Sometimes I say “wax on” as I gesture. It has become a joke about the way I am constantly moving my hand in a circle as I describe the flow of people, equipment, processes and PDCA. It looks like I am channeling the sensei from Karate Kid, but the importance of the circle versus the line is no joke.
Operators walk down the line, pass the part to the next process or operator, and walk back to their start point empty-handed. Material handlers pick up pallets from the dock, put them into the warehouse, and return to get the next pallet with empty forks. Full trucks drop off their cargo and head home with an empty trailer or no trailer at all.
Empty hands, empty forks, and empty trailers are all waste. Traveling further than needed with 50% utilization is not the concept of flow, or of lean, or a formula for business success.
The characteristics of a circle help to conceptualize and remember important aspects of flow. And it is fun.
1. Start and end are close together. Circles are continuous. There is no start, and there is no end. If we must think in terms of start and end, consider that they are very close together and that they can be anywhere in the circle. The operator in a cell should finish the process and start the next cycle seamlessly, and with little or no movement or empty hands. The material handler (water spider) is dropping off and picking up with each stop and the move from last stop to supermarket to next stop is very short. The truck driver drops a trailer and immediately hooks on to the next load for the return trip.
2. Do not cross the stream. With the start and end close together, it is possible to have the path cross itself. There will be trouble where it crosses. Water, electricity and parts will follow the path of least resistance. In a process where the flow crosses, is where parts will skip a process. If it is a route or operator path, it is where collisions occur or where we have congestion and bottlenecks.
3. Make it smaller. When you have a standard, repeatable route or path that has the start and end close together and does not cross itself, make it smaller. Improvement comes from the combination of distance and utilization. The first two characteristics are to improve utilization, now reduce the total distance. Work stations should be less than 0.8m (30”); analysis brings the highest volume products in the warehouse closer to the point of use; having suppliers within a 20-minute drive allows just-in-time delivery of large high-mix, low volume assemblies.
4. Circular, but not circles. A circle is rarely the optimal path. The benefits of the “U” shaped cell are well known, but any shape that has the start and end close together, does not cross and minimizes total distance is a winner. The advantages of having a short distance from one side of the path to the other include being able to rebalance work load, ability to add or subtract resources to match demand, and not having to travel the full route when not required.
A straight line of processes from receiving to shipping is a definite improvement over chaos, and it looks sexy on the CAD drawing, but it almost guarantees that even as the parts and processes may have minimum travel, that the people and material handling equipment will be traveling empty half the time. The route map with nice arrows on a map showing delivery routes is exciting, but has to have arrows coming back.
Circles are better than lines. Wax on.
Robert H. Simonis is the senior operations consultant at KCE Consulting LLC. Robert has over 20 years of leadership experience including 10 years in manufacturing management and 10 years of global responsibilities in automotive, electronics, machining, logistics, and complex assembly operations, and is recognized as a lean enterprise expert. Email [email protected]com or www.kceconsulting.com.