Laser Cutting Technology Introduce for Vascular Stent Microporous Structure

30-10-2020

Vascular stent is a stent placed in the lesion segment on the basis of balloon dilatation and forming of the lumen to support the vessels in the narrow and occluded segment, reduce the elastic retraction and remodeling of vessels, and keep the lumen blood flow unobstructed.Partial stent also has the effect of preventing restenosis.It is mainly divided into coronary stent, cerebrovascular stent, renal artery stent, aortic stent.

The cutting quality of the bracket mainly depends on the precision of the cutting dimension and the quality of the cutting surface. The cutting surface quality includes the width of the cut, the roughness of the cut surface, the width of the heat-affected area and the ripple of the cut section, as well as the slag hanging on the cut section or the lower surface.There are many factors affecting the cutting quality of the scaffold, and the main factors can be divided into three categories:

A. Characteristics of the processed object (material, shape, size, surface state, etc.);

B. The performance of the processing system itself (precision of the mechanical system, vibration of the working table, etc.) and the influence of light (wavelength, output power, beam mode, beam shape, diameter, divergence Angle, focal length, focal position, focal depth, spot diameter, etc.);

C. Processing parameters (feed speed and precision of materials, auxiliary gas parameters, nozzle shape and hole size, laser cutting path setting, etc.)


laser cutting machine

The specific extension of laser cutting process of vascular stent microporous structure has five characteristics:

1. Requirements of laser cutting for medical thin-walled tubes: The raw materials for the scaffold are generally medical thin-walled metal tubes, and seamless tubes are used to ensure the consistency and consistency of the materials.The metallic material can be 316LVM medical stainless steel, cobalt-chromium alloy or nickel-titanium shape memory alloy.As three types of medical instruments, the stent should consider not only the uniformity of the chemical composition of the material, but also the requirements of its size and shape, such as the diameter, wall thickness and deviation of all sizes of the pipe, straightness, cylindricity and coaxiality, etc.

2. Laser processing system: At present, nanosecond laser (such as Nd: YAG laser, water knife laser) and femtosecond laser are used for metal vascular stent cutting.For microdevices such as stents, the finer the slit width is the better. Therefore, in order to obtain high power density and fine incision, small focal spot diameter is required.

3. Design of cutting path: Although the Nd: YAG laser has a high precision, the error caused by such small instruments as the support along the length direction of the processed pipe cannot be ignored.Due to the accumulated error, the width of the strut along the axial direction of the strut changes too much, so that the strut loses its supporting function. Therefore, the cutting path design of the strut is very important. A good cutting path can compensate for this error, and at the same time, make the thermal impact caused by cutting less and do not reduce its mechanical properties, usually at the cost of reducing the cutting efficiency.

4. Influence of airflow and nozzle during laser cutting: Oxygen assisted melting cutting is adopted in bracket cutting, with purity of oxygen of 99.95% and pressure of 0.3 ~ 0.6mpa.The airflow in laser cutting has provided part of cutting energy.

5. The choice of laser cutting speed Cutting speed is another important factor affecting the quality of the slit. The oxygen-assisted laser cutting speed is related to the laser power density, oxygen flow rate and the width of the cut.However, when it reaches a certain better value, the cutting speed does not increase with the continuous increase of oxygen flow rate. When the oxygen flow rate exceeds a certain peak, the cutting speed starts to decrease again due to the cooling effect.With constant oxygen flow rate, the higher laser power density is, the faster cutting speed is.Under certain cutting conditions, there is a reasonable cutting speed range, cutting speed is too high, cut slag, or even cut through;If the cutting speed is too low, the material will overburn, the incision width and the heat affected area will be large.Through orthogonal test, the suitable cutting speed is chosen to be 2.5 ~ 3.0mm/s.

fiber laser cutting machine


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