International audienceThe additive manufacturing of metal parts provides new opportunities to freely design of molds with conformal cooling channels, which enhances the productivity of injected plastic parts. In contrast to this manufacturing process, the surface quality of laser sintering parts is limiting the application of such technology on mold manufacturing. This work intends to investigate the surface roughness of maraging steel 300 samples produced by direct metal laser sintering (DMLS) and post-processed with end milling. Based on a set of experiments, combining different laser sintering build directions and milling process the measurement of the resulting surface roughness expresses how these process parameters impact on the final surface quality

Cioca, Vitor Valentin

Del Conte, Erik Gustavo

Jardini, A,

Lavernhe, Sylvain

Morel, Claire

English

Archive Ouverte en Sciences de l'Information et de la Communication

HAL Id: hal-01773243
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Submitted on 21 Apr 2018
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Part surface roughness on laser sintering and milling of
maraging steel 300
Claire Morel, Vitor Valentin Cioca, Sylvain Lavernhe, A Jardini, Erik Gustavo
del Conte
To cite this version:
Claire Morel, Vitor Valentin Cioca, Sylvain Lavernhe, A Jardini, Erik Gustavo del Conte. Part surface
roughness on laser sintering and milling of maraging steel 300. 14th Internation Conference on High
Speed Manufacturing, Apr 2018, San-Sebastian, Spain. ￿hal-01773243￿
Part surface roughness on laser sintering and milling of maraging steel 300 
 
C. Morel (1), V. V. Cioca (2), S. Lavernhe (1), A. L. Jardini (3), E. del Conte (2), 
email: erik.conte@ufabc.edu.br 
 
 
(1) LURPA, ENS Paris-Saclay, Univ. Paris-Sud, Université Paris Saclay, 94235 Cachan, France 
(2) CECS, Federal University of ABC, Brazil 
(3) BIOFABRIS, University of Campinas, Brazil 
 
Abstract 
 
The additive manufacturing of metal parts provides new opportunities to freely design of molds with conformal 
cooling channels, which enhances the productivity of injected plastic parts. In contrast to this manufacturing 
process, the surface quality of laser sintering parts is limiting the application of such technology on mold 
manufacturing. This work intends to investigate the surface roughness of maraging steel 300 samples produced 
by direct metal laser sintering (DMLS) and post-processed with end milling. Based on a set of experiments, 
combining different laser sintering build directions and milling process the measurement of the resulting surface 
roughness expresses how these process parameters impact on the final surface quality. 
 
Keywords: Direct metal laser sintering (DMLS), milling, surface roughness, maraging steel 300.  
 
1. Introduction 
 
The additive manufacturing process of metal parts provides greater autonomy for tooling design with complex 
geometry and, thus, allows the manufacture of molds with integrated cooling channels (conformal cooling) 
reducing the injection molding cycle time [1]. Maraging steels are known to combine good mechanical 
properties, such as high strength, high tenacity, good weldability and dimensional stability [2]. Prior studies 
show that the mechanical properties and the part quality directly depend on parameters used during the sintering 
process [3][4]. Yasa et al. [4] studies investigated the selective laser melting (SLM) process in maraging steel 
300 parts. The same study showed that a higher scan speed for layers with 60 µm thickness induced lower 
roughness values (30 µm Ra). The parameter range of the SLM process of maraging steel-manufactured samples 
led in different roughness after the surface milling [5]. The roughness obtained by laser sintering does not meet 
the requirements of mold surface finishing for applying in injection molding. To improve the surface quality the 
polishing post process is required, a difficult to handle and costly operation and your suppression could lead to 
improve mold productivity. In this regard, this study investigates the surface roughness of maraging steel 300 
samples obtained by direct metal laser sintering (DMLS) process and post processed with end milling. 
 
2. Experimental set-up 
 
Figure 1 shows the operation principle of DMLS technology where a laser beam melts the powder layer by layer 
according to the build direction defined to slice the 3D CAD model. 
 
 
Figure 1: Operation principle of DMLS technology [2]. 
 
The Table 1 shows the machine specification and the parameters used in this study. 
 
Machine  EOSINT M 280 
Technology  DMLS 
Laser type  Yb-fibre  
Laser power [W] 170 
Material  Maraging steel 300 
Building platform [mm] 250 x 250 x 325 
Preheating platform [ºC] 40 
Hatch distance [mm] 0.1 
Environment gas   Nitrogen 
Speed [mm/s] 1250 
Stripe width [mm]                                          5
Layer thickness [mm]                            0.02 
Laser focus [mm]                            0.1
Laser beam offset[mm]                          0.015
Scan strategy                                   Line 
 
Table 1 – Machine specification [7] and process parameters. 
 
The build direction was changed in the sintering process. Fig. 2a shows the geometry developed for test 
specimens. Furthermore, the Fig. 2b shows the angles in which the parts were built, and the highlighted surfaces 
show the places of the roughness measurement. 
 
           a) Dimensions in millimeters 
Figure 2 - Test part dimensions and building: a) Geometry b) Build direction. 
The surface roughness was measured in a parallel direction to the building lines using Surtronic S-218 Taylor 
Hobson (set to measure the average roughness Ra with 0.80 mm cutoff). After chemical attack (Nital 5% for 5 
minutes) Olympus BX51M, an electronic microscope, and a scanning electron microscope (SEM) Jeol were used 
to observe the microstructure and the milled surface. The sintered surface milling was performed under dry 
conditions in the machining center Romi D600 with end milling tool with Ø 63 mm and 6 carbide inserts 
(OAKU 060508SR-R50) (see Fig.3) with the following cutting speeds Vc1 = 100 m/min and Vc2 = 200 m/min, 
feed per tooth fz = 0.08 mm and cutting depth ap = 0.25 mm. 
       
 
Figure 3 - Milling tool and insert format. 
 
3. Results and discussions  
 
3.1. Surface analysis 
 
Figure 4 shows the results obtained from surface roughness samples measurements. The arithmetic average 
roughness (Ra) is 3 µm for build direction of 90º. When the part was rotated to 0º, the roughness increased to 
10.1 µm. Finally, when it was built in 45º, the roughness result was 11.36 µm. The direct comparison between 
the samples shows that the roughness values are better to the sample with build direction 90º, showing the build 
direction changes the part roughness. It is important to emphasize the machine changes the scan strategy in the 
last sintered layers. The sintered surface milling provided significant improvement in the roughness. The 
maximum roughness value obtained was 0.6 µm with cutting speed 200 m/min. It was noted that the change of 
the build direction changes the part roughness after milling. The best surface roughness obtain after milling is the 
test part that have the worse surface roughness directly after sintering. However, the change of the cutting speed 
    b)         P1- 0º                   P2- 45º                  P3- 90º 
 
0° 45° 90° 
to 100 m/min results the lower roughness value 0.37 µm (see Fig. 4) and changing cutting speed to 200 m/min 
not causes significant impact on surface roughness. 
 
 
 
Figure 4 – Surface roughness comparison. 
 
The milled surface analysis in SEM showed that are inclusions (see Fig. 5a) and micropores (see Fig. 5b), which 
can be related to fusion failures in the sintering process and shows the need to improve the process. 
 
    
 
Figure 5 – Milled surfaces after laser sintering: a) amplification 45x b) amplification 200x. 
 
3.2. Microstructure 
 
The microstructure analysis shows the change in the solidification shape of the laser melt pool. Fig. 6a (build 
direction 45º) shows a half ellipsoid solidification shape and Fig. 6b (build direction 90º) shows a smooth, 
elongated and cross ellipsoid solidification shape, evidencing the effect of the scan strategy in the part 
solidification. Fig. 6c (build direction 90º) shows formation of elongated acicular microstructures that were 
observed in all samples. 
 
 
Figure 6 – Surface images: a) Amplification 10x b) Amplification 10x c) Amplification 1300x. 
 
4. Conclusions 
 
This study investigated the surface roughness of maraging steel 300 samples manufactured by the direct metal 
laser sintering (DMLS) process and post processed with end milling. The lower roughness obtained directly after 
the sintering process was 3 µm (Ra) in the sample surface with direction of 90º (final surface of the part in plan 
X-Y parallel to building platform). For milled surfaces, the lower roughness was 0,37 µm with cutting speed 100 
m/min with part build direction of 45º. A slight influence of the build direction was noted. Moreover, as 
0
2
4
6
8
10
12
14
As built As built As built VC100 VC100 VC100 VC200 VC200 VC200
Roughness Ra (µm)
0° 45°
90° 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
VC100 VC100 VC100 VC200 VC200 VC200
Ø 23 µm 
Ø 5 µm 
supposed, the microstructure of the material is sensitive to process parameters, in particular the scan strategy. For 
future studies, we suggest the analysis of combination impact of other parameters (e.g.: scan speed, laser power, 
heat treatments etc.) in the part roughness after the milling. 
 
Acknowledgment 
 
The authors would like to thank the technicians Luis Fernando Bernardes, Pedro Anastácio Da Silva, Osmando 
Cardoso and Henriques Frandini Gatti. 
 
References 
 
[1] J. P. K. Gildeon N. Levy, Ralf Schindel, “Rapid manufacturing and rapid tooling with layer 
manufacturing technologies, state of the art and future perspectives,” Manuf. Technol. J., vol. 52, no. 2, 
pp. 589–609, 2003. 
[2] L. Thijs, J. Van Humbeeck, K. Kempen, E. Yasa, and J.-P. Kruth, “Investigation on the inclusions in 
maraging steel produced by Selective Laser Melting,” 5th Int. Conf. Adv. Res. Virtual Rapid Prototyp., 
no. 2007, pp. 297–304, 2011. 
[3] D. Manfredi et al., “Direct Metal Laser Sintering: An additive manufacturing technology ready to 
produce lightweight structural parts for robotic applications,” Metall. Ital., vol. 105, no. 10, pp. 15–24, 
2013. 
[4] E. Yasa, K. Kempen, and J. Kruth, “Microstructure and mechanical properties of Maraging Steel 300 
after selective laser melting,” Proc. 21st Int. Solid Free. Fabr. Symp., pp. 383–396, 2010. 
[5] A. Fortunato, A. Lulaj, S. Melkote, E. Liverani, A. Ascari, and D. Umbrello, “Milling of maraging steel 
components produced by selective laser melting,” Int. J. Adv. Manuf. Technol., 2017. 
[6] C. H. Ahrens and N. 1965- Volpato, Prototipagem rápida : tecnologias e aplicações. Edgard Blücher, 
2007. 
[7] EOS GmbH, “Eosint M280,” 2013. 
 
 


Part surface roughness on laser sintering and milling of maraging steel 300

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Part surface roughness on laser sintering and milling of maraging steel 300

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