Abstract
Magnesium alloys are of increasing interest in the medical industry due to their biodegradability properties and better mechanical properties as compared to biodegradable polymers. Fiber laser cutting of AZ31 magnesium alloy tubes was carried out to study the effect of cutting conditions on wall surface roughness and back-wall dross. During the experiments, an argon gas chamber was adapted in order to avoid material reactivity with oxygen and thus better control the part quality. A surface response methodology was applied to identify the significance of pulse overlapping and pulse energy. Our results indicate minimum values of surface roughness (Ra < 0.7 μm) when the spot overlapping is higher than 50%. A back-wall dross range of 0.24% to 0.94% was established. In addition, a reduction in back-wall dross accumulations was obtained after blowing away the dross particles from inside the tube using an argon gas jet, reaching values of 0.21%. Laser cutting experimental models show a quadratic model for back-wall dross related with the interaction of the pulse energy, and a linear model dependent on pulse overlapping factor for surface roughness.
Highlights
A coronary stent is a mesh-like tubular scaffold that is used to expand clogged arteries
This work addresses the simplification of a variety of laser cutting parameters into two simple process parameters: pulse overlapping and pulse energy to study the impact into quality parameters such as back-wall dross and surface roughness
Cutting with No Gas Blowing through the Tube Surface response design trials were programed following the experimental levels presented in Figure 5 illustrates the process variations in surface roughness (Figure 5a) and back-wall dross
Summary
A coronary stent is a mesh-like tubular scaffold that is used to expand clogged arteries. Laser cutting of coronary stents is a well-established process wherein cutting parameters such as laser power, frequency, pulse width, cutting speed gas type, and gas pressure are of great importance to enhance the quality features (i.e., dross, spatter, heat affected zone (HAZ), and surface roughness). Some experiments were carried out on the AZ31 magnesium alloy using a Q-switched fiber laser operating in the nanosecond regime comparing argon and oxygen gases to assist the process [18]. This work addresses the simplification of a variety of laser cutting parameters (i.e., cutting speed, laser frequency, peak power, and pulse width) into two simple process parameters: pulse overlapping and pulse energy to study the impact into quality parameters such as back-wall dross and surface roughness. There is a particular focus on exploring the reduction of back-wall dross based on gas blowing through the tube
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