CN102091839B - Bunched electrode high-speed discharge processing method - Google Patents

Abstract

A cluster electrode high-speed discharge machining method in the field of arc discharge machining technology. The cluster electrode is fixedly connected to the spindle of a machine tool, and the end face of the cluster electrode is directly opposite to a workpiece to be processed on the machine tool workbench. The workpiece can be immersed in a water-based working fluid. In the water-based working fluid provided by the liquid supply system, the water-based working fluid supply system, the cluster electrode and the machine tool working fluid tank form a fluid circuit, and the discharge power supply, the cluster electrode, the water-based working fluid that has been broken down between the electrodes, and the The workpiece to be processed forms a current loop, and the water-based working fluid between the cluster electrode and the workpiece to be processed is circulated through the water-based working fluid supply system. DC current or pulse current forms a short arc discharge, thereby realizing high-speed discharge machining. The invention utilizes cluster electrodes to realize enhanced high-pressure, large-flow porous internal flushing, uses fluid dynamic arc-breaking mechanism to ensure short-arc discharge machining, and can simply, conveniently and economically realize the technological method of cluster electrode high-speed discharge machining, especially for curved surfaces, Cavity machining.

Description

Cluster Electrode High-Speed EDM Method

technical field

The invention relates to a processing method in the technical field which adopts a fluid dynamic arc breaking mechanism to realize short arc discharge and aims at material removal, in particular to a high-speed discharge processing method for cluster electrodes.

Background technique

Realizing the high-speed and high-efficiency processing of high-hardness, high-toughness, high-strength and high-brittleness materials has always been the goal in the field of material processing. EDM has the advantages of small macro force, non-contact processing, etc., and the processing process is not affected by the mechanical properties of materials, thus providing an effective method for processing difficult-to-cut materials. EDM is a discharge machining method that realizes thermal erosion of materials by spark discharge between electrodes. Due to the nature of spark discharge, it is difficult to achieve high-efficiency machining with high discharge energy. Unlike spark discharge, arc discharge is an alternative form of discharge that can conduct discharge currents up to tens of thousands of amperes, allowing for more efficient material removal potential. Inspired by EDM, and with people's control over the characteristics of arc discharge, short arc discharge is gradually used in the field of material processing, and combined with other technologies to form a variety of processing methods with high-efficiency processing capabilities.

In arc discharge machining, if the discharge process cannot be terminated in time, that is, the arc is broken, a continuous steady-state arc discharge will be formed, resulting in the transformation of the machining process for the purpose of material erosion into a heating process of burnt materials. Therefore, the key to efficient EDM with short arc is an effective arc breaking mechanism. After searching the prior art, it is found that the arc breaking mechanism adopted in the current short arc discharge machining is realized by the mechanical sliding movement of the electrode relative to the surface of the workpiece.

After searching the prior art, it is found that Chinese Patent Document No. CN 87106421A discloses a processing method and equipment combining short-arc discharge and mechanical grinding, and further discloses short-arc electric processing equipment in Chinese Patent Document No. CN 1061175A , The above-mentioned technology involves a process method called "electromelting explosion processing", that is, a combined processing method that uses a combination of disc tool electrode rotational movement and short arc discharge to achieve metal melting and removal. During the machining process, the relative movement between the tool and the workpiece is realized through the rotation of the disk tool electrode, so that the discharge arc is forced to be mechanically interrupted to realize efficient discharge machining. Determined by its principle, this method is mainly suitable for rough machining and grooving of outer circular parts such as rolls and grinding rolls.

In addition, the distributed arc electric erosion machining method disclosed in Chinese Patent Document No. CN 1693024A, and the method of high-efficiency discharge milling using simple hollow long electrodes disclosed in Chinese Patent Document No. CN1397399A, all involve an internal flushing liquid or A combined machining method combining multi-axis movement of the outer flushing tubular electrode and short arc discharge. This method is also based on the relative movement between the electrode and the workpiece to perform forced mechanical arc breaking of the discharge arc to realize processing. When this type of method is used, the forming process of the workpiece is similar to EDM. Simple electrodes are used to etch the workpiece material layer by layer through discharge to obtain three-dimensional shape processing. This method is suitable for complex curved surfaces with little curvature change. processing.

However, in the methods of short arc machining disclosed in the above technologies, the relative movement between the tool electrode and the workpiece is used to achieve forced mechanical arc breaking, which makes these machining methods using short arc discharge limited to a certain extent , such as the former method is mainly suitable for cylindrical processing. The latter two methods require the machine tool to have a three-axis or more CNC system.

Chinese Patent Document No. CN 1657208A describes a cluster electrode that can realize large-flow internal flushing for electric discharge machining. The beneficial effect of cluster electrodes is that the discretization of integral shaped electrodes can be aggregated from a large number of tubular or rod-shaped unit electrodes, so that the processing of shaped electrodes with complex contours and high processing costs is simplified. The combination of simple tubular or rod-shaped unit electrodes produced at low cost can greatly reduce the electrode cost and shorten the production time.

However, in the above technology, the cluster electrode is defined as a shaped electrode that is only used in the field of ordinary electric discharge machining, which greatly restricts the application range of the cluster electrode. Liquid energy and sufficient discharge energy can realize high-speed short-arc discharge machining different from EDM on a machine tool with a single-axis numerical control system.

Contents of the invention

The present invention aims at the above-mentioned deficiencies in the prior art, and provides a "high-speed electric discharge machining method with cluster electrodes", which utilizes cluster electrodes to realize enhanced high-pressure, large-flow porous internal flushing, and uses a hydrodynamic arc-breaking mechanism to ensure short-arc discharge machining. The technological method of high-speed electrical discharge machining of cluster electrodes can be realized simply, conveniently and economically, and the method is especially suitable for high-speed machining of complex curved surfaces and cavities.

The present invention is achieved through the following technical solutions. In the present invention, the cluster electrode is fixedly connected to the main shaft of the machine tool, and the processing end face of the cluster electrode is directly opposite to the workpiece to be processed on the machine tool table. The workpiece can be immersed in the water-based working fluid provided by the water-based working fluid supply system. Then the water-based working fluid supply system, the machine tool working fluid tank and the cluster electrode form a fluid circuit, and the discharge power supply, the cluster electrode, the workpiece and the water-based working fluid that has been broken down between the electrodes form a current loop, and the water-based working fluid is supplied through the water-based working fluid. The system circulates the water-based working fluid between the cluster electrode and the workpiece to be processed. The cluster electrode is connected to the negative pole of the discharge power supply, and the workpiece to be processed is connected to the positive pole of the discharge power supply. DC current or pulse current is applied through the discharge power supply to form a short arc discharge, thereby realizing High speed electrical discharge machining.

The discharge power supply refers to a DC power supply with a voltage value of 30V-60V and a peak current of 500A-10000A;

The discharge power supply refers to: providing a pulse power supply with a pulse width and a pulse interval ranging from 2 μs to 2000 μs, a peak voltage ranging from 30V to 60V, and a peak current ranging from 500A to 10000A, so as to realize electrical forced arc breaking.

The machine tool mentioned above refers to: a machine tool with at least a single spindle automatic servo feed and retract function;

The water-based working fluid can be cutting emulsion or tap water with a conductivity of 125-1250 μS/cm.

The cycle refers to: the water-based working fluid pump drives the water-based working fluid between the cluster electrode and the workpiece to flow at a pressure of 1.0MPa and above and a flow rate of 20L/min and above to achieve hydrodynamic arc breaking, Therefore, the short-arc high-speed discharge machining process with the purpose of material erosion rather than material heating and burning is guaranteed.

The beneficial effect of the present invention is that: material erosion is carried out by using short electric arc, which has a material removal ability much higher than that obtained by electric discharge machining; short electric arc machining is realized through a fluid dynamic arc breaking mechanism, and the machining process can adopt the spindle sinking type Processing requires simple movement of the machine tool. This simple spindle sinking processing method cannot be realized for the disclosed short-arc processing method introduced in the technical background; the processing has a wide range of applications, not only through simple The submerged machining realizes the machining of the cavity and the curved surface, and by expanding the movement function of the machine tool, the relative movement between the cluster electrode and the workpiece can also be achieved under the joint action of the fluid dynamic arc breaking mechanism and the forced mechanical arc breaking mechanism. Machining performance The multi-axis linkage short arc high-efficiency discharge machining process realizes the machining of cavity and curved surface.

Description of drawings

Figure 1 is a schematic diagram of cluster electrode high-speed EDM operation.

Fig. 2 is a schematic diagram of the process principle of cluster electrode high-speed electric discharge machining.

Fig. 3 is a schematic diagram of the arc shape and the discharge voltage and current waveform in the hydrodynamic arc breaking process.

Detailed ways

The embodiments of the present invention are described in detail below. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following implementation example.

As shown in Figure 1, the application environment of this embodiment includes: a cluster electrode 1, a workpiece to be processed 2, a machine tool 3, a water-based working fluid supply system 4, and a discharge power source 5, wherein: the cluster electrode 1 is fixedly connected to the spindle of the machine tool 3, The processing end face of the cluster electrode 1 is directly opposite to the workpiece 2 to be processed on the workbench of the machine tool 3. The workpiece can be immersed in the water-based working fluid provided by the water-based working fluid supply system 4. The water-based working fluid supply system 4 and The cluster electrode 1 and the working fluid tank of the machine tool 3 form a fluid circuit, and the discharge power supply 5, the cluster electrode 1, the water-based working fluid broken down between electrodes and the workpiece 2 to be processed form a current circuit.

The schematic diagram of the discharge erosion process under the hydrodynamic arc breaking mechanism in the water-based working fluid is shown in Figure 2. When a voltage is applied between the electrodes, the breakdown discharge will first occur at the position of the highest electric field strength between the electrodes (as shown in (a) ), and quickly form a discharge arc column A in a state of dynamic equilibrium between the cluster electrode 1 and the workpiece 2 to be processed, so as to realize the instantaneous heating and melting of the workpiece material and the explosive erosion of bubbles, as shown in (b). Under the hydrodynamic force F of the high-speed flowing water-based working fluid, the dynamic balance of the discharge arc column A is broken and shifted along the flow direction of the working fluid, thereby forming an elongated arc column B. Due to the increase in the actual discharge path length, The impedance of the arc column increases. When the arc column is elongated to a certain extent due to the offset, the discharge arc column is difficult to maintain and is pulled off to form a C state, so that the current arc discharge is terminated and the working fluid is deionized, as shown in the figure (c ), that is, hydrodynamic arc interruption is achieved, thereby ensuring a short arc discharge with strong material removal capability, rather than a conventional steady-state arc discharge that heats and burns the tool and workpiece material. At the same time, a new breakdown will be formed at another position with the highest electric field intensity between the electrodes, and a discharge arc column will be generated, repeating the previous hydrodynamic arc breaking process. By repeating this process continuously, the cluster electrode short arc high-speed discharge machining is formed.

Among them, the inter-electrode discharge voltage and current waveforms corresponding to the A, B, and C processes of hydrodynamic arc interruption are shown in Figure 3. As the discharge arc column is blown and elongated to present B state, the inter-electrode discharge maintenance voltage also rises correspondingly, and the discharge current decreases accordingly. When the arc column is blown off and presents C state, the discharge voltage returns to open circuit voltage, while the discharge current drops to zero.

The enhanced high pressure and large flow of flushing liquid brought by the porous structure of the cluster electrode also have the following three indispensable effects for high-speed electrical discharge machining:

First, high-efficiency removal: because the high-speed fluid can blow the liquid and gaseous metals in the discharge molten pool on the surface of the workpiece melted by the short arc discharge away from the surface of the workpiece, avoiding the re-solidification of a large amount of molten metal, thereby improving the material removal rate ;

Second, efficient chip removal: Since the high-speed fluid can take away the metal debris generated by high-speed discharge, it avoids frequent short circuits caused by a large amount of metal debris staying in the processing gap, ensuring continuous and stable processing;

Third, high-efficiency heat dissipation: a large amount of heat generated by short-arc discharge can be taken away by the high-speed flowing water-based working fluid through enhanced convective heat transfer, avoiding metallographic structures such as annealing of the processed surface caused by the temperature rise of the processed workpiece Changes, and the reduction of dimensional accuracy caused by thermal expansion and deformation.

Example 1

Using the machine tool 3 with only a single spindle automatic servo feed and retract function, the proper arc discharge gap between the cluster electrode 1 and the workpiece 2 to be processed is maintained through the feed of the spindle. The area of the end surface of the cluster electrode 1 is 500mm ² , and its material is graphite. The material of the workpiece 2 to be processed is titanium alloy (model TC4). Short arc processing is performed using the power parameters of peak voltage 50V, peak current 635A, pulse width 2000μs and pulse interval 200μs , the water-based working fluid is cutting emulsion, and the working fluid pressure provided by the flushing system is 1.5MPa and the flow rate is 25L/min. Under these processing conditions, the material removal rate of titanium alloy TC4 can be obtained by simple spindle sinking processing Up to 6844mm ³ /min, this processing speed is much higher than the maximum material removal rate that can be achieved by traditional EDM (under the processing conditions of peak current 127A, pulse width 24μs, pulse interval 100μs and flushing flow rate 2.5L/min , The maximum material removal rate of the cluster electrode EDM TC4 that has been obtained is below 150mm ³ /min).

Example 2

Change the workpiece material to fully verify the universal applicability of cluster electrode high-speed electric discharge machining to different materials. The workpiece material is selected as superalloy (GH4169), and other processing conditions in Example 1 are kept unchanged. The material removal rate of superalloy GH4169 is as high as 6350mm ³ /min.

Example 3

Selecting the workpiece material as carbon steel (S45C), keeping other processing conditions unchanged in Example 1, the material removal rate of carbon steel S45C is as high as 4320mm ³ /min.

Example 4

The processing efficiency is approximately proportional to the discharge current, but the higher the discharge current needs to be supplemented with a larger flushing flow rate, by increasing the peak current in Example 1 to 1000A, and supplemented with a larger flushing flow rate of 35L/min, maintaining Other processing conditions remain unchanged, the material removal rate of titanium alloy TC4 is as high as 10530mm ³ /min.

Example 5

Further increase the peak current in Example 1 to 2000A, supplemented with a larger flushing flow rate of 50L/min, and keep other processing conditions unchanged, the material removal rate of titanium alloy TC4 is as high as 19388mm ³ /min.

Claims (5)

1. a bundling electrode high rate discharge processing method is characterized in that, at first bundling electrode is fixedly connected with the main shaft of lathe; The bundling electrode end face is over against the pending workpiece that places on the platen; This workpiece is immersed in the water base working solution that water base working solution liquid-supplying system provides, and then water base working solution liquid-supplying system and bundling electrode and lathe work tank is formed fluid circuit, and discharge power supply, bundling electrode, breakdown water base working solution and the pending workpiece of interpolar are formed current loop; Through the water base working solution between water base working solution liquid-supplying system circulation bundling electrode and the pending workpiece; Bundling electrode connects the negative pole of discharge power supply, and pending workpiece connects the positive pole of discharge power supply, applies DC current or pulse current through discharge power supply; Form short arc discharge, thereby realize high rate discharge processing;

Described circulation is meant: the water base working solution that water base work liquid pump drives between bundling electrode and the pending workpiece flows the current interruption of realization fluid dynamic with the pressure more than the 1.0MPa, flow more than the 20L/min.

2. bundling electrode high rate discharge processing method according to claim 1 is characterized in that described discharge power supply is meant: magnitude of voltage is 30V-60V, and peak point current is the dc source of 500A-10000A.

3. bundling electrode high rate discharge processing method according to claim 1; It is characterized in that; Described discharge power supply is meant: provide pulse width and pulse spacing scope to be respectively 2 μ s-2000 μ s; Peak voltage ranges is 30V-60V, and peak point current is the pulse power of 500A-10000A, realizes electric pressure current interruption.

4. bundling electrode high rate discharge processing method according to claim 1 is characterized in that described lathe is meant: the lathe that has feeding of single main shaft automatic servo and rollback function at least.

5. bundling electrode high rate discharge processing method according to claim 1 is characterized in that, described water base working solution is the running water of 125～1250 μ s/cm for cutting emulsion or electrical conductivity.

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