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Reducing the amount of
waste for Muelink & Grol
Don’t waste your scrap
Master thesis 15-11-2010
Performed for: Muelink & Grol B.V. & University of Groningen First supervisor University of Groningen: H. van der Meulen Msc.
Co-assessor University of Groningen: Prof. dr. ir. J. Slomp Supervisor Muelink & Grol Drs. ing. M. Smit
Student: Ing. M.J. Sloet Bsc. Student number: 1843443
Master of Science Technology Management
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MANAGEMENT SUMMARY
M&G is a leading manufacturer of Flue Gas Systems in Europe. The company was founded in 1932 and experienced steady growth. A few years ago M&G was hit by the worldwide financial crisis. Fewer customers paid out in decreased revenues and therefore cost reduction solutions are sought. This research is based on the following research question:
““How can M&G improve its plastic production to reduce waste by using lean manufacturing principles?”
In the diagnoses, a VSM analysis led to the conclusion that from the seven lean wastes ‘defects’ are of main interest. Measurements showed that M&G had a scrap rate of 18,88% with total material scrap costs of € 136.342 over 2008.
With the VSM as a basis the sources of scrap are identified using the quantitative metric Overall Equipment Effectiveness. The OEE analysis is applied to measure productivity of individual equipment in a factory. It identifies and measures losses of important aspects of manufacturing namely availability, performance, and quality rate (figure 1).
The main points of interest that were identified from this analysis are the high amount of quality defects (approximately 250 kg/day) caused by rejects, an inappropriate extrusion pipe length, the down time losses caused by set-up and adjustment and machine breakdowns. For extrusion over 4,5 hours/day of production time is lost due to high machine changeover times, the usage of a corrective maintenance policy and incorrect planning. The following OEE metrics influence scrap levels for M&G.
The lower the availability of extrusion the higher the amount of scrap. Scrap is caused by machine changeovers and breakdowns. Changing between material colors can take up to several hours, whereby the line has to run at a steady pre-specified pace.
Also the performance of the extrusion line is related to the amount of scrap. The higher the performance the harder it is to achieve proper product quality. Currently the performance of the extrusion line is 65%.
Low quality is an aspect that is correlated to both the extrusion and Sica lines. The lower the quality percentages, the higher the amount of rejects and defects and thus scrap (figure 2).
Total scrap Total production Percentage of scrap Total costs scrap
66.464kg 352.000kg 18,88% € 136.342 Line A P Q Extrusion 80,2% 65,0% 91,4% Sica 1 79,8% 62,8% 95,5% Sica 2 81,6% 68,1% 95,9% 44,0% 45,0% 46,0% 47,0% 48,0% 49,0% 50,0% 51,0% 52,0% 53,0% 54,0% OEE Extrusion 47,6% Sica 1 47,9% Sica 2 53,3% P e rc e n ta g e OEE
Figure 1 – OEE percentages
Figure 2 – Relation OEE to scrap Low availability High performance Low quality Extrusion Sica Extrusion Sica Extrusion Sica Correlation to scrap + + + +
3 Now that the problem is verified and the main sources of scrap are identified design solutions are sought to reduce the amount of scrap. In the design phase a waste hierarchy model is used, which classifies the importance of system improvements starting from elimination to disposal at the end (figure 3). This led to the following recommendations:
1. Eliminate – A benchmark study performed at InterActive B.V. indicated that there is no need to pay for scrap disposal. As M&G currently pays € 30.000/year for scrap collection disposal companies were sought to eliminate these costs. This resulted in Kaymar B.V., located in Groningen, which is willing to collect scrap for free.
2. Reduce – The four design solutions leading to scrap reduction are the following:
• A recalculation of the ideal extrusion pipe length revealed that the current length of 4315 mm is inappropriate and needs to be set to 6240mm, resulting in approximately 45% scrap reduction, approximately 10% cycle time reduction and yearly savings of € 40.000 without problems worth mentioning.
• M&G should follow a preventive maintenance program instead of corrective maintenance. Literature reveals that the costs for corrective maintenance are about three times higher than for preventive maintenance.
• In order to reduce setup and adjustment time, M&G should apply the lean principles SMED and 5-S. A SMED analysis carried out for an extrusion diameter changeover concluded in a possible reduction of 62% of time.
• M&G should focus on training to improve process knowledge and motivate operators to come up with ideas. Extrusion is a process that requires highly specialized knowledge. 3. Re-use – There are opportunities to re-use material that is processed at the Sica lines and is
judged as scrap in the current situation. There are numerous articles that cause over 500mm of scrap which are applicable for re-use by cutting it into smaller lengths. This results in savings of over € 3000/year on a pure material basis only.
4. Recycle – Material that cannot be re-used, reduced or eliminated should be recycled. A gravimetric slide blender is designed to blend virgin pellets with regrind. The initial costs for such a machine are € 10.000 with an estimated pay-back period of 1,93 years. Hereafter approximately € 5.168/year is saved.
5. Disposal – Once all previous mentioned recommendations are carried out and implemented the rest of the material scrap is disposed.
W aste hierarchy 1 Elim inate 2 Reduce 3 Re-use 4 Recycle 5 Dispose
4 Following up the recommendations would lead to nearly 5% of total scrap reduction with yearly savings of nearly € 80.000. In addition to this M&G establishes a higher level of basic stability and environmental benefits are gained by disposing fewer scrap. To support this an action priority matrix is added in the report which prioritizes recommendations on effort and financial impact to the company.
The current progress of implementation can be found in table 3. Disposal costs are eliminated and the first tests with an increased pipe length of 6.240mm are carried out.
Recommendation Implementation
1. Eliminate disposal costs Carried out
2. Increasing pipe length In progress
3. Cutting pipes into smaller pieces In progress
4. Replacing head/screw In progress
5. Preventive maintenance program No action taken yet
6. Training of operators No action taken yet
7. Recycling (gravimetric) In progress
Recommendation Impact Financial benefit Waste hierarchy
1. Free disposal of scrap Eliminating scrap disposal costs €30.000/year (depends on amount of scrap)
Eliminate 2. Increase extrusion pipe
length
41,3% reduction of scrap expressed in pipe length (m)
Approx. €40.000/year Reduce 3. Total productive
maintenance
Reducing break-downs, increasing OEE
Further research Reduce 4. Apply SMED/5S Reducing changeover time,
increasing OEE
Further research Reduce 5. Training Increasing knowledge, thinking
along in the process
Further research Reduce 6. Reuse of pipe lengths Additional 6,5% reduction of
scrap
Approx. €3.351/year Re-use 7.Gravimetric slide
blender
Recycling of scrap material Approx. €5.168/year Recycle
Table 2 – Recommendations
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TABLE OF CONTENT
Management summary ... 2 Table of content ... 5 Preface ... 8 1.Introduction research ... 9 1.1 Introduction company ... 91.2 Reason for research ... 10
1.2.1 List of requirements ... 11 2.Research ... 12 2.1 Research methodology ... 12 2.2 Problem statement ... 12 2.2.1 Research objective ... 12 2.2.2 Research model ... 12 2.2.3 Operationalisation ... 13 2.2.4 Research question ... 14 2.2.5 Sub-questions ... 14 2.2.6 Research structure ... 14 2.3 Research boundaries ... 15 3.Theoretical framework ... 16 3.1 Lean manufacturing ... 16 4. Current situation ... 18 4.1 Machines ... 18 4.1.1 Extrusion line ... 19 4.1.2 Sica line(s) ... 19 4.2 Material ... 20 4.2.1 Product specifications ... 20 4.3 Methods ... 21 4.3.1 Maintenance ... 21 4.3.2 Planning ... 22 4.4 Manpower ... 22
5. Diagnoses - Value Stream Mapping ... 24
5.1 VSM explanation ... 24
5.2 Lean 7 wastes ... 24
5.3 Conclusion ... 26
6.Diagnoses - Problem verification ... 28
6 6.2 Scrap calculation ... 29 6.2.1 Extrusion line ... 29 6.2.2 Sica line ... 29 6.3 Zero measurement ... 29 6.4 Scrap disposal ... 30 6.5 Total scrap ... 30
7. Diagnoses - Overall equipment effectiveness ... 31
7.1 Introduction ... 31
7.2 Availability ... 31
7.2.1 Root causes extrusion ... 32
7.2.2 Root causes Sica lines ... 34
7.3 Performance ... 34
7.4 Quality ... 35
7.5 Overall Equipment effectiveness ... 36
7.6 Conclusion OEE ... 36
8. Design ... 37
8.1 Introduction ... 37
8.2 Elimination of scrap disposal costs ... 38
8.3 Reduction of scrap ... 38
8.3.1 Ideal Extrusion pipe length ... 38
8.3.2 Machine downtime ... 43 8.3.3 OEE calculator ... 46 8.4 Reuse ... 47 8.5 Recycle ... 49 8.6 VSM future state ... 50 8.7 Conclusion ... 51 9. Implementation ... 52 9.1 Introduction ... 52 9.2 Implementation priority ... 53 9.3 Implementation progress ... 54 Research conclusion ... 56
Discussion and further research ... 59
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Appendices ... 62
Appendix 1 – Muelink & GRol group ... 62
Appendix 2 - Photo report production ... 63
Appendix 3 – Processes ... 65
Appendix 4 – Situation M&G ... 66
Appendix 5 – Questionnaire scrap ... 67
Appendix 6 – Results questionnaire scrap... 69
Appendix 7 – Pareto chart ... 70
Appendix 8 – Scrap percentage sica current situation ... 71
Appendix 9 – Zero measurement ... 72
Appendix 10 – Scrap disposal costs ... 73
Appendix 11 – OEE formulas ... 73
Appendix 12 – Performance Sica ... 74
Appendix 13 – Scrap percentage proposed situation ... 76
Appendix 14 – Scrap percentage different diameters ... 78
Appendix 15 – Benchmark Interactive ... 79
Appendix 16 – Calculated OEE data ... 81
Appendix 17 – List of companies for scrap disposal ... 82
Appendix 18 – Bottleneck analysis ... 83
Appendix 19 – SMED diameter changeover extrusion ... 84
Appendix 20 – Recycling by regrind ... 87
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PREFACE
As a start, I would like to say that performing this research was an interesting, defying learning experience. Linking theory and practice made me realize where my interests are and what my future direction might be.
This report is written as part of the master thesis Technology Management at the Faculty of Economics and Business, University of Groningen. The research is executed for Muelink & Grol, a leading manufacturer of flue gas systems in Europe. The purpose of the research is to create an insight in waste generated by the company and ways to reduce it.
Without the support of people in and around M&G the execution of the research would not have been possible. I would like to thank everyone who contributed to the realization of this report. Special thanks go out to the supervisers of the University H. van der Meulen Msc. and Prof. dr. ir. J. Slomp and my student colleagues K. Timmer Msc. and W. van der Goot Msc..
Furthermore I would like to thank Michiel Smit and Richard Kramer for the supervision during the research. They were closely involved and supported me and made it possible for me to implement my recommendations.
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INTRODUCTION RESEARCH
People create new technologies and industries to meet human needs more effectively and at lower cost. Innovation is a major agent of progress, and yet innovators’ incomplete knowledge leads to undesirable effects. Such unforeseen consequences of new inventions or processes are not unique to the feverish industrialization of the 19th and 20th centuries. By the year 2030, 10 billion people are likely to live on this planet which on the waste side of the ledger would generate 400 billion tons of solid waste every year enough to bury greater Los Angeles 100 meters deep.
These numbers are not meant to be forecasts of a grim future, but emphasize the incentives for recycling and conservation. They lead to the recognition that the traditional model of industrial activity in which individual manufacturing processes take in raw materials and generate products to be sold plus waste to be disposed of should be transformed into a more integrated model; a system in which consumption of energy and materials is optimized, waste generation is minimized and the effluents of one process serve as the raw material for another process.1
1.1 INTRODUCTION COMPANY
Muelink & Grol (M&G) is a leading manufacturer of Flue Gas Systems in Europe. The company was founded in 1932 in Groningen and developed an extensive knowledge of legislation in in several countries in and outside Europe over the years. They are a total supplier of flue and ventilation systems for their customers. The M&G group has an annual revenue of €135 million with a total labour force of approximately 750 employees (dependent on temporary workers).
M&G has always focused on new developments and innovative products. The strong home market position enabled the company to prepare itself for the growing export market throughout Europe, in which it developed itself very successfully from the late eighties onwards. Dutch boiler manufacturers were strong in developing efficient gas fired boilers for central heating systems and hot water supply. These manufacturers became important suppliers for the European market as the use of natural gas systems became more widespread throughout Europe. M&G followed this trend and made sure it was constantly innovative and leading in the development of safe systems in accordance with the various national legislations.
The leading position of M&G is a result of the constant interest and investment in Research and Development. M&G has its own laboratory with testing equipment at its disposal to perform measurements in accordance with European Standards. To guarantee a program of products with high quality the production methods are continuously monitored. Motivated personnel and machines controlled by modern computers form the basis for efficient manufacturing. The relationship with manufacturing partners, technical institutes and inspection authorities are of great importance to ensure top quality (see appendix 1 for more information).
Figure 1.1 illustrates the three buildings of M&G. Building A is the warehouse that contains orders that are ready for expedition and storage of raw material and semi-finished products. In the other two buildings the production processes take place. In building C the plastic operations are carried out: extrusion and Sica’s. Building B is the main factory in which the remaining operations are carried out. The production processes have a functional layout split up in four departments: plastics, assembly, paint shop and packing. M&G
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10 employs approximately 150 permanent employees from which about half are direct production employees and the other half have supportive functions. Besides permanent employment M&G utilizes approximately 50 temporary workers for production, dependent on customer demand. The main customers of M&G are Original Equipment Manufacturers (OEM’s); they manufacture products using components bought from M&G. 95% of M&G’s revenue is generated by boiler manufacturers in Europe. The three major customers are Bosch, Remeha and Vaillant. Furthermore 3% of the revenue is generated by industrial heating manufacturers from Germany and France and finally 2% is generated by the ambiance lighting manufacturers in Holland, thus M&G’s market is primarily in Western Europe. However, the Eastern European and Mid East markets are developing. M&G has a market share of 90% and the three biggest competitors are Cox Geelen, Ubbink and Centroterm.
The wide range of products are produced in aluminium, stainless steel and plastics (PP/PPs). The main product groups are:
• Flue systems, which can be delivered in various diameter ranges and materials, such as Twin Flue, concentric, cascade, flexible and collective flue systems.
• Hybalans plus – a ventilation system that provides the supply as well as the discharge of ventilating air with a high focus on energy saving.
• Customized products – products produced according to the customers specification.
1.2 REASON FOR RESEARCH
Since its founding in 1932 M&G experienced high levels of growth. More and more products were sold and higher profits gained. There was no clear need to change organizational and/or production processes. The primary goal of M&G is to serve its customers at the best possible way to maximize the service level. In 2008, as many other companies, M&G was hit by the worldwide financial crisis. As a result, fewer customers led to decreased revenues. This was the beginning of many changes for M&G. In the past year the production process became a central aspect in the organization, new personnel was hired and shifts in employee functions took place. M&G decided to implement lean manufacturing which was by the following statement:
“M&G has proven to be very successful over the last years. The direct results of this success are a growing market share and very good results, but also a company where not everyone knows what is expected and to who(m) one is accountable. In short, ambiguity about roles and responsibilities and confusion about methods for improvement. The management team concluded that in addition to a distinct structure concerning responsibilities, also the company’s structure needs adjustment in order to improve the actual performance. To start these two coherent steps it is decided to apply the lean methodology to realize the projects.”
The operation manager took the initiative to introduce the lean thinking principle to eliminate non-value added activities. An important division of M&G subject to increasing costs is the manufacturing of plastic parts. On this basis a research was requested to analyze and map the current system of plastic manufacturing with the goal to reduce the costs of waste. Based on interviews it is concluded that waste levels and the costs associated with it are increasingly high and implore for reduction. The original complaint given is the following:
11 At this stage pluralism is necessary to approach the problem objectively. The original complaint implies that the amount of manufacturing waste (referred to as scrap) is too high, but lean manufacturing approaches waste from a broader perspective. Lean describes waste by means of the 7 wastes (chapter 3). In order to set a research boundary one needs to clarify which of the seven wastes have the highest influence on the system taking into consideration requirements set by the operation manager.
1.2.1 LIST OF REQUIREMENTS
The following list of requirements is composed to set standards for the research design. The following aspects need to be taken into consideration:
• There should be limited costs involved (incremental improvement);
• Quick results need to be yielded due to the current circumstances within M&G; • Should be in line with the lean philosophy;
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2.
RESEARCH
2.1 RESEARCH METHODOLOGY
The methodology that will support this research is the DDC (diagnoses, design, change) method by de Leeuw (2003). It is a structural method to approach managerial problems. In the diagnose phase the first thing to do is to write down the original complaint and problem statement. It is important to conceptualise and analyse the problem and to describe (model) it. The design phase defines which direction needs to be taken to solve or improve the problem and to elaborate on it. In the third phase (change) is to change the actual system is changed using the solutions given in the design phase. The research will focus on the first two phases. A start has been made with the third phase.
2.2 PROBLEM STATEMENT
A problem statement is on the one hand about mutual agreement with the principal and on the other about internal control of the research (de Leeuw, 2003). On the occasion of M&G’s goal to reduce waste of plastic processing a problem statement is made consisting of a goal, a conceptual model, operationalisation, research question and sub-questions.
2.2.1 RESEARCH OBJECTIVE
The research objective clarifies the relevance of the research, i.e. why the research is performed (De Leeuw, 2003). For the research the following objective is formulated:
“Describe the current system of plastic processing and provide recommendations on how to reduce waste by implementing lean manufacturing principles and recommend which tools are applicable for M&G”.
From this objective, it is clear that the main focus of research is to reduce waste with a limitation to plastic manufacturing. Plastic manufacturing entails a series of machines that are discussed in chapter 4.1.
2.2.2 RESEARCH MODEL
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Figure 2.1 – Research model
2.2.3 OPERATIONALISATION
Waste. Waste is any aspect of an operation that fails to add value. It is a significant hidden cost for
many plastic processing companies and typically costs 10 – 15 times more than the costs of disposal (Envirowise, 2001)2. In order to elucidate the sources of waste it is important to map the actual wastes.
Manufacturing. Manufacturing includes all steps necessary to convert raw materials, components,
or parts into finished goods that meet a customer's expectations or specifications. Manufacturing commonly employs a man-machine setup with division of labor in a large scale production.3
Manpower. Stability in a manufacturing environment starts with a well trained workforce. Employees
tend to know their jobs very well, but despite this it is important to focus on the further improvement of the skills and capabilities of work teams (Smallley, 2008). It is important to have a workforce empowered to make changes and improvements in products and processes and have the necessary skills to do so. Many organizations operate as if improvement is solely the business of managers, consultants, analysts and engineers. When employees learn that seeking out and suggesting improvements is the sole responsibility of specialists, they will stop looking for improvement possibilities (Nicholas, 2008)
Machines. It is not necessary to have equipment with perfect uptime. More important is to know the
capacity and actual output of your process. It is important to measure the true output potential of a process during a typical shift. For example, if the customers demand is 700 units per shift and your actual output is only 500 units despite having capacity for 1000, then you need more availability (Smalley, 2008).
Materials. In general the goal of lean production is to reduce waste and shorten the timeline from
when an order is received until the time it is produced. For batch processes, some amount of inventory is required to cover for the time when other parts are running, or tools are being changed. Not all inventories are waste, only inventory beyond what is needed to run the process is waste. Inventory often exists as a symptom of a problem in the process. Solving the problem earns you the right to reduce the inventory (Smalley, 2008).
Methods. In order to have stable manufacturing standard methods are required. The normal
definition of standard is that it is a rule or way to do things. The unintentional side effect is that people are not encouraged to question or change the rule. “We do it this way because that is our
2
http://envirowise.wrap.org.uk/
3
14 company standard” is a phrase that is often heard. Toyota uses this definition slightly different. They define it as a “rule or basis for comparison.” A standard is nothing more than a tool to measure how things are done and refer to when change is necessary. Lean thinking is about changing work methods in order to eliminate waste and make improvements (Smalley, 2008).
2.2.4 RESEARCH QUESTION
Based on the available information the following research question is formulated:
“How can M&G improve its plastic production to reduce waste by using lean manufacturing principles?”
2.2.5 SUB-QUESTIONS
In order to answer the research question it is divided into 8 sub-questions. Answers to the sub questions should expose key problem areas and provide practical insight in auditing the research problem. Table 2.1 shows the sub-questions in combination with the chapter in which they are discussed.
Sub questions Chapter
Theoretical
What is waste and how does this relate to lean manufacturing? 3
Diagnoses
How is the plastic manufacturing of M&G organized? 4
Which type(s) of waste is most suitable for improvement? 5
How much waste is currently created per machine/line? 6
What are the sources of the generated waste? 7
Design
What are the possibilities to reduce waste? 8
Which lean manufacturing principles are helpful to reduce waste for M&G? 8
Implementation
How should the recommendations be implemented and what is the current progress? 9
2.2.6 RESEARCH STRUCTURE
This study’s presentation is organized in four parts: a theoretical framework, the diagnoses, design and implementation. The content of these phases will be shortly explained. Figure 2.2 depicts the research structure.
Table 2.1 – Sub-questions
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Extrusion Belling
Packing
Assembly Expedition
Theoretical framework. Chapter 3 is considered as an orientation to lean manufacturing and
describes lean aspects/tools that are applicable to analyze the system. Two methods are described: Value Stream Mapping (VSM) and Overall Equipment Effectiveness (OEE).
Diagnoses. Chapters 4, 5, 6, and 7 are about the diagnoses of the system. Chapter 4 describes how
M&G operates discussing the four manufacturing M’s. In chapter 5 an epigrammatic Value Stream Map is given to find out which of the seven wastes influence the system the most considering the list of requirements. Chapter 6 verifies the problem and in chapter 7 the OEE methodology is applied to the system.
Design. In the design phase (chapter 8) process improvements are described and recommendations
are given to reduce the costs of plastic manufacturing for M&G.
Implementation. In the implementation phase (chapter 9) recommendations are prioritized and the
current implementation progress is described.
2.3 RESEARCH BOUNDARIES
Within the boundaries of this research there are basically two processes. The first process is the extrusion of polymers to form hollow pipes and the second process is belling of the pipes. In chapter 4.1 both processes are described in more detail. Figure 2.3 gives a simplified representation of the research boundary.
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3.
THEORETICAL FRAMEWORK
In this chapter lean manufacturing and its connection to waste is described together with mapping tools to measure and analyze the system. Lean manufacturing is chosen as a guideline because of the introduction of lean thinking principles to the company. It provides an answer to the following sub-question: “What is waste and how does it relate to lean manufacturing?”
3.1 LEAN MANUFACTURING
After World War II Japanese manufacturers were faced with the dilemma of vast shortages of material, financial, and human resources. The problems that Japanese manufacturers were faced with differed from those of their Western counterparts. These conditions resulted in the birth of the “lean” manufacturing concept. Toyota Motor Company, led by its president Toyoda, recognized that American automakers of that era were out-producing their Japanese counterparts. In order to make a move toward improvement early Japanese leaders such as Toyoda Kiichiro, Shigeo Shingo, and Taiichi Ohno devised a new, disciplined, process-oriented system, which is now known as the “Toyota Production System,” or “Lean Manufacturing.” (Nicholas, 1998).
The rationale underlying lean manufacturing is to help researchers or practitioners to identify waste in individual value streams and, hence, find an appropriate route to removal, or at least reduction, of this waste. The use of such waste removal to drive competitive advantage inside organizations was pioneered by Toyota’s chief engineer, Taiichi Ohno, and SENSEI Shigeo Shingo (Shingo, 1989) and is oriented fundamentally to productivity rather than to quality. The reason for this is that improved productivity leads to leaner operations which help to expose further waste and quality problems in the system. There are seven commonly accepted wastes in the Toyota Production System (TPS):
- Overproduction. Discourages a smooth flow of goods or services and is likely to inhabit
quality and productivity. It also tends to lead to excessive lead and storage times. As a result defects may not be detected early and products may deteriorate.
- Waiting. Time is being used ineffectively. In a factory setting this waste occurs whenever
goods are not moving or being worked on. This waste affects both goods and workers, each spending time waiting.
- Transport. Goods being moved out. Any movement in a factory could be viewed as waste and
so transport minimization rather than total removal is usually sought.
- Inappropriate processing. Occurs in situations where overly complex situations are found to
simple procedures such as using a large inflexible machine instead of several small flexible ones. The ideal, therefore, is to have the smallest possible machine, capable of producing the required quality.
- Unnecessary inventory. Tends to increase lead time, preventing rapid identification of
problems and increasing space, thereby discouraging communication.
- Unnecessary movements. Involve the ergonomics of products where operators have to
stretch, bend and pick up when these actions could be avoided. Such waste is tiring for employees and is likely to lead to poor productivity and often to quality problems.
- Defects. The Toyota philosophy is that defects are direct costs and should be regarded as
opportunities to improve. The defects are seized on for immediate Kaizen activity.
17 Waste is all about aspects that do not add value to the product. In order to start a waste reduction program it is most important to first elaborate on how much waste is actually created. In order to reduce waste, there are actually three applications that can be defined and that have to be carried out. First of all the waste must be identified (finding out which resources are used and possibly how much is waste). In order to identify the seven wastes Value Stream Mapping (VSM) is a widely accepted tool. VSM is simply transferring information about the value stream to a ‘map’, which represents either the current or future state of the manufacturing system (Chen et al., 2008). It consists of all the material and information required in the manufacturing of a product and how they flow through the manufacturing system.
The second step is measuring the actual waste (quantification of waste or any non-value added activities) and in the implementation phase, waste must be eliminated (eradication or reduction of waste or any non-value added activity).
For measurement, lean metrics guide an organization in their transformation into lean enterprises. It involves visible performance measures, targeted improvement, team reward and recognition. Most of the existing metrics have poor links to production issues and better links to financial and accounting ones. The selection of effective performance measurement metrics is the key to achieve the goals. In the 1980s, Nakajima (1988) launched Total Productive Maintenance (TPM), which provides a quantitative metric called Overall Equipment Effectiveness (OEE) for measuring productivity of individual equipment in a factory (figure 3.1). It identifies and measures losses of important aspects of manufacturing: availability, performance, and quality rate. The OEE concept is becoming increasingly popular and has been widely used as a quantitative tool essential for measurement of productivity in manufacturing operations (Huang et al. 2003). There is an ongoing discussion whether TPM and thus OEE fall under the denominator lean or not. As TPM works on the dual objectives of zero breakdowns and zero defects, this results in improved productivity and efficiency of equipment, which is linked to waste reduction and is therefore considered as lean manufacturing.
The OEE tool is designed to identify losses that reduce the equipment effectiveness. These losses are activities that absorb resources but add no value to the product. Value-adding operations involve the conversion or processing of raw materials or semi-finished products through the use of manual labor, such as sub-assembly of parts. The following six big losses are identified by Nakajima (1988):
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4.
CURRENT SITUATION
In this chapter the current situation of M&G is described using the conceptual model. The four manufacturing M’s are discussed to create a better understanding of the system. The chapter gives an answer to the sub-question: “How is the plastic manufacturing of M&G organized?”
In order to visualize and determine the root causes of waste, causal mapping is applied. Causal maps are an essential tool for managers who seek to improve complex systems in the areas of quality, information systems , and strategy. These causal maps are known by many names, including Ishikawa (fishbone) diagrams and risk-assessment mapping tools (Hodgkinson, Tomes, & Padmore, 1996). A putative first-level causal map (figure 4.1) is applied as a diagnostic tool to focus attention on the root causes of the problem by means of the four manufacturing M’s, which are discussed further in the report.
4.1 MACHINES
As explained in the conceptual model, the processes that are carried out influence plastic production and thus generate waste. In this subparagraph the production processes of plastic parts are discussed to create more insight in what machines are in operation. In appendix 2 a photo representation of the machinery is given. Figure 4.2 gives a simplified representation of the processes that are carried out.
Man Machine Material Method Training Qualifications Measurement Maintenance Quality Design Waste Technology Condition
Figure 4.1 – Fishbone diagram
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Figure 4.4 – Belling machine
4.1.1 EXTRUSION LINE
Extrusion is a process in which a material is forced through a shaped orifice, with the material solidifying immediately to produce a continuous length of product. Squeezing toothpaste from a tube is a similar process. In plastic extrusion, thermoplastics are softened by heating prior to extrusion and after extrusion the thermoplastics must be quickly cooled to preserve their shape, and, usually, supported while cooling. The extrusion line is built up using several different machines that cooperate together to create hollow pipes in varying diameters with a standard length of 4315mm. In appendix 3 the machinery is discussed in a sequential order, from dosing station to cutter. The following figure 4.3 gives a simplified representation of the extrusion process (from right to left).
Figure 4.3 – Extrusion line
The extrusion process is largely a black box process. In other words, it is not possible to visually observe what goes on inside the extruder. What happens between the feed opening and the die exit cannot be seen, because the process is obscured by the extruder barrel. Measuring instruments have to be correctly calibrated and it should be ascertained that the instrument is capable of measuring the variation in the parameter it is supposed to monitor. An extensive understanding of the extrusion process is necessary. For people new to extrusion, it is recommended to take classes that cover material characteristics of plastics, typical features of extrusion machinery, instrumentation and operating control, the inner workings of the extruder, as well as screw and die design (Giles et al., 2005).
Troubleshooting is often the most critical element of extrusion engineering because of the huge financial impact that extrusion problems can have. Before dealing with specific extrusion problems, there are some issues, which should be addressed first. When the extruder develops a problem, it is very important to be able to diagnose the extruder quickly and accurately in order to minimize downtime or off-quality product.
Because of the required extensive understanding and the costs associated with troubleshooting it is decided not to focus on the internal working of the extrusion line. In the following subparagraph the Sica line(s) are discussed.
4.1.2 SICA LINE(S)
M&G uses two Sica lines to mould sockets (smooth, or with seal seat) on rigid PP pipes, respectively Sica 1 and Sica 2. The following steps are taken sequentially:
20 Both lines are able to process pipes with diameters between 32-160mm and a cut length between 250-2000mm. The line is used downstream from the extruder. During standard molding, high pressure air is forced into the internal side of the heated pipe and shapes the socket against the mould. The unit is made up by three ovens that can be operated independently; they heat up progressively the pipe until the ideal temperature for the molding of the socket is reached. To make the machine more versatile, it can be set up with different configurations, thanks to a series of tools available on request, allowing to bell up to 3 pipes at the same time. The positioning arms fulfill the task of translating and positioning the pipe from one work station to the next; they are activated by pneumatic cylinders. The proximity sensors detect the position of the pipe allowing it to pick up the pipe to be moved. The machine has an electrical control panel and a terminal for setting operating parameters and programming work characteristics. Both lines are controlled by a single operator, who checks the correct machine operation. Figure 4.5 visualizes the main processes of the Sica lines.
4.2 MATERIAL
M&G uses polypropylene (PP) pellets to form and shape hollow pipes in different sizes and lengths. Polypropylene is a thermoplastic that offers a combination of outstanding physical, chemical, mechanical, thermal and electrical properties. Compared to low or high density polyethylene, it has a lower impact strength, but superior working temperature and tensile strength.
The quality of extruded pipes is an essential aspect for further processing. First of all pipes must meet customer requirements, e.g. no striping or irregularities. Furthermore the pipes should not be curved, since this can cause problems entering the cutter at the Sica line. If the quality does not meet the specifications pipes are rejected and considered as scrap. It must be noted that there are many more problems as described in the books of Extruding plastics: a practical processing handbook (1998) by Rosata and Extrusion: the definitive processing guide and handbook (2005) by Giles et al..
4.2.1 PRODUCT SPECIFICATIONS
Extrusion. The extruder processes hollow pipes with a standard length of 4315 mm. In addition to
this, some products are directly processed to customer demand. Table 4.1 creates an insight in the lengths, diameters and different colors that are processed.
Sica. The two Sica lines (table 4.1) are used for different shaping purposes. Sica 2 is more versatile
concerning shapes, while Sica 1 is more versatile when it comes to the diameters to be processed. Both lines are scheduled to run for approximately 16 hours/day, while the extrusion line is scheduled to run 24 hours/day.
21 Extrusion Sica 1,2 Standard length Other lengths Standard diamater
Bought Colors Diameter Machine Shapes
4315mm 692 mm 60mm Ø 70mm Ø Transparent Sica 1 – normal, QF
663 mm 80mm Ø 130mm Ø White Sica 2 - normal, QF, safe PP
Other 100mm Ø 150mm Ø Grey 70 Ø Sica 1 normal, QF
Black Sica 1 – normal, QF
Sica 2 – normal, QF Sica 1 – normal, QF Sica 2 – normal, QF 130 Ø Sica 1 normal, QF 150 Ø Sica 1 normal, QF 60 Ø Sica 1, Sica 2 80 Ø Sica 1, Sica 2 100 Ø Sica 1, Sica 2 4.3 METHODS
This paragraph is about (standard) procedures that are carried out and are influential concerning waste. In this paragraph the maintenance policy and planning are discussed.
4.3.1 MAINTENANCE
Despite the interdependent relationship between the production scheduling and the maintenance planning, the two activities are planned and executed separately within M&G. For many years the relationship between production and maintenance has been considered as a conflict in management decision. The conflicts may result in an unsatisfied demand or machine breakdowns if the production and maintenance services do not respect the requirements of each other (Berrichi et al., 2009). The maintenance and production services must collaborate to achieve a common goal, that of maximizing system productivity. Therefore, both objectives of maintenance and production must be considered with the same importance level. Hence, a solution of the joint production and maintenance problem must be a trade-off between the objectives of the two services.
Machine breakdown is one of the most important issues that concerns operators on the shop floor. The reliability of equipment on the shop floor is very important because if one machine breaks down the entire production line stops. An important tool that is necessary to account for sudden machine breakdowns is Total Productive Maintenance (TPM).
There are three main components of a TPM program: preventive maintenance, corrective maintenance, and maintenance prevention. Preventive maintenance has to do with regular planned maintenance on all equipment rather than random check ups. Workers have to carry out regular equipment maintenance to detect any anomalies as they occur. By doing so sudden machine breakdowns can be prevented, which leads to improvement in the throughput of the machines and a reduction of waste (Feld, 2001). Corrective maintenance deals with decisions such as whether to fix or buy new equipment. If machine components regularly breakdown it might be better to replace those parts with newer ones. Maintenance prevention has to do with buying the right machine/equipment. If a machine is hard to maintain (e.g., hard to lubricate) then workers will be reluctant to maintain the machine on a regular basis.
Currently, M&G applies a corrective maintenance policy. In paragraph 8.3.2.1 the situation is described in more detail. M&G aims for preventive maintenance but it is not yet carried out due to incorrect planning and lack of production time.
22 4.3.2 PLANNING
Within M&G planning falls under the responsibility of the planning- and logistics office. In this paragraph the main activities of planning are described, focusing on plastic processing.
Planning entails a series of actions that engage every aspect of a firm’s activities. Basic information is assembled and tracked from its earliest stages and applied to a process by which future performance within all areas of the company’s operations may best be anticipated, designed, and implemented. The essential ingredient in the planning process is information, and the essential result is preparation. In particular, planning is the focal point of human and material resources management (Moynihan et al., 2002).
M&G works with a MRP system named BMPro, which is internally programmed in an MS-DOS environment. At the moment M&G is implementing SAP to optimize its information flow and planning system. M&G’s main focus regarding planning is to produce on order. Customers place orders on a daily base which are handled by sales. The last couple of years an approximated number of 12.000 customer orders per year were processed. Only a small percentage (10%) of these orders are produced on stock, which are either semi-finished or end products. M&G works with a determined stock minimum, basically meaning that whenever stock level drops below the pre-determined level a stock order is placed for supplementation. On this basis BMPro generates production advices which are controlled and verified by planning- and logistics.
Every Wednesday the preliminary capacity planning is discussed between planning, logistics and production to find out whether it is achievable followed by a definite planning for the upcoming week. Pre-determined stock levels differ between products. When stock levels fall below the minimum a new order is placed within two weeks, while the current stock level is used as buffer. For extrusion planning is of great importance due to changeover times. Changing between colors and diameter is a timely business and generates waste, due to the fact that the machine cannot be shut down. Changeovers are unavoidable for M&G, but improvements should be sought. This is discussed in chapter 8.3.2.2.
Planning will not be extensively researched, due to the current introduction of SAP. It is mentioned to acknowledge the fact that it is an important aspect concerning waste.
4.4 MANPOWER
Both extrusion and Sica lines run from Monday to Friday based on respectively three and two 8 hour shifts per day. For each shift there are in total four operators, one for the extrusion line, one group leader and two operators for both Sica lines. In the table below a short task description is given.
Workplace Short description
Operator extruder
Operating the extruder, checking the quality, solving small interferences, converting machinery to other jigs, accomplish color changes, measuring wall thickness and packaging and removal of finished goods.
Operator Sica
Operating the Sica machine, checking the quality, solving small interferences, converting the machine to other jigs and packaging and removal of finished goods.
Group leader Able to perform changeovers, run overall production, instruct operators, paperwork.
23 Skills and qualifications are important topics in literature. Skill enhancement is becoming the central focus of labor market concerns. The existence of a certain level of skills makes those forms of work organizations possible that are necessary for enhanced competition on the global marketplace. For M&G the workforce is an increasingly important source of competitive advantage. It is important to build a workforce that has the ability to achieve competitive success and that cannot be readily duplicated by others. The recent trend towards using temporary help and part-time employees is noticeable within M&G and using these people in core activities might have a negative impact on productivity. At the most fundamental level, it is obvious that, if all employees are temps they cannot serve as a base for distinction. If people have no attachment to the firm the competitive position of the organization is diminished. This is why many well-managed professional firms emphasize recruitment, selection, and building strong cultures to retain the skilled employees who constitute the basis for their success (Pfeffer, 1995).
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5.
DIAGNOSES - VALUE STREAM MAPPING
As explained in the theoretical framework value stream mapping is a lean tool used to analyze the flow of materials and information required to bring a product to a consumer. In combination with the 7 wastes described by Ohno this chapter reveals which of the waste(s) have the highest influence (concerning costs) on the system based on the listed research requirements. First a concise explanation of the VSM is given followed by a brief description of each of the seven wastes. The visual representation of the VSM is given in figure 5.2. The values of the VSM are averages for one arbitrary pipe through the system. The chapter provides an answer to the following sub-question: “Which type(s) of waste is most suitable for improvement?”
5.1 VSM EXPLANATION
For extrusion material is processed continuously through a series of machines from raw material to final product. It flows in a continuous stream from one machine to the next, without periods of stopping and waiting in between. Hence, the lean ideal of flow occurs by default. Also, there is typically little or no Work in Progress (WIP) between machines.
The buffer in between both lines due to the hardening process makes it unfeasible to place both manufacturing lines next to each other in such a way that after extrusion the pipe is belled instantaneously. Therefore the whole process from raw material to final product should be considered as discrete manufacturing. The buffer in between both processes can be considered as a decoupling point. The decoupling point is the point in the material flow stream where the customer’s orders penetrate. It is here where order-driven and forecast driven activities meet (Hoekstra and Romme, 1992). The extrusion process is considered as a forecast driven activity while the Sica process is an order-driven activity. The decoupling point is also the point at which strategic stock is often held as a buffer between product variety and smooth production output, which is necessary because of the hardening process of extrusion pipes.
In order to better understand the VSM a brief explanation is given. Customers (mainly OEM’s) place orders on a daily base. Based on the amount of orders, M&G forecasts the amount of plastic pellets needed for production and places orders to its supplier. Once the material is supplied to M&G it is placed in stock ready to be extruded at the extrusion line. For extrusion production is pushed based on predetermined stock levels. Once pellets are processed at the line, the following process (hardening) takes place in order to get the appropriate product quality. Then extrusion pipes are pushed from stock based on customer demand to Sica 1,2. Once extrusion pipes are processed at one of the Sica lines they are either packaged or required for further processing. All processes behind the Sica lines fall outside of the research boundary.
5.2 LEAN 7 WASTES
Overproduction. Producing more, earlier or sooner than next workstation demands results in larger
25 Waiting. Whenever goods are not moving or being processed, the waste of waiting occurs. Much of a
product’s lead time is tied up in waiting for the next operation; this is usually because material flow is poor, production runs are too long, and distances between work centers are too great. Goldratt (1984) has stated many times that one hour lost in a bottleneck process is one hour lost to the entire factory’s output, which can never be recovered. Linking processes together so that one feeds directly into the next can dramatically reduce waiting, but this is impossible due to the hardening process and thus in this case waiting time is unavoidable.
Transport. This refers to transportation within Work-In-Process (WIP) and often occurs because of
reasons like weak plant layout and lack of understanding of production or process flow. Transporting products between processes is a cost incursion which adds no value to the product. Excessive movement and handling cause damage and are an opportunity for quality to deteriorate. Transport is an important aspect considering waste and too much time is involved, but direct gains without high investments are not realizable.
Inappropriate processing. Often termed as “using a sledgehammer to crack a nut,” many
organizations use expensive high precision equipment where simpler tools would be sufficient. This often results in poor plant layout because preceding or subsequent operations are located far apart. In addition they encourage high asset utilization (overproduction with minimal changeovers) in order to recover the high cost of this equipment. There are signs of inappropriate processing caused by deterioration of the extruder (e.g. a worn screw). Replacing or altering these parts involves high investments and direct gains are not measurable.
Unnecessary inventory. Work in Progress (WIP) is a direct result of overproduction and waiting.
Excess inventory tends to hide problems on the plant floor, which must be identified and resolved in order to improve operating performance. Excess inventory increases lead times, consumes productive floor space, delays the identification of problems, and inhibits communication. In order to improve excess inventory, processes and planning need to be streamlined first. M&G is currently implementing SAP to improve its planning and streamline its processes.
Unnecessary movements. This waste is related to ergonomics and is seen in all instances of bending,
stretching, walking, lifting, and reaching. These are also health and safety issues, which in today’s litigious society are becoming more of a problem for organizations. Jobs with excessive motion should be analyzed and redesigned for improvement with the involvement of plant personnel. Nearly every company is subject to unnecessary movements, so is M&G. An example is the moving of heavy extrusion pipes from line to line. For now, this is considered as a waste that has no direct influence on the increasing costs for M&G.
Defects. Defects are direct costs and are thus judged as a serious opportunity for Kaizen
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5.3 CONCLUSION
Now that the seven wastes are briefly described it is important to set a final research boundary. Improving all seven wastes is unfeasible due to the limited time available for research. Given that there is a strong tendency within M&G towards cost reductions and the fact that defects are direct costs that seize for immediate Kaizen action the choice is made to focus on defects and thus scrap reduction of plastic. Under the current circumstances of M&G (appendix 4), process improvements without major investments have priority (research limitation). Instead of visualizing a time table the VSM visualizes the production output with scrap percentages per line and other important aspects concerning scrap such as changeover time and unplanned maintenance. In paragraph 8.6 a future state VSM is given.
Now that the final research boundary is set (figure 5.1), the amount of scrap needs to be mapped and the problem must be verified, which is discussed in the following chapter.
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6.
DIAGNOSES - PROBLEM VERIFICATION
In this chapter three methods for verification of the problem are discussed. At first a questionnaire was used to map the current activity of M&G concerning scrap reduction. Secondly a calculation of the current scrap for extrusion and Sica 1,2 is given followed by the introduction of a zero measurement to measure the amount of scrap (figure 6.1). It provides an answer to sub-question 4: “How much waste is currently created per machine/line?”
6.1 QUESTIONNAIRE
A questionnaire was used to investigate the activity of M&G concerning scrap reduction (appendix 5). The results of the questionnaire can be found in appendix 6. The questionnaire was sent to 16 employees with a return rate of 80%. The questioned employees varied from work floor operators to management. It is important to focus on employees with differing views towards the problem. The following results are gathered.
Despite the fact that that M&G is modifying its processes to reduce scrap there are no clear metrics to identify and monitor it. There is barely any information available about the amount of scrap generated. It is interesting to see that almost everyone acknowledges that scrap is an important issue for M&G and agrees upon the fact that there are high costs involved. It is said that changes are being carried out, but this contradicts with the negative response on whether all processes have been studied and improvements are made.
From the questionnaire it can be concluded that M&G is under the impression that they have progressed rather well on scrap reduction, but since there is an agreement upon the fact that not all sources of scrap have been identified and the fact that scrap is not clearly monitored M&G is placed in between ‘we plan to reduce scrap’ and ‘we have identified our scrap and are monitoring it’. In the following paragraph the actual scrap levels are calculated.
Figure 6.2 – Scrap classification
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6.2 SCRAP CALCULATION
Now that important stakeholders have acknowledged that scrap is an actual problem for M&G it is important to measure/calculate the amount of scrap. At first a calculation will reveal what the percentage of scrap is in the current situation.
6.2.1 EXTRUSION LINE
For the extrusion line there are no clear data about the amount of generated scrap. The extrusion line basically generates two types of scrap. First of all pipe lengths (rejected pipes due to damages or other causes) and melt (caused by machine breakdown or failure). In order to find out what the amount of scrap is a zero-measurement is carried out (paragraph 6.3).
6.2.2 SICA LINE
Because of the standard length of 4315mm for an extrusion pipe and the fact that pipes are cut in all ranges of lengths, scrap is being generated. In table 6.1 a calculation of the loss in the current situation is given based on 35 products that cause 80% (appendix 7) of the total production in 2008 (data from 2009 is inappropriate due to unstable production caused by the economic crisis).
The average percentage of scrap for Sica 1 and 2 is 8,53% and this accounts for a loss of 69.034 meter of material scrap, 29.814 kilograms and total costs of €47.703 (table 6.1). The material costs are calculated by an average price of € 1,60/kg.
As explained both Sica lines cut and bell pipes based on customer demand. In appendix 8 the production numbers over 2008 are given (in meters). Dividing this by the standard pipe size of 4315mm gives the total number of extrusion pipes needed for processing. For every pipe 61mm is lost in order to cut straight, thus 4254mm remains. With this net length the number of cuts can be calculated dividing it by the length of the pipe to be processed. Taking article number 97294 as an example the number of pipes cut from one extrusion pipe is 6,42, basically meaning 0,42 pipe length is lost representing 276mm + 61mm = 337mm of scrap. For this particular article number this accounts for a scrap percentage of 7,81%. Since there were 21.794 extrusion pipes needed for this particular article number the total loss is 337mm * 21.794 pipes and accounts for 7.344 meter, 2.938 kg and € 4.700 on a yearly base.
6.3 ZERO MEASUREMENT
Once it became clear that scrap is not properly monitored, lists were created to measure the amount of scrap in kg per line. It was important to gain trust from the operators to be able to conduct the measurement. The following graph shows the results over a period of approximately three weeks ranging from the 25th of May to the 13th of June. Over this period a total of 4.154 kg with a value of € 6.646 of scrap was created, underpinning the fact that there are high costs involved (figure 6.2). In appendix 9 more detailed results of the measurements can be found, including the created lists.
Product Average waste(%) Material waste (m) Material waste (kg) Material costs (€)
80% of total production 8,53% 69.034 29.814 € 47.703
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6.4 SCRAP DISPOSAL
In addition to the earlier discussed methods to formalize the problem the scrap disposal costs are researched. In the current situation all (plastic) scrap (mixed) is dumped into a container which is rent from Leo Reitsma B.V. who also takes care of disposal. The following two graphs reveal how much money is spent over January-February-March 2010. M&G pays €0,11/kg for disposal and an additional €164 for container rental. This accounts for approximately €30.000 per year. For January, February, and March the costs are depicted in figure 6.4. In appendix 10 more detailed information can be found.
6.5 TOTAL SCRAP
Since there are no clear data available about the costs of scrap an estimation is given excluding additional costs such as operator salaries, depreciation, and machine hour tariffs. The total amount of scrap generated is solely based on the zero-measurement and accounts for 38.752 kg of scrap for the extrusion line and 27.712 kg for both Sica lines. An estimated amount of 66.464 kg of scrap was generated over 2008 (based on 48 weeks) based on a total production of approximately 352.000 kg, which accounts for 18,88% of scrap. The total costs for material scrap plus disposal are € 136.342 (table 6.2).
Total scrap Total production Percentage of scrap Total costs scrap
66.464kg 352.000kg 18,88% € 136.342
Figure 6.3 – 0-measurement
Figure 6.4 – Scrap disposal costs
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7.
DIAGNOSES - OVERALL EQUIPMENT EFFECTIVENESS
Now that the problem is formalized it is important to uncover the sources of scrap. In order to do so an OEE analysis is carried out. As explained in the theoretical framework the OEE is a function of availability, performance and quality and gives an indication of how effective a process is (The Fast Guide to OEE).4 This chapter provides an answer to the following sub-question: “What are the sources of the generated waste(s)?”
7.1 INTRODUCTION
The OEE analysis starts with plant operating time; the amount of time a facility is open and available for equipment operation. From plant operating time, a category of time called planned downtime is subtracted, which includes all events that should be excluded from efficiency analysis because there is no intention for running production (e.g. breaks, lunch, scheduled maintenance, or periods where there is nothing to produce. The remaining time available is the planned production time. OEE begins with Planned Production Time and scrutinizes efficiency and productivity losses that occur, with the goal to reduce or eliminate these losses. There are three general categories of loss to consider – Down Time Loss, Speed Loss and Quality Loss.
Availability. Availability takes into account Down Time Loss, which includes any events that stop
planned production for an appreciable length of time. Examples include equipments failures, material shortages, and changeover times. While it may not be possible to eliminate changeover times, in most cases it can be reduced.
Performance. Performance takes into account Speed Loss, which includes any factors that cause the
process to operate at less than the maximum possible speed when running. Examples include machine wear, substandard materials, misfeeds, and operator inefficiency. The remaining time is called Net Operating Time.
Quality. Quality takes into account Quality Loss, which accounts for produced pieces that do not
meet quality standards, including pieces that require rework. The remaining time is called Valuable Time. This is what should be maximized.
7.2 AVAILABILITY
The availability portion of the OEE Metric represents the percentage of scheduled time that the operation is available to operate. The Availability metric is a pure measurement of uptime that is designed to exclude the effects of Quality, Performance, and Scheduled downtime events.
Extrusion. Figure 7.1 represents the down time loss over a period of 52 days. The total productive
time lost due to setup and adjustments was 147,8 hours and the loss due to breakdowns was 100,2 hours, which account for 4,77 hours/day. In total this represents an availability rate of 80,2% based on 24 hours of scheduled time (appendix 16 for more information).
Sica. The down time losses for Sica 1 and 2 were respectively 99,5 and 108,8 hours for setup and
adjustments and 69,0 and 44,5 hours for breakdowns (figure 7.1). The average scheduled time for both Sica lines is 16 hours per day thus the availability rates are 79,8% and 81,6% (figure 7.2) (appendix 11 for formulas).
4
32 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Extrusion Sica 1 Sica 2
Setup and Adjustments 147,8 99,5 108,8
Breakdowns 100,2 69,0 44,5
Percentage
Down time loss
Setup and Adjustments Breakdowns 78,5% 79,0% 79,5% 80,0% 80,5% 81,0% 81,5% 82,0% Availability Extrusion Sica 1 Sica 2
Now that the availability percentages are known the question remains what the root causes for availability losses are. In the following subparagraph these root causes are discussed for respectively the extrusion line and Sica lines.
7.2.1 ROOT CAUSES EXTRUSION
Breakdowns. The extrusion line is subject to a number of breakdowns (figure 7.3). The most common
breakdowns are calcification of the calibration tube and machine interruptions such as the spray cooler bath (cool water machine). Calcification of the calibration tube leads to product striping and thus rejected extrusion pipes and is caused by improper water conditions. More information about breakdowns is given in paragraph 8.3. One of the main reasons for machine failure is the use of corrective maintenance instead of preventive and/or predictive maintenance. The relation between breakdowns and scrap is that the extrusion line is a continuous process that normally is not switched off. Whenever a breakdown occurs the line is set to approximately 15% of its maximum capacity, which is about 30 kg/hr. 0,00 5,00 10,00 15,00 20,00 25,00 Breakdowns Other Jams Saw jam Compressor Puller Vaccuum pump Vaccuum calibrator Coolwater machine Calibration unit
Figure 7.1 – Down time loss Figure 7.2 – Availability percentage
