The Robust and Reliable Job Shop
Going Lean Requires More than the Traditional Tools
by Matthew Jaster, Associate Editor
An optimized workflow from a forging operation that keeps the highest volume operations closest together to minimize wasted travel (courtesy of Shahrukh A. Irani, OSU).
"Once a job is first begun, never stop until it's done, be it big or be it small, do it right or not at all!" Ardilla Womack, mother of James Womack
There's both rhyme and reason to incorporating lean strategies on an assembly line. On any assembly line you'll find a particular workflow where everything has its place and the day-to-day job requirements remain consistent. This is why lean manufacturing and the just-in-time (JIT) philosophy originally developed with the Toyota Production System (TPS)—the objective being to make automobiles in the quickest and most efficient way possible. "The idea was to create more value with fewer resources, fewer errors and fewer product defects," says James Womack, senior advisor for the Lean Enterprise Institute (LEI) in Cambridge, Massachusetts.
Lean manufacturing, does not however, lend itself so easily to the job shop where every day is different and every order is unique. "If you're running a job shop where you never do anything the same way twice, you're going to have a more difficult time utilizing the tools that have made lean manufacturing such a success on the assembly line," Womack says. "That's not to say that it can't be done, you just need to be a little more creative in your approach."
Dr. Shahrukh Irani, associate professor, Department of Integrated Systems Engineering, The Ohio State University, agrees. "There's an extreme volatility in incoming order demand in job shops, larger number of designs, a wider customer base and complex production control, scheduling and shop floor control," Irani says. "In their enthusiasm to implement lean in job shops, they are forgetting that when it comes down to doing the implementation, the tools are where the mistakes are being made. Yes, you can empower the workforce and invest thousands in workforce training, but at the end of the day, neither the employees and surely not the higher-paid executives and managers, are doing what it takes to make lean work," Irani adds.
"The fundamentals of lean are universal with flow and pull distinguishing features of the system," says Dustin Ott, global manager, operational excellence, Boart Longyear. "Job shops follow the same principles but adapt them to fit the unique circumstances inherent in their businesses. All job shops share the common problem of variable cycle times and variable routings."
So is it possible to achieve the same end results in a job shop that lean manufacturing provides the assembly line?
"At first, many lean thinkers believed that there was no conceivable way to develop a product focus in job shops," Womack says. "It turns out there are plenty of product families to work with including categories like large, medium and small as well as hard and soft. You just had to know where to look to find them."
"It is essential that job shops embrace the philosophy and principles of lean and carefully select a manufacturing strategy that suits them," Irani says. "If the goal is to release orders into the shop only when there is available capacity on the workcenters needed to produce it, then that variation of pull scheduling is not going to be achieved by putting some kanbans on parts that constitute only 10 percent of a gear shop's business. That is bogus lean because a kanban system is a lean tool that works on the basis that each process on a production line pulls just the number and type of components the process requires, at just the right time. No jobshop is just one production line! Instead, what really is needed is that the entire production control and shop scheduling system work. When that is achieved, visual management can be done by displaying electronic schedules at certain locations where strategic buffers are being maintained, allowing material handlers and expeditors to know which order is ready to be moved when to which workcenter next, etc."
"Machine shops have traditionally focused on machine utilization and mastering the conditions required to increase cutting speeds. Reducing the value added time addresses only a small portion of the output equation. The result has been the overproduction of materials and it manifests itself in the form of stagnation of work and no flow," Ott says. "So the first step and the highest hurdle to get over is to truly believe that overall efficiency is more desirable than point efficiency."
Ott continues, "Getting to flow in job shops means that you're going to need to buy or build simple dedicated pieces of equipment that are going to be underutilized. That is why they need to be low cost. I'm talking about grinders, blasters, plating modules, presses, washers, tempering units, stamp machines, polishers, painting booths and packing stations etc. When I mean small I'm talking about a footprint no wider than your shoulders. Within cells we've co-located even expensive equipment including everything from induction units, robots, PLC's and multiple CNC's."
If a manufacturer can get over the first hurdle by moving to a cellular concept then the next hurdle is to increase the capability and stability of your workforce to enable flow.
"I call this concept 'base isolation," Ott says. "Just as modern structures in areas prone to earthquakes have design mechanisms that allow the foundations to move independently from the main body of the structure. These mechanisms absorb shock; job shops require a similar structure. Most small job shops already have this capability but the idea is to have people who can move with the product as its individual sequence requires. The Japanese call it shojinka but a key feature is that operators have job skills that are aligned sequentially. This enables the operator to move the product FIFO (first-in, first-out) in an unobstructed way without queuing. It also allows for skipping unnecessary processing requirements. The next step is to choose the method of processing and it all depends on your capabilities. A good place to start is to use a method I call bump. The idea is that once the last person in a cell has completed their work cycle, they move back upstream until they encounter an operator, regardless of where the product is in the processing cycle. The product is then transferred from one person to another with the empty handed operator now moving upstream to "bump" the next person and so on. Note that the holy grail of lean production for a job shop or the ideal ratio of work to people is now 1:1," Ott adds.
The 21st Century Lean Job Shop
So how should the lean toolbox change in a job shop? Lean and Six Sigma are simply scratching the service, according to Irani, and a job shop considering these strategies would also benefit from the continuous improvement initiatives found in Theory of Constraints (TOC). "Goldratt, the author of The Goal, looked beyond cost reduction by focusing on business growth and instead of material requirement planning (MRP), using Finite Capacity Scheduling to ensure on time delivery of orders," Irani adds.
Another consideration is to look into JobshopLean, a method originally developed at The Ohio State University to reduce production lead times for aerospace and defense applications that can be applied in most job shop settings. "JobshopLean allows job shops to embrace technology-aided work execution, something that is a-given in the high technology and Internet businesses but is often ignored in the manufacturing sector," Irani says.
The standard Womack-Jones Lean Thinking Process can be applied in any high-variety low-volume (HVLV) jobshop. The absolutely essential first step that a jobshop should take to become lean is to reduce and simplify the material flows in their facility by using Production Flow Analysis and Design for Flow Manufacturing. JobshopLean consists of a range of strategies that help to reduce the flow complexity of a jobshop in an attempt to achieve the linear and unidirectional flow patterns that are characteristic of a Toyota assembly factory. All of these strategies exploit knowledge of the different part families in the product mix and the resources shared between these part families. Use of these strategies helps to design a flexible and lean facility layout that is suited for the operating conditions of any job shop.
More advanced and efficient methods are possible according to Ott but require additional capacity. He believes any lean initiative starts and ends with the right leadership. "If you don't have a person determined to making it happen it probably won't. I've learned that the more senior the person the better. Staff can do it but it takes a very good staff person to overcome all the obstacles that are inevitable in change of this significance."
There is no better way to build quality into a product than through a robust process based on lean production methods. Total quality control (TQC) was very much a part of TPS as Toyota evolved. "In job shops quality is often left in the hands of operators where 100 percent inspection is performed while machines cycle. That is followed immediately by functional checks. Build into that the concepts of jidoka and you have a superior quality system with incredibly short feedback loops. Large lot production quality systems can't hold a candle to 1x1 production systems. With today's technology such as continuous induction furnaces, there is no reason why a job shop can't cost effectively achieve the ideals of 1 x 1 production."
And the future of lean manufacturing in the job shop?
"I suppose the idea [that] lean applies just as much to the job shop as the high volume manufacturer has yet to be overcome. If anything there should be hope that there is another way, it just takes a bit of adaptation and persistence to see it through. In 1946 Taiicho Ohno became manager of a machine shop at Toyota where they made transmission gears and suspension components. It was there, in one of the most unlikely places, a machine shop with old machines that lean as we know it today was born. Ohno had seen a better way in the textile industry. It was his insight, persistence and tenacity that revolutionized the manufacturing industry. Ironically I bet that 'his machine shop' is no longer just a machine shop. I would not be at all surprised today to find that Ohno's original machine shop is an integrated processing center."
For more information:
10808 South River Front Parkway, Suite 600
South Jordan, Utah 84095
Phone: (801) 972-6430
Dr. Shahrukh A. Irani
Department of Integrated Systems Engineering
The Ohio State University
294 Baker Systems Engineering
1971 Neil Avenue
Columbus, OH 43210
Phone: (614) 688-4685
Lean Enterprise Institute
215 First Street, Suite 300
Cambridge, MA 02142
Phone: (617) 871-2900