In production plants across the globe, lean manufacturing techniques are being used to meet increasing demands placed on manufacturers. Originally developed as a methodology to make production processes highly efficient, lean techniques have been adopted by more than 72 percent of machine shops across the country. For many of these, the techniques have helped them to dramatically increase their competitive edge, while continuing to remove wasteful practices and contribute to the bottom line.
Although the basic lean model was introduced more than 100 years ago, it has continued to evolve over time, from Henry Ford’s continuous assembly lines for the Ford Model T, to the concept of interchangeable parts used by Eli Whitney and Samuel Colt, to the Toyota Production System. These concepts, in addition to a multitude of others, have come together to formulate what we know today as lean manufacturing.
The core idea behind lean manufacturing is maximizing customer value while minimizing waste, thereby achieving manufacturing excellence through the creation of more value with fewer resources. Waste is defined as an activity that does not add value to the product. Through the elimination of waste along the entire manufacturing process, rather than at isolated points, companies are able to create processes that need less human effort, less space, less capital, and less time to produce high-quality, lower-cost products compared with traditional business systems.
Given the shift toward a customer-centric environment while facing formidable competition, many manufacturers are implementing lean principles to help eliminate waste and increase efficiencies rather than relying on processes and procedures that have been used in the past (figure 1). To help guide companies through a lean transformation, James Womack and Daniel Jones developed a five-step thought process detailed in their book, Lean Thinking (Free Press, 2003). The five steps represent a continuous cycle of improvement, and act as the foundation for the successful implementation of lean in a facility:
1. Specify value. Identify the value of a specific product from the customer’s perspective. Value can only be defined by the ultimate customer, although it must be created by the producer.
2. Identify the value stream. Identifying the entire value stream for each product will almost always reveal three types of actions along the value stream, including steps that create value, steps that create no value but are unavoidable with current technologies and production assets, and nonvalue-adding steps that can be eliminated.
3. Create flow. Once value has been precisely specified and the value stream for a specific product fully mapped, making work elements flow continuously with minimal queues and no rework or stoppages is the next step in a lean transformation.
4. Establish pull. After wasteful steps have been removed, and flow has been established, the ability to deliver only what is wanted by your customer, and only when they want it, is the fourth principle of lean thinking: pull. Allowing customers to pull a product through the process is indicative of the organization’s ability to be responsive to a customer’s needs.
5. Seek perfection. As organizations bring their processes through the initial four principles—accurately specifying value, identifying the value stream and removing wasteful steps, creating flow, and letting customers pull value from the enterprise—the fifth principle, perfection, becomes attainable.
Although there is no such thing as a “perfect” process, companies can constantly strive for perfection through the elimination of waste. In the Toyota Production System—developed by Taiichi Ohno, Shigeo Shingo, and Eiji Toyoda—one of the major precursors to lean manufacturing, the elimination of waste, is also one of the main objectives. The Toyota Production System even goes so far as to identify seven different types of wastes, known as the “seven deadly wastes.”
The seven deadly wastes of manufacturing are activities that have been identified as nonvalue-adding events or processes that hinder profitability in a company. All finished goods and batched inspections include the seven deadly wastes. However, being cognizant of this fact can help companies eliminate the waste while achieving maximum efficiencies. Below are the seven deadly wastes and lean tools that can be implemented to counteract waste.
1. Waiting. Time spent waiting on something, or someone, to complete a task.
Lean tool: Design processes so that flow is continuous, and there are minimal (or no) buffers between steps in production.
2. Motion. Any unnecessary movement of people that does not add value to the product or service.
Lean tool: Ensure that work areas are logically organized, e.g., rather than having a worker walk 20 feet to pick up spare parts every half-hour, minimize the distance to 5 feet to significantly reduce excess motion.
3. Overprocessing. Using more energy or activity than is needed to produce a product.
Lean tool: Look for potential simplifications to the manufacturing process, e.g., instead of completing 100-percent inspections on parts that never fail, reduce the number of parts inspected to greatly reduce processing time.
4. Inventories and queues. Excess product waiting to be processed.
Lean tool: Excess or just-in-case inventory can result in lost money and resources caused by storage. Aiming for just-in-time inventory reduces downtime associated with inventory problems.
5. Transportation. Unnecessary movement to get goods from one process to the next.
Lean tool: The transportation of goods or material can be risky. Damages or delays incurred while goods are in transit uses up resources. Effective planning can ensure that excess wastes in terms of moving do not occur.
6. Overproduction. Making more parts or information than is required.
Lean tool: Pacing material flow through production to match customer demand can help to minimize overproduction, and is more cost-efficient in the long run.
7. Fixing defects and mistakes. Time spent repairing or reworking material or information.
Lean tool: The cost of fixing defects or mistakes is often cheaper the sooner they are found. For example, mistakes found at raw-materials inspection may cost only $10 to isolate and fix, whereas fixing a product at the work-in-progress stage may cost hundreds of dollars.
“Lean is not simply a toolbox, but a total perspective.” Undertaking a lean transformation can be a difficult transition. However, understanding that lean is not only a set of tools but also a cultural concept that affects every level of an organization, will result in a successful implementation. From the production floor to C-level management, it is critical for teams to understand the concept and buy into the overall goal. Below are four common lean tools and practices implemented in the process of bringing on a lean transformation.
Cellular manufacturing: Arranging production work stations and equipment in a sequence that supports a smooth flow of materials and components through the production process with minimal transport or delay. Shifting from traditional batch-and-queue mass production systems (figure 2) to a single-piece flow-and-pull production system (figure 3), cellular manufacturing helps to eliminate overproduction and reduce defects.
Example: Allowing organizations to be flexible in terms of production setup and delivery, cellular manufacturing helps to facilitate faster turnaround and reduce work-in-process inventory, while optimizing the layout on the production floor.
5S workplace organization: A series of activities for eliminating wastes that contribute to errors, defects, and injuries.
Simplify. Clearly distinguishing what is necessary and disposing of the unnecessary
Straighten. Organizing the necessary items so that they can be used and returned easily (figure 4)
Scrub. Cleaning floors, equipment, and furniture in all areas of the workplace.
Stabilize. Maintaining and improving the standards of the first three S’s
Sustain. Achieving the discipline of properly maintaining the correct 5S procedures and continuously improving to making maintaining 5S easier
In-line inspection: Removing the need for separate testing and inspection labs (figure 5), in-line inspection allows workers to perform inspections directly on the line to ensure the accuracy of in-process work. Verifying measurements on the line, rather than having to bring a part to a separate temperature-controlled room, helps to create more efficient workflows and streamlines the inspection process (figure 6).
Example: In a lean work cell, the goal is to eliminate scrap, while building quality into the process. One way to accomplish this is to implement portable coordinate measuring machines (CMMs) on the line, increasing production efficiencies and producing higher quality finished goods. Mounted directly on the machine, portable CMMs eliminate the need to bring a part to a quality lab, saving the company time and money. By utilizing portable metrology tools such as articulating arms designed to withstand harsh working environments, operators are able to quickly identify defects of parts in-process.
Kaizen: Often considered to be the building block of all lean production methods, kaizen events are rapid and cost-effective projects that focus on identifying waste, improving productivity, and achieving sustained continual improvement in targeted activities and processes.
Aiming to involve workers from multiple functions and levels in working together to address a problem or improve a process, the kaizen team uses analytical techniques such as value-stream mapping and the 5 Whys to identify opportunities quickly to eliminate waste in a targeted process or production area.
Example: After identifying an area for a rapid improvement event, such as a production area where significant bottlenecks or delays occur, the kaizen team must identify the root cause of the problem. This can be accomplished by utilizing the 5 Whys technique. An example would be:
• Why did the machine stop? There was an overload, and the fuse blew.
• Why was there an overload? The bearing was not sufficiently lubricated.
• Why wasn’t it lubricated sufficiently? The lubrication pump was not pumping sufficiently.
• Why wasn’t it pumping sufficiently? The shaft of the pump was worn and rattling.
• Why was the shaft worn out? There was no strainer attached and metal scrap got in.
Once the root cause of the problem has been identified, the team can then work to collect information on the targeted area, such as measurements of overall product quality, amount of work-in-progress, and scrap rate and source of scrap. Analyzing these data allows the team to identify areas for improvement, and test improvement options before implementation.
A key portion of a kaizen event is the follow-up activity to ensure improvements are sustained and not just temporary. Following an event, the team routinely tracks key performance measures and document improvement gains to assess performance and identify modifications that may be necessary to sustain the improvements.
Ideal for a variety of applications, including 3-D modeling, reverse engineering, alignment, machine installations, and rapid prototyping, portable coordinate measuring machines (CMMs) such as articulating arms and laser trackers have become critical components in the implementation of lean principles. Providing companies with ways to help streamline inspection processes, create flow, and eliminate deadly wastes in a lean manufacturing environment, portable CMMs enable companies to do more with less.
One of the major elements of lean manufacturing is the concept of creating flow. By making work elements flow continuously with minimal queues and no rework or stoppages, a company is one step closer to reaching optimal levels of production. Creating flow through the implementation of portable CMMs on the line simultaneously eliminates two of the deadly wastes, waiting and transportation.
For example, by mounting an articulating arm directly on a machine producing a part, operators are able to create flow between each station and eliminate the waiting periods commonly found in batch-and-queue manufacturing. Eliminating the machine outage time necessary for off-line inspection, operators are able to reduce inspection times without having to transport materials to inspection rooms while mitigating measurement variability between users.
Fixing defects is another example of a deadly waste that can be helped through the implementation of portable CMMs. Many companies utilize portable CMMs for incoming and in-process inspection. For example, by implementing an articulating arm to inspect parts as they arrive, defects can be eliminated at the raw materials stage, preventing incorrect products from making it further into the production process. Additionally, laser trackers can be used for in-process inspections, ensuring that components are aligned correctly for work-in-process, eliminating rework at final inspection. Discovering any errors early in the production process saves companies valuable time and money.
Many companies have implemented lean manufacturing techniques to create more efficient workflows. Through the elimination of waste and the creation of flow through the various processes, companies are able to eliminate costly scrap and rework while contributing to their bottom line.
Implementing portable CMMs into standard workflows has helped them achieve their lean manufacturing goals; in many cases, companies that have implemented portable CMMs directly on the line for in-process inspections have seen a reduction in inspection time of up to 60 percent. Used to ensure accurate alignment and precision measurements, portable CMMs have become a value-adding component helping companies to achieve various lean principles.