· · 208 The status and research progress of selective laser melting additive manufacturing Yongqiang Yang, Fan Fu, Di Wang, Changhui Song ( School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510641, China) Abstract: With the development and research progress of additive manufacturing technology, direct manufacturing of metal functional parts has become the research hotspot, and the application field has also expanded to aerospace, biomedicine, automobile and mold. This paper introduces the principle, characteristics, application and domestic research status of SLM technology,elaborates the research achievements of SLM technology in South China University of Technology and the application of the technology in various fields. Material, molding size, precision, performance and the application of SLM technology in depth have been discussed, and analyzed. Key words: additive manufacturing; selective laser melting; powder material; applications DOI: 10.7512/ j.issn.1001-2303.2017.13.26 Prof. Yongqiang Yang Email: [email protected]0 Introduction With the rapid development of additive manufacturing(AM) technology, the mode of production and lifestyle formed since the industrial revolution are gradually changing. As a strategic emerging industry, AM technology has attracted huge attention from the United States, Germany and other developed countries and these countries promote the technology actively. In 2012, the US President Barack Obama issued a statement of State of the Union speech giving strong support to 3D printing which also named AM, then it became a hot spot among the world's technology industry. In recent years, owing to personalization, customization combined with digital network, AM industry continues to develop and expand [1] . Up to now, several direct manufacturing methods have been developed, like fused deposition modeling (FDM), electron beam fusion (EBM), selective laser melting ( SLM ), selective laser sintering ( SLS ), and digital light processing (DLP) [2] . Among them, SLM direct manufacturing technology which is the most cutting-edge and most potential technology in the AM system, leads the development direction of advanced manufacturing technology. SLM is beneficial to achieve the new concept "near net forming" for material processing and is particularly suitable for manufacturing metal parts with complex structures to meet limited order requirements or special customization requirements in biomedical areas, defense, aerospace [3] , such as satellite applications, in particular, radio-frequency components [4] . With the continuous upgrading of the manufacturing industry, the development of science and technology and the demand for application promotion, the utilize of SLM to direct manufacture functional parts [5] has become the main direction of its development. 1 The introduction of SLM additive manufacturing technology SLM is a kind of additive manufacturing (3D printing ), adapting the principle of rapid prototyping. That is, designing the three-dimensional parts of the solid model on computer through software first, and then the data will be sliced and the contour data of each section of the three-dimensional model will be obtained through dedicated software [6] . The data will be imported into the rapid prototyping equipment. The equipment then control the laser beam to selectively melt metal powder of each layer and gradually stack into three-dimensional metal parts according to these contour data. The laser beam rapidly melts the metal powder and obtains a continuous fused channel, which can manufacture metal parts in almost any shape, with complete metallurgical bonding, high precision and density. The process of SLM is shown in Figure 1 [7] , in the molding process, the right side powder cylinder up a set value, the powder roller moves to the left and the left Yongqiang Yang, professor, director of the Department of Electrical and Mechanical Engineering, School of Mechanical and Automotive Engineering, South China University of Technology. He has been done the research work in the field of laser additive manufacturing technology, laser processing and welding technology, publishing more than 240 academic papers.
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· ·208
The status and research progress of selectivelaser melting additive manufacturing
Yongqiang Yang, Fan Fu, Di Wang, Changhui Song
(School of Mechanical and Automotive Engineering, South China University
of Technology, Guangzhou 510641, China)
Abstract: With the development and research progress of additive
manufacturing technology, direct manufacturing of metal functional
parts has become the research hotspot, and the application field has
also expanded to aerospace, biomedicine, automobile and mold.
This paper introduces the principle, characteristics, application and
domestic research status of SLM technology,elaborates the research
achievements of SLM technology in South China University of Technology
and the application of the technology in various fields. Material, molding
size, precision, performance and the application of SLM technology in
0 IntroductionWith the rapid development of additive manufacturing(AM)
technology, the mode of production and lifestyle formed since the
industrial revolution are gradually changing. As a strategic emerging
industry, AM technology has attracted huge attention from the United
States, Germany and other developed countries and these countries
promote the technology actively. In 2012, the US President Barack
Obama issued a statement of State of the Union speech giving strong
support to 3D printing which also named AM, then it became a hot
spot among the world's technology industry. In recent years, owing
to personalization, customization combined with digital network, AM
industry continues to develop and expand [1]. Up to now, several direct
manufacturing methods have been developed, like fused deposition
modeling (FDM), electron beam fusion (EBM), selective laser melting
(SLM), selective laser sintering (SLS), and digital light processing
(DLP) [2]. Among them, SLM direct manufacturing technology which
is the most cutting-edge and most potential technology in the AM
system, leads the development direction of advanced manufacturing
technology. SLM is beneficial to achieve the new concept "near
net forming" for material processing and is particularly suitable for
manufacturing metal parts with complex structures to meet limited
order requirements or special customization requirements in biomedical
areas, defense, aerospace [3], such as satellite applications, in particular,
radio-frequency components [4]. With the continuous upgrading of the
manufacturing industry, the development of science and technology
and the demand for application promotion, the utilize of SLM to direct
manufacture functional parts [5] has become the main direction of its
development.
1 The introduction of SLM additive manufacturing technologySLM is a kind of additive manufacturing (3D printing), adapting the
principle of rapid prototyping. That is, designing the three-dimensional
parts of the solid model on computer through software first, and then
the data will be sliced and the contour data of each section of the
three-dimensional model will be obtained through dedicated software[6].
The data will be imported into the rapid prototyping equipment.
The equipment then control the laser beam to selectively melt metal
powder of each layer and gradually stack into three-dimensional metal
parts according to these contour data. The laser beam rapidly melts
the metal powder and obtains a continuous fused channel, which
can manufacture metal parts in almost any shape, with complete
metallurgical bonding, high precision and density. The process of SLM
is shown in Figure 1[7], in the molding process, the right side powder
cylinder up a set value, the powder roller moves to the left and the left
Yongqiang Yang, professor, director of the Department of Electrical and Mechanical Engineering, School of Mechanical and Automotive Engineering, South China University of Technology.
He has been done the research work in the field of laser additive manufacturing technology, laser processing and welding technology, publishing more than 240 academic papers.
· ·209
side molding cylinder plate coated with a layer of uniform powder.
Then the metal powder layer melted by SLM, the three-dimensional
metal parts formed layer by layer. The entire process is carried out in
a molding chamber with an inert gas protection to prevent the metal
from reacting with other gases at high temperatures.
Fig. 1 Schematic diagram of SLM molding
The existing powder coating device in the SLM equipment show
high applicability to Fe-based, Ni-based, Ti-based and other types
metal powder materials, but the applicability to Al-alloy powder is low,
resulting in its SLM molding process is difficult to proceed smoothly.
2 The research status of SLM technology in ChinaIn recent years, SLM technology and industry developed rapidly,
new materials and process continue to emerge. The application of
SLM has been extended to aerospace, automobile manufacturing, bio-
medical, jewelry and other industries. In the past few years, aircraft
manufacturing and medical applications are the fastest growing areas
of SLM, industrial output maintain a large increase every year, more and
more enterprises engaged in. The research on the theory and process
of SLM for metal parts is relatively early abroad and a number of mature
SLM equipment manufacturers have emerged including EOS, MCP,
Concept Laser, SLM Solutions and American 3D company.
Domestic research on SLM start relatively late, at the beginning of
1990s, Xi'an Jiao Tong University, Huazhong University of Science and
Technology, Tsinghua University, Beijing Longyuan company has made
significant progress in molding equipment, typical software, materials
and other aspects of SLM research and industrialization under the
support of the State Ministry of science and technology. Subsequently,
many domestic universities and research institutions have carried
out relevant research, such as Northwestern Polytechnical University,
Beihang University, South China University of Technology(SCUT) and
other units.
In the research of SLM on light alloy such as titanium alloy and
Aluminum Alloy. The Gu Dongdong team of Nanjing University of
Aeronautics and Astronautics has systematically developed Ti-based
metal element with high precision, complex structure, net molding,
shape and property control [8]. Northwest University of Technology
Huang Weidong team made an in-depth study on AM process of high-
performance metal in the field of aviation and has successfully repaired
aero engine blades, some developed metal parts as shown in Figure 2 [9].
Fig. 2 Complex parts developed by Northwest University of Technology
The Beijing University of Aeronautics and Astronautics Wang
Huaming team long-term commit to the research on laser direct
manufacturing process, internal quality control and application of large-
scale titanium alloy structure, the manufacturing process for high-
performance metal components has been successfully used in the
development of a variety of domestic large aircraft [10].
Lu Bingheng team of the Xi'an Jiao Tong University made a deep
research on laser AM process of titanium alloy. Based on powder
focusing control, combined scanning mode, layer-by-layer power
control and other molding process basis, the complex titanium alloy
whole turbine blade sample was molded out [11]. Yang Yongqiang team
of SCUT focus on the research and development of SLM equipment
and has developed DiMetal-240, DiMetal-280, DiMetal-100 and other
types SLM equipment [12], as shown in Figure 3.
(a) DiMetal —100 (b) DiMetal —280
Fig. 3 Two SLM equipments developed by SCUT
3 The application status of SLM technology in ChinaIn recent years, as SLM technology continues to become mature and
commercial, its application area become more and more broad. SLM
has high molding precision and excellent comprehensive mechanical
properties, can directly mold precise metal parts to meet practical
engineering applications. So it has important applications in many fields,
· ·210
such as biomedicine, mold manufacturing, automobile, jewelry, aviation
and spaceflight.
3.1 The application of SLM in biomedicine
The application of AM technology in domestic medical industry
began in the late 1980s, initially mainly for the rapid manufacturing
of 3D medical models. In recent years, with the development of AM
technology and the growth of precise and personalized medical
needs. Additive manufactured biomaterials such as 316L stainless steel,
titanium-6 aluminum-4 vanadium (Ti6Al4V) and cobalt-chromium
(CoCr) are widely used in clinical practice [13]. The application of SLM
in medical industry has continued to grow and gradually use for direct
manufacturing Orthopedic implants, customized prostheses and
prostheses [14]. There are also some domestic enterprises that carry out
research and explorations in SLM for biomedicine, such as Changzhou
Watson medical equipment, Trauson medical equipment, Guangzhou
Medprin regenerative medical technologies Co., Ltd, Shenzhen KTJ and
other enterprises. Changzhou Watson Medical Devices has developed
a full range of orthopedic products for different regions (especially for
our Asian human body). Including the series of spine, trauma series
(stainless steel and titanium alloy plate series, bone screw series and
intramedullary nail series), a new series of locking plate, artificial joints
and prosthesis series of orthopedic products.
( a ) Customized orthopedic implant ( b ) Anterior cervical plate system
Fig. 4 Two SLM medical products developed by Watson
Dongguan EONTEC is committed to the development of
biodegradable magnesium alloy orthopedic implants products, and is
expected to achieve the clinical application of degradable magnesium
alloy in short term. Degradable magnesium alloy which is regarded as
the new generation of biomedical materials with many advantages
over traditional materials, in line with the development trend of
biomedical materials, can be used to develop new medical devices with
unique performance. its clinical application will be a milestone in the
development of biomedical materials.
Fig. 5 Biodegradable Mg-Alloy implant developed by Eontec
3.2 The application of SLM in mold
From a global perspective, the production of molds mainly
concentrated in China, Japan, the United States and Germany. The
quantity of mold enterprise in China is up to 20 000. At present,
the application of SLM technology in the field of mold is mainly
concentrated in the production of high-end metal mold with cooling
channel [15], which has obvious effect on improving the manufacturing
capability of high-end mold [16]. Dongjiang mold, Dongguan
RATC, Shenzhen Sunshine, Shanghai Risemold Laser and other
Chinese companies have implied SLM technology maturely to mold
manufacturing. Dongjiang mold use SLM process to manufacture
conformal waterway inside the mold, which greatly enhance the mold
cooling efficiency. The injection cycle increased by 21.7%, injection cost
decreased 110000RMB and monthly economic benefits increased by
94 000RMB. Shanghai UREAL 3D technology developed a wave roller
washing machine mold through the design of balanced distribution of
waterway to provide superior cooling consistency, to ensure uniform
product contraction and improve product quality. The high-efficiency
conformal waterway inside cannot be limited by shape, completely
attached to the surface of mold, substantially increase the efficiency
of mold cooling to reduce the deformation caused by uneven mold
temperature, as shown in Figure 6.
Fig. 6 A wave roller washing machine mold with high-efficiency