Regulatory bodies around the world are implementing Unique Device Identification systems (UDI) for traceability of implants and instruments throughout their entire product lifecycle, from manufacturer to patient. In order to be compliant with the requirements of FDA, or if your products are distributed in the European Union, under the Medical Device Regulation, a UDI code must be long-term resistant, reliably legible (machine and human readable) and must conform to given formatting standards.
The UDI can be applied to a device using multiple methods, ranging from chemical etching to laser marking. Laser marking, particularly fiber lasers, has become a top technology according to LaserFocusWorld. It provides long-lasting reliable marks on instruments of almost any material, and is a preferred method to apply UDI codes.
Laser marking technology has played a key role in the implementation of a robust and affordable solution to address the traceability requirements of the market. According to Strategies Unlimited, the medical market was oneof the strongest areas for laser growth in 2018. The firm expects sales from lasers in all markets combined to exceed $14 billion this year.
Although laser technology is the preferred marking technology for UDI, it has its challenges. The laser marking of the UDI on a medical device is often the last step of a long and complex manufacturing process. The device is at its finished state, and any marking error would cause significant loss. Therefore, a safe and error-free marking procedure is critical for manufacturers.
Laser users must develop a marking process that will provide not only a contrasted mark of high quality, but also one that must sustain an expected lifetime of hundreds of autoclave cycles. The very first sign of marking inadequacy is the fading of a mark after passivation. Additionally, the mark must not corrode over the lifetime of the device. Attaining adequate laser marking parameters is one of the most complex trial and error processes that many medical device manufacturers keep secret—like a Michelin star chef would keep recipes only for his valued customers.
Once laser marking parameters have been defined and tooling to support the marking of the instrument is available, production can start. To date, laser marking systems regularly require fixtures to enable a precise mark alignment. The tooling processes is time consuming, as it is a succession of different phases that include design, prototyping, testing, validating and documenting before fixtures can be released to production. The above steps represent a significant added cost to production. A simple fixture design can vary from a couple of thousands of dollars to several tens of thousands, dependent upon its complexity. Some large medical device manufacturers will easily produce on average 200 new fixtures in a year. Manufacturers are well aware that the cost of tooling for laser marking can be several times the cost of the laser marking system.
To control the excessive cost of tooling, manufacturers often turn to lower cost fixtures produced by 3D printers. Made from a process called fused deposition modeling (FDM), these fixtures are relatively inexpensive and can be produced overnight. This provides a great advantage when fixtures are broken or used by other processes. Of course, lower cost fixtures come with downsides; they tend to be on the loose side and are susceptible to wear and tear. Switching to harder material adds cost, and is not always seen as an attractive alternative.
To compensate for the loose repeatability of fixtures and to improve mark performance, laser manufacturers have slowly introduced vision solutions. Vision is a proven technology that has been used in other industries with success, and is based on a camera that is either added to the side of the laser or integrated within the optics of the laser. Accuracy and cost are the key differentiators between the two concepts. External cameras are generally more affordable and provide a full view of the laser marking area, but tend to be inaccurate. Inaccuracies are mostly introduced by the perspective distortion coming from the side view camera.
Lasers with internally built cameras, or so called Through-The-Lens Vision (TTLV), are significantly more accurate but tend to be expensive. The imaging optics are more complex, as it provides an undistorted straight down view of the parts placed under the laser. TTLV technology also has weaknesses—a limited field of view, generally a 1/10th of the laser marking. Because mark accuracy is generally a requirement for implants like bone screws and plates where marking space is highly constrained, TTLV technology is ideal. TTLV provides the required accuracy and repeatability that is often close to a hairline.
“It would be hard for me to consider using a laser without vision,” says Rhonda Davis, Process Engineer at Medtronic in Warsaw, Indiana, who uses laser markers with a TTLV technology called IMP (Intelligent Mark Positioning). “I spent many years using lasers without vision, and in comparison, the ease of use with vision makes things much faster, easier and more consistent.”
The inside of an abutment with laser mark (Character height 0.3mm) seen with a microscope on the left
and as imaged with IMP. The space allocated for laser marking is severely restricted.
Greg St. Jean, from Straumann Group, a dental implant manufacturer with a facility in Andover, Massachusetts, also uses such technology to laser mark the inside of dental implants. St. Jean’s challenge is to accurately place a laser mark on the internal lip of the abutment, about 0.5 mm in width. Previous technology did not always meet his needs, as it was susceptible to part vibrations and motions. Switching to a laser based TTLV technology also allowed him to increase his production from five parts to 16 parts at a time, within a fraction of the old system cycle time.
“If parts are not properly positioned, the IMP System repositions the laser mark to compensate for the part placement variation, which means 100% of our parts are always marked right,” says St. Jean.
When it comes to marking large medical instruments, manufacturers must display the UDI in both human and machine readable formats. Placing UDI 2D code on devices the size of a pair of forceps or larger requires an accuracy placement of +/-0.2mm or +/-0.008”. The laser mark quality and placement repeatability are as important as the content it carries, as they project signs of workmanship, know-how and quality that many device manufacturers want to reflect.
TTLV technology is generally better adapted to devices smaller than 20mm in size. Large medical devices like forceps tend to require the visibility of the full instrument. To address this limitation, TTLV technology has been developed further into a concept named FOBA Mosaic™. A set of images are stitched together to simulate a miniature wide angle camera that is embedded inside of the laser scan head. The outcome is an imaging area as large as the entire marking field of the laser. The stitched images must not only be tiled perfectly, to allow a robust image processing, but must take less than a second to be considered of “practical” use.
The imaging concept, developed specifically to address manufacturing challenges of medical device manufacturers, proved to be a technical achievement and an economic benefit for its users. The Mosaic concept has the major characteristic of providing a straight down view which eliminates perspective distortion. Without perspective distortion, objects can be rotated or translated and they will always have the same outline. Distortion free images make images processing simpler, more robust and faster. With this concept, parts randomly placed under the laser are found and marked with accuracy.
This specific technology eliminates the need for fixtures and tooling, as well as manufacturing and the design, production and maintenance of industrial tooling. The saving of costs and ease of handling, even for unskilled workers, are the main advantages of Mosaic. However, parts can only be marked on surfaces that face the laser while lying flat. If products are curved or three-dimensional, the IMP concept would still be the preferred marking solution.
One of the first companies to evaluate this technology, Add’n Solutions, was chosen as a beta site for its expertise at offering UDI implementation on a broad range of medical devices. Dominik Pfeiffer, CEO at Add’n, says, “What I like most is that with Mosaic, we are saving significant time, especially from the operator’s perspective. You don’t have to scan each part and put it at predefined positions, but just put it in and push the button, even if you have unskilled workers in front of the laser.”
According to Mr. Pfeiffer, marking parts with Mosaic took half the time required using the same equipment but without Mosaic. Pfeiffer estimates that close to 70% of their products can be marked fixture-less. “The visualization of the entire marking field, the automated mark alignment of UDIs is feasible even on parts that are as large as the laser mark area. Large bulky parts like tools, fixtures, instruments, housings, that so far have hardly been able to fit a laser marking machine, can now be processed as well,” Pfeiffer says.
Apart from achieving legal compliance and ensuring product traceability, it is important for manufacturers to find ways to streamline processes, save costs and enhance yield. Medical device manufacturers are always in search of innovations that address manufacturing challenges and achieve economic efficiency, throughput speed and practical applicability. Novelties like TTLV or Mosaic, applied to automated laser alignment, open the door to new ways of manufacturing that are more efficient, less demanding, easier to use, better adapted to today’s manufacturing needs for higher efficiency and more cost effective.
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3. Passivation is the process of submitting the marked device to multiple cycle warm acid baths in order to give the substrate a resistant finish.