Cartwheels

We may think the wheel has increased our ability to work, but it really has increased the waste we create

Published: Tuesday, February 28, 2017 - 13:02

Most often when we think of a wheel, it’s in the context of transportation, one of the more obvious and ever-present of the 7 wastes in lean. In fact, the first likely use of a wheel and axle was not for transport but for processing—actual work.

According to the Smithsonian, the potter’s wheel dates to 3500 BC. The wheel and axle weren’t used for human transport (the chariot) for several hundred more years; the idea of carting material apparently took several millennia after that! The wheelbarrow was invented around 100 AD in China, and it took another thousand years more for it to appear in Europe.

From a human standpoint, these conveyance devices are designed to reduce strain. In a technical sense, it can be said they multiply our capability to do work, at least the force-times-distance kind of work: W= f x d. The problem is that although conveying material on wheels is embedded in our thinking as an improvement over manual transport, it’s actually a mechanization of waste. We may think the wheel has increased our ability to do work, but it really has increased the amount of waste we can create. Odd.

Over the centuries additional wheels were added to the basic cart, enabling conveyance of even more material with less work [sic] in a single trip. Then, in 1936, the invention of the shopping cart at Humpty Dumpty supermarkets became the prototype for more recent improvements to conveyance: a four-wheel, multi-level steel wire cart. This invention replaced a hand-carried basket, enabling shoppers to gather all groceries in a single pass. The shopping cart, however, also required wider aisles and larger checkout counters.

Then the aisles were widened again, this time to accommodate pallet loading of the larger amounts of material needed to accommodate a new concept: economic order quantity (EOQ). Why buy just a little, when you can have so much more in an economy pack? Carriages became larger still to accommodate bulk quantity shopping. All of these innovations were intended to make it easier for the customer to buy more—and, of course, to encourage them to buy more.

There are more than a few parallels in industry. Automatic guided vehicles (AGV), pallet jacks, forklifts, and conveyors are all “improvements” on the basic cart. These machines typically require wider aisles, deeper and higher shelving, new training, maintenance, and of course, more space to park the machines—kind of like the tail wagging the dog. Too often, rather than rethinking the cause of the waste, we automate around it. Shigeo Shingo referred to these as “superficial improvements.” An AGV mechanizes the waste of transportation; an automated storage and retrieval system (ASRS) facilitates the waste of storage. Worker strain may be reduced by a superficial improvement, but the actual waste remains and sometimes even increases.

A stockroom manager, for example, lamented to me recently, “I have less people now, but it takes longer to kit a job than when we did it manually. The machine is a bottleneck, and the factory waits for parts.” Unfortunately, these expensive superficial improvements become sunk costs, hard to undo because they are depreciable assets. Thank you, management accounting.

One more insidious reinvention of the wheel is the stationery, or almost stationery, wheel. To the casual observer, these are the wheels that are on a cart that appears as if it’s for transportation. In reality, this cart never moves except to move out of the way. Moveable storage becomes an option when material staged in front of a process has overflowed to a point that it must be staged in the aisles; funny that this is called “work in process.” Of all uses or abuses of the wheel, this one is tops on my personal list: the appearance of conveyance. We assume that if there is a wheel, then there must be movement. Shingo’s comment that the “The worst waste is the one we cannot see” comes to mind.

Here is an improvement exercise for you to try in your own facility. First take an inventory of carts and answer these questions:
• What is the total number of carts?
• What is the total floor space they occupy?
• How many are actually used for conveyance?
• How many are really only for storage or are kept on hand in case of storage overflow?
• How can you reduce each of these numbers by half?

Please let me know how much production space you liberate.

About The Author

Bruce Hamilton

Bruce Hamilton, president of the Greater Boston Manufacturing Partnership (GBMP), brings hands-on experience as a manager, teacher, and change agent. Prior to GBMP, Hamilton led efforts to transform United Electric Controls Co.’s production from a traditional batch factory to a single-piece-flow environment that has become an international showcase. Hamilton has spoken internationally on lean manufacturing, employee involvement, continuous improvement, and implementing change. Also, he has contributed to numerous texts ranging from visual control to variety reduction. Hamilton’s blog, Old Lean Dude, is an ongoing reflection on lean philosophy and practices, with an emphasis on keeping good jobs close to home.