Laser beam cutting and welding of coronary stents

Acta of bioengineering and biomechanics / Wrocław University of Technology, 2009

Coronary stents are the most important supports in present day cardiology. Flexibility and trackability are two basic features of stents. In this paper, four different balloon-expandable coronary stent systems were investigated mechanically in order to compare their suitability. The coronary stent systems were assessed by measurements of stent flexibility as well as by comparison of forces during simulated stenting in a self-investigated coronary vessel model. The stents were cut by laser from a single tube of 316L stainless steel or L-605 (CoCr) cobalt chromium alloy. The one-and four-point bending tests were carried out to evaluate the stent flexibility E x I (Nmm(2)), under displacement control in crimped and expanded configurations. The flexibility of stents would be rather dependent on the design than on raw material. In general a more flexible stent needs lower tracking force during the implantation. The L-605 raw material stents need lower track force to pass through in the v...

Cutting of 316L Stainless Steel Stents by using Different Methods and Effect of Following Heat Treatment on Their Microstructures, 2017

In this study, effect of different cutting methods and following normalization heat treatment on microstructure of 316L stainless steel tubings were investigated. 316L stainless steel is the most commonly used material for coronary stent production. Tubings were cut with laser cutting, plasma cutting, oxy-fuel cutting, water jet cutting and electrical discharge machining methods. Cut tubings were characterized by using Scanning Electron Microscope (SEM). Separate samples were prepared for heat treatment operation. 316L stainless tubings were cut with same methods and same parameters. Normalization heat treatment was applied to the samples. Heat treated tubings were characterized by using Scanning Electron Microscope. When results were evaluated, it was seen that laser cutting gives the best results rather than that of other cutting methods in terms of homogeneous microstructure, smoothness of cutting surface, a microstructure without oxidation and distortion etc.

Journal of Materials Engineering and Performance, 2021

This paper focuses on microstructural and mechanical characterization of metallic thin-walled tube produced with additive manufacturing (AM), as a promising alternative technique for the manufacturing of tubes as a feedstock for stents micromachining. Tubes, with a wall thickness of 500 lm, were made of 316L stainless steel using selective laser melting. Its surface roughness, constituting phases, underlying microstructures and chemical composition were analyzed. The dependence of hardness and elastic modulus on the crystallographic orientation were investigated using electron backscatter diffraction and nanoindentation. Spherical nanoindentation was performed to extract the indentation stress-strain curve from the load-displacement data. The obtained results were compared with those for a commercial 316L stainless steel stent. Both tube and commercial stent samples were fully austenitic, and the as-fabricated surface finish for the tube was much rougher than the stent. Microstructural characterization revealed that the tube had a columnar and coarse grain microstructure, compared to equiaxed grains in the commercial stent. Berkovich nanoindentation suggested an effect for the grain orientation on the hardness and YoungÕs modulus. The stress-strain curves and the indentation yield strength for the tube and stent were similar. The work is an important step toward AM of patient-specific stents.

2016

Implants are becoming more important in medical area, with improving of their functions due to the advancements in technology and science. 316L stainless steel is the most common material used in implants because of its good mechanical properties, high corrosion resistance and biocompatible structure. Shaping of raw material is the first and the most important step in an implant production process. Cutting is the main step of shaping. Cutting operation causes change in the material structure near the cutting zone. The change of material structure is very important at the implants which has low dimensional tolerances. In this study, 316L stainless steel tube was cut by laser cutting, plasma cutting, oxy-fuel cutting, water jet cutting and electrical discharge machining methods. Cut pieces were examined under SEM (scanning electron microscope) and optical microscope. The effect of cutting methods on material structure was evaluated. After the consideration, normalization annealing was...

2006

Revascularisation by endovascular implant (stent) has great importance in the treatment of coronary artery diseases. Stents are high-technology implants that are the creation of the knowledge of health sciences, physics, chemistry, material science and engineering. Its development can be carried out only by the involvement of these areas of knowledge. Hungary has a stent production since 1995, which is the only one in the new EU member countries. The aim of the project that has been started within the frameworks of the National Research and Development Program, is the development of a new stent family based on the results of the material science researches have started for 10 years and the clinical and production experiences of experts, which could result an equivalent Hungarian product to the market leader products in case of several product lines. The original wire-mesh cut for those replaced welded stents made of wire later from tubes laser cutted ones. The stents are made of bio...

PLOS ONE, 2020

Advances in additive manufacturing enable the production of tailored lattice structures and thus, in principle, coronary stents. This study investigates the effects of process-related irregularities, heat and surface treatment on the morphology, mechanical response, and expansion behavior of 316L stainless steel stents produced by laser powder bed fusion and provides a methodological approach for their numerical evaluation. A combined experimental and computational framework is used, based on both actual and computationally reconstructed laser powder bed fused stents. Process-related morphological deviations between the as-designed and actual laser powder bed fused stents were observed, resulting in a diameter increase by a factor of 2-2.6 for the stents without surface treatment and 1.3-2 for the electropolished stent compared to the as-designed stent. Thus, due to the increased geometrically induced stiffness, the laser powder bed fused stents in the as-built (7.11 ± 0.63 N) or th...

2010

Cardio-vascular deceases are the number one killer in the world. As an alternative to common treatment methods the installation of specific-purpose stents into the damaged blood vessel could be used in order to minimise fatal outcomes. Existing technologies of stent manufacturing provide quite good results but are very expensive at the moment. The given paper deals with the design of stents for cardio-vascular surgery and their manufacturing with help of Q-switched Nd-YAG laser which is considered to be much cheaper and more efficient. The methods of nonlinear programming together with methods of experiments planning were used to find the optimal processing conditions and create adequate numerical models of the process. Several processing schemes based on direct laser cutting and step-by-step laser milling had been considered in the research. Some processing dependencies had been established as well as the possibility to create the special micro-relief on the machined surface with help of laser milling. It was demonstrated that due to the assist gas stream action the micro deformation of the stent's workpiece occurs thus influencing the final machining quality.

Cardiovascular engineering and technology, 2024

Purpose Altered hemodynamics caused by the presence of an endovascular device may undermine the success of peripheral stenting procedures. Flow-enhanced stent designs are under investigation to recover physiological blood flow patterns in the treated artery and reduce long-term complications. However, flow-enhanced designs require the development of customised manufacturing processes that consider the complex behaviour of Nickel-Titanium (Ni-Ti). While the manufacturing routes of traditional self-expanding Ni-Ti stents are well-established, the process to introduce alternative stent designs is rarely reported in the literature, with much of this information (especially related to shape-setting step) being commercially sensitive and not reaching the public domain, as yet. Methods A reliable manufacturing method was developed and improved to induce a helical ridge onto laser-cut and wirebraided Nickel-Titanium self-expanding stents. The process consisted of fastening the stent into a custom-built fixture that provided the helical shape, which was followed by a shape-setting in air furnace and rapid quenching in cold water. The parameters employed for the shape-setting in air furnace were thoroughly explored, and their effects assessed in terms of the mechanical performance of the device, material transformation temperatures and surface finishing. Results Both stents were successfully imparted with a helical ridge and the optimal heat treatment parameters combination was found. The settings of 500 °C/30 min provided mechanical properties comparable with the original design, and transformation temperatures suitable for stenting applications (A f = 23.5 °C). Microscopy analysis confirmed that the manufacturing process did not alter the surface finishing. Deliverability testing showed the helical device could be loaded onto a catheter delivery system and deployed with full recovery of the expanded helical configuration. Conclusion This demonstrates the feasibility of an additional heat treatment regime to allow for helical shape-setting of laser-cut and wire-braided devices that may be applied to further designs.

Procedia Manufacturing, 2019

Despite Bioresorbable Stents (BRS) are the main research line nowadays, permanent stent, both Bare Metal Stents (BMS) as Drug Eluting Stents (DES) will always be useful in some patient-specific cases. To produce permanent stents the current industrial technique is the Laser Micro Cutting. However, this technology produces some thermal damages which raise the manufacture cost. Most of the works done in the last decades have tried to reduce this damages adding traditional cooling techniques. This work aims to study the fibre laser micro cutting process of SS316 tubes assisted by Minimum Quantity Lubrication (MQL). The influence of pulse power, cutting speed, and quantity of coolant upon cutting quality was studied. Cut samples were analyzed by Optical Microscopy with Nikon SMZ-745T attached to digital camera CT3 ProgRes and a Scanning Electron Microscopy Quanta 3D FEG. MQL has demonstrated an average reduction of the dross deposition area (43.3 %), recast layer (37.8 %), kerf width (7.1 %) and heat affected zone (7.46 %) becoming in an effective, economic, and ecologic technique to reduce the thermal damages in laser manufacturing process.

Angiography, 2019

From the introduction of stents, nobody was able to predict the advances that will occur in stent technology over the upcoming decades. Since their appearances, it became evident that this device had significant limitations, such as vessel occlusion and/or restenosis. Despite that, this medical device is the best clinical solution for cardiovascular vessel occlusions. Stents require a deep analysis, in terms of thrombogenicity, manufacturing process, geometrical aspects, and mechanical performance, among many other characteristics. The surface quality obtained in their manufacture process is crucial to blood compatibility, prevents the activation process of thrombosis, and improves the healing efficiency. The forecast stent market makes necessary continuous studies on this field, which help to solve the medical and engineering problems of this device, which are in constant development. Stents have been the center of many research lines over the last decades. The present chapter aims to summarize the state of the art of this medical device in the last years in the fields of design, manufacturing, and materials.