Hairpin winding technology is essential in electric drives for traction applications. This process involves inserting copper bar segments coated with an insulating layer, cut, and bent to shape. Laser welding is used to connect the hairpins at the final production stage, which depends heavily on enamel stripping quality. Residual enamel can cause weld defects, while over-stripping leads to conductivity damages. Hairpin stripping can be achieved via lasers, offering flexibility in size and geometry, or cutting tools, which involve simpler machinery. Each method differs in material removal, resource use, waste generation, and defect potential. However, the benefits and limitations of digital laser technology over the mechanical milling process require further evaluation and objective measures. This study systematically compares laser removal and milling for hairpin stripping, analyzing productivity, defect types, joint strength, and electrical conductivity. It benchmarks the two methods based on resource efficiency and waste generation.

A novel hybrid welding method combines laser and MIG welding for enhanced performance. A narrow gap is created between the workpieces, and a laser head with an oscillating beam is positioned alongside a MIG torch. The laser preheats the workpiece edges and partially heats up the melt pool formed by the MIG process. The melt fills the entire gap. This dual role of the laser improves weldability, surface wettability, and melt flow characteristics. The metallurgy of the weld can be tuned using the composition of the filler wire. Therefore, this method is also suitable for dissimilar welds with appropriate filler wire. Consequently, the method yields superior weld quality across the entire cross-section with improved uniformity in chemical composition, geometry, and microstructure. The method is currently under investigation for various steel grades, including structural and austenitic stainless steels, and their combinations.

In recent years, special steels have attracted considerable interest due to their high strength, wear resistance and weight reduction potential. However, the industrial application of high carbon steels remains limited because of their challenging weldability. This study investigates the use of laser preheating before welding and laser heat treatment after welding to enhance the mechanical properties of high carbon steels. Unlike traditional methods such as furnace or induction heating, a novel approach utilizing an oscillating laser welding head was successfully implemented, allowing localized heat treatment application. The process was optimized for a specific weld length by adjusting the number of heating cycles and laser power. Mechanical tests revealed significant improvements in strength and hardness for materials that are otherwise completely unsuitable for welding without heat treatment. The results show the potential to open up wider industrial applications for the welded use of high carbon steels.

With new opportunities for processing, recycling and repair, thermoplastic carbon fiber-reinforced polymers (TCFRPs) offer promising approaches to tackle the economical and sustainability challenges of tomorrow’s aviation industry. The authors enabled the manufacturing of the longitudinal butt joint of the world’s largest thermoplastic aircraft structure: The Multifunctional Fuselage Demonstrator (MFFD), created in the European Union’s Clean Sky 2 project. Using a CO2 laser source, fully-consolidated multidirectionally reinforced TCFRP laminates with 6 plies were welded onto the longitudinal butt joint in a one-shot process. During welding, multiple parameters were adjusted constantly to achieve a joint with high homogeneity, such as laser power, beam shaping and feed rate. Mechanical testing (ILSS) has shown that the produced joints offer similar strengths as reference samples from conventional heat press co-consolidation, without any post-processing necessary after the layup of the laminates.

Hybrid polymer-metal parts gain popularity in industrial applications, for example for lightweight structures or parts with combined material properties. In order to join metals and plastics laser direct joining is often the process of choice, leading to strong and reliable joints without adhesives, primers or mechanical fasteners and can therefore also be used in medical technology. Laser direct joining of metals and polymers is based on two processes. To achieve a good mechanical bond between the parts, the surface of the metal part is structured in a first step. In the second step, the polymer is heated in order to allow the melt to flow into the prepared metal structures. When using highly filled, fiber-reinforced high-performance polymers, which are required in many demanding applications, melt flow into these structures can be hindered. Process optimizations are presented to avoid air enclosures in the structures, surface defects or inhomogeneous bond properties.

Multi-materials which can save weight are important materials to realize carbon neutrality. Our innovative laser direct joining method is effective for joining different materials such as difficult-to-join composite materials and light metals. However, its joining mechanism and properties have not been clarified so far. Therefore, the objectives of this research are to clarify the joining mechanism of laser direct joining of difficult-to-join composite materials and light metals by integrating cutting-edge observation and analysis with materials informatics (MI) and computational science, and to control the dominant factors of joining by optimization of surface modification, etc. to realize ultimate joining strength, superior reliability and environmental durability that can be used in space and deep sea.