LaserHybrid Welding Drives VW Improvements — Volkswagen Phaeton

22 мая 2015 | Author: | Комментарии к записи LaserHybrid Welding Drives VW Improvements — Volkswagen Phaeton отключены
Volkswagen Phaeton

Laser-Hybrid Welding Drives VW

Laser-Hybrid Welding Drives VW

A hybrid process that a laser beam with gas arc welding produces benefits could not achieve with process alone

Laser welding and arc welding both long been used in production and permit a wide of applications. Both processes their specific areas of as described by the physical processes of transport and by the obtained energy Energy is transmitted from the to the arc by means of high-energy infrared radiation using a fiber-optic The arc transmits the heat needed for by a high electric current to the workpiece via an arc column. Laser leads to a very narrow zone with a large of welding depth to joint (deep-weld effect). The ability of the welding process to bridge openings is low due to its small focus but, on the other hand, welding speeds can be obtained. The arc process has a much lower density, but causes a bigger spot on the surface and is characterized by a processing speed. By merging processes, useful synergies can be and, ultimately, it is possible to both quality advantages and engineering benefits, as well as cost efficiency. This process offers interesting and attractive applications in the automobile due to higher permitted tolerances on the because of higher joining and good mechanical/technological parameters. — A schematic representation of welding. This article an application at Volkswagen AG, Wolfsburg, where the doors of the Phaeton are welded with a laser-hybrid

Development of Laser-Hybrid Welding

The for combining laser light and a arc into an amalgamated welding has been known since the but for a long time thereafter, no research and development was undertaken. however, researchers have turned their attention to topic and attempted to unite the of the arc with those of the laser in a welding process. In the early the suitability of lasers for industrial use had to be nowadays lasers are standard in many manufacturing enterprises.

The of laser beam welding another welding process is a welding process, meaning a beam and an arc act simultaneously in one welding and influence and support each Fig.2 — Volkswagen’s model. The Laser

Laser welding not only high laser power but a high-quality beam to obtain the deep-weld effect. The resulting beam quality can be exploited to obtain a smaller focus or a larger focal distance.

For the currently underway at Volkswagen, a solid-state laser with a beam power of 4 kW is used. The light is transmitted via a water-cooled, glass fiber. The laser is projected onto the workpiece by a module with a focal of 200/220 mm. Fig.3 — of the joining techniques used on the Phaeton’s front door. process: 7 joints, 380- mm length; laser beam 11 joints, 1030-mm welded laser-hybrid process: 48 joints, welded length. Total length equals 4980 mm. The Process

For welding metallic the Nd:YAG laser beam is to obtain intensities of more 106 W/cm2. When the laser hits the surface of the material, the is heated up to vaporization temperature and a cavity is formed in the weld due to the escaping metal vapor. The feature of the weld joint is its depth-to-width ratio. The energy density of the freely burning arc is more than 104 W/cm2. 1 illustrates the basic principle of welding. The laser beam here transmits heat to the metal in the top part of the joint, in to the heat from the arc. a sequential configuration where two weld processes act in succession, welding may be viewed as a combination of weld processes acting in the same process zone. on the kind of arc or laser process and depending on the process parameters, the will influence each to a different extent and in different (Refs. 1, 2). Fig. 4 — butt joint for the Volkswagen D1 (currently called the Phaeton). welding parameters for aluminum materials: welding speed, 4.2 wire feed rate, 6.5 and laser power, 2.9 kW. Thanks to the of the laser and the arc, there is an increase in both weld depth and welding speed (as to each single process). The vapor escaping from the cavity acts upon the arc Absorption of the Nd:YAG laser in the processing plasma remains Depending on the ratio of the two power the character of the overall process may be determined either by the laser or the arc 3).

The temperature of the workpiece surface influences absorption of the laser Before the laser welding can start, the initial reflectance be overcome, especially on aluminum This can be achieved by starting with a special start After vaporization temperature has reached, the vapor cavity is and nearly all radiation energy can be put the workpiece. The energy required for is determined by the temperature-dependent absorption and the of energy lost by conduction the rest of the workpiece. In laser-hybrid vaporization takes place not from the surface of the workpiece but from the welding wire, so metal vapor is available, in turn facilitates the input of radiation and prevents process (Refs. 4-9).

Using the Process at Volkswagen

strategy is to have the highest of laser weldments in the automotive Figure 2 shows the Phaeton, called the Concept D1. In this car all doors are laser-hybrid welded. The requirements included a high of stiffness in the door structure. the laser-hybrid process, big, aluminum cast materials have been necessary. The tolerances had to be very small to a perfect fit to the car body, resulting in low levels from the wind driving. To achieve a door that degree of stiffness, a combination of sheet, cast, and materials was necessary. In order to a low weight, aluminum was the preferred and material because of its low density.

The door shown in Fig. 3 of 7 gas metal arc, 11 laser, and 48 weldments. The total length of on these doors is 4980 mm.

4 shows a laser-hybrid welded of a two aluminum cast material. The wire was AlSi12 with a of 1.6 mm. The shielding gas was argon. With laser power, higher speed is possible. Combining the beam with the arc results in a weld pool compared to the beam weld process and welding of components with root openings becomes The range of the welding speed is 1.2 to 4.8 but the process is optimized at 4.2 m/min.

In the industry, there are many of overlap welding without preparation. At the moment, the state-of-the-art for this welding job is laser welding with a cold wire, due to hot cracking of the AA 6xxx When the joint is welded a welding wire, much of the energy will be lost in that welding wire.

Comparing Laser-Hybrid with Processes

Figure 5 represents the between laser-hybrid and laser on an overlap joint with a speed of 2.4 m/min. In the case of welding, there is no possibility of up the weld and undercut is produced. is also only a little into the base material. The bead width is very and, therefore, a low tensile is expected. In the case of laser-hybrid additional material is transported the weld pool. The undercut is with wire from the gas arc welding (GMAW) process and a of laser energy is now saved. saved laser energy can be to increase the penetration into the material and the weld bead is larger than the material which is required for optimum properties. Fig. 5 — between laser hybrid and beam welding without metal. In the case of laser with welding wire 6), it is necessary to use a pressure wheel to get the tolerances. But there are limits accessibility because of the higher of the welding head. Typical of this process are a welding of 2.8 m/min, laser power of W, and wire feed rate of 6.6 With the laser-hybrid process, it is possible to weld other geometries, especially fillet on lap and butt joints. Fig. 6 Laser cold wire at Volkswagen. Figure 7 shows the head, which has small dimensions to ensure good to the components to be welded, a requirement needed for the automotive industry. It is to permit both a suitable connection to the robot head and of process variables such as distance and torch standoff in all Cartesian coordinates. The accuracy of is 0.1 mm in all directions. The spattering that during the welding process to increased soiling of the protective The quartz glass is coated on sides with an antireflective and is intended to protect the laser system from damage. on the degree of soiling, the spatter on the glass can cause the laser actually impacting the workpiece to by as much as 90%. Heavier generally leads to the destruction of the glass, as such a large of the radiant energy is then by the glass itself, causing stresses in the glass. To avoid a glass or a reduction of laser on the workpiece, it is possible to integrate glass monitoring equipment. The head has a changeable water-cooled gas and torch and a current load of up to 250 A at a cycle of 100%.

The welding head can be applied for welding with and without wire, laser-hybrid welding, gas arc welding, and laser hot-wire (especially for zinc-coated materials). In the of laser hot-wire brazing, the is preheated with the same source that can be used for welding. There is only a in the software, not in the hardware configuration.

of Laser- Hybrid Welding

The of the arc and laser beam results in the advantages of laser-hybrid welding laser welding:

Higher stability

Higher bridgeability


Lower capital costs because of savings in energy

Greater ductility.

The of laser-hybrid welding over are the following:

Higher welding

Deeper penetration at higher speeds

Lower thermal

Higher tensile strength

weld joints.

The arc welding is characterized by a low-cost energy good root opening and the facility for influencing the structure by filler metals. The laser process, on the other hand, large welding depth, welding speed, low thermal and narrow weld joints. The beam produces a deep-weld in metallic materials over a beam density, which components with greater thickness to be welded- providing the power is sufficiently high. welding thus allows welding speeds, process due to the interaction between the arc and the laser increased thermal efficiency, and workpiece tolerances. As the weld is smaller than in the GMAW there is less thermal and a smaller heat-affected zone. results in lesser weldment which reduces the amount of postweld straightening work. there are two separate weld the subsequent thermal input the arc means the laser beam area, especially in the case of is given a postweld tempering spreading the hardness values evenly across the joint. 8 sums up the synergies of the combined hybrid) process. Fig.7 The laser-hybrid welding head. now to the economic advantages of hybrid over laser welding, the statements can be made: The weld consists partly of a laser and partly of a GMA weld. The hybrid makes it possible to reduce the of the laser beam, thereby reducing energy consumption of the source as the laser beam has an efficiency of only 3%. In other a reduction of 1 kW in the laser beam impacting upon the workpiece to a reduction of approximately 35 kVA in the power from the electricity mains.

A laser beam apparatus approximately $120,000 per kilowatt of beam power. When of the hybrid process makes it to use a 3-kW laser instead of one 4 kW of beam power, investments of are saved. However, costs of $65,000 will be needed for the MSG equipment and welding head. Due to the welding speed, both time and welding costs can be Fig.8 — The synergies by combining laser beam and arc With the laser-hybrid welding it is possible to weld materials of steel, and stainless steel 1 to 4 mm thick. If the thickness is higher, penetration is only possible in the of steel or stainless steel up to 5 mm. For zinc-coated materials, it is preferable to use the hot-wire brazing process.

applications where the laser- welding process is suitable are trains, vessels, axles, and car


Laser-hybrid welding is a new that offers synergies for fields of application in the automotive especially where it is not possible or viable to achieve the component required for laser beam The wider range of applications and the capability of the combined process to enhanced competitiveness in terms of investments, shorter fabrication lower manufacturing costs, and productivity.

The laser-hybrid process offers a new approach to the welding of However, a stable process has possible relatively recently of the higher available output of solid-state lasers. Many have examined the fundamentals of and arc hybrid welding processes. By welding process, the combination of beam welding and the arc welding is understood, with only one process zone (plasma and Research has shown by combining the two synergies can be achieved and the drawbacks of separate process can be compensated resulting in enhanced welding weldability, and reliability for many materials and constructions. In particular, has been demonstrated for aluminum at Volkswagen on the Phaeton model. By the current process parameters, it is to selectively influence weld such as geometry and structural The arc welding process increases the by adding filler metal; it determines weld joint and reduces the amount of workpiece needed. Moreover, the interactions the processes lead to a substantial in efficiency. This combination also requires considerably investment costs compared to beam welding. New joint are possible, especially fillet or joints, and it is not necessary to use a pressure on the welding head, resulting in accessibility.


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2. Cui, H. 1991. Study of between arc and focused laser and applicability of combined laser-arc Thesis. Technical University

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4. et al. 1978. Arc-augmented laser Paper No. 17 4th Int. Conf. on in Welding Processes, pp. 257-265.

5. 1996. Laser Material Springer Verlag.

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7. Beyer, E. 1997. Welding Lasers: Basis. Springer.

8. F. Weick, J. M. Fitz, R. and Kern, M. Applications of twin focus Laser Days in Stuttgart, pp.

9. Helten, S. 1999. Qualification and of arc suported laser beam process in the production process of body lightweight construction. Germany: Diplomarbeit Audi, (ISF). T. GRAF is with Wolfsburg, Germany. H. STAUFER is Fronius International GmbH, Austria. Fronius USA can be reached at 220-4414 or

Based on a presented at the Annual Assembly of the Institute of Welding on June 27, in Copenhagen, Denmark.


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