What is Total Productive Maintenance?
First published by the Quality Methods Association and written by
David Hutchins, Chairman, David Hutchins International Limited
Total Productive Maintenance (TPM) which is one of the key concepts of Lean Manufacturing, challenges the view that maintenance is no more than a function that operates in the background and only appears when needed. The objective of TPM is to engender a sense of joint responsibility between supervision, operators and maintenance workers, not simply to keep machines running smoothly, but also to extend and optimise their performance overall. The results are proving to be remarkable.
The goals of TPM are measured using an Overall Equipment Effectiveness (OEE) ratio.
OEE = availability x performance x Quality rate.
Availability = Available time - downtime x 100
Downtime can be calculated by adding together the amounts of time lost due to equipment failures, set-up and adjustment, and idling and minor stoppages.
Performance rate = Ideal cycle time x Processed Quantity x 100
Speed losses are calculated by combining time lost due to idling and minor stoppages and time lost due to reductions in speed.
Quality rate = Processed Quantity - defective quantity x 100
Defective quantity is calculated by combining defects in process start-up and reduced yield.
Typical calculations for OEE prior to the implementation of Just in Time related strategies usually range between 40% and 50% with the former being the more normal. Experience indicates that it is possible to raise this to between 80% and 90% in a period of some two to three years from start up. However, the improvement will usually follow an almost exponential upward curve with the bulk of the gains being in the latter part of the period.
Total Productive Maintenance was developed in Japan in 1971 by the Japanese Institute of Plant Maintenance (JIPM). TPM involves everyone in the company.
The JIPM also identified what they refer to as the six big losses. These are as follows:-
The Six Big Losses.
“The goal of TPM is to increase the productivity of Plant and Equipment. Consequently, maximised output will be achieved through the effort of minimising input - improving and maintaining equipment at optimum levels to reduce its life cycle cost. Cost-effectiveness is a result of an organisation’s ability to eliminate the causes of the ‘six big losses’ that reduce equipment effectiveness:
Reduced yield (from start up to start-up to stable production).
Idling and minor stoppages.
Set-up and adjustment.
The JIPM also states that “Both operations and maintenance departments should accept the responsibility of keeping equipment in good condition. To eliminate the waste and losses hidden in a typical factory environment, we must acknowledge the central role of workers in managing the production process. No matter how thoroughly plants are automated or how many robots are installed, people are ultimately responsible for equipment operation and maintenance. Every aspect of a machines performance, whether good or bad, can be traced back to a human act or omission. Therefore, no matter how advanced the technology is, people play a key role in maintaining the optimum performance of the equipment.”
Whilst in the early stages, the workforce involvement will usually be limited to membership of multi layer teams, in the longer term, usually in around two to three years, the operator involvement will have developed into fully autonomous self managing maintenance group activities.
Typically, in the early stages, a pioneer team of managers, technical specialists including maintenance department personnel and operators work on one problem production line. Using the project by project disciplines the team select specific problems from amongst the so called ‘Six Big Losses’ that they believe can be solved quickly and easily but which produce tangible and measurable improvements.
At this stage, the programme is then given a high profile and extended to include every one in the plant. The initial teams of workers will be trained in the problem solving tools and taught how to select process related problems as projects. Managers and specialists will act as consultants to the newly formed teams and guide them in the best use of problem solving methods.
5S/5C CANDO system
At this point the workers will be encouraged to carry out simple plant cleaning activities using the 5S housekeeping concept.
Whilst the exact translation of each of the 5 S’s does not transfer directly into a convenient set of words ‘S’ words in English, the following can be safely regarded as being very near equivalents. There are also other variants such as the 5Cs and CANDO which is another mnemonic popular in the USA. Essentially they are all the same.
SEIRI - Systemising and Standardisation.
Utilisation of equipment:
Classification, tool selection, material and suitable equipment for each task or activity, information selection and recording of that required to perform the task.
SEITON - Sorting.
Finding the right place to save objects and general organisation of the place of work.
SEISOU - Sweeping.
Keeping the work area clean.
Retain only the information and items needed to work on the specific tasks.
SEIKETSU - Sanitising.
Creating good conditions of hygiene, checking, illumination, atmospheric pollution, sound and temperature etc.
Keeping visible records easy evaluation and comprehension.
SHITSUKE - Self Discipline.
Developing the habit of looking at procedures and rules. Self control and self direction.
The cleaning activities encouraged at the commencement of a TPM programme can be likened to steam cleaning the engine of an automobile. When dirty, it is impossible to tell if there are any screws missing or loose, or if there are any oil leaks. However, after cleaning, missing screws can be easily identified, and after a few days, any possible oil leaks can be seen indicating worn oil seals or potential bearing failures.
At the same time, the operator can begin to understand better how his or her machine actually works.
Even at this early stage it is not unusual to achieve a reduction of stoppages in the order of some 50%. However, it takes from two to three years to achieve the really impressive benefits.
In parallel with this, the team leaders and supervisors will be trained in simple plant maintenance and the relevant technology. This will free up the time of the maintenance engineers to do more complex work and to develop their own skills. Later, this training will be extended to the operators themselves.
As the teams begin to mature, they will soon be able to look after the machines themselves. As they become more confident there is a marked change in attitude and a will to take wider responsibility for the performance of their operations.
These should be selected using the following criteria.
1. Those which have a positive impact on the work environment, for example Housekeeping.
2. Relatively simple but with a tangible payback.
3. If possible, choose projects in which the advice of members of the workforce can be of value.
4. Make sure that the projects selected can predictably be completed and the results implemented in around three months from the beginning or less. People will loose interest if the projects go on for too long.
5. Be very careful not to take on anything too challenging in the early days. A failure at this stage would be a major upset in the implementation process.
6. Projects selected should be either measurable or countable and stated in a negative form. For example, loss of yield from process X would be measurable and stated in its negative form. ‘Too many breakdowns on Line X is countable and also in the negative form. The reason for the use of the negative is that the next question will be ‘what causes the problem? Usually there will be many theories offered by the team members.
7. Before attempting to find the possible causes, it is also important to record the current state of the problem. Collect and organise date to show its severity, use graphical techniques such as the Pareto diagram in order to dramatise the situation. Frequently, with housekeeping related or in cases where there may be severe wear or catastrophic breakdown, photographs or video can be ideal methods for recording the current state. They will also be useful historical evidence years later. At Short Bros. Ltd, the Belfast based Aerospace Company, they have an exhibition showing the internal condition of all of the departments before they began the improvement process and then subsequently, the various stages of progress over the following years. It makes an impressive display.
8. When the possible causes have been identified, before going on to the next stage, it would be as well to seek the opinions of the relevant members of the workforce and anyone else who may have valid opinions. In one such situation in the early days at Short Bros. Ltd, a worker was asked why he thought leakage’s occurred around the small rivets which joined adjacent parts of an aircraft wing. He explained that he believed the shape of the tool fixture was incorrect and suggested an improvement. His idea implemented and proved successful. One of the more cynical of the managers asked why did you not tell us before? The response was “you never asked”! The more the opinions of the workforce are solicited, the more enthusiastic they will become and the easier it will be to gain volunteers for Autonomous workgroup activities when these first management level projects have been completed.
9. Typical problems and possible causes include:
Loss Possible Cause
Breakdown losses Checking and Cleaning
Equipment failure losses ditto
Set-up losses Waiting Instructions
Jig and Tool losses ditto
Start-up losses Waiting materials
Other downtime losses Waiting personnel
Minor stoppage and idling losses ditto
Reduced speed losses Quality instructions,
Measurement & Calibration
Defect & rework losses ditto
Waiting Instructions Management planning
Waiting materials ditto
Equipment downtime Management organisation
Equipment performance ditto
Methods & procedures ditto
Skills and loss of morale Management environment
Line organisation losses Management training
Measurement and setting losses Resource Planning
10. Finding the true causes from amongst the many theoretical causes requires the collection and analysis of data. Usually the data for the type of projects selected for TPM activities is easily recovered and does not normally demand the use of sophisticated techniques such as Designed Experiments etc.
11. In almost all cases the data will provide convincing evidence as to the true causes. When these have been determined, the team will then turn their attention to the selection of appropriate remedies. Wherever possible, the most popular remedies will be from amongst those which are irreversible, in other words, which are foolproof. If non fool proofable solutions are to be implemented they will need to be included in periodic audits to ensure that the improvement is continuing to be applied.
Following the completion of these early projects, a full awareness programme can be implemented. The initial projects should be used to demonstrate management commitment and the methodology used.
Only start as many teams as can be safely supported through their early learning experience.
As the teams develop their capabilities, it then becomes possible to increase both the number of teams and their range of problem solving skills. They can also be encouraged to tackle more difficult problems and to introduce a degree of self management. This can best be achieved by encouraging the teams to set themselves annual targets for process performance improvements. This becomes possible if the organisation practices Hoshin Kanri Planning and policy deployment. Initially the teams, should be taught to collect data to determine the overall operating efficiency of their unit of operations. This information can then be used to set targets and enable the selection of appropriate projects.
In all organisations where success is known to have been achieved, considerable efforts have been made to give recognition to successful teams and to enable all of them to display their work.
Typically, TPM boards are erected at convenient locations near to the work areas to enable the teams to post their charts and other examples of their work. This is partly for recognition purposes but also to encourage others to offer suggestions to the teams.
Displays of completed projects are posted including photographs of the teams and any awards that they may have received. All of this activity is in order to demonstrate commitment and to ensure that the TPM concept has the highest possible profile in order to maintain the highest possible level of consciousness as to the importance attached to these activities.
Examples of Success. (Internet source)
Nissan, Tochigi Plant. Results after 3 years.
Manufacturing cars, 7000 employees.
No of cars passing QC first time, no rework increased by 70%.
No of breakdowns reduced by 80%
Overall equipment efficiency increased by 30%.
Comment from Company - “we cannot management our Plant without TPM”
Nippon Lever, Utsunomiya Plant.
Manufacturing Lux Soap, Household Cleaners.
Results after 2 years
Reduction in operating costs - £2.8 Million
Cost of introducing TPM £90000!
- Domestic filling line - up from 76% to 95%.
- High speed soap line - up from 54% to 85%.
Comment from Company “the ideal status of a machine is to have no defects, no breakdowns. You may think that’s impossible. But when you see the Nippon Lever plant, you realise it is possible”.
David Hutchins is a Board member of the Quality Methods Association and obtained his Masters Degree at the Department of Engineering Production at Birmingham University. He specialises in the implementation of Business performance improvement concepts in a wide range of countries and cultures. He can be contacted through the ‘CONTACT US’ feature at the top right hand corner of this web site.