7. Integration Issues

7.1 Corporate Structures

• First consider the major functions within a company,

Production

Materials

Process Planning

Design

Customer Orders / Service

Marketing

Accounting

Management

• All of these functions generate and use common information which must be communicated between departments.

• Since computers handle information, we must be aware of what we get, and what we produce.

7.2 Corporate Communications

• Previous paper based systems provided support for data transfer between departments, and provided a good basis for the introduction of computers

• ASIDE: Computers can make a good system better, but they will always make a bad system worse. This is because a system which is not well defined and poorly understood cannot be programmed, or optimized.

• Characteristics of paper based manufacturing systems,

Multiple copies of same information.

Revising information is hard when multiple copies exist.

Delays for the transfer of paper.

Easy to lose paper.

Paper is not interactive.

Paper requires bulky storage.

• Computers overcome and reduce the problems above, but introduce some technological challenges,

Creating programs to support corporate functions.

Software to support interdepartmental communication and data sharing.

Hardware to support the software.

• This figure below shows various departments, and the information flow [source: ???

• Requirements for interfacing corporate management and staff functional entities to the factory [source: find]

• Assumed functional hierarchy computer system structure for a large manufacturing complex [source: find]

• Report interfacing to corporate management and staff functional entities from the factory [source: find]

• The Shop Floor Production Model (SFPM):

[ source: find]

 

 

Level

Sub-Activity

Responsibility

 

4

 

Section/Area

Supervise shop floor production process

Supervising and coordinating the production and supporting the jobs and obtaining and allocating resources to the jobs.

 

3

 

Cell

Coordinate shop

floor production process

Sequencing and supervising the jobs at the shop floor production process

 

2

 

Station

Command shop floor production process

Directing and coordinating the shop floor production process

 

1

 

Equipment

Execute shop floor production process

Executing the job of shop floor production according to commands

The ISO Reference Model for Factory Automation adds a couple of layers

[ source: find]

 

Level/Hierarchy

Area of Control

Responsibility

Basic Functions

6 /

Enterprise

Managing the corporation

Achieving the enterprise’s mission and managing the corporation

Corporate management

Finance

Marketing and sales

Research and Development

5 /

Facility or plant

Planning Production

Implementing the enterprise functions and planning and scheduling production

Product design and production engineering

Production management (upper level)

Resource management (upper level)

Procurement (upper level)

Maintenance management (upper level)

4 /

Section or area

Allocating and supervising materials and resources

Coordinating production and obtaining and allocating resources to jobs

Production management (lower level)

Procurement (lower level)

Resource management (lower level)

Maintenance management (lower level)

Shipping

Waste material treatment

3 / Cell

Coordinating multiple machines and operations

Sequencing and supervising shop floor jobs and supervising various supporting services

Shop floor production (cell level)

2 / Station

commanding machine sequences and motion

Directing and coordinating the activity of the shop floor equipment

Shop floor production (station level)

1 / Equipment

Activating sequences and motion

Taking action on commands to the shop floor equipment

Shop floor production (equipment level)

• A LAN (Computer Network) Hierarchy for Shop Floor Control [source: find]

• Typical Architecture for Manufacturing Components [ update]

 

Item

Equipment

Workstation

Cell

EXAMPLES

 

Hardware

Lathe, Mill, T-10 Bridgeport Series I IBM 7545 Robot

Robot tended Machine Center, Cartrac Material Handling System

Variable Mission System, Several Integrated workstations

 

Controller Hardware

Mark Century 2000, Accuramatic 9000, Custom-single-board system.

Allen-Bradley PLC-5, IBM-PC, etc.

Windows NT, SUN workstation, etc.

Type Controller

Single-board processors, Machine tool controller, Servo-Controller, etc

PLC, PC, Minicomputer

PC, Microcomputer, Super-MiniComputer

Language Application

Assembler, Part programming, Robot programming, etc.

C, Ladder logic, Pascal and other sequential languages

C, LISP, FORTRAN, and other high level languages

Memory/Size Requirements

8k-128k RAM plus custom ROM, EPROM, etc.

32M RAM, >1M Hard Drive

128M RAM, >1Gigabyte Hard drive

Response Time

< 10-3 sec

< 1 sec

< 20 sec

Machines/ Interconnects

1-1 connect

1-many

1-[1,8] Machine tools,

1-[1-50] Material handling

1-many

1-[1-15] workstations

• Functional Breakdown of Control Architecture

 

 

 

Equipment

Workstation

Cell

Planning

Tool selection, parameter specification, tool path refinement, GMT code, tool assignment to slots, job setup planning

•Resource allocation jobs

•Batch splitting and equipment load balancing

Batching, Workload balancing between workstations, Requirements planning

Task allocation to workstations

Planning Horizon

Milliseconds: Minutes

Minutes: Hours/Days

Hours: Days/weeks

Scheduling

•Operation sequencing at individual equipment

•Sequence equipment level subsystems

•Deadlock detection and avoidance

•Gantt chart or E.S. based scheduling

•Buffer management

•Assignment of due dates to individual workstations

•Look ahead ES/simulation based scheduling

•Optimization based tech

•Batch sequencing

Control

•Interface to workstation controller

•Physical control (motion control at NC and robot pick and place level)

•Execution of control programs (APT, AML, etc.)

•Monitor equipment states and execute part and information flow actions based on states

•Synchronize actions between equipment (eg. robot & machine while loading/unloading parts)

• Ladder logic execution

Organizational control of workstations, Interface with MPS, generation of reports, etc.

• In all of these models we must consider the value of the information being passed. At the low level control stages, information that is more than a few seconds old may be completely worthless, while the same information at the higher level may be valuable for quality tracking months later.

• We can draw part of a simple flow chart that illustrates a simple CIM system. The elements shown include a PLC, NC machine, and stand alone sensors. These are all integrated by a single computer running cell control software.

 

7.3 Computer Controlled Batch Processes

• The nature of Batch processes,

Batch processes deal with discrete quantities of raw materials or products.

batch processes allow the tracking of these discrete quantities of materials or products

batch processes allow more than one type of product to be processed simultaneously, as long as the products are separated by the equipment layout.

Batch processes entail movement of discrete product from processing area to processing area

Batch processes have recipes (or processing instructions) associated with each load of raw material to be processed into product.

Batch processes have more complex logic associated with processing than is found in continuous processes

Batch processes often include normal steps that can fail, and thus also include special steps to be taken in the event of a failure.

• The nature of steps in a batch process,

Each step can be simple or complex in nature, consisting of one or more operations

Generally, once a step is started it must be completed to be successful.

It is not uncommon to require some operator approval before leaving one step and starting the next.

There is frequently provision for non-normal exits to be taken because of operator intervention, equipment failure or the detection of hazardous conditions.

Depending on the recipe for the product being processed, a step may be bypassed for some products.

The processing operations for each step are generally under recipe control, but may be modified by operator override action.

• A typical process step

7.4 Problems

Problem 7.1 List 5 industries that are well suited to integration, and 5 that are not. Indicate why you think so.

Problem 7.2 In an automated factory there as many as six levels of control. Discuss the equipment available in the lab and how this relates to the 6 level model of factor floor control.

Answer 7.2 The lab equipment (right now) only satisfies the first couple of levels. You can argue that the ability to watch over the net is a supervisory function. Etc...

Problem 7.3 Information drives an automated factory from the initial entry of geometry in CAD, to the final production of parts with CAM. Discuss how data networks support this and the impact of open network standards.

 

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