Process Analysis

7/17/2019 Process Analysis

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Process AnalysisProcess Analysis

““ If you cannot describe what you are doing as a If you cannot describe what you are doing as a

process, you do not know what you are doing. process, you do not know what you are doing.””

W.E. DemingW.E. Deming



What is a process?

A process is a series of independent tasks that

transforms an input into output material of

higher value for the organization

Eamples!

". #onda transforms steel$ ru%%er$ and plastic into cars

&. 'cDonald(s transforms meat$ potatoes$ and saucesinto packaged food

). Dell transforms customer orders into P*(s



Process Analysis

+et(s look at the “%lack %o” in more detail,

Why do -e need to analyze the process?

/o identify inefficient tasks

/o spot possi%le effectiveness improvement tasks /o understand -here value can %e added

#o- can -e analyze a process? 'ap it0

What are the relevant performance measures?



Process 1lo- *harts

2raphical description of a process!

3 #olding!

4 5a- 'aterials$ 5'

4 Work in Process$ W6P

4 1inished 2oods 6nventory$ 126

3 1lo- of material or -ork

3 Processing step

3 Decision point



'aketoorder vs. maketostock

/ask " /ask &126

/ask " /ask &

Demand

6f demand is satisfied %y 126 then the system is make-to-stock $

other-ise it is a make-to order system

7ome eamples,

What are the tradeoffs?



4 What is its capacity? #o- many units per unit time go

through each task? /he process as a -hole?

4 What is the bottleneck ? Which production step limits the process capacity?

4 What is the throughput time? #o- long does it take to get

through the system?

Process Analysis! the performance measures

Assume a process is in place. What do -e need tomeasure in order to understand ho- efficient it is?

/ask " /ask & /ask )



#o- do -e measure capacity?

Cycle Time! Average time for completion of a unit at a

production step or process. Does not include -aiting.

'easured as time/unit

Throughput Rate! Average num%er of units processed over a

time interval. 'easured as units/time

"

*ycle /ime/hroughput rate 8

9ey

relationship

*apacity of a task is the physical limitation in terms of“ho- much can %e processed at this task”

*apacity 8 throughput rate



*omputing *ycle /imes

Processing a fixed amount of work

*ycle /ime = 7etup /ime + :;atch size< :/ime per unit<

;atch size

Eample! Producing "== cars. >n average$ production takes hours per car. 6t takes = hours to set up the production line.



*omputing *ycle /imes

7etup time!

" min

A ;

@uestion! What is the cycle time %et-een points A and ;

of the process$ if -e -ork in %atches of "=?

Production /ime!

&minunit



What is a %ottleneck?

Which task is the %ottleneck?

) unitshr unitshr & unitshr

Bottleneck is the

process stage with the

smallest throughput rate

(longest cycle time)



*apacity of a process

/he capacity of the process is!

minimum throughput rate at any of the stages

What is the capacity of this process?

) unitshr unitshr & unitshr



#o- do -e measure throughput time?

Throughput Time! Average time that a unit takes to go through

the entire process :including -aiting time<.

'easured as time

Work in Process(WIP)! Average num%er of units in system

over a time interval.

'easured as units

W6P

/hroughput rate/hroughput time 8

9ey

relationship

:+ittle(s +a-<



#o- do -e analyze a comple process,

". +ook at the process step %y step

&. Determine throughput rate :i.e. capacity< of

each step

). 6dentify the process bottleneck :smallest

processing rate$ or largest cycle time<.

B. /he capacity of the process is eCual to the

capacity of the %ottleneck



Eample ! hammer production process

Description

". Work %egins at the machining center. #ere t-o lines form

the heads of the hammers and place them in a %uffer.

&. #andles are attached at the assem%ly step.

). 1inished hammers are sent to the net stage$ -here they

are packed and shipped.

assem%ly pack and

ship

machining

machining

W6P W6P



Process Data!

4 machining! 7et up = min. B min per unit processing.

;atch size &==. 6dentical lines.

4assem%ly! 'anual %y t-o -orkers :no set up<. Eachhammer reCuires B= min processing. )B -orkers availa%le.

4 pack and ship! )= min set up$ & min per unit processing.

+ot sizes of "==.

assem%ly pack and

ship

machining

machining

W6P W6P

+et(s analyze the hammer process,



7tep "! 'achining

4 +ook at one line. &== units reCuire!

= &== × B 8 = minutes&== units

4 /he throughput rate is!&== = 8 =.&&F unitsminute

8 ").G) unitshour

4 ;ut -e have t-o identical lines$ so for the machining stepcapacity is & × ").G) 8 &F.&G unitshour.



7tep &! Assem%ly

4 " unit reCuires B= min processing time$ so the

throughput rate is!

" unit B= min 8 =.=& unitsmin

8 ". unitshr

4 )B -orkers availa%le$ %ut & -orkers are reCuired for

each unit$ so assem%ly capacity is!

"F × ". 8 &. unitshr



7tep )! Pack and ship

4 7imilar to machining!

)= "== × & 8 &)= min"== units

4 Pack H ship capacity is!

"== &)= 8 =.B) unitsmin

8 &G.=I units hr



#ammer process! -hat is the capacity?

Process 7tep *apacity :unitshr<

Machining &F.&G

Assembly &.=

Pack & hip &G.=I

Assembly is

the

bottleneck!



7ome voca%ulary, Buffering ! 9eep some inventory %et-een stages

= ""&

tar!ing ! 7toppage of activity %ecause of lack of material

Blocking ! 7toppage of flo- %ecause there is no storage place

" ==&

" "&&

" "



'ore Eamples..

*/ 8 )s */ 8 "s

126/ask " /ask &

+et(s study this maketostock system.

What is the capacity of the process?

What is the throughput time?

What is the average W6P?

6s any task starved or %locked?

Jote! Jo %uffer space %et-een stations$ so upstream

station has to -ait if do-nstream station is %usy



'ore Eamples..

*/ 8 )s */ 8 "s

126/ask " /ask &

/ask & starved for &s. each time.

/hroughput rate 8 &= unitsmin at /ask "$ G= unitsmin at /ask &

*apacity :throughput rate< of process 8 &= unitsmin

/hroughput time 8 B seconds 8 "" min

W6P 8 /hroughput rate /hroughput time

8 &= unitsmin "" min

8 ".)) units



'ore Eamples..

*/ 8 "s */ 8 )s

126/ask " /ask &


What is the throughput time?

What is the average W6P?


+et(s study this maketostock system!

Jote! Jo %uffer space %et-een stations$ so upstreamstation has to -ait if do-nstream station is %usy



'ore Eamples..

*/ 8 "s */ 8 )s

126/ask " /ask &

/ask " %locked for &s. each time.

/hroughput rate 8 G= unitsmin at /ask "$ &=unitsmin at /ask &

*apacity of process 8 &= unitsmin

/hroughput time 8 G seconds 8 =." min

W6P 8 /hroughput rate /hroughput time

8 &= unitsmin =." min

8 & units



'ore Eamples..

*/ 8 )s */ 8 )s

126

/ask " /ask &



+et(s study this maketostock assem%ly system!

Jote! Jo %uffer space %et-een stations

*/ 8 Bs

/ask )

*/ 8 &s

/ask B



'ore Eamples..

*/ 8 )s */ 8 )s

126

/ask " /ask &

*/ 8 Bs

/ask )

*/ 8 &s

/ask B

/asks " and & are %locked %y /ask ) for " second per product.

/ask B is starved for & seconds per product.

/he capacity of the process is " unitshour :limited %y /ask )<.

Process Analysis

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