Laser Metal Deposition (LiM 2017)

Development of a High-speed and High-resolution 3D Printer by Using Laser Metal Deposition Technology
Shiomi, Yasutomo; Ohno, Hiroshi; Okada, Naotada; Fujimaki, Shimpei

A high performance LMD (Laser Metal Deposition) 3D printer prototype is presented here, demonstrating a building
speed over 350 cc/ h, a build width as small as 0.3 mm, an accuracy of +/- 30 um, and a maximum building size of 300
mm x 300 mm x 100 mm. The prototype consists of a 6 kW fiber laser, a powder focusing nozzle, an inert gas chamber, a
metal powder feeding system with inert gas, and a laser polishing system. A 6 kW fiber laser enable higher building
speed than the conventional powder bed fusion. An axial nozzle concentrating the powder stream with a diameter as
small as 0.7 mm can improve the accuracy. Inert gas can reduce a content of oxygen in the chamber to less than 50 ppm.
Multi-layer parts consisting of multi-materials were built by switching power materials with a metal powder feeding
system. The surface of built parts with a roughness, Ra, of 14.1 um was improved to 3.9 um with the laser polishing
system. The parts built from Stainless Steel 316L powder satisfied the mechanical properties of JIS G4304.

Keywords: Additive Manufacturing, Laser Metal Deposition ;


Temperature generation of different travel path strategies to build layers using laser metal deposition
Petrat, Torsten; Winterkorn, Rene; Graf, Benjamin; Gumenyuk, Andrey; Rethmeier, Michael

Laser Metal Deposition offers the chance to build near net shape parts. The temperature evolution within the process has
an influence on track and layer geometries. There are special travel path strategies required to produce near net shape
components and reduce shape deviation resulting of error propagation.

This paper deals with the temperature progression of individual layers and the maximum heating of deeper substrate
regions. Spiral and zig-zag strategies are examined. The investigations are carried out using S235JR as substrate and 316L as
powder material. The influence of different strategies on temperature evolution is discussed.
The results from the experiments show that various production strategies are associated with different temperature fields.
Furthermore, the extent of the temperature variations of layer strategies and layer position are strongly dependent on the
production direction. These results demonstrate the importance of developing suitable build-up strategies for parts of
complex shape to ensure a stable process with constant temperature as well as even layers.

Additive Manufacturing; Temperature behavior; Laser Metal Deposition; Stainless Steel, 316L, edge effects


Performance of hot forging tools built by laser metal deposition of hot work tool steel X37CrMoV5-1
Junker, Daniel; Hentschel, Oliver; Ralph, Schramme; Schmidt, Michael; Merklein, Marion

In industry the variety of products is increasing and product life cycles are getting shorter. For parts made by forging
processes this trend leads to very high prizes, as the tool costs have to be assimilated with only few parts. To reduce the
tool costs new, flexible processes have to be established in tool manufacturing. Laser based additive manufacturing is
noted for its high flexibility and especially Laser Metal Deposition (LMD) process, which is already used for coating and
repairing of forming tools, would be qualified for the production of forging tools. Within first investigations the hot work
tool steel X37CrMoV5-1 (DIN 1.2343) was successfully processed with LMD to generate 3D structures without cracks and
a relative density of 99.9%.
In this work an additive manufactured forging tool for a fork joint was designed using the hot work steel X37CrMoV5-1.
The tool is a hybrid part with a conventional manufactured base part and a forming element added by LMD. The
mechanical properties of additive manufactured specimen are analysed by compression tests and are compared to
conventional manufactured specimen. Afterwards the occurring stresses during forging are analysed by a numerical
simulation. The designed hybrid tool is manufactured by LMD and finished by machining. Finally the tools are tested
under serial production conditions with a workpiece temperature of 900 °C. For quality assurance the produced parts
are checked randomly to evaluate the accuracy of the forging process.

Keywords: Tool Manufacturing; Laser Metal Deposition; Additive Manufacturin


Laser metal deposition of magnesium alloys
Enz, Josephin; Konovalova, Anna; Schultz, Marco; Riekehr, Stefan; Ventzke, Volker; Kashaev, Nikolai

Laser additive manufacturing (LAM) is a fast growing technology for the manufacture of metallic components. Although
the activities in the area of steel, titanium and aluminium are manifold, magnesium is practically not utilized for this
technology. The reason for this disregard lies in the problems of easy flammability of magnesium powder and the
extensive remedial measures for powder handling. By using magnesium wire for laser metal deposition (LMD) these
difficulties can be avoided. Moreover, a higher utilisation of the material can be realized. In the present study relevant
influencing factors on the LMD process as well as the peculiarities for processing magnesium alloys are identified. The
quality of the resulting components is assessed by non-destructive testing and the determination of microstructural and
mechanical characteristics. Enabling the processing of magnesium by LAM affords new prospects for its application in
the automotive, aircraft and medical industry in matters of design and properties.

Keywords: laser additive manufacturing; laser metal deposition; wire; magnesium alloy; characterisation


Characterization and optimization of residual stress state, geometrical accuracy and productivity for laser metal deposition of complex three-dimensional titanium parts
Möller, Mauritz; Scholl, Christoph; Prakash, Vishnuu; Emmelmann, Claus

Laser Metal Deposition (LMD) connected with milling processes offers the opportunity for an efficient, resource conserving manufacturing for large structural components made from Ti-6Al-4V. Conventional manufacturing routes as for example in the aerospace industry come along with up to 95% of waste material that has to be machined from the bulk material. LMD is an additive manufacturing process building parts based on a nozzle-fed powder by laser solidification. This technology offers unique advantages for the production of near net-shape parts. In contrast to the powder bed-based technologies it also provides a higher productivity rate. Today LMD lacks reproducible process strategies manufacturing large parts in narrow tolerances and predictable residual stress states. Although Ti-6Al-4V is one of the most widely used materials in additive manufacturing with LMD, the occurrence of residual stresses is still a common cause for failure of parts or even the entire build job. To reduce this effort, in this paper first the actual state of the anisotropic residual stress states is investigated for LMD-manufactured parts to obtain thorough knowledge of the process and shape-related dependencies with the quality aims. Based on these results an in-depth study for the influence of different exposure patterns on the residual stresses is shown. A simulation-based approach is chosen to develop a strategy for further optimization of the exposure. For validation, Crack Compliance Method has successfully been used in first experiments to determine the local distribution of residual stresses for several geometries - consecutively leading to a higher effort in the manufacturing-process development for such parts. The gathered knowledge is applied to an 2.5 D prototype application and a 3 D complex hybrid aerospace application.

Keywords: laser metal deposition; residual stresses; crack compliance method; geometrical accuracy; anisotropic properties; titanium


Laser metal deposition of Ti-6Al-4V structures: new building strategy for a decreased shape deviation and its influence on the microstructure and mechanical properties
Heilemann, Markus; Möller, Mauritz; Emmelmann, Claus; Burkhardt, Irmela; Riekehr, Stefan; Ventzke, Volker; Kashaev, Nikolai; Enz, Josephin

The laser metal deposition (LMD) process is used to increase the productivity rate in the field of laser additive
manufacturing. Large structural Ti-6Al-4V components can be manufactured resource efficiently with this approach. In
contrast, conventional manufacturing processes machine up to 95% from the bulk material to produce parts for the
aerospace industry, as described by Peters et al., 2003.
Compared to the powder bed based additive manufacturing the LMD process generates a local material deposition by
feeding the powder directly to the substrate. On top of the surface, the laser beam will liquefy the additional material.
Consequently a single track is deposited, which can be extended to a surface or 3D-structures.
To qualify the LMD process for an economic industrial use, it is necessary to understand the physical phenomena during
the building process. Especially for high wall structures, the thermal boundaries vary with the building height and
therefore the process lacks in reproducibility and quality . In this paper, a new approach of adapted process parameters
to the thermal conditions during the building process is presented. The laser power and processing speed vary for every
layer until a stable building rate is achieved. The aim is to narrow the geometric tolerances of the additive manufactured
structures. In addition, the influence of the building strategy on the resulting microstructure is determined.

Keywords: laser metal deposition ; additive manufacturing ; titanium ; building strategy ; microstructure.


Blue direct diode laser induced pure copper layer formation on stainless steel plate for reduction of heat affected zone
Sengoku, Masanori; Tsukamoto, Masahiro; Asano, Kohei; Sato, Yuji; Higashino, Ritsuko; Funada, Yoshinori; Yoshida, Minoru; Abe, Nobuyuki

A pure copper layer was formed on a stainless steel substrate with blue direct diode laser at maximum output power of about 100W. The six lasers were combined by a focusing optical system at a focal point of 400 μm. At the same time, the pure copper powder, which had a particle size of 30 μm φ, was supplied on the focus point from a center nozzle. The powders absorbed the laser beam, and then melts and solidifies were occurred on the substrate. The substrate was
placed on the XYZ stage in order to make the layer formation shape freely. After the laser irradiation, the Cu coated sample was cut with a micro-cutter to observe a cross section with an optical microscope in order to evaluate the thickness and heat affected zone. As the results, coating speed was obtained to 0.15 mm3/s on stainless steel 304 substrate at the laser power density 74 kW/cm2, a powder supply of 17mg/s and scanning speed of 5.0 mm/s.

Keywords: Blue direct diode laser.


Design recommendations for laser metal deposition of thin wall structures in TiAl6V4
Zapf, Hannes; Bendig, Niels; Möller, Mauritz; Emmelmann, Claus

Today, the use of laser metal deposition (LMD) for industrial applications is increasing tremendously. Due to a high
freedom in design, it offers a superior potential for weight saving in lightweight applications with higher build-up rates in
comparison to the powder bed technology. However, most design engineers are used to design parts for conventional
manufacturing methods, such as milling and casting, and often only have limited experience in designing products for a
metal deposition process. The absence of comprehensive design guidelines is therefore limiting the further usage and
distribution of LMD. In this paper, experimental investigations on the influence of thin walls and varied process
strategies are presented. Thin walls have been identified as typical basic shapes used in lightweight design and were
built in LMD at different orientations and overhanging angles to determine the process limits. Additionally, their
geometrical accuracy is measured by laser triangulations to compare the walls shape to the target geometry. From the
results of the experiments, an outlook on design guidelines for laser metal deposition is given. For selected structures a
recommendation for an optimized building strategy is shown and the underlying process restrictions are mentioned.

Keywords: Laser metal deposition; Ti-Al6-V4; design recommendations; thin walls; tilted walls


High speed laser metal deposition process: development of technology and equipment using robotic systems
Turichin, Gleb Andreevich; Klimova-Korsmik, Olga; Zemlyakov, Eugeniy; Babkin, Konstantin; Valdaitseva, Ekaterina

Intensive progress of additive technologies leads to improvement of the developed equipment. Such developments are
only possible if there are serious theoretical and technological researches. In recent years many theoretical and
experimental articles, devoted to additive technologies and their applications has been published. The paper presents
results of theoretical and experimental researches devoted to stability of products formation from different metallic
alloys with complex geometry form and the development of equipment using robotic systems. Designed equipment uses
technology of high-speed laser metal deposition process.

Keywords: additive technology, high-speed laser metal deposition, robotic systems, heterophasic process, mechanical properties,
powder, metal alloys, ultrafine structure.


Adapted approach of the product development process for hybrid manufactured parts
Ewald, Ake; Möller, Mauritz; Schlattmann, Josef

The researched hybrid manufacturing process presents a solution in the field of tension between pure additive
manufacturing processes like selective laser melting and pure subtractive manufacturing processes like milling or
turning. With the goal to further reduce time and costs, a product development process has been developed, where the
advantages of the laser metal deposition (LMD) process have been used to optimize the part structure towards a
minimum of used resources.
LMD is a layer-by-layer additive manufacturing process building parts based on a nozzle-fed powder by laser assisted
solidification. The LMD technology offers unique advantages for the production of near net-shape parts. In most cases
near net-shape parts require a turning or milling process in order to get to the final shape. The LMD is the perfect
partner in a hybrid manufacturing process using additive and subtractive processes in synergy.
The researched hybrid manufacturing process is manufacturing a part by partly a raw stock and additive material added
by the LMD process. During or after this process, a subtractive milling process is commonly used to finish the part
towards the final contour.
The product development process for additive manufacturing usually contains the steps of the part design in CAD, the
slicing and the manufacturing of the part. In the hybrid manufacturing process, the design step needs an additional
optimization of the ratio between the raw stock and the LMD added material after the part design in CAD and an
optional FEM optimization. The three design steps CAD design, FEM optimization and manufacturing optimization have
an influence on each other, thus have to be processed in an iterative way.

Keywords: LMD; additive manufacturing; hybrid manufacturing; product development process