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Flexible fabrication - a progress report.

Flexible fabrication-A progress report

One of the dramatic success stories in metalworking technology is that of flexible fabrication systems (FFS). In a period of just five years, the FFS has acquired capabilities and sophistication rivaling those of even the most advanced chipmaking systems.

Today, an FFS can run small or midsize batches of parts quickly and cost-effectively. CNC programming for these systems is fast and easy, and individual machines have been integrated far better--both mechanically and electronically--than before.

Now less expensive, more accurate, and easier to regulate than previously, laser cutters often are combined with punch presses in fabrication centers. And computer power, particularly DNC and nesting software, have transformed the entire FFS technology.

Indeed, flexible fabrication no longer need take a back seat to other types of metalworking.

Computer's arms

According to FFS suppliers, the most important, far-reaching advance in recent years has taken place in development and application of computer systems, particularly software. This change is so profound that today an FFS is really a mechanical extension, the arms and tools, of a computer.

In fact, say the experts, once you have a mechanical system that works well, and a suitable computer system, then all you need do is make the software perform more and better work. Speed, versatility, and quality production have become functions of software and controls.

Wilson Lundy Jr, executive vice-president of Optimation Inc, Las Cruces, NM, observes tha five years ago, fabrication machinery actually had more flexibility than did the software. "It was so difficult and time-consuming to generate NC code and nests that instructions were used repetitively, and managers put their emphasis on preplanning," he says. "Only midsize or large lots could be produced cost-effectively. A number of parts could be grouped in a nest, allowing several orders to be processed in parallel, but the time invested to create that one nest caused it to be used for processing large numbers of sheets.

"Now, though, programming for fabrication has matured to where the term nesting software implies limited capability. Today's software is better termed a dynamic production planner.

"Schedule and machine throughput are honored, along with material utilization, so you can change NC instructions and nest patterns quickly and easily on the fly. Using the latest AS/RS loaders, punches, shears, sorters, and so on, you can feed one sheet right after another, changing sheet sizes and gauges, and produce what's needed in small quantities--even quantities of one."

In some cases, FFS control has been handed over from programmable logic controllers (PLCs) to high-powered microcomputers. "We're now using micros to provide direct control of CNCs in flexible cells and systems," reports Jack Rosa, FFS manager for Wiedemann Div, Warner & Swasey Co, King of Prussia, PA. "In our systems, the role of PLCs has diminished.

"Furthermore, CNCs are now much more intelligent than previously, and have acquired more functionality," he adds. "They're better able to converse with computers on DNC networks, and can hold tighter accuracies and move tables faster. Servo mechanisms and motors have improved greatly, too."

Higher integration

Another major advance is integration of production machines, auxiliary equipment, and software into unified, automated systems that can run untended. A fully automated FFS may include an AS/RS, automatic loader, CNC punch press or fabrication center, automatic tool-changer, transfer mechanisms, and equipment for automatic shearing, parting, scrap removal, part sorting, and stacking.

"Some of the new systems also can take sheets through four sides of automated forming," points out Russ Branton, marketing manager for Salvagnini America Inc, Hamilton, OH. "These systems perform not only punching, cutting, shearing, and so on--the traditional processes--but also bending, with a different geometry on each side."

Among recent mechanical advances for FFS are the automatic tool changer (ATC), rotary tool indexer, and a variety of equipment for unloading and sorting. Supplied with capacities from 25 to over 400 tools, ATCs provide flexibility in much the same way as tool magazines and carousels for CNC machining centers.

Rotary indexers perform rapid, fully automatic tool-indexing. In some punch presses, automatic, CNC-controlled angling of the tool is afforded.

To get the most from an FFS or a flexible fabrication cell (FFC), the user needs automated unloading and sorting, points out Stuart Ingram, sales manager of advanced products at Trumpf Inc, Farmington, CT. "Imagine having 25 different parts nested on a sheet," he says. "Manually unloading and sorting this variety of parts would be extremely slow, and it's likely errors would occur.

"To meet the need for automating these functions, we provide several kinds of unloading mechanisms and sorters, all controlled from the nesting software. One popular mechanism is a traveling frame with programmable suction cups. Parts are dropped onto pallets positioned by a chain conveyor that travels back and forth. For small parts, we usually recommend dropping the separated parts down a chute onto a conveyor, and sorting them into bins from there."

In the area of computers and controls, CNC and nesting systems now can be linked with CAD/CAM, MRP, scheduling, and production control systems. As a result, fabrication cells and systems are integrated not only mechanically but also electronically.

"The justification for these computer-integrated systems is a tremendous increase in throughput, plus a capability to make small quantities for just-in-time requirements," points out Wilson Lundy Jr. "Full integration frees you from the discontinuities that arise when you rely on poorly orchestrated human activity. You gain ease of control, along with a great improvement in production flow."

Cells debut

Another recent development is the FFC. Designed for smaller, simpler production requirements than those met by FFS, an FFC usually is comprised of a CNC punch press or fabrication center, automatic tool-changer, and automatic loader. An FFC may also include an unloader and sorter. An automatic nesting system is considered standard.

"A cell has all the characteristics of a larger, more complex FFS, but takes up less room and coss less," explains Howard Abbott, president of C Behrens Macinery Co, Danvers, MA. "Cells provide low cost per part, with good control over flow and quality."

Because they may be required to produce small quantities of many different part geometries, FFCs generally need large tables and trap-doors. For instance, a buyer may specify a 96"-wide table instead of a 78"-wide, and a 60" throat opening. The price of an FFC with laser/punch center, material-handling equipment, and computer with nesting software runs from $500,000 to $750,000.

More lasers

Five years ago, you seldom saw a laser cutter being used in a fabrication center. Nibbling was the norm, because industrial lasers were, generally speaking, relatively expensive, difficult to program and regulate, and not highly accurate.

Now, though, laser cutters are practical and cost-effective. A few suppliers, including C Behrens Machinery Co, promote laser application. "We push for the combination punch press and laser," says Howard Abbott. "A high percentage of users need to produce contoured parts as well as rectangular ones. You can make contoured parts much faster and more economically with a laser cutter.

"What's more, large tool magazines are expensive. It's nice to work from a 300-tool magazine, but the tools are costly, and must be sharpened, moved around, programmed, and tracked. A laser is more flexible; it lets you minimize tool inventory, changing, maintenance, and so on."

But the tools--whether punches, lasers, or a combination--must be chosen to suit production needs, adds Mikko Lindstrom, vice-president of Finn-Power International Inc, Elk Grove Village, IL. "The choice really depends on geometries of parts to be made," he says. "A laser is good for contouring complex parts, and then for parting.

"At the same time, however, buyers must remember that a laser has its own cost. Besides the initial outlay, there are costs for electricity, gas, and maintenance."

The payoff

Recent advances in flexible fabrication technology are already yielding impressive benefits. "Our customers say they now enjoy lower material inventories, lower labor costs, better responsiveness to customer needs, and fast job turnaround than were previously possible," says Michael Donnelly, vice-president of W A Whitney Corp, Rockford, IL.

"Users also report higher part quality, greater consistency in quality, fewer errors, and less scrap. Another benefit cited by many users is the ability to change sheets, tools, and NC programs quickly. This makes it possible to run small lots economically, and to provide just-in-time service."

Mark Barszcz, systems product manager for Strippi Inc, Akron, NY, points out that improvements in FFS technology have had a profound effect on cost per part produced. "With an advanced system or cell in place, you can make one part of 1000 parts at almost the same cost per part," he says. "This is especially important to fabrication job shops, and to fab departments in large manufacturing companies practicing just-in-time."

Side-effects

An important side-effect of flexible fabrication's growing sophistication is that buying and installing a cell or system requires much more planning and resource allocation than previously.

"Smart buyers realize that an FFS or FFC is not a standalone product," says Jack Rosa. "Sound project management is now of paramount importance.

"Unfortunately, a few buyers still approach FFS the same way they would standalone machine tools. Doing so invariably leads to failure and disappointment.

"To meet the increased need for better project management, we suppliers have staffed our organizations not only with fabrication experts, but also with specialists in project management and computer programming," Rosa continues. "Our more intelligent customers also hire such experts.

"Project management for flexible fabrication extends into many areas, including site preparation, production management, hiring, training, and software--as well as hardware considerations. In fact, advanced fabrication technology reaches into and affects virtually all aspects of a user's business."

Another side-effect of technology's advance is a change in the operator's role. "In mot FFSs in the field, the operator still performs supervision of punching, loading and deleting NC programs, and moving tools," says Mikko Lindstrom. "But in our latest systems, the operator is not directly involved with machinery.

"Instead, he does general supervision of the operations, and performs functions that cannot readily be automated. Examples are cleaning and kitting tools, watching for malfunctions and material hangups, and replenishing sheets in the AS/RS."

What's next?

As you can see, flexible fabrication has made tremendous strides during the past half-decade. What further developments can you expect during the next five years?

Several experts think FFCs will continue to improve in flexibility, particulary in random nesting. Wilson Lundy Jr says the enxt big leap will come in the application of FFS computer technology.

"We fare going beyond the FFS itself, and orchestrate processes downsteam," he says. "New software systems allow dynamic production planning for other machines, stations, and cells such as press brakes, stamping presses, welders, and finishing stations.

"A system is being implemented now that will orchestrate processes and material-handling systems so parts automatically come together for assembly kits. Further, the user will be able to dynamically balance assembly lines for labor usage fand model mix. Software development and application are the keys to these advances."
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Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Author:Quinlan, Joseph C.
Publication:Tooling & Production
Date:Mar 1, 1989
Words:1833
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