Experimental Study of Back Wall Dross and Surface Roughness in Fiber Laser Microcutting of 316L Miniature Tubes Page: 3
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Micromachines 2018, 9, 4
This research is focused on assessing the influence of cutting process parameters on surface
roughness (Ra) and back wall dross (Dbw). Fiber laser microcutting experimentation was conducted
on 1.8 mm diameter miniature tubes (material: AISI 316L stainless steel) with two different dimensions
of wall thickness (t) and two hardness conditions as follows: annealed with 110 m wall thickness
and hard drawn with 160 m wall thickness.
2. Materials and Methods
A 4-axis laser-cutting machine (PRECO Model MedPro ST2000, Preco Inc, Wisconsin, WI, USA)
was used to manufacture a single strut of a coronary stent. This machine uses an IPG fiber laser
model YLR-150/1500-QCW-AC (IPG Photonics, Oxford, MA, USA). Experiments were conducted with
continuous wave (CW) operation in a modulated mode, using a fiber feeding of 50 m core diameter,
a 120 mm collimator and final focus lens of 50 mm, resulting in a theoretical spot size of 20.8 m.
However, according to the beam analysis provided for the machine supplier  the minimum radius
is of the order -32.1 m. Table 2 indicates the fiber laser system specifications used in this research.
Figure 1 illustrates the experimental setup used in this research with a close-up image of the laser
cutting head. The tubes were held by the rotating chuck in close proximity to avoid deflections during
the process. Experiments were performed using stainless steel tubes (AISI 316L) with an outer diameter
of 1.8 mm, and a wall thicknesses of 110 and 160 m. Table 3 presents the chemical composition of AISI
316L, while the mechanical properties (data were provided by material supplier: Minitubes, Grenoble,
France)  and metallographies are presented in Table 4.
From images in Table 4, a small grain size was observed in the hard drawn processed tube
compared to the annealed tube. Before struts were laser cut, the tubes were pre-cleaned with a solution
of 10% ethanol and distilled water in ultrasonic bath and then dried.
Table 2. Fiber laser system specifications.
Parameter Specification Unit
Nozzle diameter 0.50 mm
Standoff distance 0.25 mm
Operation mode CW/pulsed -
Maximum peak power 1500 W
Maximum average power (CW mode) 250 W
Minimum pulse width (CW mode and modulated) 0.010 ms
Maximum average power (pulsed mode) 150 W
Pulse width (pulsed mode) 0.2-10 ms
Wavelength (A) 1070 nm
Beam parameter product 0.96 mm mrad
Beam quality, M2 2.82 -
Table 3. Chemical composition AISI 316L for two kinds of miniature tube with 1.8 mm in diameter .
Tube Type C Si P S Mn Ni Cr Mo Fe Cu N
Miniature tube A * 0.011 0.41 0.014 <0.002 1.93 14.73 17.61 2.71 Bal. 0.08 0.04
Miniature tube B ** 0.019 0.42 0.016 <0.002 1.87 14.84 17.53 2.72 Bal. 0.08 0.04
* Miniature tube A: Annealed condition and 110 m wall thickness; ** Miniature tube B: Hard drawn condition and
160 m wall thickness
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García-López, Erika; Medrano-Tellez, Alexis G.; Ibarra-Medina, Juansethi R.; Siller, Héctor R. & Rodríguez, Ciro A. Experimental Study of Back Wall Dross and Surface Roughness in Fiber Laser Microcutting of 316L Miniature Tubes, article, December 26, 2017; Basel, Switzerland. (digital.library.unt.edu/ark:/67531/metadc1062077/m1/3/: accessed November 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Engineering.