Facility Design-Week 4
Material Flow Analysis
By
Anastasia L. Maukar
Flow Analysis
•
Factors that Affect the Flow Pattern
•
Flow Analysis Information
•
Flow Patterns
a. Flow within Workstations
b. Flow within Departments
c. Flow between Departments
•
Flow Planning
•
Measuring Flow
•
Types of Layout
a. Fixed Location
c. Group Technology
b. Product
d. Process
e. Hybrid
•
Flow Dominance Measure
2
Factors that Affect the Flow Pattern
•
•
•
•
•
•
•
•
•
•
Number of parts in each product
Number of operations on each part
Sequence of operations in each part
Number of subassemblies
Number of units to be produced
Product versus process type layout
Desired flexibility
Locations of service areas
The building
....
3
Flow Analysis Information
•
•
•
•
•
•
•
Assembly Chart
Operation Process
Chart (OPC)
Multi-Product Process
Chart (MPPC)
String Diagram
Process Chart
Flow Process Chart
Flow Diagram
•
•
•
•
•
From-to Chart/Travel
Chart
Triangular Flow
Diagram
Activity Relationship
Chart (ARC) dan
Activity Relationship
Diagram (ARD)
Procedure Chart
Critical Path Network
4
Assembly Chart
It is an analog model of the assembly process.
Circles with a single link denote basic
components, circles with several links denote
assembly operations/subassemblies, and
squares represent inspection operations. The
easiest method to constructing an assembly
chart is to begin with the original product and to
trace the product disassembly back to its basic
components.
5
Operations Process Chart
By superimposing the route sheets and the
assembly chart, a chart results that gives an
overview of the flow within the facility. This
chart is operations process chart.
6
Multi-Product Process Chart
This chart is a flow process chart containing
several products.
7
String Diagram
8
Flow Process Chart
This chart uses circles for operations,
arrows for transports, squares for
inspections, triangles for storage, and the
letter D for delays. Vertical lines connect
these symbols in the sequence they are
performed.
9
Other Flow Process Chart
10
Flow Diagram
It depicts the probable movement of
materials in the floor plant. The
movement is represented by a line in
the plant drawing.
11
From-To Chart
This chart is a matrix that contains
numbers representing a measure
(units, unit loads, etc.) of the material
flow between machines, departments,
buildings, etc.
12
Triangular Flow Diagram
13
Flow Patterns: Flow within Workstations
Motion studies and ergonomics considerations are important in establishing
the flow within workstations. Flow within workstations should be:
•
•
•
•
Simultaneous: coordinated use of hands, arms and feet.
Symmetrical: coordination of movements about the center of the body.
Natural: movements are continuous, curved, and make use of momentum.
Rhythmical and Habitual: flow allows a methodological and automatic
sequence of activities. It should reduce mental, eye and muscle fatigue, and
strain.
14
Flow Patterns: Flow within Departments
•
•
The flow pattern within departments depends on the type of department.
In a product and/or product family department, the flow follows the product
flow.
1 machine/operator
2 machines/operator
1 machine/operator
More than 2
machines /operator
1 machine/operator
15
Flow Pat.: Flow within Departments (cont.)
• In a process department, little flow should occur between
workstations within departments. Flow occurs between
workstations and aisles.
Uncommon
Aisle
Aisle
Aisle
Aisle
One way
Aisle
One way
Dependent on interactions among workstations
available space
size of materials
16
Flow Pat.: Flow between Departments
•
•
Flow between departments is a criterion often used to evaluate flow within a
facility.
Flow typically is a combination of the basic horizontal flow patterns shown
below. An important consideration in combining the flow patterns is the location
of the entrance (receiving department) and exit (shipping department).
Straight
Simplest. Separate
receiving/shipping
crews
U flow
Very popular.
Combine receiving
/shipping. Simple to
administer
Serpentine
When line is too long
L flow
Similar to straight.
It is not as long.
Circular
flow
Terminate flow.
Near point of origin
S flow
17
Flow within a facility considering the locations
of entrance and exit
At the same location
On adjacent sides
18
Flow within a facility considering the locations of
entrance and exit (cont.)
On the same side but
at opposite ends
On opposite sides
19
Vertical Flow Pattern
Flow between buildings exists
and the connection between
buildings is elevated
Ground level ingress (entry)
and egress (exit) are required
Some bucket and belt
Travel between floors occurs on
the same side of the building conveyors and escalators result
in inclined flow
Ground level ingress (entry)
and egress (exit) occur on the
same side of the building
Backtracking occurs due to the
return to the top floor
20
Flow Planning
•
Planning effective flow involves combining the above patterns with adequate isles to obtain
progressive movements from origin to destination.
•
An effective flow can be achieved by maximizing directed flow paths, reducing flow, and
minimizing the costs of flow.
•
A directed flow path is an uninterrupted flow path progressing directly from origin to
destination: the Figure below illustrates the congestion and undesirable intersections that may
occur when flow paths are interrupted.
Uninterrupted flow paths
Interrupted flow paths
21
Flow Planning (cont.)
• The reduction of flow can be achieved by work simplification including:
1. Eliminating flow by planning for the delivery of materials, information, or people directly to the point of
ultimate use and eliminate intermediate steps.
2. Minimizing multiple flows by planning for the flow between two consecutive points of use to take
place in as few movements as possible.
3. Combining flows and operations whenever possible by planning for the movement of materials,
information, or people to be combined with a processing step.
• Minimizing the cost of flow can be achieved as follows:
1. Reduction of manual handling by minimizing walking, manual travel distances, and motions.
2. Elimination of manual handling by mechanizing or automating flow.
22
Measuring Flow
1.
Flow among departments is one of the most important factors in the arrangement of departments
within a facility.
2.
Flows may be specified in a quantitative manner or a qualitative manner. Quantitative measures may
include pieces per hour, moves per day, pounds per week. Qualitative measures may range from an
absolute necessity that two departments show be close to each other to a preference that two
departments not being close to each other.
3.
In facilities having large volumes of materials, information, a number of people moving between
departments, a quantitative measure of flow will typically be the basis for the arrangement of
departments. On the contrary, in facilities having very little actual movement of materials,
information, and people flowing between departments, but having significant communication and
organizational interrelation, a qualitative measure of flow will typically serve as the basis for the
arrangement of departments.
4.
Most often, a facility will have a need for both quantitative and qualitative measures of flow and both
measures should be used.
5.
Quantitative flow measure: From-to Chart
Qualitative flow measure: Relationship (REL) Chart
23
Quantitative Flow Measurement
•
A From-to Chart is constructed as follows:
1.
List all departments down the row and across the column following the overall flow pattern.
2.
Establish a measure of flow for the facility that accurately indicates equivalent flow volumes. If
the items moved are equivalent with respect to ease of movement, the number of trips may be
recorded in the from-to chart. If the items moved vary in size, weight, value, risk of damage,
shape, and so on, then equivalent items may be established so that the quantities recorded in
the from-to chart represent the proper relationships among the volumes of movement.
3.
Based on the flow paths for the items to be moved and the established measure of flow, record
the flow volumes in the from-to chart.
24
Example 1
Stores
Milling
Turning
Press
Plate
Assembly
Warehouse
Stores
Turning
Milling
Press
Plate
Assembly
Warehouse
From-to Chart
Stores
–
12 6
9
1
4
–
Stores
–
6
12
9
1
4
–
Milling
–
–
–
–
7
2
–
Turning
–
–
3
–
4
–
–
Turning
–
3
–
–
4
–
–
Milling
–
–
–
–
7
2
–
Press
–
–
–
–
3
1
1
Press
–
–
–
–
3
1
1
Plate
–
3
1
–
–
4
3
Plate
–
1
3
–
–
4
3
Assembly
1
–
–
–
–
–
7
Assembly
1
–
–
–
–
–
7
Warehouse
–
–
–
–
–
–
–
Warehouse
–
–
–
–
–
–
–
Original Flow Pattern
Revised Flow Pattern
25
Warehouse
Assembly
Plate
Press
Milling
Turning
Store
Flow Patterns
Press
Stores
Warehouse Assembly
Turning
Press
Milling
Plate
Assembly
Warehouse
S-shaped flow
Milling
Plate
U-shaped flow
Straight-line flow
Stores
Turning
Stores
Turning
Milling
Press
Warehouse
Plate
Assembly
W-shaped flow
26
Warehouse
Assembly
Plate
Press
Milling
Turning
Store
Flow Patterns (cont.)
Press
Stores
Warehouse Assembly
Turning
Press
Milling
Plate
Assembly
Warehouse
S-shaped flow
Milling
Plate
U-shaped flow
Straight-line flow
Stores
Turning
Stores
Turning
Milling
Press
Warehouse
Plate
Assembly
W-shaped flow
27
Types of Layout
Volume
High
Product
Planning
Department
Product
Layout
Medium
Fixed Location
Layout
Fixed Materials
Location
Planning
Department
Product
Family
Planning
Department
Group Technology
Layout
Process
Layout
Process
Planning
Department
Low
Low
Medium
High
Variety
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Fixed Product Layout
Lathe
Press
Grind
W
a
r
e
h
o
u
s
e
S
t
o
r
a
g
e
Weld
Paint
Assembly
29
Fixed Product Layout
30
Fixed Product Layout (cont.)
•
Advantages
1.
Material movement is reduced.
Promotes job enlargement by allowing individuals or teams to perform the
“whole job”.
Continuity of operations and responsibility results from team.
Highly flexible; can accommodate changes in product design, product mix, and
product volume.
Independence of production centers allowing scheduling to achieve minimum
total production time.
2.
3.
4.
5.
•
Limitations
1.
Increased movement of personnel and equipment.
Equipment duplication may occur.
Higher skill requirements for personnel.
General supervision required.
Cumbersome and costly positioning of material and machinery.
Low equipment utilization.
2.
3.
4.
5.
6.
31
Product Layout
Lathe
S
t
o
r
a
g
e
Drill
Press
Bend
Mill
Drill
Lathe
Lathe
Grind
Drill
Drill
A
s
s
e
m
b
l
y
W
a
r
e
h
o
u
s
e
Drill
32
Product Layout
33
Product Layout (cont.)
•
Advantages
1. Since the layout corresponds to the sequence of operations, smooth and logical
flow lines result.
2. Since the work from one process is fed directly into the next, small in-process
inventories result.
3. Total production time per unit is short.
4. Since the machines are located so as to minimize distances between consecutive
operations, material handling is reduced.
5. Little skill is usually required by operators at the production line; hence, training is
simple, short, and inexpensive.
6. Simple production planning control systems are possible.
7. Less space is occupied by work in transit and for temporary storage.
34
Product Layout (cont.)
•
Limitations
1. A breakdown of one machine may lead to a complete stoppage of the line that
follows that machine.
2. Since the layout is determined by the product, a change in product design may
require major alternations in the layout.
3. The “pace” of production is determined by the slowest machine.
4. Supervision is general, rather than specialized.
5. Comparatively high investment is required, as identical machines (a few not fully
utilized) are sometimes distributed along the line.
35
Process Layout
Lathe
S
t
o
r
a
g
e
Lathe
Drill
Weld
Lathe
Lathe
Drill
Paint
Mill
Mill
Grind
Assembly
Mill
Mill
Grind
Assembly
Weld
Paint
W
a
r
e
h
o
u
s
e
36
Process Layout
37
Process Layout (cont.)
•
Advantages
1.
5.
Better utilization of machines can result; consequently, fewer machines are
required.
A high degree of flexibility exists relative to equipment or man power allocation for
specific tasks.
Comparatively low investment in machines is required.
The diversity of tasks offers a more interesting and satisfying occupation for the
operator.
Specialized supervision is possible.
•
Limitations
1.
Since longer flow lines usually exist, material handling is more expensive.
Production planning and control systems are more involved.
Total production time is usually longer.
Comparatively large amounts of in-process inventory result.
Space and capital are tied up by work in process.
Because of the diversity of the jobs in specialized departments, higher grades of
38
skill are required.
2.
3.
4.
2.
3.
4.
5.
6.
Group Layout
Lathe
S
t
o
r
a
g
e
Drill
Grind
Assembly
Mill
Assembly
Weld
Paint
Press
Lathe
Drill
Press
Assembly
Grind
Drill
Assembly
Drill
Grind
W
a
r
e
h
o
u
s
e
39
Group Layout (cont.)
•
Advantages
1.
4.
5.
Increased machine utilization.
Team attitude and job enlargement tend to occur.
Compromise between product layout and process layout, with associated
advantages.
Supports the use of general purpose equipment.
Shorter travel distances and smoother flow lines than for process layout.
•
Limitations
1.
General supervision required.
Higher skill levels required of employees than for product layout.
Compromise between product layout and process layout, with associated
limitations.
Depends on balanced material flow through the cell; otherwise, buffers and workin-process storage are required.
Lower machine utilization than for process layout.
2.
3.
2.
3.
4.
5.
40
Hybrid Layout
•
Combination of the layouts discussed.
•
A sample hybrid layout that has characteristics of group, process and product layout is shown
in the following figure.
•
A combination of group layout in manufacturing cells, product layout in assembly area, and
process layout in the general machining and finishing section is used.
TM
DM
TM
TM
BM
TM
TM
41
Flow Dominance Measure
•
Notations:
M:
number of activities.
Nij:
number of different types of items moved between activities i and j.
fijk:
flow volume between i and j for item k (in moves/time period).
hijk:
equivalence factor for moving item k with respect to other items moved
between i and j (dimensionless).
wij:
equivalent flow volume specified in from-to chart (in moves/time period),
N ij
w ij =  f ijk h ijk .
k 1
42
Flow Dominance Measure (cont.)
•
fU  f '
fU  fL
Flow dominance measure = f =
where
1
2
  2
2 2
w

M
w 
ij
 i  1 j 1


2
M

1




f' 
,
w
M M
1
2
 M  M1 
fU  M 
 ,
2
(M

1)(M

1)


2
M M
  w ij
w=
i  1 j 1
M2
1


fL  M 
2

 (M  1)(M  1) 
1
2
•
f is the coefficient of variation.
•
fL and fU are lower and upper bounds on f, respectively (fL  f  fU).
•
The upper bound fU is only guaranteed to work when each process plan includes all activities. In this case, 0 
f  1.
43
Flow Dominance Measure (cont.)
Three cases :
1. f  0  a few dominant flows exist.  product layout.
 can use operations process chart as starting point for developing layout
and material handling system design.
 quantitative measures principal source of activity relationship.
2. f  1  many nearly equal flows exist.
 any layout equally good with respect to flows .
 qualitative measures principal source of activity relationship.
3. 0 << f << 1  no dominant flows exist.  difficult to develop layout.
 process or product family layout .
 both quantitative and qualitative measures important source of activity
relationship.
44
Example 1
•
Given three machines (activities) labeled 1, 2 & 3,
Product
•
Process Plan
Quantities/Shift
A
1-2-3
10
B
2-1
5
C
3-1-2
15
Assume Product B is twice as “difficult” to move as A or C  hijB = 2 and hijA = hijC = 1
To
1
2
3
0
110
1  15
25
0
From
Equivalent
Flow Volume
From-To Chart
1

2
25
10
0
1  10
10
3
1  15
15
0
0
w12 = 25,
w21 = 10, etc
45
Example 1 (cont.)
M = 3 and
w=
(25  10  10  15)
 6.67
32
 (25  10  10  15 )  (3  6.67

32  1

'
f 
6.67
2
2
2
2
1
2
2
2
)


1
2
= 1.352
1
2
 3  3 1 
1


f U  3
=
1.984
and
f

3
 0.75

2

2

L
 (3  1)(3  1) 
 (3  1)(3  1) 
2
f
1984
.
 1352
.
 0.5122
1984
.
 0.75
 no dominant flows exist
(likely, since 3 different process plans)
46
Qualitative Measures
•
Closeness values (A, E, I, O, U, X) used to indicate physical proximity requirements
between activities.
•
Relationship Chart can only show symmetric relationships, as compared to From-to
Chart (wij  wji possible).
•
Relationship Chart is starting point for developing layout when 0 << f  1.
–
If f  1, then don’t need to consider flow (only qualitative relationship)
–
If f <<1, then one can convert equivalent flow volumes to closeness values so that material
flow relationships can be considered along with qualitative relationship.
–
If f  0, then can still convert to relationship chart if significant qualitative relationship exists,
otherwise, just use operations process chart.
47
Conversion Method
•
To convert equivalent flow volumes to closeness values for the example problem,
use wij + wji to make them symmetric.
•
Conversion relations :
20 < wij + wji
A
w12 + w21 = 25 + 15  A
12 < wij + wji  20
E
w13 + w31 = 0 + 15  E
5 < wij + wji  12
I
w23 + w32 = 10 + 0  I
0 < wij + wji  5
O
wij + wji = 0
U
Machine 1
A
E
Machine 2
I
Machine 3
48