Micromachining of 316LVM stainless steel tubes using periodic acousto-optic modulation of pulsed Nd:YAG lasers for cardiovascular stent applications

Optoelectronic techniques can be used in laser applications in biomedical instrumentation to achieve better flexibility and control of the available optical power. These techniques enable the processing and manufacturing of biomedical implants like cardiovascular stents and micrometallic components with reduced heat-affected zone (HAZ) and extremely precise edge cutting. The present investigations deal with the study of laser piercing routines and further profile cutting of thin stainless steel sheet tubes for biomedical implant manufacturing. The process is performed using an acousto-optic (AO) modulator-based pulsed Nd:YAG laser. The AO modulator used in the experiments is a Bragg diffraction device. During the piercing of holes, the focused laser power is gradually increased from a low value and finally reaches the maximum as the beam goes deeper into the material. The most suitable value of dwell time is found to be 50 ms. A nine step staircase modulating voltage with a maximum ac component of 800 mV is used, and the laser power is 4 W in TEM00 operation. The acousto-optic modulator-based pulsed Nd:YAG laser is capable of cutting extremely complex geometries of stents on 316LVM tubing. Laser cutting results in a kerf width of 20.5 +/- 0.5 mu m. Precise strut dimensions of 115 +/- 15 mu m for subsidiary strut, 150 +/- 15 mu m for main strut, and 150 +/- 15 mu m for the link are also obtained. With the piercing routine, extremely fine holes with reduced heat-affected zones are produced, and this quality is reflected during consequent machining of required profiles for implants. (C) 2006 Society of Photo-Optical Instrumentation Engineers.