VARTA Consumer Batteries is a leading brand manufacturer and is part of the American consumer products group Spectrum Brands. Within the corporation, it concentrates on the premium battery segment. The Dischinger factory specializes in manufacturing all types of batteries, from mono- to AAA microcells. All equipping, assembly and filling processes are developed in Dischingen in accordance with specifications from the US head office. The entire production process takes place in this plant, up to and including the printing and packaging of the final product. Approximately three million battery cells are sent to the shipping depot daily, first passing through rotary indexing machines, conveyor lines, test facilities and packaging machinery. Not all the batteries bear one of the two house brand names. Many partners who sell own-brand batteries are supplied with VARTA’s high-quality mignon cells. Otto Hessel, technical director of the plant: “We compete globally on quality and price. We’re not just competing with ‘real’ competitors, but also with other production sites in the group.” The pressure is enormous. VARTA thus seeks to ensure maximum system availability and optimal production processes at the lowest possible cost.
The first step in slow-motion technology
At the factory, production speed runs up to 600 units per minute. If an error occured while production was in progress, it would not have been possible to identify the causes clearly with the naked eye. Here, the slow-motion technology came into play. Modern high-speed cameras deliver clear results in uncovering unexplained error sources and collect technical measurement data. This makes it possible to optimize processes, improve product quality and reduce costs, even in high-speed rotary indexing machines.
Based on these considerations, management at the Dischingen factory decided to invest in a high-speed camera. They quickly chose the MotionBLITZ® Cube2 from Mikrotron for convincing reasons, as technical director, Otto Hessel stresses: “We opted for a Mikrotron MotionBLITZ® Cube2 because the demo recordings, which were done in less than 15 minutes, helped us to precisely identify the reasons for of one of our most important process problems.” The recording speed, image quality, and particularly the device’s extremely easy handling, met all the requirements for daily use in production and plant commissioning. In addition, the people at VARTA liked working with an experienced German manufacturer, thus using a short-distance strategy.
Precisely adjusting the injection process
According to Otto Hessel, the latest generation of batteries from VARTA performs significantly better than its competitors. The reason for this improved performance is a special electrolyte formula filled in the battery body. Highly accurate dosing is an crucial factor, but there are only a few hundredths of a second available for the filling process. In the past, this production step caused two problems:
- First, the plant was repeatedly and substantially contaminated. This increased maintenance costs and thus lowered plant availability, leading to reduced production figures. In addition, this contamination led to reductions in the quality of the batteries’ external constitution.
- Second, electrolyte-filling problems meant that the performance of the individual batteries fluctuated more than the specifications allowed, and morer than the formula would have allowed in theory.
“Even the first high-speed recordings allowed us to make huge steps forward,” explains Josef Graule, a production engineer who specializes in working with this camera. “After a few high-speed recordings we were able to choose the filling nozzles so that the filling process did not lead to annoying splashes.” VARTA could thus avoid the contamination of the plant and machinery with the aggressive electrolyte that might otherwise have happened. The process parameters could quickly be adjusted based on the slow-motion studies, allowing them to meet the high quality requirements within the very short cycle time.
Finding errors quickly with slow-motion studies
A missing electrolyte drop changes the battery characteristics, contaminating the production facility and increasing maintenance costs. The relevant process parameters could quickly be optimized with the help of slow-motion studies. In the picture, the drops are colored red.
Previously, in the time-consuming “trial-and-error“ process, staff had to wait until the finished product was ready for testing after each readjustment of the system. Today, the impact of control parameters can be seen directly in the running processes. This allows the production departments to evaluate both the facilities and the processes involved better than before.
A sophisticated analysis of labeling
The MotionBLITZ® Cube2 also facilitated significant successes in battery labeling. The labeling machine runs at a speed of 900 to 1,000 pieces per minute. Each label must precisely start on the rotating battery at a constant belt speed: Each slip during label transfer or any insufficient adhesion to the cell causes a problem for the next cell. If batteries are labeled incorrectly, this leads to unnecessary wastage and loss of material. A possible label jam must be rectified and leads to machine downtime, which can add up from one shift to another. The error analysis of this machine by means of high-speed recordings would not have been possible without the simultaneously high image resolution. In the lateral shots required here, the label is only visible as a very thin contour line. This new technology nevertheless allowed VARTA to thoroughly analyze this complex problem and find troubleshooting methods. Machine downtimes and other drawbacks were reduced considerably. This made it possible to optimize this production step.
Labeling machine in the Dischingen battery factory
The labeling machine runs at a clock rate of up to 1,000 units per minute. The error analysis of this machine by means of high-speed recordings with the MotionBLITZ® Cube2 would not have been possible without the simultaneously high image resolution.
High-speed imaging of the labeling machine
The MotionBLITZ® Cube2 had to be fitted to the side. From this perspective, the labels were only visible as a thin line. In the high-speed recording, they are marked with a red outline.
Precisely adjusting measuring devices
Another example is the setting up and adjustment of a continuous measurement control device. With the help of the MotionBLITZ® Cube2, VARTA could precisely calibrate a new laser measuring device for quality control. The slow-motion study showed the exact point at which the measurement of the battery body should be started and what production speed allowed the highest accuracy with the plant at full capacity. Here, a built-in camera function – the time stamp in each frame – was extremely beneficial. It enabled process adjustments in the millisecond range. Even small delays in production control were recognizable and so the processes could be adjusted to suit each other much more precisely. “The additional insertion of control signals in high-speed recordings provides further valuable information for process optimization, as we often have to coordinate multiple process steps within one machine,” explains Josef Graule.
The quick way to recoup investments
Investigating errors during running production had proved unsatisfactory because process speeds had to be slowed down tremendously. At these speeds, however, the machines usually ran problem-free because the errors only occurred at full capacity. The high-speed camera now makes it possible to detect where problems occur, even at maximum production speed. Graule says: “The MotionBLITZ® Cube2 now provides us with the information that will help us to reduce bottlenecks in the production flow even further.”
Within just one year, studies with the MotionBLITZ® Cube2 were conducted at more than 20 points in the production process for the battery cells. A whole series of optimizations were made based on the results. When purchasing the MotionBLITZ® Cube2, VARTA hoped that the system would pay for itself within a period of one year. With this in mind, the fact that they recouped their investment in less than a year has to be considered a great and unexpected success.
There is an additional benefit that is not captured in the financial calculation, but nevertheless has a positive effect: Instead of simply having to come to terms with recurrent and frustrating production problems, VARTA’s employees could now look forward to a solution. This made them feel again that their efforts were worth it. The result is a healthy interaction between man and machine, which in turn can lead to improved motivation and a higher quality production.
A strategy of sustainable process optimization
In Dischingen they still see great untapped potential in high-speed analysis. In the long term, VARTA sees preventive system optimization based on clear information using slow-motion recordings as a powerful way to boost productivity even more. This would be not only be an important step towards the utmost process safety and quality assurance, but would open up further operational reserves in production with the same machines. Graule: “I am sure that we will have even more prevention in the future. The Cube provides the perfect information in this regard.“