session-8b line balancing

8/3/2019 Session-8B Line Balancing

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M.S Ramaiah School of Advanced Studies - Bangalore 1


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Session Objectives

Line Balancing. Current State VSM and C cle Time. Standardized Work. Load Levelin Hei unka



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Line balancing is the process through which you evenlydistribute the work elements within a value steam in order t

.Line balancing helps optimize the use of personnel; itbalances workloads so that no one is doing too little or toomuch.

Keep in mind that customer demand may fluctuate and

line



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Line Balancin

.

The best tool to perform this task is an operator balancechart.

The operator balance chart is a visual display of the work elements, time requirements and operators at each work station. It is used to show im rovement o ortunities b visually displaying each operations times in relation to TaktTime.



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Step 4 - Map the current state

Understanding the ..current process C cle time Process communications Peo les work standards Machine / equipment capacity & so on



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Line Balancin

Typically, some operations take longer than others,

leaving operators with nothing to do while they wait forthe next part. On the other hand, some operations maynee more an one opera or. ne a anc ng s eprocess through which you evenly distribute the work

time. Line balancing helps optimize the use of personnel; it balances workloads so that no one is doingtoo little or too much. Keep in mind that customerdemand may fluctuate and changes in takt time often


ma e t necessary to re a ance a ne.


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Line Balancin

state. The best tool to perform this task is an operatorbalance chart. The o erator balance chart is a visualdisplay of the work elements, time requirements, and

operators at each workstation. It is used to showimprovement opportunities by visually displaying eachoperations times in relation to takt time and total cycle

e.



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C cle TimeCycle time is the time that elapses from the beginning of an operat on unt ts comp et on n ot er wor s, t s t eprocessing time.

Dont confuse this measure of processing time with takt

time, which is the measure of customer demand.Total cycle time is the total of the cycle times for eachindividual operation in a value stream.

This is also referred to as total value adding time (VAT),because this is the time durin which value is actuall


being added to the material as it flows through the process.


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C cle Time

7

A

6

4

5

96

78

1 2 3

3 421 5

7

B

6 5

1 2

4

3

9

3 46

78

21 5



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C cle TimeC

49

3 4

6

78

21 5

1 2 3

CustomerDemand

Total ProductCycle Time

Daily AvailableTime

TaktTime

Number of OperatorsRequired

A 500 60S 30,000S 60S 1

B 1,000 60S 30,000S 20S 2

C 1,500 60S 30,000S 30S 3


U shaped cell Increase flexibility.


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C cle Time



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C cle Time



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C cle Time



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C cle Time

elsewhere. The conventions of lean thinking suggest that a decimalless than or equal to 0.5 (in this case, 0.36) is a good indicator thatthis is a realistic goal. In the improved process, each of the three

make one part within the 60-second takt time (or a small batch

within the time calculated for pitch). Thus, total cycle time must beess an or equa o secon s.

One solution would be to combine operations A and B, and C and, ,

perform each of the three sub processes (A-B, C-D, and E) in 60seconds or less (see Figure 3-11).



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value stream, workers must be able to produce to takttime and achieve consistent cycle times for the work elements assigned. You do not want one individual

achieving a 45 - second cycle time and a coworkerac ev ng a secon cyc e t me or t e same operat on.You want to standard size to the 45 second cycle time

way. This is accomplished by implementingstandardized work.



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Standardized work provides a basis for consistently high

levels of productivity, quality, and safety. Employeesdevelop kaizen ideas to continually improve these three

.standardized work:

or oge er w opera ors o e erm ne e mosefficient work methods and ensure that consensus isattained. This ma include reviewin the ro osed set of revised work elements with the entire group that will beusing them. Do not surprise people by unilaterally imposing


new standards and procedures.


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Use the Standard Work Combination Sheet Fi ure 3-

13) to understand how process cycle time compareswith takt time. This document displays the material andhuman workflow for a process. It specifies the exact

time for each sequence within an operation, including. ,operation can be kaizened (improved) to meet takt.This ma include allocatin some of the work elementsinto an operation that cycles faster than takt.



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Adhere to takt time, a critical unit of measurement for

stan ar ze wor . o not attempt to accommo ate c angesin takt time by making substantial changes in individualworkloads. When takt time decreases, stream line the work and add employees as necessary. When takt time increases,assign fewer employees to the process.



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When ou establish takt time, create work cells, and

implement standardized work, it is likely that you willalso want to increase the variety of products flowingthrough the cells. Such flexibility requires toolingchanges that do not disrupt continuous flow. The means

method. QCO originates from a methodology calledsin le-minute exchan e of die SMED that wasdeveloped by Shigeo Shingo at Toyota.



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uick Chan eover

The need for QCO usually becomes obvious at one of two

1. Demand stage: slow changeover times present a majoro stac e to meet ng customer eman .

2. Continuous flow stage: implementing standardized

work underscores the need for faster changeover timesto reduce total cycle time and help balance operations.



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uick Chan eover3. Convert internal tasks to external tasks when possible;improve storage and management of parts and tools tostreamline external setup operations.

4. Streamline all setup activities by implementing parallel

operations (dividing the work between two or more people),us ng unc ona c amp ng me o s ns ea o o s,eliminating adjustments, and mechanizing when necessary.

ere y a ress ng t e o v ous t ngs, e prepar ng antransporting tools and equipment while the machine is still


, .


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In-Process Su er MarketsIn Process Su ermarkets

Where obstacles to continuous-,

process supermarket system. A

supermarket of work-in-processmay be necessary to ensure thatflow is possible. It is used when

t ere are mu t p e eman smade on a machine or a process.



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In-Process Su er MarketsToyota found the supermarket to be the best alternative forscheduling upstream processes that cannot flow continuously.As you improve flow, the need for supermarkets may

.the ideal state, as are pitch, buffer inventory, and safety

inventory. You will not achieve your ideal state overnight, butkeep the takt image alive and continually work toward thatideal state.

The supermarket system works best when there is a highdegree of commonality between parts. Refer to the PQ


analysis or part-routing matrix you created in Step 2 examine

part families.


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an an ystem

Kanban is at the heart of a pull system. Kanbans arecards attached to containers that store standard lots zes. en t e nventory represente y t at car sused, the card acts as a signal to indicate that more

. ,only when needed, in the exact amounts needed.



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The Origin of Kanban

In Japanese, kanban meanscard, billboard, or sign.Kanban refers to the inventorycontrol card used in a ullsystem. Kanban also is usedsynonymously to refer to the

developed for use within theToyota Production System



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Kanban S stemKabans manage the flow of material in and out of supermarkets,

nes an ce s. ey can a so e use to regu ate or ers rom t efactory to suppliers (see Figure 3 14).


gure - . ow a an an system contro s mater a ow


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Kanban S stem1. Customer orders 20 units (electronic transaction).

2. With drawl kanban for 20 units taken to finished goodssupermarket.

3. After shipper withdraws 20 units from the supermarket, takesproduction kanban for 20 units and drops it off at cell 2.

. e operator uses w t rawa an an to pu un ts ofrom in-process supermarket, pulls production kanban fromcontainer, and drops off at Cell 1.

5. Cell 1 operator uses withdrawal kanban to pull 20 units of rawmaterial from raw material supermarket, pulls signal kanban from


container and places it in a holder to be collected by supplier s truck

driver.


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If you lack a high degree of commonality between arts

and cannot use an in-process supermarket system, thenyou can work with the concept of a first-in, first-outane. rst- n- rst-out s an nventory

control method used to ensure that the oldest inventory- - .

useful in situations where multiple value streams meetbefore product customization, and before large-batch

operations where dissimilar parts go through an operationsuch as anodizing, welding, stamping, or painting (see


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nes


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An upstream operation cuts steel rods for a cell that makes

t ree s g t y erent ut re ate pro ucts. ne pro uctstarts with a 3 diameter rod that is 8 s long, the second

,third product starts with a 5 diameter rod that is 12s long.

Since the cell requires three different-sized rods, you couldestablish a FIFO lane to ensure that the rods are processeddownstream in the order that they were cut.

On the other hand, if each of the three products were madefrom the same-sized steel rod, you could establish an in-


process supermar et rom w c parts cou e pu e w en

needed.

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Remember that a pull system is based on actual need, not

orecasts. usta n ng suc a system requ res you to sc e u eproduction and control inventory based on the needs of the

pull and continuous flow methods to initiate and signal all

other activities. If necessary, you may have to introducesupermarkets and /or FIFO in the value stream to enableyour production system to handle variations and mistakes.

,little or no changeover (ideally less than one minute), andreatest worker flexibilit . Often this will be an assembl


area.

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Review of the Various Levels of FlowWhen you plan the future state you will have to consider the best

.

Flow in the Ideal State (One-Piece Flow)

Advantages:

Absolute control over processes. Instant feedback on quality and safety issues.

Balanced workload.

Immediate reaction to system failure (machine, people, material).


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,

by which you can balance the pace of productiona ainst the ace of sales or takt time. There are twoways to accomplish this: paced withdrawal and heijunka


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Paced withdrawal is a s stem for movin small batches of

a product from one operation or process to the next, attime intervals equal to the pitch. Paced withdrawal is used

,meaning that all pitch increments will be identical.

- . ,customers usually want products in containers that hold astandard pack-out quantity. Paced withdrawal levelspro uc on y v ng e o a requ remen or a s orday into batches equal to a pack-out quantity. The pitchdetermines the frequency with which containers are


released to shipping.

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Heijunka is a so histicated method forplanning and leveling customer demandby volume and variety over the span of a

ay or s t. t ere s tt e or no pro uctvariation, you may not need this level of

.smaller lots or pure, continuous, one-piece flow, the demand for parts is subject

to sudden peaks and valleys. Large ordersmay immediately deplete inventory,


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Hei unka ma be the ke to establishin a tru lean ull s stem inyour facility if your product mix warrants it. Heijunka uses pacewithdrawal based on pitch, but breaks it into units based on the

. ,consider a value stream that makes five related products in

standard-pack quantities of 25, as shown in the table below.Product A B C D E

Daily requirement 300 200 200 50 50

Pack out quantity 25 25 25 25 25

# Of Kanbans 12 8 8 2 2


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In each case, the number of kanbans is determined by dividing thea y requ rement y t e pac -out quant ty. e tota a y requ rement

is 800 units, and the available production time over two shifts is 52,800seconds. This means that takt time e uals 66 seconds and itch e uals1,659 seconds (27.5 minutes):

Takt time = Available production time / Total daily quantity required

Takt time = 52,800 seconds / 800 units

Takt time = 66 seconds

Pitch = Takt time x Pack out quantityPitch = 66 seconds per unit x 25 units per container


tc = , secon s or . m nutes.

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So, every 27.5 minutes, 25 units must be released to

.

Over the course of the day, the value stream must turn out12 containers of A 8 containers each of B and C and w2containers each of D and E. In other words, the ratio of A:

B: C: D is 12:8:8:2:2. Reduced to its smallest terms, theratio is 3:2:2:0.5:0.5 or, for every t ree containers of product A produced, two containers each of products B and

.produced. The leveled production ratios are managedthrough distribution of kabans using a heijunka box,


explained in the next section

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Heijunka (Load Leveling)

understanding of customer demand and the effects of this demand upstream. Heijunka is not somethingthat you can put in place with a cosmetic lean effort: itrequires strict attention to the principles of sta zat on an stan ar zat on.


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The heijunka box, or leveling box, is a physical device usedto manage eve e pro uct on vo ume an var ety over a

specified time period. The load is leveled with

equipment. Kanban cards are placed in slots corresponding

to the pitch increments in which products are to be releasedto shipping and subsequently replenished.

In the heijunka exam le above, we determined that level

production could be achieved based on the following ratio:A: B: C: D: E = 3:2:2:0.5:0.5


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Product A is made during the first three pitch periods.

Product B is made during the next two periods.

Product C is made during the following two periods.

Since production is based on pitch, it would be impractical to make ahalf container of product D. Instead, it would make good sense to run A

- .helps sustain flow by minimizing changeovers.

After runnin D, ou would dedicate the next four itch eriods to

running two more containers of B and C respectively. Product E is made during the final pitch period of the first shift.


The pattern established above repeats during the second shift.

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Hei unka Load Levelin


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Note that by the end of the day, production requirements

ave een met. we ve conta ners o , e g t conta ners

each of B and C, and two containers each of D and E have.

Note created the table for the preceding example to show in

of different products is distributed in a balanced way overan entire day. A heijunka scheme is more commonly

represented as show in figure 3-17 (in reality, you mightfabricate a box with slots in which you place kanbans or a


oar on w c t e an ans are poste .

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In a lean transformation ou often discover in the course of performing line balancing that you can eliminate a workerfrom a target value stream and redeploy that person elsewhere.

,material handler, provided that he or she is qualified to assume

that role (see Runner Qualifications).The runner ensures that pitch is maintained. He or she covers adesignated route within the pitch period, picking up kanbancar s, oo ng, an componen s, an e ver ng em o e rappropriate places. If a heijunka box is used, the runnerremoves kanbans from it to use as visual work orders.


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Heijunka (Load Leveling)

a mailbox for the value stream, andthe runner is the mailman. If aheijunka box is not being used,then the runner picks up and

e vers parts rom store ocat onsas required to sustain efficient flow

.


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Runners play an important role in proactive problem solving. Becauset ey cont nuous y mon tor t e unct on ng o a ne or ce as we as

pitch (or takt time), runners are closely attuned to how well the valuestream is fulfillin customer re uirements. Normall , when a roblemoccurs, an operator immediately notifies a team leader or supervisorand the problem is addressed after it occurs. However, runners are in

large problems that seriously disrupt process flow.

Remember that levelin occurs after ou have achieved continuous

flow. It is a refinement of your lean design. You may find that specifictechniques implemented earlier will be eliminated as you successfully


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Identify Non Lean Conditions

After learning something about lean, you will begin to look at thevalue stream in a new way. As a first step in applying yourknowledge, start observing ways in which the manufacturingprocess is not lean, or could be improved. Ask yourself questions

about what ou are observin , such as: Does the floor layout promote waste-free of parts through theprocess?

Do you have a push system or a pull system? How do youcommunicate orders to the upstream process? How do you pass


components to t e ownstream process?

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Heijunka (Load Leveling) Are ou roducin lar e lots small batches or one- ieceflow?

Is customer demand being met? Are you working to takt time?Have you determined the pitch?

Is the work area messy and disorganized? Are you tolerating inventory, waiting, and other forms of waste?

How long are your changeover times?


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Summary

moved at the same rate.

theoretically determine the cycle time of materials coming fromupstream.

The process of balancing is ongoing and as such is another aspectof continuous improvement.


session-8b line balancing

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