Coping with an increasing demand for guiding catheters at PendraCare
Master Thesis
Author: Marnick Boerland Student ID: 1453297
Date: 13-12-2010 Address: Turftorenstraat 27
9712 BM Groningen
Email: m.boerland@student.rug.nl
University: University of Groningen Faculty: Economics and Business Study: Technology Management
1st Supervisor: Prof. dr. ir. J. Slomp 2nd Supervisor: Dr. J.A.C. Bokhorst
Company: Pendracare Department: Operations Supervisor: E. Krikke
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Abstract
This research diagnosed the assembly process of the guiding catheter at Pendracare. The guiding catheter is available in four different French sizes which are currently all assembled on the same line.
The current assembly process has been designed without careful research, due to time and financial constraints. This has led to an inefficient assembly process which is not able to deliver the amounts, as desired by the customers, on time. This paper discusses several possibilities for increasing the possible output, each having certain advantages and disadvantages. These possibilities have been summed up in a decision tree, thereby generating different possible routes that Pendracare could follow to gradually increase the output. This decision tree discusses the output varying from one assembly line to three in order to increase the output. No matter how many lines are implemented there were two options discussed for increasing the output per line. The first is placing ablated bodies on stock in a supermarket to provide the assembly process with catheters and the second is installing a second laser. For both these options the ideal layout and work distribution have also been determined.
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Preface
The last five months I have spent a lot of time and effort writing this final thesis for my master Technology Management at Pendracare in Leek. Due to the dynamic environment it proved to be an interesting time that I am glad to have experienced.
I would like to start by thanking everybody at Pendracare for their support and inspiration during this research. The willingness of everybody to cooperate made it much easier to gather the required information. I am very pleased I was able to write my final thesis here. A special word of thanks goes out to Erik Krikke my supervisor at Pendracare for guiding me through this thesis and sharing his knowledge and experience with me.
Another word of thanks goes to prof. dr. ir. J. Slomp my supervisor of the University of Groningen.
Prof. dr. ir. J. Slomp always gave me valuable feedback that allowed me to change my perspective on this research whenever this was needed. In addition he was the person who brought me in contact with Pendracare. I would also like to thank dr. J. A. C. Bokhorst for taking the time to read and judge my thesis.
This master thesis marks the end of my study Technology Management at the university of Groningen, which started over six years ago. It has been a period to which I look back with great pleasure and pride. It helped form me into the person that I am today and enriched my live with a lot of knowledge and experiences. I hope that the period ahead of me will continue to help me grow as a person and lead to more defining moments.
I hope you enjoy reading this thesis as much as I have enjoyed writing it, Marnick Boerland
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Management Summary
Assembly of the guiding catheter is currently performed on one line that goes through three different departments. In 2011 the α guiding catheter will be introduced on the market for medical devices, it will be available in four different sizes. As there is currently only one assembly line, all four catheter sizes will be assembled on the same line.
The marketing and sales department have come up with a sales forecast for the two coming years, 2011 and 2012, this will be respectively 45.000 and 300.000. The common believe within Pendracare is that the current assembly process, which has a very inefficient design is not able to cope with the quantities as forecasted. After an analysis of the current assembly process this turned out to be true, utilizing the full capacity will only imply a maximum output of 20.700 guiding catheters. This is for a yield of 100% which will probably not be reached. Therefore measures for increasing the output have been discussed during this research. Leading to the following research question: What measures could be taken in order to cope with an increasing demand for 5F, 6F, 7F and 8F guiding catheters?
After constructing a current state VSM and a spaghetti diagram the main cause for the low output level has been determined. When the guiding catheter enters the assembly process at the assembly cell located in the clean room, it undergoes three laser processes, ablation, annealing and cutting.
Where ablation and cutting are done on the same machine. This implies changing over the machine every time when shifting between processes and when a catheter is being cut no body can be ablated, this also goes the other way around. On the one hand this causes starving of machines and on the other hand this causes high WIP levels. This phenomenon is called re-entrant flow.
Three different scenarios were drawn up for coping with the increased sales volume the next few years. The first scenario was keeping assembly on one line, scenario two was adding one line to the assembly process and scenario three was adding two lines to the assembly process. For each scenario options for increasing the output have been suggested. The options that have been suggested for increasing the output per line are: increasing the number of assembly shifts; adding a supermarket to the assembly organization and adding a third laser to the assembly process, these last two have been suggested to get around the re-entrant flow.
For the scenarios that dealt with two or more lines, the option of installing one or more high volume lines has also been discussed, where the other line would remain a mixed model line. The advantage of installing high volume lines is that these lines are not faced with changeovers for different French sizes. This leads to more net available production time and higher output levels than for mixed model lines. To maintain a high level of flexibility the lines are on a planning level high volume lines, whereas on an organizational level they are not. Meaning they are used solely for 6F assembly, however they do have the settings to cope with the other three French sizes. When demand turns out to be much different than forecasted these dedicated lines could also be used for other French sizes.
The two measures for dealing with the re-entrant flow problem are the supermarket and an extra laser. The problem with re-entrant flow is not only a significant lower output level, but it also requires batch production which causes high WIP levels, but more importantly quality issues and thereby a low yield. A supermarket is buffer which is filled with in this cases ablated catheter bodies, during the dayshift operators could pick the bodies from this supermarket. During an additional second shift the supermarket should be restocked with the number of bodies that have been taken
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from it. The advantage of this is that during the dayshift the ablation/cutting laser only needs to be set for cutting. Thereby making room for one-piece flow and a significant increase in the yield. The output in this option is higher compared to the current situation, due to less quality issues occurring not to a higher capacity. The option of adding a laser does imply a significant increase in the capacity of the assembly process, because each laser now only performs one operation. This also has a consequence that one-piece flow is possible, resulting in less quality issues. The increase in capacity gives this option a higher level of flexibility and reliability compared to the supermarket. However in terms of assembly costs the supermarket scores better. This option requires one additional operator to fill the supermarket whereas purchasing a whole new laser requires an investment of € 100.000,-.
The calculations for all three scenarios combined have led to a decision tree, showing different possible routes for gradually increasing the output of the assembly process.
For both options for increasing the output, a supermarket in the assembly process and an extra laser, a layout has been constructed. In both layouts the tooling has been rearranged in such a manner that every process is placed after the previous process in the routing. When changing this routing the number of assembly departments could be brought back from two to three. Leading to two new possible assembly layouts, one with a supermarket and one with an extra laser. These four layouts and their affect on the assembly process are given in the following table:
During observation of the assembly process it became apparent that the cycle time of the cutting to length process done by the laser could be reduced. The cycle time was set to long. This would lead to a significant increase in the output. After discussing this with process engineers it came to light that the cutting process might be sped up even more by increasing the power of the laser. The same goes for the ablation process. The exact cycle time could not be given, however it is said that this would lead to a considerable decrease. Since the exact cycle time is unknown the effect it has on the output levels could not be given. Therefore graphs have been constructed showing all possible cycle time reductions and their effect on the output. These graphs can be found in section 6 of this research.
The last section of this research discusses the implementation of a kanban system into the assembly process. When placing a buffer after every production department the downstream process could take bodies from this buffer, this will act as a signal for the downstream process. This will take away the work orders from the assembly process and pulls the catheters through the assembly process.
High volume products could be put on end stock, picking catheters from this end stock will act as a signal to commence production. For the low volume products it is not feasible to put them on end stock, therefore a work order is still required. This should only be sent to the shaping department, the other departments will know what to assemble, when they see which bodies are taken from the buffer.
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Table of contents
Abstract ... 1
Preface ... 2
Management Summary ... 3
Table of contents ... 5
1. Introduction ... 6
2. Research design ... 9
2.1 Problem context ... 9
2.2 Research goal ... 11
2.3 Research question ... 11
2.4 Conceptual model ... 12
2.5 Methodology ... 15
2.6 Report Layout ... 16
3. Current state ... 17
3.1 The guiding catheter ... 17
3.2 Customer orders ... 18
3.3 Assembly process ... 19
3.4 Inspection ... 20
3.5 Value stream map ... 21
3.6 Layout ... 24
4. Scenarios for future assembly ... 27
4.1 Takt time ... 27
4.2 Current situation ... 30
4.3 Scenario 1: A mixed model assembly line ... 32
4.4 Scenario 2: Two assembly lines ... 36
4.5 Scenario 3: Three assembly Lines ... 38
4.6 S.M.E.D. ... 42
4.7 Poka Yoke ... 42
5. Layout design... 44
5.1 Lean assembly ... 44
5.2 U-shaped line ... 46
5.4 Line balancing ... 51
5.5 Assembly routing ... 54
6. Cycle time reduction ... 58
6.1 Laser cutting settings ... 58
6.2 Increasing power ... 60
7. Planning & Control ... 63
7.1 Current situation ... 63
7.2 Push vs. Pull ... 64
7.3 Kanban ... 65
Conclusion ... 68
Recommendations ... 71
References ... 74
Appendix... 75
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1. Introduction
This report gives the results of a research into the performance of the guiding catheter assembly process at Pendracare based in Leek, this research concludes the Master Technology Management at the University of Groningen. This thesis begins with a discussion of the general characteristics of Pendracare.
Organization
Pendracare is a relatively young organization that has been rapidly expanding ever since it was established in 2004. It is based in Leek, Groningen, and develops and manufactures different types of catheters. It is a relatively small organisation, that currently employs around one hundred people.
Pendracare is a privately owned company that is divided into two divisions, as could be seen in figure 1, Pendracare Vascular and Pendracare International. Both divisions are based in the same building in Leek. Pendracare Vascular provides contract development for external partners and Pendracare International develops, manufactures and distributes Pendracare branded products through an internationally oriented distribution network, the research that has been conducted during this internship was carried out at Pendracare International.
Figure 1: Pendracare divisions
For Pendracare customer involvement throughout the entire design and manufacturing process is very important. Their mission statement is:
When designing these catheter concepts and interventional devices customer needs and patient safety are the most important factors. This strategy can be classified as ‘customer intimacy’, according to Treacy and Wiersema (1993). The total organizational structure, covering both Pendracare Vascular and Pendracare International, is composed of the following departments:
Pendracare
Pendracare Vascular
• Contract development
Pendracare International
• Diagnostic catheter
• Guiding catheter
“We want to be the partner of choice for Medical companies and Medical specialists for the development, manufacturing and marketing of truly innovative catheter
concepts and interventional devices for use in the blood circulation.”
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Chief Executive Officer
Research & Development Operations Administrative
assistance Sales & Marketing
Finance
Quality Assurance &
Regulatory Affairs
Figure 2: Organizational structure of Pendracare
Industry
The catheters Pendracare produces are sold worldwide, the largest part of their customers are distributors who buy the catheters and sell them to medical institutes, either under their own brand name or under the Pendracare brand. Pendracare also delivers, in some cases, directly to hospitals, an example of this is ‘Nij Smellinghe’, a hospital located in Drachten (Friesland).
An important characteristic of the medical devises industry is the large role legislation plays.
Pendracare designs, develops and manufactures devises that are used for circulatory diseases management, which means these devices are inserted into the human body. The government defines catheters as medical devises and therefore they are under strict standards and regulations. For this reason the department ‘Quality Assurance and Regulatory Affairs’ plays an important role within Pendracare.
Products
A catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, injection of fluids, or access for surgical instruments. The process of inserting a catheter is called catheterization.
Pendracare International is currently producing two types of catheters, these two types are the diagnostic catheter and the guiding catheter, this research was focussed on the production of the guiding catheter. The diagnostic catheter is used to display the vascular system for diagnostic purposes. The catheter is inserted into a blood vessel and then brought to the target vessel over a guide wire. Once the diagnostic catheter has reached the desired location, a contrast fluid is injected into it to enable the vascular system to be X-rayed.
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The guiding catheter has been designed to help physicians guide their sophisticated tools to the desired location. Once it has been inserted into a specific vessel, physicians could use it to pass through a variety of their instruments and into the vessel. The most commonly used instruments to be inserted into the guiding catheter are guide wires and balloon catheters.
Pendracare Vascular designs and develops balloon catheters on a contract basis for external partners, they are used to widen narrowed vessels. By injecting radiocontrast agent through a tiny passage extending down the balloon catheter and into the balloon, the balloon is progressively expanded. As much hydraulic brute force is then applied as judged needed to be effective to make the narrowing in the vessel widen. Once the vessel has widened enough the balloon will be removed.
Besides the balloon catheter, there are several other devices that can be inserted into the vessels through a guiding catheter. Some examples of this are laser catheters, IVUS catheters, Doppler catheters, pressure or temperature measurement catheters and stents. Stents, which are expandable stainless steel mesh tubes that are mounted on a balloon catheter, are the most commonly used devices, next to the balloon catheter.
Clean room
Because catheters are inserted into the human body through the blood vessels they need to be as sterile as they could possibly be. That is why both the guiding and the diagnostic catheter are produced in an ISO class 8 (ISO 14644-1) ‘cleanroom’, this is a controlled environment that has a low level of environmental pollutants such as dust, airborne microbes, aerosol particles and chemical vapours. A cleanroom has a controlled level of contamination that is specified by the number of particles per cubic meter at a specified particle size. The exact guidelines for this type of cleanroom are:
• Maximum of 3,520,000 particles bigger or equal to 0.5 µm per m3 air
• Maximum of 832,000 particles bigger or equal to 1 µm per m3 air
• Maximum of 29,300 particles bigger or equal to 5 µm per m3 air
Cleanrooms are spaces with overpressure, which means that while upon entering the room no
‘polluted’ air from outside the cleanroom could enter it. These production spaces are separated from other areas through a lock chamber. In these lock chambers the pressure is lower than in the cleanrooms, but higher than in other adjacent areas, which also stops ‘polluted’ air from entering.
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2. Research design
This section of the paper discusses in what manner this research has been designed. Through the elaboration of the problem context, a conceptual model, the research goal and the accompanying research questions that have been formulated. This section is ended with an explanation of the scope and a brief description of the layout of this research.
2.1 Problem context
Pendracare recently started a project that aims at reducing the throughput time for its diagnostic catheter, which currently is 6-8 weeks, they set their goal at reducing this to two weeks. From the value stream map (VSM) that has been constructed for the diagnostic catheter several points of attention were identified. A value stream map displays all the actions (both value added and non- value added) currently required to bring a product through the main flows essential to every product: (1.) the production flow from raw material into the arms of the customer and (2.) the design flow from concept to launch (Rother & Shook, 2003). This value stream map can be found in appendix A.1. Two large projects were initiated based on this VSM. The first one was decreasing the throughput time of the diagnostic catheter production process and the second one was speeding up the logistical process, which mainly means reducing order processing- and transportation time.
Pendracare wants to tackle these projects using the principles of lean manufacturing.
However the research as conducted during the internship at Pendracare does not focus on the production of the diagnostic catheter, it focuses on that of the guiding catheter. As discussed in the previous section the production of the guiding catheter is currently in the start-up face, the first orders are coming in. During production of these first few orders it became clear that the current assembly process is far from efficient, because the optimal layout of the assembly line has not jet been discovered. This results in production with a lot of wastes, leading to high production costs, low margins and high throughput time, which is not a desired situation, especially not in these times of low demand.
The last few years producing with waste was not a major issue, demand for catheters kept on rising and the major challenge Pendracare was facing was making sure orders were delivered on time, within the promised 6-8 weeks. Pendracare being a young organization was not used to this high demand and the pressure on production resulting from this. Because of this, throughput time was the most important performance indicator production was judged upon and all attention was given to this. A logical consequence from this was that there was not much time and capacity left to pay attention to efficiency improvements.
However recently times have changed, making sure orders are finished and delivered on time is still a very important performance indicator, but not the only one anymore. The catheter market is highly uncertain, fluctuations in demand are very common. Pendracare has experienced this for themselves with the diagnostic catheter. Where the last few years they were facing difficulties with finishing orders on time, demand is now considerably lower resulting in overcapacity. Because of this decline in demand profit has decreased, therefore, next to the throughput time, efficiency has become a very important performance indicator as well. The necessity sprung to start paying more attention to improving the performance of the production process, in order to minimise production costs and throughput time. This goes not only for the production of the diagnostic catheter but also for the guiding catheter. The Pendracare management team decided to implement lean manufacturing into
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the organisation and especially in the production areas as a means of reaching this goal of minimizing both production costs and throughput time. The β guiding catheter has not been produced for a very long period and this started very quickly after product development was finished, this decision was made because Pendracare needs the money that they believe the guiding catheter will generate, in order to ensure their continuity in the near future. Because of these time and financial constraints there has not been a lot of research into the optimal layout of this production line and especially the assembly line. This is the reason why the assembly line is currently operating far from efficient. The management of Pendracare believes that implementing the principles of lean manufacturing into the assembly process layout of the β guiding catheter will result in less waste and therefore in a better operational performance.
As mentioned before the guiding catheter is currently produced in batches. An order is divided into batches of around 25 catheters and these catheters are not transferred to the next production station until the entire batch has finished that specific production step. This results in a lot of work in process (WIP) in the production line, meaning that during production there are a lot of catheters that are somewhere in the production line, but not undergoing any production step at that particular moment. The problem situation as encountered at Pendracare can be summed up in the following problem description:
The α guiding catheter which is currently in development will be, unlike the β, produced in different French sizes. The four different French sizes that will be produced are the 5F, 6F, 7F and 8F. The α is considered to be the successor of the β, therefore production of this type will stop once development of the α has been finished. This catheter type will be available on the market from 2011. Therefore the marketing and sales department has constructed a sales forecast for 2011 and 2012 for the α guiding catheter. The forecast shows a significant increase in the demand for guiding catheters. It is believed within Pendracare that with the capacity of the current assembly process it is not possible to deliver the forecasted quantities.
The α guiding catheter will be assembled on the same line as the β. Problems are thus foreseen with delivering the required quantities for meeting the forecasted demand, as the assembly process as it is currently designed is not considered to be able to cope with these high volumes. However there is no data to backup this hypothesis and possible options to increase the output and what their effect will be are unknown. This has lead to an additional problem:
Due to a lack of time the guiding catheter production started quickly after product development was finished, because of this there has been no research conducted into the optimal layout of the
assembly process, resulting in an assembly process with a lot of waste
Pendracare does not know what the maximum output of the current assembly process is and what measures could be taken to improve this
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2.2 Research goal
Due to a lack of time and money the current guiding catheter assembly process has an inefficient design, leading to a lot wastes. This research is focussed on determining measures for increasing the output. This assembly process is faced with a significant forecasted increase in demand for the coming years. Expected is the current process will not be able to deliver these quantities. Therefore it is important to increase the output of the assembly process in such a manner that it is able to cope with the high customer demand. This leads to the following goal for this research:
2.3 Research question
The research goal has been translated into a main question for this research, which is defined as:
To answer this main research question a set of sub questions is introduced, these questions are:
• What is the current state of the assembly process?
• Which measures could be taken in order to increase the output of the assembly process?
• What effect do these measures have on the performance of the assembly process?
• What should the layout of the assembly process be in order to cope with the increased output levels?
• How could the current production planning and control process be improved?
Determine measures for increasing the output of the guiding catheter assembly process
What measures could be taken in order to cope with an increasing demand for 5F, 6F, 7F and 8F guiding catheters?
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2.4 Conceptual model
The goal of a conceptual model is to define boundaries for the conducted research and to get a clear picture of the actual problem. In this case a causal conceptual model has been constructed, giving the variables that are of influence to the research and their individual (causal) relations. The variables in this model are characterised on the level of properties of the system that can be influenced in order to change the outcome of that specific system (Prins, 2010). This has led to the following conceptual model:
Figure 3: Conceptual model
For the conducted research the variables on the system properties level are: The organisation of the assembly process, Production planning and control and The layout of the assembly line. These variables can be seen as knobs of the system that can be turned in order to improve the output, in this case the performance of the guiding catheter assembly line.
The organisation is the first variable that is of interest to this design research. With the organization of the assembly process is meant the number of operators working in a shift and the number of shifts the assembly cell is operated during the day. Production planning and control is concerned with distributing the customer orders over the available capacity of machines, operators and time. The final variable is the layout of the assembly line, this covers the grouping of operators, machines and spaces within a confined area. The relationships between the three variables are reciprocal, the new layout of the assembly line cannot be optimal without considering the production planning and the organization, this also goes the other way around. The variables influence not only each other, but also the performance of the assembly line. Therefore it is important to design these variables in such a way that the output benefits most from it.
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Performance measuring
During this research several proposals for increasing the output of the guiding catheter assembly process shall be made, each having certain advantages and disadvantages. Therefore it is important to determine these measure while keeping in mind the performance of the assembly cell. This could be done through using the five Key Performance Indicators (KPI’s) from Slack and Lewis (2008).
Influencing the system variables will result in either an improved or a worse performance. The KPI’s, that were gathered using literature and interviews, are: Assembly process costs, Throughput time, Quality of the output of the assembly process, Flexibility of the assembly process and Reliability of the assembly process. In order to determine what effect the changes made in the system level variables have on the performance of the assembly process the defined KPI’s need to be made operational.
• Throughput time: The elapsed time between the beginning and the end of a manufacturing process. Also defined as the time needed to fulfil the need of an internal or external customer.
• Assembly process costs: These are the costs implied with assembling the guiding catheter.
Costs can be divided into three groups, these are: operating cost, capital cost and work capital. Where operating costs are costs regarding e.g. labour, material and energy. Capital cost are the expenses made for the production facilities such as machines and buildings.
Finally work capital is the costs incurred for covering the time between outgoing and incoming cash flows.
• Flexibility: This is the ability to adopt different states, take up different positions or do different things. An operation is flexible if it can exhibit a wide range of abilities. There is a distinction between a number of types of flexibility, these are: product flexibility, mix flexibility, volume flexibility and delivery flexibility. Where product flexibility is the ability to introduce and produce novel products and modify existing ones. Mix flexibility is the range of products which the company produces within a given time period. Volume flexibility is the absolute of aggregated output which the company can achieve for a given product mix. And delivery flexibility is the extent to which delivery dates can be brought forward.
• Quality of products: Quality consists of two parts, the first is the degree to which the product complies with the specifications and the second is the quality of the specifications. Next to this it is also important that the products not only comply with the specifications, but are also of consistent quality and reliable.
• Reliability: This is the degree to which delivery agreements are met.
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Research Constraints
When designing the measures for improving the performance of the guiding catheter assembly process there are, in addition to the properties of the system that could be influenced, a number of constraints that cannot be influenced, but need to be taken into account. Even though they cannot be changed and therefore cannot be used to improve performance they play an important role during this design research. The design needs to optimize performance within the boundaries set by the constraints. These constraints could be found in the following figure:
Figure 4: Constraints in the design
The first is the layout of the production area located in the clean room, the floor space is set and thereby cannot be changed. Thus the assembly line needs to be designed in such a way that it fits the available production space. Besides the restriction on assembly space there is also the floor of the production room, which in some places is not strong enough to carry the two heavy laser machines.
Only on those places where there are support beams underneath the floor it is able to withstand the load. This means the places where the two laser machines could be placed are limited to the number of support beams.
Another constraint for this research is the capacity of the current machines, this is not infinite. The level of output is amongst other things determined by the capacity of the machines used in the assembly process. The performed calculations during this research are based on the maximum output of machines, therefore increasing the output beyond the calculated levels cannot be done with the current machines. When increasing machine capacity an investment has to be made to purchase new machines.
Location of the lasers
Fixed constraints
Machine capacity Layout production
area
Layout assembly
line
Production planning &
control Organisation System level
variables
Output
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2.5 Methodology
Verschuren and Doorewaard (2003) classify this type of research, during which different measures for improving performance are thought out, as a design focussed research. De Leeuw (2002) uses the following definition for what he calls a design problem:
A design problem is a description of:
1. A mess of actors and their subjective problems that are 2. arranged by and translated into the functioning 3. of (a subsystem of) the organisation and
4. that have been linked to a professional appointment (interpretation in theoretical terms) mostly from a strategic perspective and
5. have structural causes and/or that can be solved by changing the structure.
In the case of the assignment at Pendracare the subsystem of the organization where the problem lies is the assembly line of the guiding catheter. This problem could be solved be solved by proposing measures for improving the performance of the assembly process. Problem solving is making problems disappear trough the use of aimed actions (de Leeuw, 2002).
When conducting research it is important to use the right methodology in order to apply structure, a useful tool for this is using the DDC model from de Leeuw (2002). The abbreviation DDC stands for
‘Diagnosis’, ‘Design’ and ‘Change’. This model provides a simple route that could be followed in order to come to the desired improved situation. The model consists of three consecutive phases, as could be seen in figure 5.
Figure 5: DDC methodology
The DDC model shows a structured research should start with a diagnosis of the current (problem) situation, the goal of this is to get a clear picture of the actual design problem at hand. This phase consists of a description of the organization, the problem as encountered at the organization, evaluation criteria for this problem and the accompanying theory that should be used during this research. A brief description of Pendracare and a description of the design problem have already been given in the previous sections, a more thorough analysis of the problem situation will be performed in the next section of this thesis. A value stream map will be composed for the guiding catheter, creating a ‘current state map’. In this current state both the information flow and the material flow are traceable. With the help of this Current state map the wastes throughout the assembly process could be identified. Wastes that are found in the product’s design, the processing machinery already bought or the remote location of some activities are difficult to change, that is why they should be seen as given throughout the VSM process.
The final step in de Leeuw’s (2002) DDC model is change, here the improvements to the assembly process, as drawn up in the Future state map, are implemented into the actual process. However this
Problem situation
Improved situation Solution
Problem
Design Change
Diagnosis
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final step is outside the scope of this research. The goal of this internship is to formulate an advise on what changes should be made to the layout of the assembly process, it is then up to Pendracare to implement these changes.
2.6 Report Layout
The report will be structured using the three phases of the DDC model as presented in the previous subsection. The upcoming section will continue with the diagnosis of the design problem. First the assembly process as discussed in the introduction will be explained more thoroughly, one process at the time. This will be followed by the design of a current state map of the assembly process, giving additional important information of this process. Section three is concluded with the current layout of the assembly process. Using the information as gathered in this section a diagnosis of the design problem is formulated.
Section four gives a scenario analysis of possibilities for distributing the different French sizes that will be available in the near future over assembly lines. This differs from one to three assembly lines, leading to three scenario’s. Within each scenario different possibilities for increasing the output are determined. Section five explains what the layout of the assembly line should be in order for it to be possible to assemble the quantities as calculated in section four. Whereas the options for increasing the output as given in section four imply adding either operators or machines to the assembly organisation, the options in section six aim at increasing the output without changing the current organisation.
The last section of this research deals with the last variable in the conceptual model that is of influence on the layout and its performance, this is production planning and control. This is followed by a conclusion and recommendations and ended with a discussion of the research conducted during this internship.
The change step is beyond the scope of this research, the thesis is written with the goal of coming up with measures for improving the performance of the assembly process. The implementation of the propositions should be done by Pendracare.
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3. Current state
This section gives an overview of the current state as found at Pendracare, it begins with a more in depth description of the guiding catheter. This is followed by a description of the customer orders and the manner in which they are dealt with. Followed by a detailed overview of the assembly process and the adjacent inspection steps. Based on the data concerning the assembly and inspection steps a value stream map is constructed. Finally this section is closed off with an overview of the layout of the assembly room.
3.1 The guiding catheter
A few years ago the guiding catheter has been completely redesigned due to negative feedback from the market. This has lead to the β guiding catheter which was launched last year. Although this catheter was a significant improvement in comparison to the old guiding catheter, there was still some negative feedback from users. Therefore the design of its successor, the ‘α’ was initiated quickly after the launch of the β. This has lead to the launch of this new catheter in the beginning of 2011 and a relatively new assembly process. The design of the guiding catheter can be found in the following figure:
Figure 6: Schematic drawing of a guiding catheter
Size and shape
The French (F) scale system is used to measure the diameter of a catheter. 1 F = 0.33 mm and therefore the diameter of a catheter in millimetres can be determined by dividing the French size by three. An increasing French size corresponds with a larger catheter diameter. For the diagnostic catheter there are three different French sizes, these are 4F, 5F and 6F. For the guiding catheter there is currently only one French sizes the 6F, however there are plans for the future to start producing the 5F, 7F and 8F.
Besides multiple French sizes catheters are also produced in different shapes, each shape is used for optimal manoeuvring throughout the specific target vessel it was designed for. A lot of shapes are named after the physician that thought of that specific shape, for instance the Judkins and the Amplatz, but there are also shapes that are named after the way they look, like the pigtail. For the diagnostic catheter there are 62 different shapes and for the guiding catheter there are 28 shape configurations.
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Figure 7: Examples of catheter shapes, the left catheter has a JL4 shape and the right catheter has a JL5 shape
Figure 7 shows two examples of different shapes of catheters, when the coronal artery is targeted by the physician the Judkins Left is often chosen. The catheter on the left is the Judkins Left 4 (JL4), this catheter is used in an aorta with a normal condition. When the aorta is dilated, like in the picture on the right, the JL5 will be the catheter of choice. The more extended secondary curve is needed to reach a supporting surface in the aorta.
3.2 Customer orders
Sales of the guiding catheter started recently, meaning it is in the initiation face. Pendracare is visiting (potential) customers to show them their newly developed guiding catheter in the hope it will enthuse them to place an order. This already led to the first few orders coming in, the size of these orders varies between approximately 10 to 500 guiding catheters, however it is likely orders will be larger once customers have gotten familiar with the product and placed several repeat orders. Since sales are still in the start up face there is no data available on frequency of purchases by customers and the variance of demand over time, because of this demand patterns cannot be determined yet.
However Pendracare did come up with a forecast for the years 2010, 2011 and 2012, in which sales of respectively 10.000, 45.000 and 300.000 α guiding catheters are estimated for the entire product mix.
Currently the guiding catheter assembly process is partly made-to-order and partly made-to-stock.
Once a customer has placed an order at Pendracare this is put, along with the other orders and a sales forecast in MRP, which then generates a weekly planning. This weekly planning results in work orders that are send to the extrusion department, the assembly department and the shaping and packing department two to three times a week. For the extrusion department a work order is the signal to start producing catheter bodies. When the extrusion department has finished producing catheter bodies the batch, which is fitted with a work order is pushed forward to the assembly department, regardless of the capacity left at that department. This work order contains, just as the extrusion work order no customer specific information, it only gives information about how many catheters from which size should be assembled. After the bodies have visited the injection moulding department they are put on stock. When the shaping department receives a work order it contains, unlike assembly orders, customer specific information concerning the different required shapes. The catheter bodies are picked from the stock created after injection moulding.
Therefore the first part of the production process, from the extrusion department up till injection moulding is made-to-stock. Whereas shaping and packing processes are made-to-order.
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3.3 Assembly process
As discussed this research focuses on the assembly process design of the guiding catheter. The assembly process of the β guiding catheter is made up from the following consecutive process steps:
Figure 8: Assembly process of the β guiding catheter
The assembly process starts in the clean room located on the first floor of the factory, it could be commenced once unassembled guiding catheter bodies have been moved from the ground floor, where they are produced, to the clean room. At this moment there are no different catheter body types entering the assembly process at the ablation process, they are all the same. However in the near future this will change, production of the guiding catheter will then also include the 5F, 7F and 8F guiding catheter. The laser processes are explained in more depth in the next part of this thesis, the explanation of the other assembly steps can be found in the appendix.
Laser ablation
Pendracare has recently purchased two sophisticated lasers to perform three operations, these three are: ablation, annealing and cutting. When the catheters are entering the assembly line they are covered with a topcoat. During the first step of this assembly process, which is ablation, about 15 mm of this topcoat material is removed, exposing the braided metal wire that lies underneath this layer. Due to the heat of the laser the topcoat material is burned away.
Laser annealing
The catheter is then put into the second laser machine, where this braided metal wire will be annealed. Annealing is a heat treatment wherein the metal is heated above the recrystallization temperature and then cooled down again, causing changes in properties such as hardness and strength. In the case of the guiding catheter the annealing process is done to relief stress in the braided wire. This prevents the wire from pointing in all possible directions once the uncovered braded wire is cut into the right length.
Laser cutting
The cutting to length, which is the last laser step is done on the same laser machine as the ablation process, which means the catheter moves back one station. The machine settings for ablation and cutting are not the same, this means the machine has to be changed over every time it shifts between the two operations.
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The α guiding catheter
The assembly process of the α guiding catheter is nearly the same, with one difference compared to the β guiding catheter. Whereas the β has a Teflon inner layer in the α this is missing. Therefore no filler ring has to be fused to the body in order to restore this layer. Meaning one step is removed from the assembly process. However in return for this a process has also been added to the assembly steps. In the α design the topcoat material covering the braided wire melts under the influence of the heat coming from the laser. This topcoat material gets through the braided wire and enters the inside of the catheter, causing the inside to contain sharp points. This is not a desired situation, since the sharp edges could damage instruments entering the body through the guiding catheter. To remove these sharp edges the catheter is inserted into a flare tool. This flare tool reheats the basecoat material and pushes it back between the braided wire in order to remove any sharp points.
There is a second difference although both catheter types undergo a shaping process, the processes themselves differ. The β is shaped in two steps, where the first step is a heating process and the second induction. The α on the other hand is shaped using two heating steps, whereas the first heating tool has the capacity to shape four catheters at the time and second, shape oven, can handle fifteen catheters. There is an exception to this, there are a few shapes that do not need the first shaping step, they only require to be placed into the shape oven. Keeping in mind the different assembly steps compared to the β guiding catheter, this leads to the following consecutive assembly steps for the α guiding catheter:
Figure 9: Assembly steps for α guiding catheter
3.4 Inspection
Due to time and financial restrictions the choice was made not to validate the entire production process of the guiding catheter. This decision resulted in a production process for which Pendracare could not guarantee the quality of its output. Quality is an important performance indicator for every company, but for Pendracare this is extremely important. They are producing medical devices that are inserted into the human body, when something is wrong with a catheter it could permanently damage parts of the body. Therefore Pendracare needs to strive for the highest possible quality, in order to minimize the risk for the patients the catheters are used on. Because of the absence of a process validation every step in the production process needs to be followed by an inspection, in order to be able to guarantee the level of quality. For the assembly process this means that after every assembly step an inspection needs to be performed, before continuing with the next assembly step. This has led to a lot of inspection steps that need to be taken to make sure the quality of the guiding catheter can be guaranteed to customers, an overview of these steps can be found in the appendix.
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3.5 Value stream map
In order to get a clear view of the guiding catheter assembly process a value stream map has been constructed, which could be used as input for pointing out possible areas for improvement. A value stream is all the actions, both value added and non-value added, currently required to bring a product through the main flows essential to every product: (1) the production flow from raw material into the arms of the customer, and (2) the design flow from concept to launch (Womack &
Jones, 1996). A value stream perspective focuses on improving an entire process, not just on optimizing its parts.
The value stream mapping method is a visualization tool oriented to the Toyota version of lean manufacturing, the Toyota Production System. It helps to understand and streamline work processes by using the tools and techniques of lean manufacturing. The goal of VSM is to identify, demonstrate and decrease waste in the processes of an organisation (Rother & Shook, 2003). Where waste is defined as an action that does not add value to the final product. It can be used as a communication tool, a business planning and a tool to mange change processes.
A value stream map follows a product’s production path from customer to supplier and displays a visual representation of every process in the material and information flow. The map contains two types of flows, the first type of flow is the movement of material through the factory and the second type is the flow of information that is used to let each process know what to do or make next (Rother
& Shook, 2003). In the lean manufacturing literature the information flow is treated with equal importance as the material flow.
Current state map
Developing a current state map implies going through four stages (Brunt, 2000), these four stages are:
1. Gathering details about the customer’s requirements
2. Detail the physical flow with all processes, data boxes and inventory triangles 3. Mapping the supply of materials
4. Mapping the information flow and determine push- and pull systems
The guiding catheter is a relatively new product which has not been on the market for a very long period, therefore not much is known about what the customer requires. However some things are already known, the customer wants a high quality guiding catheter that is designed according to their requirements. This is why during development there were several prototypes of the guiding catheter developed, each with different properties. These different guiding catheters were taken to several physicians who then chose the prototype that best fitted their needs and should be taken into production.
Another import customer requirement is quick delivery, customers do not want much time to elapse between the moment an order is placed and the moment they are summoned to collect their catheters. Pendracare has set themselves the goal of a throughput time of two weeks, however since there have only been a few orders that were placed it is not realistic to say whether or not this goal could be met. It is the presumption that with the current layout and capacity this goal cannot be met during periods of high demand.
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An important part of a current state map is gathering data about the individual processes, this is used when making decisions about the future state. The first characteristic of each process that is important for this research is the cycle time, which is defined as the time that elapses between one part coming off the process to the next part coming off, given in seconds (Rother & Shook, 2003).
The next data that is gathered is the changeover time, the time to switch from producing one product type to another (Rother & Shook, 2003). Also data about the number of operators working in each assembly station and the available production time. Using this data points for improvement in the assembly process can be determined.
First a value stream map for the current β guiding catheter assembly process was constructed, which as mentioned before resembles the α guiding catheters assembly process to a great extent. The difference lies in the filler ring process which has been removed and the flaring process which has been added. The second difference is the shaping process, whereas both types need to be shaped the process used for this differ. The β is shaped using induction and the α in a shape oven. The cycle times as given in the value stream map are average times. The calculations for these times are based on a ten cycle analysis. These ten cycles were filmed, after which they were carefully inspected and an average cycle time was calculated. This method was chosen to minimize the chance of false measurements due to possible variability in the process. The β guiding catheter value stream map can be found in appendix A.2. It served as input for the α guiding catheter value stream map, because as mentioned before a lot of the processes used to assemble the β are also used for the α.
The processes that were used to assemble the α, but that were not used for the β, have been filmed during assembly of catheters for the purpose of engineering tests.
All information gathered in the previous sections combined has lead to the current state map of the assembly process of the α guiding catheter, found in the following figure on the next page. The processes located within the border created by the dotted line make up for the assembly process.
This current state map contains the cycle time of each of the assembly process. These times consist of the time a catheter spends in a machine plus the time required for the manual actions at that specific process. This also includes the time spent on the inspections required after each assembly step.
When looking at these combined times the longest process is soft- and intermediate tip fusing.
However there are a lot of manual tasks required for this process that could be divided among operators. When looking at the actual time the catheter spends inside the machine, including the loading and unloading of this machine, the ablation process takes the longest, namely 145 seconds.
Although this is still not the machine setting the pace for the assembly process, this is the entire loop the guiding catheters have to make at the two lasers, this will be elaborated in more depth in the coming section. A second point that becomes apparent from this VSM is that next to the small inventory build ups within the departments, due the batch production, there are large inventories built up between the departments.
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Figure 10: Current state map_assembly process α guiding catheter
