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Lesson 3 Layout & Flow
Sandwich making
'If you were making a sandwich for a friend how would you do it?
'If you were making sandwiches for a whole group of friends who were due to arrive in an hour’s time, how would your process change?‘
'If you were making 5,000 sandwiches a day for a supermarket, how would you wish to organize the production system?'
Sandwich making
Sandwich for a friend - What kind of sandwich would they want (limited only by the availability of ingredients in the kitchen), when do they want it? (it could be made to order), and how much it could be customized (more salt and pepper)
Whole group/1hour arrival (You would butter all the bread together, standardize the products to some extent, and so on).
‘Making 5,000 sandwiches a day for a supermarket?'(would need to use an assembly line or process, etc.).
Volume & Variety
Layout and flow cannot be discussed without first considering : The product volume and variety The type of process to be employed
These factors are inextricably linked
Project process
Jobbing process
Batch process
Mass process
Continuous process
Fixed position layout
Process layout
Cell layout
Product layout
The physical position of all transforming resources
The flow of the operation’s
transformed resources
Process type
Basic layout type
Detailed design of layout
Volume and variety
Strategic performance
objectives
Decision 1
Decision 2
Decision 3
How decisions might be connected (Slack2004)
Volume & Variety
Product volume – quantity of units produced
Product Variety – is the variation in products (SKU’s)
Product volume and variety is affected by the type of business and the market demand for products
Volume-Variety Dilemma
Low VOLUME High
Hig
hV
AR
IET
YL
ow
Not possible?
Not viable?
Accepted continuum for processes
Volume & Variety
Product volume and variety have a big influence on process design.
The two dimensions normally go together: Low volumes operations normally have a high
degree of product variety. [automotive component supplier]
High volume operations normally have a low degree of product variety.[canning plant]
The same organisation can have different parts of the operation organised differently – [large automotive OEM]
Volume/Variety is seen as having a large Influence upon the process type deployed
Volume & Variety
Process types in manufacturing are generally considered as: Project Processes Jobbing Processes Batch Processes Mass Processes Continuous Processes
The volume/variety position points to the most appropriate process
VolumeLow High
Var
iety
Lo
wH
igh
Project
Jobbing
Batch
Mass
Contin--uous
Manufacturing Process Types
Process types are designed to
cater for the volume /variety
mix
Notice how process types
overlap!
Project Processes
One-off, complex, large scale, high work content “products” e.g. construction projects
Specially made, every one customized i.e. a project!
Defined start and finish: time, quality and cost objectives
Many different skills have to be coordinated Fixed position layout, resources brought to
product
Jobbing Processes
Also deal with high variety / low volume Very small quantities: “one-offs” Specially made. High variety, low repetition e.g. bespoke
suits Skill requirements are usually very broad Each job has to share resources with other jobs Fixed position or process layout (routing decided by
jobbers)
Batch Processes
Higher volumes and lower variety than for jobbing
Standard products, repeating demand. But can make specials
Specialized, narrower skills Set-ups (changeovers) at each stage of
production Can use process or cellular layout, has a
predetermined planned routing
Mass (Line) Processes
Higher volumes than Batch Standard, repeat products Low and/or narrow skills No set-ups, or almost instantaneous ones Cell or product layout: a fixed sequence
of operations
Continuous Processes
Extremely high volumes and low variety: often single product
Standard, repeat products Highly capital-intensive and automated Few changeovers, if any, required Difficult and expensive to start and stop the
process Product layout: usually flow along
conveyors or pipes
The Product/Process Matrix
Low volumeLow
standardization
INCREASING VARIETY
Low volumeMultiple products
Higher volumeFew major products
High volumeHigh
standardization
PRODUCT CHARACTERISTICS
INCREASING VOLUME
Machine tool
maker
Custom furniture
maker
Automobile factory
Petro- chemical refinery
Jumbled flow
(jobbing)
Disconnected line flow(batch)
Connected line flow(mass)
Smooth flow (Continuous)P
RO
CE
SS
CH
AR
AC
TE
RIS
TIC
S
Random flow
(project)
Deviating from the ‘natural’ diagonal on the product-process matrix has consequences for
cost and flexibility
Project
Jobbing
Batch
Mass
Continuous
Professionalservice
ServiceShop
Massservice
None
None
Less process flexibility
than is needed so high cost
More process flexibility
than is needed so high cost
The ‘natural’ line of fit of process to volume/variety characteristics
Manufacturing operations
process types
Service operations process types
Variety
Volume
Layout and F low
•Layout decisions have to be carefully thought out:
•Size and complexity of equipment involved
•Cost
•Resource and time
•Disruption to production and customer service
•Complex and ‘muddled’ production flows can evolve if not designed and monitored properly
Layout
Product volume and variety dictate the processprocess type selected.
Areas of overlap exist where more than one type could be applicable – in this case operational objectives are used to make decision: cost, flexibility, known future areas of growth etc.
There are four broad layouts
Fixed position Process Cell Product
Layout
It is important to note that one process type does not mean one layout type.
There are normally choices associated with jobbing processes, batch processes and mass processes.
The nature of the basic layout types
Basic layout types
Manufacturing process types
Serviceprocess types
Fixedposition layout
Project processes
Process layout
Cell layout
Product layout
Jobbing processes
Batch processes
Mass processes
Continuous processes
Professionalservices
Service shops
Mass services
Project processes
Fixed Position
Transformed resources do not move Equipment and resources move to the product
which is stationery. Normally because product is too large, i.e.
shipbuilding, aero-engine, power generators. Or too delicate or fragile – heart transplant patient Main problems associated with this type of
operations are space and scheduling issues: Adequate space for groups to work without
interference Storage for materials and equipment Scheduling of material and people is key to FP
success
Fixed Position Example
Case study exercise – ALSTROM Pg 209 In groups of 2-3 discuss the set questions. Question 2 should be answered in relation to
performance metrics - Quality, Speed, Dependability. Flexibility and Cost
Alstrom Case Study
1. What factors at each site are likely to influence the layout?
Although the generators themselves will be relatively standard (though there are some variations) the installation of each will be slightly different where the generator interfaces with something else. The input of fuel, the output of generated electricity, and the way in which the generator is fixed to its foundations will all depend on the customer’s site. So, for example, the geometry of the site could be important. Very large pieces of the generator will have to be brought in and positioned in the site. If access to the site is restricted this may have to be done in a non-standard manner. Similarly, some of the services required by the product (compressed air, water, etc.) may not be available at the right place. These will also have to be provided.
Alstrom Case Study2. Parts of the product are assembled in the factory and transported to the site. What advantage does this give the company? The advantages to the company can be classed according to our normal five performance objectives as follows. Quality – Assembling large parts of the generator at the factory ensures that the job will be done by skilled staff who can make sure that any small problems in assembly are solved at the point where there are the appropriate facilities. Assembling parts on the site introduces more variables which may undermine the quality of the product. Speed – It will be faster to assemble parts in the factory using an appropriate layout than trying to do the same on the site where conditions are less predictable. Dependability – Again, the relatively predictable conditions of the factory will allow assembly to be carried out to a schedule. Assembly on site is prone to disruption from the other tasks taking place on the site. Flexibility – Standard parts, assembled at the factory, can be used for more than one customer. So, for example, if one part, when it gets to the site, is found to be unsatisfactory another one can be rushed to it at short notice. Cost – Making many of the same part in the factory (even if the part is fairly large) is obviously cheaper than assembling everything on site.
Process Layout
Resource types dominate layout decision Similar process are located together – for
convenience or utilisation Parts are routed through the operation based
upon their requirements Flow patterns are different and complex Control and visibility is also an issue Example of use – production of aero-engine
parts – many different processes involved.
Cellular Layout
Where all the required resources are available in one area to meet the processing needs.
Can be of the product or process layout type.
After completion the product may be finished or go to another cell.
Cells attempt to bring order to the product flow
Process Layout Cellular Layout
Product Layout
Each product follows the same route
Can also be known as flow-line
Flow is clear predictable and therefore offers visibility and ease of control.
Products produced are standardised (although small variations are possible) – but flow route is the same.
Examples – car assembly, electronic goods etc.
Advantages and disadvantages
Fixedpositionlayout
Processlayout
Celllayout
Productlayout
Disadvantages
Advantages
Very high product and mix flexibility.
Product/customer not moved.
High variety of tasks for staff.
Very high unit costs.
Scheduling space and activities can be difficult.
High product and mix flexibility.
Relatively robust in the case of disruptions.
Easy to supervise.
Low utilization.
Can have very high WIP.
Complex flow.
Can give good compromise.
Fast throughput.
Group work can result in good motivation.
Can be costly to rearrange existing layout.
Can need more plant.
Low unit costs for high volume.
Opportunities for specialization of equipment.
Can have low mix flexibility.
Not very robust to disruption.
Work can be very repetitive.
Next Week
No tutorial sessions on Monday 15th October
Answer SAQ for Unit 1 - Lesson 3 Read Unit 1 lesson 4 of study guideLAYOUT DESIGN TECHNIQUES – LINE
BALANCING
Lesson 3 Self Assessment Questions
Lesson 3 Self Assessment Questions
Lesson 3 Self Assessment Questions
Lesson 3 Self Assessment Questions
Lesson 4 Layout Design Techniques:
Line Balancing
Last Week
Discussed volume & variety Processes – Project, Jobbing, batch,
mass & continuous Looked at layouts - Fixed position,
cellular, process and product
This Week
Layout Design Techniques Focus on Product layout Cycle time Line Balancing
Product Layout
Transforming resources located for the convenience of the transformed resources
Product/customer/information follow a pre-arranged route
Sequence of activities matches the sequence in which process’s have been located
Detailed Design - Product Layout
Key decisions are concerned with ‘what to place where’ – in terms of what to allocate to each of the workstations.
This is termed line balancing Other key questions are:
What cycle time is needed? How many stages are needed? How should the layout be balanced? How should the stages be arranged?
Some definitions – (ch4 Slack) Cycle time – the average time for units of
output to emerge from the process
Throughput time – the time for a ‘unit’ to move through the process
Work Content – the total amount of work required to produce a unit of output
WIP – work in progress
Detailed Design - Product Layout
Cycle time = time available No.of units to be processed
Suppose a bank is designing an operation to process mortgage applications. The number to be processed per week= 160 and the time available for processing = 40 hours
Cycle time = 40 = 1 hr = 15 minutes 160 4
Detailed Design - Product Layout
Number of stages req. = work content required cycle time
Suppose the back in the previous example calculated the totalwork content to process a mortgage application to be 60 minutes. Cycle time = 15 mins
Number of stages = 60 = 4 stages
15
Detailed Design - Product Layout The previous example assumed that 15mins. of work time
was allocated equally to each of the 4 stages.
This can be almost impossible in practice and some imbalance results
The effectiveness of the line balancing is measured by ‘balancing loss’
Balancing loss - is that proportion of the time invested in processing the product or service which is not used productively
Can lead to excessive stations being required
Lo
ad
Stage
Cycle time = 2.5 mins
An ideal ‘balance’ where work is allocated equally between the stages
0
0.5
1
1.5
2
2.5
3
1 2 3 4
Work allocated to stage
Idle time
Calculating balancing loss:Idle time every cycle =(3.0 - 2.3) + (3.0 - 2.5) + (3.0 - 2.2) = 2.0 minsBalancing loss = 2.0
4 x 3.0 = 0.1667 = 16.67%
Lo
adStage
Cycle time = 3.0 mins
2.32.5
2.2
3.0
But if work is not equally allocated the cycle time will increase and ‘balancing losses’ will occur
0
0.5
1
1.5
2
2.5
3
3.5
1 2 3 4
2.3 2.5 2.2 3.0
Calculation of Balancing Loss
The Plug and Play Excercise
STAGE 1
(10 secs)
STAGE 2
(50 secs)
STAGE 3
(15 secs)
STAGE 4
(15 secs)
1. WHAT WAS THE CYCLE TIME?
2. HOW LONG DID IT TAKE TO MAKE THE FIRST PLUG?
3. HOW LONG DID IT TAKE TO MAKE THE LAST PLUG?
Timing diagram
STAGE 1
STAGE 2
STAGE 3
STAGE 4
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
Start upFirst Plug Produced Second Plug Produced
90 secs 50 secs
START OF PRODUCTION
Timing diagram
STAGE 1
STAGE 2
STAGE 3
STAGE 4
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
Plug Produced Last Plug Produced
50 secs50 secs50 secs
Plug Produced
END OF PRODUCTION
Detailed Design - Product Layout
In Line balance calculations the initial start up situation is neglected and the cycle time is taken as the continuous rate of output
In this case 1 plug every 50 seconds Note – it is the value of the longest activity
(the bottleneck) Using this value the line balancing loss
can be calculated
The Plug and Play Excercise
STAGE 1
(10 secs)
STAGE 2
(50 secs)
STAGE 3
(15 secs)
STAGE 4
(15 secs)
Stage 1 10 secs Fit pins to plug
Stage 2 50 secs Get plug from stage 1 10secs
Fit screws and cable retainer 30 secs
Take plug to Stage 3 10 secs
Stage 3 15 secs Fit fuse and holder
Stage 4 15 secs Inspect and fit top cover0
10
20
30
40
50
60
1 2 3 4
40 35 35
CYCLE TIME = 50 secs
WORK CONTENT = 90 secs
Idle time = (50-10)+0+(50-35)+(50-35)
= 40+0+35+35 = 110 secs
Balance loss = (110/4*50)*100 = 55%
Karlstad Kakes ExerciseConsider Karlstad Kakes (KK) a manufacturer of speciality cakes which has recently obtained a contract to supply a major supermarket chain with speciality cake in the shape of a space rocket. It has been decided that the volumes required by the supermarket warrant a special production line to perform the finishing, decorating and packing of the cake. This line would have to carry out the elements in the precedence diagram shown on the next slide.
The initial order from the supermarket is 5000 cakes a week and the number of hours worked by the factory are 40 hrs/week
Element listing and precedence diagram for Karlstad Kakes
Element - - De-tin and trim 0.12 mins
Element - Reshape with off-cuts 0.30 mins
Element - Clad in almond fondant 0.36 mins
Element - Clad in white fondant 0.25 mins
Element - Decorate, red icing 0.17 mins
Element - Decorate, green icing 0.05 mins
Element - Decorate, blue icing 0.10 mins
Element - Affix transfers 0.08 mins
Element - Transfer to base and pack 0.25 mins
Total work content = 1.68 mins
a
b
c
d
e
f
g
h
i
a b c d
e
f g
h
i0.12 mins
0.30 mins
0.36 mins
0.25 mins 0.05 mins
0.17 mins
0.10 mins
0.08 mins
0.25 mins
No of units required - 5000 cakes per weekTime available - 40 hrs per week
Cycle Time = 40x60/5000 = 0.48 mins
Number = work content/ cycle time of stages
= 1.68/0.48 = 3.5
PRECEDENCEDIAGRAM
Allocation of elements to stages and balancing loss for Karlstad Kakes
a b c d
e
f g
h
i0.12 mins
0.30 mins
0.36 mins
0.25 mins 0.05 mins
0.17 mins
0.10 mins
0.08 mins
0.25 mins
Stage 1 Stage 2 Stage 3 Stage 4
0
0.1
0.2
0.3
0.4
0.5
0.6
1 2 3 4
Cycle time = 0.48 mins
Idle time every cycle = (0.48 - 0.42) + (0.48 - 0.36) + (0.48 - 0.42) - 0 = 0.24 minsProportion of idle time per cycle = 0.24 = 12.5%
4 x 0.48
MAXIMUM CYCLE TIME = 0.48 minutes
BUT MUST NOT COMPROMISE PRECEDENCE
0.42 0.36 0.42 0.48
Stage Arrangement
How could the Plug and Play scenario be improved?
Stage 1
Stage 2
Stage 3
Stage 4
Stage 1 Stage 2 Stage 3 Stage 4
SHORT AND FAT
LONG AND THIN
10 50 15 15
90
90
90
90
One plug every 22.5 secs
One plug every 50 secs
SHORT AND FAT
More flexible –
Volume -as demand varies shut down individual stages
Mix – Individual stages can specialise
Highly Robust – Any one stage fails other three carry on
Less Monotonous work
LONG AND THIN
Controlled flow
More efficient – In real situation build operations are more complex. If each stage is performing a small part of the job can be made highly productive through the elimination of waste time
Stage Arrangement
Two main options: Long thin line Short fat line
Advantages of long thin: Easy to manage flow of materials Simplified material handling More efficient operation
Advantages of short fat: Higher mix flexibility Higher volume flexibility Higher robustness Less monotonous work
Next Week
Answer SAQ for Unit 1 - Lesson 4 ready for tutorial sessions on Monday
29TH October
LAYOUT DESIGN TECHNIQUES – PRODUCTION FLOW ANALYSIS
Tutorials
Room RV307
Group 1 11-0 to 11-35pm Group 2 11-40 to 12-15 pm Group 3 12-25 to 13-0pm
See list to find out which group you are in
Line Balancing Exercise SMC Ltd are developing a new process. The process has the
following tasks and linkages.
Activity Time (sec) Predecessor
A 12
B 8 A
C 10
D 16 C
E 20 B,D
F 9
G 15
H 11 E,F,G
I 8 H
J 15 I
K 8 I
L 13 J,K
[adapted from Martinich, 1997]
Line Balancing Exercise
Your task is to : Calculate the max cycle time if 1100 units
are to be produced/8 hour day. Calculate the minimum number of
workstations. Design a line that minimises the number
of workstations. Calculate the actual cycle time,
production rate and efficiency
Self Assessment Questions
Line Balancing Case Study
Read the Weldon Case study on pgs 240-241. Working in groups of 2-3 answer the following
questions:
How many people will be needed to assemble the product, during (i) yr1 qtr 1 and (i) yr2 qtr 4. Comment upon the sales forecast profile.
Design a layout for production during yr 1 qtr 1, consider both the short fat and long thin options. Discuss the arguments associated with each model.
Line Balancing Exercise SMC Ltd are developing a new process. The process has the
following tasks and linkages.[Martinich, 1997]
Activity Time (sec) Predecessor
A 12
B 8 A
C 10
D 16 C
E 20 B,D
F 9
G 15
H 11 E,F,G
I 8 H
J 15 I
K 8 I
L 13 J,K
Line Balancing Exercise
Your task is to : Calculate the max cycle time if 1100
units are to be produced/8 hour day. Calculate the minimum number of
workstations. Design a line that minimises the number
of workstations. Calculate the actual cycle time,
production rate and efficiency
Product Flow Analysis
PFA is a technique for planning to change from a process oriented layout (functional) to one which is focused upon the product (cellular).
By finding product families of work centre
groupings it simplifies material flow systems.
Rank Order Clustering (ROC) is a widely
used technique for this purpose. It uses a binary system based on 2s to give each row and column an identity based upon its content.
It traces the flow of components from
machine to machine and helps to form families and cell designs.
The accuracy of the product data is
important - why
Product Flow AnalysisTutorial Example (1)
Product no4 10 11 12 14
1 1 1 1
2 1 1
Resource 3 1 1 1
4 1 1 1
5 1
6 1 1 1 1 1
7 1 1
8 1 1
9 1 1 1
10 1 1 1
11 1 1
12 1 1 1
13 1 1
14 1 1
Product Flow AnalysisTutorial Example (2)
16 8 4 2 1Product no
4 10 11 12 14
1 1 1 1 1 22
2 2 1 1 9
4 Resource 3 1 1 1 22
8 4 1 1 1 22
16 5 1 1
32 6 1 1 1 1 1 31
64 7 1 1 9
128 8 1 1 18
256 9 1 1 1 22
512 10 1 1 1 22
1024 11 1 1 9
2048 12 1 1 1 22
4096 13 1 1 9
8192 14 1 1 9
2989 13410 2861 2989 13426
Allocate row values
Product Flow AnalysisTutorial Example (3)
(1)Sort by row
(2) Total columns
16 8 4 2 1Product no
4 10 11 12 14
1 6 1 1 1 1 1 31
2 1 1 1 1 22
4 Resource 3 1 1 1 22
8 4 1 1 1 22
16 9 1 1 1 22
32 10 1 1 1 22
64 12 1 1 1 22
128 8 1 1 18
256 2 1 1 9
512 7 1 1 9
1024 11 1 1 9
2048 13 1 1 9
4096 14 1 1 9
8192 5 1 1
255 7937 127 255 16129
Product Flow AnalysisTutorial Example (4)
Sort by column
16 8 4 2 1Product no
11 4 12 10 14
1 6 1 1 1 1 1 31
2 1 1 1 1 28
4 Resource 3 1 1 1 28
8 4 1 1 1 28
16 9 1 1 1 28
32 10 1 1 1 28
64 12 1 1 1 28
128 8 1 1 12
256 2 1 1 3
512 7 1 1 3
1024 11 1 1 3
2048 13 1 1 3
4096 14 1 1 3
8192 5 1 1
127 255 255 7937 16129
Product Flow AnalysisTutorial Example (5)
Key Questions:
1. What are the cells you have suggested? i.e. part no’s and resources in each.
2. Why have you come to this decision?
3. Are there any issues outstanding – if so how can they be resolved?
