Electrical discharge machining of ceramic nanocomposites: sublimation phenomena and adaptive control

In present, five-axis numerical control (NC) machining center is used to process blisk, and the technology of plunge-milling and side-milling are widely adopted, which results in lower processing efficiency and high total cost. In the present study, first, a new machining technology of blisk is put forward, which is known as multi-milling, namely, disc-milling is used to remove the large margin of blisk’s channel, plunge-milling can expand the size of groove, further forming the surface of channel, and the corner and angle of the channel can be eliminated by side-milling. Second, with one-stage fan blisk of a certain type aircraft engine as an example, the processing efficiency of three different technologies (multi-milling, plunge-milling+side-milling, and side-milling) are studied by means of UG (Unigraphics NX) software. Third, based on the technology of multi-milling, the specific structure of multi-milling machine tool is designed. Last, the verification test is conducted, test results show that the processing efficiency of blisk can be enhanced drastically, finish cost can be reduced greatly with the multi-milling machine tool, which can give a great push to the development of aviation industry.

Compound efficient and powerful milling machine tool of blisk

The increasing adoption of exotic and hard to cut materials in high-end applications makes electric discharge machining (EDM) process more relevant than ever. In particular, wire EDM variant (WEDM) deserves attention due to its ability to cut the workpiece's surroundings without completely evaporating the unused portion of the rare and expensive exotic materials. However, WEDM is a stochastic process that still lacks complete mathematical models and is driven by a myriad of parameters that will make its control a complex task. In WEDM, whenever the wire is fed too fast, the process will be interrupted not only by short circuits, but the wire electrode is most likely to break, jeopardising process efficiency in many ways. Currently, most of the literature has focused efficiency efforts in proposing a trade-off among parameters without a complete correlation with servo and control strategies. Therefore, this review aims to find and analyse the state-of-the-art approaches for controlling the Wire EDM process. A systematic literature review is conducted to identify and provide an adequate understanding of the best control strategies, fundamental parameters, and role. With no previous studies found, the present review focuses exclusively on servo control. First, it provides a comprehensive literature framework covering four decades, to next glimpse future developments of WEDM control strategies. Potential adoption of the findings can result in a deeper understanding of control variables and a broader and more efficient concept for WEDM servo feed control.

Comprehensive servo control strategies for flexible and high-efficient wire electric discharge machining. A systematic review

Wire Electrical Discharge Machining (WEDM) is an electrothermal non-traditional machining process used for machining electrically conductive materials that are difficult to machine. Material removal in WEDM is by means of spark erosion. WEDM is proven to be the alternative for producing complex parts with higher degree of dimensional accuracy and better surface finish. Over the years, a significant amount of research was globally carried out to explore the WEDM process capability. This paper aims to explore the research work carried on parametric influence of WEDM process variables on various output performance measures. The paper also highlights various modelling techniques to predict optimal machining conditions and explore the feasibility of applying WEDM process to machine advanced materials. Combined technology that benefits from the virtues of WEDM and conventional method is also highlighted in this paper. The final section discusses the development and possible research trend in WEDM process.

/pdf/a-progress-review-in-wire-electrical-discharge-machining-3sh02q4c8k.pdf

A progress review in wire electrical discharge machining process

Exotic materials play a key role in high-end applications. Thus, Wire Electric Discharge Machining (WEDM) stands out due to superior surface roughness and high precision. Currently, WEDM is found in rigid bed-based CNC machines constraining the workpieces in geometry and size. Parallelly, the stochastic nature of WEDM and the lack of complete mathematical models make it complex to control. As a result, whenever the servo feed becomes faster than the material removal rate, short circuits and wire break occur. On the other hand, traditional machining using six-axis industrial robots (IR) have been extensively investigated for cost efficiency, improved envelope and virtually unlimited axis combination. However, the IR design offers low stiffness, facing severe vibrations in machining hard-to-cut materials, resulting in low accuracy, poor finishing, and lack of repeatability. Thus, IRs are not comparable to CNC. The present research reviews the ideal servo control strategies for a synergistic combination of a novel machining technic of WEDM working with an IR as the servo. Employing a theoretical analysis followed by a series of simulations, it is demonstrated how the combination can be successfully controlled by frequency modulation, delivering a robotic process able to machine any hard-to-cut conductive material yet free of vibration.

Servo Control Strategies for Vibration-Control in Robotic Wire EDM Machining

High-speed wire electrical discharge machining (WEDM-HS) of materials of super-high thickness (more than 1000 mm) is a challenging problem. First, sufficient energy is required to maintain the inter-electrode normal discharge. Next, there must be adequate inter-electrode dielectric fluid. Third, in order to generate a smooth cut surface, it is necessary to suppress the vibration of the wire electrode to reduce vibration lines on the cutting surface. To better understand these challenges, the energy and the flow of the medium between two electrodes were analyzed, allowing the establishment of a relevant model. The results indicated that for super-high-thickness machining, the pulse energy must be adequate to compensate for the energy consumed in the molybdenum wire and inter-electrode working liquid. In addition, the running speed of the wire electrode should be improved to ensure that there is a sufficiently high flow rate of the dielectric fluid. The servo control mode of the existing machine tools and dielectric fluid were improved and then a process experiment was performed. The experimental results show that the process can be carried out efficiently and stably and the workpiece surface can be cut smoothly using the improved working liquid and servo control mode.

Super-high-thickness high-speed wire electrical discharge machining

To further improve the technological indexes of high-speed wire electrical discharge machining (HS-WEDM) under conditions of high energy and high thickness while also solving the problem of an absent liquid medium and unsteady processing in the inter-electrode gap, a new type of stranded wire electrode used in HS-WEDM was designed to enhance the flow of the liquid medium and debris removal during the machining process. First, a simulation model of the inter-electrode gap flow field is established; the simulation analysis indicates that the capacity of carrying liquid medium with a stranded wire electrode is approximately 65% higher than with a normal wire electrode at a high workpiece thickness of 400 mm. Next, the special discharge characteristic of stranded wire electrode is summarized from the two aspects of effective discharge area and high-thickness workpiece. Third, a comparative experiment on cutting a high-thickness workpiece at high energy demonstrates a greater threshold of stable cutting speed (over 250 mm2/min) and stable material removal rate (142 mm3/min) at an average cutting current of 18 A with a stranded wire electrode, whereas the maximum cutting speed (155 mm2/min) at an average cutting current of 8 A with a normal wire electrode. Experiments prove that using a stranded wire electrode can significantly increase cutting speed and improve processing stability in the electrode gap under high-energy and high-thickness conditions.

Laijiu Fang

Papers

Super-high-thickness high-speed wire electrical discharge machining

Study on high-efficiency cutting of high-thickness workpiece with stranded wire electrode in high-speed wire electrical discharge machining