Lean manufacturing is about eliminating muda, or waste, while increasing poke-a-yoke, which means mistake proofing, while always striving for kaizen, or continuous improvement. In a nutshell, lean manufacturing is about examining every process in the company to eliminate nonvalue-added activities.
Traditional manufacturing philosophies stress high utilization of machinery and manpower with little concern for cycle time or manufacturing waste. The lean manufacturing philosophy focuses on creating greater production efficiencies through maximizing value-added activities, while minimizing waste.
Vincent Bozzone in his book, Lean Manufacturing for Job Shops, says that "Although some people believe that quality and product are opposites that cannot co-exist, this is not true. A company does not have to sacrifice quality to meet output goals. In fact, the opposite is more often the case. A shop that is operating at a productive pace will generally be able to meet quality goals more consistently than one in which the pace is disjointed, lackadaisical or chaotic."
Some of the quality problems that can be addressed are transportation damage, breakdowns vs. preventative maintenance and setup adjustments. Solutions include one-piece flow, cellular manufacturing, pull processing, batch reduction, plant layout and teamwork.
Traditional measurements, according to a white paper by Excel Partnership Inc. (Sandy Hook, CT), such as return on investment, labor reporting, variances and absorption cannot cohabitate with lean manufacturing. "Cost accounting is important, but not on the shop floor....Shop measurements must be real time and useful to flow. That means product velocity, quality, takt time and machine utilization must be the driving measurements." the paper says.
In many ways, lean manufacturing fits hand-in- hand with Six Sigma in that both processes focus on continuous improvement, customer improvement, and making decisions based on data and facts generated by carefully analyzing the plant.
Lean manufacturing takes aim at overproduction, inventory, transportation, work-in-progress, defect reworking, and underutilization of the talent and knowledge of the employees, according to the Manufacturing Extension Partnership (MEP). The nationwide network, sponsored by the National Institute of Standards and Technology, is made up of not-for-profit centers in more than 400 locations nationwide, with the sole purpose of providing small- and medium-sized manufacturers with the means to improve how they build their product.
According to MEP, typical benefits to those manufacturers who embrace lean manufacturing systems and concepts include:
Joe Paxton is a research scientist at the Alabama Technology Network (Huntsville, AL), an MEP affiliate located on the campus of the University of Alabama. The first step, according to Paxton, is to generate a value stream map, which is essentially a snap shot of the current operation. "I look to see how material flows and help them [manufacturers] develop a future state of what they want production to look like," he says. "We want to improve quality, reduce defects and scrap material, and increase product flow and throughput."
This often includes flexible manufacturing, such as cellular manufacturing design, with the ultimate goal of one-piece manufacturing. Cellular production allows companies to produce smaller runs of products more cost effectively. Normally designed in a U-configuration, a workcell brings all the processes to build a particular product together in a uniform and efficient manner.
"We want to go from one part to the next. We try to set up the machine so the company doesn't have to change anything," says Paxton. "A lot of times we try to help without them having to invest in a lot of capital."
Companies of all sorts are finding that lean manufacturing makes for more efficient production. Lockheed Martin Corp. and The Boeing Co. will use lean manufacturing techniques in developing the Joint Strike Fighter. The National Steel and Shipbuilding Co. uses lean to build ships. Dell Computer Corp. uses lean manufacturing to build computers. For Dell, lean manufacturing has helped them weather an economic downturn, according to the Washington Post. The newspaper says that Dell can respond to the slumping computer market faster than its competitors because of its lean manufacturing structure. The company works in a traditional pull scenario; it makes computers only after customers have placed their orders, allowing it to carry less inventory.
Another example is George Guenzler and Sons (Kitchener, Ontario, Canada), a furniture, chair and stair part OEM manufacturing company. The company recently completed a four-year, multi-million dollar renovation that included a new 60,000-square-foot factory, new computer numerical control machinery and other dedicated machines, plus a new manufacturing philosophy that focuses on increased throughput, reduced inventories and smaller batch sizes.
"The old thinking was batch production," says company president Norbert Englisch. "Today, we don't want massive inventories on the production floor. We want to adjust our production so it all comes together at the right time and at the right place to satisfy our customer's requirements."
In implementing synchronous management, Guenzler has looked to identify bottlenecks and eliminate material-handling steps by reducing the number of machines required to do tasks.
By doing these things, Guenzler is able to more efficiently produce smaller batches on a just-in-time basis. This in turn results in less need for inventory of raw material and finished products at Guenzler and its customers' facilities. "We realize inventory is very costly," says Englisch, "so we want our customers to receive product they require in the quantities that are most useful for their production requirements."
To get the most out of lean manufacturing techniques, the experts say that the knowledge of as many people as possible should be harnessed. Teams should be established that are made up of members from a variety of disciplines from design to quality, manufacturing to shipping.
"When we talk about lean enterprise, we are talking about everything from suppliers through manufacturing to delivery and to the end customer. That is the whole enterprise. It is not just one segment such as manufacturing," says Dr. Thomas Greenwood, director, Lean Enterprise Forum, University of Tennessee (Knoxville, TN) in a CD-Rom introduction to his organization.
Teamwork was evident at Raytheon Systems Corp. (Dallas). In 1997, the company was awarded the contract to build 13 prototype Long Range Advanced Scout Surveillance Systems (LRAS3).
Paul Zimmermann, lead systems producibility engineer at Raytheon, says that 85% of all manufacturing costs are determined in the early concept stages of design, and he says his engineers were determined to reduce production costs as much as possible. Upon contract approval, an integrated product team (IPT) was assembled from many departments including design, quality and manufacturing to implement concurrent engineering approaches. Their mission was to develop, as early as possible, product design directions that met the cost, schedule and performance requirements of the U.S. Army.
The system incorporates advanced second-generation forward-looking infrared, a day video camera, a laser range finder and a global positioning system. A unique design challenge was the cover assembly for the global positioning system interferometer subsystem (GPSIS). The system antennas require a flat ground plane with exact tolerances that were difficult to achieve with traditional casting or sheet metal processes, according to Zimmermann.
The other requirements for the GPSIS cover included: thermal isolation of the circuit card assemblies from solar load, lightweight and rigid construction, an environmental seal on antennas and sight housing, a conductive ground plane to shield the system from electromagnetic interference (EMI) and radio frequency interference and minimal tooling costs.
The team electronically designed seven configurations of the GPSIS cover using Design for Manufacture and Assembly software from Boothroyd Dewhurst Inc. (Wakefield, RI) The software guides designers through a systematic analysis of products with the aim of consolidating parts and eliminating assembly difficulties. Being able to do these design changes electronically let the team work out any bugs prior to production and save an estimated $2 million over the life of the program. For instance, the original concept for the cover consisted of a machined casting with insulation foam bonded to the bottom. The problem with this design was that the casting would be too heavy and it would require a long lead time and excessive tooling costs. It also presented a direct solar load to the circuit card assemblies and exposed the system to what are called foreign object debris.
The final design was made from a foam core that was used as a structural member of the composite cover with aluminum top and bottom skins. This construction eliminated foreign objects from getting in and protected the electronics from solar heat. It reduced the weight of the cover while at the same time providing rigidity. As for product quality, Six Sigma for the GPSIS cover design improved from 3.64 for option two to 4.83 for option seven, and defects per unit improved from 6.62 to 0.17. These quality improvements account for a predicted product cost savings of 55%. "The real benefit is defect avoidance," says Zimmermann. "Reducing defects by 6.45 defects per unit decreased repair and rework by an estimated 97%."