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Laser cutting technology for microporous structure of vascular stent
Vascular stents refer to the placement of internal stents in the diseased segment based on the balloon dilatation of the lumen to support the narrowed and occluded segment of the blood vessel, reduce the elastic retraction and reshaping of the blood vessel, and maintain smooth blood flow in the lumen.
Some internal stents also have the function of preventing restenosis.
They are mainly divided into coronary stents, cerebrovascular stents, renal artery stents, aortic stents, etc.
The quality of stent cutting mainly depends on the accuracy of cutting dimensions and the quality of cutting surface.
The cutting surface quality includes: incision width, incision surface roughness, width of heat-affected zone and corrugation of incision section and slag hanging on incision section or lower surface.
There are many factors affecting the quality of stent cutting, and the main factors can be divided into three categories:
a. Characteristics of the object to be processed (material, shape, size, surface state, etc.);
b. Performance of the processing system itself (mechanical system accuracy, vibration of the workbench, etc.) and the influence of light (wavelength, output power, beam mode, beam shape, diameter, divergence angle, focal length, focus position, focal depth, spot diameter, etc.);
c. Processing process parameters (feed speed and accuracy of materials, auxiliary gas parameters, nozzle shape and hole size, laser cutting path setting, etc.)
The specific extension of the laser cutting process of the microporous structure of vascular stents has five major characteristics:
1. Requirements for medical thin-walled tubes in laser cutting:
The raw materials used to make stents are generally medical thin-walled metal tubes, and seamless tubes are used to ensure the consistency and continuity of the materials.
The metal material can be 316LVM medical stainless steel, cobalt-chromium alloy or nickel-titanium shape memory alloy.
As a Class III medical device, the stent must not only consider the uniformity of the chemical composition of the material, but also its size requirements and shape requirements, such as the diameter, wall thickness and dimensional deviation, straightness, cylindricity, coaxiality, etc. of the tube.
2. Laser processing system:
The lasers currently used for cutting metal vascular stents are nanosecond lasers (such as Nd: YAG lasers, water jet lasers) and femtosecond lasers.
For micro devices such as vascular stents, the thinner the slit width, the better. Therefore, in order to obtain high power density and fine incisions, the focus spot diameter is required to be small.
3. Design of cutting path:
Design of cutting path Although Nd: YAG laser has high precision, it is The error caused by small devices such as stents along the length of the processed pipe cannot be ignored.
Due to the cumulative error, the width of the stent rod along the stent axis changes too much, which will cause the stent to lose its support function.
Therefore, the cutting path design of the stent is very important.
A good cutting path should be able to compensate for this error, while minimizing the thermal impact caused by cutting without reducing its mechanical properties.
It is usually not at the expense of reducing cutting efficiency.
4. The influence of airflow and nozzle during laser cutting:
Stent cutting uses oxygen-assisted melting cutting, the purity of oxygen is 99.95%, and the pressure is 0.3-0.6MPa.
The airflow in laser cutting provides part of the cutting energy.
5. Selection of laser cutting speed cutting speed is another important factor affecting the quality of the slit.
The cutting speed of oxygen-assisted laser is related to the laser power density, oxygen flow rate and incision width.
When the laser power density is kept constant, the cutting speed increases with the increase of oxygen flow rate; but when it reaches a certain optimal value, the cutting speed no longer increases with the continuous increase of oxygen flow rate.
When the oxygen flow rate exceeds a certain peak, the cutting speed begins to decrease due to the cooling effect.
The oxygen flow rate remains unchanged, the greater the laser power density, the faster the cutting speed. Under certain cutting conditions, there is a reasonable cutting speed range.
If the cutting speed is too high, the incision slag cannot be completely cleaned, or even cannot be cut through; if the cutting speed is too low, the material is overburned, and the incision width and heat-affected zone are large. Through the orthogonal test method, the appropriate cutting speed is selected as 2.5-3.0 mm/s.
Beyond Laser has been developing and breaking through laser applications in various industries and fields, and looks forward to your discussion and communication.
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What are the precautions for operating a laser marking machine?
1. It is strictly prohibited to start the laser power supply and Q-switching power supply when there is no water or the water circulation is abnormal.
2. The Q power supply is not allowed to operate without load (i.e., the output terminal of the Q power supply should be left floating).
3. In case of any abnormal phenomenon, first turn off the galvanometer switch and the key switch, and then conduct a check.
4. It is not allowed to start other components before the krypton lamp is lit to prevent high voltage from entering and damaging the components.
5. Pay attention to leaving the output terminal (anode) of the laser power supply suspended to prevent sparking and breakdown with other electrical appliances.
6. Keep the internal circulating water clean. Regularly clean the water tank and replace it with clean deionized water or pure water.
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What should we do when laser intensity decreases and the marking is not clear enough?
1. Turn off the machine and check if the laser resonant cavity has changed; Fine-tune the resonant cavity lens. Make the output light spot the best;
2. The acousto-optic crystal is offset or the output energy of the acousto-optic power supply is too low;
Adjust the position of the audio-visual crystal or increase the working current of the audio-visual power supply;
3. The laser entering the galvanometer deviates from the center: Adjust the laser;
4. If the current is adjusted to around 20A but the light sensitivity is still insufficient: the krypton lamp is aging. Replace it with a new one.
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How to maintain a UV laser cutting machine?
1. It is required to carry out regular cleaning every day, remove debris from the countertop, limiters and guide rails, and spray lubricating oil on the guide rails
2. The waste materials in the collection box should be cleared regularly to prevent excessive waste from blocking the exhaust port.
3. Clean the chiller once every 15 days, drain all the internal water, and then fill it with fresh pure water.
4. The reflector and focusing lens should be wiped with a special cleaning solution every 6 to 8 hours.
When wiping, use a cotton swab or cotton swab dipped in the cleaning solution to wipe from the center to the edge of the focusing lens in a counterclockwise direction.
At the same time, be careful not to scratch the lens.
5. The indoor environment can affect the lifespan of the machine, especially in damp and dusty conditions.
A damp environment is prone to causing rust on the reflective lenses and also easily leading to short circuits, discharge and sparking of the velvet laser.
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What accidents might be caused by the laser emission when using a laser cutting machine?
(1) A fire was caused by the laser coming into contact with flammable materials.
Everyone knows that the power of laser generators is very high, especially when it comes to high-power laser cutting machines, the temperature of the emitted laser is extremely high. The possibility of a fire being caused when a laser beam comes into contact with flammable objects is very high.
(2) Harmful gases may be produced when the machine is in operation.
For instance, when cutting with oxygen, it undergoes a chemical reaction with the cutting material, generating unknown chemical substances or fine particles and other impurities. After being absorbed by the human body, it may cause allergic reactions or discomfort in the lungs and other respiratory tracts. Protective measures should be taken when conducting work.
(3) Direct laser exposure to the human body can be harmful.
The damage caused by lasers to the human body mainly includes damage to the eyes and skin. Among the harms caused by lasers, the damage to the eyes is the most severe. Moreover, damage to the eyes is permanent. So when doing homework, you must pay attention to protecting your eyes.
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What is the focused spot diameter of nanosecond, picosecond and femtosecond laser?
Nanosecond: The light spot is 0.5-1mm.
Picosecond: The focused spot is around 0.02mm.
Femtosecond: Under the action of a laser beam with a high repetition rate of 100-200KHz and a very short pulse width of 10ps,
the focused spot diameter is as small as 0.003mm.
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What are the main applications of UV laser cutting machine?
The UV laser cutting machine can be used for cutting and depaneling PCB.
It can precisely cut and shape various types of PCB circuit boards with V-CUT and stamp holes, and open Windows and covers.
It can also be used for separating packaged circuit boards and ordinary smooth boards.
It is suitable for cutting various types of PCB substrates, such as ceramic substrates, rigid-flex boards, FR4, PCBs, FPCs, fingerprint recognition modules, cover films, composite materials, copper substrates, aluminum substrates, etc.
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Precautions for laser cutting machines to process various metal materials?
Copper and brass:
Both materials have high reflectivity and excellent thermal conductivity.
Brass with a thickness of less than 1mm can be processed by nitrogen laser cutting.
Copper with a thickness of less than 2mm can be cut. The gas used for laser cutting processing must be oxygen.
Copper and brass can only be cut when a "reflective absorption" device is installed on the system. Otherwise, reflection will damage the optical components.
Synthetic materials:
Processable synthetic materials include: thermoplastics, thermosetting materials and artificial rubber.
Aluminum:
Despite its high reflectivity and thermal conductivity, aluminum materials with a thickness of less than 6mm can be cut, depending on the type of alloy and the capacity of the laser.
When cutting with oxygen, the cutting surface is rough and hard.
When nitrogen is used, the cutting surface is smooth.
Pure aluminum is extremely difficult to cut due to its high purity.
Only when a "reflection and absorption" device is installed on the fiber laser cutting machine system can aluminum materials be cut.
Otherwise, reflection will damage the optical components
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What should be paid attention to when laser cutting stainless steel?
Laser cutting processing of stainless steel requires the use of oxygen, under the condition that edge oxidation is not a concern.
If nitrogen is used to achieve an edge free of oxidation and burrs, no further processing is required.
Coating an oil film on the surface of the sheet will achieve a better perforation effect without reducing the processing quality.