547

特集

ヨ ー ロ ッパ 自動 車 産 業 に お け る レー ザ 加 工 の 実 用 化

The Latest Laser Applied Technology of the Auto

Industry in Europe on the Example of the Body in

White Applications of the Volkswagen Golf V

Klaus LOEFFLER

Keywords LASER welding, Autoniohile, Laser cutting, Body iii white, Application,

Laser brazint

1.lntroduction

The use of laser based welding technology on-line in the

body shop at European automotive manufactures, have a

long history starting in the mid 80's. Single laser installa-

tions, mainly to join the roof with the side frame and the

trunk lid brazing application developed to standard applica-

tions used at many car companies (for example: Volvo,

BMW, VW, AUDI, SEAT, DC-Mercedes).

Volkswagen AG started 1992 exploring body-in-white

laser welding with the availability of high power Nd:YAG-

lasers. Laser welding applications got introduced step by

step with each new model in all manufacturing plants since

then. Volkswagen reached with the introduction of the

Golf V in 2004 a percentage of almost 50% laser welded

joints in this car. Volkswagen takes on the global lead in laser based car production.

This paper will describe examples of the laser joining

methods used, and finally, experiences and lessons learned

will be summarized.

2 History of laser technology at Volkswagen

Volkswagen was not the first company to take advantage

of laser welding in the body shop. The known perfor-mance of early CO2 lasers as well as the limited flexibility of

the mirror based beam delivery system made it not a con-sidered alternative joining method for a long time. The

appearance of the first solid state Nd:YAG lasers with the flexibility of directing the beam with a simple fiber optic

cable created a vision at the Volkswagen management to

replace the present joining technology by lasers.

Intensive studies began in the early 1990's, that leaded to

some pilot installation and the first serial installation with

the roof joint of the VW Passat in 1996. From then on

each new car program used the advantages tested laser

applications and introduced several new laser applications

that developed into standards for the next car program.

In 2003 all car programs take advantage of laser technolo-

gy. Figure 1 shows this step-by-step development.Volkswagen operates at the moment more than 500

lasers. The 4000 Watt lamp pumped laser manufactured

by TRUMPF has proven to be the most beneficial laser sys-

tem for Volkswagen and therefore the standard system.

The main reasons for VW's choice of lasers are short

welding cycle times, almost no wear items which equals

minimal maintenance, a reduction in component flange

width which equates to savings in weight and single sided

application that provides for new design options.

The above mentioned reasons leaded to the Golf V that

will be described in more detail in the following paragraph.

3e The production of the Golf V

The Golf V is based on the Volkswagen A5 platform first

introduced with the Audi A3 and the Volkswagen Touran.

The Golf .is the most important product for the Volkswagen

Group. With the introduction of the Golf V, the produc-

tion philosophy as well as the joining technology has been

changed dramatically (Figure 2).

The Golf V has been started up with intensive laser welding

applications in three plants at the same time. Wolfsburg/

Germany, Mosel/Germany and Brussel/Belgium. A total

of 250 4000W lasers including 3 new bodyshops had to be

installed, the plants prepared, people trained and the run-off

performed. The number of 250 4000W lasers are more

* Received 2004,9.1** Volks Wagen AG

溶接学 会誌 第73巻(2004)第8号 15

548

Fig. 1 History of laser applications at Volkswagen

Fig. 2 Comparison of the joining between Golf IV and Golf V.

Fig. 3 Development of the roof joint

than twice of the world production of 4000W lasers of the

year 2001. All these lasers require an total electrical ser-vice of 40MW, produce a total of 200km of laser welds per

day or 3000 cars per day. Laser processing is the dominat-

ed joining technology and used from the platform, side

frames, framing, respot-lines and doors as well. The laser

technology allowed us to decrease the required floor space

for the side panel assembly by 50% compared to the tradi-

tional resistant spot welding technology.

The following paragraph will describe 3 representative

laser applications of the Golf V.

4. Example 1: Laser brazed roof joint

The roof joints are traditional produced by resistant spot

welding with a roof ditch of 20mm. A sealer has to be

applied after the weld as well as a plastic cover for design

reasons. Switching to lasers, Volkswagen decided in the

beginning to move to an edge laser weld with the intention

to reduce the roof ditch to 10mm an to eliminate the sealer

operation. The full benefit of laser technology has been

reached while going one step further to laser brazing on

the class A surface. Laser brazing made it possible to

eliminate the sealer operation, the roof ditch cover and to

give the design engineers an invisible joint. Figure 3 illus-trates the development of the roof joint at Volkswagen.

Parallel to the evolution of the roof joint, the laser tools

have been developed/enhanced. In the beginning the

welds have been performed with the help of additional sys-

tems (optical seam tracker, X-Y axis, process monitoring

systems). The development of the adaptive brazing optic

eliminated all the additional systems that were more or less

difficult to handle. The adaptive optic keeps the focus of

the laser beam and filler wire automatic in the joint. This

had a positive impact in cost reduction of the early systems

(less components, low accuracy robot possible, easy to han-

dle and maintain).

Summarizing the advantages of using laser brazing are

the following:

First of all, a continuous laser brazed joint eliminates the

additional sealer process. Second, a laser brazed joint

with an additional cosmetic operation can get used on class

A surfaces. Third, laser brazing offers a factor 2 increased

gap bridging capability compared to laser welding with filler wire.

“Á•W The Latest Laser Applied Technology of the Auto Industry in Europe on the Example of the Body in White

Annlir.atinns of the Ynikswaven Golf V LOEFFLER16

549

5. Example 2: Laser welding

The lasers are used for welding zinc coated components

in all areas of the assembly process, starting with sub-

assemblies, platform, side frames, doors, framing station

and respot station. Most of the laser welds are performed

as overlap welds, some as edge welds. The flanch width

for spot welds of 14mm have been reduced to 8mm, which

is one reason for the achieved weight reduction. The

overlap weld joints are either two or three layer designs

with a package thickness between 1,6mm and 4mm. A

variety of materials are welded together, from regular auto-

motive steels all the way to Ultra-high-strength steels (hot-

formed materials).

The known problem of welding zinc coated materials are

taken care off by using appropriate clamping (material

thickness + necessary gap) or dimples produced during the

stamping process or through special clamping devices

mounted on the laser welding optic.

The laser process (power, speed, focus position) is devel-

oped keeping a large process window in mind. The laser

welding process has to be as robust as possible for the real

world application.

The most sophisticated workstation in the body shop is

the fully laser based framing station called Laser-Framing-

Station (Figure 4). This system has been developed by

Volkswagen Tool & Die in Wolfsburg. The system takes

the tagged body, fixtures all components to geometric posi-

tion and weld 200 geometric joints beside laser brazing the

roof joint. Volkswagen has a very positive experience

using this system, since all geometrically important joints

are performed in one fixturing station.

The system is extremely compact and has a reduced

floor space requirement of 40% compared to the convention-

Fig. 4 Laser Framing Station.

al manufacturing method. The system is designed in a

modular way to meet any production rate up to 60 jobs an

hour. One station applies up to 14 lasers that weld simul-

taneously. A production rate of 120 jobs an hour can get

met by simply adding the hardware for a second framing

station while using the laser from the first station in a syn-

chronized pattern. The time for shuttling the parts in/out

and clamping the parts are the time where the lasers can

get used in the second station. One key to the economical success is the intelligent use of the laser power of each sin-

gle resonator. In order to use the lasers across worksta-tions an intelligent Laser-Net-Work is essential. Volks-

wagen takes advantage of the TRUMPF Laser-Net-Work

The respot lines are designed without any product specif-

ic clamping. All the clamping is integrated in the roboti-

cally guided laser welding head. The reason is to offer a

solution for the trend to increase flexibility in auto body

assembly by allowing mixed production lines, flexible pro-

duction to meet customer demand and quick/low cost

changeover to new product lines. The changeover from

the Golf V to the Golf VI in a few years will show if we have

met the goal.

6 Example 3: Laser cutting of option holes

In the European market, cars are build on customer

orders. The customers like to get a more and more cus-

tomized car with a shorter delivery time. The Golf V is

being build in 89 variations taking the different body stills

and engine/drive train components into account. With all

interior/color options Volkswagen offers more than 16,000

different configurations for the Golf V. The challenge is to

reduce the number of parts and the complexity in logistics

with the goal to react faster to the new customer require-

ments.

The ideal situation to justify laser cutting technology.

Within the Golf V production line, the right-hand-drive ver-

sion, GPS antenna and other rare chosen options are cut

with a 1kW Nd:YAG system, 2 industrial robots with autofo-

cus cutting head (compare Figure 5).

Fig 5 The laser cutting cell.

溶接学 会誌 第73巻(2004)第8号 17

550

Instead of placing the cell in the body shop, the cell is

installed in the paint shop and laser cutting is performed on

the already painted body. This opens up the possibility to

increase the batch size per color and additional to move the

freeze point (last possibility date to react on a specific cus-

tomer request) closer to the delivery date.

Laser cutting is underrepresented in the present produc-

tion lines. Laser cutting offers further potentials especially

since the product life time will decrease and the number of

variations/options will increase. The cost justification for

cutting dies will get more and more difficult and laser cut-

ting technology might be the solution.

7. Conclusion

The goals of Volkswagen for the "laser based body shop"

have been reached.

Quality of the product

Uptime of the production line

Increased productivity

Flexibility of the production line

Reduction in floor space

The laser technology has proven itself as being a very

reliable technology for high volume production lines. The

challenge to integrate 150 lamp pumped 4kW Lasers

(HL4006D) into one single production line shows the relia-bility of the laser related components.

Qualification programs are necessary in all areas of the development and production process in the company in

order to reach the possible quality and economical benefits.

This includes design engineers and their partners, planning

engineers, the machine tool suppliers, laser component

manufactures and all the way to the plant /maintenance

/operator level.

Volkswagen operates more than 500 lasers on a global

base, all over Europe, in South America, Africa and Asia.

8. Outlook

The commitment to lasers by Volkswagen has pushed

the development of all aspects of laser technology. From

new laser resonators (Disk and Fiber) to production proven

laser processing heads for almost any laser application.

VW is looking for laser resonators with an efficiency of 20%,

a required uptime of 99.8%, a smaller footprint , unlimited fiber length for process flexibility, optimized laser usage

and improved beam quality to enhance productivity at

lower laser cost. And most important are methods to fur-

ther increase the process stability to weld zinc coated

steels. The goal is to reduce the requirements in preci-

sion clamping as well as reduce the required part accuracy

for laser joints. Both will further increase the usage of

lasers in the automotive industry.

The future designs for lightweight cars may call for more

use of advanced material like carbon composites, space

frame specific materials and plastic panels. This will call

for the most efficient joining method in terms of process

stability and economy. Laser technology might be the

choice

“Á•W The Latest Laser Applied Technology of the Auto Industry in Europe on the Example of the Body in White

Applications of the Volkswagen Golf V LOEFFLER18