Operations7

473.31

Fall 2015

Bruce Duggan

Providence University College

This Week’s Project

Vehicle Salvaging:• Process Flowchart• Precedence Graph

1Check for Spare Tire

[? min]

Is there a spare tire?

Is the tire in good shape?

yes

no

yes

no

yes

Is the rim aluminum

?

3Leave tire on

rim[? min]

2Take it out

[? min]

yes

4Put in good

tire bin[? min]

(from 3)

Summary

Many factories use a combination of layouts• workcentres for some parts

• assembly operations for others

Service businesses are in many ways similar to manufacturing businesses

Service design must consider• the high degree of personalization

often required

• the speed of delivery needed

• the direct customer contact

• the inherent variability of service encounters

6-20

Know The Answers To These Questions1. What is the difference between an “assemble to order” process and a “make to order” process?

2. How else, other than an assembly line, can a production process be organized?

3. What calculation can be used to help determine if investing in equipment for a process is worthwhile?

4. Should services be classified by degree of customer contact or by degree of labour intensity?

5. How do you determine the required “pace” (cycle time) for an assembly line and how do you determine how many people are needed to work on the line?

6. How can changing a facility layout reduce waste and increase capacity?

6-21

Organization of Production ProcessesProject layout• The product, because of its sheer volume or weight remains fixed in a location

Workcentre• A process structure suited for low-volume production of great variety of

nonstandard products

Manufacturing cell • An area where simple items that are similar in processing requirements are

produced

7-3

Organization of Production ProcessesAssembly Line• A process structure designed to make:

o discrete partso moved through a set of specifically designed workstationso at a controlled rate

Continuous process• An automated process that converts raw materials into a finished product in

one continuous process.• Similar to assembly line, but the flow is continuous, not discrete.

Product-Process Matrix

Break-Even Analysis

A standard approach to choosing among alternative processes or equipmentModel seeks to determine the point in units produced (and sold) where we will start making profit on the process or equipment Model seeks to determine the point in units produced (and sold) where total revenue and total cost are equal

7-6

Break-Even Analysis Formula

This formula can be used to find any of its components if the other parameters are known

break-even demand =

purchase cost of process or equipment

total fixed costs of process or equipment

price per unit

cost per unit

unit price to customer

variable cost per unit

Break-Even Analysis Example

Suppose you want to purchase a new computer that will cost $5,000. It will be used to process written orders from customers who will pay $25 each for the service. The cost of labour, electricity and the form used to place the order is $5 per customer. How many customers will we need to serve to permit the total revenue to break-even with our costs?

break-even demand =

total fixed costs of process or equipment $5,000

= 250 customersunit price to

customervariable cost per unit

$25 $5

Designing a Production System

Project Layout• Visualize the product as a hub of a wheel, with materials and equipment

arranged concentrically around the production point.

Workcentres• Arrange workcentres in a way that optimizes the movement of material.

Designing a Production System

Workcentre Layout

Designing a Production System

Manufacturing Cell• Group parts with common machine requirements into families. • Identify dominant flow patterns for each part family.• Machines and the associated processes are physically grouped into cells.

Designing a Production System

Manufacturing Cell

Designing a Production System

Assembly Line Layout• Assembly line layout design is for the special purpose of building a project by

going through a series of progressive steps or ‘stations’• Stations are linked by a material-handling device. • There is usually some form of pacing by which the amount of time allowed at

each station is managed.

Designing a Production System

Continuous Process Layout• Continuous or flow process is similar to an assembly line except the product

moves continuously through the process.

Classification of Services

Service systems• Generally classified according to:

o who the customer is o the service provided to them

• Customer is involved in the production process• Service systems with a high degree of customer contact are more difficult to

control than those with a low degree of customer contact

Service-System Design Matrix

Assembly Line Balancing

1. Specify the sequential relationships among tasks.2. Determine the required workstation cycle time.3. Determine the theoretical minimum number of workstations.4. Assign tasks, one a time, until the sum of the tasks is equal to the

workstation cycle time.5. Evaluate the efficiency of the balance.6. Rebalance if needed.

Assembly Steps and Times: Vortex Hybrid Sedan

Precedence Graph:Vortex Hybrid Sedan

Line Balancing Process:Vortex Hybrid Sedan

Precedence Graph:Vortex Hybrid Sedan

Possible Physical Layout of an Assembly Line

Flexible Line Layouts

End of Chapter 7