Facility Design – An Introduction

R. Lindeke, Ph. D.

IE 3265

Sp. 2006

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

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

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

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

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

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

Flow Patterns within Process

Departments (Job Shops)

Aisle

Aisle

A. Parallel FlowAisle

B. Perpendicular Flow

Aisle

Aisle

C. Diagonal Flow

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

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

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!

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)

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!

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

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

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

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)

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

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:

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

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

Using Activity Relationship Chart to build

Designs

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

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

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

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

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

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

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

• 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

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

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

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

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

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

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

Layout Total Transport Cost

• Form: M*F*C “cell products”

• Sum each cell of resultant matrix � it is the facility transportation cost (for

comparison)

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

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

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

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

New Transportation Costs:

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!

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

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

Transportation Cost Picture:

A further savings of $1000 – as manager we decide if the new configuration design is worth the savings gained!