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Glued & Screwed

 

How mechanical bonding and other creative ideas helped one contract manufacturer grow through good times and bad

 

By Ed Sinkora
Contributing Editor

In many ways Command Technology (Baltimore, MD) has always been like any other thriving contract manufacturer: Dozens of CNC machining centers, excellent QC, and a good team. But twenty years ago, Command’s founder and owner, George Braswell, challenged himself to create a capability that would set the company apart. Ironically (for a machine shop), the answer relied on glue and a torque screwdriver.

Before that, Command was doing well, but bobbed up and down in the economic cycle like everyone else. Braswell had pushed himself through the University of Maryland engineering program working 40 hours a week in a machine shop, from janitor, to machinist (when he showed the boss he could do better at programming the NC machines than the current operator), to production supervisor. With his practical machining knowledge and his engineering expertise (not to mention his habit of working seven days a week), he knew he could do better.
They may have 25 CNC machining centers and a wealth of other equipment, but a big part of Command Technology’s success over the years has rested on their ability to do bonded assembly: Braswell’s own “glue and screw” concept.
He had already won significant defense work from Smith Industries, now a unit of GE Aerospace, by redesigning a number of their cast parts to be machined from solid. So he asked them for a tougher problem to solve. Smith offered the Pylon Interface Unit (PIU) for an attack helicopter. They were brazing the sides together and having a terrible time with distortion. (Think of the PIU as a fancy aluminum box which will be stuffed with critical electronics and subjected to intense vibrations.) Braswell promised he could machine the components and then mechanically bond them together, which Smith’s engineers assured him wouldn’t work because the parts needed to adhere together such that the whole unit passed Electromagnetic Interference (EMI) and continuity testing. Braswell said he could do it with glue. They were skeptical, but let him have his shot.


Defining a New Process

Braswell had already been working with 3M on developing specialized glues for a bomber project. In parallel to that R&D he also made a clever design change to the PIU: bonding pads. As Braswell explains, “Back in the old days bonding required large fixtures to hold the parts together until the glue set, and you’d have to use piano wire or glass beads in the bond to prevent the parts from squeezing out all the glue. So I thought, how can I make this thing more efficient and get rid of the fixtures? That’s when I came up with the concept of ‘glued and screwed.’

“I designed a 5 thousandths high bonding pad in the parts where my screws would go, aligned with a tapped hole in the matching component. That would give me metal-to-metal contact for electrical continuity and would meet EMI requirements. It also provides enough surface area with the right gap for the adhesive and achieves the required strength. Plus it’s easier. You just screw the thing together.”

Not only did the part pass all Smith’s tests perfectly, they rewrote their spec around the new approach. Braswell had turned the difficult black art of bonding into a relatively easy and repeatable process. This eliminated the need for brazing on a whole series of parts.

Making this support structure for a missile nose requires five-axis milling of the three sides, some EDM work, and bonded assembly.

Since then, the process has contributed both to Command’s growth and to steady business in leaner times. Braswell adds that they’ve “never had a failure with a mechanically bonded assembly. It’s always passed the requirements for brazing and castings. We’re still making that original PIU, 30–40 different assemblies for a variety of customers, and now we have the first bonded assembly in space.”


Doing Work No One Else Wants to Do

Besides revamping longstanding manufacturing processes, like replacing brazing with mechanical bonding, Command has also earned substantial business by taking on work that no one else wants to do. To be sure, this approach reflects Braswell’s intellectual curiosity and attitude, which in turn stems from his carpenter father. The elder Braswell taught George to never give up and lived that motto himself, working into his 80s after losing all but a $26 monthly retirement payment. But “never give up” is also a strategic business decision. Braswell figures that if he embraces each new challenge and works through the kinks he’ll lock in a relationship. So even if the first job isn’t profitable (and it often isn’t), Command will emerge as the sole source for repeat work. When the job comes back they’ll be more efficient at it and profitable. It’s an approach they’ve repeated many times, most recently with tantalum.


Blocking Subatomic Particles with Heavy Metal

Tantalum is a very heavy, hard, and rare metal, mostly used in tiny capacitors; it has the highest known ability of any metal to store electricity. It’s also used in some coatings and superalloys where its hardness and high melting point are needed. But it’s almost never used in the format faced by Command Technologies: sheets of pure tantalum, roughly 400 square inches in size, layering a block of aluminum.

A customer wanted a layer of tantalum to function as a radiation shield for a spacecraft. Another firm solved the problem of imploding a layer of tantalum onto aluminum so that it forms a stable chemical bond, a process so specialized that one such implosion costs $125,000. But someone then has to machine the entire tantalum layer flat and cut all the necessary mounting forms, which are mostly in the aluminum side, but include some through-holes. The first contractor failed. Command’s Sales Director, Lucy Boyd, didn’t want to touch it: “Too expensive. Too high risk.” Braswell, of course, accepted the challenge. “I said, ‘No, I want to machine it. I want to learn about it.’ ”

Here, one side of the support structure is milled at 14,000 rpm on a Mori Seiki NH5000 DCG horizontal machining center. Braswell favors horizontals for his high-volume work, owing to their power and superior chip handling. This particular machine also has a large pallet changer and is set up for 40 jobs.

It took two years of learning: Figuring out the best way to hold the part and developing special machining processes. (Command dedicates several CNC machining centers to this kind of R&D, an investment few shops could afford.) A key part of the solution was partnering with Linley Patterson of DGI Supply. Patterson helped analyze the problem and recommended a specialized 3 flute solid-carbide end mill with variable helix, unequal indexing, and a staggered core. Great end mill or not, the parts are so expensive and hard to replace Command won’t machine one if there’s a threat of a thunderstorm and a possible loss of power that might interrupt the cut. And they teleconference with the customer every week, the project is so hot. But as hoped, Command has emerged as the go-to shop for this exotic application.


Another Key to Winning Work: Risk Mitigation

Boyd explains that when she visits prospective customers now, she’s not really selling Command’s machining capabilities. “In this day and age you have to sell risk mitigation. You have to sell your strategy. You have to sell your business emergency plan. It’s no longer about craftsmanship. That’s a given. It’s business strategy now. It’s partnership.”

Why the focus on risk mitigation and partnership? Because “unfortunately, engineering is so skinny in the US. And nothing is inventoried anymore. It’s not dock to stock, it’s dock to line. Companies can’t stand any variation in meeting requirements. It’s made all of us grow as business people. Everyone on our floor understands business more than they ever thought they would coming into machining.” 

  


Cutting Risks through Vertical Integration This peak into the tombstone changer on the Mori

Over the years, Braswell became increasingly uncomfortable about sending parts out for specialized services. Besides the lack of scheduling control, the chances of damaging delicate tight-tolerance parts in transit was too high. So in addition to Command’s machining, EDM, CMM, and bonded assembly capabilities, he added chemical film deposition, powder coating, wet painting, and dye penetrant inspection. Each time Command added such a capability, they went through the certification process with each of the major defense contractors. They’ve also been certified under the comprehensive AS9100 standard. So parts produced at Command often go right into the finished product without any further inspection by the OEM.

As Boyd puts it, “It’s expensive to bring in all these processes in the beginning. But in the long run, once you’re approved by Lockheed, Northrop, Raytheon, you get a lot of that work. You help them mitigate the risk and you become a partner, not just another supplier.”


Communicating through Adversity Helps

Braswell’s background as both a machinist and a degreed engineer has helped from the beginning. He can communicate with the OEM engineers on their own terms and lead them to designs that will save money from the machining standpoint. That builds the kind of relationships that fuel growth. For example, when a large number of Smith engineers were laid off during the previous big downturn, they seeded many other companies who then brought their work to Command.

Braswell is also a big believer in the need to be up front about problems. “Meeting the requirement of your customer is the most important thing, and if you have a problem call them up! Don’t wait until it’s late and then call them. We call them beforehand if there’s an issue. In most cases they’ll work with you as long as you work with them. Communication is the best thing you can do. You cannot forget they are part of your team too.” ME 

 

This article was first published in the August 2014 edition of Manufacturing Engineering magazine. Click here for PDF.


Published Date : 8/1/2014

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