Graphite electrode processing method

Abstract

The invention relates to a graphite electrode machining method in the technical field of electric spark machining. A hardware foundation of the method comprises a graphite electrode, a workpiece and a circuit part electrically connected with the graphite electrode and the workpiece. The method comprises the following steps: S1, processing preparation; s2, giving voltage, waiting for breakdown and entering servo control; s3, after breakdown, the IP adopts step waves, and meanwhile, proper voltage is given; s4, carrying out disruptive discharge; s5, judging whether to finish or not: if not, returning to execute the step S1; if yes, machining is finished. By the adoption of the scheme, the discharging process can be well controlled, and the machining efficiency is improved; while the processing efficiency is improved, the stability and controllability of the discharge process can be ensured, and the circuit part has anti-interference performance.

Description

Technical Field

[0001] The invention relates to the technical field of electric spark machining, in particular to a graphite electrode machining method. Background Art

[0002] Discharge machining is a process in which a power supply device applies a group of machining pulses composed of high and low voltage pulses to the machining gap. According to time division, it is generally divided into three stages: pulse width (ON), pulse stop (OFF) and waiting for breakdown time. Among them, the stage of applying high voltage during machining is called the ON stage, and the stage of applying machining voltage and shutting down is called the OFF stage. In the On stage, when the electric field strength of the gap is large enough, the insulating properties of the dielectric liquid in the gap are destroyed, and discharge occurs. The high temperature and high pressure generated by the discharge causes the workpiece material to evaporate or melt to achieve the purpose of removing the workpiece material. In the OFF stage, the insulating properties of the dielectric liquid can be restored to facilitate the next discharge. According to the different application methods in the ON stage, it can be divided into equal energy machining and equal pulse machining, which can be divided into equal pulse width machining with a fixed ON opening time and equal energy machining with a fixed actual discharge time period. It is known that equal energy machining can improve the uniformity of the workpiece machining surface. The waiting for breakdown time is very critical, and good control can often improve efficiency.

[0003] Discharge electrodes are usually copper and graphite. Considering factors such as price, processing difficulty, and weight, graphite electrodes are the preferred electrode type. However, higher requirements are placed on graphite electrodes. The loss must be low (the ideal state is no loss), and the processing efficiency must meet the process requirements. This places higher requirements on the discharge solution of the spark machine. Summary of the invention

[0004] The purpose of the present invention is to provide a graphite electrode processing method to meet the process requirements proposed in the prior art.

[0005] The object of the present invention is achieved as follows: a graphite electrode processing method, the hardware basis of the method includes a graphite electrode and a workpiece, and a circuit part electrically connecting the graphite electrode and the workpiece;

[0006] The method comprises the following steps:

[0007] S1. Processing preparation;

[0008] S2, set voltage, wait for breakdown and enter servo control;

[0009] S3, after breakdown, IP adopts step wave and gives appropriate voltage at the same time;

[0010] S4, breakdown discharge;

[0011] S5, determine whether to end:

[0012] If not, return to step S1;

[0013] If yes, the processing is finished.

[0014] Furthermore, the circuit part contains a MOS tube for converting a DC signal into a pulse signal, and a single breakdown discharge process is divided into a discharge pulse time period Ton, a discharge rest time period Toff, and a waiting breakdown time period Topen, wherein the discharge pulse time period Ton is the duration of opening the MOS tube.

[0015] Furthermore, in an ideal state, the length of the waiting-for-breakdown time period Topen is 0.

[0016] Furthermore, when the graphite electrode is about to contact the workpiece, a gap of 50 um is reserved.

[0017] Furthermore, the circuit part includes:

[0018] A first input unit having a first photocoupler;

[0019] a second input unit, wherein an output terminal of the first input unit is electrically connected to an input terminal of the second input unit;

[0020] Differential unit;

[0021] A second photoelectric coupler, wherein the output end of the second input unit is electrically connected to an input pin of the second photoelectric coupler through a differential unit;

[0022] Circuit protection unit;

[0023] A MOS tube, a gate of which is electrically connected to an output pin of the second photocoupler through a circuit protection unit;

[0024] A protection module, wherein the protection module is electrically connected to the drain of the MOS tube;

[0025] An input protection unit, wherein the input protection unit is electrically connected to the source of the MOS tube;

[0026] The graphite electrode terminal and the workpiece terminal are configured with a switchable contact unit and are electrically connected to the input protection unit through the switchable contact unit. The graphite electrode terminal and the workpiece terminal are electrically connected to the graphite electrode and the workpiece respectively.

[0027] Furthermore, the differential unit includes a differentiator U1B, an input end of the differentiator U1B is electrically connected to an output end of the second input unit, and the differentiator U1B is used for differentially receiving input electrical signals to prevent line interference.

[0028] Furthermore, the differential unit also includes a differentiator U2B, the input end of the differentiator U2B is electrically connected to the output end of the differentiator U1B, the output end of the differentiator U2B is electrically connected to the input pin of the second optocoupler, and the differentiator U2B is used to convert the input electrical signal into a differential signal so that the second optocoupler can receive it.

[0029] The beneficial effects of the present invention are:

[0030] The discharge process can be well controlled to improve processing efficiency;

[0031] While improving the processing efficiency, it can also ensure the stability and controllability of the discharge process, and its circuit part has anti-interference performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a simplified diagram of the operation process of the present invention.

[0033] Figure 2 It is a main circuit schematic diagram of the present invention.

[0034] Figure 3 is a schematic diagram of the first input unit.

[0035] Figure 4 is a schematic diagram of the input protection unit.

[0036] Figure 5 It is the actual output waveform diagram of the present invention.

[0037] Figure 6 Schematic diagram of the discharge pulse waveform of the present invention.

[0038] Explanation of the accompanying drawings: 1-first input unit; 2-first photoelectric coupler; 3-signal converter; 4-second input unit; 5-differential unit; 6-second photoelectric coupler; 7-circuit protection unit; 8-MOS tube; 9-protection module; 10-input protection unit; 11-openable and closable contact unit; 12-graphite electrode terminal; 13-workpiece terminal. DETAILED DESCRIPTION

[0039] The following will be combined with the attached embodiment of the present invention Figure 1-6 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Under the condition of equal energy: when the pulse discharge time is short (i.e. the pulse width is narrow), the surface roughness of the graphite electrode is greater than that of the copper electrode; conversely, when the pulse is wide, the surface finish of the copper electrode material is worse than that of the graphite electrode.

[0041] Discharge electrodes are usually copper and graphite. Considering factors such as price, processing difficulty, and weight, graphite electrodes are the preferred electrode type. However, higher requirements are placed on graphite electrodes. The loss must be low (the ideal state is no loss), and the processing efficiency must meet the process requirements. This places higher requirements on the discharge solution of the spark machine.

[0042] like Figure 1 As shown, a graphite electrode processing method is proposed, and the hardware basis of the method includes a graphite electrode and a workpiece, and a circuit part that electrically connects the graphite electrode and the workpiece.

[0043] The method comprises the following steps:

[0044] S1. Processing preparation;

[0045] S2, set voltage, wait for breakdown and enter servo control;

[0046] S3, after breakdown, IP adopts step wave and gives appropriate voltage at the same time;

[0047] S4, breakdown discharge;

[0048] S5, determine whether to end:

[0049] If not, return to step S1;

[0050] If yes, the processing is finished.

[0051] The above circuit part contains a MOS tube 8 for converting a DC signal into a pulse signal, such as Figure 5 , 6 As shown, the single breakdown discharge process is divided into a discharge pulse time period Ton, a discharge rest time period Toff, and a waiting breakdown time period Topen, wherein the discharge pulse time period Ton is the duration of opening the MOS tube 8, and the duration of the waiting breakdown time period Topen is 0 in an ideal state.

[0052] The method for selecting the breakdown time point is: according to the requirements of the workpiece processing drawings and the surface texture and smoothness requirements, select suitable parameters such as IP (peak current) and ON-OFF. When the graphite electrode is about to contact the workpiece, reserve a 50um gap and then discharge. This will not easily cause overshoot, carbon deposition or damage to the pointed graphite electrode.

[0053] The above circuit part includes:

[0054] The first input unit 1 controlled by the CPLD, such as Figure 3 As shown, it has two circuit modules and a first photocoupler 2 for coupling the two circuit modules, and also has a signal converter 3, the input end 9 pin of the signal converter 3 is electrically connected to the circuit module on the output side of the first photocoupler 2, the 8 pin of the signal converter 3 is connected to IP1+, and the 6 pin thereof is connected to IP1-;

[0055] A second input unit 4, wherein the output end of the first input unit 1 is electrically connected to the input end of the second input unit 4;

[0056] Differential unit 5, such as Figure 2 As shown, the differential unit 5 includes a differentiator U1B and a differentiator U2B, the input end of the differentiator U1B is electrically connected to the output end of the second input unit 4, the differentiator U1B is used to differentially receive the input electrical signal to prevent line interference, the input end of the differentiator U2B is electrically connected to the output end of the differentiator U1B, the output end of the differentiator U2B is electrically connected to the input pin of the second photoelectric coupler 6, and the differentiator U2B is used to convert the input electrical signal into a differential signal so that the second photoelectric coupler 6 can receive it;

[0057] The second photocoupler 6, the output end of the second input unit 4 is electrically connected to the input pins (pins 2 and 3) of the second photocoupler 6 through the differential unit 5;

[0058] Circuit protection unit 7;

[0059] MOS tube 8, whose gate G is electrically connected to the output pin (pin 6) of the second photocoupler 6 through the circuit protection unit 7, MOS tube 8 is used to convert the DC signal into a pulse signal to facilitate the discharge of the spark machine, and directly adding a DC signal will cause a short circuit;

[0060] Protection module 9, protection module 9 is electrically connected to the drain D of MOS tube 8, diode D2 is used to protect Q1 (MOS tube 8), when the voltage is too high, diode D2 is first broken down; C1, R3, R4 and D3 form an RDC loop to absorb negative voltage and AC voltage;

[0061] Input protection unit 10, combined with Figure 2 , 4 As shown, the input protection unit 10 is electrically connected to the source S of the MOS tube 8. The voltmeter indicates the average voltage between the electrode and the workpiece. The voltage waveform is measured and displayed by the oscilloscope voltage probe. The ammeter indicates the machining discharge current (average current). The waveform is measured and displayed by the oscilloscope current probe. Figure 5 As shown;

[0062] Graphite electrode terminal 12( Figure 4 P1) and workpiece end 13 ( Figure 4 P2), which is equipped with a switchable contact unit 11, and is electrically connected to the input protection unit 10 through the switchable contact unit 11, and the graphite electrode terminal 12 and the workpiece terminal 13 are electrically connected to the graphite electrode and the workpiece respectively.

[0063] The graphite electrode terminal 12 is connected to a fixture via a cable, and the fixture clamps the graphite electrode.

[0064] The "workpiece" mentioned in this article, according to industry common sense in the field of electrospark machining, is a conductive material, usually a mold to be processed.

[0065] The openable and closable contact unit 11 plays a role in polarity conversion. During normal processing, the electrode is positive and the workpiece is negative. In some special processing occasions, the electrode needs to be negative and the workpiece needs to be positive. Figure 4 The two groups of contactors in the circuit are converted (contactors NM1, NM2, RV1, RV2).

[0066] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "front", "back" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention; in the present invention, it should also be noted that the terms "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, an integrally formed connection, a mechanical connection, or an indirect connection through an intermediate connecting component, and the specific meaning of the terms in this utility model can be understood according to the specific circumstances.

[0067] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0068] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A graphite electrode processing method, characterized in that: The hardware basis of the method includes a graphite electrode and a workpiece, and a circuit part electrically connecting the graphite electrode and the workpiece; The method comprises the following steps: S1. Processing preparation; S2, set voltage, wait for breakdown and enter servo control; S3, after breakdown, IP adopts step wave and gives appropriate voltage at the same time; S4, breakdown discharge; S5, determine whether to end: If not, return to step S1; If yes, the processing is finished.

2. A graphite electrode processing method according to claim 1, characterized in that: The circuit part contains a MOS tube (8) for converting a DC signal into a pulse signal. The single breakdown discharge process is divided into a discharge pulse time period Ton, a discharge rest time period Toff, and a waiting breakdown time period Topen, wherein the discharge pulse time period Ton is the time length for opening the MOS tube (8).

3. A graphite electrode processing method according to claim 2, characterized in that: Ideally, the duration of the waiting breakdown period Topen is 0.

4. A graphite electrode processing method according to claim 1, characterized in that: When the graphite electrode is about to contact the workpiece, a 50um gap is reserved.

5. A graphite electrode processing method according to claim 2, characterized in that: The circuit part includes: A first input unit (1) having a first photocoupler (2); A second input unit (4), the output end of the first input unit (1) being electrically connected to the input end of the second input unit (4); Differential unit (5); A second photoelectric coupler (6), wherein the output end of the second input unit (4) is electrically connected to an input pin of the second photoelectric coupler (6) via a differential unit (5); Circuit protection unit (7); A MOS tube (8), a gate of which is electrically connected to an output pin of the second photoelectric coupler (6) through a circuit protection unit (7); A protection module (9), wherein the protection module (9) is electrically connected to the drain of the MOS tube (8); An input protection unit (10), the input protection unit (10) being electrically connected to the source of the MOS tube (8); The graphite electrode terminal (12) and the workpiece terminal (13) are provided with a switchable contact unit (11) and are electrically connected to an input protection unit (10) via the switchable contact unit (11). The graphite electrode terminal (12) and the workpiece terminal (13) are electrically connected to the graphite electrode and the workpiece, respectively.

6. A graphite electrode processing method according to claim 5, characterized in that: The differential unit (5) comprises a differentiator U1B, the input end of the differentiator U1B is electrically connected to the output end of the second input unit (4), and the differentiator U1B is used to differentially receive input electrical signals to prevent line interference.

7. A graphite electrode processing method according to claim 6, characterized in that: The differential unit (5) further comprises a differentiator U2B, the input end of the differentiator U2B being electrically connected to the output end of the differentiator U1B, the output end of the differentiator U2B being electrically connected to the input pin of the second photoelectric coupler (6), and the differentiator U2B being used to convert the input electrical signal into a differential signal so as to be received by the second photoelectric coupler (6).

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