The International Journal of Advanced Manufacturing Technology

Jia, Zhi-xin; Li, Ji-qiang; Liu, Li-Jun; Zhou, Hong

doi: 10.1007/s00170-011-3420-5pmid: N/A

Die service life improvement is an important problem in high-pressure die-casting industry. Experiment results on die steel shows that biomimetic laser-remelting process provides a promising method to improve the service life of die-casting die. A casting with uneven wall thickness was selected and problems existing in die-casting production were analyzed. The corresponding die-casting die was processed by biomimetic laser-remelting process. The application result indicates that the service life of the die processed by biomimetic laser-remelting process has been increased from 12,000 to 28,000 shots, which is more than twice that of no processed one under real high-pressure die-casting conditions. The application of laser-remelting process provides desirable micro-structural changes in biomimetic units, which induces the intensified particles effect for improving the service life.

Zeilmann, Rodrigo; Nicola, Gerson; Vacaro, Tiago; Teixeira, Cleiton; Heiler, Roland

doi: 10.1007/s00170-011-3401-8pmid: N/A

The machining of hardened steel is becoming increasingly important in manufacturing processes. Machined parts made with hardened steel are often subjected to high service demands, which require great resistance and quality. The machining of this material submits the tools to high mechanical and thermal loads, which increases the tool wear and affects the surface integrity of the part. In that context, this work presents a study of drilling of AISI P20 steel with carbide tools, analyzing the effects on the process caused by the reduction of cutting fluid supply and its relation with the tool wear and the surface integrity of the piece. The major problem observed in the tests was a difficulty for chips to flow through the drill flute, compromising their expulsion from the hole. After a careful analysis, a different machining strategy was adopted to solve the problem.

Lee, Seok; Nestler, Andreas

doi: 10.1007/s00170-011-3431-2pmid: N/A

In this paper, an efficient methodology to generate a virtual workpiece (VWP) is presented. VWP is a workpiece in a virtual environment in which the geometric, kinematic, and thermo-mechanical effects of the process and resources can be reflected. VWP encompasses not only the macro-information corresponding to the shape of the “virtually” machined intermediate workpiece, but also the micro-information, such as the surface roughness, scallop heights, chatter mark, etc. To represent VWP, swept volume (SV) of geometrically defined cutters is generated first by envelope profiles which are calculated by the intersection of the Tool map with the Contact map of the tool moving direction. Then SV is tessellated to conduct elementary 1D Boolean subtraction of SVs from the IPW. The Boolean subtraction is realized by means of an efficient ray-triangle intersection test using Barycentric coordinates. Finally, VWP is reconstructed as a triangular mesh (STL, stereolithography data format) from the orthogonal triple-dexel model (TDM) which predicts machined surface quality, such as surface roughness, gouging and sharp edges and is reused for further operations, e.g., tool path generation, simulation and geometric metrology, etc. To demonstrate the validity of VWP modeling, several material removal processes, e.g., milling and micro-EDM operations, have been tested and the proposed approach has been proven to be applicable to enhance the quality of NC simulation and verification.

Li, Anhai; Zhao, Jun; Luo, Hanbing; Pei, Zhiqiang; Wang, Zeming

doi: 10.1007/s00170-011-3408-1pmid: N/A

This paper presents a detailed analysis of tool failure progression through an experimental study of high speed milling of Ti-6Al-4V alloy with CVD (Ti(C, N)-Al2O3)-coated carbide tools. The progressive tool failure characteristics under a variety of different cutting conditions were investigated. Cutting forces components and transient infrared temperature during the machining processes have been measured along with corresponding progressive tool wear when milling using coated carbide inserts under dry machining conditions. Optical microscope and scanning electron microscopic analysis results clearly show the different dominant wear regions at different stages of machining with coated carbide tools. The experimental results demonstrate that the cutting forces and the cutting temperature produced during the machining process showed an increasing trend with the tool failure progression, which in turns accelerated the tool wear progression and caused the change of the tool failure mechanisms. Furthermore, the progressive tool failure mechanisms were analyzed qualitatively. The cutting speed was correlated with progressive tool failure mechanisms, and the different conditions of friction and normal stresses caused by different cutting force and cutting temperature under different cutting speeds resulted in the varieties of progressive tool failure mechanisms.

Jaffery, Syed; Mativenga, Paul

doi: 10.1007/s00170-011-3427-ypmid: N/A

Titanium alloys are materials of choice for a wide range of applications. Their high strength and low density make them suitable for aerospace applications. Titanium-based alloys also exhibit excellent corrosion resistance and are bio-compatible, making them suitable for prosthetic applications like orthopedic transplants. The reactivity as well as heat resistance of titanium-based alloys, however, renders them difficult to machine. Based on previous research involving the development of a wear map for Ti-6Al-4V alloy, this research aims to identify the wear mechanisms associated with tool deterioration across different regions of the wear map. The characterization of wear mechanisms with respect to machining conditions and tool wear rate would ultimately help in the development of suitable tool coatings for machining titanium-based alloys.

Liewald, M.; Wagner, S.; Becker, D.; Ziebert, C.; Pesch, P.; Kolozsvári, S.

doi: 10.1007/s00170-011-3412-5pmid: N/A

Resistance to wear, and therefore the lifetime of forming tools, can be increased by surface functionalisation using novel, multifunctional coatings. Thereby, the tribological requirements on the coating are an essential factor. Within the scope of the research work presented here, tribological examinations were carried out on a metastable vanadium aluminium nitride (VAlN) tool coating when drawing the high-strength sheet metal material DP 800. It was shown that the wear of the VAlN tool coating can already be determined at stable frictional behaviour (μ < 0.085). The wear analysis was carried out considering the topography and change in hardness of the tool surface during the drawing path of 110,000 mm under a contact stress of 150 MPa.

Ramezani, Maziar; Ripin, Zaidi

doi: 10.1007/s00170-011-3418-zpmid: N/A

Deep drawing of sheet metals using Maslennikov’s technique has been analyzed by analytical and finite element simulation approaches. A new friction model based on local contact conditions has been used in the finite element (FE) simulations of the process. Compared to traditional Coulomb friction model, the results of FE simulations with the new friction model show good correlation with analytical calculations. The effects of key process parameters such as rubber ring thickness, ring inner diameter, die hole diameter, and die profile radius on the results have been investigated. The results showed that very deep cups without thinning in the side wall portion can be achieved with this process. Based on the results of FE analysis, it was found that the maximum drawing ratio can be achieved by adopting a combination of process parameters which correspond to points nearest to the fracture limit.

Xu, Gang; Yang, Zhi-tao; Long, Guo-dong

doi: 10.1007/s00170-011-3425-0pmid: N/A

Determining optimal process parameter settings critically influences productivity, quality, and cost of production in the plastic injection molding industry. Selecting the proper process conditions for the injection molding process is treated as a multi-objective optimization problem, where different objectives, such as minimizing product weight, volumetric shrinkage, or flash present trade-off behaviors. As such, various optima may exist in the objective space. This paper presents the development of an experiment-based optimization system for the process parameter optimization of multiple-input multiple-output plastic injection molding process. The development integrates Taguchi’s parameter design method, neural networks based on PSO (PSONN model), multi-objective particle swarm optimization algorithm, engineering optimization concepts, and automatically search for the Pareto-optimal solutions for different objectives. According to the illustrative applications, the research results indicate that the proposed approach can effectively help engineers identify optimal process conditions and achieve competitive advantages of product quality and costs.

Nguyen, Minh; Rahman, Mustafizur; Wong, Yoke

doi: 10.1007/s00170-011-3397-0pmid: N/A

Deionized water has been used as dielectric fluid for micro-electrical discharge machining (micro-EDM) because it gives higher material removal rate and lower tool wear than hydrocarbon oil. Moreover, it is a relatively low-cost and eco-friendly substance. Therefore, deionized water tends to be more favorable for micro-EDM. However, it causes weak electrochemical reaction during micro-EDM due to its slight conductivity. This leads to the unanticipated additional material removal from the workpiece which affects the machining shape and quality. The study in this paper aims to suppress the electrochemical reaction in die-sinking micro-EDM using deionized water by employing short voltage pulse. Experiments were carried out to fabricate micro-holes using the developed nanosecond pulse circuit. Different pulse parameters were applied to identify the main factor affecting the electrochemical reaction rate. Machining gap was found to be thinner and workpiece surface adjacent to the rim of micro-holes were found to be free of defects caused by material dissolution when pulse duration reached a critical value. Moreover, the influence of pulse parameters on material removal rate and machined shape was also investigated. Besides, energy-dispersive X-ray spectroscopy analysis showed that the machined surface using deionized water was less affected from material migration during micro-EDM process in comparison to hydrocarbon oil.

Wang, Fude

doi: 10.1007/s00170-011-3423-2pmid: N/A

Tensile mechanical properties of selective laser-melted Hastelloy® X alloy in as-deposited condition and after hot isostatic pressing (HIP) have been studied at ambient and elevated temperatures. Room temperature four-point bending and tension–tension fatigue properties have also been investigated in as-deposited condition and after HIP. The yield strength of the as-deposited selective laser-melted Hastelloy® X specimen is higher than the heat-treated (hot forged) samples. The ultimate strength is also higher than that of the hot forged samples while the elongation property is lower. This can be attributed to its ultrafine microstructure caused by rapid solidification, which is characteristic of the selective laser melting process. It is also found that the mechanical properties (tensile and fatigue) do not vary with samples built in different bed locations.