Facility Design-Week 4 Material Flow Analysis By Anastasia L. Maukar.
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Transcript of Facility Design-Week 4 Material Flow Analysis By Anastasia L. Maukar.
Facility Design-Week 4Material Flow Analysis
By Anastasia L. Maukar
2
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 b. Product
c. Group Technology d. Process
e. Hybrid
• Flow Dominance Measure
3
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• . . . .
4
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
5
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.
6
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.
9
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.
11
Flow Diagram
It depicts the probable movement of
materials in the floor plant. The
movement is represented by a line in
the plant drawing.
12
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.
14
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.
15
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/operator1 machine/operator 2 machines/operator
1 machine/operator
More than 2 machines /operator
16
Flow Pat.: Flow within Departments (cont.)
• In a process department, little flow should occur between workstations within departments. Flow occurs between workstations and aisles.
Aisle
Aisle
Aisle
Aisle
Aisle
Dependent on interactions among workstations
available space
size of materials
Uncommon
One way
One way
17
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
U flow
Serpentine
L flow
S flow
Circularflow
Simplest. Separate receiving/shipping crews
Very popular. Combine receiving /shipping. Simple to administer
When line is too long
Similar to straight. It is not as long.
Terminate flow. Near point of origin
18
Flow within a facility considering the locations of entrance and exit
At the same location
On adjacent sides
19
Flow within a facility considering the locations of entrance and exit (cont.)
On the same side but at opposite ends
On opposite sides
20
Vertical Flow Pattern
Flow between buildings exists and the connection between
buildings is elevated
Ground level ingress (entry) and egress (exit) are required
Ground level ingress (entry) and egress (exit) occur on the
same side of the building
Travel between floors occurs on the same side of the building
Some bucket and belt conveyors and escalators result
in inclined flow
Backtracking occurs due to the return to the top floor
21
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
22
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.
23
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
24
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.
25
Example 1
Stores
Turning
Milling
Press
Plate
Assembly
Warehouse
– 6 12 9 1 4 –
– – 3 – 4 – –
– – – – 7 2 –
– – – – 3 1 1
– 1 3 – – 4 3
1 – – – – – 7
– – – – – – –
Sto
res
T
urni
ng
Mil
ling
Pre
ss
Pla
te
Ass
embl
y
War
ehou
se
Stores
Milling
Turning
Press
Plate
Assembly
Warehouse
– 12 6 9 1 4 –
– – – – 7 2 –
– 3 – – 4 – –
– – – – 3 1 1
– 3 1 – – 4 3
1 – – – – – 7
– – – – – – –
Sto
res
Mil
ling
Tur
ning
Pre
ss
Pla
te
Ass
embl
y
War
ehou
se
From-to Chart
Original Flow Pattern Revised Flow Pattern
26
Flow PatternsS
tore
Tur
ning
Mil
ling
Pre
ss
Pla
te
Ass
embl
y
War
ehou
se
Stores Turning Milling
Warehouse Assembly Plate
Press
Stores Press Plate Assembly
Turning Milling Warehouse
Stores Milling Warehouse
Turning Press Plate Assembly
Straight-line flow U-shaped flow
W-shaped flowS-shaped flow
27
Flow Patterns (cont.)S
tore
Tur
ning
Mil
ling
Pre
ss
Pla
te
Ass
embl
y
War
ehou
se
Stores Turning Milling
Warehouse Assembly Plate
Press
Stores Press Plate Assembly
Turning Milling Warehouse
Stores Milling Warehouse
Turning Press Plate Assembly
Straight-line flow U-shaped flow
W-shaped flowS-shaped flow
28
Types of Layout
Volume
High
Medium
Low
Low Medium HighVariety
Product Planning Department
Fixed Materials Location Planning Department
Process Planning Department
Product Family Planning Department
Product Layout
Fixed Location Layout
Group Technology Layout
Process Layout
31
Fixed Product Layout (cont.)
• Advantages 1. Material movement is reduced.2. Promotes job enlargement by allowing individuals or teams to perform the
“whole job”.3. Continuity of operations and responsibility results from team.4. Highly flexible; can accommodate changes in product design, product mix, and
product volume.5. Independence of production centers allowing scheduling to achieve minimum
total production time.
• Limitations1. Increased movement of personnel and equipment.2. Equipment duplication may occur.3. Higher skill requirements for personnel.4. General supervision required.5. Cumbersome and costly positioning of material and machinery.6. Low equipment utilization.
32
Product Layout
Drill Grind Drill
Lathe
Drill
Drill
Storage
Warehouse
Assembly
Lathe
Bend
Lathe
Mill
Press
Drill
34
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.
35
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.
36
Process Layout
Lathe Drill Weld
Mill
Drill
Grind
Storage
Warehouse
Lathe
Lathe
Mill
Mill
Lathe
Mill
Paint
Grind
Assembly
Assembly
Paint
Weld
38
Process Layout (cont.)
• Advantages 1. Better utilization of machines can result; consequently, fewer machines are
required.2. A high degree of flexibility exists relative to equipment or man power allocation for
specific tasks.3. Comparatively low investment in machines is required.4. The diversity of tasks offers a more interesting and satisfying occupation for the
operator.5. Specialized supervision is possible.
• Limitations1. Since longer flow lines usually exist, material handling is more expensive.2. Production planning and control systems are more involved.3. Total production time is usually longer.4. Comparatively large amounts of in-process inventory result.5. Space and capital are tied up by work in process.6. Because of the diversity of the jobs in specialized departments, higher grades of
skill are required.
39
Group Layout
Drill Grind Assembly
Drill
Weld
Assembly
Storage
Warehouse
Lathe
Assembly
Grind
Press
Mill
Lathe
Paint
Drill
Drill
Press
Grind
Assembly
40
Group Layout (cont.)
• Advantages 1. Increased machine utilization.2. Team attitude and job enlargement tend to occur.3. Compromise between product layout and process layout, with associated
advantages.4. Supports the use of general purpose equipment.5. Shorter travel distances and smoother flow lines than for process layout.
• Limitations1. General supervision required.2. Higher skill levels required of employees than for product layout.3. Compromise between product layout and process layout, with associated
limitations.4. Depends on balanced material flow through the cell; otherwise, buffers and work-
in-process storage are required.5. Lower machine utilization than for process layout.
41
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
TM TM
TM TMDM
BM
42
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),
w = f h .ij ijk ijkk
N ij
1
43
Flow Dominance Measure (cont.)
• Flow dominance measure = f =
where
f f
f fU
'
U L
f
w M w
M 1
w, w =
w
M
f MM M 1
(M 1 )(M 1 ), f M
1
(M 1 )(M 1 )
'
ij2 2 2
j 1
M
i 1
M
2
1
2
ijj 1
M
i 1
M
2
U
2
2 L 2
1
21
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.
44
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.
45
Example 1
• Given three machines (activities) labeled 1, 2 & 3,
Product
A
B
C
Process Plan
1 - 2 - 3
2 - 1
3 - 1 - 2
Quantities/Shift
10
5
15
• Assume Product B is twice as “difficult” to move as A or C hijB = 2 and hijA = hijC = 1
To
From
1
2
3
1
0
2 510
1 1515
2
1101 15
25
0
0
3
0
1 1010
0
Equivalent Flow Volume
From-To Chart
w12 = 25,
w21 = 10, etc
46
Example 1 (cont.)
M = 3 and
f3 1
6 .6 7= .3 5 2
f 33 3 1
(3 1 )(3 1 )= 1 .9 8 4 an d f 3
1
(3 1 )(3 1 )
f
'2
U
2
2 L 2
( ) ( . )
.
. .
. ..
2 5 1 0 1 0 1 5 3 6 6 7
1
0 7 5
1 9 8 4 1 3 5 2
1 9 8 4 0 7 50 5 1 2 2
2 2 2 2 2 212
1
21
2
w =(2 5 1 0 1 0 1 5 )
36 .6 72
no dominant flows exist (likely, since 3 different process plans)
47
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.
48
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
A
IE
Machine 1
Machine 2
Machine 3