SCIENCE ners, so that a
SCIENCE ners, so that a large number of material combinations can be bonded with long-term stability, such as steel and carbide, PCD/CBN or cutting ceramics (Brockmann 2008; Luhn et al. 2012a; Moser et al. 2013). Moreover, the low-heat joining process prevents changes in the microstructure and the formation of microcracks in the cutting material (Brockmann 2008). Further adhesive applications in saw blades can take other advantages like vibration dampening, corrosion protection or reduction of mass inertia due to lightweight construction (Doobe 2012). In addition, the reworking costs for distortion and complex cleaning processes that arise during brazing are eliminated (Doobe 2012). Given the advantages mentioned above, especially the use of new cutting materials on circular blades (see figure 3), the adhesive bonding technology could have a huge impact on the circular saw blade industry. However, the use of adhesives instead of brazing alloys also brings some disadvantages. The lower thermal stability and the high effort to carry out surface preparation and implement process control have to be taken into consideration when dimensioning the joint. To perform a high reproduction rate of the reachable joint strength automation processes are necessary. Otherwise, a failure in the bond could have a fatal impact both on the machine and its operator. An overview of the advantages and disadvantages of adhesion technology is presented in table 1. Current research in the field of the adhesive bonding of cutting tools Individual research projects have been carried out in recent years to prove the usability of adhesives for different cutting tool applications. Darwish, for example, investigated the mechanical performance of bonded joints under thermal influence and the vibration dampening capability of milling tools with carbide tips and steel body. Bonded millers showed less wear, an improved surface roughness of the manufactured parts and only small differences in cutting forces. (Darwish und Davies 1989) Two funded projects in 2003 and 2007 (IGF no. 12792 N and 15028 N) used adhesives to join diamond-segments on circular blanks for stoneworking applications. They also investigated optimized joint geometries with finite-element methods and developed a partially automated maintenance module. Moreover, successful cutting of granite was carried out. (Stehr 2004; Stehr et al. 2003; N.N. 2010) figure 3: different cutting materials on a circular saw blade (left: tungsten carbide, right: SiAlON-ceramic) [Fraunhofer IPA, photographer: Rainer Bez ] advantages no thermally conditioned stress of the micro structure no thermally conditioned part deformation possibility of joining different materials High dynamic stability; high vibration dampening Bonded saw bands for stone-working were investigated in the IGF project no. 17193 N and cutting trials were successfully performed. In this context, new joint geometries, capable adhesives and surface treatment taken into account. (Kohl et al. 2014; Kohl et al. 2015; Schwarte 2015) The use of ceramics on circular saw blades was investigated at the Graz University of Technology. Here, the increase of the joint strength was identified as the main topic of operational tools. (Moser et al. 2013) The results of the IGF project no. 16031 BG proved the usability of bonded hard materials in metal machining. This included an extensive trial with adhesives and surface treatments to maximize the joint strength. (Luhn et al. 2012b; Jahn et al. 2012) Investigations of bonded ceramics for drilling tools were carried out by GFE e.V.. Here, the best machining results of carbon fiber reinforced plastics were performed with SiAlON-ceramic as cutting material. (Reich and Preiß 2015) The Institute for tool research and materials IFW carried out investigations with composite circular bimetallic blanks with a plastic or copper layer in between for vibration stabilization (Dültgen und Zobel 2014). Fraunhofer IPA also participates in the research activities concerning new joining methods for cutting tools and new approaches to substitute limited resources (Schumpp et al. 2018). Circular saw blades with bonded carbides have shown their ability to cut aluminum in a special intermittent cutting process developed by Fraunhofer IPA (Stroka et al. 2018). In a research project, funded disadvantages surface preparation of the joining parts limited form stability under thermal loading accurate process control time influence of the whole procedure table 1: excerpt of advantages and disadvantages of the adhesive bonding technology (Habenicht 2009) by the Federal Ministry for Economic Affairs and Energy (BMWi), the adhesion technology for the use in circular saw blades for wood-working and plastics was investigated both by Fraunhofer IPA and the Institute for tool-research and materials IFW. Initially, an analysis of the existing cutting forces and temperatures with conventional circular saw blades was conducted to gain knowledge of the load in the joint. The mechanical load was transferred to virtual models to analyze and optimize the joint geometry with finite element analysis in reference to the requirements of the adhesion technology. Simultaneous investigations of adhesives revealed different strengths of the joints depending on the adhesives and surface pre-treatments. In figure 4, different joint strengths of variable parameter sets are shown. Comparable brazed joints showed an average strength of 146,6 MPa. (Stroka and Keßler 2020) figure 4: joint strengths with different cutting materials and surface pre-treatments (Stroka and Keßler 2020) 14 No. 3 • August 2020
SCIENCE Fully carbide-tipped circular saw blades have been produced and grinding and sawing processes were performed. Individual bonded joints of the saw teeth could not handle the grinding forces and temperatures. The adhesive failed due to weak positioning which led to excessive loads and unwanted load cases like peel stress because of the manual joining process. Hence, an automation concept was developed. A conventional brazing machine for circular saw blades served as foundation. Initial tests have shown improved accuracy and the inductive hardening of the adhesive worked well. (Stroka and Keßler 2020) Future challenges for a successful implementation of the adhesive bonding technology Future research has to aim at a reliable industrial joining process, comparable to the brazing processes for the individual cutting tools today. Without full automation, the technical and economic goals of creating customer attractive products cannot be achieved. A big variety of surface treatment methods, adhesives and hardening processes are state of the art. Here, the main challenge lies in the right selection and implementation in the manufacturing process. A detailed view at the temperature surveillance, if infrared pyrometers are still used, is necessary because of the variable emissivity of the components. The identification of a better shape than the usual joint supports the bonding performance and has to be considered in the development process for new cutting tools for special applications. Depending on the mechanical and thermal stress in the joint, optimized joint geometries have to be developed. Conclusion The examples in this paper show the utilizability of the adhesion technology in the cutting tool industry. Over the last decades, intensive research has delivered good results because of improved adhesives, especially under thermal load. Automatic joining processes and machines will help to establish adhesively bonded cutting tools for special applications. The new cutting tools can draw advantage from the possibilities given by the adhesives in terms of vibration dampening and use of new cutting materials. Acknowledgment The authors would like to thank both the Federal Ministry of Education and Research for funding the “Innovationsforum Zerspanwerkzeuge” and the Federal Ministry of Economic Affairs and Energy for funding the Aif IGF-project no. 19446 N. Reference Brockmann, Walter (2008): Klebtechnik. Klebstoffe, Anwendungen und Verfahren. 1. Nachdr. Weinheim: Wiley-VCH. Darwish, S.; Davies, R. (1989): Adhesive bonding of metal cutting tools. In: International Journal of Machnine Tools and Manufacture 29, 1989 (Vol. 29, No.1), S. 141–152. Doobe, Marlene (2012): Hartstoffschneiden kleben statt löten oder schweißen. Online verfügbar unter https://www.springerprofessional.de/fertigungstechnik/ verbindungstechnik/hartstoffschneiden-kleben-statt-loeten-oder-schweissen/6593696, zuletzt geprüft am 08.07.2020. Dültgen, Peter; Zobel, Frank (2014): Schwingungsstabilisierung von Kreissägewerkzeugen durch Verbundbauweise für die Holzbearbeitung. In: HOB (9), S. 74–76. DIN 8593-8:2003-09, September 2003: Fertigungsverfahren Fügen. Habenicht, Gerd (2009): Kleben. Grundlagen, Technologien, Anwendungen. 6., aktualisierte Auflage. Berlin Heidelberg: Springer. Jahn, S.; Luhn, R.; Sändig, S.; Maul, T.; Reich, S.; Geiß, P. L.; Gramsch-Kempkes, S. (Hg.) (2012): "Tooltime" - Innovative Fügeverfahren in der Werkzeugtechnik. 10. Schmalkalder Werkzeugtagung 2012. Schmalkalden, 14./15. November 2012. Kohl, D.; Schwarte, S.; Heise, C.; Thiede, H.; Böhm, S. (2014): Adhesive joining of PCD cutting segments onto a saw band for machining mineral material. In: Weld World 58, 2014 (58), S. 237–244. Kohl, D.; Schwarte, S.; Mechthold, S.; Böhm, S. (2015): Einsatz der Klebtechnik bei der Fertigung von Sägebändern zur ressourceneffizienten Spanung mineralischer Werkstoffe. In: Schweißen und Schneiden 2015, 2015 (67 Heft 11), S. 664–672. Luhn, R.; Sändig, S.; Jahn, S.; Geiß, P. L.; Gramsch-Kempkes, S.; Maul, T.; Meister, L. (2012a): Hartstoffschneiden mittels Klebverbindung befestigen. Online verfügbar unter https://www.maschinenmarkt.ch/hartstoffschneiden-mittels-klebverbindung-befestigen-a-365324/, zuletzt geprüft am 08.07.2020. Luhn, R.; Sändig, S.; Maul, T.; Geiß, P. L.; Gramsch-Kempkes, S. (2012b): Geklebte Hartstoffschneiden. Herstellung von Hochleistungswerkzeugen. In: Adhäsion 05/2012, 2012 (5), S. 40–45. Moser, F.; Vallant, R.; Hampel, S. (2013): Kleben von Schneidkeramik-Sägezähnen auf ein Stahlsägeblatt. Grundlagenuntersuchungen und Potential. TU Graz, Graz. Institut für Werkstoffkunde, Fügetechnik und Umformtechnik IWS (mittlerweile IMAT). 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Final report on IGF project #12792 N Stehr, G. C.; Münz, U. V.; Glatzel, T.; Schäfer, H.; Brede, M.; Kolbe, J. (2003): Innovative Steinbearbeitungswerkzeuge mit geklebten Diamant-Schneidsegmenten (DVS 222), 2003, S. 90–95. Stroka, M.; Keßler, R. (2020): Branchenübergreifende Entwicklung und Untersuchung einer wärmearmen Fügetechnologie für schnelldrehende scheibenförmige Werkzeuge zur Holz- und Kunststoffbearbeitung. Final report on IGF project #19446 N " Stroka, M.; Schumpp, F.; Schneider, M. (2018): Geklebte Schneidsegmente im unterbrochenen Schnitt. Untersuchungen zum Einsatz geklebter Schneidsegmente für Kreissägeprozesse am Beispiel von Aluminium. In: wt Werkstattstechnik online 6, 2018 (108), S. 466–472. No. 3 • August 2020 15
