Workpiece transport system for fully automated battery testing

The ACOPOStrak transport system from B&R is used in an X-ray inspection system for round battery cells. With maximum flexibility, simple parallel operation across multiple lines and a highly controllable production flow, this system combines cost-effective operation with impressive testing performance.

Even though battery production only accounts for a small part of overall electric vehicle production, its economic and strategic importance is immense. Acceptance and vehicle market penetration depend on the quality and price of mobile energy storage systems.

Around a third of the cost of an electric vehicle is accounted for by the battery. The vehicle's range, which depends on the battery capacity, is still the most important feature for most buyers. The quality and reliability of the batteries have a direct impact on safety and driving characteristics. 100% inspection of batteries during production is therefore essential. X-ray inspection has established itself as a common method for inline inspection of batteries.

Exacom GmbH from Hanover specializes in inspecting prismatic and round battery cells.

The company supplied the iXcell system for X-ray inspection of round cells to the gigafactory of a well-known electric vehicle manufacturer. To achieve the required inspection rate of around 175 cells per minute, an ACOPOStrak transport system from B&R Industrial Automation is used in the system.

Hagen Berger, Managing Director of Exacom, explains: "Basically, there are two decisive factors for X-ray inspection: We have to master image acquisition, which means we use a process that captures a high-quality image with maximum reliability in the shortest possible time, and we also need a suitable transport system."

ACOPOStrak from B&R is used throughout the entire battery production facility at the electric car manufacturer's gigafactory. X-ray inspection with iXcell is fully integrated into the production line and inspects each battery cell during critical production steps and ejects it immediately if testing fails. This means that defective cells are not dragged through the entire process only to be ejected at the end of the line, which would result in losses in yield, raw materials and energy.

The inline integration of the iXcell stations also means that the X-ray system must keep pace with the production flow and not become a bottleneck, however. Between 150 and 175 battery cells per minute leave the automatic winding machines in battery cell production and each one has to be put through its paces in a time window of around 340 milliseconds. Hagen Berger: "To meet this requirement, we use the possibilities of the ACOPOStrak transport system. During inspection, the individual shuttle with the battery cell must stand absolutely still. Each subsequent vibration after the stop extends the test cycle. That's why the specialists at B&R configured transport system controller so the cell in the X-ray station is slowed down with the greatest possible deceleration and a predefined motion profile and the vibration is suppressed by the maximum amount.

Above all, however, Managing Director Berger sees the almost unlimited flexibility of the ACOPOStrak system layout as a unique selling point: "In contrast to a conventional monorail system, B&R offers a high degree of flexibility in the design of the overall system, especially when linking different process steps. The electronic diverter allows us to easily eject defective cells, set up parallel product flows or, if necessary, direct the process to a specific station without having to interrupt production, for example when servicing is required. As far as I know, no other manufacturer can do this in this form."

Berger explains what this means in practice using an example: "The design of the ACOPOStrak makes it possible to pick up the round cells from four winders in the gigafactory and feed them through two X-ray systems. Thanks to path flexibility, we can even move to a turning station if necessary allowing a cell with a test specimen that is rotated by 90 degrees to be run through a system a second time."

When designing the X-ray system, which was specially developed for this battery manufacturer, Exacom benefited from an ACOPOStrak digital twin as well as engineering support from the B&R branch in Hanover and the headquarters in Eggelsberg, Austria. "We had to design the X-ray system within a time frame of six months and integrate it into battery production. This was a challenge and we really appreciated the support from B&R," explains Berger.

Within a very short time, the system design and the positions at which the test specimens enter and exit the X-ray system were tested and defined with the help of digital simulation. This also involved finding a suitable line layout to optimize battery test specimen handling including buffering, discharge and material flow. Berger sums up with satisfaction: "This accelerated development, resulted in less trial and error and allowed us to determine early on in the development process how the cells and carriers should be placed."

For Exacom, a welcome side effect of simulation with a digital twin was the ability to transfer the source code from the simulation models directly into the hardware. "All in all, great teamwork," concludes Managing Director Berger.