What is Lean Manufacturing?
Lean Manufacturing are several tools that will help you eliminate all the operations that do not add value to the product, service and processes, increasing the value of each activity carried out and eliminating what is not required.
lean-manufacturingReduce waste and improve operations, always based on respect for the worker. Lean Manufacturing was born in Japan and was conceived by the great gurus of the Toyota Production System: William Edward Deming, Taiichi Ohno, Shigeo Shingo, Eijy Toyoda among a few.
The Flexible Manufacturing or Lean Manufacturing system has been defined as a philosophy of manufacturing excellence, based on:
- The planned elimination of all types of waste Respect for the worker: Kaizen Consistent improvement of Productivity and Quality
Lean Manufacturing Goals
The main objectives of Lean Manufacturing is to implement a philosophy of Continuous Improvement that allows companies to reduce costs, improve processes and eliminate waste to increase customer satisfaction and maintain profit margin.
Lean Manufacturing provides companies with tools to survive in a global market that demands higher quality, faster delivery at a lower price and in the required quantity. Specifically, Lean Manufacturing:
- Reduce waste chain dramatically Reduce inventory and shop floor space Create more robust production systems Create appropriate material delivery systems Improve plant layouts to increase flexibility
Benefits
The implementation of Lean Manufacturing is important in different areas, since different tools are used, therefore it benefits the company and its employees. Some of the benefits it generates are:
- 50% reduction in production costs Reduction of inventories Reduced delivery time (lead time) Better Quality Less labor Increased equipment efficiency Reduced waste
- Overproduction Waiting time (delays) Transportation The process Inventories Movements Poor quality
Lean Thinking
The fundamental part in the process of developing a lean strategy is that of the personnel, since it often involves radical changes in the way of working, something that by nature causes distrust and fear. What the Japanese discovered is that more than a technique, it is a good regime of human relations. In the past, the intelligence and creativity of the worker has been wasted, and he is hired as if he were a machine. It is very common that when an employee at the lower levels of the organization comes up with an idea or proposal, they are criticized and even shut up. Managers sometimes don't understand that every time they 'turn off the light' on a worker, they are wasting money. The concept of Lean Manufacturing implies the removal of controls and their replacement by leadership.The word leader is the key.
The 5 Principles of Lean Thinking
- Define the Value from the customer's point of view:
Most customers want to buy a solution, not a product or service.
- Identify your Value stream:
Eliminate waste by finding steps that do not add value, some are unavoidable and
others are eliminated immediately.
- Create Flow:
Make the whole process flow smoothly and directly from one step that adds value to another, from raw material to consumer
- Produce the Customer's "Jale":
Once the flow is done, they will be able to produce on customer orders instead of producing based on long-term sales forecasts.
- Pursue perfection:
Once a company achieves the first four steps, it becomes clear to those who are involved that adding efficiency is always possible.
The 5’S Lean Manufacturing Tools
This concept refers to the creation and maintenance of cleaner, more organized and safer work areas, that is, it is about giving a better "quality of life" to work. The 5'S come from Japanese terms that we put into practice daily in our daily lives and are not an exclusive part of a "Japanese culture" alien to us, indeed, all human beings, or almost all, have a tendency to practice or have practiced the 5'S, even if we don't realize it. The 5'S are:
- Classify, organize or arrange properly: S eiriOrdenar: S eitonLimpieza: S eisoEstandarizar: S eiketsuDisciplina: S hitsuke
When our work environment is disorganized and unclean we will lose efficiency and morale at work is reduced
Objectives of the 5'S
The central objective of the 5'S is to achieve the most efficient and uniform functioning of people in the workplace
Benefits of the 5'S
The implementation of a 5'S strategy is important in different areas, for example, it allows to eliminate waste and, on the other hand, it allows improving industrial safety conditions, thus benefiting the company and its employees. Some of the benefits generated by the 5'S strategies are:
- Higher levels of security that result in greater motivation of employees Higher quality Shorter response times Increase the useful life of equipment Generate organizational culture Reduction in losses and losses due to defective productions
Definition of the 5'S
Classify (seiri)
Classifying consists of removing from the work area or station all those elements that are not necessary to carry out the work, either in production areas or in administrative areas. An effective way to identify these items to be removed is called 'red tagging'. In effect, a red card (of expulsion) is placed on each item that is considered not necessary for the operation. These items are then taken to a temporary storage area. Later, if it was confirmed that they were unnecessary, these will be divided into two classes, those that are usable for another operation and the useless ones that will be discarded. This sorting step is a great way to free up floor space by discarding things such as: broken tools, fixtures, or obsolete tools,cuts and excesses of raw material. This step also helps eliminate the "Just In Case" mentality.
Classify consists of:
- Separate in the workplace the things that really work from those that do not work Classify the necessary from the unnecessary for routine work Maintain what we need and eliminate the excess Separate the elements used according to their nature, use, safety and frequency of use in order to facilitate agility at work Organize tools in places where changes can be made in the shortest time possible Eliminate elements that affect the operation of the equipment and that can cause breakdowns Eliminate unnecessary information and that can lead us to misinterpretation or performance
Benefits of classifying
Sorting prepares workplaces to make them safer and more productive. The first and most direct impact is related to safety. In the presence of unnecessary elements, the work environment is tense, it prevents a complete view of the work areas, it makes it difficult to observe the operation of equipment and machines, and emergency exits are obstructed, making the work area more insecure. Sort allows:
- Free up useful space in plant and officesReduce access times to material, documents, tools and other elements Improve visual control of spare stocks (inventories) and production elements, folders with information, plans, etc. Eliminate losses of products or elements that deteriorate due to remaining unused long time exposed in an environment not suitable for them; for example, packaging material, labels, plastic containers, cardboard boxes and others Facilitate visual control of raw materials that are running out and that are required for a process in a shift, etc. Prepare work areas for the development of autonomous maintenance, since the leaks, leaks and contaminations existing in the equipment can be easily appreciated and that are often hidden by unnecessary elements that are near the equipment
Sort (seiton)
The TPM makes it possible to differentiate an organization in relation to its competition due to the impact on cost reduction, improved response times, reliability of supplies, the knowledge that people have, and the quality of the final products and services. TPM looks for:
- Maximize team effectiveness Develop a productive maintenance system for the life of the equipment Involve all departments that plan, design, use, or maintain equipment in the implementation of TPM Actively involve all employees, from senior management to Floor workers Promote TPM through motivation with autonomous activities of small groups Zero accidents Zero defects Zero breakdowns
Objectives of the TPM
Strategic objectives
The TPM process helps build competitive capabilities from the company's operations, thanks to its contribution to improving the effectiveness of production systems, flexibility and response capacity, reducing operating costs, and maintaining industrial "knowledge".
Operational objectives
The purpose of the TPM in the daily actions is that the equipment operates without breakdowns and failures, eliminate all kinds of losses, improve the reliability of the equipment and truly use the installed industrial capacity.
Organizational objectives
The TPM seeks to strengthen teamwork, increase worker morale, create a space where each person can contribute their best, all this, with the purpose of making the workplace a creative, safe, productive and where to work is really pleasant.
TPM Features:
- Maintenance actions at all stages of the equipment life cycle Wide participation of all the people in the organization It is observed as a global company strategy, rather than a system to maintain equipment Aimed at improving the Global Effectiveness of operations, instead of providing attention to keeping the equipment working Significant intervention of the personnel involved in the operation and production in the care and conservation of the equipment and physical resources
- Maintenance processes based on the deep use of the knowledge that the personnel have about the processes
TPM benefits
Organizational
- Improvement of the quality of the work environment Better control of operations Increased employee morale Creation of a culture of responsibility, discipline and respect for rules Lifelong learning Creation of an environment where participation, collaboration and creativity is a reality Proper sizing of personnel templates Communication networks effective
Security
- Improving environmental conditions Culture for the prevention of negative health events Increasing the ability to identify potential problems and seeking corrective actions Understand the why of certain standards, rather than how to do it Prevention and elimination of potential causes of accidents Radically eliminate sources of contamination and pollution
Productivity
- Eliminate losses that affect plant productivity Improve equipment reliability and availability Reduce maintenance costs Improve final product quality Lower financial cost for changes Improve company technology Increase responsiveness to market movements Create competitive capabilities from the factory
Pillars of the TPM
The pillars or fundamental processes of the TPM serve as support for the construction of an orderly production system. They are implemented following a disciplined, powerful and effective methodology. The pillars considered necessary for the development of the TPM in an organization are those indicated below:
Pillar 1: Focused Improvements (Kaizen)
Focused improvements are activities that are developed with the intervention of the different areas involved in the production process, in order to maximize the Global Effectiveness of the Equipment, process and plant; all this through organized work in multidisciplinary teams, using specific methodology and concentrating its attention on the elimination of waste that occurs in industrial plants.
It is about developing a continuous improvement process similar to the one that exists in Total Quality Control processes, applying maintenance procedures and techniques. If an organization has similar improvement activities, it can simply incorporate into its process, Kaizen or improvement, new tools developed in the TPM environment. You should not modify your current improvement process that you currently apply.
Pillar 2: Autonomous Maintenance (Jishu Hozen)
Autonomous maintenance is composed of a set of activities that are carried out daily by all workers in the equipment they operate, including inspection, lubrication, cleaning, minor interventions, change of tools and parts, studying possible improvements, analyzing and solving equipment problems and actions that lead to keeping the equipment in the best operating conditions. These activities must be carried out following previously prepared standards with the collaboration of the operators themselves. Operators must be trained and have the knowledge necessary to master the equipment they operate.
The fundamental objectives of autonomous maintenance are:
- Using the equipment as an instrument for learning and acquiring knowledge Developing new skills for analyzing problems and creating a new thinking about the work Through correct operation and permanent verification according to the standards, avoiding deterioration of the equipment Improving the operation of the equipment with The creative input of the operator Build and maintain the necessary conditions for the equipment to function without breakdowns and full performance Improve safety at work Achieve a total sense of belonging and responsibility of the worker Improve morale at work
Pillar 3: Progressive or Planned Maintenance (Keikaku Hozen)
Progressive maintenance is one of the most important pillars in the search for profit in an industrial organization. The purpose of this pillar is the need to move gradually towards the goal of "zero breakdowns" for an industrial plant.
The planned maintenance that is practiced in many companies has the following limitations, among others:
- There is no historical information necessary to establish the most appropriate time to perform preventive maintenance actions. The times are established according to experience, manufacturer recommendations and other criteria with little technical foundation and without the support of data and historical information on past behavior. The stoppage of a team is used to "do everything necessary on the machine »Since we have it available. Will a similar intervention time be necessary for all the elements and systems of a piece of equipment? Will this be economical? Preventive maintenance plans are applied to equipment with high accumulated deterioration. This deterioration affects the dispersion of the (statistical) distribution of failures,making it impossible to identify a regular behavior of the failure and with which the preventive maintenance plan should be established.Equipment and systems are given a similar treatment from the point of view of the definition of preventive routines, regardless of their criticality, risk, effect on quality, degree of difficulty in obtaining the replacement or replacement, etc. It is rare that maintenance departments have specialized standards for carrying out their technical work. The usual practice is to print the work order with some assignments that do not indicate the detail of the type of action to be carried out. The planned maintenance work does not include Kaizen actions to improve work methods.Actions to improve technical capacity and improve the reliability of maintenance work are not included, nor is it frequent to observe the development of plans to eliminate the need for maintenance actions. This should also be considered as a preventive maintenance activity.
Pillar 4: Education and Training
This pillar considers all the actions that must be carried out for the development of skills to achieve high levels of performance of people in their work. It can be developed in steps like all TPM pillars and employs techniques used in autonomous maintenance, focused improvements, and quality tools.
Pillar 5: Early Maintenance
This pillar seeks to improve the technology of production equipment. It is essential for companies that compete in sectors of accelerated innovation, Mass Customization or versatile manufacturing, since in these production systems the continuous updating of the equipment, the capacity for flexibility and failure-free operation are extremely critical factors. This pillar acts during the planning and construction of the production equipment. For its development, information management methods are used about the operation of current equipment, economic project management actions, quality engineering techniques and maintenance. This pillar is developed through teams for specific projects. The departments of research, development and design, process technology, production,maintenance, planning, quality management and commercial areas.
Pillar 6: Quality Maintenance (Hinshitsu Hozen)
It is intended to establish equipment conditions at a point where "zero defects" is feasible. The quality maintenance actions seek to verify and measure the "zero defects" conditions regularly, in order to facilitate the operation of the equipment in the situation where quality defects are not generated.
Quality Maintenance is not…
- Apply quality control techniques to maintenance tasks Apply an ISO system to the maintenance function Use statistical quality control techniques to maintenance Apply continuous improvement actions to the maintenance function
Quality Maintenance is…
- Carry out maintenance actions aimed at caring for the equipment so that it does not generate quality defects Prevent quality defects by certifying that the machinery meets the conditions for "zero defects" and that these are within technical standards Observe the variations in the characteristics of the equipment to prevent defects and take actions in anticipation of the potential abnormality situation Carry out equipment engineering studies to identify the equipment elements that have a high incidence on the quality characteristics of the final product, carry out the control of these elements of the machine and intervene these elements
Principles of Quality Maintenance
The principles on which Quality Maintenance is based are:
- Classification of defects and identification of the circumstances in which they occur, frequency and effects Carry out a physical analysis to identify the equipment factors that generate quality defects Establish standard values for the characteristics of equipment factors and assess the results through of a measurement process Establish a periodic inspection system for critical characteristics Prepare maintenance matrices and periodically assess standards
Pillar 7: Maintenance in Administrative Areas
The purpose of this pillar is to reduce the losses that can occur in manual work in the offices. If about 80% of the cost of a product is determined in the product design and production system development stages. Productive maintenance in administrative areas helps to avoid loss of information, coordination, accuracy of information, etc. Employs focused improvement techniques, 5's strategy, autonomous maintenance actions, education and training, and job standardization. It is developed in the administrative areas with individual or team actions.
Pillar 8: Safety, Health and Environment Management
Its purpose is to create a comprehensive security management system. It employs methodologies developed for the pillars of focused improvement and autonomous maintenance. It contributes significantly to preventing risks that could affect the integrity of people and negative effects on the environment.
Pillar 9: Specials (Monotsukuri)
The purpose of this pillar is to improve the flexibility of the plant, implement postponement technology, level flow, apply Just in Time and other technologies to improve manufacturing processes.
Steps for TPM implementation
Step 1: Communicate senior management's commitment to introduce the TPM
A statement must be made from the highest-ranking executive in which the decision was made to implement TPM in the company
Step 2: Introductory educational campaign for the TPM
This requires the teaching of several TPM courses at the various levels of the company
Step 3: Establishing a promotional organization and machine maintenance model through a formal organization
This organization must be made up of:
- Plant managers Department and section managers Supervisors Staff
Step 4: Set basic policies and objectives
Goals must be in writing in documents that state that the TPM will be implemented as a means to achieve the goals.
You must first decide on the year in which the company will undergo internal or external audit
Set a numerical goal to be achieved for each category in that year
You should not set "lukewarm" goals, the goals should be drastic 1/100 reductions under the proposed objectives
Step 5: Design the TPM Master Plan
The best way is in a slow and permanent way
Plan from implementation to certification (TPM Excellence Award)
Step 6: Introductory Launch
It personally involves senior and mid-level people, who work on setting the settings for the launch, as this day is when TPM will be launched with the participation of all staff.
A tentative program would be:
- Declaration of the company in which it has decided to implement the TPM Announce the promotional organizations of the TPM, the fundamental goals and the master plan The union leader makes a strong declaration of initiating the activities of the TPM The guests offer a congratulatory speech The work developed is recognized through praise for the creation of logos, phrases and any other activity related to this topic
Step 7: Improving Team Effectiveness
In this step, the 6 large losses considered by the TPM will be eliminated, such as:
- Losses due to failures:
They are caused by defects in the equipment that require some kind of repair. These losses consist of downtime and the costs of the parts and labor required for the repair. The magnitude of the failure is measured by the dead time caused.
- Model change and fit losses:
They are caused by changes in operating conditions, such as starting a production run, starting a new shift of workers. These losses consist of downtime, changing molds or tools, heating, and machine adjustments. Its magnitude is also measured by dead time.
- Losses due to minor stoppages:
They are caused by machine outages, jamming, or waiting time. In general, these losses cannot be recorded directly, so the percentage of use is used (100% minus the percentage of use), in this type of loss the equipment is not damaged.
- Speed losses:
They are caused by reduced operating speed, because at higher speeds, quality defects and minor stoppages occur frequently.
- Loss of quality defects and rework:
They are products that are out of specification or defective, produced during normal operations, these products have to be reworked or eliminated. Losses consist of the work required to make up the defect or the cost of the wasted material.
- Performance losses:
They are caused by wasted or unused materials and are exemplified by the amount of materials returned, thrown away or discarded.
Total effective equipment productivity (PTEE) concept
The PTEE is a measure of the actual productivity of the teams. This measure is obtained by multiplying the following indicators:
PTEE = AE X OEE
AE-Use of the equipment
This is a measure that indicates the amount of calendar time used by teams. AE is more related to directive decisions about the use of available calendar time than to the operation of the equipment itself. This measure is sensitive to how long the equipment could have operated, but for various reasons the equipment was not programmed to produce 100% of the time. Another factor that affects the use of the equipment is the time used to carry out planned preventive maintenance actions. AE can be interpreted as a percentage of the calendar time that a team has used to produce.
To calculate the AE, the steps detailed below can be applied.
- Set the calculation base time or calendar time (TC).
It is common in manufacturing companies to take the calculation base 1440 minutes or 24 hours. For continuous process companies that perform annual plant inspection, consider calendar time as (365 days * 24 hours).
- Get the total unscheduled time
If a company works only two shifts (16 hours), the unscheduled operating time in a month will be 240 hours.
- Get planned stoppage time
The time used to carry out preventive maintenance actions, breaks, scheduled meetings with operators, continuous improvement meetings, etc. is added.
- Calculate the operating time (TF )
It is the total time the equipment or plant is expected to operate. It is obtained by subtracting from the TC, the time spent on planned maintenance and total unscheduled time.
TF = Calendar time - (Total unscheduled time + Planned downtime)
AE = (TF / TC) X 100
Y represents the percentage of calendar time that is actually used to produce and is expressed as a percentage.
OEE-Overall Equipment Effectiveness
This metric assesses the performance of the computer while it is running. The OEE is strongly related to the state of conservation and productivity of the equipment while it is operating.
This indicator shows the real losses of the equipment measured in time. This indicator is possibly the most important to know the degree of competitiveness of an industrial plant. It should be noted that these indicators are managed on a daily basis, so the data on planned shutdowns and unscheduled shutdowns vary with those used in the EA and is made up of the following three factors:
- Availability: Measures the loss of equipment availability due to unscheduled shutdowns.
Availability =
Where:
Net time available = Overtime + Total time programmed + Stop time allowed
Operating time = Net time available - Line stop time
- Efficiency: Measures the performance losses caused by equipment malfunction, not operating at the original speed and performance determined by the equipment manufacturer or design.
Efficiency =
Where:
Touch time =
- First Time Quality (FTT): These quality losses represent the time taken to produce products that are defective or have quality problems. This time is wasted, as the product must be destroyed or re-processed. If all the products are perfect, these losses of time of the equipment operation do not occur.
FTT =
Where:
Total defective parts: Defective parts + reworks or recoveries
The calculation of the OEE is obtained by multiplying the previous three terms expressed as a percentage.
OEE = Availability X Efficiency X FTT
Figure 5. TPM indicators
Why is OEE important?
This indicator responds elastically to the actions carried out for both autonomous maintenance and other TPM pillars. A good initial OEE measurement helps to identify critical areas where a TPM pilot could be initiated. It serves to justify to senior management about the need to offer the support of resources necessary for the project and to control the degree of contribution of the improvements achieved in the plant.
The figures that make up the OEE help us to guide the type of TPM actions and the class of instruments that we must use to study the problems and phenomena. The OEE is used to build comparative indices between plants (benchmarking) for similar or different equipment. In those complex production lines the OEE may have to be calculated for the component equipment. This information will be useful to define the type of equipment in which it is necessary to influence with higher priority with TPM actions. Some plant managers find that obtaining a global OEE value for a complex process or plant is not entirely useful, as it can combine multiple causes that change daily and the effect of TPM actions is not adequately appreciated in the global OEE. For this reason, it is better to get an OEE value per equipment,with special attention to those who have been selected as pilot or model.
It is frequent that the information is fragmented in the different departments of the company and the AE and OEE are not calculated. This leads to each department taking care of its indices. However, the multiplicative effect of availability, performance and quality levels produce a deterioration of the AE and OEE, not being observed by the company's managers.
Maintenance personnel are often in charge of controlling the availability of equipment as this measures the general efficiency of the department. Availability is a measure of equipment performance. However, in the maintenance area it is common to ignore the performance level values of these equipment. If this level deteriorates, the cause is questioned and problems that are operative and that have nothing to do with the maintenance function are frequently assumed to be the cause. This lack of teamwork and common interests makes it more difficult to obtain the true sources of loss. For this reason, if there are frequent behaviors in a company such as "I repair the equipment and you operate it", it will be impossible to improve the OEE of a plant.
Step 8: Establish a self-contained maintenance maintenance program for operators
Autonomous maintenance requires operators to understand or know their equipment, so 3 skills are required:
- A clear understanding of the criteria for judging normal and abnormal conditions A strict effort to maintain equipment condition A rapid response to abnormalities (ability to repair and restore equipment condition)
Step 9: Prepare a schedule for the maintenance schedule
The purpose of the program is to improve the functions of: conservation, prevention, prediction, correction and technological improvement
Step 10: Conduct training to improve operation and maintenance skills. The training consists of the following topics:
- General Diagnostic Techniques Basic Equipment Diagnostic Techniques Vibration Theory General Inspection Rules Lubrication
Step 11: Developing an Initial Program for Team Management
Which will have as objectives:
- Guarantee 100% product quality Guarantee the initial and operating cost anticipated Guarantee planned equipment operation and efficiency
Step 12: Fully implement and support goals
Using the following implementation phases:
- Planning and repair of TPM implementation Pilot installation Installation to the entire plant
Level Production (Heijunka)
Heijunka, or Leveled Production is a technique that adapts production to fluctuating customer demand. The Japanese word Heijunka (pronounced eh June kah), literally means "make flat and level." Customer demand must be met by customer's required delivery, but customer demand is fluctuating, while factories prefer it to be "level" or stable. A manufacturer needs to match these production demands.
The main tool for smoothing production is the frequent change of the exemplary mixture to be run on a given line. Instead of running large batches of one model after another, small batches of many models should be produced in short periods of time. This requires faster changeover times, with small batches of good parts delivered more frequently.
Process verification (Jidoka)
The word "Jidoka" means in-process verification, when Jidoka systems are installed in the production process it refers to quality verification integrated into the process.
The Jidoka philosophy establishes the optimal quality parameters in the production process, the Jidoka system compares the production process parameters against the established standards and makes the comparison, if the process parameters do not correspond to the pre-established standards the process stops, alerting that there is an unstable situation in the production process which must be corrected, this in order to avoid mass production of defective parts or products, the Jidoka processes are comparative systems of the "ideal" or "standard" against the results current in production. There are different types of Jidoka systems: vision, strength, length, weight, volume, etc. It depends on the product is the type or design of the Jidoka system that must be implemented, like any system,the information that is fed as "ideal" or "standard must be the optimum quality point of the product.
Jidoka can refer to equipment that stops automatically under abnormal conditions. Jidoka is also used when a team member encounters a problem on their workstation. Team members are responsible for correcting the problem - if they can't, they can stop the line. Jidoka's goal can be summarized as:
- Quality assuring 100% of the time Equipment breakdowns preventing Manpower using effectively
Devices to prevent errors (Poka Yoke)
The term "Poka Yoke" comes from the Japanese words "poka" (inadvertent mistake) and "yoke" (to prevent). A Poka Yoke device is any mechanism that helps prevent errors before they happen, or makes them too obvious for the worker to notice and correct in time. The purpose of Poka Yoke is to eliminate defects in a product by either preventing or correcting errors that occur as soon as possible.
Poka Yoke systems involve 100% inspection, feedback and immediate action when defects or errors occur. This approach solves the problems of the old belief that 100% inspection takes a lot of time and labor and therefore comes at a very high cost.
A Poka Yoke system has two functions: one is to inspect 100% of the parts produced, and the second is if abnormalities occur, it can provide feedback and corrective action. The effects of the Poka Yoke method in reducing defects will depend on the type of inspection that is being carried out, either: at the start of the line, self-check, or continuous check.
Poka Yoke regulatory functions
Control methods
There are methods that when abnormalities occur, they turn off the machines or block the operating systems, preventing the same defect from occurring. These types of methods have a much stronger regulatory function than preventive ones, and therefore this type of control system helps to maximize efficiency to achieve zero defects.
Not in all cases where control methods are used is it necessary to turn off the machine completely, for example when there are isolated defects (not in series) that can be corrected later, it is not necessary to turn off the machinery completely, a mechanism can be designed that allows «Mark» the defective part, for its easy location; and then correct it, thus avoiding having to stop the machine completely and continue with the process.
Warning Methods
This type of method warns the worker of the abnormalities that have occurred, drawing their attention, by activating a light or sound. If the worker does not notice the warning sign, the defects will continue to occur, so this type of method has a less powerful regulatory function than that of control methods.
In any situation, control methods are far more effective than warning methods, so control-type methods should be used as much as possible. The use of warning methods should be considered when the impact of abnormalities is minimal, or when technical and / or economic factors make the implementation of a control method extremely difficult.
Classification of Poka Yoke methods
- Contact methods. They are methods where a sensitive device detects abnormalities in the finish or dimensions of the part, where there may or may not be contact between the device and the product. Fixed value method. With this method, abnormalities are detected by inspecting a specific number of movements, in cases where the operations must be repeated a predetermined number of times. Step-movement method.These are methods in which abnormalities are detected by inspecting errors in standard moves where operations are performed with predetermined moves. This extremely effective method has a wide range of application, and the possibility of its use should be considered whenever the implantation of a Poka Yoke device is being planned.
Meters Used in Poka Yoke Systems
Meter types can be divided into three groups:
- Contact meters
Limit switch, microswitches. These verify the presence and position of objects and detect broken tools, etc. Some of the limit switches are equipped with lights for easy use.
Tact switches. They are activated by detecting a light in its receiving antenna, this type of switches can detect the presence of objects, position, dimensions, etc., with high sensitivity.
Differential transformer. When contacted with an object, a differential transformer captures changes in contact angles as well as different lines in magnetic forces, this is helpful for objects with a high degree of precision.
Trimetron. A digital caliper is what forms the body of a «trimetron», the values of the limits of a piece can be easily detected, as well as its real position. This is a very convenient device since the limits are selected electronically, allowing the device to detect the measurements that are accepted, and the parts that do not comply are rejected.
Liquid level relay. This device can detect fluid levels using floats
- Non-contact meters
Proximity sensors. These systems respond to changes in distances from objects and changes in magnetic lines of force. For this reason they should be used on objects that are susceptible to magnetism.
Photoelectric switches (transmitters and reflectors). Photoelectric switches include the transmitter type, in which a beam transmitted between two photoelectric switches is interrupted, and the reflector type, which uses the reflection of light from the rays. Photoelectric switches are commonly used for non-ferrous parts, and reflector-type switches are very convenient for distinguishing differences between colors. They can also detect some areas by the difference between their color.
Light sensors (transmitters and reflectors). These types of detector systems make use of a beam of electrons. Light sensors can be reflector or transmitter type.
Fiber sensors. These are sensors that use optical fibers.
Area sensors. Most sensors detect only interruptions in lines, but area sensors can randomly detect interruptions in some area.
Position sensors. They are a type of sensors that detect the position of the piece.
Dimension sensors. They are sensors that detect if the dimensions of the part or product are correct.
Displacement sensors. These are sensors that detect deformation, thickness, and height levels.
Metal sensors. These sensors can detect when products pass or do not pass through a place, they can also detect the presence of metal mixed with excess material.
Color sensor. These sensors can detect colored markings, or differences between colors. Unlike photoelectric switches these do not necessarily have to be used on non-ferrous parts.
Vibration sensors. They can detect when an item is passing, the position of damaged areas and cables.
Double parts sensor. These are sensors that can detect two products that are passed at the same time.
Thread sensors. They are sensors that can detect incomplete thread machining.
Element fluid. These devices detect changes in air currents caused by the placement or movement of objects, they can also detect broken or damaged bits.
- Pressure, temperature, electric current, vibration, number of cycles, counting, and information transmission meters
Pressure change detector. The use of pressure gauges or pressure sensitive switches, allows to detect the oil leakage of a hose.
Temperature change detector. Changes in temperature can be detected by means of thermometers, thermostats, thermal couplings, etc. These systems can be used to detect the temperature of a surface, electronic parts and motors, to achieve adequate maintenance of machinery, and for all types of temperature measurement and control in the industrial environment.
Detectors of fluctuations in electric current. Metric relays are very convenient for being able to control the causes of defects by detecting electrical currents.
Abnormal vibration detectors. They measure abnormal vibrations of machinery that can cause defects, it is very convenient to use this type of vibration detectors.
Detectors for abnormal counts. For this purpose, counters should be used, either with relays or with fibers as sensors.
Time detectors and timings. Stopwatches, time relays, timed units, and time switches can be used for this purpose.
Meters of abnormalities in the transmission of information. Light or sound can be used, in some areas a sound is better as it captures the worker's attention more quickly since if he does not see the warning light, errors will continue to occur. The use of colors somewhat improves the ability to attract attention than plain light, but a flickering light is much better.
Comparison in the application of different types of devices against errors
The following figure indicates the types of devices against errors that currently exist, who uses them, the cost classified as low, medium, high or very high, how much maintenance it requires and the reliability of the device.
Figure 6. Types of Poka Yoke
It can be seen that as the application becomes more technological, the cost also increases. What you need to do is find the solution to the problem, not justify the purchase of a very expensive device.
Main characteristics of a good Poka Yoke system:
- They are simple and cheap. If they are too complicated or expensive, their use will not be profitable They are part of the process. They are part of the process, they carry out “100%” of the inspection They are placed near or at the place where the error occurs. Provide feedback quickly so mistakes can be corrected
Visual Indicator (Andon)
Japanese term for alarm, visual indicator or signal, used to show production status, uses audio and visual cues. It is a display of lights or luminous signals on a board that indicates the working conditions on the production floor within the work area, the color indicates the type of problem or working conditions. Andon means HELP!
The Andon can consist of a series of lamps in each process or a board of lamps that cover an entire area of production. The Andon in an assembly area will be activated via a pull cord or a push button by the operator. An Andon for an automated line can be interfaced with machines to draw attention to the current need for raw materials. Andon is a tool used to build quality in our processes.
If a problem occurs, the Andon table will illuminate to signal the supervisor that the workstation is in trouble. A melody is used in conjunction with the Andon chart to provide an audible cue to help the supervisor understand there is a problem in their area. Once the supervisor assesses the situation, he or she can take appropriate steps to correct the problem. The colors used are:
- Red: Machine broken down Blue: Defective part White: End of production batch Yellow: Waiting for model change Green: Lack of Material No light: System operating normally
Quick Model Change (SMED)
SMED stands for "Single digit model change in minutes". They are theories and techniques to perform model change operations in less than 10 minutes. From the last good piece to the first good piece in less than 10 minutes. The SMED system was born out of necessity to achieve Just-in-Time production. This system was developed to shorten machine preparation times, making it possible to make smaller batches in size. Model change procedures were simplified using the most common or similar items commonly used.
SMED objectives
- Facilitate small production batches Reject Inexpensive batch formula Run each part every day (make) Reach batch size to 1 Make first part right every time Model changeover in less than 10 minutes 3-step approach
- Eliminate external time (50%)
Much of the time is wasted thinking about what to do next or waiting for the machine to stop. Planning tasks reduces time (the order of parts, when changes take place, what tools and equipment are needed, who will be involved, and what inspection materials are needed). The objective is to transform the process into a systematic event, leaving nothing to chance. The idea is to move external time to external functions.
- Study the methods and practice (25%)
The study of times and methods will allow you to find the fastest and best way to find the remaining internal time. Nuts and bolts are one of the biggest cause of delay. The unification of measures and tools reduces time. Duplicating common parts for assembly will allow operations to be carried out externally, saving this time from internal operations.
For better and effective model changes, teams of people are required.
Two or more people collaborate in the positioning, scope of materials and use of tools. The efficiency is conditioned to the practice of the operation. The time spent in practice is well worth it as the results will improve.
- Clear settings (15%)
It implies that the best adjustments are those that are not needed, that is why they resort to fixing the positions.
It seeks to recreate the same circumstances as the last time.
As many adjustments can be made as outside work it is required to set the tools.
Adjustments require space to accommodate different types of dies, dies, punches, or tooling so standard clearances are required.
SMED benefits
- Produce in small batches Reduce inventories Process high-quality products Reduce costs Shorter lead times Be more competitive More reliable turnaround times More balanced load in daily production
Phases for reducing model change
Phase 1. Separate internal preparation from external
Internal preparation are all the operations that require the machine to be stopped and external those that can be done with the machine running. Once the machine is stopped, the operator must not leave it to carry out external operations. The objective is to standardize operations so that with the least amount of movements changes can be made quickly, this allows to reduce the size of the lots.
Phase 2. Convert as much of internal preparation as possible into external preparation
The idea is to do everything necessary to prepare - dies, dies, punches,… - outside the machine in operation so that when it stops, the necessary change is quickly made, so that it can start up quickly.
Phase 3. Eliminate the adjustment process
Adjustment operations typically represent 50 to 70% of the internal setup time. It is very important to reduce this setup time to shorten the total setup time. This means that it takes time to get the process up and running according to the new required specification. In other words, adjustments are usually associated with the relative position of parts and dies, but once the change is made it takes a while to get the first good product to work - it is actually called adjustment to non-conformities based on trial and error is coming to make the product according to specifications -. In addition, an extra amount of material is used.
Phase 4. Preparation optimization
There are two possible approaches:
- Use a uniform design of the products or use the same part for different products (assembly design); Produce the different parts at the same time (parallel design)
Phases for reducing model change
Figure 7. Phases for reducing model change
Techniques for reducing model change
- Standardize external preparation activities Standardize only the necessary parts of the machine Use a quick fastener Use a complementary tool Use parallel operations Use a mechanical preparation system
Continuous improvement (Kaizen)
It comes from two Japanese ideograms: "Kai" which means change and "Zen" which means to improve. Thus, we can say that "Kaizen" is "change to improve" or "continuous improvement." The two pillars that sustain Kaizen are work teams and Industrial Engineering, which are used to improve production processes. In fact, Kaizen focuses on people and standardization of processes. Its practice requires a team made up of production, maintenance, quality, engineering, purchasing, and other employees that the team deems necessary. Its objective is to increase productivity by controlling manufacturing processes by reducing cycle times, standardizing quality criteria, and working methods per operation. In addition, Kaizen also focuses on the elimination of waste,identified as "mute", in any of its six forms.
Kaizen strategy begins and ends with people. With Kaizen, a wrapped leadership guides people to continually improve their ability to meet expectations of high quality, low cost, and on-time delivery. Kaizen transforms companies into 'Top Global Competitors'.
Figure 9. Comparison Innovation vs. Kaizen
The ten commandments of Kaizen
- Waste ('mute' in Japanese) is public enemy number 1; To eliminate it you have to get your hands dirty. Continuous gradual improvements are not a one-off break. Everyone has to be involved, whether they are part of senior management or middle management, they are grassroots personnel, they are not elitist. In a cheap strategy, you believe in increased productivity without significant investments; It does not spend astronomical sums on technology and consultants. It applies anywhere; It is not only used for the Japanese. It relies on "visual management", on a total transparency of procedures, processes, values, makes problems and waste visible to everyone's eyes. Focuses attention on where It really creates value ('gemba' in Japanese). It is process oriented.Give priority to people, to "humanware"; believes that the main improvement effort should come from a new mentality and work style of people (personal orientation for quality, teamwork, cultivation of wisdom, elevation of morals, self-discipline, quality circles and practice of individual or group suggestions) The essential motto of organizational learning is learning by doing.
Steps to implement Kaizen
Step 1. Selection of study topic
The study topic can be selected using different criteria:
- Higher objectives of industrial management Quality problems and customer deliveries Organizational criteria Possibilities for replication in other areas of the plant Relationship with other continuous improvement processes Significant improvements to build competitive capacities from the plant Innovative factors and others
Step 2. Create the structure for the project
The frequently used structure is that of the multidisciplinary team. In this class of teams, workers from the different areas involved in the production process take part, such as supervisors, operators, technical maintenance personnel, purchases or warehouses, projects, process engineering and quality control.
Step 3. Identify the current situation and formulate objectives
In this step, a general problem analysis is necessary and the main losses associated with the selected problem are identified. In this phase, information on breakdowns, failures, repairs and other statistics on losses due to quality problems, energy, process capacity analysis and operation times must be collected or processed to identify bottlenecks, stops, etc.. This information should be presented in a graphical and stratified form to facilitate its interpretation and diagnosis of the problem. Once the study topics have been established, it is necessary to formulate objectives that guide the improvement effort.
Step 4: Diagnosing the problem
Before using analytical techniques to study and solve the problem, the basic conditions that ensure proper operation of the equipment must be established and maintained. These basic conditions include: cleaning, lubrication, routine checks, tightening of nuts, etc. Also important is the complete elimination of all those deficiencies and the causes of accelerated deterioration due to leaks, leaks, contamination, dust, etc. This implies conducting autonomous maintenance activities in the areas selected as a pilot for the realization of the targeted improvements.
The analytical techniques used most frequently in the study of equipment problems come from the field of quality. Due to their ease and simplicity, they can be used by the majority of workers in a plant. The techniques most used by study teams are:
- Why & Why method known as the knowing why technique Modal Analysis of Failures and Effects (AMFES) Primary cause analysis Function method of the physical principles of failure Value Engineering techniques Data analysis Traditional Quality Improvement techniques: seven tools Flow analysis and other techniques used in Just-in-Time, SMED, etc. production systems.
Step 5: Formulate action plan
Once the different causes of the problem have been investigated and analyzed, an action plan is established to eliminate the critical causes. This plan should include alternatives for possible actions. Based on these proposals, the specific activities and tasks necessary to achieve the formulated objectives are established. This plan must incorporate actions for both specialist personnel or support members such as engineering, projects, maintenance, etc., as well as actions that must be carried out by equipment operators and routine production support personnel such as machinists, packers, auxiliaries, etc.
Step 6: implement improvements
Once the actions have been planned in detail, they are implemented. It is important during the implementation of the actions to have the participation of all the people involved in the project, including the operating personnel. The improvements should not be imposed since if they are imposed by higher order they will not have the full support of the operational personnel involved. When trying to improve working methods, the opinions of the personnel who directly or indirectly intervene in the process must be consulted and taken into account.
Step 7: Evaluate the results
It is very important that the results obtained in an improvement are published on a billboard or panels, throughout the company which will help to ensure that each area benefits from the experience of the improvement groups.
Basic principles to start the implementation of Kaizen
- Discard the idea of making improvised arrangements Think about how to do it, not why I can't do it Don't make excuses, start wondering why it happens so often Don't rush for perfection, go for 50% of the goal first If you make a mistake, correct it immediately Don't spend money on Kaizen, use your wisdomWisdom comes from the face of adversityTo find the causes of all your problems, ask yourself five times Why? The wisdom of 10 people is better than the knowledge of one Kaizen ideas are endless
Kaizen Events
What is the Kaizen event?
It is a Continuous Improvement Program based on teamwork and the use of the skills and knowledge of the personnel involved. It uses different Lean Manufacturing tools to optimize the operation of a selected production process.
3.5.13.4.2 Purpose of the Kaizen Event
Improve the productivity of any chosen area or section in any company, through the implementation of various techniques and work philosophies of Lean Manufacturing and techniques for solving problems and detecting waste based on the encouragement and training of personnel.
Kaizen Event Benefits
The benefits may vary from company to company, but those typically found are as follows:
- Increased productivity Reduced space used Improvements in product quality Reduced inventory in process Reduced manufacturing time Reduced forklift use Improved production management and control Reduced production costs Increased profitability Improved service Improved flexibility Improved organizational climate The concept of responsibility clarifies roles
Implementation program
- Development of a commitment to the goals of the company
- Clear definition of goals and objectives Involvement and commitment of people Awards for efforts
- Establish incentives with staff
- Teamwork
- Leadership
The leader must pay attention and consider the problems. You must know how to listen, transmit positive attitudes and ideas.
- Measurement
It is done through graphics, action plans, improvement boards, etc.
How to organize a Kaizen event
- A Kaizen event is usually held in a week The specific objectives of the event are defined, which are generally to eliminate waste in the work area A multidisciplinary team of operators, supervisors, engineers and technicians is integrated According to the objective, training is given on the subject and very explanations simple, whether to improve the model change with SMED, eliminate transport and delays, maintain order and cleanliness with 5'S, autonomous maintenance with TPMS The people of the Kaizen Event are involved with their ideas for improvement on the objective, the Participants' ideas The area for improvement is analyzed, photos and videos are taken, everyone's ideas are discussed and analyzed, a work plan is generated and improvements are worked on
Process map
They are all the current actions required to produce a product through the main essential flows for each product:
- The production flow of the raw material from the moment it is in the customer's hands The flow design from concept to launch
It is a great drawing, not an individual process and the instructional as a whole, the part is not optimized. It is a drawing or visual representation of each process including the flow of material and the flow of information.
Why is the process map an essential tool?
- It helps to visualize more than the individual process, for example: assembly, welding, etc. in production. You can see the flow Helps see more waste Provide a common language to talk about manufacturing processes Make decisions about apparent flow so you can discuss it. Otherwise, many details and decisions in your warehouse happen because of not making the decisions. Show the connection between the flow of information and the flow of material. It is not just another tool It is more useful than a quantitative tool and the lay-outs produce a concordance so as not to add steps, delivery time, distance traveled, the amount of inventory The process map is a qualitative tool, which describes the order in detail of the flow
Bibliography
- Bonilla Bravo, Carlos Alexis, Imai, Masaaki, Gutiérrez Garza, Gustavo. Just in Time and Total Quality, Principles and Applications. Fifth edition. Ediciones Castillo SA de CV, Monterrey, Nuevo León, Mexico, 2000 Hodson William. Maynard, Manual of the Industrial Engineer. Volume II. Fourth edition. Mac Graw Hill, Mexico, September 2001
