Influence of process parameters for sheet lamination based on laser micro-spot welding of austenitic stainless steel sheets for bone tissue applications

Abstract

The laser micro-spot welding process was studied to implement a sheet lamination process-based methodology for the fabrication of austenitic stainless steel scaffolds. AISI 302 sheets with a thickness of 254 μm were laser cut and laser welded. Experimental tests were carried out with different values of average laser power (i.e., 180, 200, and 220 W) and different exposure times (25, 50, 75, 100, 125 ms). The micro-spot welds were visually inspected according to the ISO 13919-1 Class B requirements. Spot welds were qualitatively characterized, and weld dimensions were measured (i.e., penetration depth, top, middle, and bottom width and the heat-affected zone (HAZ)) to identify the cross-sectional shape. Furthermore, process efficiencies (i.e., coupling, melting, and process) were studied. A seam welding model was adapted to calculate the required exposure time and was used to obtain a micro-spot weld to accomplish the quality requirements of the scaffold. A scaffold prototype was designed and manufactured using the selected parameters by experimental trials and using the mathematical model (i.e., a laser power of 220 W and an exposure time of 45 ms).

Characterization of Porous Scaffolds Fabricated by Joining Stacking Based Laser Micro-Spot Welding (JS-LMSW) for Tissue Engineering Applications

“…These results demonstrate high repeatability in the micro-spot weld dimensions obtained in this works. Additionally, it is observed that the micro-spot welds under the Z height of 2 mm presented a fluted shape which is consistent with our previous study [ 10 ]. After the Z height of 2 mm, the micro-spot welds showed a parabolic shape; this change in the weld beads indicated a difference in the heat transfer phenomena [ 10 , 31 ] resulting from the stacking process.…”

“…Forty-three sheets were stacked using laser micro-spot welding. The scaffold was joined using the methodology explained in our previous work [ 10 ]. The final scaffold was cut from the stack using a wire electrical discharge machining (WEDM) machine.…”

“…Figure 3 presents the scaffold designed with the established dimensions. Figure 3 a shows the stack built after laser cutting and micro-spot welding, Figure 3 b illustrates the scaffold after WEDM, and Figure 3 c presents the micro-spot designed to achieve full penetration in accordance with the ISO13919-1 to join three AISI302 sheets and considering the gaps between sheets observed in the previous study [ 10 ]. An aspect ratio (d/w) of 1.25 was considered for spot weld designed to assure higher heat transference in the Z -axis and minimize mechanical distortions due to heat dissipation losses in the X and Y axes [ 29 , 30 ].…”

“…It has been replaced by AISI316L alloy due to its high corrosion resistance, which has allowed its application in bone plates, screws, and oral implants [ 6 ]. To the author’s best knowledge, there is only a study conducted by Cedeño-Viveros et al [ 10 ] using AISI302 alloy in a sheet lamination process for potential applications of bone tissue engineering scaffolds.…”

“…Applications of laser micro-welding include intraocular lenses, knee joint replacements, cochlear implants, and pacemakers [ 27 , 28 ]. Cedeño-Viveros et al [ 10 ] studied sheet lamination using laser micro-cutting and laser micro-welding for bone scaffold applications with promising results. This investigation presents the study of bone tissue scaffolds fabricated through Joining Stacking based Laser Micro-Spot Welding (JS-LMSW) as a sheet lamination (additive manufacturing) process.…”