by Kip Hanson
Success with micromachining needs the right machine tool, the right cutters and a healthy dose of patience.
Stop and reflect for a moment about the wealth of advanced technology available to industrialized society today. Cell phones, ever more capable and compact computers, smart devices in our homes, and internet access everywhere you go. It’s no wonder the world seems to be a much smaller place than even a few decades ago, although not, perhaps, in the way you think.
That’s because supporting these technologies requires a significant number of machined components and tooling that have either been resized to Lilliputian dimensions or contain ever more minuscule features, both of which are stretching the limits of what’s possible with modern manufacturing equipment.
This trend is not limited to electronic devices. The automotive industry continues its call for lighter, more fuel-efficient vehicles, which in many cases equates to miniaturized parts. Physicians seek to further shrink the implants and other medical miracles they place within our ailing selves. The list goes on. Simply put, micromachining is demanding work.
The good news is that several machine tool suppliers have stepped up to the microplate with wares specially designed to tackle this tiny realm. Consider Microlution, for example. In mid-2016, this micromachine builder became part of GF Machining Solutions Inc. in large part due to the company’s expertise in laser machining, and has continued to expand its offering ever since.
“GF Machining Solutions strives to always be on the cutting edge of manufacturing technology,” says Karl Kleppek, director of business development for GF Machining Solutions. “The Microlution brand was a perfect fit for our product portfolio which includes milling machines, laser texturing machines, metal additive manufacturing machines and electrical discharge machines (EDM), even for very minute features.”
Onik Bhattacharyya, director of sales and business development at GF Machining Solutions-Microlution, explains that lasers are a vital tool in the micromanufacturing toolbox. They’re used to drill holes the size of dust motes in fuel injector nozzles, cut out watch parts like the world’s tiniest sheet processing machine, or trace the intricate curves of cardiovascular stents. And the mechanism used to do this? Ultra-short pulse lasers, which he says offers HAZ-free machining of virtually any material, and accuracies difficult to achieve with other methods.
“Depending on the application, we might use a nanosecond, picosecond, or femtosecond laser, and deliver the beam via hard optics or a fiber,” he says. “In either case, we focus on extremely high precision applications with accuracy requirements in the 7 to 10-micron (0.00027 to 0.00039 in.) range, and surface finish requirements better than 0.3 µm Ra (approximately 13 RMS). We’re also able to manipulate both the beam and the workpiece in five axes simultaneously, giving us the ability to generate some very complex shapes.”
Bhattacharyya notes that programming and operating an ML-5 or one of the company’s other laser cutting platforms isn’t all that different than running a conventional CNC machine tool. He says GF Machining Solutions’ Microlution team has developed their own software interface that works with standard CAM packages, as well as some “sophisticated parametric programming techniques” that make the machines easy to use.
There’s also a range of advanced options such as automation and in-process inspection systems, features that he says are relatively popular with micromachinists. “It’s pretty rare that we’ll sell a standalone machine. Most of our customers opt for some level of integration with other machine tools and secondary processes. In many of these cases, they come to us seeking a turnkey solution.”
Kern Precision Inc. is another machine tool builder with its eye on the micromachining prize. President Toni Mangold says the company started out as a machine shop in Germany but found itself unable to meet the strict accuracy requirements of a well-known manufacturer at that time, IBM. After searching in vain for a more capable machining centre, the owner decided to design and build his own equipment—when it came time to deliver the parts, the computer giant ended up buying Kern’s new machine tool as well.
That was 30 years ago. Today, Kern Microtechnik continues to machine parts for a range of industries in its “highly-automated” plant in Westried, a small town near Munich, but has also sold more than 1200 of its extremely high precision CNC machining centres across the world.
Kern currently offers three machine models, the Micro, Evo, and Pyramid Nano. Three and five axis versions are available, as are a range of automation options. Many of its customers service the markets described earlier, although Mangold says Kern is a favourite of European watch manufacturers, which use the equipment to machine the miniature main plates and bridges found in a mechanical wristwatch. “These parts must be perfect, or the watch won’t keep accurate time,” he says.
Machining at this scale depends on several factors, Mangold explains. “For starters, you need the extreme accuracy of a conventional way system, but there must be no stick-slip whatsoever—even the slightest amount is enough to break a micro-tool,” he says. “This is why we pump pressurized oil between the way surfaces to assure there will never be metal-on-metal contact. This hydrostatic drive technology is also what gives us the ability to generate sub-micron surface finishes.”
Micromachines boast the same features as their larger cousins, only smaller. These include tool changers, touch probing and laser measurement, automated material handling, and so on, but the feedback and control systems must be more accurate to achieve the extreme repeatability needed by the machine’s users. Kern utilizes glass scale positioning to deliver this, and CNC controls programmable to one-tenth of a micron.
The result is advertised accuracy of ± 0.3µm (± 0.00002) and surface quality 0.05 µm Ra. To illustrate these capabilities, Kern technicians once drilled a series of holes through a human hair. Several years later, they one-upped themselves by engraving a hair with the company name.
“Aside from watch parts, micromachining is used extensively in the optical and dental industries,” says Mangold. “The lens housings used in endoscopic instruments, for instance, and dental implants, which are produced in such high volumes that you’d run into a bottleneck if you stopped to measure each one. But our machining centres are so accurate—more so than most coordinate measuring machines—that our customers have largely eliminated the inspection process, even those operating in a lights-out environment. Once the first part’s been qualified, the rest go straight to the dentist and right into someone’s mouth. Everything just fits.” SMT