Molecular Dynamics Simulation on Cutting Mechanism in the Hybrid Machining Process of Single-Crystal Silicon

In this paper, molecular dynamics simulations are carried out to investigate the cutting mechanism during the hybrid machining process combined the thermal and vibration assistants. A modified cutting model is applied to study the material removal behavior and subsurface damage formation in one vibration cycle. The results indicate that during the hybrid machining process, the dominant material removal mechanism could transform from extrusion to shearing in a single vibration cycle. With an increase of the cutting temperature, the generation and propagation of cracks are effectively suppressed while the swelling appears when the dominant material removal mechanism becomes shearing. The formation mechanism of the subsurface damage in one vibration cycle can be distinct according to the stress distribution. Moreover, the generation of the vacancies in workpiece becomes apparent with increasing temperature, which is an important phenomenon in hybrid machining process.

Optimization of turn-milling process in roughing and finishing regimes: Trade-off between productivity, cutting force and surface integrity

Turn-milling is a hybrid machining process which used benefits of interrupted cutting for proceeding of round bars. However, number of controllable parameters in the hybrid process is numerous that makes optimizing the process complicated. In the present study, an optimization work has been proposed to investigate the trade-off between production rate and cutting force in roughing regime as well surface roughness and tensile residual stress in finishing regime. Number of 43 experiments based on response surface methodology was designed and carried out to gather required data for development of quadratic empirical models. Then, the adequacy and importance of process factors were analyzed using analysis of variances. Finally, desirability function was used to optimize the process in rough and finish machining regimes. The obtained results showed that selection of eccentricity and cutter speed at their maximum working range can effectively enhance the quality characteristics in both the roughing and finishing regimes.

Optimization of Process Parameters in Micro-Electrochemical Discharge Machining by Using Grey Relational Analysis

Micro-electrochemical discharge machining is hybrid machining process which is based on combined principle of electro discharge machining and electro chemical machining. It is suitable for machining of both conductive as well as non-conductive materials. In this study a micro hole drilled on Ti-6Al-4V as work piece by varying machining parameters like electrolyte concentration, voltage and duty factor at three different levels. Orthogonal array L9 considered for design and performing experiments. The Grey relation analysis (GRA) was performed to optimize the output parameters i.e. material removal rate (MRR) and hole tapper angle (HTA). The result reveals that voltage was the most significant factor for both MRR and HTA followed by electrolyte concentration and duty factor. The maximum MRR and minimum taper angle are 1.50 mg/min and 0.98 ° obtained respectively. The GRA show optimal machining parameters at electrolyte concentration 3M, voltage 40 V and duty factor 25% respectively.

Generation and characterization of ultra-precision compound freeform surfaces

Compound freeform surfaces are widely used in bionic and optical applications. The manufacturing and measurement of such surfaces are challenging due to the complex geometry with multi-scale features in a high precision level with sub-micrometer form accuracy and nanometer surface finish. This article presents a study of ultra-precision machining and characterization of compound freeform surfaces. A hybrid machining process by combining slow slide servo and fast tool servo is proposed to machine compound freeform surfaces. The machining process for this hybrid tool servo is explained, and tool path generation is presented. Then, a normal template-based matching and characterization method is proposed to evaluate such compound freeform surfaces. Experimental studies are undertaken to machine a compound freeform surface using the proposed method based on a four-axis ultra-precision machine tool. The machined compound freeform surface is also measured and characterized by the proposed analysis and characterization method. The experimental results are presented, and the machining errors for compound freeform surfaces are also discussed.

Experimental Study and Parameter Optimization of Hybrid Electrical Discharge Machining

Hard materials cannot be machined effectively by the individual machining process. In order to machine workpiece made from hard and stiff materials effectively a concept of Hybrid machining process (HMP) is originated. The HMP is an integration of two or more machining process to get the advantage of each individual process. HMP is used to machine This study focuses on evolving a novel process using both oil and gas as dielectrics to analyse the effect on tool wear rate (TWR) and material removal rate (MRR). The flow of compressed gas through eccentric-hole rotating tool improved the debris removal from inter-electrode gap, hence it improve the flushing competence of the machining process. In this experimental investigation, the workpiece material is Al-20% SiC metal matrix composite (MMC) and the electrode material is copper. The experiments were conducted following the Taguchi method of design experiments. The effect of various machining parameters on MRR and TWR has been studied. The optimization of process parameter has also been done. The results of TWR and MRR are analysed using S/N ratio, ANOVA and main effect plots. The experimental results, revels that discharge current, gap voltage and pulse on time significantly affected MRR, and TWR. The experimental inference reveal that provision of compressed air through eccentric hole rotary tool has a positive effect on machinability of electrical discharge machining (EDM) process.