thin stamped items. Some

components and subsystems of the dual

clutch, such as the main hub, are an assembly made of up to six items concentrically welded together (for each hub a weld seam of 2m cumulative length by 3mm deep is placed on both sides). In spite of a dimension of about 200mm, the final assembly must comply with a very tight run-out tolerance after the welding process.

A fully automated laser welding line, which includes complementary operations such as brushing to remove residual welding spatters, geometric control and traceability marking, delivers up to 300,000 DCT full units per year. This represents an accumulated length of about 800km of weld carried out using the sheer force of light. TTi

66 Case study: Fives

Transmission Technology International | September 2013

While the dual-clutch transmission is proving pivotal for fuel economy, laser welding could be an ideal assembly method the further supports the production of some components

a section view of a dual-clutch transmission hub

Laser welding for DCT componentsn The number of dual-clutch transmissions in the market is expected to more than double over the next five years to reach approximately nine million units by 2017.

To support this increase in capacity, Fives, the 200-year-old industrial engineering group, has concentrated its experience of more than 25 years in the design and supply of laser welding systems for powertrain components such as manual and automatic transmissions, camshafts, drive shafts and CV joints. Now Fives is marketing automatic lines dedicated to the production of hubs and disk carriers of DCT units, using high-power lasers.

Quality innovationsInnovations in the field of transmissions involve new materials and altered geometries of powertrain components. To deal with these new requirements, the advantages of laser welding for mass production are indisputable: precise concentration of energy emitted by the beam on the welding point ensures a high energy density, while minimizing possible warping and modification of the material properties. At the same time, an unrivaled depth/width ratio of the weld seam ensures an excellent mechanical assembly. Laser welding also enables a high operating speed and unmatched repeatability.

The quality of a laser welding result is conditioned by finding the right balance between various parameters such as welding mode (conduction mode or keyhole mode); power density of the laser on the material; focal length and tilt of the beam; number of weld passes and their speed; composition of the shielding gas; the flow rate and injection mode of the shielding gas; and a proper positioning of the assembly of components to be welded.

Geometry challengesIn the case of DCTs, the main challenge lies in ensuring a proper overall geometry of the final assembly performed by laser welding, while the construction is made mostly of

an automated laser welding line delivers over 300,000 dCt units per year. Fives offers the market automatic lines dedicated to the production of hubs and disk carriers of dCts