Printer Friendly

Common cause for machine-control systems.

Common cause for machine-control systems

Computer and control builders once argued that proprietary languages allowed optimum development of specific hardware and software. Today, many engineers understand that what we really need is communication, not private optimization.

Translator programs or postprocessors let machines talk to one another in networks--or receive instructions from central host computers. But that's the hard way. Today, at last, competing machine controls are beginning to talk to each other directly.

The translator veil has been eliminated, or at least reduced to reasonable proportions. For manufacturers, the term Open Architecture joins other jargon expressions such as MAP, Ethernet, and MMS. The acronyms sound complicated, but they represent attempts to simplify interconnections, even as overall systems grow more complex.

To review some basics, CNC stands for computer numerical control; LAN, for local area network; PLC for programmable logic controller (which used to be programmable controlled or PC); and PC for personal computer.

In the late '50s, early numerical control (NC) required a relatively simple punched-tape reader at the machine and some sort of programming device in the office. First systems used a typewriter mechanism to punch holes in the tape, based on handwritten program instructions. The manual effort became computerized to some extent, but no one thought of it as user friendly. Some systems even used punched cards instead of a spool of paper or Mylar tape.

Today, punched tape still serves, but powerful microprocessors streamline operation and allow easy manual data input (MDI) or programming right at the machine tool, if desired. However, most of todays's CNCs also accept external data from floppy discs, magnetic tape, paper of Mylar tape readers, and direct wire to a host computer or network. This works best for complex programs that require an office atmosphere for clear thinking, or for CAD/CAM systems.

Open information flow

We've been talking about numerical control of machine tools, but similar systems with similar problems handle nearly all the data generated on, and fed to, the factory floor. Of course, each machine-tool manufacturer, and each program or computer developer, used his own programming language.

Most languages have nothing in common, so a computer system handling scheduling and other information flow can not talk directly to a network of machine controls. And, even the machine-control network relies on translator--requiring postprocessor programs for each different control brand, and additional hardware.

That's all changing. Open Systems Technology is here. According to Gary Green, senior manufacturing engineer of General Motors Corp, Buick-Oldsmobile-Cadillac Group, and Ralph Mackiewicz, VP, Systems Integration Specialists Co Inc (SISCO), we're throwing off the shackles of high-level tools such as fourth-generation languages (4GL). "These simplify the development of sophisticated plant-management applications within commercially available Relational Data Base Management Systems (RDBMS), but integrating these tools with plant-floor data has been costly because of the variety and proprietary nature of many plant-floor systems," report these authors in a paper delivered at the IPC '91 conference in Detroit this year, sponsored by the Engineering Society of Detroit.

The relief comes in the form of open-systems technology that "encompasses MAP V3.0 networking, RDBMS, and other commercially available application-development tools that can establish process monitoring, communications, and information-management infrastructure needed to effectively build sophisticated plant-management applications that are integrated with plant-floor data and other plant-business systems."

Open systems is a design philosophy, of course. And Mackiewicz and Green point out that we must avoid misconceptions, including the big one: that standards prohibit innovation. They asked, for example, if the home-appliance market lacked creativity because it was slaved to a standard 120 V AC power supply!

The big demo

Last April, at the International Programmable Control (IPC) show, 15 companies organized an interbooth network on the exhibit floor. They called it CONNECT'91, and it used the Manufacturing Message Specification (MMS) international standard protocol. "This communication standard integrated computers, programmable controllers, sensors, robots, NC machines, and other manufacturing devices," says NCMS, the National Center for Manufacturing Sciences, Ann Arbor, MI.

NCMS is part of an overall effort to promote industry-wide acceptance of MMS as the standard manufacturing application-integration protocol. The show network integrated off-the-shelf products using MMS protocol, eliminating the need to create custom interpreters for each proprietary device in the netwrok. Coordinated by SISCO, the network demonstrated shop-floor common database access, eliminating the need to duplicate or manually input information.

All network participants shared information with other booths on the network, and these included AEG/Modicon, AEG Computrol, Allen-Bradley, Applied Integration Management, Digital Equipment Corp, GE Fanuc, Hewlett Packard, IBM, Lotus Development, Mainstream Software Corp, Siemens, SISCO, Square D, Texas Instruments Industrial Automation, and US Data. Relcom and COMM/SCOPE provided taps, cables, and connectors to link the network booths.

The real world

What does an open-architecture network look like in the real world of manufacturing? Saturn's four-million-sq-ft manufacturing and assembly facility in Spring Hill, TN, is a good example. GE Fanuc Automation, Detroit, MI, supplied PLCs, computer numerical controls, MAP communications, and plant-floor computer systems for the huge facility.

A major part of the early planning was the development of standards for the design, implementation, operation, and maintenance of control and information technologies for the factory floor. These standards helped to avoid confusion during installation, and led to a smoother, under-budget, on-time start-up.

Here is a brief rundown of GE Fanuc technology at work in the Spring Hill plant. More than 700 GE Fanuc programmable controllers and 13,000 Genius[TM] I/O modules are scattered throughout the plant, in addition to traditional rack-style I/O. Standards used for PLC integration were tailored to meet the specific needs of the various sections of the Saturn plant: power train, body systems, paint, general assembly, and vehicle testing.

The distributed nature of Genius I/O proved to be particularly useful at Saturn. For example, in the body fabrication area Genius I/O blocks were strung along welding lines hundreds of feet long, linked directly with GMF Robotics welding robots and weld controllers. With conventional I/O, an installation of this scope would have required massive amounts of wiring, but with Genius, only a single twisted pair cable was needed, a major factor in cutting Saturn's overall installation costs.

GE Fanuc's CIMPLICITY[TM] factory-floor software was used throughout the plant in what Saturn called the Manufacturing Process Manager, or MPM. More than 60 Digital Equipment Corp computers based on Digital Equipment's VMS[TM] operating system are running CIMPLICITY software, performing such functions as production monitoring, process alarming, and statistical process control.

The Saturn plant features what is believed to be the largest MAP 3.0 plant-wide networking installation in the world, with several hundred nodes and more than 30 miles of network cabling in the factory's ceiling. More than 250 GE Fanuc PLCs are directly connected to the network, enabling Saturn to gather data on each manufacturing process in the plant and continually monitor quality throughout the system. CIMPLICITY monitoring and control systems provide reports from the MAP network to all of the computers in the facility.

Rounding out the Saturn technology were more than 150 GE Fanuc computer numerical controls, both single and multiaxis. In addition, numerous discrete control devices and specialized controllers were used on special processes and machine tools.
COPYRIGHT 1991 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Miller, Paul C.
Publication:Tooling & Production
Date:Nov 1, 1991
Words:1198
Previous Article:Clamping technology vital to productivity.
Next Article:PC-based manufacturing software.
Topics:


Related Articles
Managing technical data on the factory floor: new type of reporting system takes advantage of existing DNC networks.
IMTS-92: sparks capital spending.
SFP taps CNC PC potential.
The machine control interface.
In-process probing: growing in popularity, it's a powerful tool for quality control in metalworking.
High speed control slashes machining time.
Cost saving reasons to calibrate.
PM feedback: Preventive measures prolong machine tool life, save big bucks. (Editorial Viewpoint).
Computer Numerical Controls revisited. (On the Three "R's").
Hypersonic aero builders reach for every advantage.

Terms of use | Copyright © 2017 Farlex, Inc. | Feedback | For webmasters