Sustainable and cost-efficient surface finishing of balancing weights
Today centrifuges are the most commonly used systems for cleaning and recycling the process water required in mass finishing operations. For example, the globally leading supplier of balancing weights, Wegmann Automotive, is utilizing a fully automatic Rösler centrifuge, model Z1000. As a pilot customer Wegmann expanded the software for its centrifuge with the “advanced version” of the innovative digital process water management system from Rösler Smart Solutions. Compared to the previously practiced manual process control the new software package with its digital algorithms has produced considerable benefits. It helped not only to improve the overall product quality but also resulted in substantial cost savings.
When it was founded in 1882, the company initially was building carriages. From these modest beginnings Wegmann expanded into a corporate entity with three different business units. In their respective fields all three units are global market and technology leaders. The Krauss-Maffei Wegmann GmbH & Co. KG develops and produces a wide range of products in the field of national defense. The Schleifring GmbH is a leading provider of systems for the transfer of energy, electrical signals, data and electronic media. With a huge portfolio of balancing weights, tire valves, battery terminals, tire pressure control systems, including suitable service kits and special weights, the Wegmann Automotive GmbH supplies not only numerous automobile manufacturers but also serves the entire automotive aftermarket. The company, located in Veitshöchheim, Germany, produces more than one billion components per year. As global leader for balancing weights Wegmann Automotive produces percussion and adhesive weights for steel and aluminum wheels.
A mass finishing operation that must meet stringent demands
The balancing weights are made as stampings from steel and galvanized steel as well as die-castings from zinc or zinc alloys. Eugen Weizel, the department manager for mass finishing and coating at the Wegmann Automotive company, explains: „After the stamping or die-casting process the weights undergo a part-on-part mass finishing operation in a rotary vibrator. The goal is to completely remove the residual oil left over from the stamping process and the water-based mold release agent left over from the die-casting operation. At the same time the utilized compound provides a corrosion protection for the steel parts. On the other hand, the zinc die-castings require a certain surface tension for the subsequent coating step. The surface tension is carefully monitored and controlled.” Mr. Weizel’s colleague Manuel Salomon, as WAPS (short for Wegmann Automotive Production Systems) responsible for setups in the coating department, trainings and Lean Management, adds: “A high compound concentration in the process water is beneficial for the corrosion protection on the steel parts. But if it is too high, we will not achieve the required surface tension on the zinc components. This can cause inadequate coating results and may even force us to scrap some products.”
The product quality depends on the quality of the process water
Since the process water is recycled, the process water cleaning operation with a fully automatic Z1000 centrifuge from Rösler and the control of the compound concentration are key factors that determine the quality of the balancing weights. Manuel Salomon continues: „When the mass finishing machine and the centrifuge were commissioned, we quickly recognized that there is a close correlation between the process water quality and the quality of our products. Therefore, we carefully measured the compound concentration once per week and recorded the measured results. This allowed us to precisely define the compound concentration for our finishing process and correct it as needed.” Since measuring and recording the concentration values was quite time consuming, Wegmann gladly accepted Rösler’s offer to utilize the advanced version of the “digital process water management system” as a pilot user. Eugen Weizel concludes: „We quickly recognized the benefit to further develop and refine the software package together with Rösler, and, at the same time, to deepen our process knowledge.”
The new, interactive monitoring and control system for process water cleaning and recycling with semi- and fully automatic centrifuges is integrated into the centrifuge controls and allows the monitoring, recording and evaluation of all relevant process parameters. At Wegmann this includes measuring the compound concentration by titration or refraction (BRIX), the pH value, the process water conductivity, the water hardness, the microbiological contamination with bacteria, yeast and fungi, chloride contents, CSB value (chemical oxygen demand) and BIT concentration (biocide in the process water. The system also monitors the appearance and the smell of the process liquid. The process water parameters to be monitored can be individually selected and their values adapted to the respective finishing requirements.
In the basic version of the digital process water management system from Rösler Smart Solutions the samples are taken manually and analyzed with suitable measuring devices that can also be supplied by Rösler. After the data have been entered into the system, the algorithm in the software determines if the measured values are within the specified limits. In case of deviations the dashboard displays suitable actions, which can be immediately implemented. In addition, the technical background and corrective actions are explained in detail. This allows the operator to undertake the measures required to bring back the values into the acceptable range and to secure the desired process stability. Since all parameters are stored in the system, they can be retrieved at any time, for example, in the form of a table or a chart. The latter helps to prevent unwanted and costly downtimes by carrying out necessary process water changes during periods, when they are not interfering with the manufacturing operations. The complete documentation of the operational parameters is also a valuable tool to prove the process quality and process stability during quality audits as well as for validation purposes.
Recommended actions can also be called up in case of events that affect the overall quality of the mass finishing process. This includes foaming during the process, corrosion of the work pieces or insufficient work piece cleanliness that could negatively affect subsequent manufacturing steps. Manuel Salomon comments: „The pointers and recommended actions are extremely helpful. In the past we measured the process parameters. But when it came to the necessary corrections, we were entirely on our own. And in case of process problems we had to search for solutions ourselves, or we had to ask for help by telephone. Today the digital system provides all the support we need. This is especially helpful for colleagues with little knowledge of mass finishing and process water cleaning and recycling.”
A simple solution that can be quickly implemented
The smart process water management system has been in operation at Wegmann Automotive since the middle of March this year. Eugen Weizel remarks: „The software structure is well organized and easily understandable. And the system can be fully utilized after a short training. All critical data are arranged so that they can be viewed at a glance. And the entire information is presented in an easy-to-understand manner.”
While in the past the compound concentration was only measured once per week, now it is measured twice, once in the morning and once in the afternoon of a particular day. In addition, the pH value is recorded, and the appearance and smell of the process water is monitored. „This approach provides us with valuable information about our process. For example, the development of the compound concentration tells us that due to a higher volume of oily work pieces we must increase the compound dosing rate to maintain the required process water quality,” explains Manuel Salomon, who continues: „Another example is the microbiological contamination. In the past we did not control this at all. If the contamination is too high, it can have an adverse effect on the corrosion protection of steel parts.”
Significantly improved process stability and cost-efficiency
For monitoring the various parameters with the digital process water management system Wegmann Automotive needs about 20 minutes per week. Compared to the once-per-week measurement of the compound concentration this requires about 15 minutes more. But the technical and economic benefits achieved by the digital system are so significant that the company gladly accepts the fact that a bit more time must be invested. Eugen Weizel concludes: „With the digital process water management system we find out quickly, if for example, the compound concentration is no longer adequate. Since this could have an adverse effect for subsequent manufacturing steps, we are grateful to have such a valuable, early warning system. Our finishing process is now not only a lot more stable but also more economical.” Therefore, it is not surprising that the company is interested in the next version of the digital process water management system from Rösler Smart Solutions. This allows the automatic measurement, evaluation and recording of the process parameters.