Key Definitions

5S  

5S provides the foundation for all other improvements. It is often implemented as the first step in implementing lean operations, Total Productive Maintenance programs or Total Quality Management. 

• S1 - Sort Out what is needed from what is not needed. This can be done using for example the “TAG” method as follows. First, sort through all of the items in your workplace and tag each item that is considered important to perform the workplace tasks with a “Green” tag. All items that are considered not important to perform the workplace tasks receive a “Red” tag. All items that one cannot decide about should receive a “Yellow” tag. In a multi-shift environment each shift independently selects the color of tag for the item. Once everybody has had an opportunity to put on the tags, everything that has all Red tags is removed. Anything with at least one green tag stays. All the items with a mix of red and yellow stay or are placed into an intermediate storage area if available. They are re-evaluated after a certain time period. 

• S2 - Set in Order, i.e. determine where to place each item that is retained in the workplace. This could be on shelves or on the floor. The position for the item should be selected so that the minimum motion is required to use the item in the task. Once it is certain that the items are positioned in the correct location, their location is marked with lines, signs or shadows. These lines or borders create meaning which is communicated for an otherwise empty space. 

• S3 – Shine and Inspect, i.e. clean the work space so it is free from dirt, stains and impurities. As everyone who lives in a family knows, what is clean for one person is not clean for another person. Therefore, the first step is to decide how clean is clean with the people who are involved in performing work within the area. The work team can develop a scale of cleanliness such as: “Clean enough to eat from the surface / White glove clean” to the opposite end of “Clean enough for my kids” or “Pigsty” to “Whistle-clean.” Involving the workers performing the function means that clean is seen as an incremental process and achievable goals are set for each area. Next one has to decide what methods, tools and supplies are to be used in the cleaning. Tools and supplies should be stored in the 5S corner or cupboard. 

• S4- Standardize, i.e. establish standard procedures to perform S1, S2 and S3 on a regular basis. The tasks to be performed are assigned to individuals and scheduled. This can be done using a simple task assignment matrix. For example, public restrooms often have a table hanging behind the entrance door, where it lists the tasks, who is assigned, the time and notes for performance. 

• S5 – Sustain, i.e. implement a system to ensure that the 5S policies are followed. This consists of regular audits, promotion and communication. This requires that the audits be scheduled and the results communicated. The results are often displayed at the entrance to a department or workplace as well as in specific locations throughout the facility. The results are displayed in terms of “before and after” pictures as well as radar charts showing the audit scores for each S over time. Promotion can occur at those same locations with posters about the benefits of 5S as well as pictures of the 5S winner of the month. 

Once it is implemented, S1, S2 and S3 together form an ongoing cycle of cleaning that is standardized or structured by S4 and institutionalized or sustained by S5.

Cleaning and setting in order requires an investment in time and capacity to implement and maintain it. Yet benefits include: 

• 5S increases the safety of the worker and reduces the risk of machine break downs – for example oil leaks can easily be spotted on a clean surface. 

• 5S - reducing the safety hazard for workers and the risk of machine break downs - significantly reduces an important source of variance in the system which otherwise cannot be avoided. Variance is always detrimental to shop performance! 

• 5S gives things and space meaning. As a result, things and space provide explicit information. If a worker looks for a tool he knows where to find it. 

• 5S - loading things and space with information - allows for the right information being at the right time at the right place. The worker has the tool at hand when he/she needs it which reduces variance and so improves performance.

Total Productive Maintenance  

Total Productive Maintenance aims at improving the Overall Equipment Effectiveness. The capacity that a firm is purchasing when it purchases equipment can be lost if the firm does not maintain it. Often these losses are classified into six categories – The 6 BIG losses! - as follows: 

1. Breakdown losses 

2. Setup and adjustment losses 

3. Idling and minor stoppage losses 

4. Speed losses 

5. Quality defects and rework losses 

6. Start-up yield losses 

The availability of the machine is influenced by the breakdown losses and setup and adjustment losses. The breakdown loss is the most obvious, because the machine is not able to function without being repaired. The equipment setup and adjustment losses occur as the machine switches from producing one product to another. The performance rate of the machine is affected by the idling and minor stoppage losses and reduced speed losses. The idling and minor stoppage losses occur during the operation of the machine when the machine has to be paused to clean debris or correct a minor malfunction, such as loose bolt or wire. The speed losses occur as the machine is operated at a lower speed to ensure that the quality is good or the machine will not breakdown. The quality rate of the machine is affected by the quality defects and rework losses and start-up yield losses. The start-up and yield losses are quality losses because they occur when the parameters of the machine’s operations are being adjusted.

Maintenance actions can be classified by whether they are reactive or proactive. Reactive maintenance responds to the breakdowns after they have occurred, which is too late to prevent capacity losses. Proactive maintenance seeks to avoid losses through preventive maintenance activities (e.g. think of changing the oil and the filters on a car). Predictive maintenance makes the status of the components of machines visible in order to predict when they will need to be repaired (e.g. a clean, white floor under a machine will show any oil leaks, and a vibration sensor on the machine will indicate when a bearing is failing). Thus predictive maintenance is talking to the parts. 

Predictive and proactive maintenance avoid the capacity losses and are the preferred methods in lean operations. Lean prevents the six big losses using three primary methods. 

• Lean measures the Overall Equipment Effectiveness regularly on the key equipment.

• Lean has a checklist of the maintenance tasks the operator must perform daily.

• Lean has a schedule of the preventive maintenance and predictive maintenance tasks the maintenance technician is to perform. 

These action creates a structure that ensures that the required maintenance actions take place.

(Total) Quality Management  

Total Quality Management is an integrative management concept which aims at continuously improving and sustaining quality products and processes. It is a management strategy aimed at embedding awareness of quality in all organizational processes - involving management, workforce, suppliers, and customers -  in order to meet and/or exceed customer expectations.

More information on (Total) Quality Management can be found here.

Single Minute Exchange of Die  

The rapid changeover of a production process from running one product to the next is the key to reducing production lot sizes and thereby improving flow. The objective of the concept of Single-Minute Exchange of Die is the reduction of the set-up or changeover time. More information can be found here.

Continuous Improvement 

Continuous improvement builds the backbone for 5S, Total Productive Maintenance, Total Quality Management and other management concepts for a lean work design. 

Continuous improvement consists of two words – continuous and improvement. Improvement means eliminating errors or defects from the process. This leads to increased productivity, increased resource effectiveness and improved responsiveness to the customer. Continuous means that the improvement process is an ongoing journey.

The process of continuous improvement is expressed as a continual repetition of the Plan-Do-Check-Act cycle. Plan-Do-Check-Act is based on the scientific method (see Shewart and Deming). It was popularized by Deming in his lectures and is the standard approach for continuous improvement or continuous problem solving. 

Plan-Do-Check-Act is a conceptual explanation of the scientific method. 

Companies typically operationalize it by creating standardized problem solving approaches for their company. For example, General Electric’s Six Sigma uses Define-Measure-Analyze-Improve-Control for its standard problem solving. 

Standard problem solving tools include:

• A3 thinking

• Pareto diagram 

• Cause-and-effect diagram (also Ishikawa or Fishbone diagram) 

• Control Charts

Problem solution can be implemented through:

• Poka Yoke

• Gantt chart 

• To Do Matrix of Who, What, When, Where

• Kaizen

Kaizen is the Japanese word for continuous improvement. This word was popularized in the US by Imai (1986). It is often implemented as a series of structured events which occur over a period of a day to a week. As part of kaizen there is detailed advance planning followed by a rapid implementation of the plan. Typically, kaizen focuses on a large change in the process, while the worker’s continuous improvement is concerned with a more limited portion of the process.

The concept of performance frontiers (see e.g. Schmenner & Swink, 1998) can be used to gain a deeper understanding into variability to provide guidance on the application of continuous improvement. First we introduce the difference between common and assignable variability (see e.g. Shewart, 1931; Deming, 1982). Shewart (1931) argued that each controlled capability is variable. A capability was said to be under control when, through the use of past experience, one can predict, at least within limits, how its target condition may be expected to vary in the future. Prediction within limits means that the probability that the observed measure for the target condition will be within the given limits can be stated at least approximately. It follows that a controlled process is a constant system of chance causes. 

Further, it was found that there are causes of variability that do not belong to a constant system. These causes can be assigned to special causes and these assignable (or special) causes of variation found and eliminated. 

Variability can be categorized into three categories as follows: 

• Assignable variability can be found and eliminated through improvement bringing the process under control. If a process is under control a company reached its operating frontier.  Note that a process can be under control (i.e. at its operating frontier) yet still not be capable to produce to the required quality standards!

• Common variability of the infra-structure can only be reduced by infra-structural change. 

• Common variability of the physical asset can only be reduced by radical technological upgrades or replacements.

This categorization guides the problem solving tools and solutions applied.

Facility Layout  

The facility layout is the physical arrangement of the parts of the processes (departments, work centers or equipment) within a facility. The facility layout provides the framework for the resource assignments and the structure for information and knowledge integration.

Facility layout has a major impact on the work design. The facility layout determines the assignment of resources, the flow of work  - and the amount of motion that is required for the work to flow through the facility - and the flow of information. A lean work design seeks to minimize the amount of work that is required for movement to support the process; capacity is restricted thus capacity used to support the process which is not required (for example unnecessary motion) is capacity lost for the throughput and should be avoided.

There are three major types of layouts: 

• A product layout (e.g. a flow line) uses highly specialized machines and places the equipment and machines in the sequence in which the production of the product requires their use. The product layout is the organization of the processes into the sequence in which they need to be performed to manufacture or assemble a particular product. 

• A cell layout uses general purpose machines and places them in the sequence that are going to be used in the production of product families.

• A process layout uses general purpose machines and places the machines and equipment that do the same function together (e.g. lathes are all located together).

The type of layout depends on both the volume of the product being produced (the production lot size) and the variety of the products being produced. Make-to-order shops produce highly variable products in small lot sizes and therefore typically apply a process layout or cell layout. 

The facility layout also influences the “Zone of Control” in the facility. Managers are assigned an area of responsibility and that area is subdivided into other areas of responsibility. These areas overlap. The zone control creates a structure of responsibility and coverage. This is similar to using a “zone” in sports, where each player is assigned a portion of the “play area” to defend, rather than defending one-on-one. This ensures the unity of command which avoids misunderstandings in the communication of goals and objectives. 

Visible Control  

The objective of a control system is to stabilize a process by triggering action if the process deviates from a target. A control system typically consists of a parameter that is being measured against a target and includes a feedback loop to the process to adjust the parameter output if the parameter deviates from the target. 

This becomes a visual control signal when the measurement of the performance to the target is made visual. In processes the adjustment actions are typically taken by the humans in the system. So, lean uses visual control signals to call for action. This ensures that the information is available when it is needed – as it is visual to anyone. 

Visual control is an important form of communication in the company ensuring that the right information is at the right time at the right place. It builds a cornerstone for lean concepts as 5S, Total Productive Maintenance, Total Quality Management, Just-In-Time etc.

Pull Systems  

A pull system is a production planning and control system that limits the load in the production system based on feedback about the throughput of the system. This requires that jobs are not released directly to the shop floor when they arrive, but are retained in a buffer (i.e. a pre-shop pool or backlog of orders). Jobs are released so that the workload on the shop floor stays within limits. One of the key concepts for lean planning and and control in the context of a lean work design suitable for small to medium sized make-to-order companies is Workload Control.