School of Technology and Design, TD
Investigation of the ways to improve the performance of a plant
Undersökning av metoder för förbättring av anläggningskapacitet
Växjö June 2007
Report ID: TD 039/2007 Muhammad Shahid Tufail Hamid Mehovic Department of Mechanical Engineering
Organisation/ Organization Författare/Author(s) VÄXJÖ UNIVERSITET
Institutionen för teknik och design Muhammad Shahid Tufail Växjö University Hamid Mehovic
School of Technology and Design
Dokumenttyp/Type of document Handledare/tutor Examinator/examiner Examensarbete/ Diplomawork Om Prakash Basim Al-Najjar
Titel och undertitel/Title and subtitle
Investigation of the ways to improve the performance of a plant Undersökning av metoder för förbättring av anläggningskapacitet
Sammanfattning (på svenska)
Nuförtiden är många företag intresserade av att förbättra sina produktionssystem. Det har blivit viktigt i den globala och konkurrensutsatta marknaden för överlevnad. Företagen undersöker sina produktionssystem ur olika aspekter för att nå konkurrensfördelar. Men viktigast är att finna problemet i produktionssystemet för att möjliggöra förbättringar.
I denna uppsats studeras en del av produktionssystemet på ett företag för att finna problem i produktionssystemet för att kunna göra förbättringarna, och för att kunna rekommendera lösningar som leder till att företaget når sina strategiska mål. För att uppnå detta har beräkningar av anläggningseffektiviteten använts för att kartlägga nuläget. Dessa beräkningar av O.E.E. på olika arbetsstationer ger en klar bild av problemen.
Det beräknar tillgängligheten av produktionssystemet som visar på underhållssystemets effektivitet.
Kvalitetsutbytesberäkningarna visar på tillståndet hos maskiner och arbetares kompetens, medan anläggningseffektiviteten i arbetsstationerna visar på maskinutnyttjandet. Resultatet av uppsatsen efter beräkningarna av O.E.E. är att det finns problem med utnyttjandet av maskinerna. Ofta står maskinerna stilla eller väntar på underhåll om de går sönder.
Nyckelord: Underhåll, O.E.E., Konkurrensfördelar, arbetskraftsledning.
Abstract (in English)
Nowadays many companies are interested to improve their production system. It has become important in globalize and competitive market for the survival. The companies are looking to their production systems in the different direction to get the competitive advantages. But the most important is to find out the problem of the production system to make improvements.
In this thesis, a part of the production system of a company is studied to find the problems of the production system to make the improvements and to recommend some points to the company for the achievements of its goals. For this purpose, the overall equipment effectiveness calculations have been used to see the current situation of the production system of the company. These calculations of the O.E.E. of the different production work stations make the clear picture of the problems. It calculates the availability of the production system which shows that maintenance system’s effectiveness. The quality rate calculations of the work stations show the conditions of the machines and the worker’s skill and the calculations of the performance efficiency of the work stations show the utilization of the machines. The result of this thesis after all the calculations of O.E.E. is that there is a problem in the utilization of the machines. Most of the time the machines remain idle or wait for the maintenance if it fails.
Key Words: Maintenance, O.E.E., Competitive advantages, manpower management.
Utgivningsår/Year of issue Språk/Language Antal sidor/Number of pages 2007 English 52
Internet/WWW http://www.vxu.se/td
Acknowledgement
A special thanks to the production chief Lars Kinnby for his co-operation and make it possible for us to complete our degree thesis. The authors also thank to the production team of the company which make possible to get the required information and data. We would like to specially thank the machine operators for their help to make the calculations.
The authors would like to thank the supervisor associate professor Om Prakash for his help to complete our thesis and the rest of the personnel at the department of the tero technology at Växjö University for the help and support. Authors would like to specially thank for Mirka Kans and Anders Ingwald for their support through out the course.
Authors would like to thank to the class fellows and friends for the discussions on the different topics which are helpful to clear the ideas of the programme.
Muhammad Shahid Tufail Hamid Mehovic
Table of contents
1. Introduction ………. 1
1.1 Background………..1
1.2 Problem discussion……….. 2
1.3 Presentation of problem………. 2
1.4 Problem formulation………3
1.5 Purpose……….. 3
1.6 Relevance………... 3
1.7 Limitations………. 3
1.8 Timeframe………. 4 2. Research methodology………
2.1 Positivism and Hermeneutics………
2.2 Qualitative and Quantitative methods……….
2.3 Data collection technique………..
2.4 Induction and deduction………..
2.5 Research strategies ………
2.5.1 Experiment………
2.5.2 Survey………
2.5.3 Interview………
2.5.4 Observation………
2.5.5 Case study……….
2.6 Validity and Reliability ………
2.7 Research method selection………
3. Theory……….
3.1 Maintenance………
3.2 Maintenance Objectives………
3.3 Maintenance management……….
3.4 Maintenance strategies………..
3.4.1 Preventive maintenance……….
3.4.2 Predictive maintenance……….
3.4.3 Breakdown maintenance………
3.4.4 Design out maintenance……….
3.5 Maintenance techniques………
3.6 Maintenance and production relationship……….
3.7 Competitive advantages through efficient maintenance………
3.8 Introduction and history of Total productive maintenance………
3.9 Definition of TPM………..
3.9.1 Down time losses………
3.9.2 Speed losses………
3.9.3 Defect or Quality losses………..
3.10 Overall equipment effectiveness (OEE)……….
4. Empirical findings………..
4.1 Henjo Plåtteknik AB Ljungby………..
4.2 Introduction ………..
4.3Organizational plan of the company……….
4.4 Company working style and different processes………..
4.5 Products of Henjo Plåtteknik AB………..
4.6 Description of the production section activities ………
4.7 Production process………
1 1 2 2 3 3 3 3 4 5 5 5 6 6 6 6 7 7 7 7 7 8 9 9 9 10 10 10 10 11 11 12 12 13 14 14 14 15 15 16 18 18 18 19 19 20 21 23
4.8. Quality ………..
4.9. Maintenance………..
4.10. Goals of the company………..
5. Analysis………
5.1. O.E.E. calculation of Laser cutting work station………
5.2. O.E.E. calculation of Bending work station………
5.3. O.E.E. calculation of Punching work station………
5.4. O.E.E. calculation of Robot Welding work station………
5.5. Production line 1 & 2……….
5.5.1 O.E.E. calculation of Line 1 ……….
5.5.2 O.E.E. calculation of Line 2………..
6 Results and Discussion………..
7 Conclusions………..
8 Recommendations……….
References………
APPENDIX #1……….
APPENDIX #2……….
25 25 26 27 27 29 30 32 33 33 33 39 42 43 44 46 46
1. Introduction
In this chapter the background and problem formulation with discussion for the case study will be presented. Further on the limitations and purpose of the case study will be stated.
1.1. Background
With the start of the new century, the competition and pressure to perform competitively have increased on the companies. This new age will be challenge for the companies to provide new, exciting, innovative and cost effective products in the market. (Bean R. & Radford R., 2000). Now the business has become globalize and competitive. To survive, a company has to offer best prices to its customers with high quality, service and operate with lowest cost. It is only possible for a company if all of its departments are well managed (Andersson D., 2005).
In today’s competitive environment, companies want to get the benefits of the different techniques which are being used in the product processes. They have implemented total quality management (TQM), just in time (JIT) manufacturing and total employee involvement (TEI). Now many companies have shifted their focus to optimization of their assets. One of the main parts of the company which has a strong influence on the assets is the maintenance department or the employees responsible for maintenance (Wireman T.1998).the different concepts to meet the requirements of the manufacturing plant are not successful without the support of the quality and maintenance strategy. For example, JIT manufacturing concept demands for an effective and efficient maintenance which can ensure smooth flow of production and ideally, cent percent quality cost effectively. The maintenance adds to customer value in terms of profit, quality, time and service. Therefore, the maintenance function has become important for a manufacturing company’s ability to maintain its competitiveness. Without well maintained equipment; it will not be advantage in the market that requires low cost products at a high quality to be delivered quickly.
(Alsyouf I.2004)
There is no doubt that the maintenance has a vital role in the companies.
Now a days most of the companies are giving attention to this important function which is considered as the necessary evil for the companies, i.e. an expense to the companies and a non value addition function. The companies can not survive for long time without considering the maintenance as an important function because they will be put out of the business by the companies that are considering the maintenance as a competitive weapon. Now the companies are looking it as a way to reduce the cost of producing their products. There is no doubt that it is another main area of cost. The cost reduction of this area is not meaning the decrease in service or the quality of the service. It means that the good control of the maintenance organization. The companies have used different organisational structures, change reporting structures, upsizing, downsizing, contracting out, and empowered teams for the purpose to control the maintenance. It has been realised that a typical developed system consists not only of mechanical components but also other elements such as electronic, hydraulic, electromechanical elements, software and human beings are involved in the system. This means that the disturbance in the production process may occur due to different factors such as the failures of the important components of equipments, the quality of the purchase materials and spare parts, design, manufacturing process
control, management systems and human error. (Tajiri M., Gotoh F.,1992 ; Wireman T.1998)
The effectiveness of the manufacturing companies remains at the certain level. This is due to improper maintenance and unavailability of the equipments. In most of the manufacturing plants, the equipment is susceptible to failure through breakdown maintenance, deterioration in performance through age and use and obsolescence due to improvements in the technology. Maintenance has a strong effect on above mentioned areas. Also it can reduce the cost of the manufacturing process, improve the quality and capability of the production process. These internal improvements of the manufacturing system can be more profitable, improve the environment and safety. The unforeseen stops, speed losses, and quality defects in the operating equipments reduce the working potential of the manufacturing plant from twenty to seventy percent. These factors become the reason for the production losses and other indirect hidden costs. Ultimately, it affects the overall performance of the company. The interruptions are not only due to the maintenance but bad maintenance can be important part of the causes of disturbances (Jonsson P., 1999). The importance of maintenance has been increased than before, due to its role in maintaining and improving availability, performance efficiency, and quality products, on time deliveries, the environment, safety requirements and overall plant productivity at a high level.
1.2. Problem discussion
Nowadays many companies are interested to improve their maintenance system. Because, they have come to know that this is the system through which companies can reduce the cost of their products and can develop a reliable production process. A well designed maintenance structure can be helpful for the companies to get the competitive advantages. But majority of companies are not able to manage a maintenance system. The two main reasons for that are the lack of proper measurement and the lack of control systems for maintenance. (Wireman T., 1998) The main goal of the maintenance is to reduce the failures of the industrial plant, machinery and equipments. This goal can be achieved by using different maintenance approaches such as corrective maintenance and preventive maintenance e.t.c. A good maintenance approach and schedule can not be 100 percent effective at all the time. Unforeseen equipment breakdowns and requests reduce the efficiency of the plan. Even now a good maintenance schedule can get 70 to 90 percent efficiency (Wireman T., 1994).The detection and implementation of a suitable maintenance approach makes the companies able to prevent the premature maintenance cost, maintain the stable manufacturing capabilities and control the deterioration of the system. In other words, the company can improve its performance if it implements a suitable maintenance approach for eliminating the causes of production disturbances.
1.3 Presentation of problem
The idea with this project is to see the current situation of the company.
Is the company using its manufacturing equipments in a proper way to get the competitive advantages? If not, then find out the main reason for that. Which kind of
problem is there i.e. availability, quality or performance efficiency? And what is the influence of these problems to achieve the goals of the company. The company can not compete in the competitive market unless it uses it resource and capabilities to the maximum level. The company must have to work to get rid of the problems to get the competitive advantages with respect to cost, service, quality and on time delivery.
These issues do not allow the company to achieve its set goals.
1.4 Problem formulation
• To investigate the current situation of the production of the case company.
• To pick up the weakening in the production system those do not allow the company to achieve its full capacity and meet the set goals.
• To suggest the ways to improve the situation.
1.5 Purpose
The purpose of this case study is to take a systematic and scientific way to analyse the current situation and suggest the ways to improve it to achieve the set goals.
1.6 Relevance
Now a days companies are realising the importance of the maintenance in the competitive environment. They are looking to get the benefits of the maintenance.
They want to make a reliable manufacturing system with minimum failures and to improve the production capacity of their plants. This is the main focus of the maintenance. The overall equipment effectiveness of the production process is the way of understanding the current situation and it gives the direction to put forward an initiative to improve the situation. Because it makes the problems clear and the effect of these problems on the company’s business can be seen easily. The value of this can be increased with the help of the full participation of the employees from management to workers and a maintenance system in the company. This study future will show the way the company’s profitability can be improved and the set goals can be meet.
1.7 Limitations
The limitations of this case study are to study one manufacturing company and two production processes because these are the main production lines of the case company and of the time limitations. We are not able to study all the machines individually in selected work stations. We use the average value of all the machines at a work station. All the calculations are based on one year’s data (2006).
1.8 Timeframe
The time frame for the project is as follows.
Introduction
Methodology
Theory
Analysis
Conclusions
Collecting data
Week 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
2 Research methodology
Many definitions of Research have been given, as a systematic method of gaining new knowledge or a way to answer the questions. (Gliner, Jeffrey A., Morgan, George A., 2000)
Research methodology is considered as a supporting subject. It is used to develop a variety of research paradigms. These paradigms are varying in their contents and substance but their broader approach to inquiry is the same. ’Although the basic logic of scientific methodology is the same in all fields, its specific techniques and approaches will vary, depending on the subject matter’. There are two basic steps in the research process. The first step is to decide the goal or research questions. The second step is to find out the way to get the answers of the questions. The path to get the answers of the questions is composed of the research methodology. The selection of suitable methods, procedures and models are played an important role in each operational step of the research process to get the objectives of the research. (Kumar R., 2005).
2.1 Positivism and Hermeneutics
Positivism has the roots in empirical scientific tradition. The positivist considers the complete knowledge while the hermeneutic is more understandable for the practical mind. Positivism has the belief that human being can get the knowledge in only two ways i.e. what we can sense (empirical knowledge) and what we can workout with our logical aptitude. Any one can find the fact with the help of empirical knowledge.
According to the positivism the logical truths have nothing to do with observations from the reality, it has only to do with our intelligence and our way to use the language. A person should be critical to study a statement or an observation and the study should be based on the facts i.e. they can be used with out any hesitation. To be capable to make the result from these facts, a logical analysis must be preferred. Positivistic community have normally a critical view on the world around themselves. (Gliner, Jeffrey A., Morgan, George A., 2000)
Hermeneutic is a science of interpretation. It uses the interpretation of pre- understanding type and learning of interpretation. Hermeneutic is about interpretation of meanings. It can be used to interpret the context in words, symbols and experience e.t.c.
the interpretation explain the sense and relation which lie at the back of everything and can appear or which can be observed in the text, conversation or an act. It is must for the person that makes the interpretation to choose a starting point for the questions because the material will be based on it. The starting point consists of the basic vision, assessments and interpretation. The hermeneutic research is subjective as compare to the positivistic research. The hermeneutic researcher uses own assessments when doing the research. The pre-understanding is represented by the researchers experience and knowledge. Hermeneutic can also be observed as a common knowledge about communication and understanding. (Järvinen.P., 2001)
2.2 Qualitative and Quantitative methods
The two main ways are used in the research called as quantitative or qualitative, which will be used is based on the available information. The qualitative analysis is theoretical and less nearer to the raw data as compare to the quantitative analysis. Word or sentences are used in the qualitative method but mathematical figures
are used in quantitative method. Like as the terms “less than” or “bigger than” can be used in qualitative method but the exact figures are used in the case of quantitative method.
In the quantitative method, the researcher gathers the data and carefully examines it. The attempt is made to find the relations between different sets of facts. The researchers calculate and use the scientific technique to get the result. In the qualitative method, the researcher is more interested in the knowledge of people. (Ingwald A., 2004)
2.3 Data collection technique
There are two types of data which are collected for the research purpose, primary data and secondary data. Primary data mean new data. While secondary data mean the data which already exist. The methods used to collect the new data are observations, interviews and experiments. There are some problems to the use of the data.
One problem is the compatibility and the other trustworthiness. (Ingwald A., 2004)
2.4 Induction and Deduction
Induction and deduction are two different ways of making the decisions.
Empirical facts are the base for the conclusions in Induction approach. It is vital to understand that inductive conclusion can not be hundred percent accurate. This is only because of the empirical material is the base of the conclusion. It means that there is a probability of different results from different persons. (Järvinen P., 2001)
Logic is used to make the conclusions in the deduction approach. The conclusions must be reflected as valid, logically. On the opposite this conclusion need not be true according to the reality. The conclusion can be ruled out due to the experience in the induction and this is the main dissimilarity in the induction and deduction way of making conclusion.
(Järvinen P., 2001)
2.5 Research strategies
There are different research methods which can be useful when performing a project. (Alsyouf I., 2001)
2.5.1 Experiment
The experiment method is divided into laboratory experiment, quasi experiment and field experiment researches.
The laboratory experiment is performed in the same environment conditions for each object that takes part in the research. The basic parameters and variables are control in this type of research.
The quasi experiment research is almost the same as laboratory research.
But the difference is that the research is done in the reality with out control on the variables.
In the field experiment research, the researcher has good chance to control the variables as compare to the quasi experiment research. This method of research is also done in the reality. (Dyer C., 1995)
2.5.2 Survey
The survey research uses the many basic research methods to get the data from participants in their natural environments. The basic way to get information in this method is survey. This survey is consisting of a set of one or more questions that ask the people about different issues. Opposite to the experiment research, the survey researcher does not control the variables but does inflict some constraints on the participants by using the survey tool. It is used to test the relationship between different variables.
(Graziano A. and Raulin M., 2000)
2.5.3 Interview
Researcher and interviewed persons are the requirement of this method. The researcher must be talented to place one self in the current situation. The researcher must take the record on the problem area that is discussed and the interviewed person must be capable to argument for the researcher’s opinion. (Järvinen P., 2001)
2.5.4 Observations
This method is divided into two parts. These are named as participant and non-participant observations. In the participant observation research method, the participators are alert that they are under study. Non-participant observation research method is opposite to the open research method. The participators do not have an idea that they are under observation. (Järvinen P., 2001)
2.5.5 Case study
It consists of different kind of researches. It can be based on combinations of quantitative and qualitative proof .it does not require always consisting of direct, detailed observations as a proof. The researcher chooses the most suitable method for the specific case i.e. interview or survey e.t.c. (Sekaran U., 2000). The main advantage of the case study is that the researcher can focus on one exact thing or fact and then try to discover the affect of different factors on it.
2.6 Validity and Reliability
Validity views the degree to which an observation measures what it claims to measure. Validity is a theory, model, or concept which describes the reality exactly.
Internal validity and external validity are the main types of the validity. The external validity is about the theoretical part of the research. While the internal validity deals with the project. It also deals with the connection between the theoretical part and the empirical parts of the research. If the different portions of the project are not able to get the required validity, it will also lead to unachieved validity for the whole project.
(Järvinen P., 2001)
Reliability views the degree to which observations by different researchers studying the fact with same reason will get nearly the same results. (Gummeson E., 1988) There are three kinds of reliability: quixotic, synchronic and diachronic. The quixotic reliability is the extent to which a specific technique of observation generates an even measurement. The Synchronic reliability is the extent to which observations within the same time interval are similar. The Diachronic reliability is the extent to which a specific technique of observation generates the same measurements when exposed to specific observable fact at different points in time. (Järvinen P., 2001)
2.7 Research Method Selection
The research strategy that is going to use in project is the case study. The
case study consists of the interviews and the observations. That is the reason that the both qualitative and quantitative methods will be use in the project. The qualitative method is
used when interviews are conducted and the quantitative method is used when the data is collected and analysed. The writer will collect data by themselves and will receive from the company employees. In other words, the primary and secondary data will be used.
The deduction approach will be used in this case study project. This approach is helpful when comparing the collected data with the theory. The purpose of the data collection will be explained to the persons involved in the information so that a valid and reliable data can be used in the project.
3. Theory
Nowadays the costumer’s demand is increasing. They want quality products at low cost with high service level. This attitude of the market compels the companies to make research on their production systems. Therefore every company wants to utilise their machines and equipments at the highest possible extent. This is possible only if they have a good maintenance system which makes the companies manufacturing equipments a best possible working condition. In this chapter, the theory about the maintenance concept will be presented.
3.1 Maintenance:
Maintenance is a multidisciplinary area and it is hard to explain its different function. It has been defined in Macmillan’s dictionary of production management and technology as “The care and repair of equipment. There are several approaches to maintenance in manufacturing but in each case, a more strategic view is generally taken today than previously. Many of new techniques (e.g. JUST IN TIME) depend upon totally reliable equipment, and the term ‘TOTAL PLANNED MAINTENANCE’ has coined to cover this …maintenance may be PLANNED or PREVENTIVE, but some production plant is best maintained on a REACTIVE basis-having the ability to respond very quickly to plant failure.” Maintenance management in the European standard is defined as:” All activities of the management that determine the maintenance strategy, objectives and responsibilities and implement them by means such as maintenance planning, maintenance control and supervision, improvement of methods in the organisation including economical aspects”.
The above definitions stress on the complicated role of maintenance. Various maintenance methods concentrate on different aspects of maintenance. The strategic and integrated maintenance is the demand for the Lean organisations. But reactive maintenance policies are reliable for some other environments. The maintenance area covers equipment and technical systems as well as organisational, human and economical aspects (Josson P., 1999)
3.2 Maintenance Objectives
Maintenance is vital for the process industry .this fact was recognised and raised with the development of the Japanese’s industry. The strengthening, year by year, of maintenance management in the process industry occurred for different reasons. In the industry, production relies heavily on the plant itself, so that the most of the factors like productivity, quality, safety, pollution, and production costs depend on the condition of the plant. Also most of the industry production is of the continuous, integrated type, so plant and equipment problems generate enormous financial losses.
The primary objectives of maintenance are:
• To extend equipment life.
• To keep the plant and equipment in the optimal condition for production or service and secure maximum return on the investment.
• To constantly maintain the ability to cope with emergencies.
• To assure safety.
(Suzuki T., 1992)
3.3 Maintenance management:
The aim of the maintenance management was kept maintenance program operating efficiently toward the objectives of the maintenance.
Once the equipment is assembled and fitted, test operations are completed and the equipment is handed over to the company and started up. At this point, the maintenance management step begins, covering the life cycle of the equipment.
Maintenance management deals with the maintenance of equipment in various technical ways by using the different maintenance approaches. (Suzuki T., 1992)
3.4 Maintenance strategies:
In maintenance different strategies are used. But it depends on the failure modes and their behaviour in time. The different maintenance strategies to meet the failures are as follow.
• Preventive maintenance
• Predictive maintenance
• Breakdown maintenance
• Bad actor management
3.4.1 Preventive maintenance:
The term “Preventive maintenance” means “Periodic maintenance” and is known as all over the world. Preventive maintenance in this sense is a periodic or scheduled activity, which has as its objective the direct prevention of failure modes or defects. In its simplest form this activity consists of the periodic lubrication, coating, or cleaning of the machinery components to increase the useful life duration.
Periodic preventive maintenance is very useful in case of some failure modes but it is not effective for all kind of failure modes. Moreover, quite often deterioration cannot be completely abolished even in those failure modes that do respond to preventive maintenance. For example, by periodically renewing the lube oil in a pump bearing, it does not mean that the deterioration of the bearings will be finished by this activity.
Because there are so many other factors which are involved in the deterioration. The quality of the oil itself may be the reason of the deterioration. So the wear of the bearings can be reduced but can not be finished. (Bloch Heinz P., Geitner Fred K., 1999)
3.4.2 Predictive maintenance:
Predictive maintenance is periodic inspection activity. If any defect is deducted during inspection, it may be the replacement or overhauling of the machine parts, this maintenance activity performs its role to remove the problem of the machine.
These actions of predictive maintenance do not directly reduce the deterioration rate but indirectly control the chance and cost of the accidents, breakdowns, malfunctions, and general trouble. This maintenance activity is referred as the predictive maintenance.
The preventive maintenance looks mainly the time-dependent failure modes and predictive maintenance deals with the randomly and suddenly happening failure modes as far as possible by searching for them and by effecting timely repairs. With the implementation of this maintenance technique, the expectations to prevent the failures are
not high and are not possible to control the failures completely. But the influence on the consequences of the unexpectedly occurring defects can be reduced with this technique.
Predictive maintenance strategy point out a continuous search for defects is required and in other words a continuous monitoring of the machinery condition and performance is necessary with the continuous feedback. This type of maintenance highly depends on the vigilant operators and the maintenance people as well as the type of the plant under consideration. In reality, the majority of the activities in the predictive maintenance are some how periodic and depend on the observer’s sense of seeing, hearing, feeling and smell. (Bloch Heinz P., Geitner Fred K., 1999)
3.4.3 Breakdown maintenance:
Some people are optimistic about the possibilities of machinery preventive maintenance. This ability of some people can not be the parameter for the breakdown maintenance. But there are several limitations to machinery preventive maintenance concepts.
• The limitations set by random failure events. But random machinery failures are not happened after equal time intervals and form this reason, predictive maintenance is preferred in industry over breakdown maintenance. Continues inspections are the only solution of this kind of problems.
• The life dispersion of the machinery components. The time-dependent failures are not predictable at all yet. They are not occurring after the same time intervals.
There can be different reasons for that. For example, the life dispersion of the mechanical gear couplings on process compressors. There is no doubt that they are components going to wear with time. If it can be assume that mean time between failures or the mean time between reaching of defect is 7.5 years. But it can be happened that the failure become after 3 years or after 15 years. This can be happened due to the misalignment, lubrication losses e.t.c.
• The third limitation of preventive maintenance in machinery is that in order to inspect we have to shut down and open up. It is a risky procedure.
We conclude from this that certain breakdown maintenance of our machinery will always be necessary.
This maintenance activity brings back the machinery equipment to service after failure modes developed that were:
Preventable but not prevented.
Predictable but not predicted.
Predicted but not acted open.
Not preventable or predictable.
(Bloch Heinz P., Geitner Fred K., 1999)
3.4.4 Design out maintenance
This type of maintenance is different from the other types of maintenance.
The aim of this maintenance type is also to minimise the failures with to minimisations of the reasons of the maintenance. Obviously, this is an engineering problem but its responsibility is also on the maintenance department. This maintenance is considered for the items of high maintenance cost which is may be due to poor maintenance, poor design or operation outside the design specifications. Some times, the design out maintenance
has the purpose to work on an item which does not require maintenance. Therefore, this kind of policy can be apply effectively if an information system exists which gives the service in the identification of such items. The decision is made in between to bear the cost of the redesign of the item or the cost of the repeated maintenance. (Kelly A., 1984)
3.5 Maintenance techniques:
Maintenance methods and diagnostic techniques are different according to the technical category of the equipment dealt with, whether it consist of fixed vessels such as towers, tanks, heat exchanger, or rotating machines such as compressors, motors, pumps, speed reducers or furnaces, instrumentation, piping and so on. It depends on the management of each company to which method they use in maintenance.
(Suzuki T., 1992)
3.6 Maintenance and Production relationship
Maintenance has an important place in any organisation and it is to be positioned as a sub process or integrated part of the overall production process. The relation between maintenance and production can be shown in the figure 3.1 below. The primary inputs to production process are material, energy and manpower .These primary inputs are then transformed into primary output i.e. the final product. This transformation of primary inputs to primary output leads to a secondary production output that is the maintenance demand. Maintenance affects the potential production capacity of the plant and is necessary to keep the potential production capacity of the plant on the maximum level. In other words, it is the secondary input of the production process.
(Josson P., 1999).
Production process
Primary input Primary output
Secondary input
Secondary output
Maintenance
Figure 3.1 Production-maintenance processes
3.7 Competitive advantages through efficient maintenance
The efficient maintenance influences the productivity, competitiveness and profitability of the manufacturing process because it has the direct impact on the quality, efficiency and effectiveness of the production process. In an organisation, the operations function has the responsibility to produce the goods or provide the service to the costumers of the company. In any manufacturing company, the company consists of many departments like engineering, planning, purchasing, manufacturing, quality, maintenance, despatch, e.t.c. but the operations function has relatively high budget as compared to the all other departments and consists of the largest part of the company’s budget. The main reason for that is to manage the manufacturing activities effectively, efficiently, and with high quality. The most cost effective maintenance approach has the influence on the performance of the business and on the performance of the maintenance itself. The maintenance has directly influence on the quality of the operations. On there hand, the operation quality and maintenance efficiency has the influence on the effectiveness and efficiency of the operations processes. There is no doubt that the result of a good quality, efficiency, and effectiveness of the operations processes comes in the form of productivity advantages i.e. lower cost, and value advantages(in terms of good image and reputation in the market).This leads a company towards the competitive advantages (Figure 3.2).(Alsyouf I., 2001)
3.8 Introducti
Competitive advantages
Productivity advantages
Value advantages Profitability
Operation effectiveness
Operations quality
Operations efficiency
Efficient maintenance
Figure 3.2 How does the maintenance influence the company’s competitive advantages?
3.8 Introduction and history of Total productive maintenance
TPM methodology was started in Japan in 1971.The concept of this methodology was come from USA. (Nakajima S., 1988).In those days the Japanese’s industry was in critical economic situation due to the oil crises and was searching the effective measures to survive in the worldwide market. They took the basic idea of the productive maintenance (PM) from united state and modified it by the Japan institute of plant maintenance to TPM system. This system was develop step by step in small group activities (Tajiri M.,Gotoh F.,1992).Therefore, TPM is an American style of productive maintenance which has been modified and improved to fit it in the Japanese industrial environment. Now it is normal in Japanese industry and becoming popular in other western countries (Nakajima S., 1988).
The development of TPM is usually divided into four main development stages and these are as:
• Breakdown maintenance
• Preventive maintenance
• Productive maintenance
• Total productive maintenance(TPM) (Nakajima S., 1988).
3.9 Definition of TPM
Total productive maintenance is also known as the productive maintenance with everyone’s participation. It can be defined as including the following goals:
1. The TPM is concentrate to maximize the overall equipment effectiveness.
2. The TPM has the aim to establish a comprehensive preventive maintenance system for the whole life span of the equipment.
3. The TPM involve all departments which make planes, use and maintain the equipment.
4. TPM makes the participation of all employees from top management to workers.
5. TPM promotes the preventive maintenance through motivation management i.e through autonomous small group activities.
(Suzuki T., 1992)
TPM has the main goal to maximize the overall equipment effectiveness. So to achieve its goal, TPM try to reduce the six big losses that are the main problems to get the high equipment effectiveness. The link of the losses and the effectiveness in TPM is defined in terms of both the quality of the product and the equipment availability. On the base of the detail study of the factors involve in the reduction of the equipment effectiveness are divided into six main types.
3.9.1 Down time losses
• Breakdown losses
These kinds of losses are due to the defects of the equipment which need any kind of repair or maintenance. These kinds of losses consist of downtime along with the
labour and the spare parts required fixing the problem. The amount of these losses is calculated in the form of downtime.
• Setup and adjustment losses
These losses are due to the changes in the operating conditions, like the start of the production or the start of the different shifts, changes in products and condition of the operation. The main examples of this kind of losses are equipments changeovers, exchange of dies, jigs and tools. These losses consist of setup, start-up and adjustment down times. The amount of these losses is calculated in the form of downtime.
3.9.2 Speed losses
• Minor stoppage losses
These losses are due to the reason of machine halting, jamming, and idling.
Many companies are considering these minor stoppages as the breakdowns in order to give importance to this problem.
• Speed losses
These losses are due to the reduction in speed of the equipment. In other words the machine is not working at the original or theoretical speed. If the quality defect and minor stoppages occurs regularly then the machine is run at low speed to cover the problems. These losses are measured in the term of theoretical to the actual operating speed ratio.
3.9.3 Defect or Quality losses
• Quality defect and rework losses
These losses are due to the defective products during the routine production.
These products are not according to the specifications. So that rework is done to remove the defects or make a scrap of these products. Labour is required to make a rework which is the cost for the company and material become a scrap is also another loss for the company. The amount of these losses is calculated by the ratio of the quality products to the total production.
• Yield losses
These losses are due to wasted raw materials .The yield losses are split into two groups. The first one is the raw materials losses which are due to the product design, manufacturing method e.t.c. The other group is the adjustment losses due to the quality defects of the products which are produced at the start of the production process, changeovers e.t.c.
These six big losses indicate the three main topics which are the availability, performance rate and total yield rate (quality rate). These three topics are the base for the overall equipment effectiveness calculations.
O.E.E = Availability * Performance rate * Quality rate
• Breakdown losses
• Setup and
adjustment losses
• Minor stoppage losses
• Setup and adjustment losses
• Breakdown losses
• Setup and
adjustment losses (Tajiri M., Gotoh F., 1992)
3.10 Overall equipment effectiveness (O.E.E)
The overall equipment effectiveness is the main goal of the TPM system. It is the benchmark of the any TPM process and is used to measure the equipment effectiveness. The formula for equipment effectiveness measures the availability, the rate of performance, and the quality rate. It can be done with the involvement of all departments to measure the equipment effectiveness .The formula of the overall equipment effectiveness is as follows
O.E.E = Availability * Performance rate * Quality rate (Mobley R.K., 2002)
1. Availability
The availability is calculated as the required availability minus the downtime and then divided by the required availability. This can be written in the form of formula as Availability = Required availability – Downtime * 100
Required availability
The required availability can be defined as the time of production to operate the equipment minus the other planned downtime like breaks, meetings e.t.c. The down time can be defined as the actual time for which the equipment is down for repairs or changeovers. This time is also some times known as the breakdown time. The out put of this formula gives the true availability of the equipment. Then further this figure is used in the overall equipment effectiveness formula to measure the effectiveness of the equipment.
2. Performance rate
The performance rate can be defined as the ideal or design cycle time to produce the item multiplied by the output of the equipment and then divided by the operating time. This will give the performance rate of the equipment. The formula to calculate the performance rate can be expressed as
Performance rate = design cycle time * output * 100 Operating time
The design cycle time or the production output will be in the unit of production, like parts per hour and the output will be the total output in the given time period interval. The operating time will be the availability value of the availability formula. The result of this formula will be in the percentage of the performance of the equipment.
3. Quality rate
The quality rate can be expressed as the production input into the process or equipment minus the volume or number of quality defects then divided by the production input. The quality rate can be expressed in a formula as
Quality rate = production input – quality defects * 100 Production input
The production input mean that the unit of product being feed into the production process.
The quality defects mean the amount of products which are below the quality standards i.e. the rejected items after the production process. This formula is very helpful to calculate the quality problems in the production process. (Mobley R.K., 2002)
4. Empirical findings
This chapter is on the empirical findings of the case company situated in Ljungby. Lars Kinnby is the chief of production and we got the all data and information about the company through him. We also collected some information during our visit to the production lines of the company. All calculations of this project are based on one year data of 2006.
4.1 Henjo Plåtteknik AB Ljungby
Henjo Plåtteknik AB is the name of the case company.
4.2 Introduction
Henjo Plåtteknik AB was established in 1945 in ljungby. The founder of this company was Henry Johansson. The Company is not a large one, has only one unite which is in Ljungby with 8000m2 areas. The company has only 74 employees with 13 officers. This company is ISO 9001 and ISO 14001 certified. It is fabricating company which is producing different sheet metal products according to the orders of its customers.
It is working as subcontractor because it has no its own product. It is producing different parts as the requirement of its customers. The company has 150 customers and 10 of them are the main customers of the company which give 80% of the total business of the company. The turn over of the company is increasing almost every year, this shows that the business of the company is increasing continuously. The turn over of the company is 92 Swedish MKr in 2006 (Figure 4.1). The most important customers of the company are Kalmar industries, Electrolux, Wascator, Burtech, Dynapac, Svetruck, Ljungby Maskin, SMV Konecranes, and Rapid Granulator. The order average per month of the company in 2006 is 1510. The company on time delivery average percentage is 82 and 25 percent of this 82 percent on time deliver of the orders is for those orders which are delivered on the same day (see Appendix#1).
company turnover per year
0 20 40 60 80 100
No. of years
MKr
MKr 31 33 44 48 42 50 55 59 61 74 84 92 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Figure 4.1 Turnover of the company from 1995 to 2006
4.3Organizational plan of the company
The organizational plane is showing that all the working areas are working directly under the C.E.O. (Figure 4.2). All working areas are responsible of their works according to their duties and are answerable to the C.E.O. of the company.
C.E.O Sven Bodevind Hans Bodevind
I.T.
Hans Bodevind Magnus Enfors Personnel
Mia Asplund Quality &
Environment Berit Johansson
Ma
Administration Lena Johansson gnus Berg
Production Lars Kinnby
Purchase Johan Hovelius
Sale Hans Andersson
Maintenance Magnus Enfors Production support
Assembly &
Delivery Bending Welding Painting Punching Rolling
Figure 4.2 Organizational plan of the company
4.4 Company working style and different processes
The following layout is showing the company’s working style (Figure 4.3).
When company receive an order from the customer, it first comes in the production planning section. This section makes the plane for the order i.e. when and how much to produce these products according to the customer requirement and according to the resources. The next section is of construction. This section makes the plane about the production method should be used in the manufacturing of the required items. It selects the line and the production machines for the particular items. The purchase section is the responsible to purchase the required items for the production and to provide on time to the production section. The production section is the responsible to produce the products according the planes and specifications receives from the planning section and construction section. These are the four main working processes which are directly involved in the production of the required items. At the end, products are delivered to the customers. There are two supporting processes that are IT and maintenance. These two processes help to make the smooth production. There is another process which makes the measurements and analysis after getting feed back from different sections and from the
customers. It is the management process. The management is the responsible to provide the sources for the production.
Management process Measurement &
analysis Resources
Production planning
Construction Purchase Production
Figure 4.5 Figure 4.6
Figure 4.7
4.5 Products of Henjo Plåtteknik AB
Henjo Plåtteknik AB is producing 5000 different types of products. But these entire products are fabricating from the sheet metals of different sizes as per specifications of the customers. There are some pictures of the products to understand the company’s business (Figures 4.4, 4.5, 4.6, 4.7, 4.8).
Supporting processes
The need of customer
Maintenance
Customers
IT
Figure 4.3 Different processes of the company
Figure 4.4
Figure 4.8
4.6 Description of the production section activities
The company is working to produce different kinds of products as the demand of its customers. This demand varies a lot .That is the main reason that company has a flexible production system. The different activities of the production section have the capacity to work with the different requirements. The most important activities are laser cutting, bending, welding, punching, rolling, painting and assembling. There are many machines are involve in these activities.
Laser cutting
Three machines are involved in this activity. These machines are computerized and working according to the cutting programme.
Different cutting programmes can be feed in these machines as the requirement of the products. These machines can cut the metal sheets up to 20 mm thickness. The average set up time of each machine per day is 8.57 min. and the number of failures per month of each machine are two. The time to restart the machine is 34 (10hr fault fixing + 24hr technician arriving time) hours after each failure of
these machines. The short stoppages of the each Figure4.9 leaser cutting machine machine are 975 per year. Each short stoppage takes 20 min. Eight employees are working in this activity. This working station works 24 hours a day and 7 days a week. It means this is much busy. There are total three working shifts in a day. One shift is consisting of eight hours. Forty minute break is there in each working shift. Two workers are working in each shift every day. The eight workers are mobilised in each shift of the whole week. In other worlds, two workers are remain on standby and can be used in case of emergency. The out put of this work station is 491 products per week. The machine cuts the 1 metre metal sheet in 2.8 minutes. But the machine is cutting 1 metre of the metal sheet in 3.2 minutes. There is no time wastage between the replacement of the metal sheets for the continue work. The rejected products of this work station were 1334 in year 2006.
Bending
There are five machines which are involved in this activity. The capacity of these machines is different. They have the capacity from 85 tones to 230 tones. The average set up time of each machine is 25 minutes per day. Each machine stops once a month due to failure. The time to restart the machine is one day and four hours. The short stoppages of each machine
per year are twenty. The time for each short stoppage is 20 minutes. Ten employees are working in this work station. These employees work in one working shifts each day.
There is a break for coffee of 40 minutes. Only five day per week work is done in this work station. The production capacity of this work station is to produce 266 products per week. The machine ideal cycle time is 6.6 sec (0.11 minutes) i.e. it can make a bend in this time. But the average time between two strokes of the machine is 0.65 minutes. The total 2035 products of this work station were rejected due to the quality problems in year 2006.
Figure4.10 Bending machine
Punching
For this activity, there is only one machine. This machine is also computerized and working according to the punching programme which is feed to it for the particular job. This machine can hold ten different punching tools at a time and can use them one by one as the requirement of the item. The set up time of this machine is 30 minutes per day.
This machine fails three times in a month. The time require to restart the machine is twenty four plus eight hours (i.e. one day production time 8hr + next day 8 hr will be lost ) after each failure. The short stoppages of this machine per year are 90 and each short stoppage consumes 20 minutes. The working specification of the machine is 2000*1000*6 mm. one employee is working and handles the whole work of this work station. The only one working shift is there for this activity per day and it works five days a week. The 40 minutes coffee break is included in the shift time. This work station produces 24 products per week. The machine ideal capacity is to punch a metal sheet of size 600 mm*280mm in 7 minutes. But the average time to punch this size of sheet is taking 12.21 minutes. Only 9 products of this work station were rejected due to the quality problem in whole year.
Welding
Figure4.11 welding machine Robot welding machines are used in this activity. There
are two robot welding machines. A welding programme is feed to these machines and then they work as the instructions of the programme. This work station works in one shift per day and 45 minutes coffee break is also included in the working shift time.
This work station work five days a week. The set up time for each machine is 30 minutes per day. Once a month each machine fails.
Time to recover the fault and restart the machine is twenty four plus two hours (i.e. one day production time 8hr + next day 2 hr will be lost ). The short stoppages of each machine per year
are 20 and each short stoppage take 20 minutes. Four employees are involved in this welding work. Fourteen Hands welding employees are also involve in this activity. They make the semi welded object. This work station produces 77 products per week. The robot welding machine can weld a metal product with the ideal speed of 300 mm in 10 sec. but average time which machine is taking to weld 300 mm is 39.68 sec. the rejected products of this work station in whole year were 486 products.
Rolling
There are two rolling machines to perform the rolling work on the metal sheets.
The roll’s length of one of the machines is 1000mm and other machine has the roll length of 2000mm.the speed of these machines is controlled through the control panels of the machines. The set up time of each machine per day is 15 minutes. These machines fail once in two months and this failure takes twenty four plus four hours to restart the machine again. The number of short stoppages of each machine per year is 20 and time which is consumed in each short stoppage is 15 minutes. This data is of these machines of early years when the machines were working with full capacity. Now a day, these machines are working one or two times in a week. There is only one person to handle the entire load of this work station. This work station is available for one shift to work. The break time of this work station is 40 minutes in the working shift. This work station is producing 31 products per week.
Painting
The company has a system for the paint of its products. For this purpose, the company has a good automatic paint plant. There are many steps are involved in this plant. The set up time of this plant is two hours. The plant fails once a month. The time to finish the problem and to start the plant once again is twenty four plus four hours. The short stoppages of this plant per year are 18 and each stoppage takes the 30 minutes. The six employees are working in paint shop. This work station has only one working shift with 45 minutes coffee break. This working shift also depends on the products available for the paints. The paint shop is painting 128 products per week. In the whole year, 126 products were rejected of this work station.
Assembling
The last activity of the production process is the assembling of the different parts of the products. The three employees are involved in this activity in one working shift of the production. The employees has 45 minutes coffee break during the working shift. Different tools (hammer, screw drivers e.t.c.) are used to assemble the parts and to give them the final product shape. The assembling area’s employees assemble 24 products per week. But some times, the employees do mistake in assembling the different parts. So due the assembling problem, the 28 products were rejected in the whole year.
4.7 Production process
The production process of the company is complicated and consists of different production lines (see Figure 4.12). This is only due to the big variation of the product’s demand of its customers. Production process starts from the main store. The metal sheets are issued for the work as the requirement of the order to the work stations i.e. Laser cutting or punching. These two work station are at the start of all the production lines. When metal sheets reach in the laser cutting work station with job plan and specification then operator takes the metal sheet and put it on the plate form of the mention machine for the laser cutting. After fixing the metal sheet on the plate form of the machine, operator starts the machine and machine starts its work according to the cutting programme which is already feed in its operating device. Before starting, operator sets the laser intensity of the laser beam. When machine starts, the plat form of the machine with metal sheet moves in side of the machine and reaches at a fixed point (zero position).
After cutting the whole cut metal sheet comes out from the machine and at the other metal sheet moves inside of the machine for the cutting. There are two plate forms of the machine which work alternatively i.e. one goes inside of the machine and other is ready for the loading of the next metal sheet. Operator takes the cut metal pieces and checks the quality of them and goes to the next work station with these metal pieces to hand over them for the next operation. What will be the next operation it depends on the specification. The next station can be bending, welding, painting or assembling after the laser cutting work station.
Let’s consider the next work station is bending. It works according to the instructions as the laser cutting work station works. Operator sets the plate form of the machine according to the specification of the job before starting the machine. After adjustment of the machine, two operators put the metal piece or metal sheet on the plate form of the machine between the edges, which they have fixed on the plate form to get the require result. Then one of the operators starts the machine for the stroke to make a bend.
After stroke the machine head goes back and operator pick up the piece with bend. They check the bend according to the requirement if they find some problem in the bend then they put this piece once again in the machine for the same operation or some times they use hammer to get the require results. They make many bends on the piece according to the specifications or drawing. They hand over the bended pieces to the next work station for its operation after bending some pieces.
If the metal pieces or metal sheet comes in the welding work station, there are robot welding machines. But before robot welding of the different pieces, the manual welding is done to make a semi welded object. The Operators see the job instructions and put the semi welded metal object on the machine plate form. These welding machines are computerized and works according to the operating programme which is already feed in it. The operator set the plate form of the machine before putting the object on it according to the welding operation programme of the machine. They use the electric hoist to put and to remove the object from the plate form of the machine. The operators have the responsibility to check the quality of the weld. After inspection, they keep the object one side and put another semi welded object on the plate form of the welding machine.
They hand over their welded objects to the next work station for its operation after welding some objects.
There is a work station which is for paints. When the metal pieces or objects comes in the paint shop for painting, the operator of this paint shop checks the instructions and hang the objects on the moving belt of the plant which is used to carry the objects in and out purpose through the plant. Before the painting process, the operator checks the right quantity of the paint powder and other chemicals which are used in the painting.
Operator checks the quality of the paint on the objects after painting and hands over to the next station which is of the assembling of different parts or just for store as the finish product. In the assembling, the employees of this station read the instructions and see the drawing and assemble the different parts to make the final product.
If we see the right side of figure 4.12, there is a punching work station. When pieces reach in this work station, the operator sees the instructions and drawing and then fixes the different punching tools in the machine. This machine use the require tool according to the punching programme, which is feed in the machine memory. Operator initializes and fixes the space for metal piece on the plate form of the machine before starting it for the punching operation. After punching, operator checks the quality of the punches and then puts other metal piece on the plate form of the machine for the punching operation. After punching some pieces, he gives them to other work station for the other operation. Other work station is for the rolling purpose. The operator of these machines fellow the instructions and drawing to roll the object. He just takes the object and put it in the rolls of the machine. Before putting the object in the machine, he sets the speed of the rolls and the gap between them. Operator checks the rolling quality as per drawing. He has the responsibility to give the rolling object according to the drawing. He gives the rolled object to the next work station for its operation on the object. All production lines end at the assembly and final product store area. The final products to the customers are delivered from this area.
Production process flow diagram
Main Store
Laser cutting work station Punching work station
Bending work station Welding work station
Painting work station
Assembly & Store
Customer
Rolling work station
Figure 4.12 Different production lines of the company 4.8 Quality
The company is facing the quality problems. The company paid 818182 SEK due to the quality problems in 2006 (see Appendix#2). This amount is 0.89% of the turnover of the company. The operators has the responsibility of good quality and they are themselves checks the quality of the products. There are no special quality checkers in the production area. The company has a section for checking the quality of the products. But this section just checks the quality of the first piece of the production daily. The other all production quality depends on the operators.
4.9 Maintenance
The company has the preventive maintenance strategy for the all machines in the company. They have the contract with the machines manufacturing companies for preventive maintenance. This maintenance plan is different for different machines. One week per year is
