According to a definition used by the U.S. Defense Acquisition University, lean manufacturing refers to “an evolving … process of production covering the total enterprise, embracing all aspects of industrial operations … and including customer-supplier networks, which is governed by a systemic set of principles, methods and practices.” Just as it is with more traditional approaches to manufacturing, automation is frequently a component of lean manufacturing. Key lean principles include getting it right the first time, waste minimization, continuous improvement and flexibility. And, both lean manufacturing and automation share a focus on accomplishing more with less.
Unfortunately, few organizations recognize the potential role fastener selection can play in helping achieve lean manufacturing and automation goals.
Joe Greenslade, director of engineering technology at the Industrial Fastener Institute and a 38-year veteran of the fastener industry, says companies often make mistakes when trying to optimize operations and improve efficiency by failing to consider the role of the fastener. “The fastener industry is continually coming up with innovations that simplify the manufacturing process. Manufacturers are always trying to squeeze costs but often fail to look at alternative fastening methods for solutions.”
Companies often put extensive efforts into designing components and subcomponents and only then, at the end of the process, do they select the fasteners. But that can be short-sighted because the optimum fastener can make an assembly operation much faster and raise quality, too. If you are really trying to achieve optimum efficiency in assembly and manufacturing, Greenslade suggests putting time into thoroughly researching fastening options and talking to potential suppliers. “OEMS should call in the very best fastener producers to review their designs ahead of time as part of a design for assembly approach,” he says.
Furthermore, says Greenslade, if you are going from conventional to lean manufacturing you might want to consider selecting proprietary fasteners as part of the transition. For example, he says, combined screw and washer assemblies can reduce the number of components being handled and simplify assembly operations, whether by hand or machine. “And the use of thread-forming screws, where they create matching threads as they are assembled, is not only faster but it eliminates the possibility of cross-threading and can give you a more secure joint,” he says.
In the case of products such as home appliances with substantial use of sheet metal, there is a growing incentive to reduce the gauge of stock – but this smart cost-saving step can make conventional fastening systems prone to failure. “It can get to the point where standard sheet metal screws no longer work well and that is a place where proprietary designs can help, too,” says Greenslade.
“Proprietary screws might cost double or triple on a per unit basis but if you get a more secure assembly with less labor, there is actually a tremendous saving,” he says.
Furthermore, he says, there is an increasing number of alternatives to threaded fasteners for some kinds of assemblies including hook and loop (better known by the trade name Velcro®) and a wide range of adhesives. “That’s why I’m saying designers should stop, back up and look at how things will go together before they finalize their designs. Unfortunately, these things are usually an afterthought, which means companies are often saddled with ongoing, unnecessary costs,” he says.
Likewise, says Greenslade, rivets aren’t used as often as they could be. People are focused on threaded fasteners, which are great if you want something to be serviceable, but many assemblies aren’t intended to be serviced so rivets, clinch nuts and other fasteners that work with a simple punch as opposed to a carefully gauged torque can be great alternatives.
In conclusion, he says, the offsetting cost in labor savings usually outweighs the difference in the cost for proprietary fasteners.
“You can go through college and even get a Ph.D. in engineering and probably not have more than three class hours devoted to fasteners,” says Greenslade. “The fasteners typically amount to something like three percent of the total cost of a typical assembly but the impact they have on assembly and quality is way out of proportion to that cost.”