With its patented Laser MicroJet (LMJ) process, SYNOVA S.A. from Nyon, Switzerland has established a “wet” laser processing method. In this process, the laser beam is guided to the workpiece by a hair-thin water jet. It is used to shape, drill and cut diamonds and jewels as well as tools, turbine blades or semiconductors. In this interview, Dr. Bernold Richerzhagen, founder and CEO of the spin-off of École Polytechnique Fédérale de Lausanne (EPFL), talks about the beginnings of the process, water as a medium in highly precise laser processes and the most important growth markets for laser material processing.
Dr. Bernold Richerzhagen: Today, SYNOVA has more than 100 employees, half of whom are in our headquarters in Switzerland, the others in our subsidiaries in USA, Japan, China, India, South Korea and, as of May 2021, in Germany too. We are constructing a new production site in Rottweil, Baden-Wuerttemberg. Since 2015, De Beers, the world’s largest supplier of raw diamonds, has had a 33.4 percent stake in SYNOVA. I myself am the majority shareholder and CEO. Twenty-three years after I founded it in 1997, we are experiencing a huge surge in demand. The pandemic accelerated innovations based on new products, materials and processes for which we offer appropriate solutions. More and more industries are recognizing the advantages of our Laser MicroJet (LMJ) process, which combines a pulsed laser with a fine stream of water.
Richerzhagen: After studying mechanical engineering with a focus on medical technology in Aachen, I went to Lausanne as a scholar to work on my thesis as part of an artificial heart project. At the École Polytechnique Fédérale de Lausanne, I came across my PhD subject: The development of a laser for painless dental treatment. In order to cool down the point of contact with the light, I originally wanted to work with a water spray, but that failed because the laser beam was scattered by the mist. Instead, I fell back on an idea from Professor Jean-Daniel Colladon, who used a water jet to guide light at the University of Geneva back in 1840; the principle behind it is the total internal reflection, which also occurs in optical fibers. With his research, Colladon laid the basis for modern fiber technology and, ultimately, for our LMJ process as well. Many unsuccessful attempts to combine lasers with jets of water lay ahead of me. We also needed three years of development to demonstrate feasibility. In 1993, I was able to remove material with a laser beam in a water jet for the first time. It was a wonderful moment! I had heard so many times that it could not work.
Richerzhagen: As with other laser processing methods, a strong plasma forms on the processing area. Thankfully, it withstands the water pressure. With each laser pulse, a plasma bubble forms where the light hits the material. The water cools the area between the pulses and washes away any ablated material. Thanks to the cooling and the high frequency of tens to hundreds of thousands of laser pulses per second, the process is fast and efficient. At the same time, it is highly precise thanks to the parallel laser beam. By coupling the laser to the fine, straight water jet, there is no focal point, which means that even cuts a few centimeters deep have smooth, burr-free edges. This is because the beam guidance also works in the cutting gap. We recently used it to cut 100 millimeters of strong silicon carbide. Thanks to its precision and intrinsic cooling, the process is predestined for highly sensitive and very hard materials: Diamonds and other jewels, semiconductors or also technical ceramics.
Richerzhagen: The process is complex and, in the beginning, it reacted very sensitively to interferences. This is due to the fact that a water jet is a physically unstable phenomenon. Where its surface meets the air, it wants to change its shape and take on a spherical form. In order to control this effect, we needed to find the right pressure, suitable nozzles and the optimal water jet diameter and, at the same time, optimize the pulse frequency, pulse duration and output of the laser in terms of process efficiency and repeatability at a consistent level of quality. Today, depending on the requirements, the water jet is 20 to 80 micrometers (µm) thin. For comparison, a human hair has a diameter of 60 µm. The water is ultrapure and pressurized beforehand in our systems. With these parameters, we were able to develop a stable, industrial process that has established itself even in strongly regulated industries. Today, LMJ is being used to process important engine components for the latest generation of aircraft from Boeing and Airbus—and thousands of patients are living with stents processed by LMJ.
Richerzhagen: The quantities of water are minimal, and because we use highly purified water, no particles or foreign bodies enter the process. Rather, it increases the precision by washing the dissolved material out of the processing area. As we treat the water in our systems, we can use any water around the world—whether in India, China or Africa. Recently, we even realized water recirculation for a customer. Due to the very low quantities of around one liter per hour, this special effort usually isn’t necessary.
Richerzhagen: It is a very important market, which is currently undergoing many changes for both synthetic and natural diamonds. Our new, completely automated CNC-controlled LMJ laser cutting and polishing method processes raw diamonds into brilliants with 57 facets within an hour. It previously took weeks to achieve the µm-precision required. Our process also uses the shape of the raw diamonds optimally, thus minimizing waste and leaving useable off-cuts rather than grinding powder. An additional driving force is the rapid progress in the production of synthetic diamond materials. This development is similar to when aluminum was just starting to be used. It was once very expensive—and is now a common packaging material. The cheaper it becomes to create diamonds, the broader the range of applications. This is an excellent development for laser processors, because only they can process diamonds without wear.
Richerzhagen: In addition to the diamond industry, the semiconductor industry is among the most important customers. And the use of lasers is also on the rise in other areas of industrial material processing. We cover the spectrum from technical ceramics, turbine blades and clocks to automobile and tool construction. One growing field of application is the aforementioned processing of ceramic components for aircraft engines. In the interests of lightweight construction, manufacturers are turning to silicon-carbide materials: Partially silicon-carbide fibers in a silicon-carbide matrix. This way, they achieve the highest levels of strength at only a quarter of the weight of the previous inconel alloys. However, processing these demanding materials is a challenge. Often customers are at a loss and come to us. In all our subsidiaries, we operate laboratories where we design the LMJ process to the respective applications of our customers. I think the new materials will catch on in lots of industries. Silicon carbide and diamonds in the semiconductor industry, technical diamonds and high-strength ceramics in aircraft, automobile and tool construction or in medical technology: Highly efficient and precise processing methods are in demand all over for these materials. We are also currently running projects with battery and fuel cell manufacturers. Now—two decades after our foundation—we are seeing that our process is highly sought after in these material-driven innovation fields all around the world. The pandemic further accelerated this change in many industries. For that reason, we are currently expanding our production capacities as a matter of priority. In Switzerland, we are building an assembly hall that is three times larger than our current one. Besides that, we are multiplying our previous capacities in Rottweil and in China. Fortunately, we are benefiting from the fact that the specialist market has relaxed due to the pandemic. Skilled applicants are still very much welcome.