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Quality Scan: Smart Processes Can Enhance Assembly

  

To many people who have made their living supplying components, the growing trend toward consolidating suppliers and buying "modules" or assemblies rather than parts has come as a very unwelcome development. But, like it or not, the trend is well established and accelerating across a broad range of industries.   

It started in aerospace. At Boeing, for example, more than 90% of each aircraft produced is made by someone else, and the content per vendor is rising. It's very common for a Boeing Quality Control team to be resident full-time at major suppliers, where they are actively involved in resolving work flow and product-performance issues.

The goal at Boeing is to do final-final assembly in their facility, and little or nothing more. All of the "real" manufacturing is being pushed as far upstream as possible, as quickly as possible.

It didn't take the automotive industry long to see the financial advantages of this approach. But, what looked at first to be a strictly bottom-line-oriented effort to trim the number of suppliers turns out to be something else altogether.

Because it perpetuates bad design decisions and mistakes, the old "build-to-print even if it doesn't make any sense" model is inherently wasteful. Shorter supply chains put the supplier closer to the product's end use, and that opens up a lot of creative opportunities that did not exist in the old system.

One of the less obvious benefits of the move to upstream assembly is the freedom it gives to the supplier.The build-to-print model often locks the producer into an inflexible tolerance straitjacket that defines quality in terms of the number of zeros in the size tolerance.

The idea that ever-smaller tolerances automatically translate into ever-higher quality is an excellent example of the wisdom underlying the adage—"If the only tool you have is a hammer, pretty soon everything starts looking like a nail." Until quite recently, the ability to achieve tighter tolerance was the only tool available to improve quality. That's no longer true.

Quality is fundamentally an economic concept, not a dimensional or physical one. Quality is really a measure of the value the customer believes they receive from a product. The customer measures that value in terms of how well the product functions compared to how much it cost. The customer does not know, or care, how precisely the components of the product have been machined. What matters to the customer is that the product works as expected, and does what it promised to do.

And how does this relate to upstream assembly?

By handing over the physical manufacturing process to their suppliers, end users like Boeing and the auto companies open the door for those suppliers to creatively explore ways to deliver "quality" products.Ways that do not consist of simply adding zeroes to tolerance specifications.

One of those ways is the use of smart assembly systems that can recognize and compensate-for component variations during the assembly process. For example, a technology known as Signature Analysis compares the force/position signature of a specific assembly operation to the signature of a known-good operation to produce virtual clones of the known-good assembly with 100% assurance.

All of the elements of a smart system using this technology—servopresses with integral force/position sensors, PCbased CNC controls, real-time signature analysis software—are available off-the-shelf. Everything else required is essentially standard assembly fixturing built of standard components. And, signature analysis is only one of many smart assembly technologies available today.

With a smart assembly system, the actual size of the component parts becomes much less important, because the system can compensate for a broad range of variation and still produce 100% functional assemblies. It's often possible to open the acceptable tolerance range for component parts, and still meet stringent functional quality goals for the finished assembly.

The cost implications of that capability are both obvious and significant. But the advantages don't stop there.

For the traditional part supplier making the move to upstream assembly, the choice of a smart assembly system also can significantly smooth the transition. The system's built-in intelligence can help compensate for the lack of assembly experience within the supplier's workforce.

So, if you are a part supplier facing the prospect of becoming an upstream assembly source, the transition will be easier if you approach it as an opportunity rather than as a burden. Because, that is exactly what it is, an opportunity to use smart technology to give you a competitive advantage, and a healthier bottom line.

 

This article was first published in the May 2008 edition of Manufacturing Engineering magazine. 


Published Date : 5/1/2008

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