Tailor blank welding in Europe

Tailor blank welding using laser power is a big, global business. So big that, as a key part of an economic analysis of the industrial laser market, this magazine tracks both the sales of blank welding systems and the growth in the number of blanks sold each year.

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By David A. Belforte

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Tailor blank welding using laser power is a big, global business. So big that, as a key part of an economic analysis of the industrial laser market, this magazine tracks both the sales of blank welding systems and the growth in the number of blanks sold each year.

The list of suppliers of laser blank welders is small, seven companies sell worldwide, and reports of some 17 new suppliers in Japan seem exaggerated.

In the world market the three major blank producing sectors employ different supply procedures. In North America, blanks are supplied by Tier 1 companies who purchase the coils from steel companies who may or may not have corporate ties. In Europe, the steel companies arrange to supply the OEMs from their own subsidiary companies. In Japan, until recently, the OEMs supplied their own blanks. Now a shift to purchasing blanks from steel companies and Tier 1 suppliers is happening. In the secondary markets, Asia and South America, blanks are supplied by a mix of the above procedures.

We visited three major suppliers of laser–welded blanks, located in three countries, during a one–week trip arranged and conducted by the Swiss systems supplier Soudronic. The purpose of the visit was to see high–volume blank welding as performed by different organizations that supply most of the European auto companies. All the blank suppliers visited were associated with a major steel company. The raision d'êcirc;tre for maintaining a blanking operation varied from a desire to sell more steel to the creation of a growing profit center for blank welding.

The first visit was to a Spanish company, Tailor Metal, currently part of the Aceralia Group, located in Pedrola, which is about 300 km northwest of Barcelona. You approach the company by passing by its major customer Opel–both located on a plateau about 30 km outside of Zaragoza.

Tailor Metal is the newest blank welder in Europe, having taken delivery of its first Soudronic unit in 2000. Amazingly, the company had already signed a contract with Opel in February 1999 with the guarantee that it would supply blanks for the Opel Corsa in August of 2000.

Picture this. In December of 1998 Caesar Martin, now the general manager but then the project manager, stood in a greenfield site on this plateau and looked across empty fields to his customer Opel, which was in the final stages of building an assembly plant for the new Corsa model. In 20 months Martin and Francisco Somoza, the current plant manager, had to build a plant, fill it with equipment and start delivering floor panels, wheelhouses and B–pillars to their neighbor. That's a tall order for any company. And they did it.

Today Tailor Metal runs three shifts per day, five days per week producing these parts for Opel on a seven–year contract. In Europe suppliers who are awarded such contracts, essentially the life of the platform, can purchase major systems and expect to recover this investment over the life of that contract.

At Tailor Metal, the new plant was laid out by Martin and Somoza in what is viewed as the most efficient manner. Coils arrive from the steel mill by truck and are off–loaded at the rear of the plant in the blanking area. There a 630–ton press produces blanks, which are then moved via automated shuttle pallets to an integral warehouse located about one–third of the way toward the front of the facility.

This warehouse is artfully designed to maximize storage of blanks prior to laser welding and welded blanks prior to shipment to the auto stamping plants. The warehouse, shown in Figure 1, is fully automated. It is a little disconcerting to be standing in an aisle and have a fully loaded shuttle pallet slide up to you unannounced.

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Figure 1. Automated guided vehicle carries welded blanks to the warehouse.
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In the blank welding section are four Soudronic lines that are served by the automated shuttle system. Each line employs one Trumpf 8kW CO2 laser. All steel welded at the plant is coated, one of the prime reasons that laser blank welding has gained the popularity it has. Today almost all tailored blank welding is done on laser–powered equipment.

According to Somoza, the four lines have sufficient capacity to fill all of Opel's needs and, therefore, Tailor Metal has now accepted contracts from other companies. While there we saw door inners having a chevron–type, nonlinear seam being produced for the VW Polo, a small car being built in large numbers in Pamplona, about 150 km from Zaragoza.

Not only was the Pedrola a greenfield startup, but the company was obliged to train a new work force. Each welding system has one operator. There is a weld specialist on each shift to oversee line uptime and a one–person quality–control operation. Every employee has the go–ahead to stop the line whenever a problem occurs or parts do not meet specifications. However, only the weld specialist, who Somoza calls the Star Welder, can make the necessary system adjustments. No shift differential is offered to employees and yet the three shifts maintain equal production rate. In fact, there is mild competition between shifts to adhere to the posted production results.

We came away from this visit with great respect for the company management who erected a new building, outfitted it with the latest in automated blank fabrication equipment and were delivering blanks to their customer in less than 15 months.

Ensuring a reliable welding process
In the Soudronic process, several features control the parameters that affect seam quality when welding different thickness materials. A mechanical roller presses material from the thicker blanks into the weld gap, producing a zero gap, which is critical in laser blank welding. A hold–down wheel, mounted beside the roller, applies pressure to the thinner material, eliminating mismatch.

A vision system tracks and positions the weld edge, guaranteeing that the laser beam is in optimum position. Another vision system measures the top and bottom seam geometry, ensuring that variations in the process are immediately recognized. In addition, a quality inspection system checks the welded seam for local imperfections, supplying real–time information on process stability.

With these features, even greenfield start–ups, such as those described, can reach full production capacity in a short time. –DAB

Tailor Steel Sidmar in Gent is a sister company to Tailor Metal in Spain. This year, Sidmar's merger with Sollac (France) and Aceralia (Spain) will be approved by the European Com munity, and the company's new corporate name will be Arcelor.

The company has an extensive background in laser blank welding with equipment installed in five plants in Europe and the United States. The facility at Gent is located on the grounds of Sidmar's coated steel rolling mill complex, which facilitates the delivery of coils to the blank welding building. This building was built to accommodate four welding lines and a blanking line setup to produce left– and right–hand welded blanks for PSA (Peugeot), Honda, Daimler Chrysler and Audi as part of a contract awarded to the company in 1999–2000. This facility started up in November of 2000 and had been producing blanks full time ever since.

The layout of the 1200m2, four–welding–line plant is similar to the plant in Spain. Coils of coated metal and high–strength steel enter the building from the rear where a blanking press stamps out the next week's components. Automated pallet shuttles move the blanks to the automated warehouse, which is built along the sidewall of the building. This warehouse extends about two–thirds of the way from the front to the back of the building. It is arranged such that automatic retrieval of blanks can feed the four welding lines. After welding, the blanks are returned to storage prior to shipment to the customer.

Two lines are placed parallel to each other and to the warehouse. The operator's console is situated between the two lines as seen in Figure 2. This arrangement enables two welding lines to be operated by two employees.

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Figure 2. Robots load stamped blanks and unload welded blanks at Tailor Steel.
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The company runs a three–shift–per–day operation, seven days per week. In contrast with Tailor Metal in Spain, a pay differential is offered to second– and third–shift operators. A welding specialist and a maintenance person are on duty each shift.

Changeover of a system to weld a different part that is already in the company's computers takes less than one hour. When a new part is added it takes about six hours for the setup.

To ensure weld quality, the company wire brushes the weld edge of each blanked sheet. This is necessary because the blanking process tends to leave zinc particles on the cut edge, which could cause blowholes in weld zones. For Peugeot, Tailor Steel maintains weld records on each blank for 12 years in case of warranty situations.

Tailor Steel will expand its output next year adding Ford as a customer followed the next year by Renault. General Manager Johan Vandeng berghe told ILS that he expects the laser blanking business to grow by ten percent per year over the next five years.

Voestalpine Europlatinen GmbH (Linz) is the oldest and largest installation of Soudronic laser blank welders. The company installed its first Duplex linear welding system (two welding lines, one laser source) in December of 1997. Since then the company has installed five more Duplex linear welding lines, operates another unit for linear and non–linear prototyping and has a sixth on order for delivery later this year.

Laser power for these lines is supplied by either 6– or 8–kW Trumpf CO2 lasers that are arranged to time–share the beam between weld stations as shown in the photo on page 6. Ac cording to Artur Müllner, Voe st alpine sees laser blank welding as a value–added process. With revenues expected to reach 76 million Euros next year, it is easy to understand the steel company's outlook. So contrary to other steel companies that see blank welding as a means to sell more steel, at this company it's a profit center. At Europlatinen, they take only a normal mark up on the steel they sell the customer.

With its five Duplex lines, Euro platinen can produce up to eight million welded blanks per year. This year that will represent about 13 percent of all the blanks produced in Europe. The recent addition of a second blanking line enables up to 100,000 tons of steel to be processed annually.

The first contract in 1997 was as a second source for left and right inner doors for the BMW 3 Series. This was followed by a succession of contracts from Daimler Chrysler for door inners for the S–Class Mercedes, body side inners and door inners for the Jeep Cherokee and door inners for the PT Cruiser. For BMW, the company took contracts for the 3 and 7 Series body side inners. It welds longitudinal rails for the Audi A4 and A6 and the Skoda Fabia. For PSA (Peugeot), the company welds door inners, rails for 307 and 806 models and cross members for the Citroen Xsara.

The company takes great pride in its ability to produce long weld seams, up to four meters, as exemplified by the Jeep Cherokee side ring shown on this month's ILS cover. The linear welding arrangement of Soudronic systems lends itself to long welding patterns, in either single or multiple blanks.

Müllner expects growth to continue in the laser blank welding market, although laser–welded hydroformed tubing poses a growing threat. He points to tailored side rails that will provide crash protection as a feature that will find more adherents. While admitting that the number of blanks per car may decrease, currently it's three to four per car in Europe, he expects that more cars will be built thus sustaining growth.

Europlatinen runs their operation three shifts per day, six days per week. Shifts are rotated each week, therefore the company does not offer a shift differential, and still there is competition one shift to another to meet expected output and efficiency.

Contrary to the other companies visited, Europlatinen does not have an automated warehouse. A visitor finds the constant traffic of forklift trucks moving welded and unwelded blanks a bit discombobulating at first. Especially after touring two fully automated blank welding facilities, where guided vehicles move all the metal around. When asked about this seemingly labor–intensive approach, Müllner laughs saying, he too thinks about it a lot. However, the ten lines have such a mix of parts that automatic scheduling would be a nightmare. Besides, one of the three machine operators drives the lift trucks because they have the time. The number of blanks on a pallet can serve several hours of weld time so it really is quite manageable. After spending several hours in the plant, this becomes evident.

Another difference at Europlatinen is that the operators are expected to maintain and service their systems. Training is therefore extensive, with newcomers put through a one–month on–the–job program.

Laser assist gas is another concern at the company. Welding eight million parts per year means a lot of helium would be used. To keep costs in line Europlatinen uses a novel gas mixture called Lasgon, 50 percent argon, 35 percent helium and 15 percent carbon dioxide. According to operators, this mixture actually improves welding speed in the laboratory but not on the production floor.

We left Europlatinen very impressed by this high–volume operation. This plant was another greenfield startup. Since 1997, there have been three additions and a fourth is in the cards, which will take up the remainder of the site. What will they do? Müllner hints that they might start to follow their customers.

Current activity in the European laser blank welding market appears to mirror activity in the entire auto–producing sector. Industry sources indicate that every global auto company uses tailored blanks. These sources project growth rates in the 25– to 30–percent ranges for the next few years. Worldwide demand in 2002 is projected to be about 120 million blanks. For this year, Europe is expected to produce more than half of this output.

In each of the plants we visited prototype and pre–production applications for nonlinear welds were in advanced stages. Our host, Soudronic, has a new system in its development lab that utilizes Nd:YAG laser power. Company sources indicated this laser is highly regarded as the power source for laser blank welding and they anticipate increased usage in the near–term.

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