Maintaining a Laser Focus
https://www.odtmag.com/issues/2018-03-01/view_features/maintaining-a-laser-focus/
Mark Crawford, Contributing Writer 03.21.18
As medical device manufacturers (MDMs) continue to make smaller and more complex products, an increasing number of companies and their contract manufacturers (CMs) are turning toward laser machining and processing to get the job done. This is especially true for challenging new designs that are difficult or impossible to make with traditional mechanical processes.
Laser technology for micromachining and processing is one of the fast-growing manufacturing segments in the medical device industry. For micromachining, a laser beam is used to remove material during the manufacturing process. This also includes making small holes, slits, and grooves into a wide range of materials, including advanced polymers, ceramics, glass, metals, and alloys. Tolerances can be less than 0.0005 inches.
Laser processing (cutting, drilling, welding, abrasion, and etching) is also used to produce small parts with complex features. Because of their very high speeds and low temperatures, ultrafast lasers can provide burr-free laser cutting and drilling and make stronger weld points that are smaller and more attractive than those made with traditional welding methods. And, as regulations become more stringent, a greater need exists for permanent markings on parts and devices.
Because of these increased demands, laser machining for medical devices is an active and expanding market. Engineers continue to find deeper and broader applications for laser technologies with the products they design; the smaller features, high precision, and faster throughputs they require challenge the more traditional methods of computer numerical control (CNC) machining. There are also more lasers to choose from on the market, including low-cost ultraviolet (UV) lasers with high peak powers and repetition rates that are ideal for marking and engraving a variety of materials. Ultrafast laser applications are gaining more attention—not only because they provide better cutting and faster throughput, but they also process parts at low temperatures without creating heat affected zones (HAZ). This means no secondary processes are required, which saves time and money. Ultrafast lasers also allow engineers to work with more heat-sensitive materials, expanding their design options.
With increased scrutiny from the FDA and other regulatory bodies regarding validation and traceability, MDMs are also paying closer attention to unique device identification (UDI) marking; this is especially true for smaller, more complex products that must face harsh end-user environments, such as sterilization procedures.
“We have seen a dramatic increase in interest for part traceability, due to the FDA regulatory requirements for traceability of products via UDI marking,” stated Michael Rauch, northeast U.S. regional sales manager for ALLTEC FOBA GmbH, a Selmsdorf, Germany-based supplier of laser marking/engraving equipment. “These marks also must stand up to post-passivation and other cleaning processes.
What OEMs Want
OEMs continue to seek superior quality, precision, cost-effectiveness, and timely delivery. “OEMs want tight tolerances, broad materials capabilities, and cost reduction,” said Herb Bellucci, president and CEO of Pulse Systems, a Concord, Calif.-based contract manufacturer that provides precision laser machining services to the medical device industry.
MDMs are especially focused on finding lower-cost ways to make complex products with higher precision and expect their CMs to have the laser and material knowledge and expertise to turn their ideas into successful products. High precision/tight tolerances mean micron accuracy in most cases, especially for smaller, more complex devices.
“We routinely produce features as small as 50 microns in size with single-micron accuracy,” stated Igor Lukash, technical director for Gateway Laser Services, a Maryland Heights, Mo.-based provider of precision laser micromachining services to the medical device industry.
Also, as products become more complex, or use sensitive or combined materials, MDMs want to eliminate heat-affected zones and create small burr-free features that do not require post-processing. The solution is short-pulse ultrafast lasers such as picosecond and femtosecond lasers. Their micromachining capabilities allow MDMs to expand their design ideas and increase the functionality of their products. They then bring their creative concepts to their contract manufacturers—however, this can also take some creative thinking by the CMs to see if they realistically can turn their ideas into high-value products.
For example, Mario Vaenberg, business director for Gateway Laser Services, reported that customers often bring new combinations of materials composed of thin films layered on top of each other. An adhesive layer may be part of the sequence as well, creating an additional challenge for clean cutting. “Often, we have to perform preliminary tests to see if these designs are machinable,” he said.
OEMs must be able to trace materials, components, and products. They want laser processors that are experts in materials, marking, and compliance requirements so they can develop the best marking process for the intended end-use conditions. This becomes more challenging as MDMs use more advanced or sensitive materials. “Many companies are marking lot codes and batch codes so they can track and trace to the origin, should there be any issues with the device in the future,” said Allie Constantino, marketing manager for DPSS Lasers, a Santa Clara, Calif.-based provider of ultraviolet laser marking equipment. “Barcodes, especially 2D [Datamatrix] codes, are very popular in the orthopedic industry because OEMs can store a lot of information on a very small footprint.”
Laser Micromachining
Both fiber and ultrafast lasers are replacing more traditional CNC machining processes because they provide faster throughput and better cut qualities. Conventional machining typically requires tooling and multiple steps and is not as suitable for producing the very small features MDMs desire in their products. Lasers can produce features up to an order of magnitude smaller than Swiss CNC machines. They also can process parts at low temperatures, without creating HAZ that require secondary processes to fix (this is especially important for neurovascular products like stents). Lasers can also be combined into a single hybrid laser—for example, fiber and CO2 lasers, or ultraviolet and infrared (IR) lasers, can be bundled into one machine for cost-effective processing and part handling.
Femtosecond lasers are picking up new applications quickly, in part because these laser systems are rapidly coming down in price. This affordability is moving femtosecond lasers from research and development labs into production line systems. Femtosecond lasers can be in the IR, green, and UV wavelengths. Femtosecond lasers (regardless of wavelength) can ablate materials without imparting damaging heat to a range of materials, including metals/alloys, ceramics, polymers, multilayered materials, semiconductors, composites, and rubber. This also means reduced contamination and burring when cutting material.
Femtosecond lasers are preferred for micro drilling and cutting high-precision holes and shapes without any thermal damage, with accuracies within a single micron and sub-micron repeatability. Athermal ultrashort pulse lasers eliminate the need for costly finishing operations to remove HAZ, saving time and money. They are also a good choice for prototyping, low-volume production of intricate parts, and high-volume manufacturing.
One drawback to ultrafast lasers is their initial cost and return on investment. “However, the cost effectiveness of the newer laser technologies such as short-pulsed lasers and diode-pumped fiber lasers has improved significantly over the last few years,” said Bellucci.
More MDMs and their CMs are recognizing that laser technologies in almost any role can be a key factor in reducing overall manufacturing costs—saving time and money and improving quality and precision.
“Some product development professionals think of laser technologies as being expensive and separate from other manufacturing technologies, such as machining,” said Chip Harvill, vice president of Cadence, a Staunton, Va.-based contract manufacturing partner for medical device and diagnostics companies.
In fact, just the opposite is true, especially with the rise of “hybrid” machine tools, which combine the capabilities of laser cutting and conventional CNC Swiss machining into a single system. For example, lasers can be fully integrated with a multi-axis precision CNC lathe, with a fully enabled laser-cutting module, that operators can use when needed. LaserSwiss systems provide the high productivity of Swiss machining precision cutting from the laser cutter, compared to traditional CNC machining, “without having to move the part from machine to machine,” said Harvill. “They can create more innovative and complex tube products, never possible before, at a much lower cost.” For example, he noted, many new robotics and sports medicine devices have benefitted from this process, which allows for the functional requirement of incorporating areas of articulation and precision machining in the same part.
Pulse Systems recently added a Tsugami LaserSwiss machine to its manufacturing facility. The system enables the production of laser-cut parts with machined features in a single set-up, increasing productivity and eliminating the need to mechanically align features added on one machine to parts made on another machine.
“The most impressive aspect of this machine is the complete integration of its laser cutting and machining capabilities, fully indexed in all 11 axes of motions,” said Bellucci. “In certain situations, this machine represents a game-changing technology because it makes previously impossible designs possible.” Regarding productivity, the payback comes with the full automation of production parts, elimination of duplicate set-ups, and smoother part handling and alignment.
Laser Welding
Laser welding is also gaining attention for complex products, especially those with complex geometries, dissimilar metals, heat-sensitive assemblies, or other situations where thermal distortion could be an issue. Depending on the requirement, laser welding can be a better joining process than bonding methods such as gluing or soldering. It is becoming the preferred method of choice for joining plastics and metals, as well as creating smaller, stronger, and higher-precision welds (for example, titanium implants). Spot sizes can be as small as 0.004 inches and provide repeatable quality. Laser welding saves time and money, and increases throughput, because high-precision welds can eliminate the need for the multiple operations that most bonding processes require, such as grinding.
“Laser welding is also a good alternative to bonding when adhesives are not desirable,” added Natalia Christensen, senior technical consultant for Potomac Photonics, a Baltimore, Md.-based contract manufacturer for the medical device industry. “For example, it can be challenging to contain the flow of liquid adhesives to specific locations on the part or in the case of medical devices, the chemistry might be toxic to cells.”
With the constant pursuit by OEMs for higher quality and lower costs, custom laser welding solutions are now being optimized for high precision and affordability. A few years ago, Cadence relied on commercially available standard equipment to handle typical welding application requirements. As welding requirements became increasingly complex, Cadence created its own in-house laser welding solutions, customized to the customers’ part requirements. “This approach allows us to choose the best laser raw technology and couple it with the motion control and material handling systems needed to yield the best outcome for our customers,” said Harvill.
Cadence identified a specific capability gap in the established supply base for the rapid development of new complex sub-assemblies that required laser-welding as a means of joining. MDMs were looking for prototyping and “proof of principle” parts in days, not weeks—something that typical production welding cannot accomplish. To fill this gap, Cadence established its fully dedicated Advanced Welding Lab. This approach integrates a variety of complex welding capabilities into a rapid manufacturing process, allowing more creative options for product development. “Our custom laser-welding work cells are based on the production part requirements of the customer,” said Harvill. “We integrate the best laser technology, along with the appropriate motion control and material handling systems, to yield the highest precision and lowest part cost.”
Laser Marking
Laser marking systems typically range from 1 to 55 watts in power; they are also available as nanosecond, picosecond, and femtosecond UV lasers. “The only material that we cannot mark is natural Teflon,” stated Constantino. “All other materials can be permanently marked with our UV solutions.” The readability and scanability of laser marking can, however, vary dramatically according to the size of the component, surface roughness, material type, and even the color of the anodizing.
Many OEMs are familiar with laser marking, but only in terms of the capabilities of IR or CO2 lasers. These “hot” lasers essentially burn the material to leave a mark, but can also damage the surface of sensitive materials. UV lasers, in contrast, have a “cool” photochemical or photoablation reaction with the material. There are also limitations to the IR lasers as far as the materials they can mark, minimum spot size, and work area, compared to UV lasers.
“UV lasers take advantage of a cold marking process that does not require high average power levels and allows damage-free, permanent marking on virtually any material,” added Constantino.
UV laser marking systems can also be integrated with multi-axis robot arms. For example, a six-axis robot arm can work with complex geometrical shapes and a variety of part sizes to achieve a permanent mark in a hands-free, batch process. This is ideal for marking alpha numeric text, Datamatrix barcodes, and sequential numbering of parts. “These UV laser integrations can get down to a six-micron spot size, with small 15 x 15 mm work areas, or larger work areas of up to 500 mm with beam sizes of 50 microns,” said Constantino.
ALLTEC FOBA GmbH is receiving more requests for very small “micro-code” marking, with UDI ranges down to 1mm x 1mm and sometimes even smaller. Typical applications are for small instruments, bone screws, and some electronic components.
“The ability to mark different plastics as well as metals that undergo passivation is achieved by different wavelength lasers and precise software control related to alignment/position of the mark,” said Rauch. “FOBA utilizes a very powerful vision-based alignment method that has the ability to do pre-mark validation. For example, when trained, the camera can actually recognize that the correct part has been loaded, adjust for an angular displacement, and direct the laser where to place the mark. Our camera alignment system includes the ability to read and verify the UDI code, as well as collect the read data for transmission to the end user’s enterprise resource planning [ERP] system.”
Lowell has taken the FOBA M3000 Series Laser Marker to the next level by adding robotic tending to eliminate manual part loading. Integrated smart pallets are fed into the FOBA via a Motoman HP20D robotic arm. The FOBA camera automatically detects the items to be marked and adjusts the laser into the correct position. “These two technologies enable us to load pallets containing up to 200 bone screws at a time into the laser marker, reducing error and running lights-out,” said Philip Allen, director sales/marketing for Lowell, a Minneapolis, Minn.-based contract manufacturer of complex implants for the orthopedic and cardiovascular markets. “It’s increased our capacity by about 50 percent.”
Picosecond “black marking” of medical devices is the result of Trumpf’s TruMicro Mark 2000, a full-featured ultrashort pulse laser marking station that includes a scanner, laser cooler, and software. The ultrashort pulses enable cold processing, which allows fabricators to single-pass mark materials with a corrosion-resistant, non-fading ultra-black mark. The system offers the benefits of maximum process stability and monitored pulse energy for each individual pulse and can also mark chrome-plated plastic surfaces without thermally damaging the plastic or polymer. The deep black, corrosion-resistant markings remain corrosion-free despite daily cleaning and sterilization.
“The high peak pulse power of the picoseconds laser creates a nanostructure on the surface of the work piece,” stated Athanassios Kaliudis, media spokesperson for Trumpf. “The rough surface produces a sort of light trap which reduces the diffuse scattering of the light and evokes a permanently black mark. The special quality of this process is that the steel's chromium oxide layer remains intact, which prevents corrosion from forming.”
Future Laser Trends
According to Geoff Shannon, manager of advanced technology for Amada Miyachi America, a Monrovia, Calif.-based manufacturer of laser systems, welding, plastics, and process monitoring—which are all well-established in general industrial manufacturing—are starting to evolve in the medical sector.
Shannon observed in an article on Advancedmanufacturing.com1 that, with catheters and tubes for medical applications decreasing in diameter, weld sizes are down to about 100 μm and smaller, compared to 300 or 400 µm a few years ago. The expanding range of laser capabilities “has allowed us to access areas where we couldn’t weld before, with much smaller spot sizes with the fiber laser,” said Shannon. “The nanosecond fiber laser is arguably a more cost-effective solution for certain types of welds, so that is opening more doors, too.”
Although welding plastics is well-established in other manufacturing sectors, it is not well understood within the medical industry because so many parts rely on adhesives, which MDMs understand and feel comfortable with. Shannon believes that more MDMs will experiment with laser processing of transparent materials in the next few years, thanks to the greater variety of lasers available in various wavelengths. He indicates that currently thulium fiber lasers in the 1.5–2 µm range are best for the processing of transparent welding.
As more extremely small, high-precision features are built into new medical designs, perhaps the largest production benefit will be gained through improved process monitoring. “You’ve got a very small signal and a lot of signal is lost—particularly at the start of the weld,” said Shannon. With smaller medical welds, this could be four milliseconds or less—too small for existing process monitoring solutions to track accurately. Solutions for small-scale process monitoring will likely be proprietary, custom-designed, in-house systems. “That’s something we’re working on; it’s not necessarily ready for prime time, though,” said Shannon.
As Shannon points out, laser processes continue to evolve, expand their capabilities, and improve the quality of medical devices—and even help out with validation and traceability. However they are used, laser systems—especially ultrafast lasers—will increasingly be a key component to faster operations and lower overall costs. It is also a great benefit to MDMs that high-speed lasers are becoming less expensive, making them more affordable throughout the supply chain and allowing smaller players to be more competitive.
“Many common applications today call for very tight dimensional specifications,” said Harvill. “When coupled with high-enough volumes, this can justify the cost of purchasing the laser equipment. With prices coming down, more contract manufacturers can consider this investment.”
References
Mark Crawford is a full-time freelance business and marketing/communications writer based in Madison, Wis. His clients range from startups to global manufacturing leaders. He also writes a variety of feature articles for regional and national publications and is the author of five books.