Creating Lean Workstations
Although lean workstations appear much the same as their more traditional brethren, they are, in fact, inherently different.
"With a lean workstation, everything must be choreographed like an orchestra, so that every movement has a purpose," says Rick Harris, president of Harris Lean Systems Inc. "It requires a new way of thinking. Traditionally, most workstations were laid out for the material handler's convenience, not for the value-adding operator."
Assemblers creating lean workstations should focus on critical operator issues, such as safety, ergonomics, and getting parts and tools in place, so they can be located quickly and efficiently. A lean workstation puts all the required assembly materials at the operator's fingertips. They are strategically positioned so assemblers can reach for tools or parts without even looking.
Unfortunately, workstations are notorious for being sources of waste. This is because tools and parts are often located in such a way that an operator needs to walk or reach around or over something to get what he needs-a situation made all more problematic when dealing with heavy objects that can cause muscle strain.
Quarterman Lee, president of Strategos Inc., believes it may be time for engineers to resurrect the principles of motion economy that were codified in the 1930s and then successfully applied during World War II. "In its fascination with computers, American industry pretty much forgot about motion economy during the 1960s," Lee says. "When lean manufacturing was re-imported from Japan, motion economy was left behind.
With this in mind, manufacturing engineers need to become familiar with the basic principles of ergonomics. For example, it's important to have an understanding of the three primary ergonomic operating zones: the optimum work zone, the optimum grab zone and the maximum grab zone. Parts presentation, the assembly sequence and tool organization should all be limited to the optimum zones as much as possible.
"It's important to remember that people move in arcs, not straight lines," says Chris McIntyre, president of Ergonomics at Work Inc. "Too many workstations tend to be designed as a rectangular desk. As you move parts and tools further out from the side of the body, they become harder to reach."
Remember that ergonomic reach zones extend both vertically and horizontally, and tasks performed below shoulder height are less fatiguing than those that take place higher up. Routinely used tools and parts should be placed within horizontal reach and work zones whenever possible. If reaches become excessive, engineers should consider splitting the assembly operation into two separate tasks.
Also, whereas in a traditional workstation, parts and tools tend to spread out horizontally across a work surface, in a lean workstation, there is a more vertical presentation so tools and parts are closer to the operator. "This reduces space and wasted time spent looking for materials," says Eric Dotson, general manager for Treston.
Throughout this process, keep in mind that it may be necessary to determine whether it's more important for operators to be able to access tools or parts more efficiently. In a high-volume situation, for example, the key may be easy access to the different components that go into each assembly. On the other hand, in a low-throughput environment where a single operator may be performing a number of different operations on a single workpiece, access to assembly tools may be the priority.
Finally, don't forget your operators. John O'Kelly, president of Newcastle Systems, suggests that assemblers carefully examine how a procedure is being performed and ask operators a series of questions, such as: What are your pains or annoyances? How does the workstation fit within the facility environment? What happens before and after the product arrives at the workstation? What do you want to change about the work area? What do you like about it?
These factors affect the size and shape of the workstation, the choice and placement of accessories, and whether the workstation should be mobile or stationary. "Document the different tasks that need to be performed at the workstation and the accessories that may be able to provide relief. Use the information from the operator to find modular workstations that provide variety in surfaces, configurations or sizes, such as height, depth and width," O'Kelly says.
Put together a mockup of the workstation and let operators "try it on" for size. "Many engineers...fail to do a mockup of the workstation, using cardboard, Styrofoam and PVC pipe," says Harris. "We always invite the operator in during this simulation. He becomes the king. We put him in his work envelope and let him evaluate it."
While working with your operator on the shop floor, don't hesitate to pick up the tools and trying performing the assembly yourself. "Engineers need to step in and do the task to get a better perspective," says McIntyre. "Try it yourself. Try working at the workstations you design. Ask questions such as: How much force do I have to use? What position do I have to use?"