SCM Chapter 6 Study Guide

"Sustainable Production is the creation of goods and services using processes and systems that are: non-polluting; conserving of energy and natural resources; economically efficient; safe and healthful for workers, communities, and consumers; and socially and creatively rewarding for all working people." To achieve this, the Lowell Center advocates designing and operating processes in ways that:

-"wastes and ecologically incompatible byproducts are reduced, eliminated or recycled on-site; -chemical substances or physical agents and conditions that present hazards to human health or the environment are eliminated; -energy and materials are conserved, and the forms of energy and materials used are most appropriate for the desired ends; and -work spaces are designed to minimize or eliminate chemical, ergonomic and physical hazard." To achieve these goals, business organizations must focus on a number of factors that include energy use and efficiency, CO2 (carbon footprint) and toxic emissions, waste generation, lighting, heating, cooling, ventilation, noise and vibration, and worker health and safety.

Process technology and information technology can have a profound impact on:

-Costs -Productivity -Competitiveness

Basic Layout Types

-Product layouts -Process layouts -Fixed-Position layout -Combination layouts

Line Balancing Procedure

1. Identify the cycle time and determine the minimum number of workstations. 2. Make assignments to workstations in order, beginning with Station 1. Tasks are assigned to workstations moving from left to right through the precedence diagram. 3. Before each assignment, use the following criteria to determine which tasks are eligible to be assigned to a workstation : a. All preceding tasks in the sequence have been assigned. b. The task time does not exceed the time remaining at the workstation. 4. Assign the task with the greatest number of followers. Break ties that occur with assigning the task with the longest task time. If there is tie, choose one task arbitrarily. 5. After each task assignment, determine the time remaining at the current workstation by subtracting the sum of times for tasks already assigned to it from the cycle time. 6. Continue until all tasks have been assigned to workstations. 7. Compute appropriate measures (e.g., percent idle time, efficiency) for the set of assignments. *

The Need for Layout Planning

1. Inefficient operations -High cost -Bottlenecks 2. Accidents or safety hazards 3. Changes in product or service design 4. Introduction of new products or services 5. Changes in output volume or product mix 6. Changes in methods or equipment 7. Changes in environmental or other legal requirements 8. Morale problems

The basic objective of layout design is to facilitate a smooth flow of work, material, and information through the system. Supporting objectives generally involve the following:

1. To facilitate attainment of product or service quality. 2. To use workers and space efficiently. 3. To avoid bottlenecks. 4. To minimize material handling costs. 5. To eliminate unnecessary movements of workers or materials. 6. To minimize production time or customer service time. 7. To design for safety.

Precedence diagram

A diagram that shows elemental tasks and their precedence requirements - Tool used in line balancing to display elemental tasks and sequence requirements

Flexible Manufacturing System (FMS)

A group of machines designed to handle intermittent processing requirements and produce a variety of similar products -Have some of the benefits of automation and some of the flexibility of individual, or stand-alone, machines -Includes supervisory computer control, automatic material handling, and robots or other automated processing equipment

Computer Integrated Manufacturing (CIM)

A system for linking a broad range of manufacturing activities through an integrated computer system Activities include -Engineering design -FMS -Purchasing -Order processing -Production planning and control The overall goal of CIM is to link various parts of an organization to achieve rapid response to customer orders and/or product changes, to allow rapid production and to reduce indirect labor costs

Key Aspects of Process Strategy:

Capital Intensity -The mix of equipment and labor that will be used by the organization Process flexibility -The degree to which the system can be adjusted to changes in processing requirements due to such factors as -Product and service design changes -Volume changes -Changes in technology

Cellular Layouts

Cellular production -Layout in which workstations are grouped into a cell that can process items that have similar processing requirements -Groupings are determined by the operations needed to perform the work for a set of similar items, part families, that require similar processing The cells become, in effect, miniature versions of product layouts

Product Layouts: Advantages & Disadvantages

Disadvantages -Creates dull, repetitive jobs -Poorly skilled workers may not maintain equipment or quality of output -Fairly inflexible to changes in volume or product or process design -Highly susceptible to shutdowns -Preventive maintenance, capacity for quick repair and spare-parts inventories are necessary expenses -Individual incentive plans are impractical Advantages -High rate of output -Low unit cost -Labor specialization -Low material handling cost per unit -High utilization of labor and equipment -Established routing and scheduling -Routine accounting, purchasing, and inventory control

Process Layouts: Advantages & Disadvantages

Disadvantages -In-process inventories can be high -Routing and scheduling pose continual challenges -Equipment utilization rates are low -Material handling is slow and inefficient -Reduced spans of supervision -Special attention necessary for each product or customer -Accounting, inventory control, and purchasing are more involved Advantages -Can handle a variety of processing requirements -Not particularly vulnerable to equipment failures -General-purpose equipment is often less costly and easier and less costly to maintain -It is possible to use individual incentive systems

Two key questions in process selection:

How much variety will the process need to be able to handle? How much volume will the process need to be able to handle? Usually, volume and variety are inversely related; a higher level of one means a lower level of the other. However, the need for flexibility of personnel and equipment is directly related to the level of variety the process will need to handle: the lower the variety, the less the need for flexibility, while the higher the variety, the greater the need for flexibility.

Facilities Layout

Layout the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system Facilities layout decisions arise when: -Designing new facilities -Re-designing existing facilities

Fixed Position layout

Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed

Product layout

Layout that uses standardized processing operations to achieve smooth, rapid, high-volume flow -Used for Repetitive Processing -Repetitive or Continuous

Non-repetitive Processing: Process Layouts

Layouts that can handle varied processing requirements -Used for Intermittent processing -Job Shop or Batch

Process Selection

Refers to deciding on the way production of goods or services will be organized It has major implications for -Capacity planning -Layout of facilities -Equipment -Design of work systems Process selection occurs as a matter of course when new products or services are being planned. However, it also occurs periodically due to technological changes in products or equipment, as well as competitive pressures.

Assigning Tasks to Workstations

Some Heuristic (Intuitive) Rules: -Assign tasks in order of most following tasks -Count the number of tasks that follow Assign tasks in order of greatest positional weight. -Positional weight is the sum of each task's time and the times of all following tasks.

Combination Layouts

Some operational environments use a combination of the three basic layout types: -Hospitals -Supermarket -Shipyards For instance, supermarket layouts are essentially process layouts, yet we find that most use fixed-path material-handling devices such as roller-type conveyors in the stockroom and belt-type conveyors at the cash registers. Some organizations are moving away from process layouts in an effort to capture the benefits of product layouts -Cellular manufacturing -Flexible manufacturing systems

Designing Product Layouts: Line Balancing

The goal of a product layout is to arrange workers or machines in the sequence that operations need to be performed

Group technology

The grouping into part families of items with similar design or manufacturing characteristics Design Characteristics: -Size -Shape -Function Manufacturing or processing characteristics -Type of operations required -Sequence of operations required Requires a systematic analysis of parts to identify the part families

Cycle time

The maximum time allowed at each workstation to complete its set of tasks on a unit Cycle time also establishes the output rate of a line Cycle Time= Operating time per day/Desired output rate

Task 1= 0.1 min Task 2= 0.7 min Task 3= 1.0 min Task 4= 0.5 min Task 5= 0.2 min What is the min cycle time and maximum cycle time

The minimum cycle time: the longest task time (1.0) The maximum cycle time: the sum of the task times (0.1+0.7+1.0+0.5+0.2= 2.5 minutes)

Line Balancing

The process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements Goal: -Obtain task grouping that represent approximately equal time requirements since this minimizes idle time along the line and results in a high utilization of equipment and labor Objective: to maximize utilization. to meet a required output rate. Why is line balancing important? 1. It allows us to use labor and equipment more efficiently. 2. To avoid fairness issues that arise when one workstation must work harder than another.

How Many Workstations are Needed?

The required number of workstations is a function of -Desired output rate -Our ability to combine tasks into a workstation Theoretical minimum number of stations N min= Et/Cycle time Where N min= theoretical minimum number of stations Et= sum of task times

Service Layouts

Two key factors: Customer contact Degree of customization Layouts: Warehouse and storage layouts Retail layouts Office layouts

Repetitive

When higher volumes of more standardized goods or services are needed, repetitive processing is used. The standardized output means only slight flexibility of equipment is needed. Skill of workers is generally low. Examples of this type of system include production lines and assembly lines. In fact, this type of process is sometimes referred to as assembly. Familiar products made by these systems include automobiles, television sets, pencils, and computers. An example of a service system is an automatic carwash. Other examples of service include cafeteria lines and ticket collectors at sports events and concerts. Also, mass customization is an option.

Flexible automation

evolved from programmable automation. It uses equipment that is more customized than that of programmable automation. A key difference between the two is that flexible automation requires significantly less changeover time. This permits almost continuous operation of equipment and product variety without the need to produce in batches. FMS (Flexible Manufacturing System) -A group of machines designed to handle intermittent processing requirements and produce a variety of similar products CIM (Computer Integrated Manufacturing) -A system for linking a broad range of manufacturing activities through an integrated computer system

Line Balancing Approach- Heuristic Rules

good but not necessarily the best solutions For instance: Assign tasks in order of most following tasks. -Assign the task with the greatest number of followers. -If tie, assign the task with the longest task time; -If tie again, choose one task arbitrarily.

Programmable Automation

involves the use of high-cost, general-purpose equipment controlled by a computer program that provides both the sequence of operations and specific details about each operation. This type of automation has the capability of economically producing a fairly wide variety of low-volume products in small batches. Numerically controlled (N/C) machines and some robots are applications of programmable automation. Computer-Aided Manufacturing (CAM) -The use of computers in process control, ranging from robots to automated quality control Numerically Controlled (N/C) Machines -Machines that perform operations by following mathematical processing instructions Robot -A machine consisting of a mechanical arm, a power supply, and a controller

Desired Cycle time

is determined by the desired output; that is, a desired output is selected, and the cycle time is computed CT=OT/D where OT= Operating time per day D= Desired output rate

Automation

is machinery that has sensing and control devices that enable it to operate automatically. Generally speaking, there are three kinds of automation: fixed, programmable, and flexible.

Project

is used for work that is nonroutine, with a unique set of objectives to be accomplished in a limited time frame. Examples range from simple to complicated, including such things as putting on a play, consulting, making a motion picture, launching a new product or service, publishing a book, building a dam, and building a bridge. Equipment flexibility and worker skills can range from low to high.

Five basic process types

job shop, batch, repetitive, continuous, and project.

Process technology and information technology can have a major impact on costs, productivity, and competitiveness. Process technology includes

methods, procedures, and equipment used to produce goods and provide services.

Batch

processing is used when a moderate volume of goods or services is desired, and it can handle a moderate variety in products or services. The equipment need not be as flexible as in a job shop, but processing is still intermittent. The skill level of workers doesn't need to be as high as in a job shop because there is less variety in the jobs being processed. Examples of batch systems include bakeries, which make bread, cakes, or cookies in batches; movie theaters, which show movies to groups (batches) of people; and airlines, which carry planeloads (batches) of people from airport to airport. Other examples of products that lend themselves to batch production are paint, ice cream, soft drinks, beer, magazines, and books. Other examples of services include plays, concerts, music videos, radio and television programs, and public address announcements.

Process technology and information technology can have a major impact on costs, productivity, and competitiveness. Information technology (IT) is

the science and use of computers and other electronic equipment to store, process, and send information.

Job Shop

usually operates on a relatively small scale. It is used when a low volume of high-variety goods or services will be needed. Processing is intermittent; work includes small jobs, each with somewhat different processing requirements. High flexibility using general-purpose equipment and skilled workers are important characteristics of a job shop. A manufacturing example of a job shop is a tool and die shop that is able to produce one-of-a-kind tools. A service example is a veterinarian's office, which is able to process a variety of animals and a variety of injuries and diseases.