facility design – an introduction [compatibility mode]
TRANSCRIPT
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Facility Design – An Introduction
R. Lindeke, Ph. D.
IE 3265
Sp. 2006
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Facility Layouts:
• 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
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Decision Makers:
• What is the desired flexibility and required output?
• What is the forecast product demand and its growth?
• What are the processing requirements?
• Number of operators• 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
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Signs of a Successful Layout
1. Directed Flow Patterns:
1. Straight line or other smooth patterns of movement
2. Backtracking kept to a minimum
2. Predictable Processing Time
3. Little WIP in Facility
4. Open Floors: allow communication and easy tracking of work &
employees
5. Bottleneck operations under control
6. Work Stations close together
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Signs of a Successful Layout, cont:
7. Orderly Handling & Storage of Raw Materials and Finished
products
8. No extra handling or unnecessary handling of materials
9. Can easily adapt to changing conditions
1. Considers demand growth or decline
2. Considers product change over
3. Considers technological change
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Workstation Layouts Within a cell:
IMPROVED LAYOUTS:
Standard Layouts
End to End
Back to Back (poor)
Front to Front
I/O
Circular or U Flow
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Considering Circular or U-Flow:
• Advantages:
• One operator can tend several machines
• Common I/O station simplifies material transfer
to/from cell to the rest of the facilityto/from cell to the rest of the facility
• Automation can be tried for several machines
• Disadvantages:
• Limited Queuing space or WIP storage within cell
• Requires excellent balance and high quality to
keep flow active between workstations in the cell
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Flow Patterns within Process
Departments (Job Shops)
Aisle
Aisle
A. Parallel FlowAisle
B. Perpendicular Flow
Aisle
Aisle
C. Diagonal Flow
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Some Job Shop Ideas:
• Flow is in-out of the department not between machines
• Traffic patterns must support movement from and to
aislesaisles
• Diagonal designs often save floor space in 1 way aisle
shops
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Overall – Flow is a Function of Aisles
• 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 Aisle Set Aside
< 6 ft2 5 -10% of calc. size
6 – 12 ft2 10 - 20% of calc. size
12 – 18 ft2 20 - 30% of calc. size
> 18 ft2 30 - 40% of calc. size
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Aisle width is controlled by the traffic that flows on it
Type of Traffic Min. Aisle WidthLarge Wheeled Indoor/outdoor Tractors 12’*
Aisle Consideration, cont.
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!
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General Aisle Issues:
• Good Aisle Designs …
– Avoid curves/jogs/non 90° 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)
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Facility Designs Seeks:
• To maximize directed (forward) flow
– 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• Distances minimized, too
• Minimize cost of flow – expensive flows should be short while
lighter or less critical flows can be longer
*No Backtracks!
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An Example:
50’
50’25’
A
D
• Flow Straight Thru: A-B-C-D is 250’
• Flow w/Backtracking: A-B-C-A-D is 550’
• Backtracking is an Economic decision!• 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
50’ 75’25’
B C
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The Technical Jobs of Facilities Design:
• Determination of Space requirements:
– Workstation space for:
• Equipment
– Footprint + machine travel + access (load/maintenance) + shop – Footprint + machine travel + access (load/maintenance) + shop
services (air/electrical/water, etc)
• Materials –
– consider unit load size + tooling/scrap etc
• Personnel –
– ingress & egress 30 – 42” for passage between stationary or
operating machines
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The Technical Jobs of Facilities Design:
• Determination of Space requirements (cont.):
– Departmental (Cell) Requirements:
• Σ(WS + G.Service + M.Handling )• Σ(WSreqr + G.Service + M.Handlingreqr)
• G. Service areas
– offices, records, data, inspection/QC, etc.
• Material Handling
– inside traffic set asides to move product, tools, raw materials,
etc
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The Technical Jobs of Facilities Design:
• Determination of Space requirements (cont.):
– Specifics for Work Centers:
• 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)
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The Technical Jobs of Facilities Design:
• 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:
• SLP (systematic layout planning) based on activity relationship charts to • SLP (systematic layout planning) based on activity relationship charts to
suggest appropriate layouts
• Software to optimize the relationships
– Using Quantitative tools:
• Mileage Charts: area to area distance matrices
• From -To Charts: Move/Volume/Cost Matrices
• Appropriate software to compute and optimize the arrangements
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Typical Activity Relationship Chart:
These charts are often These charts are often called an AEIOUX chart – the letters used to explain relationships that are learned during our facility studies:
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Completing the Activities Relationship Chart:
• 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:
• 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
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Using Activity Relationship Chart to build
Designs:
• Using Pure SLP ideas we develop a
“Meatball” diagram and move
departments around to shorten A & E departments around to shorten A & E
lines while increasing length of X
lines
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Using Activity Relationship Chart to build
Designs
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Using Activity Relationship Chart to build
Designs
• 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
Milling: A -; X-; E-A,D; I-E,F; O-;
U- C,G
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
Plating: A -E; X-; E-G; I-B; O-C;
U- A,D
Shipping: A -; X-; E-F; I-E; O-; U- A, B, C,D
Assembly: A -F; X-; E-; I-B,D,G; O-A;
U- C
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Using Activity Relationship Chart to build
Designs
• Select template with highest number of A relationships; tied templates
selected subject to hierarchy: most E’s, Most I’s, fewest X’s
• Here select Plating department (F)
• Next template chosen should have A relationship w/ 1st chosen – any
ties broken as above
• Here Assembly, department E
• Next template chosen should have the highest joint relationship with
first two chosen
• Here is Shipping – G
• This continues until all departments are chosen
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In doing the Design:
F
EBy This
Place F in Center. Then follow in order keeping Ideas (AEIOUX) of
E
G
B
D
A
C
By This Order:
(AEIOUX) of arrangements:
FE
G
BD
AC
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A Final Step: now we consider actual
departmental areas:
Code Function Area Ft2# Units (2000
per)
A Receiving 12,000 6
B Milling 8,000 4B Milling 8,000 4
C Press 6,000 3
D Sc. Machines 12,000 6
E Assembly 8,000 4
F Plating 12,000 6
G Shipping 12,000 6
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Leads to the following Proposed Layout:
• 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
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Addressing the Quantitative Approaches:
• Mileage Charts: showing Distances between
Departments
– Distances measures “Euclidian-wise” using computed – 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
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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:
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From-To Charts
• 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 populatedfully populated
• More expensive travel can be handled with increased Volumes or
have other special handling costs attached
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Examining Quantitative Design
• We begin with a Qualitatively designed facility (one that
meets perceived activity relationships)
• To keep it simple, lets look at a Flow–thru facility: • To keep it simple, lets look at a Flow–thru facility:
A B C D E
General Flow Direction
Consider that each of
the departments (A to
E) are 100 units
square
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Representative Products are selected
for study:
• 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 Prod. Quantity Routing
Pr1 30 A-C-B-D-E
Pr2 12 A-B-D-E
Pr3 7 A-C-D-B-E
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Mileage Chart:
A B C D E
A XXX 100 200 300 400A 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
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From To Chart (based on Routing)
A B C D E
A XXX Pr2 12
Pr 1 30 +
Pr 3 2*7 =
30 +14 = 44
0 0
B 0 XXX 0Pr 1 30 + Pr 3 2*7 =
B 0 XXX 0Pr2 12 = 42 14
C 0 Pr 1 30 XXXPr 3 2*7 =
140
D 0Pr 3 2*7 =
140 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
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From To Issues
• 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)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
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Costing Transport in the Layout:
• For comparison:
• all forward moves cost $1/unit vol/unit distance
• All Backtrack move cost $1.25/unit vol/unit distance
Costs A B C D E
A xxx 1 1 1 1
B 1.25 xxx 1 1 1
C 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
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Layout Total Transport Cost
• Form: M*F*C “cell products”
• Sum each cell of resultant matrix � it is the facility transportation cost (for
comparison)
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Can we do Better?
• Lets Swap Departments B & C
A C B D E
• This will change our Mileage and Cost Matrices as well as
arrangements in From/To Matrix
A C B D E
General Flow Direction
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New Mileage Chart:
A C B D E
A XXX 100 200 300 400A 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
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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
30 +14 = 44
C 0 XXX Pr 1 30Pr 3 2*7 =
140
B 0 0 XXXPr 1 30 +
Pr2 12 = 42
Pr 3 2*7 =
14
D 0 0Pr 3 2*7 =
14XXX
Pr 1 30 +
Pr2 12 = 42
E 0 0 0 0 XXX
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New Cost Matrix:
Costs A C B D E
A xxx 1 1 1 1A 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
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New Transportation Costs:
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Examining these results:
• Swapping 2 departments lead to a reduction in cost
of:
– $9900 or about 28% of the original cost
• Can we improve further?
– Not with this fundamental design
– Can we redesign the general footprint?
– Then we can keep looking!
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New Fundamental Design:
• And applying a Euclidean Concept of distances!
A C D
• 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!
A
B
C D
E
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Mileage Chart (now)
A C B D E
A XXX 100 142 200 224A 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
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Transportation Cost Picture:
A further savings of $1000 – as manager we decide if the new configuration design is worth the savings gained!