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Facility Design – An Introduction

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Facility Design – An Introduction
R. Lindeke, Ph. D.
IE 3265
Sp. 2006
Facility Layouts:
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A Decision that Encompasses:
–
–
–
–
Placement of �Departments’
Placement of Workstations/Machines
Placement of Stockholding points within Factory
or Warehouse
Development of Controlled Traffic Patterns to
generate smooth workflow throughout
Decision Makers:
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What is the desired flexibility and
required output?
What is the forecast product demand
and its growth?
What are the processing requirements?
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Number of operators
Level of flow between work stations and
between work areas
How can the design balance
requirements on Workstation loading
Facility Space Available
Signs of a Successful Layout
1.
Directed Flow Patterns:
1.
2.
2.
3.
4.
5.
6.
Straight line or other smooth patterns of
movement
Backtracking kept to a minimum
Predictable Processing Time
Little WIP in Facility
Open Floors: allow communication and
easy tracking of work & employees
Bottleneck operations under control
Work Stations close together
Signs of a Successful Layout, cont:
7.
8.
9.
Orderly Handling & Storage of Raw
Materials and Finished products
No extra handling or unnecessary handling
of materials
Can easily adapt to changing conditions
1.
2.
3.
Considers demand growth or decline
Considers product change over
Considers technological change
Workstation Layouts Within a cell:
Standard Layouts
IMPROVED
LAYOUTS:
End to End
Front to Front
I/O
Back to Back
(poor)
Circular or U Flow
Considering Circular or U-Flow:
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Advantages:
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One operator can tend several machines
Common I/O station simplifies material
transfer to/from cell to the rest of the
facility
Automation can be tried for several
machines
Disadvantages:
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Limited Queuing space or WIP storage
within cell
Requires excellent balance and high
quality to keep flow active between
workstations in the cell
Flow Patterns within Process
Departments (Job Shops)
Aisle
Aisle
Aisle
A. Parallel Flow
B. Perpendicular Flow
Aisle
C. Diagonal Flow
Aisle
Some Job Shop Ideas:
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Flow is in-out of the department not between
machines
Traffic patterns must support movement from
and to aisles
Diagonal designs often save floor space in 1
way aisle shops
Overall – Flow is a Function of Aisles
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As a designer, aisle placement is of primary interest
and often marks successful or failed designs!
Aisle Size is a function of Load Size!
Set Aside is controlled by Largest Load Area (Rules of Thumb)
Load Area
< 6 ft2
6 – 12 ft2
12 – 18 ft2
> 18 ft2
Aisle Set Aside
5 -10% of calc. size
10 - 20% of calc. size
20 - 30% of calc. size
30 - 40% of calc. size
Aisle Consideration, cont.
Aisle width is controlled by the traffic that flows on it
Type of Traffic
Min. Aisle Width
Large Wheeled Indoor/outdoor Tractors
12’*
Large Forktrucks
11’
Small Forktrucks
9’
Narrow Aisle trucks/AGV’s
6’
Manual Platform Trucks
5’
Personnel
3’
Personnel w/doors 1 side
6’
Personnel w/doors both sides
8’
NOTE: Consider turning radiuses at intersections!
General Aisle Issues:
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Good Aisle Designs …
–
–
–
–
Avoid curves/jogs/non 90п‚°
intersections
Avoid outside wall paths (these
are used for utilities so
machine/workstations should
back to walls if possible
Are straight and lead to door
ways
Allow Flow to be controlled by
entrances and exits (as it should)
Facility Designs Seeks:
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To maximize directed (forward)
flow
–
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Materials move directly from
sources to destination without
jogging around and by paths that
don’t intersect other flows*
Minimize total flow (volume) of all
products
Distances minimized, too
Minimize cost of flow – expensive
flows should be short while lighter
or less critical flows can be longer
*No Backtracks!
An Example:
A
50’
D
50’
B
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50’
C
75’
25’
Flow Straight Thru: A-B-C-D is 250’
Flow w/Backtracking: A-B-C-A-D is 550’
Backtracking is an Economic decision!
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Cost of Added Equipment (replication of A) VS.
Cost of added flow movement and traffic patterns (aisle set
aside) for each product that flows along backtrack
The Technical Jobs of Facilities Design:
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Determination of Space requirements:
–
Workstation space for:
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Equipment
–
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Materials –
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Footprint + machine travel + access (load/maintenance) +
shop services (air/electrical/water, etc)
consider unit load size + tooling/scrap etc
Personnel –
–
ingress & egress 30 – 42” for passage between stationary
or operating machines
The Technical Jobs of Facilities Design:
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Determination of Space requirements (cont.):
–
Departmental (Cell) Requirements:
пЃ¬ пЃ“(WSreqr + G.Service + M.Handlingreqr)
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G. Service areas
–
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offices, records, data, inspection/QC, etc.
Material Handling
–
inside traffic set asides to move product, tools, raw
materials, etc
The Technical Jobs of Facilities Design:
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Determination of Space requirements (cont.):
–
Specifics for Work Centers:
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Use a Worksheet (see handout)
Lists various resources and their requirements
considering services, physical loading (special needs?)
List and sum all areas required
Add in Aisle Allowance
See handout (one for each work center or
assembly line)
The Technical Jobs of Facilities Design:
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The second job is to effectively provide for minimum
flow and cost of flow
Here the designer performs studies of the space
requirements and desired travel patterns
–
Using Qualitative Tools:
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SLP (systematic layout planning) based on activity relationship
charts to suggest appropriate layouts
Software to optimize the relationships
Using Quantitative tools:
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Mileage Charts: area to area distance matrices
From -To Charts: Move/Volume/Cost Matrices
Appropriate software to compute and optimize the
arrangements
Typical Activity Relationship Chart:
These charts are often
called an AEIOUX
chart – the letters
used to explain
relationships that are
learned during our
facility studies:
Completing the Activities Relationship
Chart:
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After listing all departments on chart, Conduct Surveys to assess
relationships with each department’s staff
Interpret results of surveys as closeness needs – itemize and
record closeness requirements to support assessed relationship
Establish the relationships:
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A – absolutely necessary
E – Especially Important
I – Important
O – “ordinary” closeness okay
U – Unimportant
X – Undesirable
Allow all concerned parties to review proposed chart for accuracy
of closeness settings
Using Activity Relationship Chart to
build Designs:
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Using Pure SLP ideas
we develop a “Meatball”
diagram and move
departments around to
shorten A & E lines
while increasing length
of X lines
Using Activity Relationship Chart to
build Designs
Using Activity Relationship Chart to
build Designs
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An alternative approach begins with looking
at each department as equal sized
rectangles listing letter relationship with all
departments in the Facility
Receiving: A -; X-;
E-B; I-D; O-C,E;
U- F,G
Plating: A -E; X-;
E-G; I-B; O-C;
U- A,D
Milling: A -; X-;
E-A,D; I-E,F; O-;
U- C,G
Shipping: A -; X-;
E-F; I-E; O-;
U- A, B, C,D
Press: A -; X-;
E-; I-; O-A,F;
U- B,D,E,G
Sc. Machine: A -;
X-; E-B; I-A,E;
O-; U-C,F,G
Assembly: A -F; X-;
E-; I-B,D,G; O-A;
U- C
Using Activity Relationship Chart to
build Designs
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Select template with highest number of A
relationships; tied templates selected subject to
hierarchy: most E’s, Most I’s, fewest X’s
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Next template chosen should have A relationship w/
1st chosen – any ties broken as above
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Here Assembly, department E
Next template chosen should have the highest joint
relationship with first two chosen
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Here select Plating department (F)
Here is Shipping – G
This continues until all departments are chosen
In doing the Design:
F
By This
Order:
E
G
Place F in Center.
Then follow in order
keeping Ideas
(AEIOUX) of
arrangements:
A
B
C
D B
D
A
C
E
F
G
A Final Step: now we consider actual
departmental areas:
Code
Function
Area Ft2
# Units
(2000 per)
A
B
C
Receiving
Milling
Press
12,000
8,000
6,000
6
4
3
12,000
6
8,000
4
12,000
12,000
6
6
E
Sc.
Machines
Assembly
F
G
Plating
Shipping
D
Leads to the following Proposed
Layout:
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When equal sizes are replaced
with scaled sizes we develop
these layouts:
Obviously, many variants
would be possible (no X’s and
few A and E’s)
We determine appropriate
layout only after quantitative
analysis is applied to the
proposed arrangements
Addressing the Quantitative
Approaches:
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Mileage Charts: showing Distances between
Departments
–
–
Distances measures “Euclidian-wise” using
computed straight lines between department
centroids
Distances measure “Recti-linear” were
department to department distances are
computed by moving horizontally and vertically
along expected aisle routes
Mileage Chart Format
A
B
C
D
E
A
XXX
100
200
300
400
B
100(?)
XXX
100
200
300
C
200
100
XXX
100
200
D
300
200
100
XXX
100
E
400
300
200
100
XXX
BackTracks:
From-To Charts
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Charts, based on Routings, that show
each relevant part’s movement
through the proposed facility
Format is similar to Mileage chart but
are rarely symmetrical or fully
populated
More expensive travel can be
handled with increased Volumes or
have other special handling costs
attached
Examining Quantitative Design
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We begin with a Qualitatively designed
facility (one that meets perceived activity
relationships)
To keep it simple, lets look at a Flow–thru
facility:
A
B
C
D
General Flow Direction
E
Consider that each
of the departments
(A to E) are 100
units square
Representative Products are selected
for study:
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These might be “group seeds” or “large volume”
products or in other ways represent how the product
will move thru the facility
Lets explore 3: (Pr 1, Pr 2 and Pr 3)
Product
Pr1
Prod. Quantity
30
Routing
A-C-B-D-E
Pr2
Pr3
12
7
A-B-D-E
A-C-D-B-E
Mileage Chart:
A
B
C
D
E
A
XXX
100
200
300
400
B
100
XXX
100
200
300
C
200
100
XXX
100
200
D
300
200
100
XXX
100
E
400
300
200
100
XXX
From To Chart (based on Routing)
A
B
C
D
E
0
0
A
XXX
Pr2 12
Pr 1 30 +
Pr 3 2*7 =
30 +14 = 44
B
0
XXX
0
Pr 1 30 +
Pr2 12 = 42
Pr 3 2*7 =
14
C
0
Pr 1 30
XXX
Pr 3 2*7 =
14
0
D
0
Pr 3 2*7 =
14
0
XXX
Pr 1 30 +
Pr2 12 = 42
E
0
0
0
0
XXX
Pr 3 is heavier and costlier to move – we double
volume to make it equivalent to Pr 1 & Pr 2
From To Issues
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The filled cells below the diagonal represent moves
against the general directed flow of the original
facility design ( they – may (should) – cost more
than moves above the line for the same distances)
Cells Close to the diagonal are short distance moves
while cells remote from the diagonal are long
distance moves
The number of moves (not filled cells!) must equal
the total of each move in the routing sheets for the
products
Costing Transport in the Layout:
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For comparison:
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all forward moves cost $1/unit vol/unit distance
All Backtrack move cost $1.25/unit vol/unit distance
Costs
A
A
xxx
B
1
C
1
D
1
E
1
B
C
D
1.25
1.25
1.25
xxx
1.25
1.25
1
xxx
1.25
1
1
xxx
1
1
1
E
1.25
1.25
1.25
1.25
xxx
Layout Total Transport Cost
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Form: M*F*C “cell products”
Sum each cell of resultant matrix пѓ it is the facility
transportation cost (for comparison)
Can we do Better?
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Lets Swap Departments B & C
A
C
B
D
E
General Flow Direction
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This will change our Mileage and Cost
Matrices as well as arrangements in From/To
Matrix
New Mileage Chart:
A
C
B
D
E
A
XXX
100
200
300
400
C
100
XXX
100
200
300
B
200
100
XXX
100
200
D
300
200
100
XXX
100
E
400
300
200
100
XXX
New From-To Chart
A
C
B
D
E
A
XXX
Pr 1 30 +
Pr 3 2*7 =
30 +14 = 44
Pr2 12
0
0
C
0
XXX
Pr 1 30
Pr 3 2*7 =
14
0
B
0
0
XXX
Pr 1 30 +
Pr2 12 = 42
Pr 3 2*7 =
14
D
0
0
Pr 3 2*7 =
14
XXX
Pr 1 30 +
Pr2 12 = 42
E
0
0
0
0
XXX
New Cost Matrix:
Costs
A
C
B
D
E
A
xxx
1
1
1
1
C
1.25
xxx
1
1
1
B
1.25
1.25
xxx
1
1
D
1.25
1.25
1.25
xxx
1
E
1.25
1.25
1.25
1.25
xxx
New Transportation Costs:
Examining these results:
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Swapping 2 departments lead to a reduction
in cost of:
–
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$9900 or about 28% of the original cost
Can we improve further?
–
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Not with this fundamental design
Can we redesign the general footprint?
Then we can keep looking!
New Fundamental Design:
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And applying a Euclidean Concept of distances!
A
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C
D
B
E
Distance from A to B is: (1002+1002).5 = 142 units
Distance A to E is: (2002+1002).5 = 224 units
Typically, with Euclidean distances, were would not consider
transport cost differences in either direction – this facility shape
doesn’t favor general directions of flow!
Mileage Chart (now)
A
C
B
D
E
A
XXX
100
142
200
224
C
100
XXX
100
100
142
B
142
100
XXX
142
100
D
200
100
142
XXX
100
E
224
142
100
100
XXX
Transportation Cost Picture:
A further savings of $1000 – as manager we decide if the
new configuration design is worth the savings gained!
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