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Turning Up The Heat On Cold Forging

You might want to sit down before reading the next sentence. One of your competitors may have just increased its productivity by 600%. Glad you're sitting? Now it's only fair to tell you that you're not in any danger, that is, unless you're cold forging transmission shafts.

Metaldyne's Forming Technologies' facility (Fraser, MI) has completely revamped its approach to shaft manufacturing. Not only has this change increased productivity by the aforementioned amount, but it's reduced their workforce by about two-thirds and quality has improved as well. What's the catch? According to plant manager Chris Jones, there isn't one. The secret to this success? Automated presses.

Bliss press
This single green behemoth--a 2,000-ton Bliss press rebuilt with a automation system--is responsible for dramatic changes at Metaldyne Forming Technologies.

The Past.

Before 1996, Metaldyne was cold forging shafts in a traditional fashion. A billet was cut, lubricated with phosphate and soap, and forged in a press. Then the workpiece was transferred to another press and the process was repeated. To complete the part, it would often require a heat treating cycle to soften the metal, then a third or fourth forging. With 32 manually-fed presses and 150 employees, Jones and company were able to produce an average of 150 pieces per hour. Productivity numbers aside, the process was particularly inflexible. Too much time and labor were being spent on material handling and carrying in-process inventory. Furthermore, design changes from customers would leave unfinished pieces throughout the system left for scrap.

"We looked at our plant and said, `This isn't going to set the world on fire,'" explains Jones. With annual cost reductions on long term contracts doing more to erode profits than to help improve productivity, the motivation to rethink the entire manufacturing process was there. "We envisioned an automatic feed system," says Jones.

The Present

To bring their vision onto the plant floor, Metaldyne looked to one American and three German companies for help. They took an existing 2,000-ton Bliss press and had it rebuilt by Verson (a division of Allied Products Corp., Chicago) to incorporate an automation system from Dreher Automatic-Systeme GmbH (Sulz-Renfrizhausen, Germany). The press was also fitted with a hydraulic eject mechanism built by SMG Pressen (Waghausel, Germany) and tooling from Liebergeld Massivumformung (Nurnberg, Germany). Germanophiles will note that both SMG and Liebergeld are part of Germany's Schuler Group.

The three-station press came online in April 1996, running at 15 strokes/min. and capable of producing 900 pieces per hour. In the three years since, this press has churned out over 5 million complete shafts and single-handedly replaced all the other presses at the Fraser plant.

Schuler Crossbar TBS 6-5800-5-2300
This Schuler Crossbar TBS 6-5800-5-2300 was built for a North American OEM. It has five separate slides, a suction cup crossbar transfer, a hydraulic drawing cushion in the first station and so-called universal stations with up to 7-axis control between the five stations for optimum positioning of the panel.

How can one press do this much? The key is the automation system. To start with, billets are sawn rather than sheared. Although Jones explains that saw cutting the billets is a slower and more expensive procedure than shearing, the even, square cut allows the billets to be precisely measured by the automation system. Billets are weighed on a conveyor scale and passed through an inline die to make sure that they meet specifications. From this conveyor system, the billets enter the press for the first forging via an electric CNC transfer mechanism that not only loads the first die stage, but also moves the workpieces through the process. This motion is coordinated with the computer controlled hydraulic eject mechanism that shoots each piece out of the die; each of the die stations has its own ejector that is set for each different job. After the workpiece passes through the third die, the CNC arm and another conveyor system take the completed part away for shipping.

The main advantage of this system is speed; billets enter the press and exit as completed parts. Gone is the tedious amount of material handling from the conventional cold forging procedure. The need for the heat treatment is also eliminated, since the workpieces stay hot from the first through final forging. An added bonus, according to Jones, is that this constant heat saves wear and tear on the tooling.

Another advantage is that the quality of parts being produced with the automated system has gotten better. Jones explains that the Total Indicator Reading (TIR), the measure of straightness and concentricity of the shafts being produced, has improved because of the multiple concentricity rings in the new press that provide better, more consistent guidance for the billets.

Metaldyne's change in manufacturing process has necessitated more than just a change in machinery, however. There's been a change in attitude as well, for the machine operators, plant management and the engineers.

Where a press used to have a single operator with several support people (setup, quality control, hi-lo operators, etc.), the automated press is manned by just two or three people. But these press operators aren't just loading the press and watching it work; they're doing everything else as well—loading and unloading the automation system, driving the hi-los, taking care of the tooling and die changeovers, and performing maintenance and cleaning on the press itself. If the press goes down, there's no backup, so the work is considerably more varied and demanding. To accommodate this high-pressure pace and increased responsibility, Metaldyne has instituted a new training program.

Schuler Crossbar TBS 6-5800-5-2600
This Schuler Crossbar TBS 6-5800-5-2600 was also built for a North American OEM. It is nearly identical to the 2300 model. The 5800 designation is the total press force, 5800 tons, while the 2300 and 2600 designations are feed pitch in mm.

When the new press first came online, the plant's production system was still designed for their old and slower manufacturing process. This led to the inability to feed the new press fast enough to keep it running—the press was just faster than anyone in the plant could imagine. Plant management quickly corrected the problem by totally revamping production schedules for everything from shipping and receiving to the ordering of tooling and other contracts with outside suppliers. But when Jones describes that day when they realized just how much faster the new press was, the excitement in his eye looks something like a 16-year-old behind the wheel of a '65 GTO.

For the engineers, the new press allows them to design better quality into the manufacturing process. According to Jones, they no longer have to try and design a manufacturing process that's based on making the part with the fewest number of "hits," but can concentrate on making a part with the best dimensional configuration, even if it takes more forgings. Metaldyne has gone to their customers with this development proactively and, as Jones says, "We've been very well received."

The Future

With the current state of competition in the auto industry, it's no great secret that companies who are doing things the same way they did them yesterday aren't going to be in business tomorrow. The new automated press at Metaldyne has put them in a position to be competitive. "It allows us to genuinely entertain the productivity and efficiency improvements that the customer wants," says Jones.

He estimates that the capital investment in the new press and automation system was comparable with the cost of replacing all of their old presses with new models. While the likelihood of any plant completely replacing all their old equipment is admittedly low, Jones is quick to point out that, in this case, the money was well spent. He cites proof in the higher capacity, faster throughput, improved inventory turns and higher quality.

But the single automated press that's changed the Fraser plant forever (and cost Metaldyne approximately $6.5 million) is just the beginning. They are currently in the final stages of a nine-month installation of their second automated press, an identical 2,000-ton Bliss unit (rebuilt by Schuler), and the beginning stage of the installation of a brand new, five-station, 2,000-metric ton automated press line. The automated press line was manufactured by Colombo-Agostino (Monza, Italy), with the automation and tooling from Liebergeld. When the two new presses are both online early next year, it will bring the total annual capacity of the Fraser facility to somewhere in the neighborhood of 11,200,000 pieces.