Blasting Erosion Arc Machining Research Articles

Observation and modeling research of high-velocity flushing effect on the performance of BEAM

Blasting erosion arc machining (BEAM) is a novel high efficiency electrical erosion process, which is characterized by a powerful multi-hole inner flushing. In order to study the influence of the high-velocity flushing on the performance of BEAM, a single discharge experiment is carried out on a specially designed observation apparatus, and the phenomena that occurred during the discharge is observed using a high-speed video camera. During the discharge process, a spray cloud of the removed debris near the downstream side of the discharging point is captured by the camera. Tail shaped crater and erosion-corrosion features are also found on the workpiece and electrode surfaces, respectively. These observed phenomena imply that the high-velocity flushing can greatly improve the melting metal removal from the molten pool thereby improving the material removal rate (MRR). For purpose of exploring the mechanism behind, the flow field and pressure distribution of the high-velocity flushing are analyzed by using computational fluid dynamic (CFD) method. The analyzed results indicate that a low-pressure suction effect exists on the downstream side of the electrodes. With the help of the low-pressure suction effect, the high-velocity flushing can continuously take the molten metal out of the molten pool during the discharge, resulting in the reduction of the overheating of the molten metal and improve the efficiency of the discharging energy. Thereby, the work in this paper helps to explain why the high-velocity flushing can markedly promote the material removal rate.

Influence of flushing holes on the machining performance of blasting erosion arc machining

Blasting erosion arc machining is a novel electrical erosion process depending on the hydrodynamic arc-breaking mechanism to achieve a reliable high-efficiency machining. In blasting erosion arc machining, the high-velocity fluid field in the discharging gap is the precondition of the mechanism to control arc plasma to efficiently remove workpiece material. Therefore, this study mainly investigates the influence of flushing holes on the fluid field distribution directly and on the machining performance indirectly. Three multi-hole solid electrodes with different types of flushing holes are designed out according to the distributing principle. The influence of their flushing holes on the fluid field is conducted by a comparison fluid simulation which demonstrates that the electrode with flushing-hole diameters decreasing gradually from the inner to the outer in the radial direction attains the best flushing velocity distribution on the workpiece surface. Furthermore, the influence of their flushing holes on the blasting erosion arc machining performance is investigated by a comparison machining experiment in order to verify the comparison results of fluid field simulation. The experimental results illustrate that these electrodes have very different machining performance when machining nickel-based high-temperature alloy GH4169 (similar to Inconel 718) under the conditions of same discharge peak current and flushing inlet pressure. The electrode with the best flushing velocity distribution rather than with the highest velocity at a particular point achieves the best machining performance of the highest material removal rate, the least relative tool wear ratio and the least surface roughness (Ra), indicating an optimized design of flushing holes in the multi-hole solid electrode.

Study on blasting erosion arc machining of Ti–6Al–4V alloy

Blasting erosion arc machining (BEAM) was applied to improve the machining efficiency of Ti–6Al–4V alloy. 5-factor, 2-level fractional factorial experiment was firstly employed to find out the main factors for MRR (material removal rate). According to the results of fractional factorial experiment, 3-factor, 2-level full factorial experiment was conducted to find out the relationship between machining performance and the main factors (peak current, pulse duration, and pulse interval) under the negative electrode machining. Results revealed that when peak current was 500 A and pulse duration was 8 ms, MRR could achieve 16,800 mm3/min, which means the specific energy efficiency was 33.6 mm3/(A · min). Then, MRR was optimized base on MATLAB optimization toolbox and could reach 20,100 mm3/min when adopting the optimized parameters (peak current 600 A, pulse duration 8.8 ms, and pulse interval 3.0 ms). Although TWR (tool wear ratio) can be effected by the machining parameters, it appeared to be stable (around 3 ± 1 %). Besides, the polarity effect was also studied, and flow field simulations were employed to illustrate the influence of feeding direction on the surface roughness. In addition, the machined surface was analyzed by utilizing SEM, EDS, XRD, etc. Results of the surface analysis disclosed that the oxygen content in the negative electrode machined surface was obviously higher than that in the positive electrode machined surface. Since the positive electrode machined surface was much smoother, it can be used to improve the surface quality while the negative electrode machining is suitable for the bulk material removal with high energy. Finally, a Ti–6Al–4V turbine blade sample was machined to demonstrate the feasibility of high efficiency BEAM in difficult-to-cut material processing.

Machining characteristics of nickel-based alloy with positive polarity blasting erosion arc machining

A nickel-based high-temperature alloy widely used in aerospace engines is a typical difficult-to-cut material by conventional machining processes due to its high-temperature mechanical strength and toughness. Blasting erosion arc machining (BEAM), a new type of electrical discharge machining (EDM) method, is capable of removing such materials with a very high material removal rate and a low tool wear ratio. This paper presents experimental investigations in machining characteristics and machined surface integrity of the nickel-based alloy GH4169 (similar to Inconel718) by positive polarity blasting erosion arc machining (positive BEAM). The test results imply a possibility to improve the surface integrity with positive BEAM compared with a regular negative one. In this work, a three-factor, three-level machining performance experiment was carried out to examine the effects of the machining parameters such as discharge peak current, flushing inlet pressure, and pulse duration on the machining performances of material removal rate, tool wear ratio, and surface roughness. The experimental results show that positive BEAM is capable of greatly improving the machined surface integrity. The surface roughness decreased from 274 μm (under negative polarity BEAM) down to 31 μm (under positive polarity BEAM). Additionally, fewer micro-cracks and a thinner heat-affected zone on the workpiece surface can be observed. It also reveals that by optimizing the combination of the negative and the positive BEAM, favorable machining performances of high material removal rate and finer surface roughness are possible. By utilizing the polarity effects, the machining allowance for the subsequent semi-finishing processes such as cutting can be further reduced.

Influence of polarity on the performance of Blasting Erosion Arc Machining

Blasting Erosion Arc Machining (BEAM) is proposed to achieve high-efficiency machining for difficult-to-cut materials such as high-temperature alloys. By creatively controlling the arc plasma with the mechanism named hydrodynamic arc breaking, BEAM can remove bulk material with a high material removal rate (MRR). However, the BEAM generated surface is rough and requires additional post processing. In order to improve the resulting surface quality, positive electrode polarity BEAM was performed by using graphite bundled electrode to machine AISI D2 steel workpiece in this study. Experimental results demonstrate that compared with negative electrode BEAM, machining with positive polarity achieves a better surface quality with less MRR and high relative tool wear ratio (TWR). The explanation of the differences can be attributed to the performance of arc plasma resulting from the variation of the flushing velocity in the discharge gap. Therefore, it is possible to machine with high efficiency and a better control of the profile and surface quality of the workpiece by combining negative and positive (N-P) BEAM processes together.

Study of Machining Characteristics of Blasting Erosion Arc Machining

Study of Machining Characteristics of Blasting Erosion Arc Machining

Flow Field Simulation and Machining Experiment of Flank Milling Blasting Erosion Arc Machining

Flow Field Simulation and Machining Experiment of Flank Milling Blasting Erosion Arc Machining

A Novel High Efficiency Electrical Erosion Process – Blasting Erosion Arc Machining

A novel low cost, high efficiency material removal process namely the Blasting Erosion Arc Machining (BEAM) is proposed and implemented to perform bulk removing of alloys including the difficult-to-cut materials. Compared with conventional EDM process, the BEAM process erodes the work piece materials with electrical arcing instead of sparking.The most critical enabling mechanism of BEAM is how to make the arcing plasma column break off, and resulting in a consequent blast effect, by which the molten material is blown off from the molten pool efficiently. In order to avoid continuous and steady arcing, a strong multi-hole inner flushing is a prerequisite for the BEAM process. During BEAM, the high velocity flushing induces a strong hydrodynamic force into the gap, which distorts, elongates or even breaks the arcing plasma column. During the arc breaking process, an extremely strong blasting will blow off the molten material explosively. This arc breaking mechanism is named hydrodynamic arc breaking mechanism and it is the principle of BEAM process.The preliminary experiments demonstrated the material removal rate of the BEAM process is extremely higher than that of traditional EDM or even the milling process. For example, the MRR of BEAM of Inconel718 exceeds 11,300/min as well as the tool wear ratio is lower than 1%. Obviously, BEAM is a promising process in the high efficiency machining of the difficult-to-cut materials. Besides, it is also an environmentally friendly machining process because the working fluid is water-based dielectric rather than hydrocarbon dielectric oil.