Elimination of surface spiral pattern on brake discs

Rodrguez et al. / J Zhejiang Univ-Sci A (Appl Phys & Eng) 1673-565X Elimination of surface spiral pattern on brake discs* Adrin RODRGUEZ 1 L. Norberto LPEZ de LACALLE 1 Asier FERNNDEZ 1 Stephan BRAUN 0 0 Department of Mechanical Engineering, Georg-Simon-Hochschule Nuremberg, Faculty of Engineering , Kesslerplatz 12, D-90489 Nuremberg , Germany) 1 Department of Mechanical Engineering, University of the Basque Country (UPV/EHU), Faculty of Engineering of Bilbao , Alameda de Urquijo s/n. 48013 Bilbao , Spain) ( 2 Project supported by the Etortek proFUTURE II Project and UPV/EHU (No. UFI 11/29), Spain Zhejiang University and Springer-Verlag Berlin Heidelberg 2014 Nowadays, brake disc manufacturers are seeking new finishing techniques to offer economical solutions to their customers and so become more competitive. The elimination of the surface spiral pattern after turning operation is a challenge to avoid braking problems at the early life of the component. This paper presents a practical low-cost solution to finishing this kind of component. Concretely, a detailed study of the brushing process as an alternative solution to the conventional grinding process is performed. The limited literature regarding this topic implies the necessity of a full study of the process prior to any industrial application. The influence of process variables on the final surface was analyzed in this work. In addition, the tool wear and tool life behavior, the influence of the abrasive type used and the originating forces during the process were taking into account. Once the process was established, various prototypes were finished in order to check the feasibility of the process and to pass the required quality control. Results show that brushing is a feasible and economical alternative for brake disc finishing. The surface quality obtained was shown to be equal or better than grinding, with reduced costs and manufacturing time. Brake disc; Brushing; Surface roughness; Spiral pattern; Cast iron doi; 10; 1631/jzus; A1300236 Document code; A CLC number; TH13 - Thornton et al., 2011). There are also discs made of carbon matrix composite materials, but used only in racing cars and aircraft brakes due to their high cost. Currently being developed are brake discs using aluminum silicon carbide composites (Fan et al., 2011; Shivamurthy and Surappaa, 2011). Their weight makes them attractive, but the poor heat dissipation makes this technology unfeasible currently. Discs are cast parts that are dry-machined using ceramic inserts. Turned surfaces present a characteristic uniform spiral roughness pattern (Taha et al., 2010), which can cause problems during the first braking. In some cases it causes noise, vibration or deviation in the trajectory of the vehicle. To avoid these problems and to optimize the braking force, the spiral pattern of the turning process has to be eliminated. This fact is becoming a major problem for discs manufacturers, who try to deliver disks to develop their full braking potential in all the braking processes, even in the first braking. A conventional solution adopted by manufacturers is grinding, but only market leaders can offer this service due to its high cost. Commonly, vibration problems in this field are known as judder and squeal. The first one is an error state with partial brake load and stick-slip oscillations. It can take place in clutch or brake systems. Stick-slip oscillations are also friction induced (Centea et al., 1999; 2001). The second one usually occurs in the frequency range between 1 and 16 kHz. Some studies showed the importance of the disc topography in the generation of automotive disc brake vibrations (Heussaff et al., 2012; Yoon et al., 2012). Some commonly used techniques to reduce noise and squeal, and solve other important problems during the braking process can be shot-blasting (Bergman et al., 1999) and grit-blasting (Hammerstrm and Jacobson, 2006). The main idea is to change the friction characteristics of the initial surface avoiding the typical turning pattern. Nowadays, but only when a customer requires it, the tracks of the brake disc are ground. This process is performed on large and expensive grinding machines. Despite the developments in grinding technology and lubrication systems (Sanchez et al., 2010), grinding is a costly process in which usually much of the installation equipment comprises the lubrication system. In this paper, a cost-effective technique to achieve the ideal quality finish of the discs is proposed, avoiding large investments in machinery and allowing the manufacturer to offer ground disks to all their customers. There are some techniques for finishing and polishing surfaces apart from grinding, such as burnishing (Rodrguez et al., 2012), laser polishing (Ukar et al., 2010) or even shot-peening (Chaise et al., 2012). Nevertheless, in this work the brushing technology was investigated. Brushing is a production technique that has been used for many years in manual and semi-automatic processes of surface finishing. Apart from optimizing the surface of machined parts, it is also possible to remove burrs and marks with filamentary brushes (Mathai and Melkote, 2012; Chen and Yu, 2012). Brushes can be made of natural fibre, metallic wire or abrasive-filled polymeric fibres and there are many different types available. There are for example wheel brushes, cup brushes, end brushes, and abrasive ball honing brushes which are employed depending on the current process and part (Gillespie, 1999). To remove material, the rotating cutting-fibres with special geometries exert a force on the surface of the workpiece. This force depends on the rotation speed (S), the depth of cut (ap) and the feed rate (F), and it has a huge influence on the quality of the surface. With orthogonal use of cup-brushes, the rotation speed leads to a spread of the fibres due to the centrifugal force and thus shortens and widens the cutting-fibres especially on the outer face of the brush. Thus, there is a limit to the rotation speed depending on the type of brush and its diameter. Some studies developed models focused on the dynamic behaviour of rotating brushes (Vanegas-Useche et al., 2008; 2011) or on finite element models of the brushing process (Wahab et al., 2007; VanegasUseche et al., 2011a; 2011b). However, there is no more information in the literature about this, so it is difficult to find the best parameters which are needed to achieve the optimal result. Due to the deformation of the fibres and the fact that the brushes are ductile, the material removed is much less than the adjusted nominal depth of cut (apn). Nylon/abrasive brushing tools are used in surface finishing processes for a wide range of applications, such as blending, polishing, and edge-radii (Overholser et al., 2003). These flexible brushing tools can easily be adopted in milling, turning or grinding machines so that there is no necessity to invest in new machinery. M (...truncated)