Performance boost with NeoMill face milling cutter

“At BOGE, we are the centre of competence in supplying readily assembled and inspected compressor stages for screw compressors”, explains Mario Birkner, Production Manager for Organisation and Projects at the BOGE plant in Großenhain. The progressive company manufactures mechanical components for screw compressors. In Großenhain, around 40 employees produce very accurately machined rotors and housings in highly automated machining centres. During assembly, they are turned into functionally tested mechanical units, which are then delivered to the main plant in order to be completed with drives as well as measuring and control technology. During manufacturing, the focus is on optimum cost-effectiveness. The manufacturing costs for new products are already defined to a large extent during the design stage, in line with the global market standard. Therefore, the corresponding department is located in close proximity to the production. The developers can thus easily communicate with the production specialists. This helps designing products which are immediately ready for production and on time.

“After development, I take care of coordinating the machining operations for the components, so that we can achieve stable, safely controllable and cost-optimised processes”, explains Kevin Schmidt, responsible for project handling of prototypes in production. The cast-iron rotors and housings are machined separately, each on a highly automated production line or island. For new products, the tools and machining parameters suitable for optimal results need to be determined first. Further essential aspects are other general conditions, such as runtime limits or the expenses for maintaining or changing the tools. In addition, there is the design and production of suitable clamping devices and fixtures as well as the definition of test equipment, test fixtures and test plans to ensure the desired high level of quality. Finally, the plant also has test stations for examining the behaviour of units under real-life conditions.

“There are many critical machining processes for housings, e.g. position bores or the bearing areas in rotors,” knows MAPAL’s application engineer Heiko Süss. Often, strict IT6 or IT7 precision requirements have to be met. This is where fine boring tools from MAPAL, designed exactly for these tasks, come into play. Not only is maximum precision important here – machining times must also be as short as possible. Well-designed multi-stage tools often result in low material removal rates that are sufficient to carry out several machining steps. Moreover, the custom tools achieve considerably closer tolerances and better surface qualities while maintaining the same high process reliability. In this area, BOGE and MAPAL have had a close partnership in development cooperation for a long time.

In the early phase of new projects, Heiko Süss already receives an inquiry from BOGE regarding the tool concept to be used for optimal machining of the new components. The machining solution suggested by MAPAL is then elaborated on within the team and validated in tests.
 

“In our discussions, other questions always arise in addition to the actual topic of conversation”, says Kevin Schmidt. One of these conversations with Heiko Süss was about the unsatisfactory performance of the previously used face milling cutters from a market competitor for roughing thrust bearing caps. These milling cutters were fitted with indexable inserts and had a diameter of 160 mm. However, their machining performance in roughing was insufficient, so that two or sometimes even three cuts were necessary in order to remove the required material thickness. Süss made Schmidt aware of the new NeoMill face milling cutters with radial indexable inserts and recommended a NeoMill-16-Face face milling cutter with a diameter of 125 mm for this task. The tool is fitted with ten indexable inserts, each of them with eight cutting edges on both applicable sides and was used in production for tests lasting several weeks.

„Mit diesen neuen Werkzeugen konnten wir einen wirklich überzeugenden Erfolg erzielen“, freut sich Mario Birkner. Die von zwei auf vier Millimeter erhöhte Zustellung ermöglichte bereits eine Halbierung der erforderlichen Maschinenzeit. Darüber hinaus konnte aufgrund des weicheren Schnitts und der dadurch geringen Leistungsaufnahme der Maschine der Vorschub verdoppelt werden, sodass die Bearbeitungszeit um mehr als 60 Prozent zurückging. 

Die Standzeit pro Schneidkante der Wendeschneidplatten resultierte in weiteren Zeit- und Kostenvorteilen: 60 statt bisher 45 Minuten. Außerdem sanken auch die Kosten pro Schneidkante. Denn die jetzt eingesetzten, achteckigen (ONKU) Wendeschneidplatten aus dem NeoMill Programm von MAPAL besitzen eine negative Grundform, sind daher beidseitig einsetzbar und verfügen in der Summe über je 16 Schneidkanten. So ist ein kompletter Austausch des Plattensatzes erst nach 16 Einsatzstunden statt wie bisher bereits nach sechs Stunden erforderlich, mit den entsprechend positiven Auswirkungen auf den Wechselaufwand und die Handlingskosten. Im direkten Vergleich mit dem zuvor eingesetzten Fräser ergibt sich bei der Bearbeitung von 1.200 Teilen eine Einsparung von 45 Maschinenstunden. 

Die volle Nutzung dieser Vorteile gelang allerdings erst im Rahmen einer Optimierung der Maschinensoftware: Eine adaptive Vorschubregelung reduzierte bis dato anhand bestimmter Parameter die vom NC-Programm vorgegebenen Vorschubgeschwindigkeiten automatisch. Diese Automatik erwies sich für die rasante Bearbeitung des NeoMill Fräsers als zu träge. Der MAPAL Planfräser konnte sein volles Leistungspotenzial erst nach dem Deaktivieren dieser Funktion entfalten. Bei künftigen Projekten, so Mario Birkner, werde man auch für weitere Bearbeitungen gerne den Kontakt mit MAPAL suchen.