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3. Design of Cellular Layout

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									 Design of Cellular
  Operations Analysis and Improvement

                   2010 Fall

                  Dr. Tai-Yue Wang
Industrial and Information Management Department
           National Cheng Kung University
   The concept of manufacturing cells was
    presented as a specific case of product/process
       The transformation requires a unique development
        and implementation methodology
   The use of cells creates a unique set of
    production modules
       Transforms the factory into a group of self-managed
        sub-factories or modules.
   This chapter presents some design and analysis
    tools focused on getting a company ready to
    progress to cellular manufacturing.
       Including line balancing techniques.
   The first moveable assembly line was created by
    Ford to manufacture the Ford Model T.
       A capstan and a thick cable to move the cars between
        assembly stations.
       Before this development -> fixed position layout.
   The required time to manufacture a car was
    reduced from 13 hours down to 6 hours.
       Produced only identical black Ford Model T cars.
            It was the color (Black) that dried the fastest.
            Thereby allowing many Americans to afford a new car.
   Ford used many of the specialization ideas
    developed by Adam Smith
       Nail manufacturing
            Better having one worker manufacturing the head and
             another worker the tip.
   Specialization and task decomposition lead to the
    birth of new professions.
       Industrial engineers were devoted to component task
        design and to manufacturing scheduling.
   Alfred Aloan (General Motors) enhanced Ford’s
       Mix different models on the same assembly line.
   During the 1960’s and 1970’s, Japan did not adopt
    the Ford, Aloan and Taylorist way of working
       They expanded worker involvement to handle a
        variety of manufacturing processes.
         Mass production
   Some products are manufactured in very large
    batches to satisfy mass market demand.
       Food products, which are manufactured in high
        volume, will not be addressed in this chapter.
       Other products, such as toys, cars and electrical
        appliances will be studied in depth.
         Mass production
   Mass production has two basic characteristics.
       Low product price as compared with the cost of the
        handmade products.
            Product should be as standard as possible.
       Reducing the number of different replacement parts.
            Reduction in the number of spare parts.
                 Companies must maintain a spare parts accessibility for a certain
                  amount of years.
        Mass production
   Simple product assemblies reduce process
       The cost of each article decreases.
   If the complexity of a product can be increased
    to accommodate additional replacement part
    applications then the part’s utility increases.
        Mass production
   Product-Quantity (P-Q) analysis tool helps to
    decide the optimal plant distribution for the
    different products manufactured.
       Using Pareto Tool.
       If products quantity is large and its variety is small,
        massive production fits perfectly
            Focused assembly lines provide the most economic
             production alternative.
        Flow or assembly lines
   The recommended way to manufacture mass
    produced articles is by using flow or assembly
       Workstations dedicated to the progressive
        manufacture and assembly of parts.
       Integrated using materials handling devices.
        Flow or assembly lines
   Creating flexible cells generally requires the
    duplication of machines.
       Invest in several simple machines with low cost.
            Instead of a versatile and more expensive machine.
        Flow or assembly lines
   Another advantage of assembly lines is that the
    work-in-process decreases.
       Containers with waiting parts are placed in small
       This design eliminates excessive inventory
        required when using more versatile and expensive
            It is more critical to have higher machine utilization of
             more costly equipment.
            It is more difficult to manage a greater variety of
             incoming material.
        Flow or assembly lines
   The most frequently used material handling
    device is the conveyor belt.
       Size of the product -> Overhead conveyor systems.
            Each product stops a predetermined amount of time in
             each station (synchronized flow).
            Each product is removed at a workstation to be worked
             on (asynchronous flow).
          Island layout
   Advantages.
       An effective layout when
        considering product movement.
       Multifunctional workers.
       One-piece-flow.
          Island layout
   Disadvantages.
       Worker is specialized in an island or
       The islands are isolated with respect
        to each other.
       Synchronization among them can be
        Cell layout design justification
   The manufacturing environment has changed
    significantly in the past several years.
                                  PREVIOUS             CURRENT
     Product              Little variety       Great variety
     Delivery time        Not very demanding   Very demanding
     Size of lots         Large                Small
     Lead time            Long                 Short
     Product life cycle   Long                 Short

   Flow or assembly lines focus on high volume
      Cell layout design justification
   The use of process focused systems or job shops
    is focused on very small volume products.
   These systems maximize flexibility, but have
    other problems.
     Cell layout design justification
   Reasons to suggest the use of the
    manufacturing cells as opposed to process
       A high number of indirect workers is generally
        required in process layout.
       A high level of work-in-process is also typical
        of process layout.
       Product quality responsibilities are not as clear
        when using process layout.
     Cell layout design justification
   When cellular layout is properly
       Unnecessary product movement can be
       Product and manpower flexibility can be
       A more economic production environment can
        be obtained.
   The transition to cells is not easy.
Basic cells design nomenclature
   Task -> a set of the necessary steps that the
    work gets decomposed into.
       Is considered the smallest assignable unit to a
            Define the beginning and the end of the task in a
             precise way.
            Methods and time methodologies facilitate the goal
             of optimizing a task.
                 Time study is also briefly presented in this chapter.
Basic cells design nomenclature
   Workstations -> The logical organization of
    specific manufacturing or assembly
    equipment to perform task(s).
       The number should be as small as possible.
            Minimum workforce can be maintained along with a
             reduced work-in-process.
        Basic cells design nomenclature
   Takt-time and cycle time.
       Takt is a German word for rhythm.
            Is a critical term for manufacturing systems design.
       Takt-time is the allowable time to produce one
        product at the rate a customer demands it.
            This is NOT the same as cycle time.
    Basic cells design nomenclature
   Cycle time is the normal time to complete an
    operation on a product in each workstation.
        Should be less than or equal to takt-time.
                              Useful working time in one day
         Takt - time  Tc 
                                      Daily demand

        Cycle time is the sum of the task times that a product
         requires at each station.
   During the cell design project, it is important that
    the takt-time and the cycle time be as close as
             Basic cells design nomenclature
   Takt-time and cycle
    time.                            Cycle
                                                                           (1 unit)
                                             A   B       C         D   E
       Takt-time can never
        be smaller than the
        largest workstation
        cycle time.                  Cycle
                                                                           (1 unit)
                                             A   B       C         D   E
            A rhythm becomes                        workstation

             faster than the
             production system is
             capable of handling
             in the upper diagram.
          Basic cells design nomenclature
   Takt-time and cycle
    time.                    Cycle
                                                                   (1 unit)
                                     A   B       C         D   E
       Cycle time is a
        measure of how
        much time it takes
        for a particular     Cycle
                                                                   (1 unit)
                                     A   B       C         D   E
        operation.                           workstation
     Basic cells design nomenclature
   Total workstation cycle time (pi).
       The sum of the process times for each one of the
        tasks assigned to a workstation.
        Basic cells design nomenclature
   Idle time (hi)
       Difference between the takt-time and the cycle time
        or total work at each workstation.
       It can never be less than zero.
         (That would imply that a station has assigned more work
           than the takt-time.)
       Reality for many assembly companies can be quite
        different than theory.
         (Cell flexibility allows a company to rebalance tasks where
           the maximum cycle time exceeds the required takt-time.)
        Basic cells design nomenclature
   Precedence diagram.
       Precedence restrictions that exist when assembling
        the product.

         T1   16              T4   8

                   T3   12    T5   24
         T2   3
                              T6   6
        Basic cells design nomenclature
   Precedence diagram.
       Characteristics.
            There are only left to right arrows.
            There are no precedence relationships between tasks in
             the same level.
            In the determination of a level, all the tasks without
             precedence among those that have not be placed yet are
             placed in that level.
            The figure also include the task duration.
Cell design methodology
   The methodology to develop production
    cells is very straightforward.
       Form product families.
       Change the machines location.
       Calculate the output production rate, the task
        assignment in each workstation and the
        necessary number of workers in the cell.
       Planning and controlling the cell.
 Cell design methodology

The difficulty lies in the high number of
prerequisites needed to be able to carry out
this layout transformation.
       Prerequisites for cell designing
   Multifunctional workers.
   Determine the required space for the cells
    (specially U-shaped cells).
   Invest in new machinery.
   Improve the set-up time of dies.
       Prerequisites for cell designing
   Look for simple methods for production
   Choose new production planning and control
    systems so that future planning or control of the
    line is not required.
         Line Balancing
   Main goal of line balancing techniques.
       To assign tasks to workstations so that the minimum
        number of workstations can be achieved.
            Each task needed to produce a part are assigned to only
             one workstation.
            In each workstation the assigned work (pi) is less than the
            The idle time is minimal.
       This assignment should not violate any of the
        precedence relationships
         Line Balancing
   Line balancing for some companies may require
    specific algorithms.
       The workers should be assigned to a fixed number
        of workstations.
       The next methodology does not apply.
General steps in the line
   STEP 1. Define the tasks and their times
   STEP 2. Specify the precedence
       Building the precedence diagram.
   STEP 3. Determine the takt-time (Tc).
                          Useful working time in one day
     Takt - time  Tc 
                                  Daily demand
General steps in the line
   STEP 4. Calculate the minimum number of
    workstations (Mmin).
       Supposes the lower limit of the number of
        workstations that can be created.
                   ti 
         M min        
                   C 
General steps in the line
   STEP 5. Choose a task assignment rule.
       This is explained later on.
   STEP 6. Assign tasks.
       Until the assigned time is equal to the takt-time
       Until it is no longer possible to assign a task
        due to the restrictions of time or sequence.
            In this case it will be necessary to create a new
             workstation and continue with the assignment.
General steps in the line
   STEP 7. Determine the total idle time and
    the line efficiency.
                 M                      M

     H  M  c   pi                  p     i

                i1     Efficiency    i 1

                                       M  Tc

   STEP 8. If the obtained solution is not
    considered acceptable -> choose another
    assignment rule.
Line balancing--Tasks
assignment rules
   A task is eligible if it has not yet been
    assigned and all those that precede the task
    (preceding tasks) have been.
       It will be necessary to decide among several
        eligible tasks.
            There are different heuristic methods.
Line balancing--Tasks
assignment rules
   Heuristic methods are simple rules that
    propose two selection criteria.
       The second criteria will only be used if there
        are several tasks that coincide in the first
       The obtained solutions can be compared by
        analyzing the idle time share among the
     Line balancing--Heuristics
   Total number of following tasks heuristic.
       Among the eligible tasks -> choose the task that
        has the largest total number of following tasks.
       If two or more tasks coincide -> select the task
        with the longest time ti.
        Line balancing--Heuristics
   Individual durations heuristic.
       Among the eligible tasks -> choose the task with
        the longest time ti.
       If two or more tasks coincide -> select the task that
        has the largest total number of following tasks.
        Line balancing--Heuristics
   Largest positional weight heuristic.
       Among the eligible tasks -> choose the task that
        has the largest positional weight.
            Positional weight is the sum of the task time and the
             time of all its following tasks
       If two or more tasks coincide -> select the task
        with the longest time ti.
        Line balancing--Special cases

   Task time larger than the takt-time.
       Accept that the task dictates the takt-time.
            Supposes the loss of possible product sales or to increase
             the number of pending orders.
    Line balancing--Special cases
   Solve the problem.
        Divide the task into two tasks.
             Analyze and define the task again.
        Improve the task or the product.
        In case of an assembly task incorporate an assistant.
        Place two workstations in parallel.
             It increases the work-in-process.
             This solution will be adopted if and only if the other choices are
              not possible.
                                      S2’     0

               S1     0                                     S3      0

                                      S2’’    0

       0   5    10   15     20   25    30    35

         Line balancing in U-shaped cells

             S1    S2     S3     S4      S5

   The line balancing method,
    sometimes, causes an unequal
    time assignment.
                                         S1   S2   S3
       The U-shaped layout, with
        shared tasks, helps to solve
        these unequal times assignment
        situations.                      S6   S5   S4
      Line balancing in U-shaped cells
   U-shaped cells avoid constant displacements to
    the start of the line and solves many of the
    island distribution problems.
               S1      S2       S3

               S6      S5       S4
        Line balancing in U-shaped cells
   Advantages.
       Improves the tasks assignment by offering production rate
            The number of workers assigned can be changed at any time.
       Makes easy to adapt the cycle time to the tack time without
        rearranging the task assignments.

             S1     S2            S1       S2              S1      S2

             S4     S3            S4       S3              S4      S3
                                                            S1      S2         S3
         Line balancing in
         U-shaped cells                                     S6      S5         S4

   The mathematical resolution of U-shaped line
    balancing needs to be solved in a good way.
       Solutions can be obtained through two different ways.
            Observation of the workstations and their corresponding
             idle time.
            Make the line balancing supposing a takt-time (Tc’) equal
             to half of the takt-time (Tc’ = Tc/2)
                 Later, bending the line.
                 The problem arises when the number of workstations is odd.
                                  s1        0             s2   0   tc’=5

                                  s4        0             s3   0

                            S1              0        S2        0

     0   5   10   15   20        25    30       35

U-shaped LB with a ti larger
than Tc’
            6 min.             8 min.             6 min.

             s1                s2                  s3

             s5                                    s4               tc=12 min
            6 min.                                6 min.           tc’=6 min

 s5 (op1)
 s4 (op3)
 s3 (op3)
 s2 (op2)
 s1 (op1)
              6      12   18     24     30   36   42    48   54

                 6 min.                             6 min.

                  s1                s2’              s3
                                20 min.
                                20 min.
                  s5                                 s4
                 6 min.                             6 min.          tc=12 min
                                                                    tc’=6 min
 s5 (op1)
 s4 (op4)
 s3 (op4)
 s2” (op3)
 s2’ (op2)
 s1 (op1)
             6     12     18   24    30   36   42    48   54   60
    Group technology
   Which products are grouped to create a cell?
       Group technology facilitates the formation of
        product families.
   Group technology is a tool utilized in
    engineering and production departments to
    identify similar products.
       Economies of scale are achieved forming multi-
        product families rather than from a single part.
            Small companies can compete against bigger companies.
                 Offering seemingly unique products, but with numerous similar
        Group technology
   In some cases, alliances have taken place among
    different companies to manufacture new models
    sharing the development costs.
       The goal of group technology is to reduce design
        costs and production costs.
        Group technology
   Many of the gains of group technology come
    from design standardization.
       In some cases the components are designed in a way
        that allows them to be utilized in different products.
            the same screw for different fastening needs.
                 This screw is gauged according to the most critical point.
        Group technology – Product Family

   It is usually impractical to have a manufacturing
    cell for each product.
       investments would be bigger than the expected
            Grouping products into larger families eliminates this
        Group technology – Product Family

   The formation of families can suggest small
    design changes.
       If the changes do not affect the product functionality
        or to the client's necessities.
   Techniques to form product families.
       Based on direct visual inspection.
       Complex mathematical methods based on product
        features and shape.
        Group technology - Advantages
   Savings
       Up to 50% for the design time.
       Work-in-process by as much as 60%.
       Reducing time-to-market by 70%.
        Group technology - Advantages
   These benefits in production come from different
       Reduction in the number of dies required for
       Reducing purchasing cost by clustering and grouping
        orders of similar components.
       Scheduling simplification.
            Due to the reduction on the number of product types and
             the formation of self-managed cells.
         Group technology -
   Family classification consumes time and effort
       Does not always lead to profitable solutions.
            It can suggest erroneous changes in a product design.
   The installation of the manufacturing cells
    demands changes in the working habits.
       The responsibility is distributed among workers.
       Layout changes usually require large investments.
         Group technology -
   The duplication of some machines imply a low
    utilization of equipment.
       Traditional business management techniques penalize
        these reductions in production rates.
            They are based on productivity.
        Time study
   Time study can be defined as the methodology
    used to determine the standard time for an
       The time that a qualified worker needs to carry out a
        specific task, working in a normal rhythm during a
        work day.
        Time study
   The first historical works -> Fredrick Taylor’s
       Taylor used the most qualified worker to establish
        the standard working time.
            Educating the rest of workers to carry out the tasks in the
             same manner.
       Taylor received opposition from labor unions.
            Taylor decided to include two kinds of allowances.
                 Related to the workers fatigue.
                 Regarding variations among various worker capabilities.
        Time study
   Frank and Lillian Gilbreth added to the material
    started by Taylor.
       They divided tasks into fundamental elements.
       Chose the best worker for each task.
       The standard time was obtained by adding the best
        times of each task.
        Time study
   Years later, Lowry, Hayrard and Stegemerten, at
    Westinghouse company.
       Defined a normal-worker concept which is still used
                             Time study
                                                                                      Time studies lead to
                                                                                       establishment of the work
                                The 5S

                               operations     Jidoka
                                                                                      Standard time establishment
                                                          Workforce optimization

                                                                                       has other important utilities.
Visual Control

                   TPM                       functional
                                 flow         workers

                                                                                          The use for factory scheduling.
                  Kanban      Production
                                                                                          Providing standards for
                                                                                           incentives systems.
                              JUST IN TIME

                                                                                               Based on worker productivity.
                             Time study
                                                                                      Comparing different work

                                The 5S
                                                                                      Optimizing the number of
                                                                                       workers required to achieve a

                                                          Workforce optimization
Visual Control

                                                                                      Knowing the production costs.
                  Kanban                       SMED

                              JUST IN TIME
                             Time study
                              revolution                                             Four different methods to
                                                                                      determine the standard time.
                               The 5S

                                                                                         Time study with chronometer
                              operations     Jidoka
                                                                                          or videotape cameras.
                                                                                         Predetermined Time.
                                                         Workforce optimization
Visual Control

                                             workers                                     Work sampling.
                                                                                         Normalized times.
                  Kanban                      SMED

                                                                                     The first two methods are the
                             JUST IN TIME
                                                                                      most used.
     Time study - Chronometer or
     videotape camera
   Obtain the standard time for an operation by
    means of direct task observation.
       Recording the time is carried out with a stop
        watch (chronometer) or a camcorder.
        Time study - Study preparation
   It is necessary to clarify that the goal is to
    determine the standard time, not the time that the
    worker is really using during the observation.
       Workers typically speed up the process when they
        are being watched.
            Once this standard time is set, it can be compared with the
             time typically required to carry out the operation.
            The deviation between the times can be used for future
        Time study - Study preparation
   It is necessary to become familiarized with the
    process or task being studied.
       Develop a layout of the working environment.
   Determine the work cycle being studied.
       Since significant variability may take place when the
        same event happens again.
        Time study - Study preparation
   Time study is not only a technical problem of
    measuring the time.
       Human behavior enters the process and the operator
        can speed up or slow down.
       Understanding and assessing the operator is a basic
        requirement for a successful time study.
        Time study - Study preparation
   Technical knowledge is only a 25% of the
    requirements for a time analyst.
       Formulate questions in a polite manner.
       Inform to the worker that the study will be used as
       Convince the workers to contribute in the study.
   The worker should neither be criticized nor
    corrected while the study is being carried out.
       These usually lead to an erroneous study.
        Time study - Data acquisition
   Use traditional stop watches.
       Special chronometers (called minute decimal
   A time study should be broken in working
       Determine the beginning and the end of each one.
        Time study - Data acquisition
   Distinguish the following element categories.
       Repetitive and casual (non-repetitive) elements.
       Constant and variable elements.
            Variable -> depends on a product characteristic.
       Identify accidental elements.
       Separate machine elements from worker elements.
            A resource should not be penalized when the other resource
             is busy.
    Time study - Data acquisition
   Separate unnecessary and essentials movements.
   Identify simultaneous movements.
        Considered the longest time within them.
Time study - Data acquisition
   Two different methodologies for data
       Snapback method.
            The chronometer is stopped and returned to zero at
             the end of each task.
       Continuous timing.
            The time is presented in an accumulate way.
            This procedure is better than the previous one.
                 Mainly if the videotape is used.
Time study - Data acquisition
   Number of cycles to study.
       There will be variations among times.
       Depends on the duration of the elements and
        also on the accuracy required.
             Usually are taken 10 readings (n’).
                    n'  x 2    x 
        n   40                             
                           x                
                                             
     Time study - Standard time

   The first stage is to eliminate the measurements
    due to accidents, mistakes, etc.
   Observed time (OT)
       The average of the rest observations.
     Time study - Standard time

   OT should be corrected taking into account two
    factors .
       The speed at which the worker has done the task
        when the study was performed.
       The possibility of maintaining the same working
        speed during the whole day.
     Time study - Standard time

   A normal speed.
       The time that a normal worker can reach and
        maintain during a theoretical working day.
            Without additional fatigue.
       The companies usually demand, comparing to
        the normal, a higher working speed.
               Normal speed   Rhythm type or activity
                   100                    133
                   60                      80
                   75                     100
        Time study - Standard time
   Factors which are necessary to take into
       Some of the factors do not depend on the worker.
            Changes in the material quality.
       Other factors are exclusive of the worker.
            The worker's attitude regarding organization or
             professional know-how.
        Time study - Standard time
   The analyst should fix a subjective value of
    the observed working speed.
       Called the activity factor or AF.

                   observed speed
        NT                             OT  AF  OT
               rhythm speed or activity
         Time study - Standard time
         establishment         ST  A  NT

   Allowances (A).
       Personal necessities vary between 5% and 7%.
            Resting and recovering from exhausting tasks.
       Basic fatigue -> 4%.
            Weigh lifting, environmental conditions.
       Unforeseen events.
       Special process characteristics.
         Time study - Standard time
         establishment         ST  A  NT

   A fixed factor (A) is frequently used
       Due to the complexity of determining the value of
        all the suitable allowances, .
       Oscillates between 13% and 15%.
        Time study - Predetermined time

   Determine the standard time of an operation that
    does not yet exist.
       If the operations could be broken down in a limited
        number of elementary tasks…
            It would be possible to set the standard time of an operation
             in a simple way.
   There are a limited number of basic movements
    for workers.
       Their analysis and study are carried out by
        predetermined time systems.
         Time study - Predetermined time
   Predetermined systems have the advantage of
    leading to more coherent standard times.
       They are very difficult to implement.
       Working tables can be very complex.
       Do not eliminate the necessity of using the
            Machine manufacturing times and waiting times are not
             included in the tables
         Time study - MTM System

   MTM (Method Time Measurement).
       Covers generic movements of a person.
            Release, reach, move, turn & apply pressure, grasp,
             position and disengage.
       Three additional movements that are also included.
            Two eye movements.
                 Travel and focus.
            A upper body movement.
       13 movements that belong to the body.
         Time study - MTM System
   MTM (Method Time Measurement).
       The combined movements and simultaneous
        motions are also tabulated.
       Time units -> TMU (Time Measurement Unit).
            1 TMU = 0,036 secs.
   Simplified MTM system (MTM-2).
       Leads to more accurate solutions with an error of
Leveling production
   Leveling production is a prerequisites
    required for a cell layout transformation.
       Corresponds to the production planning and
        scheduling strategy.
   It is included in both the Just-in-time and
    the 20 keys (key number 16) for lean.
   To explain this concept Tomo Sugiyama uses a
    military example.
   The Battle of Nagashino.
       Nobunaga opposed Takeda.
            Nobunaga headed a thousand soldiers with muskets.
            Takeda commanded a traditional army cavalry.
       Takeda hoped to be able to attack Nogunaga while
        the muskets were being loaded.
            He was not able to get in while the muskets were being
             loaded, and Takeda lost the battle. Why?
   Batalla de Nagashino.
       Nobugana’s victory was due to a strategy that he
            He divided his army into three parts so that there was
             continuous firing.
            This strategy allowed 1/3 of his troop to be ready at all
            A third of the soldiers were always firing at Takeda’s
                 Takeda did not find the right moment to attack
        Leveling production

   Nobunaga’s approach can also be applied to
    factory production.
   In mass production systems, it is possible to
    calculate the takt-time.
       Each product is manufactured in an independent
        production line.
       Production scheduling is not affected by only product
        leveling, but with fulfilling customer due dates.
         Leveling production
   Initial strategy for most
       Carry out traditional constraint-
        based monthly planning to
        satisfy customers demand.
            A large amount of inventory is
             produced, maintained and stored.
    Leveling production
   If daily planning is
       The amount of
        generated inventory
        would be 20 times
        Leveling production
   Leveling production.
       Nobunaga’s approach.
            Leads to “constantly firing”
             different products.
       This tool forces a company to
        change their production
        scheduling strategy.
   Leveling production calculates
    the takt-time for each product.
Leveling production
   The development of a feasible sequence that
    satisfies the demand is quite complex.
       In the example presented above, it is possible to
        find a proper sequence.

       If this sequence is repeated 10 times, it fulfils
        the demand.
Leveling production
   Generally it is difficult to obtain a feasible
    (or optimal) solution when manufacturing
    different products.
       Production planning and scheduling in the
        factory should be leveled.
            If cell layout has not been properly implemented,
             level production is not possible.
        Leveling production
   Leveling production forces the suppliers to level
    their manufacturing processes.
       Otherwise, they will need to store large quantities of
        finished products to satisfy the demand.
            This manufacturing strategy has created one of the main
             obstacles to the Just-in-time.
                 The supplier owns the inventory until the assembly plant draws
                  items for assembly.
        Leveling production
   Prerequisites needed in leveling production.
       Repetitive production.
       Excess of capacity in productive resources.
       Fixed production for, approximate, a time horizon of
        one month.
       High inventory costs.
       Low resource costs.
       Multifunctional workers.
       Short set-up times.
         Multifunctional workers
   Until the 1960s the standard was for each
    machine to have a dedicated worker ->
       The main productivity concern for a company.
         Multifunctional workers
   Today’s market demands workers that are
    familiar with more than one process.
       Production workers need to carry out operations that
        may involve multiple departments.
            Quality and maintenance tasks.
1                 11 12            20                                                   revolution
         7                16
                                        Multifunctional                    Poka-Yoke
                                                                                         The 5S


                                                                                                                   Workforce optimization
    17                         8

                                                          Visual Control
         18               15                                                 TPM

              19 10 13                                                                                 workers

2                                  3
                                                                            Kanban                      SMED

                                                                                       JUST IN TIME

                     Multifunctional training has become a
                      standard for today’s factory worker.
                     Multifunctional workers are an
                      important key in the Just-in-time
                      philosophy as well as in the 20 keys
                      (key number 15) for Lean.
        Multifunctional workers - Task
   Multiple advantages.
       Reduction in work-related accidents.
       Improves the relationships among labors.
       Facilitates knowledge sharing.
       Uncover expert workers in each task.
            Should instruct other less skilled workers.
        Multifunctional workers - Task
   Training programs.
       Used to create comfortable learning environments.
       Promote other employees to self-improvement.
       incentives to workers that shown an interest in
        learning and sharing their knowledge.
       Always supposes a reduction in the company’s
        production capacity.

                                                                            The 5S

                                                              Poka-Yoke                   Jidoka

                                                                                                      Workforce optimization
        Workforce optimization

                                             Visual Control
                                                                TPM                      functional
                                                                             flow         workers

                                                               Kanban                      SMED

                                                                          JUST IN TIME

   Is a tool that is part of the Just-in-time philosophy
   The goal of this tool is to define how many
    people are necessary to make what it is necessary
    to make.
       Manufacture with the minimum number of workers.

                                                                                   The 5S

                                                                     Poka-Yoke                   Jidoka

                                                                                                             Workforce optimization
        Workforce optimization

                                                    Visual Control
                                                                       TPM                      functional
                                                                                    flow         workers

                                                                      Kanban                      SMED

                                                                                 JUST IN TIME

   One of the optimization principles is not to assign
    a fixed number of workers to a line.
   Multifunctional workers.
       It is possible to use the available workforce in the best
        possible way.
        Workforce optimization -
   Supposing a cell formed by five workstations.
       Tasks can be redistributed so that the need of one
        workstation is eliminated.
   Once achieved the first objective it is time to
    reduce the workforce by means of a better tasks
    assignment.                              Takt-time

                                1   2    3      4        5


                                1   2    3      4        5
Workforce optimization -

    1     2   3    4   5


    1     2   3    4   5

   After redistributing the tasks, it is
    important to improve the task by
    eliminating a second workstation.
       Instead of distributing the work among
        the four workstations.
         Workforce                       Part movements

         optimization                         Worker
                                                          Net operation

   The needed time to carry out a task
    can be decreased by eliminating
    waste and operations that do not add
    any value to the product.
       This is the way to eliminate the need of
        a fourth worker in the presented cell.
       There are method improvements tools
        that will be analyzed in a later chapter.
In this chapter the methodology and the
requirements for cellular layouts’ design have
been developed. U-shaped layout has been
chosen as best cell design although this layout
requires multifunctional workers in order to be
efficient. In addition, this chapter has presented
some methodologies such as time study and
group technology that must be used to
effectively carry out this project.

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