Influence of dressing strategy on tool wear and performance behavior in grinding of forming tools with toric grinding pins

The performance of grinding tools in grinding processes and the resulting surface and subsurface properties depend on various factors. The condition of the grinding tool after dressing is one of these factors. However, the influence of the dressing process on the condition of the grinding tool depends on the selected process parameters and is difficult to predict. Therefore, this paper presents an approach to describe the influence of the dressing process on tool wear of toric grinding pins and the resulting subsurface modification. For this purpose, toric grinding pins with a vitrified bond were dressed with two different strategies and the wear and operational behavior were investigated when grinding AISI M3:2 tool steel with two different grinding strategies. In general, the investigations have shown that the dressing process influences the performance and wear behavior differently depending on the grinding strategy used. The degree of clogging is influenced by the geometric contact sizes. In the case of small engagement cross sections with simultaneously large contact lengths the thermal tool load is distributed over a small annular area of the tool and favors clogging. Crushing and additional transverse loading of the grains result in an almost clog-free tool surface. This also leads to a lower G-ratio. Crushing leads to an intensified decrease of the torus radii. The influence of the dressing strategy can also be observed in the induced residual stresses. Toric grinding pins dressed by crushing induce lower compressive residual stresses into the workpiece, which can be attributed to the self-sharpening effect. This effect reduces the mechanical and thermomechanical load of the workpiece during machining

Cold Micro Metal Forming

This open access book contains the research report of the Collaborative Research Center “Micro Cold Forming” (SFB 747) of the University of Bremen, Germany. The topical research focus lies on new methods and processes for a mastered mass production of micro parts which are smaller than 1mm (by forming in batch size higher than one million). The target audience primarily comprises research experts and practitioners in production engineering, but the book may also be of interest to graduate students alike

Hybrid Bulk Metal Components

In recent years, the requirements for technical components have steadily been increasing. This development is intensified by the desire for products with a lower weight, smaller size, and extended functionality, but also with a higher resistance against specific stresses. Mono-material components, which are produced by established processes, feature limited properties according to their respective material characteristics. Thus, a significant increase in production quality and efficiency can only be reached by combining different materials in a hybrid metal component. In this way, components with tailored properties can be manufactured that meet the locally varying requirements. Through the local use of different materials within a component, for example, the weight or the use of expensive alloying elements can be reduced. The aim of this Special Issue is to cover the recent progress and new developments regarding all aspects of hybrid bulk metal components. This includes fundamental questions regarding the joining, forming, finishing, simulation, and testing of hybrid metal parts

Numerical simulation and experimental validation of the cladding material distribution of hybrid semi-finished products produced by deposition welding and cross-wedge rolling

The service life of rolling contacts is dependent on many factors. The choice of materials in particular has a major influence on when, for example, a ball bearing may fail. Within an exemplary process chain for the production of hybrid high-performance components through tailored forming, hybrid solid components made of at least two different steel alloys are investigated. The aim is to create parts that have improved properties compared to monolithic parts of the same geometry. In order to achieve this, several materials are joined prior to a forming operation. In this work, hybrid shafts created by either plasma (PTA) or laser metal deposition (LMD-W) welding are formed via cross-wedge rolling (CWR) to investigate the resulting thickness of the material deposited in the area of the bearing seat. Additionally, finite element analysis (FEA) simulations of the CWR process are compared with experimental CWR results to validate the coating thickness estimation done via simulation. This allows for more accurate predictions of the cladding material geometry after CWR, and the desired welding seam geometry can be selected by calculating the cladding thickness via CWR simulation. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Development of innovative TCT saw blades for high speed cutting of metallic alloys

The subject covered in this thesis concerns the development of an innovative PVD coated multipoint cutting tool with cemented carbide brazed inserts for high-speed cutting of ferrous alloys. The aim of the research was to optimize the properties of the constituent materials in order to maximize their durability and provide a constant level of surface finishing of the machined parts. Fast cutting technologies are nowadays spreading because of the high productive rate that they guarantee, but on the other side wear is more severe with high speed cutting. Tungsten Carbide Tipped (TCT) saw blades are typically used in wood cutting but since 30 years are gradually taking the place of traditional band saws due to the higher cutting speed that are possible to reach and thanks to a better surface finishing on machined surfaces. The research work that was part of an industrial project was divided into three steps: 1. characterization of cemented carbide grades for application in machining 2. optimization of the cutting geometry 3. development of a tailored CAE – PVD coating. The first part of the research work involved the study of literature in order to define the most suitable grades of cemented carbide for experimentation and to define some possible coating composition and architectures. Both plain grades and mixed grades with secondary Ti and Ta carbides were chosen, the relations among hardness, toughness, grain size and wear resistance were investigated through microstructural and mechanical characterization; finally discs made of cemented carbide were tested against pins of steel to characterize the resistance to sliding wear. From this characterization a mixed grade cemented carbide with 12% cobalt binder and micrometric grain size was chosen due to the best toughness properties shown from characterization. Saw blades work under interrupted cutting conditions so toughness was required as the most important feature. In the second part of this study the cutting geometry of the cemented carbide inserts was optimized via experimental cutting tests and CAE methods. After a set of benchmark cutting tests on an industrial sawing station, the experimental cutting forces were calculated analytically and than used to calibrate a FEM 2D numerical calculation model. Two cutting geometries were then tested among those simulated: -15° and -25° rake angles. Thanks to the use of an hard metal with increased toughness (KIC> 15 MPa), a tool with a rake angle of -15 ° has been designed to guarantee lower cutting forces (less than 90 N in the first cuts), friction and temperature on the surface of the tool’s rake face (Figure 1). By experimental validation of the simulated geometries the cutting model gained predictive power. In the second phase of the work, three CAE - PVD coatings of the Al - Ti - Cr - N system were studied. Two of them were monolayer and one multilayer. The aim of this part of the work was to investigate the mechanical and microstructural properties of the analyzed coatings using different experimental methods to describe their behavior. The coatings were characterized not only from the mechanical point of view (hardness, toughness and adhesion) but also from the morphological (defective), and microstructural point of view. From the tests carried out, a multi-layered coating with improved toughness for use in interrupted cutting was designed

Additive Manufacturing Materials: Fabrication of Aluminum Matrix Composites

This study aims to validate the ability of cryomilling for the production of high-quality aluminum matrix composite (AMC) powder for powder bed fusion (PBF) additive manufacturing (AM). The spectrum of aluminum-based materials available for AM remains limited due to complex melting and solidification dynamics inherent to the process. To overcome these problems, fillers are often added to aluminum matrices to create a class of materials called AMCs that combine the ductility of aluminum with the stiffness of ceramic reinforcements. However, producing particulate composite feedstock powder for PBF that promotes full densification and microstructural homogeneity is nontrivial. Traditional liquid-phase processing through atomization is not suited to produce composite powders as particle segregation discourages composite homogeneity. AM powder production through solid-state mechanical alloying has been studied with limited success, primarily due to poor powder spreadability and inclusion of lubricants in the alloying process. Cryogenic mechanical alloying, termed cryomilling, enhances homogeneity between matrix and reinforcement particles by recurrent fracture and cold welding sans lubricants but remains unexplored for the fabrication of PBF feedstock powder. Herein, a method for producing homogeneous, flowable AMC powder designed for PBF is described in detail. Various compositions, powder masses, and milling times were explored to tune particle morphology, composition, and composite homogeneity. A representative spreading test of cryomilled materials qualitatively indicated that distinct cryomilling parameters may produce powder with comparable spreading characteristics to gas atomized AlSi10Mg, a common PBF feedstock material. Cryomilled AMCs displayed superior Vickers microhardness to unmilled AlSi10Mg powder after compression and sintering. This research provides an indication of cryomilling capabilities to become an effective production method of custom alloy powder for PBF-AM

Micro-manufacturing research : drivers and latest developments (Keynote Paper)

Increased demands on micro-products and miniaturised systems/devices may have been a main driver to the rapid growth of the interest in research in micro- and nano-manufacturing. It seems, however, not to be the only reason why so much funding has been made available for researchers to be able to conduct research in this emerging field. A review was conducted recently with a view to gaining a clearer view of demands on the applications and on trends in developments in micro-manufacturing, by looking at the market, research topics, projects, interactions with industry, outcomes and applications. It was found that there have been significant changes/advances in micro-manufacturing research, compared to what had been undertaken and achieved in 5 ~ 10 years ago, being reflected especially by: (i). micro-manufacturing research bridging “nano-manufacturing” and “macro-manufacturing” and hence, bringing nano-technology into real-life and affordable products; (ii). addressing multi-length scale manufacturing problems and hence, linking it to macro-sized product manufacturing, which adds its relevance to general manufacturing and wide-sector applications; (iii). micro-manufacturing research being shifted from “process focus” to “market/product” driven research and technological development addressing production capability, product quality, pilot production line demonstration and delivery; and (iv). micro-manufacturing research playing roles in helping to transform traditional industry and products. These new developments may justify past and current significant investment in research and technological development in micro- and nano-manufacturing, and suggest more significant impacts to come in near future

Special Issue of the Manufacturing Engineering Society (MES)

This book derives from the Special Issue of the Manufacturing Engineering Society (MES) that was launched as a Special Issue of the journal Materials. The 48 contributions, published in this book, explore the evolution of traditional manufacturing models toward the new requirements of the Manufacturing Industry 4.0 and present cutting-edge advances in the field of Manufacturing Engineering focusing on additive manufacturing and 3D printing, advances and innovations in manufacturing processes, sustainable and green manufacturing, manufacturing systems (machines, equipment and tooling), metrology and quality in manufacturing, Industry 4.0, product lifecycle management (PLM) technologies, and production planning and risks