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A Medical Device Challenge: 토토사이트추천 Thin Wires of Dissimilar Metals
Overview
Stainless steel or nitinol are popular materials in medical devices. Application experts from Coherent have developed a process to safely weld thin 토토사이트추천 made of such difficult-to-weld materials. This process can even be undertaken without destroying any plastic coating
Micro-토토사이트추천 for medical devices
Laser 토토사이트추천is widely used inmanufacturing 토토사이트추천dical deviceslike implants or endoscopic devices, often to join delicate parts. This becomes challenging if the joining partners are very thin wires made of difficult-to-weld materials. Typical materials are stainless steel, nitinol, or titanium because they are biocompatible, corrosion resistant, and easily sterilized. The challenge becomes even more difficult if a connection of dissimilar materials is intended. The laser is the preferred (if not the only) tool for this task. 토토사이트추천 such materials must not compromise their desirable physical properties, e.g., memory properties of nitinol.
When joining thin 토토사이트추천, a zero gap is required; they must be placed precisely against each other, since no filler is used and even a small gap can be too large for a reliable connection. Accordingly, the laser beam has to be precisely focused, too. While the first problem is solved with a fixture, the latter task requires the alignment of the laser focus position by means of an automated vision system.
Figure 1:Setup for wire 토토사이트추천: The 토토사이트추천 partners are fixed on a tube. Process gas is introduced through an 8 mm brass tube.
토토사이트추천 with the ExactWeld 430
토토사이트추천 thin wires with diameters as small as 25 µm (0.001”) requires a precise application of energy into the 토토사이트추천 spot. The small pulse energy must be delivered in a controlled and reproducible way. The duration and temporal shape of such a laser pulse plays a crucial role.
TheExact토토사이트추천 430machine from Coherent is a turnkey solution for precision laser 토토사이트추천 that meets all these requirements. The workstation contains an integrated fiber laser source (Coherent StarFiber). Typical laser configurations for the ExactWeld range between 100 W and 600 W of output power. With a reproducible pulse modulation width, millijoule-energy laser pulses can be created. The laser beam is delivered by a galvoscanner or a fixed 토토사이트추천 optics system. The workstation also includes a system for the control and supply of process gases. Just as important, the Class 1 laser housing complies with the latest ergonomic guidelines.
The vision system and illumination play a crucial role when processing parts with such tiny dimensions. When correctly optimized, the vision system enables automated processing, which means, for example, that a weld gap control stops the 토토사이트추천 process if the gap is too large.
The wires are placed on a designated fixture before machining. This fixture is essential to keep the wires precisely in place during the 토토사이트추천 process. The workstation is available with several options for the robotic part clamping of the fixtures. It supports up to four degrees of freedom (x, y, z, and rotation). User-friendly software controls the system, which also has factory automation capabilities (Industry 4.0/Internet-of-things ready) to enhance the quality, yields, and throughput of small metal part 토토사이트추천. All processed parts can be recorded for traceability: data may include a part number, time stamp, and certain images.
"When correctly optimized, the vision system enables automated processing, which means, for example, that a weld gap control stops the 토토사이트추천 process if the gap is too large."
Laser 토토사이트추천 of 25 µm nitinol and stainless-steel wires
In a recent study in the Coherent application labs, the ExactWeld 430 was used to join thin 토토사이트추천 made of nitinol and stainless steel. Several material combinations were chosen:
1) nitinol/nitinol
2) stainless steel 316L/stainless steel 316L
3) stainless steel 316L/nitinol
The two different wires were fixed as coils on a liner, which was protected by a PTFE sleeve. A critical goal was to join the wires without damaging the PTFE sleeve. The diameters of the 토토사이트추천 partners were equal; wires were tested with d = 25.4 µm as well as some larger diameters. The task was successfully accomplished without cutting through the PTFE sleeve in all cases.
Some key process details were as follows. The laser used a 2x beam expander with a focal length of 100 mm. The working distance was 0.5 mm with a theoretical spot diameter of 12.5 µm. For the diameter of 25.4 µm, the laser power for 토토사이트추천 varied from 30 W to 50 W, depending on the material combination. The pulse duration was adjusted to between 0.035 and 0.05 ms, resulting in pulse energies between 1 mJ for 토토사이트추천 and 2.5 mJ for cutting off the protruding wire. Argon was used as process gas for all the experiments with a flow of 15 l/min, a brass tube diameter of 8 mm, and a BAK 4 nozzle at a distance of 1.4 mm (see figure 2).
For 토토사이트추천 thicker wires the pulse duration was increased while the actual laser power was kept at the same level as it was for 토토사이트추천 thin wires. After 토토사이트추천 the wires, the obstructing wire ends were cut off with a series of stronger pulses.
Figure 2:토토사이트추천 of nitinol to nitinol (left) and nitinol to stainless steel 토토사이트추천 (right).
Study results
The application trial showed that a 100 Watt StarFiber laser is sufficiently powerful to weld different wire combinations. The process window is fairly narrow for all types. It is smaller than 10 W in peak power and less than 10 µs in pulse duration. Higher values cut the wires while lower values do not connect them. The pulse shape that was used helped to make the process stable. It is essential that the wires touch and that the gaps cannot be bridged. Cutting the wires also carries the risk of 토토사이트추천 the wire ends to the next wire. Therefore, positioning is critical.
| Peak-Power [W] | Pulse Duration [ms] | Repetition Rate [Hz] | Speed [mm/min] | Rem토토사이트추천ks |
| 30 | 0.035 | 30 | 20 | 토토사이트추천 |
| 40 | 0.05 | 30 | - | Cutting |
Turnkey optimized solutions
TheExact토토사이트추천 workstationsare factory customized by applications experts from Coherent according to the desired applications. This customization includes not only the 토토사이트추천s, process control, and automated handling systems but also special fixtures, if necessary. Customers thus gain tremendous value from the collective knowledge and experience of the application engineers.
In this way, ExactWeld can be optimized for a wide variety of weld types and geometries. For contact 토토사이트추천, minimum 토토사이트추천 spots with diameters down to 10 µm can be realized. For seam 토토사이트추천, small seam geometries can be achieved at high 토토사이트추천 speeds. Free-form 토토사이트추천 can also be programed. Thanks to the rotary stage, seal 토토사이트추천 can be performed with no porosities and crack-free seams to provide for leakproof 토토사이트추천. For all systems, worldwide local service and spare parts supply are always readily available.
"Custo토토사이트추천rs thus gain tre토토사이트추천ndous value from the collective knowledge and experience of the application engineers."
"Recent practical improve토토사이트추천nts in terms of reliability, performance, and ease of use, promise to make it more economically attractive as well."
Coherent is a vertically integrated manufacturer unmatched in our ability to also offer superior products at several different levels of integration. For example, the newExact토토사이트추천 430combines the industry-leading ExactSeries workstation platform, already proven in many applications, with a state-of-the-art Coherent StarFiber 100 to 600 토토사이트추천 sub-system. For traceability, every part can be logged with part and process details.
Figure 3:The ExactWeld 430 from Coherent is a class 1 laser device for automated 토토사이트추천 tasks.
Summ토토사이트추천y
In conclusion, one of the most challenging 토토사이트추천 applications in토토사이트추천dical device manufacturing– the 토토사이트추천 of wires as thin as 25.4 µm (0.001”) from nitinol and stainless steel – has been successfully accomplished. A special material such as nitinol requires a small process window; the pulse power, duration, and temporal shape must be generated reliably and repeatably. The small dimensions also demand precise positioning of the workpiece and the focused laser. TheCoherent Exact토토사이트추천 430has already established itself in a variety of other demanding 토토사이트추천 applications in the medical device industry. It is now proved able to deliver the best solution for this difficult wire 토토사이트추천 task. Recent practical improvements in terms of reliability, performance, and ease of use, promise to make it more economically attractive as well.