AA:6.2 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.
- 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
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Requirements for interfacing corporate management and staff functional entities to the factory
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Assumed functional hierarchy computer system structure for a large manufacturing complex
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Report interfacing to corporate management and staff functional entities from the factory
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The Shop Floor Production Model (SFPM):
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Level
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Sub-Activity
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Responsibility
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4
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Section/Area
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Supervise shop floor production process
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Supervising and coordinating the production and supporting the jobs and obtaining and allocating resources to the jobs.
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3
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Cell
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Coordinate shop
floor production process
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Sequencing and supervising the jobs at the shop floor production process
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2
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Station
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Command shop floor production process
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Directing and coordinating the shop floor production process
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1
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Equipment
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Execute shop floor production process
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Executing the job of shop floor production according to commands
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[ source - find]
The ISO Reference Model for Factory Automation adds a couple of layers
Level/Hierarchy
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Area of Control
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Responsibility
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Basic Functions
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6 /
Enterprise
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Managing the corporation
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Achieving the enterprise's mission and managing the corporation
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Corporate management
Finance
Marketing and sales
Research and Development
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5 /
Facility or plant
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Planning Production
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Implementing the enterprise functions and planning and scheduling production
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Product design and production engineering
Production management (upper level)
Resource management (upper level)
Procurement (upper level)
Maintenance management (upper level)
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4 /
Section or area
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Allocating and supervising materials and resources
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Coordinating production and obtaining and allocating resources to jobs
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Production management (lower level)
Procurement (lower level)
Resource management (lower level)
Maintenance management (lower level)
Shipping
Waste material treatment
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3 / Cell
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Coordinating multiple machines and operations
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Sequencing and supervising shop floor jobs and supervising various supporting services
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Shop floor production (cell level)
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2 / Station
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commanding machine sequences and motion
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Directing and coordinating the activity of the shop floor equipment
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Shop floor production (station level)
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1 / Equipment
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Activating sequences and motion
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Taking action on commands to the shop floor equipment
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Shop floor production (equipment level)
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[ source - find]
A LAN (Computer Network) Hierarchy for Shop Floor Control
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Typical Architecture for Manufacturing Components
Item
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Equipment
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Workstation
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Cell
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EXAMPLES
Hardware
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Lathe, Mill, T-10 Bridgeport Series I IBM 7545 Robot
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Robot tended Machine Center, Cartrac Material Handling System
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Variable Mission System, Several Integrated workstations
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Controller Hardware
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Mark Century 2000, Accuramatic 9000, Custom-single-board system.
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Allen-Bradley PLC-5, IBM-PC, etc.
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Windows NT, SUN workstation, etc.
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Type Controller
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Single-board processors, Machine tool controller, Servo-Controller, etc
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PLC, PC, Minicomputer
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PC, Microcomputer, Super-MiniComputer
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Language Application
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Assembler, Part programming, Robot programming, etc.
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C, Ladder logic, Pascal and other sequential languages
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C, LISP, FORTRAN, and other high level languages
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Memory/Size Requirements
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8k-128k RAM plus custom ROM, EPROM, etc.
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32M RAM, >1M Hard Drive
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128M RAM, >1Gigabyte Hard drive
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Response Time
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< 10-3 sec
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< 1 sec
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< 20 sec
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Machines/ Interconnects
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1-1 connect
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1-many
1-[1,8] Machine tools,
1-[1-50] Material handling
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1-many
1-[1-15] workstations
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[ update]
Functional Breakdown of Control Architecture
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Equipment
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Workstation
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Cell
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Planning
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Tool selection, parameter specification, tool path refinement, GMT code, tool assignment to slots, job setup planning
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Resource allocation jobs
Batch splitting and equipment load balancing
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Batching, Workload balancing between workstations, Requirements planning
Task allocation to workstations
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Planning Horizon
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Milliseconds - Minutes
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Minutes - Hours/Days
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Hours - Days/weeks
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Scheduling
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Operation sequencing at individual equipment
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Sequence equipment level subsystems
Deadlock detection and avoidance
Gantt chart or E.S. based scheduling
Buffer management
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Assignment of due dates to individual workstations
Look ahead ES/simulation based scheduling
Optimization based tech
Batch sequencing
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Control
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Interface to workstation controller
Physical control (motion control at NC and robot pick and place level)
Execution of control programs (APT, AML, etc.)
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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
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Organizational control of workstations, Interface with MPS, generation of reports, etc.
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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.
