By Glen Martin | Jun 01, 2021
Fabricated honeycomb cores
Honeycomb has long fascinated engineers. The hexagonal structures made by bees for storing honey and protecting larvae are remarkably strong and resistant for their relative weight, a fact that was not lost on the ancients. The mythological Greek hero and craftsman Daedalus supposedly fabricated the first artificial honeycomb from gold, and the dome of Rome's Parthenon incorporates a honeycomb design.
Honeycomb structures have a wide variety of applications in modern industry, but they're particularly germane to aviation and aerospace. Aircraft engineer Hugo Junkers was among the first to recognize honeycomb laminate -- a honeycomb core covered by a fabric or metal skin -- as an ideal airframe component. He received a patent for his seminal designs in 1918.
Today, most aviation and aerospace honeycombs are made from a variety of materials: aluminum, aramid fibers such as Kevlar and Nomex, and carbon fiber reinforced plastic among them. All can be cut and shaped to meet specifications, but the process is exacting. That's where MachineTek comes in.
For 29 years, the Carlsbad, California-based company has pursued a narrow and exacting purview: machining, bonding, and shaping honeycomb core components primarily for the aviation and aerospace sectors. The company doesn’t make honeycomb materials, nor does it manufacture airplanes or spacecraft. Without its highly specialized services, however, nobody is flying to the moon or even Paris. MachineTek's clients include Boeing, Northrop-Grumman, and SpaceX.
"We started in 1992 in Southern California -- which is to aviation and aerospace what Silicon Valley is to computers -- because there was a clear need in the industry for precisely fabricated honeycomb cores," says Kevin Darroch, MachineTek's President and CEO.
Composite honeycomb typically comes in sheets and logs, says Darroch, which MachineTek bonds and shapes into the conformation required by the client. This includes wings, fuselage panels, or anything else that moves through air or space that must be simultaneously strong and lightweight.
"We typically get CAD/CAM files from our primary client or a second-tier vendor and machine the product to those specs," says Darroch. "Then off it goes back to the client, who molds and attaches the necessary skins and brackets."
Though it may sound relatively easy, it's not. Honeycomb isn't the kind of material that naturally lends itself to clear edges and mirror-smooth surfaces, so MachineTek employs a variety of specialized devices to achieve its ends.
"You can't just mill or cut honeycomb with the machinery you'd use for other materials," says Darroch. "You'd end up with rough edges that are completely unacceptable for aviation and aerospace applications. We have machines that let us heat-form honeycomb and special high-speed blades that cut in multiple passes, ultimately giving us the surfaces and precise dimensions we need."
While that may sound somewhat like making surfboards -- albeit to a meticulous degree -- such shaping is usually just the beginning of the process, Darroch says.
"It's often like assembling a jigsaw puzzle," he continues. "You might need high-density material in one place of a component and low-density material in another place. Or the specifications might require bonding two or more pieces into a larger piece. So, we have an aerospace-grade oven that lets us do the kind of thermo-couplings we need. I don't think you could call any job 'simple.'"
Moreover, you can't just hang a shingle by your door, call yourself a honeycomb fabricator, and go into business. A big part of MachineTek's efforts is devoted to staying current on the certifications required by both government and clients.
"That includes AS 9100 certification," says Darroch. "That’s a third-party certification specific to aerospace that confirms capability in meeting the stringent and complex requirements of both the defense and aerospace industries. It's extremely rigorous, and we earned it by meeting strict annual audits of our manufacturing processes. AS 9100 includes more than a hundred requirements over ISO 9001 quality management systems certification, which we also have.”
MachineTek also maintains certifications from the International Organization of Standardization for Aerospace, the National Aerospace and Defense Contractors Accreditation Program, the Directorate of Defense Trade Controls, and the Government Industry Data Exchange Program -- along with multiple certifications from client companies including Boeing, Goodrich Aerostructures, and UTC Aerospace Systems.
"Any vendor who looks at us can review our certifications and feel confident that we can do the work," observes Darroch.
MachineTek does defense-related work, but Darroch says security clearances are required only occasionally.
"It's more along the lines of 'Make this shape, but we can't tell you what it's for,'" he says.
Given the company's three decades in a small, highly specialized industry, MachineTek is well known, highly respected, and seldom if ever at a loss for work. Nor is Darroch particularly worried about foreign competitors siphoning away customers with lower bids.
"Objectively, global competition should be a problem, but that's not the case," Darroch says. "There's no good reason for that, really. But Brazil, for example, cuts and shapes what it needs, and the same with China. We've sent some components to South America, and quoted some jobs for Airbus, but not many. But for some reason, honeycomb production and fabrication are largely handled on a national or continental basis. That's certainly the case in the United States."
Challenges: "We have to always ensure we're compliant and certified for new demands and applications," says Darroch. "Starting out, our shapes were relatively simple, and we used pencil and paper. Now it's all CAD/CAM, where you can create extremely complex shapes, and that can make our work much more challenging. Sometimes my machinists complain, and I tell them to count their blessings. That's why we exist; that's why people come to us!"
Opportunities: "The uses for fabricated honeycomb keep growing," says Darroch, "so we'll continue to grow organically with that demand. We could expand to other areas, but we're certainly not running out of applications in our core competence."
Needs: "We're always looking for good people," says Darroch. "We need specialized skills, skills that most people don't have when they're hired. But we can train them -- they just have to be capable of coming up the learning curve. Also, supply chain issues -- restrictive sourcing, specifically -- can sometimes be problematic. We might find that we need weeks, months even, to get certain types of materials for a job. In certain circumstances, a customer [with better access] might order it for us."
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