Design for Assembly: taunting from the manufacturing floor

When it comes to design, sometimes what works in the uninhibited realm of solid modeling (where just about anything is possible) doesn’t make a bit of sense in the real world. A good design engineer knows this from experience. A bad design engineer may be lacking that same experience and may be in need of some hard feedback in order to improve. While you could pore over Powerpoint error count metrics and root cause analyses to systematically highlight specific design deficiencies, there’s a far simpler way: a good old-fashioned hasslin’ from “Bulldog.”



The legend

His given name was William, at least I think it was, but he chose to go by the more colloquial alias of “Bulldog” and his company badge confirmed that it was somehow not a nickname. Bulldog looked like hell, like a grizzled old prospector crossed with a post-apocalyptic warlord. It was easy to imagine his time off involved casually punching bears, long walks through factories full of burning tires, and breaking lesser engineers over his bad knee. He swore profusely and smoked like a cigarette factory. His motto was writ large on an oil-stained mural proudly taped to the back of his toolbox on the hangar floor:


Above all else, however, Bulldog was a damn good aircraft installer, a true artisan. Probably one of the best. And he knew it. Over the years, he had seen just about everything and had managed to profusely swear down several generations of, what he termed, “those $%@# engineers.”

Adventures in first article liaison

One of the earliest jobs in my career involved a facility with onsite aircraft assembly and installation work which benefited greatly from a strict policy: the original design engineer was always responsible for their first article liaison. While this policy ensured design intent was properly communicated downstream, it also had a more lasting benefit: you learned through real feedback when your stuff worked and when your stuff didn’t. And when stuff didn’t work, that meant a half-mile long march down to the hangar floor to respond to squawks. Every one of those marches was an opportunity for someone on the manufacturing floor to give an engineer the what for.

This is how I would meet Bulldog.

Especially hilarious was the fact that I was a green co-op at the time (a non-degreed engineer-in-training on internship between semesters of school) with authority slightly less than that of a mild fungus. He would look at me, amused at the fact that I was likely younger than many of his grandchildren, and quickly expressed his particular disdain for unnecessary complexity. Say, for example, spelling or pronouncing my last name. So along with the help of the rest of the manufacturing floor I was bequeathed with an alternate part number. I was to be Ed Lamborghini. As in

Oh for $%@# sake, here comes that $%@# engineer, Ed Lamborghini.

He would then proceed to dismantle everything he didn’t like about the particular assembly I was working on using a finely crafted barrage of chained expletives for emphasis. And the scary part: he was right. And that meant an opportunity for learning.

Design for Assembly

Bulldog’s well-intentioned hazing and verbal abuse was believe-it-or-not a compact form of Design for Assembly. Design for Assembly accounts for both human and machine factors in assembly, including workflow, manufacturing capability, cost, and opportunities for automation. Design for Assembly is about taking form, fit, and function beyond the context of a single part and into the interaction of multiple parts in a more complex machine.

Simply put, it’s about putting things together more reliably by considering:

  • Accessibility: Can someone actually get in there and do it with the tools they have. You’d be surprised how quickly you can lose a sense of scale when staring at a CAD design for too long without physical reference.
  • Fasteners: Using the right type of fasteners, considering access and clearance.
  • Part Orientation: Understanding how parts are indexed and positioned off other parts and identifying and eliminating opportunities for confusion, misalignment.
  • Simplification: Knowing when it makes the most sense to combine or separate parts for sake of easing or enabling assembly.
  • Tooling: Knowing when and where to cost effectively exert more exact control through tooling aides.

Design for assembly is most effective when there’s a closed feedback loop between the design authority and the manufacturing authority. Something beautifully illustrated by that first article policy and Bulldog’s particular enthusiasm.

An uneasy peace

Over time I would learn to pay special attention to Bulldog’s particular passion for Design for Assembly, and soon enough I would manage to earn his respect. I wouldn’t go so far as to say we were friends, as he’d probably sooner stab me in the eye with one of his larger screwdrivers than begrudgingly admit any sort of minor pleasantry to an engineer, his sworn enemy. But he certainly swore slightly less and stopped hasslin’ me so much, saving his wrath for the next poor engineer.

Such hard no-nonsense lessons are critical to building the engineering experience necessary to properly differentiate good design from bad design. Building such experience is certainly harder these days with manufacturing often outsourced, including artificial separation between design and manufacturing authority. Perhaps Bulldog can come to the rescue.