© 2014 Lew Hofmann

>>>PROCESS LAYOUT<<<

Drilling

D D

D D

Grinding

G G

G G

G G

Milling

M M

M M

M M

Assembly

A A

A A

Lathing

Receiving and shipping

L

L L

L L

L L

L

© 2014 Lew Hofmann

Ford Production Plant LayoutFord-Brazil

© 2014 Lew Hofmann

What is a “Layout?”

Layout refers to the physical arrangement of economic activity centers for processes within a facility.

A “center” can be anything that consumes space.

The Layout decisions are:What centers are needed?How much space and capacity are needed?Layout Configuration?Where to locate them?

© 2014 Lew Hofmann

Strategic IssuesGood layouts improve productivity and efficiency.

Altering a layout can affect an organization and how well it meets its competitive priorities in the following ways:

1. Increasing customer satisfaction and sales at a retail store.

2. Facilitating the flow of materials and information

3. Increasing the efficient utilization of labor and equipment.

4. Reducing hazards to workers

5. Improving employee working conditions and morale

6. Improving communication and interactions

© 2014 Lew Hofmann

Basic Layouts

Fixed Position

Line-Flow (Product)

Flexible-Flow (Process)

Hybrid

Retail

Warehouse

Office

Directly concerned with layout of the transformation process.

Not directly concerned with the transformation process.

© 2014 Lew Hofmann

Qualities of a good layout

Effective & efficient use of space

Facilitates good communication

Minimizes costs

Meets quality of work life needsnoisesafetylightingtemperaturesocialaesthetics

We are going arrange activity centers to optimize workflow and time utilization, but this list of intangible factors is also very important and very much affected by the layout.

© 2014 Lew Hofmann

Flexible Flow Layout

FoundryMilling

machines

LathesGrinding

Painting Drills

Office

Welding

Forging

A job shop has a process-focused (flexible-flow) layout.

Different jobs have different process requirements and different flow patterns.

© 2014 Lew Hofmann

Line-Flow Layout

Station 1 Station 2 Station 3 Station 4

A production line has a line-flow layout.

Also known as a ‘product-focused’ layout because work (people, workstations, machines) are focused on the product as it moves down the line.

© 2014 Lew Hofmann

Warehouse/Storage Layouts

Objectives:1. Optimal utilization of storage space at

minimum cost2. Minimizing the cost of handling and

moving materials and the cost of storing them.

Flows are to and from (in and out) of the warehouse rather than in between internal areas.

• We try to minimize the # of trips & distances.

© 2014 Lew Hofmann

Sample Warehouse Problem

Dept. Trips AreasA 330 3B 240 1C 180 2D 460 4E 300 1F 60 1G 280 2

Trips are monthly round trips to and from the warehouse. (What goes in the warehouse must eventually come out.)

There are no one-way trips.

Areas are the number of areas assigned to each department.

© 2014 Lew Hofmann

E G D D A A C

B G D D A C F

Sample Warehouse Problem

Dept. Trips Areas Trips PriorityA 330 3 110 5B 240 1 240 2C 180 2 90 6D 460 4 115 4E 300 1 300 1F 60 1 60 7G 280 2 140 3

To solve the layout, divide the # of trips each department makes by their number of areas to get trips-per-area.

Then prioritize the departments by the # of trips per area. The department with the most number of trips per area gets the closest areas.

Spaces are assigned closest to the entrance based on priority.

Dock

© 2014 Lew Hofmann

Retail Layout

Objectives:1. Expose customers to as

many products as possible.

2. Maximize the net profit per square foot of display space.

© 2014 Lew Hofmann

Fixed Position Layout

Used where the product remains in a fixed position.

(Usually large construction such as building a bridge)

Workers & equipment move to and from the product.Poorest space utilizationMost difficult type of layout to make efficient.Process is the extreme in Low-volume, High variety.To make it more efficient, it is usually combined with one or more other types of layouts. (A Hybrid Layout)

© 2014 Lew Hofmann

Hybrid Layouts to improve Fixed Position

If possible, a line-flow and/or a flexible-flow layout is used along with a fixed-position layout in order to improve efficiency.

Fixed + Line-Flow (Product)

EG: Aircraft parts are made in a line-flow and then delivered to a Fixed-Position location for assembly.

Fixed + Flexible Flow (Process) Layouts

Prefab. Homes are made in a flexible flow layout and then assembled at a Fixed Position Layout.

© 2014 Lew Hofmann

Flexible-Flow (Process) Layout

Objective: To minimize movement of people, parts, and materials.

Flexible flow is common for low-volume, high-variety processes.

Resources are grouped by function or process.

Typically a variety of products (or customers) move from one area to another depending on what activity is required. (Eg: Students at TCNJ)

© 2014 Lew Hofmann

Flexible-Flow (process) Layout

AdvantagesPeople & machines can be moved around and used in a variety of ways. (flexible)Uses general purpose equipment so it is a less capital-intensive process.

DisadvantagesHigher labor skills are neededHigher inventory levels and inventory-related costsHigher costs of moving materials since more movement is required to go from process to process.Longer production (processing) time from start to endLow utilization of equipment.

© 2014 Lew Hofmann

Designing Flexible-Flow Layouts

Step 1: Gather informationWhat are the activity centers (process centers)?How much space does each activity center need?Closeness factors: Which centers need to be located close to one another due to frequent interaction.

Closeness matrix (Two-From matrix): A table that shows the degree of interaction between each pair of activity centers or departments.

Step 2: Develop a Block plan: A plan that indicates the placement of each activity center or department.

© 2014 Lew Hofmann

The Classic To-From Matrix

• Used on maps for the last 100 years

© 2014 Lew Hofmann

A B C D E FA 20 20 80B 10 75C 15 90D 70EF

A,B 20A,D 20A,F 80B,C 10B,E 75C,D 15C,F 90D,E 70

Values are usually distances between two areas, but could be some other relative measure of closeness such as travel time, steps needed, trips per period of time, etc.

Two types of CLOSENESS (To-From) MATRICIES

© 2014 Lew Hofmann

Develop a Block plan A plan that indicates the placement of each department.

A B C D E FA 20 20 80B 10 75C 15 90D 70EF

Block Plan of Existing Layout

B D CF E A

To-From Matrices of Department InteractionsA,B 20A,D 20A,F 80B,C 10B,E 75C,D 15C,F 90D,E 70

Department interactions

(Trips per day)

© 2014 Lew Hofmann

Dept. Trips Current Total PPair Per-Day Distance DistanceA,B 20 3 60 5A,D 20 2 40 6A,F 80 2 160 2B,C 10 2 20 7B,E 75 2 150 3C,D 15 1 15 8C,F 90 3 270 1D,E 70 1 70 4

785

Block Plan of Existing Layout

B D CF E A

Rectilinear

EuclideanA

B

Multiply trips-per-day times the distance between areas to get total distance traveled.

Determine the distance between each “interacting” department using rectilinear distance.

Total distance is used to compare plans.

Prioritize the department pairs based on total distance traveled.

© 2014 Lew Hofmann

Dept. Trips Current Total P New TotalPair Per Day Distance Distance Distance DistanceA,B 20 3 60 5A,D 20 2 40 6A,F 80 2 160 2B,C 10 2 20 7B,E 75 2 150 3C,D 15 1 15 8C,F 90 3 270 1D,E 70 1 70 4

785Existing Layout

B D CF E A

New Layout

FC D

AEB

3

1

1

1

1112

Use a trial-and-error method of selecting a new layout based on the priorities.

© 2014 Lew Hofmann

Dept. Trips Current Total P New TotalPair Per Day Distance Distance Distance DistanceA,B 20 3 60 5 1 20A,D 20 2 40 6 1 20A,F 80 2 160 2 1 80B,C 10 2 20 7 3 30B,E 75 2 150 3 1 75C,D 15 1 15 8 1 15C,F 90 3 270 1 1 90D,E 70 1 70 4 1 70

785 400Existing Layout

B D CF E A

New LayoutC D EF A B

A 47.7% improvement

© 2014 Lew Hofmann

Available Decision-Support Tools

Automated layout design program (ALDEP) A computer software package that constructs a good layout from scratch, adding one department at a time.

Computerized Relative Allocation of Facilities Technique (CRAFT)

A trial-and-error (heuristic) method that begins with the closeness matrix and an initial block layout, and makes a series of paired exchanges of departments to find a better block plan.

(No need to memorize these tools for the exam. Just be aware that software exists for solving these types of layout problems.)

© 2014 Lew Hofmann

More HybridsIn addition to the common fixed-position hybrids that combine flexible flow and/or line flow with a fixed position situation, there are other hybrids that have characteristics of both a flexible-flow and a line-flow.

One-Worker, Multiple-Machines (OWMM) cell is a one-person cell in which a worker operates several different machines simultaneously to achieve a line flow at that particular workstation.

© 2014 Lew Hofmann

Machine 1

Machine 2

Machine 3

Machine 4Machine 5

Materials in

Finished goods out

One Worker, Multiple Machines

© 2014 Lew Hofmann

Group TechnologyA Hybrid Layout technique used to make flexible flows more like line flows.

A low-volume, flexible-flow process that contains multiple line-flows. (One-Worker, Many Machines is a mini line flow)

Parts/products that have similar processing requirements are grouped into line flows.

Material Inventory is reduced

Work-in-process Inventory is reduced

Work flow is simplified

Floor space is optimized

© 2014 Lew Hofmann

Before Group Technology

Drilling

D D

D D

Grinding

G G

G G

G G

Milling

M M

M M

M M

Assembly

A A

A A

Lathing

Receiving and shipping

L

L L

L L

L L

L

Jumbled flows in a job shop without using Group Technology cells.

© 2014 Lew Hofmann

After applying Group Technology

Line flows in a job shop with three GT cells.Each of three types of jobs go through their required functional processes in a linear flow.

Cell 3

L M G G

Cell 1 Cell 2

Assembly area

A A

L M DL

L MShipping

D

Receiving

G

© 2014 Lew Hofmann

Office LayoutsPeople problems dominate office layouts.Most procedures for designing office layouts try to group workers whose jobs require frequent interaction.Privacy is another key factor in office design.Three basic types of office layouts:1. Traditional (Private offices such as for faculty in

the School of Business and for attorneys in a law firm)

2. Office Landscaping (cubicles)

3. Activity Settings (Gym, Library) Where workers move from area to area depending on the type of work they need to do.

© 2014 Lew Hofmann

Line-Flow (Product) Layouts

Objective: To have a work-balanced line!Minimize the number of workers/work stations on a production line, and give them equal (balanced) work loads

Two types of line flows that can be balanced…Type Nature Flow Balancing

Fabrication Lines

Makes Parts

Machine Paced

Mechanical & Engineering

changes

Assembly Lines

Assembles Parts

Worker Paced

Task Changes

Note: Waiting lines cannot be balanced because there is no work being done in the line.

Cutting, milling, machining, drilling, etc.

Assembling parts and components

© 2014 Lew Hofmann

Line Balancing

The work that one person or one machine does should be balanced (in terms of time) with the work that another person or machine does on that line.

Imbalanced lines are inefficient.

Some people or machines are idle while others are working.

Idleness is wasteful

Unions and workers don’t tolerate unequal work loads.

Station 1 Station 2 Station 3 Station 4

© 2014 Lew Hofmann

Work Elements

A work element is the smallest unit of work that can be done independently by one worker or one machine.

An element may one worker operating many machines (OWMM).

The goal in line balancing is to combine work elements into work stations so that each workstation has the same work load. (Or approximately the same work load.)

A workstation may be one work element or many work elements.

The minimum number of workstations necessary for each line flow must be calculated.

© 2014 Lew Hofmann

Immediate Predecessors

The work element or elements that must be completed immediately before the next element can begin.

Similar to precedent activities in project management

A diagram of work elements and their relationships is called a Precedence Diagram. (Similar to Project Management)

Work elements are denoted by nodes (circles or squares), and contain the time required to perform that work.

© 2014 Lew Hofmann

Precedence Table

Work Elem. Time (seconds) PredecessorA 40 NoneB 80 AC 30 D,E,FD 25 BE 20 BF 15 BG 120 AH 145 GI 130 HJ 115 C,I

720

A precedence table lists all of the work elements and the immediate predecessors, if any, of each element.

© 2014 Lew Hofmann

A 40

B 80

G 120

H 145

D 25

E 20

F 15

C 30

I 130

J 115

Work Elem. Time (seconds) PredecessorA 40 NoneB 80 AC 30 D,E,FD 25 BE 20 BF 15 BG 120 AH 145 GI 130 HJ 115 C,I

720

Precedence Diagram

© 2014 Lew Hofmann

Line Balancing Terms

WORK STATION:A work station is a grouping of one or more work elements.

CYCLE TIME:Cycle time is the maximum time allowed for a workstation to complete its work on a given product/service before passing it on to the next workstation.

Exceeding the cycle time at any workstation means the day’s production quota won’t be met.

NOTE: Cycle time is NOT the time it takes to do the work-elements at a workstation, but the maximum time a workstation is allocated to complete its work.

© 2014 Lew Hofmann

Desired Output Rate

This is the target production output (quota) for a given period of time. (Units of output per shift or per day, etc.)

If the cycle time (maximum time) is exceeded at any workstation, the desired output (quota) for the shift cannot be achieved.

Line balancing focuses on combining work elements into equally-balanced workstations so as to best meet the desired output.

© 2014 Lew Hofmann

Computing the Cycle Time

Cycle time is the maximum time a workstation can spend working on one widget and still meet the desired output.

Cycle time is how how much time is allocated to make one widget, given a desired output rate (quota) and time period.

If we wish to make 192 units in an 8-hour shift, how long do we have to make one widget? (192 widgets/8 hours)

8 hours = 28,800 seconds

28,800 seconds / 192 = 150 seconds to make each widget.

Cycle Time (C) = 150 seconds

Desired Output = 192 per 8 hr shift

© 2014 Lew Hofmann

Theoretical Minimum # of Workstations

What is the Minimum # of Workstations needed to achieve the desired output?

A perfectly balanced line would have the necessary minimum # of workstations, each having the same work load.

Add up the total time for all work elements and divided it by the maximum time allowed to make one widget. (Cycle Time)

Work Elem. Time (seconds) PredecessorA 40 NoneB 80 AC 30 D,E,FD 25 BE 20 BF 15 BG 120 AH 145 GI 130 HJ 115 C,I

720

Theoretical Minimum # of workstations =

the sum of all work stationsdivided by the cycle time

Desired Output = 192 per 8 hr shiftCycle Time = 150

720 / 150 = 4.8 work stations

Round up to 5 work stations.

© 2014 Lew Hofmann

• The theoretical # of workstations is 4.8, but the actual number of workstations has to be 5.• Thus the line will not be 100% efficient.

• In most situations it is impossible to have a 100% balanced line.

• In a balanced line, no one is waiting for anyone else.

• Balance delay is the amount (%) you fall short of 100% efficiency. (There is some idleness.)

• A 90% efficient line would have a 10% balance delay.

• Desired Output = 192 per 8 hr. shift• Cycle Time = 150• Min. Work Stations = 5

Balance Delay

© 2014 Lew Hofmann

Computing Efficiency

Work Elem. Time (seconds) Predecessor

A 40 None

B 80 A

C 30 D,E,F

D 25 B

E 20 B

F 15 B

G 120 A

H 145 G

I 130 H

J 115 C,I

720

Desired Output = 192 per 8 hr shiftCycle Time = 150Minimum # workstations = 5

The theoretical number of workstations is 4.8

We had to round that up to 5.0 workstations.

4.8 is 96% of 5 (4.8 / 5 = .96)

Thus our system is 96% efficient. (4% Balance Delay)

(4% of the time someone is idle.)

© 2014 Lew Hofmann

Establishing Workstations

B 80

D 25

E 20

F 15

H 145

C 30

I 130

J 115

Group the 10 work elements into five workstations, with each as close to the 150 second cycle time as possible.

A 40

G 120

Start with the work element that has the highest time and work down.

In this example, there are no constraints for grouping work elements. In the real world, there would be many more elements and many constraints.

© 2014 Lew Hofmann

Another line balancing example:Green Grass, Inc.

Green Grass, Inc., a manufacturer of lawn & garden equipment, is designing an assembly line to produce a new type of fertilizer spreader. Using the following information, construct a precedence diagram it’s assembly.

© 2014 Lew Hofmann

© 2007 Pearson Education

Line Balancing Green Grass, Inc.

6

E20

H

18

I

40

D

30

B

25

F

50

C40

A

15

G

Desired output is 2,400 units per 40-hour week or 60 units per hour.

If you have to make 60 per hour, that is one ever minute. Cycle time = 1 min.

or 60 seconds

Minimum # workstations is then 244 seconds divided by the cycle time. 244/60 = 4.067 workstations.

Round up to 5 workstations

© 2014 Lew Hofmann

Efficiency (%)

= the theoretical # of workstations / actual # of workstations

= 4.067 / 5 = .813 or 81.3%

Idle time is the total unproductive time for all stations in the assembly of each unit. This is also called Balance Delay.

Balance Delay is the amount by which efficiency falls short of 100%. (100% - 81.3%) = 18.7%

Desired Output is 60 units per hour.

Cycle Time is 60 seconds per unit.

Minimum Workstations is 5

© 2014 Lew Hofmann

© 2007 Pearson Education

S1

S2S3

S5S4 6

E20

H

18

I

40

D

30

B

25

F

50

C40

A

15

G

Line Balancing Green Grass, Inc.

c = 60 seconds/unitTM = 5 stationsEfficiency = 81.3%

The goal is to cluster the work elements into 5 workstations so that the number of work-stations is minimized, and the cycle time (c) of 60 seconds is not violated. Here we use the trial-and-error method to find a solution, although commercial software packages are also available.

© 2014 Lew Hofmann

Four Homework Problems(Due in one week)

(No computer use is needed)

Depts. Trips Areas

A 250 2

B 180 1

C 390 3

D 320 2

E 100 4

F 190 1

G 220 1

#1. Solve the warehouse layout below.

Dock Aisle

© 2014 Lew Hofmann

Homework Problem # 2The closeness matrix below shows the daily trips between six department offices. The block diagram shown is one solution being proposed.

1. Just looking at the matrix, which two offices should be located closest?

2. What is the total weighted-distance for the proposed layout?

3. Can you find a better layout?

© 2014 Lew Hofmann

Homework Problem # 3: Line Balancing

Work Time Immed.Element (Sec.) Pred.

A 20 NoneB 55 AC 25 BD 40 BE 5 BF 35 AG 14 D,EH 40 C,F,G

Draw the precedence diagram for following situation. Using a desired output of 40 units per hour, calculate the following:

• Cycle Time• Theoretical Minimum• System Idle Time• Efficiency• Balance Delay• Group the work elements

into the Theoretical Minimum # of work stations.

© 2014 Lew Hofmann

Homework Problem # 4: Line Balancing

Work Element

Time (min)

Immediate Predecessor(s)

A 3 None

B 5 A

C 2 B

D 7 B

E 7 C,D

F 6 E

G 2 D,E

H 3 F

I 8 G

J 6 H

K 3 I,J

L 8 K

What Cycle Time corresponds to the desired output rate?

A. Identify the best possible line-balancing solution. (Note that you may not be able to group them into the theoretical minimum number of work stations.)

B. What is the impact on your solution if the time for work element D increases by 3 minutes?

E. What is the impact if the time for element D decreases by three minutes?

The desired output is 60 items in a ten-hour day. Using the work flow information provided in the table, draw a precedence diagram.