Comparison of Ground and Laser Machined Wiper Geometry on Carbide Inserts for High Performance Finishing

AbstractCutting tool development is still driven by trial and error and therefore requires various prototypes and modifications. The normal manufacturing process for carbide cutting inserts includes die production, pressing, sintering, grinding and coating. A laser can provide an easy and economical way to make modifications and prototypes out of pressed inserts. The paper compares a normal pressed and ground insert with the same geometry using various laser manufacturing options. The insert features a wiper geometry for high feed per revolution and a chip breaker. As performance criteria the cutting forces and the machined surface quality were measured and analysed. It was found that the cutting edge and surface quality of the insert depends on the laser strategy and thus influences the cutting force and the workpiece quality. No difference was discovered comparing ground and laser machined inserts showing the potential for prototyping

Realisierung und Überprüfung eines 3D-Tastsystems für Mikro-Bauteile

Es wird ein neues 3D-Tastsystem vorgestellt, dessen Design nicht nur bezüglich isotroper Steifigkeit am Tastelement, sondern auch bezüglich wirtschaftlicher Herstellung der einzelnen Bauteile und deren einfacher Montage optimiert ist. Eine Verlagerung des Tastelementes resultiert in einer Änderung der Position und/oder Orientierung einer beweglich gelagerten Messplatte, in welche der Taststift geschraubt wird. Die Bewegungen der beweglichen Messplatte werden mit kapazitiven Sensoren gemessen. Die Geometrie des Tastsystems wird unter Verwendung der Finite-Elemente-Methode (FEM) berechnet und mittels Kraft-Messungen überprüft. Damit steht ein verifiziertes Werkzeug zur Verfügung, mit welchem die Eigenschaften des Tastsystems, beispielsweise dessen Steifigkeiten, an vorgegebene Spezifikationen angepasst werden können. So werden verschiedene Varianten des Tastsystems vorgestellt, die für einen Einsatz auf (Mikro-) Koordinatenmessgeräten oder Werkzeugmaschinen angepasst sind. Die geometrische Überprüfung des Tastsystems umfasst die Bestimmung des Linearitätsfehlers in Antastrichtung, die maximale Antastabweichung, die Wiederholgenauigkeit sowie den Einfluss der Umgebungsbedingunge

Multi-Beam Strategies for the Optimization of the Selective Laser Melting Process

The additive manufacturing of metal parts is of increasing importance for various industry sectors, but processes like selective laser melting are still lacking of robustness especially in the case of hard to process materials. The local adjustment of temperature fields around the melt pool seems promising to decrease melt pool and stress related defects because the boundary conditions can be tailored to positively influence the melt pool dynamics and lifetime as well as the temperature gradients which are the main reason for distortion and cracking. Therefore a selective laser melting laboratory machine was built up which features two independent lasers and beam deflection units which are adapted to synchronization. To discuss the usability of different synchronized multi-beam strategies for further process improvement, computational and experimental evaluations are used to investigate the strategies‘ influences on the process dynamics of the selective laser melting process.Mechanical Engineerin

A new method for the characterisation of rounded cutting edges

The influence of the cutting edge micro geometry on cutting process and on tool performance is subject of several research projects. Recently published papers focus on optimising the cutting edge rounding. The results are partly inconsistent. Unfortunately, no international standard yet exists to properly describe the cutting edge micro geometry. This is seen as the root cause for detected discrepancies. To develop a common understanding for the influence of rounded cutting edges, it is indispensable to use the same basis to characterise the edge profile. This paper gives a review on existing characterisation methods, analyses the difficulties in their application and discusses different modelling ideas to describe the cutting edge profile. Based hereon, a new algorithm and geometrical parameterisation of the cutting edge is proposed, which reduces uncertainties and difficulties in the application of currently available methods. The proposed method considers measurement uncertainties and is robust against form errors and creates thus the basis required for the study of the influence of rounded cutting edge

Influence of cutting edge radius on surface integrity and burr formation in milling titanium

The influence of the cutting edge micro geometry on cutting process and on tool performance is subject to several research projects. Recently, published papers mainly focus on the cutting edge rounding and its influence on tool life and cutting forces. For applications even more important, however, is the influence of the cutting edge radius on the integrity of the machined part. Especially for titanium, which is used in environments requiring high mechanical integrity, the information about the dependency of surface integrity on cutting edge geometry is important. This paper therefore studies the influence of the cutting edge radius on surface integrity in terms of residual stress, micro hardness, surface roughness and optical characterisation of the surface and near surface area in up and down milling of the titanium alloy Ti-6Al-4V. Moreover, the influence of the cutting edge radius on burr formation is analysed. The experiments show that residual stresses increase with the cutting edge radius especially in up milling, whereas the influence in down milling is less pronounced. The influence of the cutting edge radius on surface roughness is non-uniform. The formation of burr increases with increasing cutting edge radius, and is thus in agreement with the residual stress test

On-machine wire electrical discharge dressing (WEDD) of metal-bonded grinding wheels

Metal-bonded diamond wheels, due to its strong grain retention and thermal conductivity properties, are generally used for grinding difficult-to-cut materials, such as high-performance ceramics. On the other hand, the poor dressability of this type of bond limits its application. This study aims to evaluate the use of a wire electrical discharge machining (EDM) principle for truing and dressing metal-bonded grinding wheels. Through the EDM process, the electrically conductive grinding bond is eroded, so that grain protrusion can be generated. For evaluating this dressing process, a wire electrical discharge dressing unit was designed, manufactured, and integrated into a universal cylindrical grinding machine. The dressing process is carried out using the grinding oil also as dielectric fluid. High material removal rates were achieved. Cylindrical plunge grinding tests on silicon nitride workpieces indicated that in comparison to conventionally dressed wheels, smaller cutting forces and wheel wear are achieved by using EDM-dressed grinding wheel

Failure mechanisms and cutting characteristics of brazed single diamond grains

The knowledge about the cutting characteristics and the critical loading of brazed diamonds is essential for a safe and economic application of engineered grinding tools. Scratch tests were performed with single grains. The experiments were conducted with standard polyhedral diamond grains of different sizes, ranging from 300 to 850μm, brazed with an Ag-Cu-based and a Cu-Sn-based active filler alloy onto a steel pin. Two failure mechanisms were revealed, namely "grain pullout” and "grain fracture”. Large grits mainly fail by grain fracture, whereas the smaller ones were mostly pulled out. This trend is supported by a simple mechanical model. The critical values, i.e. cutting force/scratch area, for grain fracture and grain pullout show a decrease with bigger grit size. Scratches are also analysed in terms of cutting characteristics. The dependency of the cutting and the normal force on the scratch area can be described by a power law with powers ranging between about 0.2 and 0.7, respectively. The measured cutting forces strongly depend on the rake angle, which was tested for −19.5° and −35.3