Lean Manufacturing

September 1, 2010
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Lean manufacturing can streamline glass and ceramic manufacturing processes.

The concept and philosophy of lean has its roots in the Toyota Production System. (Photo courtesy of Toyota Motor Sales U.S.A., Inc.)


An Internet search of “lean manufacturing” produces an abundance of news, articles, books, and other references that discuss how many companies focus on waste reduction and continual improvement. Given the sluggish economy, today’s manufacturers must address a number of major business issues, including cost reduction, product quality, market globalization and heightened competition.

To underpin success, manufacturers must find ways to cut costs without impacting the quality of products and services. Lean manufacturing initiatives can help companies drive waste out of the manufacturing process by simplifying, standardizing and continually improving processes. As a result, lean manufacturing is growing in popularity, and it is particularly important in today’s manufacturing environment.

Definition and Common Tools

Contrary to what many people think, lean is not about cutting costs and headcount-it is about eliminating waste. As one lean consultant stated, “Lean means manufacturing without waste.”(1) The concept and philosophy of lean has its roots in the Toyota Production System, which focuses on reduction of muda, the Japanese term for “waste.” The Lean Manufacturing Handbook defines lean as follows:

Lean manufacturing is a manufacturing system and philosophy that was originally developed by Toyota and is now used by many manufacturers throughout the world. The term Lean is very apt because in lean manufacturing the emphasis is to cut out the “fat” or waste in the manufacturing process. Waste is defined as anything that does not add value to the customer. It could also be defined as anything the customer is unwilling to pay for.(2)

Lean is more than a toolkit or a set of steps a company follows in order to get to a planned result. It is also a philosophy about how to perform manufacturing. It involves the way a company executes production with the end-user of a product or service in mind.

“By identifying both who the customer is and how they define value, lean manufacturing allows companies and individuals to focus resources on adding value. By manufacturing to customer demand, driving out waste and continuously improving, companies can satisfy customers, employees and shareholders alike,” writes Vorne Industries, a lean tool development company that provides resources to improve the manufacturing productivity of other companies.(3)

Waste reduction is key to running a lean operation, and several tools are available to reduce waste, including 5S programs; Quick Changeover techniques (such as Single Minute Exchange of Die techniques); Just in Time production and supply; total production maintenance (TPM); mistake-proofing; and workspace layout improvements.(4) Seven key areas of waste (often referred to as the Deadly Wastes of Lean) typically plague many manufacturing organizations and should be revised or eliminated on the road to continual improvement(5)

Overproduction in its simplest form means producing goods that do not align with customer demand. It can also be described as excess productive capacity. Products often lie idle as excess inventory. This is an unprofitable, wasted investment.

Inventory waste results from overproduction, as mentioned above, or from building excess inventory in order to deal with fluctuations in production scheduling or production issues (resulting from process variability).

Transportation waste depends on whether the movement of materials, either in-house or externally to a customer, adds value for the customer. Tompkins points out that the opportunities for reducing transportation waste include “improved transportation administrative processes, pooling orders, combined multi-stop truckloads, and right sizing equipment.”(6)

Waiting idles material, machine and human resources. As a result, cycle times increase and throughputs decrease.

Movement can also lead to waste in a number of ways. For example, an operation not organized using a 5S system can lead to misplaced tools and materials. This results in operator inefficiencies as people waste time looking for needed items.

Defective parts not only require rework, but could also cause delays in fulfilling customer orders. Furthermore, rework adds to product cost.

Over-processing waste is often defined as the extra steps used to complete a process. However, Hajek highlights some subtle ways over-processing can occur (such as a dull drill bit that results in a few extra seconds per drilled hole). Other examples include a machine that takes more than the standard time to adjust-slowing down a process-or fatigued/dissatisfied operators who become less effective at their tasks.(7)

Figure 1. The Ishikawa (fishbone) diagram is primarily used to identify the causes of problems.

Discovering Improvement Opportunities

If you are interested in investigating opportunities for waste reduction in your operation, a good starting point is to evaluate your processes for improvement opportunities. This can be done with an Ishikawa (fishbone) diagram and/or value stream mapping.

The fishbone diagram is primarily used to identify the causes of problems. Many quality improvement professionals promote the diagram as an effective tool for creating a positive environment for brainstorming teams. The technique is described below, and Figure 1 provides a visual example.

The Fishbone diagram is also known as the cause and effect diagram, the root cause analysis, and the Ishikawa diagram, named after its originator Kaoru Ishikawa, the Japanese quality pioneer. In simple terms, Fishbone involves brainstorming in a structured format. The technique uses graphical means to relate the causes of a problem to the problem itself, in other words, to determine cause and effect. The diagram focuses on the causes rather than the effect. Because there may be a number of causes for a particular problem, this technique helps us to identify the root cause of the problem in a structured and uncomplicated manner. It also helps us to work on each cause prior to finding the root cause.(8)

Figure 2. The value stream mapping method visually maps the flow of all materials and information.

Value stream mapping (VSM) is another method that companies can use to find areas for prospective improvement. “The value stream mapping method visually maps the flow of materials and information from the time products come in the back door as raw materials, through all manufacturing process steps, and off the loading dock as finished products (see Figure 2). Mapping out the activities in the manufacturing process with cycle times, downtimes, in-process inventory, materials moves, and information flow paths helps [teams] visualize the current state of the process activities.”(9)

The map then guides the team or organization toward a view of the future desired state. “The process usually includes the physical mapping of the “current state” while focusing on the goal, or the “future state” map, which can serve as the foundation for other lean improvement strategies.”(10)

Process Industries vs. Discrete Manufacturing

The automobile manufacturing process is defined as discrete manufacturing, which means building or fabricating products by assembling components and subsystems into larger systems using manual or automated assembly lines. One example of this in the glass industry is architectural window assembly. However, glass and ceramics are different, because both often use continuous process manufacturing. When planning a lean implementation, important differences between the two manufacturing styles should be considered, as noted below:(11)

Discrete manufacturing tends to have more work-in-process (WIP) inventory in buffers and queues. It involves multiple, flexible workstations, and the production equipment size varies from small to large, depending on what is being assembled. Capital investment can be smaller and is typically spread across multiple workstations.

Continuous process manufacturing, on the other hand, involves process industries with little or no WIP. These process industries are typically characterized by high fixed capital, with a small number of work stations. The continuous process manufacturing operations tend to be less flexible, and, due to size, equipment is not easily moved into “work cells.”

With these differences, the following opportunities (key focus areas) can bring benefits to process manufacturing companies that implement lean: setup (or changeover) reduction; visual management, especially involving tool readiness and replacements; 5S and total productive maintenance (TPM); run sequencing; smoothing production schedules; standard work and operator awareness; adhering to production specifications and settings; implementation of process report card and measurement systems to learn more about process characteristics across the entire value stream; and quality validation of incoming material.(12)

Lean Techniques in Glass and Ceramic Manufacturing

Numerous glass and ceramic companies have started the journey toward lean manufacturing. Some are in the continuous manufacturing process industry, while others use glass components in discrete manufacturing environments. Either way, their successes warrant review for those considering lean.

Cardinal Glass manufactures laminated glass products for windows, with a focus on safety and security, storm protection, temperature and UV control, sound dampening, and other architectural design elements. During a time when the operation was experiencing a heavy growth curve, the company realized that there was a gap in process data that would allow for the more effective management of throughput to meet customer demand.

By applying lean concepts to address the gap and other issues, the company was able to reduce WIP at all resources by over 50%; increase square footage of stock output by 34% with a work-hour decrease of 2%; increase accuracy in production scheduling; reduce days of raw glass inventory by 66%; reduce days of interlayer inventory by 63%; successfully double sales in 2005-2006; and undergo controlled resizing in 2007-2008.(13)

Pittsburgh Glass Works (PGW) is a supplier of automotive glass and services, and it is also actively involved in fuel economy improvement research. The company was previously a division of PPG Industries, and, one year after it became a stand-alone company, it was able to highlight its operations successes resulting from lean manufacturing techniques.

The company worked in conjunction with customers to offer value-added solutions. Lean manufacturing improved its cost structure and enhanced its flexibility to serve customers through a streamlined organization based on value streams. Through the aggressive implementation of lean and six sigma processes, PGW also transformed its manufacturing footprint from nine plants to six. The company’s operational performance capabilities have been further enhanced through the rebuild of a float line and investments made in cold-end fabrication and bending processes.(14)

Ross Ceramics, a subsidiary of Rolls-Royce, is a manufacturer of highly specialized ceramic cone components that are used in jet engine turbine blades. The company took the opportunity to implement lean when moving into a new site, as described below:(15)

When we moved into the new site at Trentham, we designed manufacturing excellence in from the start. Though it was not a greenfield site, and we couldn’t have everything laid out exactly as we might have liked, we created [cellular manufacturing] which we used a lot of the lean tools and improved flow and throughput.

It was necessary to adapt and extend the [cell] concept because you can’t always stick to the lean textbook […]. There are large pieces of the kit that you can’t duplicate in each cell, so we created what we call “virtual cells” where we have expanded the principle of dedication. You might have a particular piece of capital equipment that is dedicated to particular product groups but not just to one cell. That is not altogether a bad thing. By moving production from one machine to another you are already inviting variation. By grouping relevant products together, particularly high-running products, you improve process stability.


Additional Lessons

In closing, the essence of lean is reducing waste from the value stream and ultimately providing customers with products that they value. As you consider the implementation of lean in your operation, learn from the previous experiences of those who have already started the journey. For those with continuous manufacturing processes, like the glass and ceramic industries, here are a few additional lessons highlighted by Price and Simonin:(16)
  • Know your value stream.
  • Analytically determine the minimum safe run/batch size.
  • Not all traditional lean tools apply in continuous process environments (cells, intra-process kanban). Forcing them can be disastrous.
  • Do not accept the old adage that “running this operation is an art.” Even with the many variables in continuous process environments, standard work can be achieved.
  • Don’t let increased capacity become overproduction-one of the Seven Deadly Wastes of Lean.
  • Replicate, replicate, replicate! Most lean improvements in continuous processes can be replicated and applied to sister processes/plants. Replicate quickly to accelerate the improvements’ learning cycles.
For more information, contact the author at (607) 974-8179 or howellvw@corning.com.

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