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How to reduce subjectivity in continuous improvement

At a custom fabricator, does a certain inspection activity, one that the customer doesn’t require, add value? Some say it does, because it ensures quality and helps standardize procedures for a job shop’s diversified customers, many of which do require such inspection. Others may say that such inspection represents overprocessing, a classic waste of lean manufacturing. So who’s right?

According to Rajan Suri, those are good questions, but in the scheme of things, it may not matter all that much. That’s a point he drives home in his new book, MCT: Quick Reference Guide. In the 1990s, Suri developed quick-response manufacturing (QRM), an improvement method suited for high-product-mix manufacturing. He’s the founding director of the Center for Quick Response Manufacturing at the University of Wisconsin-Madison, and he has a message: Time really matters—in the broadest sense.

So if time matters so much, why does the debate about inspection and potential overprocessing matter? It’s because of MCT, or manufacturing critical-path time. Suri defines it as “the typical amount of calendar time from when a customer submits an order, through the critical path, until the first end-item of that order is delivered to the customer.”

Debating whether a certain activity adds value really misses the bigger picture, which Suri says is made clear by MCT, which divided simply into “white space” and “gray space” time. The gray space is when something is happening to the order, while the white space is when nothing whatsoever is happening to it. This time is a waste, and it’s hard to argue with that, considering no activity related to the job is taking place.

When a manufacturer fulfills an order, time passes, and people either spend time working on that order (gray space) or they don’t (white space)—period. In fact, when calculating the gray-space time, Suri advises that in some situations, shops shouldn’t sweat the details, be they slight variations in labor inputs, machine cycle time, or anything else. When he maps out a typical MCT in a bar chart, with blocks of white peppered with slivers of gray, you can see his point immediately: In most manufacturing environments, a lot of time passes when nothing whatsoever happens to the job, and finding out why can help you get the biggest bang out of your improvement buck.

About the Author
The Fabricator

Tim Heston

Senior Editor

2135 Point Blvd

Elgin, IL 60123

815-381-1314

Tim Heston, The Fabricator's senior editor, has covered the metal fabrication industry since 1998, starting his career at the American Welding Society's Welding Journal. Since then he has covered the full range of metal fabrication processes, from stamping, bending, and cutting to grinding and polishing. He joined The Fabricator's staff in October 2007.