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Today, nearly all precision laser cutting of metals and non-metals is performed using tools equipped with fiber lasers or ultrashort pulse (USP) lasers, or sometimes both.In this article, we will explain the different advantages of the two lasers and see how both manufacturers use these lasers.NPX Medical (Plymouth, MN) is a contract specialty processing company that manufactures a variety of devices and deployment tools, such as stents, implants, and flexible tubing, using machines that incorporate fiber lasers.Motion Dynamics manufactures subassemblies, such as “pull wire” assemblies primarily used in neurology, utilizing a machine that includes a USP femtosecond laser and one of the latest hybrid systems including femtosecond and fiber lasers for maximum flexibility and Versatility.
For many years, most laser micromachining has been performed using solid-state nanosecond lasers called DPSS lasers.However, this has now completely changed thanks to the development of two completely different, and therefore complementary, laser types.Originally developed for telecommunications, fiber lasers have matured into workhorse materials processing lasers in many industries, often at near-infrared wavelengths.The reasons for its success lie in its simple architecture and straightforward power scalability.This results in lasers that are compact, highly reliable, and easy to integrate into specialized machines, and generally offer a lower cost of ownership than older laser types.Importantly for micromachining, the output beam can be focused into a small, clean spot of only a few microns in diameter, so they are ideal for high-resolution cutting, welding and drilling.Their outputs are also very flexible and controllable, with pulse rates ranging from single shot to 170 kHz.Along with scalable power, this supports fast cutting and drilling.
However, a potential disadvantage of fiber lasers in micromachining is the machining of small features and/or thin, delicate parts.Long (e.g., 50 µs) pulse durations result in a small amount of heat affected zone (HAZ) such as recast material and small edge roughness, which may require some post-processing.Fortunately, newer lasers—ultrashort pulse (USP) lasers with femtosecond output pulses—eliminate the HAZ problem.
With USP lasers, most of the extra heat associated with the cutting or drilling process is carried away in the ejected debris before it has time to diffuse into the surrounding material.USP lasers with picosecond output have long been used in micromachining applications involving plastics, semiconductors, ceramics, and certain metals (picoseconds = 10-12 seconds).But for metal devices with pillars the size of a human hair, the metal’s high thermal conductivity and tiny size mean that picosecond lasers don’t always provide the improved results that would justify the increased cost of earlier USP lasers.This has now changed with the advent of industrial grade femtosecond lasers (femtosecond = 10-15 seconds).An example is Coherent Inc.’s Monaco series of lasers.Like fiber lasers, their output is near-infrared light, which means they can cut or drill all metals used in medical devices, including stainless steel, platinum, gold, magnesium, cobalt-chromium, titanium, and more, as well as non-metals.While the combination of short pulse duration and low pulse energy prevents thermal damage (HAZ), the high (MHz) repetition rate ensures cost-effective throughput speeds for many high-value medical devices.
Of course, almost no one in our industry needs just one laser.Instead, they need a laser-based machine, and there are now many specialized machines optimized for cutting and drilling medical devices.An example is Coherent’s StarCut Tube series, which can be used with fiber lasers, femtosecond lasers, or as a hybrid version incorporating both laser types.
What does medical device specialization mean?Most of these devices are produced in limited batches based on custom designs.Therefore, flexibility and ease of use are key considerations.While many devices are manufactured from billets, some components must be precision machined from flat billets; the same machine must handle both to maximize its value.These needs are usually met by providing multi-axis CNC controlled (xyz and rotary) motion and a user-friendly HMI for simple programming and control.In the case of StarCut Tube, a new tube loading module option comes with a side loading magazine (called StarFeed) for tubes up to 3 m in length and a sorter for cut products, allowing fully automated production .
The process flexibility of these machines is further enhanced by support for wet and dry cutting and easily adjustable delivery nozzles for processes requiring assist gas.Spatial resolution is also particularly important for machining very small parts, which means that thermomechanical stability eliminates the effects of vibration often encountered in machine shops.The StarCut Tube range meets this need by building the entire cutting deck with a large number of granite elements.
NPX Medical is a fairly new contract manufacturer providing design, engineering and precision laser cutting services to medical device manufacturers.Founded in 2019, the company has built a reputation in the industry for quality products and responsiveness, supporting a wide range of devices including stents, implants, valve stents and flexible delivery tubes for similarly diverse surgical procedures Interventions, including neurovascular, cardiac, renal, spine, orthopedic, gynecological, and gastrointestinal surgery.Its main laser cutter is the StarCut Tube 2+2Â with a StarFiber 320FC with an average power of 200 watts.Mike Brenzel, one of NPX’s founders, explained that “the founders bring years of medical device design and manufacturing experience — more than 90 years in total”, with previous experience with StarCut-like machines using fiber lasers.A lot of our work involves Nitinol cutting and we already know that fiber lasers can provide the speed and quality we need.For devices like thick-walled tubes and heart valves, we need speed, and the USP laser may be too slow for our needs.In addition to high volume production orders – we specialize in small batches of parts – only between 5 and 150 pieces – our goal is to complete these small batch turnarounds in just a few days, including design, programming, cutting, forming , post-processing and inspection, compared to the weeks after an order is placed for larger companies.”In addition to mentioning speed, Brenzel mentioned the reliability of the machine as a major advantage, not requiring a single service call over the past 18 months of near-continuous operation.
Figure 2. NPX offers a variety of post-processing options.The material shown here is T316 stainless steel with a 5mm OD and 0.254mm wall thickness.The left part is cut/microblasted and the right part is electropolished.
In addition to nitinol parts, the company also makes extensive use of cobalt-chromium alloys, tantalum alloys, titanium alloys and many types of medical stainless steels.Jeff Hansen, Laser Processing Manager, explains: “Machine flexibility is another important asset, allowing us to support cutting of a very diverse range of materials, including tube and flat. We can focus the beam down to a 20-micron spot, which is useful for more Thin tubes are very useful. Some of these tubes are only 0.012″ ID, and the high ratio of peak power to average power of the latest fiber lasers maximizes our cutting speed while still providing the desired edge quality. We Absolutely need the speed of larger products with an outside diameter of up to 1 inch.”
In addition to precision cutting and quick response, NPX also offers a full range of post-processing technologies, as well as comprehensive design services that leverage its extensive experience in the industry.These techniques include electropolishing, sandblasting, pickling, laser welding, heat setting, forming, passivation, Af temperature testing, and fatigue testing, all of which are key to Nitinol device fabrication.Using post-processing to control edge finish, Brenzel said, “usually depends on whether we’re talking about a high-fatigue or low-fatigue application. For example, a high-fatigue part like a heart valve might bend a billion times over its lifetime as a post-processing As a step, it’s important to use sandblasting to increase the radius of all edges. But low-fatigue components like delivery systems or guidewires often don’t require extensive post-processing.” In terms of design expertise, Brenzel explains, there are now as many as Three-quarters of clients also use their design services to take advantage of NPX’s help and skills in obtaining FDA approval.The company is very good at turning the “napkin sketch” concept into a product in its final form in a short period of time.
Motion Dynamics (Fruitport, MI) is a manufacturer of custom miniature springs, medical coils and wire assemblies whose mission is to solve customer problems, no matter how complex or seemingly impossible, in the shortest time possible.In medical devices, it primarily emphasizes complex assemblies for neurovascular surgery, including the design, production, and assembly of high-quality wire assemblies for applications such as steerable catheter devices, including “pull wire” assemblies.
As mentioned earlier, the choice of fiber or USP laser is a matter of engineering preference as well as the type of equipment and processes supported.Chris Witham, President of Motion Dynamics, explained: “Based on a business model that is highly focused on neurovascular products, we can deliver differentiated results in design, execution and service. We only use laser cutting to produce the components we use in-house. , to manufacture the high-value, “difficult” components that have become our specialty and reputation; we do not offer laser cutting as a contract service. We have found that most laser cuts we perform are best done with USP lasers, and for many years I have been using a StarCut Tube with one of these lasers. Due to the strong demand for our products, we have two 8 hour shifts a day, sometimes even three shifts, and in 2019 we need to acquire another StarCut Tube to support this Growth. But this time, we decided to go with one of the new hybrid models of femtosecond USP lasers and fiber lasers. We also paired it with a StarFeed loader/unloader so that we could fully automate the cutting – the operator simply put the blank The tube is loaded into the feeder and the software operating program for the product is started.
Figure 3. This flexible stainless steel delivery tube (shown next to a pencil eraser) has been cut with a Monaco femtosecond laser.
Witham adds that while they occasionally use the machine for flat cutting, more than 95 percent of their time is spent creating or modifying cylindrical products for their steerable catheter assemblies, namely hypotubes, coils and spirals, including cutting profiled tips and Cut holes.These components are ultimately used in procedures such as aneurysm repair and thrombus removal.This requires the use of laser cutters on a variety of metals including stainless steel, pure gold, platinum and nitinol.
Figure 4. Motion Dynamics also uses laser welding extensively.Above, the coil has been welded to the laser cut tube.
What are the laser options?Witham explained that excellent edge quality and minimal kerfs are critical for most of their components, so they initially preferred USP lasers.Additionally, none of the materials the company uses can be cut by one of these lasers, including the tiny gold components used as radiopaque markers in some of its products.But he added that new hybrid options, including fiber lasers and USPs, give them more flexibility in optimizing speed/edge quality issues.”There is no doubt that fiber optics can provide higher speeds,” he said.“But because of our particular application focus, this usually means some type of post-processing, such as chemical and ultrasonic cleaning or electropolishing. So having a hybrid machine allows us to choose which overall process – USP alone or fiber and post-processing Handling – Optimum for each component. It allows us to explore the possibility of hybrid machining of the same component, especially where larger diameters and wall thicknesses are involved: even fast cutting with fiber lasers, Then use a femtosecond laser for fine cutting.” He expects that the USP laser will remain their first choice because most of their laser cuts involve wall thicknesses between 4 and 6 thou, although they encounter wall thicknesses ranging from 1-20 thou. Stainless steel pipes between thou.
In conclusion, laser cutting and drilling are key processes in the manufacture of various medical devices.Today, thanks to advances in core laser technology and highly optimized machines configured for the specific needs of the industry, these processes are easier to use and deliver better results than ever before.