For economic and ecological reasons the cleaning and recycling of the process water in mass finishing applications has become indispensable. The quality of the finishing results depends to a large extent on the effectiveness of the actual process water cleaning operation. To better manage the numerous parameters of its cleaning and recycling system, Scherdel, a globally operating manufacturer of bent and stamped parts, upgraded its semi-automatic Rösler cleaning centrifuge with the digital process water management software package from Rösler Smart Solutions. It allows the interactive control of up to 13 parameters such as compound concentration, pH value or microbiological contamination. In case of deviations from the rated values the intelligent software issues corrective recommendations to the operators.
In his very first diesel engine Rudolf Diesel used already springs from the Siegmund Scherdel wire drawing company founded in 1889. Since then the company has evolved into a globally active operation that deals with forming, assembly and joining technologies as well as surface treatment. In addition, the company is also active in the manufacture of tooling and equipment. With 32 facilities around the world Scherdel actively supports its customers with services that range from initial briefings to volume production. The result are premium products that are not only used in the automotive industry but also in medical and electrical engineering as well as power generation. The products include stamped and bent parts, lock washers and components for electric vehicles. The latter are produced at the Scherdel Waldershof GmbH & Co. KG in Waldershof, Bavaria.
The components made from different steel alloys, stainless steel and non-ferrous metals frequently receive their final surface finish in mass finishing operations. Besides the basic finishing tasks like deburring and edge radiusing, clean surfaces with a high degree of cleanliness are an important requirement. Clean surfaces are essential for conducting a proper optical quality control. In this context the quality of the process water plays a key role.
Process water cleaning and recycling – for complex mass finishing applications
At Scherdel Waldershof the process water from the mass finishing operation is cleaned and recycled with a semi-automatic centrifuge. However, to date the process water quality was only controlled by a daily check of the compound concentration. And this was usually done by different people who had little understanding and knowledge of the intricacies of the process water cleaning and recycling operation. „The process water gets contaminated by oil from the stamped & bent parts, belt lubricants and metal and media fines. On the one hand this increases the conductivity, which can cause faulty readings during the optical controls. On the other hand, the guidelines regarding particle size and quantities were not always followed. All this resulted in costly rework and even scrap parts“, explains Tobias König, department manager for mass finishing & cleaning at Scherdel Waldershof.
Digital process water management results in transparency and generates knowhow
When Rösler suggested to him to test the digital process water management system “Advanced” from Rösler Smart Solutions as a pilot user, the department manager immediately agreed. This new software package for semi-automatic and fully automatic centrifuges allows the user-friendly monitoring, recording and evaluation of all essential process parameters. These are: The compound concentration (measured by titration or refraction index – BRIX), pH value, conductivity, water hardness, microbiological contamination by bacteria, yeast and fungi, chloride content, COD value (chemical oxygen demand), BIT content (biocides in the process water), appearance and smell. Depending on the particular requirements for a given mass finishing process, the respective process parameters can be individually selected. In the “Advanced” version of the digital system the water samples are manually collected and analyzed with suitable measuring equipment that can be supplied by Rösler with the software package. The determined values are also entered manually. Based on the entered data the algorithm in the software develops recommendations for immediate corrective actions so that deviations from the specified values for the respective process parameters can be corrected and, thus, ensure process stability. Besides the recommendations for immediate corrective action the software also provides information that explains the adverse effects on the work piece surface, if the various parameter deviations are not quickly corrected. Since all data are recorded, they can be retrieved and displayed in the form of tables and time charts. This helps prevent costly downtimes by unplanned process water changes and allows to schedule such changes for time periods when they are less disruptive.
„When Rösler presented the digital process water management system, we immediately recognized its potential for more transparency and a higher process stability. In addition, we realized that the recommended corrective actions along with the respective background information can be a tremendous educational tool that helps to increase the process knowledge of our employees“, concludes Tobias König.
Increased process stability and improved finishing quality
Scherdel Waldershof uses the digital process water management system with a semi-automatic Rösler centrifuge, model Z 800. This centrifuge cleans and recycles the process water from a Rösler mass finishing vibrator (model R 620) running in 3 shifts. The system controls the compound concentration and the pH value once per shift. A conductivity measurement takes place once per week. The microbiological contamination is checked whenever required. For example, this is the case, when the regularly monitored appearance and smell of the process water indicate that there might be a problem. The department manager explains: „The measurement and recording of the parameter values is easy and simple. We need about the same time for measuring and recording the compound concentration and the pH value as before.” He continues: „However, today we automatically receive an easy-to-read evaluation and a list of corrective actions that can be immediately implemented. This is a valuable tool to keep the process water stable and maintain a consistently high part quality. We have seen a reduction of rework and scrap parts by up to 50 %.“
The digital system issues not only recommendations for corrective actions when the parameters deviate from their rated values. Similar actions are proposed in case of events affecting the part quality and downstream manufacturing operations like corrosion, excessive foaming during the mass finishing process and insufficient cleanliness of the work pieces. To eliminate such problems the digital system issues detailed background explanations along with the recommended corrective actions. Tobias König concludes: „Most of the employees in my department have no special knowledge regarding mass finishing and handling of the process water. However, with the recommended corrective actions they not only learn what needs to be done, but they also acquire valuable process knowledge. This helps them understanding the relationship between the process water quality and the quality of the finished work pieces.“