This thesis was written mainly during my time as postdoc researcher at the Werkzeugmaschinenlabor (WZL) at the RWTH Aachen University, and at the Laboratory for Manufacturing and Sustainability (LMAS) at the University of California Berkeley. The research on the life cycle engineering of abrasive tools was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through the project LI1939/3-1. Thank you to the DFG for the support and the opportunity to study abroad.
I thank Prof. Klocke from the bottom of my heart for mentoring me during my time as research associate at his institute and beyond. Grinding technology, detailed research, and teaching are our shared passion. Prof. Klocke trusted all the while that pursuing an academic career would be the right way for me to go. Thank you for being such a great mentor to me and for introducing me to the international research community!
Professor Dornfeld earns my deepest gratitude for hosting me in his laboratory and providing me with excellent opportunities for networking. I learned so much from his visionary yet applied research on sustainable manufacturing.
Thank you to Prof. Karpuschewski for being a role model and inspiring me to pursue an international research fellowship. I am also grateful for his advice on this thesis.
Dr. Busch was one of my closest discussion partners and a very great help. I thank him wholeheartedly. Many thanks also to Dr. Sigwart and Mr. Noichl from Tyrolit; Dr. Hall and Dr. Arcona from Saint-Gobain Abrasives Norton; Prof. Vollstadt and Dr. List from Vollstaedt-Diamant; Dr. Bot-Schulz and Dr. Pahler from Saint-Gobain Abrasives; Dr. John Barry from E6; Dr. Magg from Tesch; Mr. Danner from Elbe Schleifmittel; and Dr. Paul and Dr. Michels from Wendt. I am thankful for all the insights into how companies secure the sustainability of their abrasive tooling systems. Thank you to Prof. Aurich for the inspiring cooperation on the CIRP keynote paper on sustainability in abrasive processes.
I am thankful for all the technical help from my former faithful student assistants Seamus Laprell and Janis Thiermann, and guest researchers Sabine Mannebach, Zhiwei Zhang, and Gero Corman. Sabine Ms. Mannebach conducted the case study on CBN and corundum tools thoroughly.
Many thanks to Prof. Garret O’Donnell, Trinity College Dublin, Dr. Markus Weiss, Tyrolit, Benjamin Doebbeler, Werkzeugmaschinenlabor (WZL) at the RWTH Aachen University, and Maria Celeste Castillo, University of California Davis for reviewing the thesis thoroughly.
I am thankful for the cordial atmosphere at the Aachener Schleifer Group and at the UC Berkeley LMAS. I would like to thank Dr. Bernd Meyer, Dr. Michael Duscha, Guido Kochs-Theisen, Peter Ritzerfeld, Dr. Dirk Friedrich, Dominik Schluetter, Dr. Holger Groening, Dr. Moneer Helu, Dr. Margot Hutchins, and Dr. Daeyoung Kong, just to name a few of all the great laboratory members at both institutions.
Last, but not least I am grateful for the support and encouragement by my husband Andor and my daughters Kira and Kim, by my parents, my sister Annika, my extended family, and best friends.
Das 21. Jahrhundert fuehrt die Menschheit an ihre natuerlichen Grenzen. […] Welche Moeglichkeiten haben die Unternehmen des produzierenden Gewerbes, durch effizientere Technologien sowohl Kosten als auch Ressourceneinsatz und Emissionen zu reduzieren? […] An die Stelle von «maximaler Gewinn aus minimalem Kapital» muss «maximaler Gewinn aus minimalen Ressourcen treten». [FHG08]
Translation: “The 21th century leads humanity to its natural limits. [. ] What options do manufacturing companies have to reduce costs, resource use and emissions through more efficient technologies? […] «Maximum profit from minimum capital» needs to be replaced by «maximum profit from minimum resources».” [FHG08].
Looming shortages of resources and energy induce a growing importance of sustainability in manufacturing. In the long run, the manufacturing paradigm has to shift from non-sustainable mass production to a sustainable environmentally conscious one [UMED12]. Furthermore, producers will have higher responsibility for the product life cycle in the future. Manufacturers may have to manage various legislative restrictions on product ingredients [e. g. the European REACH initiative (Registration, Evaluation, Authorization and restriction of Chemicals]) [UMED12]. In addition, customers increasingly demand greener products, which leads to more competition in the sustainability and manufacturing of the products. The World Commission on Environment and Development, also known as the Brundtland Commission, coined the definition of sustainable development as meeting the needs of the present without compromising the ability of future generations to meet their own needs [UN87].
Abrasive processes, also called machining with geometrically undefined edges, represent a key technology with high performance, process stability, and quality tolerances. Abrasive processes are applied in nearly every production, even if this includes the manufacturing of the mold. Abrasive processes are also core technologies in developing new energy systems as well as in improving efficiency of existing products. Nevertheless, the consideration of sustainability aspects in abrasive machining is just arising, but has a high recognition by the industry [OLIV09].
© Springer International Publishing Switzerland 2016 1
B. Linke, Life Cycle and Sustainability of Abrasive Tools,
RWTHedition, DOI 10.1007/978-3-319-28346-3_1
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Abrasive processes use grits to remove material. The engagement physics of grit and workpiece can be energy-bound, force-bound, path-bound, or room-bound grits (Fig. 1.1). Except for the energy-bound principle, all processes use abrasive tools consisting of abrasive grits in a bonding or a slurry paste. The abrasives should be harder than the workpiece material to form chips. Splintering of dull grits leads to self-sharpening and can be forced by proper abrasive grit design. In the case of path-bound grits, bonding has to hold the grits until they are too blunt, then relieve them and expose new sharp grits. The pores in a bonded or coated tool are important to supply cooling lubricant and remove chips from the contact zone. The abrasive layer might be attached to a body or backing material. All components and their composition affect the sustainability of the abrasive tools and abrasive processes. This work focusses on grinding tools.
The advantages and problems of abrasive tools arise from their often undefined cutting edge shapes, edge orientation, and number. Due to the high number of active cutting edges in the grinding tool, grinding is advantageous as it is not ruined by failure of a single cutting edge, like cutting [WERN73, p. 67]. However, the choice of an appropriate abrasive type is difficult because the interaction between abrasive grit, workpiece material, and the machining result is fairly unknown [LUDE94, p. 1].
In 1968, Malkin stated that “the main difficulty encountered by the grinding engineer is the choice of the grinding wheel best-suited for a given work” [MALK68]. This statement is still true today. The design of grinding tools holds the dilemma of providing either a cheap, mass-produced product versus an expensive, customized product. The range of machinable workpiece materials for a certain wheel has to be balanced against the tool performance. In addition, the possible workpiece geometries depend on the flexibility of the tool, e. g. the dressability of conventional wheels against pre-profiled superabrasive tools. As consequence, a mass produced tool can be used for several applications, but will never be as effective as a tool designed for one special purpose.
Several milestones in the development of abrasive grit materials and bonding systems, and the refinement of the tool components and manufacturing processes
have led to large improvements in process performance (Fig. 1.2). The life of the grinding tool is intertwined with the life of the product produced by grinding (Fig. 1.3). Similar to the manufactured product, an abrasive tool life has four phases: raw material extraction, manufacturing, use, and end of life. The use phase coincides with the machining process of another product. This thesis will discuss all life cycle phases of a grinding tool.
Abrasive tool compositions and manufacturing techniques are widely company proprietary and development is still in progress. As the design process of a grinding tool relies on the expertise of the tool manufacturer, it is often not a transparent procedure to the customer. Therefore, it is hard to comprehend considerations on sustainability. This thesis summarizes publicly available knowledge and unveils how it relates to sustainability.
Traditionally, sustainability has been viewed in tree categories or pillars: economy, environment, and society. However, this is not sufficient because it
disregards many decisions heavily based on technological considerations. For example, choice of grit size does not translate easily into one of the traditional three pillars of sustainability but depends on part surface roughness which is a technological factor. Therefore, in this work sustainability for abrasive tools is viewed under the following four aspects:
• Economics in terms of productivity and costs
• Environment in terms of energy use, materials use, waste, recyclability, emissions, etc.
• Society in terms of worker safety, health, and education
• Technology in terms of feasibility, workpiece quality, best practice, performance
This thesis revises the state of the art of research and common practice in the field of abrasive tooling systems for fine machining applications. Despite the diverse technical terms used in the literature, this thesis uses uniform terms.
Life cycle considerations and sustainability aspects in grinding are trend-setting perspectives, which are discussed in this thesis for the first time comprehensively throughout. All Chaps. 2—5 end with an interim model on technological, economic, environmental, and social sustainability.
Chapter 2 “Abrasives” analyzes the grit materials including their chemical composition, chemical and physical properties, material processing, and abrasive process performance. The knowledge of grit materials is crucial to understand the life cycle of abrasive tools holistically—where do the materials come from, how are they processed and what performance do they imply for the abrasive tool.
In a similar way, the bonding system defines tool performance and the tool manufacturing route. Therefore, Chap. 3 “Bonding Systems” explains different bond types, their ingredients, processing, and resulting tool performance.
Different abrasive applications need distinct tool designs as described in Chap. 4 “Abrasive Tool Types”. There is hardly ever only one perfect tool type, but tools can be used interchangeably affecting process performance and product quality. Moreover, the tool type affects the tool end of life significantly in terms of recyclability, re-use, or disposal.
The implications of the tool design and tool fixture specific to grinding tools are discussed in Chap. 5 “Grinding Wheel Macro-design—Shape, Body, and Qualification”. The shape and material of the tool affect its manufacture, raw materials, its use and end of life. In addition, the tool microstructure as explained in Chap. 6 “Grinding Wheel Micro-design—Abrasive Layer and Wear” changes tool performance and tool manufacture. The structure defines the tool topography that interacts with the workpiece surface and the wear phenomena, and affects sustainability since the grinding tool needs to be consumed during its use phase. Lower wear might yet lead to lower energy efficiency of the grinding process. Tool conditioning is an important method to adjust and regenerate tool profile and topography.
Having introduced the main factors of tool design, this knowledge needs to be tied back to sustainable grinding technology. Therefore, Chap. 7 “Sustainability of Grinding” first explains methods of Life Cycle Engineering (Life cycle assessment (LCA), Life cycle costing (LCC), Social life cycle assessment (SLCA), and Sustainability Indicators). Then a generic life cycle inventory of grinding processes is gathered to show the state of the art in grinding process sustainability. In addition, a new approach to understand and dissect grinding processes is explained and applied. This so called axiomatic grinding process model visualizes how process setup and tool design are connected to traditional quality indicators and newer sustainability indicators.
Chapter 8 “Sustainability Case Studies” then uses the concepts from the former chapter to discuss several examples: Vitrified bonded grinding wheels with corundum and CBN are compared with regard to their manufacturing strategies and energies; Hardturning and grinding are more or less favorable in terms of sustainability depending on the criteria. The example of leveraging gear grinding focuses on how the manufacturing process can improve the product performance towards higher overall energy efficiency, even if the gear grinding procedure consumes more energy. In a similar way, speed stroke grinding can improve product quality through a more sophisticated manufacturing process.
The final Chap. 9 “Future Prospectives” explains the actual market situation for grit material and introduces new abrasive tool concepts with potentially higher sustainability. All interim models from Chaps. 2 to 5 are combined to a generic model allowing for final conclusions on abrasive tool life cycle and sustainability.
The aims of this work are to
• Educate students and tool users on abrasive tools,
• Help tool manufacturers to emphasize sustainability in tool manufacturing,
• Help tool users to evaluate sustainability in tool use.