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SCHWEISSEN & SCHNEIDEN
Battery trays

Welding expertise with battery trays

Just a few years ago, electric cars received little public attention on grounds of their lack of performance and range. Their owners were often mocked for being “eco freaks”.
Then Tesla arrived on the scene, ushering in a new era, assisted by the climate crisis. The now rapid transition toward electromobility poses significant challenges for traditional automotive engineering. Alongside cross-brand e-platforms, it requires modern production concepts. Battery trays, which are often installed in the vehicle underbody, must meet high quality standards in terms of crash behavior and tightness.
The industry is, therefore, relying on completely new manufacturing processes, including in the field of welding technology.

Battery trays protect the battery cells installed in them from external influences. The welding requirements are high:

To protect the battery packs from corrosion, they must be absolutely leak-proof and resistant to stress in the event of a collision. The temperature of the lithium-ion cells has a significant influence on the efficiency of the batteries. For this reason, the tray housings are surrounded by heat sinks. Due to the design, more and more large-area components and components of different strengths are used. These must be welded almost flat and without distortion in a constant quality that can be reproduced at any time. This makes welding more than just challenging. Extruding press and cast profiles are manufactured from aluminum alloys with wall thicknesses of between 2 and 25 millimeters.

Laser Hybrid cell

Welding Process for Prototype Construction

Only a few welding processes are suitable for joining the material in a stable, efficient, and moisture-tight manner. These include the highly developed process variants of gas metal arc welding (GMAW), some of which work with and some without reversing wire feed movements: CMT (Cold Metal Transfer), LSC (Low Spatter Control), and PMC (Pulse Multi Control).
The LaserHybrid process, on the other hand, offers particular advantages for longitudinal weld connections:

This process combines a laser beam with a MIG welding process in a common process zone. The highly bundled light beam, which is aimed at the weld seam, penetrates deep into the parent material and is characterized by its high energy density. It is followed by a MIG process. This is used to fill the seam and creates an excellent flank connection. The additional heat introduced gives the material time to outgas, thus reducing the aluminum’s proneness to porosity.

Wolfgang Scherleitner, Head of our Prototype Center, knows the advantages of LaserHybrid:

LaserHybrid video

» The high energy density and arc stabilized by the laser enable high welding speeds and short cycle times. At the same time, the low energy per unit length minimizes component distortion. «

Scherleitner Wolfgang - Fronius Perfect Welding
Wolfgang Scherleitner, Head of Prototype Center
Battery trays simulation

Before battery trays go into series production, feasibility studies are carried out and prototypes are manufactured. Determining the most suitable welding process requires expertise in manufacturing technology and metallurgy as well as specialized welding knowledge and large-scale, cost-intensive equipment:

  • Robotic welding cells
  • clamping devices
  • online and offline programming software
  • sensor technology
  • welding data management
  • component-measuring cells
  • and, ideally, a welding laboratory.

But profound welding experts are thin on the ground these days and the capital investment required for software and welding systems is extensive. By commissioning specialized companies like Fronius with prototype production, automotive manufacturers and suppliers not only solve their skilled labor problem. They also tie up less capital by saving on development and production costs.

Simulation video

Fronius Prototype Center: Considerable Added Value

Together with our clients, primarily from the automotive industry, we seek out the best solution for joining critical components in the Fronius Prototype Center. As part of our services, we provide our customers with informed recommendations relating to welding processes, timings, and the quality and layout of welding systems. All of these details can be incorporated into the planning of future prototypes and series production, which helps our customers with their costing.

In addition to technical consulting, feasibility studies, prototype production,mechanical processing and quality inspections, we are also able to produce smaller quantities for the test phase or pre-production series on request. If required, we equip our customers’ series production with robotic welding cells. As a solution provider, we offer complete solutions from a single source, both for prototype construction and series production.

CMT cell

Premium Welding Technology

Covering around 1000 square meters, our Prototype Center provides sophisticated welding and measuring technology. Accessible only with special authorization, it guarantees absolute discretion. Our systems weld components with a diameter of up to 3.5 meters and a maximum weight of 2.5 tons. Our prototype robotic welding cells are equipped with CMT technology. The heat-reduced welding process is suitable for almost any parent material, especially light-gage sheet metal, as it drastically reduces spattering and distortion. The highly flexible TPS/i welding platform used here makes it possible to use additional GMAW welding processes, as required. In the course of pre-processing, we use our Acerios surface cleaning system, which cleans the component joints in an energy-efficient manner, for welding using hot plasma technology.

Some of our prototype robotic welding cells feature a powerful LaserHybrid system. Due to the advantages of the LaserHybrid process described above, we can reduce both the energy per unit length and component distortion by up to 50 percent compared to conventional GMAW welding.

Vitronic laser weld seam inspection

Sensor Technology and Data Documentation

All of our prototype robotic welding cells have sophisticated robot assistance and control systems:

  • We use laser cameras to track the weld seams. Seam position, edge misalignment at the joint and orientation of the tool relative to the component surface are detected and passed on to the robot controller. This ensures precise seam tracking.
  • SeamTracking reliably detects the component edge by means of pendulum movements of the welding torch, for both butt and fillet welds. In case of deviations, the robot corrects the pre-programmed welding process and continues welding at the correct position.
  • WireSense turns the wire electrode into a sensor. The system reliably detects both the edge height and the position of the components. Manufacturing inaccuracies in sheet metal are detected and taken into account during welding. This leads to excellent welding results that reduce rework and component rejects to a minimum.
  • ArcView 2, a high-performance camera, provides our welding technicians with a direct view of the arc, droplet detachment, and the weld seam being formed.
  • WeldCube, our welding data management system, stores all data from the welding process. This enables us to document, evaluate and track a wide range of information, even in the case of manual welding processes: Job number, amperage, voltage, wirefeeder, arc and dynamic correction as well as welding speed and time. To facilitate analyses, the data are graphically processed by the software and also displayed on a monitor.
Weld inspection video
Measurement

During the welding tests, the individual components are measured before and after welding in a robot-controlled measuring cell, whereby any component distortion is detected with millimeter precision. If necessary, welding and measuring are repeated until the component is within the distortion tolerances specified by the customer and the ideal welding parameters, welding sequences and clamping points have been established.

The prototypes are then subjected to metallurgical testing, the results of which are incorporated into the welding tests. This allows us to keep the number of test components as low as possible. Only those prototypes that meet all customer requirements down to the last detail are released.

In summary, our customers not only receive data which are valid for series production, but also robot systems for producing battery trays if required – all from a single source!