606 1180.263 1103.983 1105.15 -18.14
1400 1090.909 1166.667 1211.837 1157.282 1156.67 -17.38
1450 1166.667 1333.333 1340.631 1242.794 1270.86 -12.35
1500 1242.424 1348.485 1342.684 1285.827 1304.86 -13.01
1550 1257.576 1318.182 1406.808 1341.316 1330.97 -14.13
1600 1272.727 1348.485 1384.852 1340.288 1336.59 -16.46
1650 1318.182 1393.939 1453.045 1371.359 1384.13 -16.11
1700 1318.182 1424.242 1472.74 1396.901 1403.02 -17.47
Appendix I 11 (11)
1750 1409.091 1484.848 1510.675 1490.173 1473.70 -15.79
1800 1454.545 1515.152 1525.119 1512.498 1501.83 -16.57
1850 1500 1515.152 1609.274 1532.402 1539.21 -16.80
1900 1469.697 1681.818 1736.684 1660.664 1637.22 -13.83
1950 1515.152 1712.121 1643.433 1666.46 1634.29 -16.19
2000 1651.515 1712.121 1769.357 1706.211 1709.80 -14.51
2050 1696.97 1772.727 1800.737 1692.906 1740.84 -15.08
2100 1727.273 1803.03 1878.605 1810.907 1804.95 -14.05
2150 1803.03 1803.03 1850.719 1803.094 1814.97 -15.58
2200 1712.121 1863.636 1974.444 1819.759 1842.49 -16.25
2250 1863.636 1969.697 1976.039 1897.088 1926.62 -14.37
2300 1818.182 1939.394 2017.03 1886.713 1915.33 -16.72
2350 1939.394 2075.758 2103.661 2057.038 2043.96 -13.02
2400 2015.152 2151.515 2176.973 2058.042 2100.42 -12.48
2450 2045.455 2151.515 2188.227 2164.6 2137.45 -12.76
2500 1909.091 2181.818 2212.329 2153.701 2114.23 -15.43
2600 2030.303 2242.424 2281.398 2228.87 2195.75 -15.55
2700 2121.212 2287.897 2392.309 2314.267 2278.92 -15.60
2800 2318.182 2454.545 2562.802 2528.806 2466.08 -11.93
2900 2363.636 2575.758 2642.626 2614.504 2549.13 -12.10
3000 2590.909 2666.667 2691.346 2680.577 2657.37 -11.42
3500 2803.03 3090.909 3170.832 3053.866 3029.66 -13.44
4000 3393.973 3484.848 3647.773 3369.637 3474.06 -13.15
4500 3863.636 3969.697 4238.797 3903.567 3993.92 -11.25
5000 4378.788 4348.485 4508.461 4470.519 4426.56 -11.47
6000 5228.678 5258.362 5433.144 5368.107 5322.07 -11.30
Appendix II 1 (10)
APPENDIX II
Diagrams of measurement results
Figure 1. Wall thickness measurements of test piece 1A
Appendix II 2 (10)
Figure 2. Wall thickness measurements test piece 1A small walls
Appendix II 3 (10)
Figure 3. Wall thickness measurements test piece 1B
Appendix II 4 (10)
Figure 4. Wall thickness measurements test piece 1B small walls
Appendix II 5 (10)
Figure 5. Gap width measurements test piece 2A
Appendix II 6 (10)
Figure 6. Gap width measurements test piece 2B
Appendix II 7 (10)
Figure 7. Hole diameter measurements test piece 3A A-side
Appendix II 8 (10)
Figure 8. Hole diameter measurements test piece 3A B-side
Appendix II 9 (10)
Figure 9. Hole diameter measurements test piece 3B A-side
Appendix II 10 (10)
Figure 10. Hole diameter measurements test piece 3B B-side
