Why MDM's interest in femtosecond laser cutting is growing

Fiber lasers have dominated cutting and drilling applications in the medical device industry for several years due to their relatively low cost, scalable performance and high reliability. Femtosecond lasers offer a clear advantage in terms of cut quality, but for a long time have secured only a small market share. However, this is suddenly changing quite rapidly, as evidenced by the sales figures for Coherent cutting systems. Let's take a look at what is driving this dramatic increase in market share compared to fiber lasers.

Femtosecond lasers - better and finer cuts

The unique combination of benefits when using femtosecond (fs) lasers for materials processing has long been known. With traditional lasers, such as fiber lasers, most interactions with the material are photothermal, resulting in a heat affected zone (HAZ). In precision applications, this limits the minimum size of features that can be cleanly machined without heat damage. Damage can mean melting but also unacceptable functional or cosmetic damage to the surface that would require subsequent mechanical processing (e.g. deburring, hand polishing or reaming). Because the femtosecond laser provides orders of magnitude shorter pulses with much higher peak power, the material is vaporized before the heat reaches the part. This cooler, more precise cutting allows smaller features to be created without casting residue, so no grinding or polishing is required. Plus, this method works on almost any material, including parts made of mixed materials such as layers of polymer and metal - see image.

Miniature devices with finer details

A big driver behind the recent increased prevalence of fs laser machining is the demand for medical devices (e.g., peripheral stents, hypoinvasive tubing, minimally invasive instruments, etc.) that feature smaller parts with thinner walls and increased cut detail. We see this particularly in the demand for machines configured to cut geometric shapes into tubes, as shown in the figure above. In addition, the use of more demanding and expensive materials is also a secondary factor. An example of this is magnesium bioabsorbable stents, where post-cutting processing on fiber lasers can reduce yields by up to 50%. However, since fs laser cutting does not require any post-processing of the products, the full yield is maintained.

Other industries (e.g. display/electronics manufacturing) are also moving towards fs laser technology, which represents an additional market demand that further motivates laser manufacturers to develop more advanced fs lasers and machines.

Advances in fs lasers - higher power, lower cost per watt

Femtosecond lasers have reached a new level of maturity in terms of performance, cost-effectiveness and reliability. Power is a particularly important performance parameter as it directly determines production throughput. An example of the new generation of fs lasers is the Coherent Monaco series, where the maximum power has gradually increased from less than 20 W to more than 60 W over the last four years. At the same time, the acquisition cost per W of power has fallen. The first Monaco models have been operating in a demanding 24/7 production environment for several years, underscoring the higher reliability of fs lasers, which further contributes to lower overall operating costs. Together with the cost savings resulting from the elimination of mechanical post-processing steps, this has definitely led to an economic breakthrough for many precision cutting tasks.

Streamlined, automated machines

Of course, most customers who manufacture medical devices don't want a laser, but rather a complete laser machine. And that's the last part of the market picture - the availability of advanced fs laser machines with simplified automated parts handling and product inspection. The machines also include easy-to-use software that doesn't require extensive training or expertise. This gives the user the flexibility to quickly switch between jobs or run long unattended runs. An example of this is Coherent's ExactCut range, which includes our latest operator software: Coherent Laser FrameWork.

Bottom line: filament, fs laser, or both?

One of the biggest questions for anyone purchasing a new machine in MDM today is the choice between a femtosecond or fiber laser. The main remaining advantage of a fiber laser is the ability to cut faster and cut thicker parts due to the higher available power. For thinner parts, however, the power and speed advantages are often reduced due to the need to reduce the number of job repetitions over time and thus avoid cumulative thermal damage to the material and products. The conclusion is that the optimal type of laser really depends on the specifics of the application.

This is why the latest laser cutting machines for medical devices are now available with a choice of fs or fiber laser, or as a hybrid option with both lasers. With the latter option, users can switch seamlessly between lasers, even within a single job, where there may be cuts that can be made more economically with a fiber laser versus an fs laser, and vice versa.

Source: www.coherent.com