Other Lean Tools
Once the value flow map is created, several analyses are overlaid to analyze the process. The first is distinguishing operations that add value from those that do not. This was discussed earlier in this chapter. This concept was useful to initially simplify a process. Then we discussed balancing to the takt time, transfer batching, and scheduling. To continually improve the value content of a process, we need to simplify, standardize, and mistake-proof it by using additional Lean methods. The next analytical method is applying the concept of process waste to our value flow map. There are seven classic process wastes, and safety was recently added to the list by some organizations. Process waste adds complexity and cost and increases the likelihood of product and service defects.
Transportation waste occurs if materials or information are moved unnecessarily. Examples include walking an invoice around for signatures or moving materials without processing. Inventory waste occurs when we build excess materials, information, people, or other resources. The risk of creating this excess capacity, unless it is planned, is that demand may change. The result is excess capacity that will not be used, thus causing higher cost; in addition, resources used to create this excess capacity will not be available for other work. Excess capacity must also be kept in storage, which carries a risk for damage and higher costs for the storage. Motion waste occurs if the number of work tasks performed within an operation are more than the defined work standard. As an example, if an operation should be completed in three motions based on engineering studies, but workers use more than three motions to complete the work task, then this motion waste results in a longer processing time. The workers may also make mistakes or injure themselves by these unnecessary repetitive motions. Waiting waste occurs if an operation cannot start because it needs materials, information, or other resources from an upstream operation that is not available when the operation is ready to start. Examples include a job that cannot be processed because a machine is being repaired or materials and people are not available, or an invoice that is waiting for a manager’s approval. Overprocessing result from adding complexity to a process, such as adding features and functions with no value to customers. Examples include creating reports or other unneeded work objects. Defects are process waste because the work must be corrected or thrown out and redone. This wastes resources and time, thus increasing cost. The eighth waste is safety issues. These result in poor working conditions and operations that harm people, animals, property, or the environment. The advantage of understanding and seeing process waste is that these issues can be identified and projects can be created to resolve them. The concept of eight wastes is a powerful process-improvement method.
When we encounter a process issue, it useful to ask why it exists. It is vital to ask why several times to get as close as possible to root causes. This is known as 5-Why analysis, and it is a useful tool to identify root causes and other gaps that prevent process simplification and standardization. To ensure a root-cause analysis stays on track, it is useful for the team to have subject matter experts to unambiguously answer questions. A 5-Why example would be troubleshooting why a refrigerator does not work. The first question would be, “Why did the refrigerator stop working?” The team might verify through testing that the compressor motor stopped working. The next question would be, “Why did the compressor motor stop working?” The team might determine the compressor motor overheated. The third question would be, “Why did the compressor motor overheat?” The answer might be poor air circulation on a very hot day. The next question would be, “Why was there poor air circulation?” The answer might be the refrigerator was pushed against the wall and paper bags were stuffed around the refrigerator. Finally, the fifth question might be, “Why was the refrigerator pushed against the wall and paper bags stuffed around it?” The answer might be a poor process procedure. This is the root cause for the initial problem of the refrigerator failing. The solution would be to remove the paper bags to increase air circulation. In summary, a 5-Why analysis is a simple method to drill down deeper into a problem. It is best done with subject matter experts because each level of questioning needs to be verified before proceeding to the next question. The number of “whys” may be more than five if needed for resolution of the problem.
5-S is another useful method for process analysis and especially for process simplification and standardization. Most recently, some organizations have added safety and sustainability to the original 5-S method. This method is often successfully used for improving work areas. A before-and- after metric summary is created by the improvement team. These metrics are lead time through the process, yield, per-unit cost, percent value-add operations, floor space required for production, and required work-inprocess (WIP) inventory. To start the 5-S project, a team is formed with the people doing the work and a Lean facilitator. In manufacturing, the 5-S project requires three to five days. After a leadership introduction, the facilitator trains the team in the 5-S basics. At the end of the project, the workspace will be transformed and there will be a second leadership presentation discussing the observations made prior to the project and the improvements made as a result of the project.
The first step is sorting or organizes the workplace (seiri). The team goes to the work area and identifies what is needed for production. This includes parts, inventory, equipment, tools, and materials. Anything else is red-tagged for potential removal from the work area. Red-tagging rules are specified in advance of sorting. Examples include placing a tag on inventory more than one week old, equipment not used in the last three months, or tools and equipment not needed for this work area. The tag has the name or number for the item, the location from which it is taken, the location where it will be either stored or disposed, the quantity, the reason for tagging, contact people for placing the tag or the owners of the item, the date the item was tagged, and other relevant information. Once items are red-tagged, they are evaluated with stakeholders to determine if they should be kept in the work area, stored for future use, discarded, sold, returned to the supplier, or transferred to another work area. It is important to understand that although items are not needed for the current work, they may be very valuable in the future. An example is large and expensive pieces of equipment used in process industries, such as paper manufacturing. The cast iron frames in a paper factory may be a hundred years old, but they are still useful for production because electromechanical innovations were added to them over the years. At the end of this step, the team makes the changes and removes unnecessary items from the work area.
Once the work area is cleaned up, what is left is set in order (seiton). The workflow may be changed, equipment may be placed in a new sequence to simplify the process, and production balanced to the takt time. The goal is to ensure little or no process waste. Considering the eight process wastes, when setting up a work sequence we want to minimize motion, unnecessary transportation, inventory, unsafe conditions, and the other process wastes. The team also standardizes the use of materials, methods, machines, tools, communication, training, etc. Visual controls are set up. All materials, tools, equipment, storage containers, templates, and fixtures are labeled and placed in the correct location. Marked lines, color coding, and other visual information are added to the work areas to communicate production status. In summary, the team puts each item in the right place in the sequence of work tasks.
The third step is shining or sweeping (se/so), i.e., cleaning the work area. Cleaning has two components. First, prior to placing the equipment in order, the workspace floor is usually painted. In some industries it is painted white to show oil leaks from equipment; alternatively, the equipment may be painted white to identify oil leaks to aid maintenance and troubleshooting. Assignments are made for team members to clean equipment, tools, walls, and work bench surfaces to eliminate dirt, oil, and loose materials, to upgrade lighting, and other similar activities. Inspection lists and cleanliness criteria are agreed upon, and schedules are created to keep the area clean. Audits will be performed based on the fifth step to ensure cleanliness continues.
In the fourth step, the work area is standardized (seiketsu). Going forward, every operation will be standardized based on the best way to do it. Supporting standardization will be color-coding, mistake-proofing, checklists, training, and visual controls. Any remaining process waste will be eliminated over time using continuous improvement methods. The fifth 5-S step is self-discipline or sustaining these habits (shitsuke). An auditing plan is created to support the improvements from the first four steps. This plan will ensure consistency over time.
Some organizations have added safety and sustainability to their 5-S projects. Reducing unnecessary clutter, organizing the work area, and improving lighting will directly improve safety. But additional actions may be needed, and a safety expert can be added to the 5-S team. As the team rearranges the work area, the safety expert will provide advice on best practices to improve the safety of the work area and procedures to prevent injury and death in ways that meet local regulations. These actions may include ensuring workers are trained in safety practices, have the right equipment, place protective guards on machines, and other actions.
Sustainability is now an important consideration to ensure an organization’s practices save energy and resources and do not harm the environment over their useful life. Key areas of focus include recycling, repurposing, converting and properly disposing of materials, as well as minimizing the use of hazardous materials and using renewable energy sources. Metrics aligned to these focus areas include energy used per employee or unit of production, waste per employee, percent recycled materials, and the amount of carbon dioxide released into the environment per employee or for the total organization. Materials sourced in areas where people are exploited (i.e., conflict resources) are also a concern for organizations today.
Maintaining the balanced flow of work to achieve a takt time also requires that equipment and facilities be available to do work. TPM develops goals and measurements to manage unscheduled (i.e., corrective) versus scheduled maintenance (i.e., preventive) activities to ensure equipment availability. A TPM program consists of trained experts who determine equipment classifications, failure probabilities, and economics of equipment maintenance. TPM assigns responsibilities and budgets for equipment classifications, and it develops maintenance strategies based on equipment classification and design. Software applications are used to monitor equipment, schedule maintenance, and report status. A TPM system is periodically audited, and needed improvements are made. The guiding concepts in TPM are that availability depends on equipment reliability and maintainability, and maintainability in turn depends on preventive and corrective maintenance practices.
Maintenance activities are classified as preventive or corrective. Both are needed to control TPM costs and ensure equipment availability. Preventive maintenance uses equipment failure rates to schedule maintenance. In other words, maintenance interventions are predictable based on the component design, i.e., they are predictable and follow a known failure distribution. An example is scheduling maintenance for a personal vehicle based on recommended service intervals at critical mileage. These intervals are based on component designs from engineering tests by the manufacturer and its suppliers. The cost of preventive maintenance will usually be less than the cost related to simply waiting for a failure to occur.
Corrective maintenance is done when a component fails. Unexpected corrective maintenance for expensive equipment carries a high cost because the equipment is unavailable for use, as well as the cost of the repair. For low-cost components, such as light bulbs, several may be allowed to fail because the impact is minor (i.e., within safety parameters) and perhaps the entire population is replaced at once. In this situation, enough lighting is available and labor costs are kept low. In a corrective maintenance event, failed components are removed, analyzed for failure, and then repaired or replaced and tested.
Mistake-proofing has been mentioned in several chapters already. The concept is easily understood from the position that mistakes need to be prevented. But knowing how to prevent mistakes requires understanding key mistake-proofing concepts. Implementing effective mistake-proofing strategies requires an understanding of red-flag and error conditions that cause defects. Red-flag conditions include high complexity, an inability to measure performance, poorly written procedures, poorly maintained tools, little or no formal worker training, poor environmental conditions, stressful working conditions, and utilizing capacity beyond a stable level
(i.e., the system’s rated design throughput). If red-flag conditions exist, then the likelihood of an error condition occurring increases.
Error conditions may or may not lead to a defect, depending on whether the defect is prevented from occurring. Error conditions include processing omissions, processing errors, errors in setting up work, missing components, inclusion of incorrect components, completing the wrong job, operation errors, measurement errors, tool or equipment errors, and defects in job components. An example of an error condition using an invoicing example are no stamp on the envelope (processing omission), incorrect signature (processing error), incorrect spreadsheet formula (setup error), left out the profitability analysis (assembly omission), incorrect postage (incorrect component), incorrect letter placed in the envelope (incorrect job), incorrect spelling (operations error), incorrect measurement of the envelope weight (measurement error), machine fails to stamp envelop (equipment error), and copy toner ran out (defective component). These error conditions are exacerbated by red-flag conditions.
Although error conditions may exist, this does not imply a defect occurs. The error may be identified as it is being created and then corrected. The important concept for mistake-proofing is to prevent red-flag and error conditions by simplifying and standardizing processes. If a defect does occur, correct it before it moves downstream to the customer, where corrective actions are more expensive and take longer to implement.