Value stream improvement, sometimes called “flow level kaizen,” is the best tool for identifying and planning opportunities for process kaizen. People often mistake value stream mapping for process mapping. Process mapping simply involves mapping any process. Value stream mapping involves mapping information and product flow for a given value stream. The mapping is done in such a way that allows one to visualize the current state and to plan and implement a future state with measurable goals.
Before value stream mapping was popular in the United States, organizations utilized process kaizen tools while largely ignoring their effect on the entire value stream. This led to successes in individual areas without the ability to demonstrate significant improvement to the value stream as a whole. Value stream mapping allows organizations to target the right areas for process kaizen and to track, measure, and demonstrate the effects that process kaizen improvements will have.
How does it do this? Firstly, current state value stream mapping allows an organization to identify waste and sources of waste. It forces people to ask why things are done a certain way, which uncovers many opportunities for improvement. The current state provides a baseline from which people can work to create a lean future state.
Future state mapping is a process by which organizations identify a lean future condition. This future condition includes things like continuous flow manufacturing wherever possible, supermarkets or FIFO lanes (depending on the degree to which the products are custom) where continuous flow is not possible, and level production. Finally, they identify the types of process improvements that need to be made to achieve the future state. We recommend conducting a brainstorming session to identify such improvements.
After the future state has been created, a critical part of value stream mapping is creating an implementation plan. Based on the future state map, an implementation plan identifies each activity required to achieve the future state, the responsible team/individual, and the due date. Activities on an implementation plan will typically include kaizen events and "Six Sigma" type projects. Targeting such activities improves their bottom-line effectiveness since each activity will be leading to value stream improvement.
Value Stream Mapping is primarily a planning tool. It allows an organization to identify waste and sources of waste for a given value stream, systematically create a lean future state with less waste, and plan the implementation of the future state.
Darren Dolcemascolo
Tuesday, October 2, 2007
Planning and Conducting Kaizen Events
Kaizen events are powerful. They enable rapid improvements over a very short period of time. However, the biggest problem that I have seen with kaizen is the seemingly random selection of particular areas or processes. The goal of any kaizen event should be to improve the overall system. An organization that wants to implement lean manufacturing should first use Value Stream Mapping (VSM) as its tool for identifying and prioritizing kaizen opportunities. The only possible exception to this rule is the use of kaizen events to implement 5S. All lean manufacturers should have 5S in place company-wide (though value stream mapping might still aid an organization in selecting the starting point for 5S). Assuming you’ve mapped your value streams and are ready to start process-level kaizen activities, what do you do next? This article will discuss 5 steps to planning and performing kaizen events.
Step 1: Selecting an Area
You may have identified several high-priority kaizen opportunities through Value Stream Mapping. Some additional selection ideas you might use for a first kaizen event include the following:
- Select an area that has a relatively sound process and a high likelihood of success. It is important to succeed quickly in the first kaizen event to build momentum for the subsequent events.
- Select an area that will be good for visibly demonstrating improvement to the rest of the organization.
- Select an area that is small and self-contained. For example, you might have a cell (or the opportunity to create a cell) that produces a complete product and is not dependent on other processes in the organization.
Step 2: Selecting Team Members
A good size kaizen team ranges from 6 to about 12 members. Team members for a kaizen event should include the following:
- People from the selected area (about 50%)
- Maintenance person.
- People from production control, warehouse, other production areas, quality, design engineering, manufacturing engineering. This depends on the area on which you are focused.
- Customers, suppliers, consultants as needed.
The person you select as the event leader must have experience and should not be from the particular area selected. We recommend that the first few kaizen events be professionally conducted; select a consultant that has experience conducting such events. Also, select a consultant that states his intention to help your organization become self-sufficient at conducting kaizen events.
Step 3: Preparing the Area
Specific supplies will depend on the area in which your kaizen event is being done. In production areas, you will likely need hand tools, tape, cardboard, tape measures, stopwatch, connectors to link up utilities, carts, safety equipment, cleaning supplies, and forklifts. If it is a non-production area such as a design-for-manufacturability or information flow improvement event, you will not need much of the equipment mentioned above.
Regardless of the area you have selected, you will need flip charts, markers, dry erase board, and a conference room.
You will also need to gather as much baseline information about the area as possible: customer requirements, layouts or drawings, flow charts, procedures, etc. If you’ve done your value stream mapping up-front, much of this should be at your fingertips. Have all of this available for the team on the first day of the event.
Step 4: Game Day – Performing the Event Itself
For a five-day Kaizen event, the event proceeds as follows:
Day 1: Lean Training with emphasis on a particular tool (5S, DFM, SMED, etc.)
Day 2: Complete Training; this may include teambuilding exercise(s). Document current state
Day 3: Brainstorming; Idea Selection (future state); Future state formulation
Day 4: Implementation of Future State (implement as much as possible); Develop action plan for items that cannot be implemented during event.
Day 5: Complete Implementation odds-and-ends; Final Report out and celebration
Step 5: Follow Up
There must be a follow up to the action plan developed during the event. Sometimes, the consultant will do this as part of the project. Regular meetings should be held until action items have been completed. The remaining action items should be visibly posted in the area until they have been completed.
Darren Dolcemascolo
Step 1: Selecting an Area
You may have identified several high-priority kaizen opportunities through Value Stream Mapping. Some additional selection ideas you might use for a first kaizen event include the following:
- Select an area that has a relatively sound process and a high likelihood of success. It is important to succeed quickly in the first kaizen event to build momentum for the subsequent events.
- Select an area that will be good for visibly demonstrating improvement to the rest of the organization.
- Select an area that is small and self-contained. For example, you might have a cell (or the opportunity to create a cell) that produces a complete product and is not dependent on other processes in the organization.
Step 2: Selecting Team Members
A good size kaizen team ranges from 6 to about 12 members. Team members for a kaizen event should include the following:
- People from the selected area (about 50%)
- Maintenance person.
- People from production control, warehouse, other production areas, quality, design engineering, manufacturing engineering. This depends on the area on which you are focused.
- Customers, suppliers, consultants as needed.
The person you select as the event leader must have experience and should not be from the particular area selected. We recommend that the first few kaizen events be professionally conducted; select a consultant that has experience conducting such events. Also, select a consultant that states his intention to help your organization become self-sufficient at conducting kaizen events.
Step 3: Preparing the Area
Specific supplies will depend on the area in which your kaizen event is being done. In production areas, you will likely need hand tools, tape, cardboard, tape measures, stopwatch, connectors to link up utilities, carts, safety equipment, cleaning supplies, and forklifts. If it is a non-production area such as a design-for-manufacturability or information flow improvement event, you will not need much of the equipment mentioned above.
Regardless of the area you have selected, you will need flip charts, markers, dry erase board, and a conference room.
You will also need to gather as much baseline information about the area as possible: customer requirements, layouts or drawings, flow charts, procedures, etc. If you’ve done your value stream mapping up-front, much of this should be at your fingertips. Have all of this available for the team on the first day of the event.
Step 4: Game Day – Performing the Event Itself
For a five-day Kaizen event, the event proceeds as follows:
Day 1: Lean Training with emphasis on a particular tool (5S, DFM, SMED, etc.)
Day 2: Complete Training; this may include teambuilding exercise(s). Document current state
Day 3: Brainstorming; Idea Selection (future state); Future state formulation
Day 4: Implementation of Future State (implement as much as possible); Develop action plan for items that cannot be implemented during event.
Day 5: Complete Implementation odds-and-ends; Final Report out and celebration
Step 5: Follow Up
There must be a follow up to the action plan developed during the event. Sometimes, the consultant will do this as part of the project. Regular meetings should be held until action items have been completed. The remaining action items should be visibly posted in the area until they have been completed.
Darren Dolcemascolo
When and How to Use Kaizen Events
Many organizations are reluctant to utilize kaizen events because such events take a team of employees away from their "real jobs" for 3 to 5 days at a time. Companies often choose to substitute kaizen events with projects assigned to one or two individuals. Because of a lack of perceived importance and a lack of substantial participation and buy-in, very rarely does this result in true improvement. In fact, it often results in organizations claiming that lean does not work for them.
When I encounter companies in this situation, I argue that the effects of a properly planned and executed kaizen event will pay for the perceived "lost time" of the participants many times over. In fact, their "real jobs" will become easier because they will include less "firefighting" and more productive activities since kaizen events will address many of the day-to-day problems with permanent solutions instead of band aids. Earlier this year, I wrote about what makes kaizen events effective in an article called The Power of Kaizen. In this month's article on the subject, you will learn when kaizen events should be used for maximum impact.
Recall that kaizen events are focused 3 to 5 day breakthrough events that generally include the following activities:
- Training
- Defining the Problem/Goals
- Documenting the Current State
- Brainstorming and Developing a Future State
- Implementation
- Developing a Follow-up Plan
- Presenting Results
- Celebrating Successes
This process works in a variety of situations to solve a variety of problems. Kaizen events are often planned using value stream mapping to target the right areas for improvement. Following is a list of some of the problems that can be solved using kaizen events:
- Decreasing changeover time on a piece of equipment or process. Using kaizen, a team can improve upon the time to changeover equipment using the SMED system, developed by Shigeo Shingo.
- Organizing the workplace using 5S.
- Creating a one-piece flow workcell.
- Developing a pull system.
- Improving equipment reliability through TPM (Total Productive Maintenance).
- Improving the manufacturability of a product design.
- Improving a product development process.
- Improving other administrative processes such as order processing, procurement, engineering change processing, and other paperwork/information processing activities.
Kaizen events, however, cannot solve any problem within an organization. There are certain types of improvements for which other methods should be used. Process Improvements (such as “Six Sigma” type analysis) aimed at yield improvement and variation/scrap reduction are key examples. Suppose that a particular process has a first-pass yield of only 85% when it would need to be much closer to 100% to run in a one-piece flow environment. If the process must be analyzed using experiments and statistical methods, it would make sense to utilize a team but not a kaizen event. To implement these type of improvements, a problem solving team (or a six sigma team) that meets regularly over a period of time works better than a kaizen team meeting for five consecutive days.
In order to utilize kaizen events effectively, it is important to understand the types of problems for which kaizen events should and should not be used. With proper planning, kaizen events can bring breakthrough improvement to an organization on its lean journey.
Darren Dolcemascolo
When I encounter companies in this situation, I argue that the effects of a properly planned and executed kaizen event will pay for the perceived "lost time" of the participants many times over. In fact, their "real jobs" will become easier because they will include less "firefighting" and more productive activities since kaizen events will address many of the day-to-day problems with permanent solutions instead of band aids. Earlier this year, I wrote about what makes kaizen events effective in an article called The Power of Kaizen. In this month's article on the subject, you will learn when kaizen events should be used for maximum impact.
Recall that kaizen events are focused 3 to 5 day breakthrough events that generally include the following activities:
- Training
- Defining the Problem/Goals
- Documenting the Current State
- Brainstorming and Developing a Future State
- Implementation
- Developing a Follow-up Plan
- Presenting Results
- Celebrating Successes
This process works in a variety of situations to solve a variety of problems. Kaizen events are often planned using value stream mapping to target the right areas for improvement. Following is a list of some of the problems that can be solved using kaizen events:
- Decreasing changeover time on a piece of equipment or process. Using kaizen, a team can improve upon the time to changeover equipment using the SMED system, developed by Shigeo Shingo.
- Organizing the workplace using 5S.
- Creating a one-piece flow workcell.
- Developing a pull system.
- Improving equipment reliability through TPM (Total Productive Maintenance).
- Improving the manufacturability of a product design.
- Improving a product development process.
- Improving other administrative processes such as order processing, procurement, engineering change processing, and other paperwork/information processing activities.
Kaizen events, however, cannot solve any problem within an organization. There are certain types of improvements for which other methods should be used. Process Improvements (such as “Six Sigma” type analysis) aimed at yield improvement and variation/scrap reduction are key examples. Suppose that a particular process has a first-pass yield of only 85% when it would need to be much closer to 100% to run in a one-piece flow environment. If the process must be analyzed using experiments and statistical methods, it would make sense to utilize a team but not a kaizen event. To implement these type of improvements, a problem solving team (or a six sigma team) that meets regularly over a period of time works better than a kaizen team meeting for five consecutive days.
In order to utilize kaizen events effectively, it is important to understand the types of problems for which kaizen events should and should not be used. With proper planning, kaizen events can bring breakthrough improvement to an organization on its lean journey.
Darren Dolcemascolo
The Power of Kaizen
Are Kaizen events effective? Based on the successes observed in companies like Toyota and countless other “lean” companies such as Wiremold, Pratt & Whitney, and others that have been studied by lean gurus over the years; kaizen events are very effective and very powerful. However, some organizations have failed at implementing lean and kaizen events. What is the source of the power seen in successful kaizen events? Part of the reason Kaizen events are powerful is because they are carefully selected and planned. While we have addressed these important issues in other articles, there is one single factor that contributes more to the power behind kaizen than any other: people! While that may sound trite, people are in fact the power behind kaizen. Do “better” people result in “better” kaizen events? No. Toyota, by far the most successful of all “lean” companies and the inventor of lean, does not believe in hiring the so-called superstars. Toyota in Japan generally hires people directly out of school to avoid their having to “un-learn” bad habits. They believe in developing exceptional people around a lean culture. The lean culture is developed through basically five key areas:
Training: All new employees should be trained in the lean system being employed at the company. Other employees should receive on-going training. Some of this training will happen during Kaizen events. Toyota trains all of its employees in its system; this is also part of their employee orientation.
Lay-off Policy: At a successful lean organization, people cannot lose their jobs due to lean successes. If employees even suspect that they might lose their jobs due to kaizen event improvements, they will not contribute to the best of their ability. One of my colleagues visited a manufacturer in the northwestern U.S. that employs these principles. They have Kaizen events happening nearly every week. Labor requirements are reduced in almost every kaizen activity; “displaced” individuals are never laid off. They are placed in a continuous improvement or kaizen office, where they contribute to further improvements around the plant. As demand increases, they are brought back into a production function. (Recall that a growth strategy must be part of lean since lean frees up resources.)
Incentives/Metrics: Improvements must have incentive at all levels. Operators must have incentive to make improvement suggestions (and implement). Management and support personnel must have incentives to make productivity and quality improvements through kaizen. Where many companies fail is that they measure and provide incentives to employees based on one standard (such as shipping out product), but they expect continuous improvement. This does not work: incentives must be in line with expectations. If a company expects continuous improvement, it must provide incentives. Incentives can range from recognition to monetary rewards.
Team Environment: Teamwork is important, but it is often misunderstood. Following is what one American executive at Toyota said regarding teamwork:
“Respect for people and a constant challenging to do better- are these contradictory? Respect for people means respect for the mind and capability. You do not expect them to waste their time. You respect the capability of the people. Americans think teamwork is about you liking me and I liking you. Mutual respect and trust means I trust and respect that you will do your job so that we are successful as a company. It does not mean that we just love each other.” (The Toyota Way by Jeffrey Liker, page 184)
At Toyota, all levels of the organizations are respected; each part of the team has a particular job that contributes to the company’s success. Additionally, each person is respected for his or her mind and ideas as well.
Empowerment: On the list of words that have been overused, “empowerment” is near the top. To empower means to enable. A lean organization must enable its employees to make improvements. Too often, suggestion programs have failed because people are asked to implement “other people’s” ideas. One of the most overlooked elements of a lean implementation is empowering employees. Employees need to be able to suggest and implement their ideas.
If a lean culture is implemented as described above, kaizen events will be successful. Employees on kaizen teams will:
Have the incentive to succeed.
Have the necessary training to succeed.
Not worry that they may be working themselves out of a job.
Believe that they are important to the success of the organization.
Believe that their ideas are respected and wanted.
Therefore, employees will inevitably succeed. The power of kaizen is in the people.
Darren Dolcemascolo
Training: All new employees should be trained in the lean system being employed at the company. Other employees should receive on-going training. Some of this training will happen during Kaizen events. Toyota trains all of its employees in its system; this is also part of their employee orientation.
Lay-off Policy: At a successful lean organization, people cannot lose their jobs due to lean successes. If employees even suspect that they might lose their jobs due to kaizen event improvements, they will not contribute to the best of their ability. One of my colleagues visited a manufacturer in the northwestern U.S. that employs these principles. They have Kaizen events happening nearly every week. Labor requirements are reduced in almost every kaizen activity; “displaced” individuals are never laid off. They are placed in a continuous improvement or kaizen office, where they contribute to further improvements around the plant. As demand increases, they are brought back into a production function. (Recall that a growth strategy must be part of lean since lean frees up resources.)
Incentives/Metrics: Improvements must have incentive at all levels. Operators must have incentive to make improvement suggestions (and implement). Management and support personnel must have incentives to make productivity and quality improvements through kaizen. Where many companies fail is that they measure and provide incentives to employees based on one standard (such as shipping out product), but they expect continuous improvement. This does not work: incentives must be in line with expectations. If a company expects continuous improvement, it must provide incentives. Incentives can range from recognition to monetary rewards.
Team Environment: Teamwork is important, but it is often misunderstood. Following is what one American executive at Toyota said regarding teamwork:
“Respect for people and a constant challenging to do better- are these contradictory? Respect for people means respect for the mind and capability. You do not expect them to waste their time. You respect the capability of the people. Americans think teamwork is about you liking me and I liking you. Mutual respect and trust means I trust and respect that you will do your job so that we are successful as a company. It does not mean that we just love each other.” (The Toyota Way by Jeffrey Liker, page 184)
At Toyota, all levels of the organizations are respected; each part of the team has a particular job that contributes to the company’s success. Additionally, each person is respected for his or her mind and ideas as well.
Empowerment: On the list of words that have been overused, “empowerment” is near the top. To empower means to enable. A lean organization must enable its employees to make improvements. Too often, suggestion programs have failed because people are asked to implement “other people’s” ideas. One of the most overlooked elements of a lean implementation is empowering employees. Employees need to be able to suggest and implement their ideas.
If a lean culture is implemented as described above, kaizen events will be successful. Employees on kaizen teams will:
Have the incentive to succeed.
Have the necessary training to succeed.
Not worry that they may be working themselves out of a job.
Believe that they are important to the success of the organization.
Believe that their ideas are respected and wanted.
Therefore, employees will inevitably succeed. The power of kaizen is in the people.
Darren Dolcemascolo
Thursday, June 28, 2007
The Ten Commandments of Good Listening
1. Stop Talking! You cannot listen if you are talking.2. Put the talker at ease. Help the talker feel that he or she is free to talk.
3. Show the talker that you want to listen. Look and act interested. Do not read your mail while she or he talks.
4. Remove distractions. Don't doodle, tap, or shuffle papers.
5. Empathise with the talker. Try to put yourself in the talker's place so you can see that point of view.
6. Be patient. Allow plenty of time. Do not interrupt.
7. Hold your temper. An angry person gets the wrong meaning form words.
8. Go easy on argument and criticism. This puts the talker on the defensive.
9. Ask questions. This encourages the talker and shows you are listening.
10. Stop talking! This is the first and last, because all other commandments depend on it.
Tuesday, May 8, 2007
Mistake Proofing Overview
Mistake proofing is critical to the lean organization for creating and maintaining process stability. Process instability is one of the biggest problems organizations encounter when attempting to implement lean. Among the tools available to the lean practitioner to improve process stability, mistake proofing is one of the simplest, yet most effective.
For the manufacturer, mistake proofing techniques can be applied to the manufacturing process or the product design itself to prevent manufacturing errors. They can also be used outside of manufacturing: hospitals, financial institutions, and other service organization have successfully used mistake proofing techniques.
While mistake proofing in some forms has been around for a very long time, it was Toyota that formalized a system. Toyota’s Shigeo Shingo developed an approach called Zero Quality Control (ZQC). ZQC, sometimes referred to as “Zero Defects,” is based on the principle that defects are prevented by controlling the performance of a process so that it cannot produce defects even when a machine or person makes a mistake. Poka-Yoke or Mistake Proofing is one key aspect of ZQC. Poka-Yoke or Mistake Proofing systems use sensors or other devices that make it nearly impossible for an operator to make an error. They regulate the production process and prevent defects in one of two ways:
Control System – stops the equipment when an irregularity happens or locks a clamp on the workpiece to keep it from moving on when it is not completely processed. This is the better system since it is not operator dependent.
Warning System – signals the operators to stop the machine or address the problem. This type of system is operator dependent.
Basic Methods
There are three types of poke-a-yoke methods: contact methods, fixed-value methods, and motion-step methods.
Contact Methods detect whether a product makes physical or energy contact with a sensing device. An example of physical contact would be a limit switch that is pressed when screws are attached to a product. An energy contact example would be photoelectric beams that sense when something is not in the correct position. Some of the best contact methods are passive devices such as guide pins or blocks that don’t allow a product to be positioned incorrectly. Many times such simple devices can be designed in to a product.
Fixed-value methods should be used when a fixed number of parts much be attached to a product or a fixed number of operations need to be done at a workstation. Under this method, a device counts the number of times something is done and signals or releases the product when the value is reached.
Motion-step methods detect whether a motion or step has happened within a certain period of time. Also, they can be used to ensure that events happened according to a certain sequence. These methods generally utilize sensors and devices like a photoelectric switch connected to a timer. An example would be a label dispenser that uses a photoelectric switch to stop the line if it does not detect removal of a label within the machine’s cycle time.
Types of Sensing Devices
There are three categories of sensing devices used in Poke-a-Yoke applications:
· Physical Contact Sensing Devices
· Energy Sensing Devices
· Sensors that detect changes in physical conditions
Physical Contact Sensing Devices
This type of device works by physically touching a product or part of a machine. In most automated applications, the device sends an electrical signal when contact is made. Some examples of such devices include:
Limit Switches – These confirm the presence and position of objects that touch the small lever on the switch. These are among the most common and least expensive devices.
Touch Switches – These are similar to limit switches; however, they are activated by a light touch on a thin “antenna.”
Trimetron – These are sensitive needle gauges that send signals to sound an alarm or stop equipment when a measurement is outside the acceptable range.
Energy Sensing Devices
This type of device uses energy rather than physical contact to determine whether an error is occurring. Examples of such devices include:
Proximity Switches – These devices use beams of light to inspect transparent objects, judge welds, and verify conditions such as (a) proper color or size of an object, (b) passage of objects on a conveyor, (c) proper supply of parts, or (d) proper feeding of parts.
Beam Sensors – These sensors are similar to proximity switches; however, they use beams of electrons to detect.
Other types of energy sensing devices include:
· Fiber sensors
· Area sensors
· Position sensors
· Dimension sensors
· Vibration sensors
· Displacement sensors
· Top sensors
· Metal passage sensors
· Color mark sensors
· Double-feed sensors
· Weld position sensors
Sensors That Detect Changes in Physical Position
This type of sensor detects condition changes such as pressure, temperature, or electrical current. Examples include pressure gauges, thermostats, and meter relays.
Mistake proofing is a powerful tool for the lean enterprise. It can be applied to almost any process to create more stability. However, it is important to implement mistake proofing systems where they are needed most. To find out how to best implement these systems, read our article entitled “Implementing Mistake Proofing Systems.”
For the manufacturer, mistake proofing techniques can be applied to the manufacturing process or the product design itself to prevent manufacturing errors. They can also be used outside of manufacturing: hospitals, financial institutions, and other service organization have successfully used mistake proofing techniques.
While mistake proofing in some forms has been around for a very long time, it was Toyota that formalized a system. Toyota’s Shigeo Shingo developed an approach called Zero Quality Control (ZQC). ZQC, sometimes referred to as “Zero Defects,” is based on the principle that defects are prevented by controlling the performance of a process so that it cannot produce defects even when a machine or person makes a mistake. Poka-Yoke or Mistake Proofing is one key aspect of ZQC. Poka-Yoke or Mistake Proofing systems use sensors or other devices that make it nearly impossible for an operator to make an error. They regulate the production process and prevent defects in one of two ways:
Control System – stops the equipment when an irregularity happens or locks a clamp on the workpiece to keep it from moving on when it is not completely processed. This is the better system since it is not operator dependent.
Warning System – signals the operators to stop the machine or address the problem. This type of system is operator dependent.
Basic Methods
There are three types of poke-a-yoke methods: contact methods, fixed-value methods, and motion-step methods.
Contact Methods detect whether a product makes physical or energy contact with a sensing device. An example of physical contact would be a limit switch that is pressed when screws are attached to a product. An energy contact example would be photoelectric beams that sense when something is not in the correct position. Some of the best contact methods are passive devices such as guide pins or blocks that don’t allow a product to be positioned incorrectly. Many times such simple devices can be designed in to a product.
Fixed-value methods should be used when a fixed number of parts much be attached to a product or a fixed number of operations need to be done at a workstation. Under this method, a device counts the number of times something is done and signals or releases the product when the value is reached.
Motion-step methods detect whether a motion or step has happened within a certain period of time. Also, they can be used to ensure that events happened according to a certain sequence. These methods generally utilize sensors and devices like a photoelectric switch connected to a timer. An example would be a label dispenser that uses a photoelectric switch to stop the line if it does not detect removal of a label within the machine’s cycle time.
Types of Sensing Devices
There are three categories of sensing devices used in Poke-a-Yoke applications:
· Physical Contact Sensing Devices
· Energy Sensing Devices
· Sensors that detect changes in physical conditions
Physical Contact Sensing Devices
This type of device works by physically touching a product or part of a machine. In most automated applications, the device sends an electrical signal when contact is made. Some examples of such devices include:
Limit Switches – These confirm the presence and position of objects that touch the small lever on the switch. These are among the most common and least expensive devices.
Touch Switches – These are similar to limit switches; however, they are activated by a light touch on a thin “antenna.”
Trimetron – These are sensitive needle gauges that send signals to sound an alarm or stop equipment when a measurement is outside the acceptable range.
Energy Sensing Devices
This type of device uses energy rather than physical contact to determine whether an error is occurring. Examples of such devices include:
Proximity Switches – These devices use beams of light to inspect transparent objects, judge welds, and verify conditions such as (a) proper color or size of an object, (b) passage of objects on a conveyor, (c) proper supply of parts, or (d) proper feeding of parts.
Beam Sensors – These sensors are similar to proximity switches; however, they use beams of electrons to detect.
Other types of energy sensing devices include:
· Fiber sensors
· Area sensors
· Position sensors
· Dimension sensors
· Vibration sensors
· Displacement sensors
· Top sensors
· Metal passage sensors
· Color mark sensors
· Double-feed sensors
· Weld position sensors
Sensors That Detect Changes in Physical Position
This type of sensor detects condition changes such as pressure, temperature, or electrical current. Examples include pressure gauges, thermostats, and meter relays.
Mistake proofing is a powerful tool for the lean enterprise. It can be applied to almost any process to create more stability. However, it is important to implement mistake proofing systems where they are needed most. To find out how to best implement these systems, read our article entitled “Implementing Mistake Proofing Systems.”
Mistake Proofing Systems: 7 Keys to Successful Implementation
Mistake proofing is a powerful tool for creating more stable processes by reducing defects. Processes with high defect rates are very problematic for the lean producer: such processes are not conducive to a lean value stream because they require overproduction to ensure that demand is met. This article will teach you how to implement an effective mistake proofing system. This article talks about seven keys to implementing an effective mistake proofing system:
Key #1: Create a team and always include those people that work on process in question. Organizations still have the tendency to turn to “technical experts” working in isolation to implement poka-yoke systems. Involving operators in a team setting will dramatically increase the likelihood of success. A kaizen blitz event is one very effective team activity for implementing mistake proofing.
Key #2: Use Value Stream Mapping to determine where process stability must improve. (If you are not familiar with value stream mapping, go back and read our series of articles on the subject.) This will allow you to focus on areas that will impact continuous flow.
Key #3: Use process mapping within the area selected. If you are implementing mistake proofing as a part of a kaizen blitz event, then this step should be done as a matter of course. However, if you are not using this methodology, you still need to map the current state process in detail. This will clearly identify each process step.
Key #4: Use a simple problem solving methodology like a fishbone diagram to determine root causes of problems within the process. This will identify those specific steps in the process that need mistake proofing.
Key #5: Use the simplest technology that will work when implementing a poka-yoke. Many times, low-tech solutions like guide pins and limit switches will work effectively. However, there are times when more complicated systems are necessary.
Key #6: Use control systems instead of warning systems wherever practical because control systems are not operator-dependent. (Control systems stop equipment when an irregularity happens, while a warning system signals the operator to take action).
Key #7: Have a standard form for every “Poka-Yoke” that indicates the:
· Problem being addressed
· Emergency alarm that will sound
· Action to be taken in an emergency
· Method and frequency of confirming it is operating correctly
· Method to perform a quality check in case of breakdown
Mistake proofing systems are critical to the success of a lean organization simply because process stability is so critical. Using the above seven keys will improve the likelihood of implementing a successful mistake proofing program.
Key #1: Create a team and always include those people that work on process in question. Organizations still have the tendency to turn to “technical experts” working in isolation to implement poka-yoke systems. Involving operators in a team setting will dramatically increase the likelihood of success. A kaizen blitz event is one very effective team activity for implementing mistake proofing.
Key #2: Use Value Stream Mapping to determine where process stability must improve. (If you are not familiar with value stream mapping, go back and read our series of articles on the subject.) This will allow you to focus on areas that will impact continuous flow.
Key #3: Use process mapping within the area selected. If you are implementing mistake proofing as a part of a kaizen blitz event, then this step should be done as a matter of course. However, if you are not using this methodology, you still need to map the current state process in detail. This will clearly identify each process step.
Key #4: Use a simple problem solving methodology like a fishbone diagram to determine root causes of problems within the process. This will identify those specific steps in the process that need mistake proofing.
Key #5: Use the simplest technology that will work when implementing a poka-yoke. Many times, low-tech solutions like guide pins and limit switches will work effectively. However, there are times when more complicated systems are necessary.
Key #6: Use control systems instead of warning systems wherever practical because control systems are not operator-dependent. (Control systems stop equipment when an irregularity happens, while a warning system signals the operator to take action).
Key #7: Have a standard form for every “Poka-Yoke” that indicates the:
· Problem being addressed
· Emergency alarm that will sound
· Action to be taken in an emergency
· Method and frequency of confirming it is operating correctly
· Method to perform a quality check in case of breakdown
Mistake proofing systems are critical to the success of a lean organization simply because process stability is so critical. Using the above seven keys will improve the likelihood of implementing a successful mistake proofing program.
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