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When it banishes in-line inspection, Lean has gone too far.

“Look for the ridiculous in everything and you will find it.” – Jules Renard (1860)

There are a lot of annoying things in this world. People who think they can drive and carry on a phone conversation at the same time; airport security that is really just a placebo and hence a shocking oxymoron; drivers who putter along but refuse to budge from the fast lane; cellphones that don’t work; infants with lungs of Olympic swimmers who scream throughout long flights. The list goes on.

Our industry is fraught with strangeness, too. Sometimes good intentions go astray, especially when seasoned with misconceptions.

Lean manufacturing is a concept that has gained momentum the past few years. Many electronics manufacturers have gone to great extents to make their factories “lean, mean, circuit board assembly machines.” Combine Lean with mean, however, and the results can be substandard. One disturbing approach we’ve observed often has been the lack of inclusion and even the elimination of in-process inspection in the name of Lean. “No perceived value added” and “it slows down the process” are the rationales given. Nothing could be further from the truth. This is not Lean, this is “Anorexic Manufacturing” and it is dangerous.

In-process inspection is essential. It catches defects as soon as they occur, allowing manufacturers to immediately rectify the source of the problem. I am a big fan of post-print inspection. Since 50 to 60% of assembly-related defects typically occur during printing, it is logical to perform post-print inspection. This can be done, to varying extents, either on the printer or on a dedicated piece of AOI equipment designed for that purpose. The latter can be either in-line (between the printer and placement machine) or as a shared, standalone unit used on an acceptable quality level (AQL) basis. Either way, this methodology will definitely help yields. With proper utilization schemes, post-print inspection will not be a bottleneck in the process. If you haven’t looked at this equipment in a while, you have no idea what you’ve been missing.

What about placement? While not as much a contributor to overall process defects as printing, misplaced components do happen. How many lines have you seen with someone standing at the conveyor between the last placement machine and the reflow oven, tweaking components. Wouldn’t it be better if the root cause of the misplacement were eliminated? Proper maintenance and programming will go a long way. Beyond that, the biggest problem with placement is the operator doing setup. A lot of effort has gone into making sure the right component is put in the right feeder location (per the program): smart feeders, bar-code verification, on-line parametric testing/verification and, most recently, RFID tags (truly “EZ-Pass” for pick-and-place).

Most users opt to make their initial AOI investment in post-reflow inspection equipment. A good investment, indeed, but I feel strongly about accompanying it with some form of post-print inspection. The argument is, end-of-line AOI will catch errors generated in all three process areas. But that scenario means rework. Think BGAs. However, post-reflow AOI is important and powerful. The equipment has come a long way in the past few years. A stronger infrastructure – much higher resolution vision equipment and much faster processors for handling very complex algorithms – has led to powerful on-board and in-line systems. In many cases, AOI is supplanting ICT as the former is superior in programming ease, coverage and ECO response. AOI won’t make ICT obsolete, but it is a good direction to for your line to go.

Can AOI be considered non-value added? Only by the unenlightened. Imagine our dismay when, a short time ago, we audited several lines for a Fortune 50 OEM at which the Lean manufacturing “guru” had the AOI (post-print and post-reflow) equipment removed in favor of x-ray inspection after the entire assembly was completed. This was a high-volume manufacturer with well over 100 assemblies in queue awaiting x-ray “inspection” (such as it was). Bear in mind, the company had machines in place and took them out. Machines that most users would kill to have. Hence, the revelation of Anorexic Manufacturing. Needless to say, our summary report including a reading of the riot act – the section that pertains to the stupidity of not using AOI, especially when you have it.

We’ve seen a lot of very innovative and powerful concepts implemented via Lean manufacturing – particularly in manual flow lines. We’ve also seen programs with 50s style time-motion techniques that result in manual operations resembling that episode of I Love Lucy where she worked in the candy factory.

Lean manufacturing is a good concept and one that fits our manufacturing mantra of “smaller, faster, better, more economical.” But the most-effective Lean manufacturing intelligently and strategically uses the latest and best manufacturing technology combined with quality and management systems that are efficient, effective and humane. Remember, we are all in this together!

Phil Zarrow is president and SMT process consultant with ITM Consulting (itmconsulting.org); itm@itmconsulting.org. He still bears the scars, physical and mental, of reflowing convection/IR ovens. His column appears semimonthly.