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Stampers turn to transfer presses.

Stampers turn to transfer presses

Just a few years ago, transfer presses were considered suitable only for very long runs of large parts. Not only were these machines relatively expensive, but also they took a long time - often as much as a week - to set up. Consequently the market for transfer presses was restricted largely to automotive stamping plants.

During the past five years, however, the status of transfer presses has changed markedly. Automakers continue to buy them, but now these presses are used for short runs of small and midsize parts as well as for long, large-part runs.

Appliance makers, too, have been converting from lines of manual stamping presses to smaller numbers of transfer presses. And independent stampers who serve OEMs are adopting transfer. Indeed, this is the hottest technology in metalforming today.

What fuels these fires of change? On one hand, in industries that use large volumes of stampings, demand for greater press flexibility and productivity has increased rapidly. At the same time, in response to these demands, suppliers are making many major improvements and innovations. These encourage wider adoption of the technology.

"I think the big turning point came a few years ago, when General Motors Corp initiated a transfer press program," says Michael Austin, vice-president of Atlas Automation, Fenton, MI. "Because of the program's size, it caught everybody's attention, and got them to focus on transfer technology.

"Not only the automakers, but their suppliers, too, became interested. It has reached a point at which many users look at transfer presses first, then manual line presses. This may not have happened if GM hadn't jumped in with both feet."

Other US automakers are interested, too, according to Michael Reiersen, group director of manufacturing systems for M S Willett Mfg Co, Cockeysville, MD. He reports that Chrysler Motor Corp, for example, has appointed a corporate manager for automation of stamping. All new auto and truck projects are reviewed for possible adoption of transfer technology.

"Introduction of a new car or truck is a fast-paced affair," Reiersen says. "Traditionally, when a new vehicle is released for production, the drawings go to a process engineer. He immediately orders tools and dies for the stampings.

"We're now trying to teach automotive design and manufacturing engineers - especially process engineers - to design stamped parts and their processes for transfer. It's difficult to add transfer mechanisms into the scheme if the parts, tools, and dies were not designed at the outset for transfer."

Job shops, too

Along with OEMs, stamping suppliers gradually are adopting transfer technology. "For a long time, job-shop stampers shied away from transfer presses," notes Ray Gundlach, national sales manager for Niagara Machine & Tool Works, Buffalo, NY. "There was a valid reason for this: A stamper might get an OEM's job one day, but never see it again. So for him, it made good business sense to do the job on a line of manual presses.

"Today, though, many independent stampers receive long-term contracts from their OEM customers. This gives stampers more assurance they can justify investment in transfer technology. As a result, more and more independents are getting into it."

Moreover, stampers' awareness of transfer technolgoy benefits is growing, says Douglas Plank, marketing manager for The Minster Machine Co's Automation Div, Minster, OH. "Material savings and lower die costs invite the transfer to jobs where, prior to just-in-time concepts, progressive dies were used.

"Traditionally, a large percentage of independent stampers have been oriented toward use of progressive dies," he says. "Many stampers either haven't learned about transfer technology, or fear transfer because they lack experience with it. But awareness of automation's benefits, and of the increased number of transfer applications, are forcing the stamping community to raise their educational curve for transfer technology."

According to some sources the move to transfer technology is not peculiar to the US, but is a world-wide phenomenon. "A few years ago, our company sold transfer mechanisms and engineering services in North America only," says James Lehner, sales manager for HMS Products Co, Troy, MI. "Now, however, we're selling worldwide - in Europe, Asia, South America, and elsewhere.

"Even manufacturers who set up shop in foreign countries are buying automated transfer presses. Though hourly wages for factory jobs in certain countries average only 65 cents, manufacturers there can no longer afford to install lines of manual presses."

Lehner points to a major US manufacturer that was contemplating a new stamping plant in a foreign country. "They planned to install 28 manual presses for production of over 500,000 parts a year," he relates. "After analyzing all the projected costs, though, they opted to buy four large straightside presses with transfer mechanisms. Doing so allowed them to build a smaller plant, hire fewer people, increase part quality, meet production quotas, and gain their ROI quickly."

Speeds are up

Generally speaking, today's transfer presses run faster than older models, particularly where the transfer mechanism is powered by an electric servo drive. "Mechanisms with independent servo drives move parts through 10 to 25 percent faster than equivalent cam-driven mechanisms," Austin maintains. "With independent drives, you avoid certain constraints of mechanical drives such as inertia. Moreover, you can fine-tune the timing of transfer and press motions. These advantages yield not only higher speeds, but also greater efficiency."

Another advantage of servo drives, according to some suppliers, is that they enable faster changeover for different parts, through reprogramming of the control. "To take full advantage of this capability, though, you need quick die-change,' stresses Michael Reiersen. "The QDC system must be integrated with the transfer, and it's essential that you be able to move the transfer mechanism out of the way quickly."

Not all suppliers are sold on servo drives, however. US Baird, Stratford, CT, and The Minster Machine Co, Minster, OH, are among press builders that lean strongly toward mechanical drives.

"We're sticking with cam drives," says Werner Allweier, chief engineer at US Baird. "That goes for feeds as well as transfers.

"In our experience, a mechanical approach has fewer potential trouble-spots than does electrical. Also, there's much less hassle with timing between the transfer mechanism and press movements."

Over at Minster Machine, too, press system engineers retain a conservative attitude. "We like the reliability of mechanical cam-driven units," says Douglas Plank. "As electronic controls become more reliable, we'll likely apply them more often. But we think these controls need improvement, and people - especially potential users - need to gain more faith in them. This will take time."

Trend to larger presses

Where lines of manual stamping presses are being replaced by transfer presses, the trend is to install large, wide, straightside machines. "In many cases, the old mechanical presses are too narrow for efficient use of transfer," says James Lehner. "Where an old press is large enough, however, it may be cost-effective to retrofit a transfer mechanism and drive."

Dedicated transfer presses are being ordered with longer beds than previously, notes Douglas Plank. "Stampers want to perform more operations in one press, with one setup," he says. "Benefits of doing this include fewer setups, less part-handling, and less accumulation of work-in-process. In addition, the user enjoys a lower burden rate and smaller workforce."

Of course, putting all this capability into single presses affects the market. "We're selling fewer small presses these days," says Plank. "Those being sold are wider, more efficient, and more flexible than what has been built in the past. As transfer technology gains popularity, we expect sales of large, powerful, straightsides to increase."

The range of transfer capability has risen notably over the past five years, reports James Lehner. "Our transfer mechanisms can now provide pitches of 0 to 60", vertical lift of 0 to 6", and 8" finger travel," he reports.

"Transfer hardware is safer than previously, too. For instance, we routinely transfer on the upstroke, and put mechanical safety clutches in all our servo-mechanically driven transfer mechanisms."

A number of suppliers report the growing need for, and adoption of, a systems approach to transfer technology. "In the early '80s, we supplied primarily standalone presses," observes Douglas Plank. "Now, though, customers want us to provide a solution to their stamping problem, not just a press.

"Within integrated stamping systems, there are numerous types of equipment involved, and the need to integrate hardware and controls is great. Stampers don't maintain staff engineers to do this, so they rely on their equipment suppliers. Minster's Systems Group and Automation Division are results of this demand."

At Niagara Machine & Tool Works, they put together a team of experts for each transfer project. "A team usually is comprised of engineers from a tool and die house and transfer mechanism supplier, as well as from our own company," says Ray Gundlach. "Initially, the customer comes in with a part design. Then the tool people develop tooling, and coordinate their work with the transfer supplier.

"We pull it all together into a coordinated system. Using this team approach gives the customer a better solution, and from a single source."

With their speed, flexibility, and multi-function capabilities, today's transfer presses - or better, transfer systems - are much easier to justify economically than were presses built just five years ago. "Formerly, a stamper would have had to run millions of parts to justify transfer," says James Lehner. "Now, volumes as low as 40,000 can be practical.

"We see many proposals involving runs of 50,000 to 200,000 parts annually. High operating speeds, automated operation, and quick die-change make these smaller runs profitable for the stamper."

Modern equipment is only part of the solution, however. "Cooperation from plant personnel is essential," Lehner stresses, "or the stamper won't get what he could out of a transfer system. It's important to reduce the amount of labor needed to change dies."

PHOTO : This automated stamping system, equipped with transfer mechanism and other equipment from Atlas Automation, produces a mix of 28 parts. These range in length from 11" to 66", and weigh up to 75 lb apiece. The 3-axis transfer mechanism is servo-driven. Quick die-change is aided by a 24-ft die cart.

PHOTO : Installed at a company that makes steel office furniture, this system from The Minster Machine Co has a 3-axis, cam-driven transfer mechanism. Pitch is adjustable over a range of 12" to 48". For changeover, center sections of the transfer bars unclamp and stay with the die.

PHOTO : A Niagara Transtech integrated transfer system, installed at Delwal Corp, Novi, MI. Note the standalone control console, which governs operations of all equipment in the system and provides diagnostics. This controller also monitors transfer position and part flow relative to press ram position.

PHOTO : Minster/GPA transfer mechanisms are provided with cam-driven motions that can be powered directly from the press, or by servomotors. As an option, you can order mechanisms in which all axes of motion are servo-driven.
COPYRIGHT 1989 Nelson Publishing
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Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Title Annotation:includes related article on transfer technology
Author:Quinlan, Joseph C.
Publication:Tooling & Production
Date:Nov 1, 1989
Words:1802
Previous Article:Machining cell integration: the role of the consultant.
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