The Surging Interest in MDM Cutting with Femtosecond Lasers Explained
A combination of improved performance/cost for these lasers and a growing demand for their superior cutting quality in smaller medical devices is driving strong uptake.
October 18, 2022 by Coherent
図1：ファイバーレーザおよびフェムト秒レーザをベースとするCoherentチューブ切断機のシステム収益比較。
ファイバーレーザは比較的低コストで自在に出力調整ができ、信頼性が高いことから、ここしばらく医療機器製造（MDM）業界における切断・穿孔用途の主流となっています。フェムト秒レーザは、切断品質の面で明らかな優位性を備えていましたが、わずかな市場シェアに甘んじるという状況が長らく続いていました。しかし、図で示したように、Coherentのチューブ切断システムの販売数に注目すると、この状況が急激に変化していることが分かります。ファイバーレーザと比較しながら、市場シェアのこのような劇的な成長を推進した要因について説明します。
フェムト秒レーザ — 切断品質、精度の向上
フェムト秒（fs）レーザを材料加工に利用することで、複数の利点をユニークな形で組み合わせられることは、以前から知られていました。ファイバーレーザのような従来のレーザ加工法の場合、材料の相互作用のほとんどはフォトサーマル効果によるもので、熱影響部（HAZ）を発生させます。精密用途においては、溶融を起こさずクリーンに加工できる機構の最小サイズがこれによって制限されたり、機能や外観の面で許容しがたい不具合を生じさせたりするほか、しばしば機械的な後処理（バリ取り、手作業での研磨、リーマ仕上げなど）が必要になることもあります。これに対してフェムト秒レーザは、桁違いに短いパルスを高いピークパワーで照射することで、部品に熱が伝わる前に、瞬時に材料を蒸発させます。このように、より低温でより高精度な切断を行うことにより、改鋳による加工屑を発生させることなく、より小さな機構を作り出すことができるため、研削や研磨の必要がありません。さらに、この方法は、ポリマーと金属を積層させたような複合素材部品も含め、あらゆる材料に対応します（図を参照）。
図2：フェムト秒レーザは、ほぼすべての材料を、卓越したエッジ品質でしかも材料の改鋳なしで切断できます。
Miniaturized devices with finer details (e.g., struts)
The big driver causing the recent increased uptake in fs laser processing is the demand for medical devices (e.g., peripheral stents, hypo tubes, minimally invasive tools, etc.) characterized by smaller, thinner-wall components with increased number of cut details. We see this is particularly the case in demand for machines configured for tube cutting geometries as in the figure above. In addition, the use of more challenging materials and more expensive materials is also a secondary driver. An example is magnesium bioabsorbable stents where post-processing after fiber lasers can lower yields to 50% but fs laser cutting needs no post-processing. Other industries (e.g., displays/electronics) are moving towards this technology too which provides additional market demand further incentivizing laser manufacturers to develop advanced fs lasers and machines.
Advances in fs lasers - Higher power, lower cost-per-watt
Indeed, femtosecond lasers have reached a new level of maturity in terms of performance, economy, and reliability. Power is a particularly important performance parameter since it directly determines throughput. An example of next-generation fs lasers is the Coherent Monaco series where the maximum power has been successively increased from less than 20 W to over 60 W during the time span covered by the sales chart. The cost per watt for most femtosecond lasers has also recently dropped. So these lasers can deliver higher throughput together with lower cost per part. Early Monaco models have been operating in 24/7 demanding production environments for a few years, underlining the increased reliability of fs lasers that further contributes to the lower overall cost of ownership. Together with the cost savings from eliminating mechanical post-processing steps, this has definitely resulted in an economic tipping point for several precision cutting tasks.
Streamlined, automated machines
Of course, most people making medical devices don’t want a laser, rather they want a complete laser machine. And the last part of the picture is the availability of advanced fs laser machines with streamlined automated part handling and inspection. These also include easy-to-use software that doesn’t require extensive training or expertise. This provides the user with the flexibility to quickly switch between small batches of different devices or to perform long unattended runs of higher volume components. An example is the ExactCut series from Coherent that incorporates our newest operating software: Coherent Laser FrameWork.
Bottom line: Fiber, fs laser, or both?
One of the biggest questions for anyone in MDM acquiring a new machine today is the choice between fs or fiber laser. The main remaining advantage for the fiber laser is the ability to cut faster and to cut thicker parts because of its higher available power. However, for thinner parts, the power and speed advantages are often reduced because of the need to lower the repetition rate and avoid cumulative thermal damage. So the bottom line is that the optimum laser type really depends on the application specifics.
This is a reason why the latest laser machines for cutting medical devices are now available with a choice of fs or fiber laser, or as a hybrid option with both lasers. With this latter option, users can seamlessly switch between lasers, even in a single job where there may be cuts that can be made more economically with a fiber vs a fs laser, and vice versa.
Read more about how the Coherent StarCut Tube Hybrid helped Motion Dynamics leverage laser cutting for neurological sub-assemblies.
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