1

Chapter 2 Literature Review

In this chapter we take a look at what the concept of lean it’s all about. We start by

describing the origins of the lean thinking, a summary of where and how it was created. Then

we take a look at the main principles and concepts of lean manufacturing for a clear

understanding of the project as a whole. Finally, we enlighten the reader through the main

lean tools, procedures and techniques, such as Visual Management, Value Stream Mapping or

Cellular Manufacturing, required for a clear interpretation of the achieved results during the

course of this project.

2.1 - History of Lean Production

The lean production system was born in the automobile industry or, as Peter Drucker

labeled it, “the industry of industries”. The term Lean was introduced for the first time by

James Womack, Daniel Jones and Daniel Roos in their book “The Machine that Changed the

World” based on a five year study observing the differences between mass production, craft

production and lean production in this gigantic industry.

Table 2.1 – Comparisons of Lean Manufacturing with other Production Systems [2, p. 2]

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According to them [3], after World War I, Henry Ford and Alfred Sloan (General Motors)

established the age of mass production as contrast to the centuries of craft production led by

European firms. As a result, the United States dominated the global economy. But, after

World War II, Eiji Toyoda and Taiichi Ohno at the Toyota Motor Company pioneered the real

concept of lean production, making Japan the leading economy country, as other Japanese

companies and industries copied this system.

It all started with a collapse in sales at the Toyota Motor Company that forced them to

dismiss a large part of their work force in 1949. “In thirteen years of effort, the Toyota

Motor Company had, by 1950, produced 2,685 automobiles, compared with the 7,000 the

Rougue was pouring out in a single day”. [3, p. 48] In the effort of turning this around, Eiji

Toyoda, in the spring of 1950, set out on a three-month tour to Ford’s Rouge plant in Detroit,

studying every inch of this factory. Throughout this journey, Eiji noticed that the American

automobile manufacturers used a remarkable system, however this mass system could not be

implemented in Toyota, as their budget was only able to have a few press lines and,

furthermore, the market required a wide variety of vehicles types. As he returned home, he

started to create, along with his production genius, Taiichi Ohno, a similar, but much

improved system, based on a simple die change technique where they discovered that

producing small sets of vehicles was cheaper than producing huge batches, because of the

reduced carrying costs of inventory and making the mistakes much more clear, since they

were not buried by this massive inventory.

Toyota came to call this system the Toyota Production System (TPS), and, ultimately,

Lean Production (term made popular by the two best sellers “The Machine That Changed the

World” and “Lean Thinking” by Womack, Jones and Roos).

2.2 - Toyota Production System

Taiichi Ohno accepted the apparently unmanageable challenge of matching Ford’s

productivity and, along with his team, worked at the shop floor through years of trial and

errors, solving problem after problem, trying to find the antidote to muda and developing a

new production system, the Toyota Production System.

Muda it’s a Japanese word that means ‘waste’. Precisely, it’s any human activity that

absorbs resources and doesn’t create value to the product or service. Both waste and value

will be explained further more in chapter 2.5 - .

For decades Toyota implemented and improved TPS on the shop floor without

documenting the TPS theory. As it matured, it became clear the difficulty of teaching this

theory across other Toyota plants and ultimately suppliers. As a result, Fujio Cho developed

one of the most recognizable symbols in modern manufacturing – The TPS House (Figure 2.1)

[4]

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Figure 2.1 - The TPS House [4]

As in any house, it will only be strong if the roof, the pillars and the foundations are

strong. Therefore, emphasizing the importance of best quality, lowest cost and shortest lead

time (the roof); just-in-time (JIT), produce only what’s needed, that is to produce the right

part, at the right time, at the right amount (left pillar); And jikoda, that means never let a

defect pass into the next station and freeing people from machines [4] (right pillar).

2.3 - Lean Principles

Womack and Jones [5] describe the TPS philosophy as a concept to create value and

eliminate waste. Therefore, five main Lean principles were associated with it, briefly

described below, and those are: Value, Value Stream, Flow, Pull and Perfection.

Value

Express the capacity of accurately specify value from the costumer

perspective, or what he’s willing to pay, for both products and services.

Value Stream

Identify the value stream of specific activities, from raw material to final

goods, required for the development of a product or service, removing non-value-

adding waste along that path.

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Flow

Make the product or service flow without interruptions across the entire

value stream.

Pull System

The production is authorized (pulled) by the costumer, as opposite to a push

system where the finished goods are pushed to the costumer.

Perfection

Constantly identify and remove any kind of waste along the value stream to

achieve perfection.

2.4 - Lean Benefits

What can an organization expect as bottom-line results of applying lean thinking to

eliminate waste? Documented results across various industries indicate the results in Table 2.2

can be achieved. [6]

Table 2.2 - Lean Benefits [6, p. 104]

2.5 - 7+2 Non-Value-Added Waste

According to [5], Value can only be defined by the ultimate costumer and it’s created by

the producer, being very hard to accurately define from the producer standpoint. Yet, the

concept of value, which is related to efficiency (doing something at the lowest possible price)

and effectiveness (doing the right things to create the most value for the company), can be

metaphorically defined as quality divided by price. “If you can provide the customer with a

better car without changing price, value has gone up. If you can give the customer a better

car at a lower price, value goes way up.” [7]

All of the activities on an organization can be distributed into two categories: the value-

added activities and the non-value-added activities, being the last one unmistakably related

with waste. In [8], this waste can be subsequently classified in two categories:

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Pure waste

These are expendable activities, for example: unproductive reunions,

dislocations or malfunctions. Corporations are obliged to eliminate this kind of

muda and it can reach up to 65% of the total waste of the organization.

Necessary waste

Although they don’t add value, these activities need to be carried out. As

examples those could be inspection of the arriving raw material or setups. These

can take up to 30% of the total muda.

Together, they represent 95% of the organization’s time, which clearly must be

minimized, otherwise only 5% of the time is used for value-added activities.

But what is waste? What is muda? As said before, muda is a Japanese word for waste.

Taiichi Ohno and Shigeo Shingo, during the development of TPS, defined seven major types of

waste in business or manufacturing processes, listed below, that can be applied not only to a

production line but also to product development, order taking or the office.

1. Overproduction

Overproduction can be viewed as the opposite of JIT and it means producing

items for which there are no orders: produce the wrong part, at the wrong time,

at the wrong amount. This waste was considered, to Ohno, the fundamental

waste, since it causes most of the other wastes. In other words, it produces

unnecessary transportation and storage costs due to the excess of inventory.

2. Waiting Time

This is the unproductive time of a worker, or machine, when he’s just waiting

for something. For example, waiting for the next process step, tool or supply, or

just watching an automated machine finishing a process. It could also be the

waiting time due to the lack of work caused by processing delays, equipment

failure or capacity bottlenecks.

3. Unnecessary transport

Moving work in process (WIP), materials, or even finished goods long

distances is an unnecessary and inefficient transport. This will increase

production costs, the lead time, and can even cause damage to the products

during the course of the movement.

4. Incorrect processing

This concerns the unnecessary steps that are taken in a process, possibly

because of the use of poor tools and product design, causing unneeded motion

and producing defects (waste seven).

5. Excess inventory

The excess of raw materials, WIP or finished goods can cause longer lead

times, damaged goods and delays.

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Extra inventory also hides problems such as production imbalances,

redundancies, defects, paperwork, equipment downtime and long setup times.

Figure 2.2 easily exemplifies this situation through an analogy where water

represents inventory and rocks represent problems. In this case, with a high water

level, the rocks are hidden and the management assumes everything is fine, until

the water drops and the problems are presented. Deliberately forcing the water

level down, all the problems are exposed and can be corrected before they

induce other possible even worse problems.

Figure 2.2 – Inventory hiding problems [7]

6. Unnecessary movement

These are all the needless motion employers have to perform during a

process, such as walking or looking for, reaching for, or stacking parts, tools, etc.

7. Defects

This waste is the production of defected parts or correction, that is, repair,

rework, scrap, replacement and inspection means wasteful handling, time, and

effort.

Liker [4] defined another waste:

8. Unused employee creativity

Not engaging or listening to your employees can cause the loss of ideas, skills,

improvements or learning opportunities.

Yet another waste that I consider relevant not only for the industry, but also to

households, is the waste of energy (also referred in [8]).

9. Energy Consumption

Through time, it became more and more important to rationalize the

consumption of energy, giving great advantages for the consumer and the

environment, being the decrease of energy costs the most attractive benefit for

the consumer. There are numerous ways and techniques for a more efficient

energy use, like the replacement of conventional luminaires with more efficient

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ones, dimensioning a capacitor for the control of the reactive energy, micro

production, cogeneration, etc. It is recommended to do an energy audit to start a

more rationalized use of energy.

2.6 - Continuous Improvement

In Japanese, Continuous Improvement is known as Kaizen, which literally means change

(kai) for the better (zen), term that has come to be accepted as one of the key concepts of

management when the book by Masaaki Imai “Kaizen: The Key to Japan’s Competitive

Success” was published in 1986.

The word Kaizen implies improvement that involves everyone – both managers and

workers - and entails relatively little expense. The kaizen philosophy assumes that our way of

life – be it our working life, our social life, or our home life – should focus on constant-

improvement efforts. This concept is so natural and obvious to many Japanese that they

don’t even realize they possess it! [9]

There are three major components that involve continuous improvement. [8] The first

one encourages people to make mistakes, what can be seen as counterintuitive. Many

organizations punish mistakes and tend to label who made them as ‘losers’ or ‘incapables’.

This creates a fear of failing that deprive us of continuously try and improve. In fact, one

should understand why do those mistakes happen and avoid that they are repeated.

The second component encourages and rewards people to identify problems and solve

them. This is based on the principle that the one that better knows a process is the one who

makes it. A top manager will not have the same acknowledge of a manufacturing process as

the machine operator of that process.

To finish, the third component asks people to identify ways of making things better, that

is, encourages them to constantly overcome themselves. This is a way of proactive

empowerment.

Continuous Improvement is an ongoing and never ending process and there are different

kinds of continuous improvement tools, for example the PDCA Cycle, Standardization or the

5W1H.

2.6.1 - PDCA Cycle

The PDCA cycle has its origins in the Shewhart Cycle by Dr. Walter A. Shewhart in 1939.

Figure XX presents the Shewhart Cycle and the contrast with the precious straight line, as Dr.

Shewhart itself wrote “In fact these three steps must go in a circle instead of in a straight

line as shown in fig. 10 [in this case Figure 2.3]. It may be helpful to think of the three steps

in the mass production process as steps in the scientific method. In this sense, specification,

production, and inspection correspond respectively to making a hypothesis, carrying out an

experiment, and testing the hypothesis. The three steps constitute a dynamic scientific

process of acquiring knowledge.” [10, pp. 44-45]

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Figure 2.3 – Shewhart Cycle, 1939 [10]

In 1951, Dr. W. Edwards Deming modified this cycle at the Japanese Union of Scientists

and Engineers (JUSE), adding a fourth step to the cycle and stressing the importance of

constant interaction among design, production, sales and research and that the four steps

should be rotated constantly, with quality of product and service as the aim. The Japanese

called this the “Deming Wheel” [11]

Figure 2.4 – Deming Wheel [11]

Directly from the 1950 version, Deming reintroduces the Shewhart Cycle in 1986, stating:

“Any step may need guidance of statistical methodology for economy, speed, and protection

from faulty conclusions from failure to test and measure the effects of interactions.” [11]

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Figure 2.5 – The Shewhart Cycle, 1986 [12]

Again, in 1993, Deming modified the Shewhart cycle and called it the Shewhart cycle for

learning and improvement, or the PSDA Cycle. “A flow diagram for learning and for

improvement of a product or of a process” [13]

Figure 2.6 – PDSA Cycle [13, p. 132]

Although, it this cycle is well known as the PDCA (Plan, Do, Check and Act), Deming

stated in the Moen, Nolan, and Provost manuscript, “… be sure to call it PDSA, not the

corruption PDCA.” He warned Western audiences that Plan, Do, Check and Act version is

inaccurate because the English word “check” means “to hold back”. [11]

In short, the PDSA cycle has four steps:

Plan – Definition of a problem and identify an opportunity and plan for change

Do – Implement the change on a small scale

Study – Analyze the results of the change and study its modifications

Act – If the change was successful, adopt the change and continuously study the

results. If the change was not successful, run the cycle again.

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2.6.2 - Standardization

A standardized work or process is a much easier work to teach, improve, document, audit

and transfer. Thus, all efforts in this direction are welcome unless they constrain the creative

processes of people. [8]

With standardized work there’s no space for improvised tasks that may destroy plans and

day-to-day budgets. In other words, everyone does the same process in the same way and if

someone identifies a better, faster and efficient method for this process, this method is

made a standard. In every cycle of the PDCA, it should be noted the knowledge and good

practices promoting standardization, transforming the PDCA cycle into the SDCA (standard,

do, check, act).

2.6.3 - 5W1H

5W1H was originated from a poem wrote by Rudyard Kipling, thus being also known as the

Kipling Method, which started:

I Keep six honest serving-men:

(They taught me all I knew)

Their names are What and Where and When

And How and Why and Who.

This is a well-known quality management technique that is based on six trigger questions:

What? Why? Where? When? Who? and How?. These are useful in collecting information to

ensure the fulfillment of a certain action plan, diagnose a problem and design solutions. It

can be generically view in two ways, with the change of the end question:

To find the root problem cause:

o What is the problem?

o Why does it occur?

o Where is it located?

o When does it occur?

o Who is involved?

o How did it appear?

To find a solution to a problem:

o What will be done?

o Why is it being done?

o Where will it be done?

o When will it be done?

o Who will be responsible for it?

o How will it be implemented?

Lately it has been included the how much question, transforming the 5W1H in 5W2H, as in

“How much does it cost to have this problem?” or “How much does it cost to implement this

solution?”

2.7 - Lean Tools and Techniques

In this subchapter we explain how the main lean tools and techniques, used during this

project, are performed, providing a clear perception of how we achieved some

values/results. We start by elucidation the reader about Visual Management including the 5S

program, its importance and implementation method. Carrying out with an insight about the

Value Stream Mapping (VSM), how to draw one and its main principles, also referring to the

11

ABC Analysis, a tool that clarifies which of a company’s products are the most important to

management (an important task to start the a VSM). We finish this with a perception of the

characteristics and benefits of cellular manufacturing and how to balance a line.

2.7.1 - Visual Management

Work must be rigorously standardized (by the work team, not only some remote industrial

engineering group) and that employees and machines must be taught to monitor their own

work. This matters need to be coupled with visual controls, ranging from the 5Ss (where all

debris and unnecessary items are removed and every tool has a clearly marked storage place

visible from the work area) to status indicators (often in the form of andon1 boards), and

from a clearly posted, up-to-date standard work charts to display of key measurable and

financial information on the costs of the process. The precise techniques will vary with the

application, but the key principle does not: Everyone involved must be able to see and must

understand every aspect of the operation and its status all times. [5]

The main role of visual management, or visual documentation, is to convert a personal or

centralized knowledge workplace into some kind of knowledge data base or a public

knowledge workplace (Figure 2.7), creating a work environment that is self-explaining, self-

oriented and self-improving.

Figure 2.7 – The role of visual documentation: converting the workplace into a knowledge field [14, p.

67]

2.7.2 - 5S Technique

A vital component of visual management is the 5S organization system. One of the most

known and applied tool of Lean, has its origins in Japan in the early 70s. The main purpose of

its practices is to provide a more efficient, safe and organized workstation, leading to a

reduction of waste and the improvement of workers and processes performances.

The name of this technique comes from the initial letter of five Japanese words – Seiri,

Seiton, Seiso, Seiketsu and Shitsuke, each one leading to an order of implementation:

1 Andon is a manufacturing term denoting a system to notify all the stakeholders of a quality or process problem

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1. Seiri (sort)

Separate the useful from de useless. That is to sort through items and keep

only what is needed to perform value-added-activities and dispose of what is not.

A method to do this is the red-tagging. This consists in marking the rarely

used items with a red tag (Figure 2.8), identifying them as an item to remove from

the workplace. This can be done according to the next table.

Table 2.3 – Red tag classification

Red tag Usage Frequency Where to place

Daily Workstation

Once a week Work area

✓ Once a month Storage place

✓ Once a year Warehouse

✓ Obsolete Sell/Eliminate

Figure 2.8 – Red tag example

2. Seiton (orderliness)

“A place for everything and everything in its place” is the phrase that truly

describes this step. There must be well-defined place for everything and check

that everything is in its place. The most frequently used gear need to be placed

at hand (avoiding unnecessary movement for the worker), and visual help

(identifying labels) should be on the gear and at the place where they must be

placed.

3. Seiso (cleanliness)

Cleaning the workstation anticipates failure conditions that could hurt the

product’s quality or cause machine failure.

4. Seiketsu (standardize)

Define a standard regulation for order and cleanliness in the workplace. In

other words, develop systems and procedures, with visual controls for example,

to maintain and monitor the previous S’s.

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5. Shitsuke (self-discipline)

Maintain a stabilized workplace in an ongoing process of continuous

improvement.

An unfortunate consequence of this technique is that many companies confuse 5S with

lean production itself. They implement the 5S, do workshops about it, and in the end, they

don’t get time or costs reductions and quality doesn’t improve. It must be noted that 5S is

not to organize and label materials, tools and create a shiny environment, it is a support to

lean systems for a smooth flow to takt time. [4]

2.7.3 - Spaghetti Diagram

From a lean perspective, the first thing you should do in approaching any process is to

map the value stream following the circuitous path of material (or paper information)

through your process. The best way to do this is to walk the actual path of the process, draw

it on a layout of the plan and calculate the time and distance traveled - this is called the

“spaghetti diagram”. [4]

Although spaghetti diagrams are a simple way to analyze the product flow, they do not

contain the level of information that we can find in the Value Stream Mapping (VSM).

2.7.4 - Value Stream Mapping

Value Stream Mapping (VSM), or “Material and Information Flow Mapping” as it was known

at Toyota, is a technique originally developed by Toyota and then popularized by the book

“Learning to See” by Rother and Shook.

In their book they define Value Stream Mapping as “a pencil and paper tool that helps you

to see and understand the flow of material and information as a product makes its way

through the value stream. What we mean by value-stream mapping is simple: Follow a

product’s production path from customer to supplier, and carefully draw a visual

representation of every process in the material and information flow. Then ask a set of key

questions and draw a future-state map of how value should flow.” [15]

When constructing a VSM, the flow of information is outlined in the superior part of the

map, starting from the right to the left, whereas the flow of materials is drew in the inferior

part of the map, starting from the left to the right. It is also essential to insert the stock

points with the time they stay waiting for the next process of the flow and below each

process their respective cycle time (see the next illustration). With this, we can easily

determine the product lead time and processing time, or value added time.

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Figure 2.9 – Current State VSM Example [16]

In the previous image we can note different symbols and icons. These symbols represent a

common, simple and intuitive language that promotes an easy comprehension of the map for

everyone. Their meanings are presented in the next picture.

Figure 2.10 – VSM Symbols [15]

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Succinctly, the method to develop a VSM is to start by selecting a product or product

family to map. Then draw a current state map (or AS-IS state) with a clear view of the

current value stream with the flow of materials and information. After carefully analyzing the

current state map and determining what wastes are influencing the lead time, which

activities are and aren’t creating value to the product, it’s time to develop an improvement

plan and draw the future state map (or TO-BE state). Figure XX represents a future state map

of the previous VSM (figure xx).

Figure 2.11 – Future State VSM Example [16]

In this map it should be clear a reduction of the lead time and an improvement in the

processes synchronization. Last but not least one must constantly improve towards

perfection, implementing a continuous improvement policy.

As mentioned, when developing a VSM a question arises – what’s the product, or service,

that we should map? The answer is to choose the one that has the most impact on the

company’s development or the one that has more gaining potential with the implementation

of continuous improvement tools. [8] Consequently, we have the ABC Analysis.

2.7.5 - ABC Analysis

The ABC Analysis consists in categorizing items so that the most important will receive

management attention. [17]

In this analysis, the products are grouped in three categories in order of their estimated

importance (A, B and C), based on the Pareto principle. This principle, also known as the 80-

20 rule, states that the majority of the situations are dominated by a few vital elements, for

example, “80% of your sales come from 20% of your products”.

Considering the annual turnover of a company as a selection parameter, one could

categorize the products as the following example:

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Class A items – 75 to 80% of the turnover, from 15 to 20% of products

Class B items – 10 to 15% of the turnover, from 20 to 25% of products

Class C items – 5 to 10% of the turnover, from 60 to 65% of products

Figure 2.12 exemplifies a typical ABC curve, identifying the three categories of products

and the respected value on production.

Figure 2.12 – Typical ABC Curve

There are no fixed percentages to each class. Different ratios can be applied based on

different objectives and criteria. Yet, they’re categorized through very important to

marginally important products, where:

Class A

These items are the most important ones for the company. Hence, there

should be a tight and rigorous control, quick deliveries/supplies and should be

kept a safety stock.

Class B

These items are less important than class A items, therefore must be the

same concerns as with class A, but with lower incidence.

Class C

These are marginally important items. There shouldn’t be such much

attention and time wasted on these items, since they don’t bring a big impact to

the company’s development.

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2.7.6 - Cellular Manufacturing

The ‘conventional bundle’ and ‘straight line’ systems are the most common approaches to

work organization and often referred to as the ‘line system’ or ‘progressive bundle’ system.

In these methods of working, cut pieces are bundled and distributed to workers to perform

predominantly short-cycle tasks. Having completed their tasks, operators would re-bundle

these pieces and then pass them onto other operators to complete another short-cycle task.

[18]

These systems have led to several familiar problems. Each function tends to act as a

“silo” and hands its output “over the wall” to the next function. They are characterized by

departmental barriers and parochialism, and generally slow progress of work though the

system. Much of the job lead time consists of non-value-adding times devoted to move, wait,

information collection, etc. [19]

Group technology (or cellular) layouts allocates dissimilar machines into cells to work on

products that have similar shapes and processing requirements. The overall objective is to

gain the benefits of product layout in job-shop kinds of production. These benefits include:

[7]

Better human relations. Cells consist of a few workers who form a small work

team; a team turns out complete units of work.

Improved operator expertise. Workers see only a limited number of different

parts in a finite production cycle, so repetition means quick learning.

Less in-process inventory and material handling. A cell combines several

production stages, so fewer parts travel through the shop

Faster production setup. Fewer jobs mean reduced tooling and hence faster

tooling changes

There are relatively few formalized ‘standards’ of teamworking in the apparel context.

The Toyota Sewing System (TSS) is one of them (see Figure 2.13). [19]

Figure 2.13 – The Toyota Sewing System [18]

Some characteristics of the TSS are: [18]

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Operatives stand to allow easy movement between work stations. Ideally, an

operative should not stay standing in the same position as they will move

between work stations.

The module is usually U-shaped. This aids communication between operatives.

Operators work on single garments.

Each operator performs approximately 2-4 operations, depending on the product.

Work flow is sequential.

Operators’ skills overlap.

2.8 - Line Balancing

In the following subdivisions we’ll be explaining the basics for balancing an assembly line,

concepts also essential for the balancing a production cell. In particular, we’ll briefly discuss

the concepts of takt time, cycle time and their relation, and the key steps for balancing an

assembly line.

2.8.1 - Takt time

Takt time, also known as the production pace, is the rate at which customers require

finished units. [15] In other words, it sets the desired time between units of production

output, synchronized to costumer demand.

It stems from the German word ‘takt’ that means pace, beat or musical meter and can be

determined by dividing the productive time available per day and the required demand also

per day.

(2.1)

Note that takt time represents the actual customer demand rate so you must not subtract

time for unplanned machine downtime or other unforeseen internal problems, only the

scheduled downtime for maintenance or planned breaks.

2.8.2 - Cycle time

Cycle time is how frequently a finished unit actually comes off the end of your line or

pacemaker cell. [20] In this case, it includes all types of delays occurred while completing a

job, as exemplified in the next formula:

[21] (2.2)

Cycle time and takt time should be balanced in parallel, with approximated time.

Without this precaution the production may result in a late delivery and customer

dissatisfaction (when cycle time is greater than takt time) or cause excess inventory or use of

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resources (when cycle time is shorter than takt time), like the use of extra operators (Figure

2.14).

Figure 2.14 – Cycling much faster than takt time may require more people [20]

Comparing takt time and cycle time is the easiest way to answer the simple but critical

questions: “How frequently does the customer need one piece?” and “How frequently do we

actually make one piece at our pacemaker process?”.

2.8.3 - Line balancing process

The process of balancing an assembly line involves three major steps: determine the takt

time, calculate the theoretical minimum number of workstations and assign specific assembly

tasks to each workstation. These steps can be performed has described below:

1. Takt Time

We can determine the takt time by dividing the productive time available

and the required demand per day, as previously described.

2. Minimum number of workstations

This can be calculated as the total tasks duration time divided by the

takt time. The total tasks duration time is the sum of all tasks times that

it takes to make the product in analysis.

(2.3)

3. Assign tasks to workstations

Assign tasks, one at a time, to the first workstation until the sum of the task

times is equal to the workstation cycle time, or no other tasks are feasible

because of time or sequence restrictions. Repeat the process for Workstation 2,

Workstation 3, and so on until all tasks are assigned. [7]

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One can also determine the maximum number of production and measure the

efficiency of an assembly line as follows:

(2.4)

(2.5)

References

[1] ATP - Associação Têxtil e Vestuário de Portugal, [Online]. Available: http://www.atp.pt/gca/index.php?id=18. [Acedido em March 2012].

[2] M. Houshmand e B. Jamshidnezhad, “Conceptual Design Of Lean Production Systems Through an Axiomatic Approach,” em Proceedings of ICAD2002 Second International Conference on Axiomatic Desig, Cambridge, MA, 2002.

[3] J. P. Womack, D. T. Jones e D. Roos, The Machine That Changed The World, New York: Rawson Associates, 1990.

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