Flexible Remote Laser Welding – E-Mobility

In remote laser welding of electrical contacts, battery cells and bipolar plates of fuel cells, there are different challenges for the laser welding technology. These are as follows:

The challenges in welding electrical contacts are, on the one hand, the welding of different materials such as copper and aluminum, and on the other hand, their planar connection in the smallest possible space and maximum connection cross-section for optimal current transmission. This means: A large number of connections must be made whose joint surfaces have the greatest possible reproducibility. Tolerances that occur inherently are normal in this case and have to be compensated for. For this purpose, it is important that the path of the laser beam – generated by a 2D scanner – can be adapted to the position and tolerance of the component. High-frequency oscillation also enables precise control of the seam geometry and welding depth. A supreme discipline is the welding of stator hairpins in electric motors, where absolutely no defects are permitted.

Tight connections are essential for the final sealing of battery cells and their integration into the battery modules – and this with very short cycle times. For welding battery cells, the laser beam must be positioned and guided precisely to the welding contour. If oscillation is superimposed on the welding movement for this purpose, it is possible to achieve better bridging of gaps and to compensate for tolerances in the component while maintaining the same welding depth.

The bipolar plate is a component with several functions. In the fuel cell, it has the task of guiding and separating the gas and serves as an electrical connection as well as for cooling. To produce a bipolar plate, two very thin stainless steel sheets are laser-welded in an overlap joint to form a tight plate. A high welding speed ensures that the energy input of the strongly focused laser beam can act on the sheets in such a way that the welding process generates secure joints with little distortion. Beam-shaping optical elements can be used to optimise the energy distribution. In this way, instabilities such as humping – which are welding seam irregularities – pore formation and seam ejections, which can arise from the demanding process parameters, are reduced.

When laser welding hairpins, the ScaVis camera is a must. For laser welding of other contacts, it is a valuable asset.

High-quality machine vision ensures high process quality, which must be 100 percent guaranteed, especially when welding hairpins. Blackbird's ScaVis camera ensures that each of the up to 400 pin pairs is welded absolutely error-free. Behind this is a reliable detection and localisation system of the wires, which defines the characteristic geometries of the component. Based on the camera images, the welding path is defined and parameterised offline. Before the laser welding process is started, the RobotSyncUnit (RSU) software compares the actual component contours with the pattern stored. As soon as a deviation outside the defined limits and thus an impermissible component position is detected, the system sends a warning to the machine control and prevents welding.

Of course, the welding data is documented on the PLC of the user and thus ensures the monitoring of the welding results.

Due to agile and partly outsourced procurement processes, a component may be purchased from different suppliers in automotive production. Since different manufacturing technologies are also used, component deviations in the delivery batches are literally pre-programmed. In order to be prepared for all contingencies, the software of the Blackbird technology package contains large amounts of image information about a possible design of the component. The simulation of the image recognition process enables the verification of the program-specific ScaVis camera settings for the new batch.

Should a component ever fall outside the specified limits, the system skips individual welds. This prevents defective welds, as this would irrevocably destroy a component. If a weld is skipped, the possibility for rework remains open. In such a case, the system operator can place the weld manually in the ScaVis program interface. If the process is time-critical, the higher-level controller can be given the command to skip welds in order to rework the component later. 

Anyone who wants a well thought-out, reliable and economical solution package for electromobility in automotive production is on the safe side with the holistic offer from ABICOR BINZEL and Blackbird. The highly developed and powerful technology of Blackbird can be used internationally in the automotive industry through the worldwide sales and service network of ABICOR BINZEL.

• Sophisticated technology package
• International network of experts
• Worldwide application and service support