JPS63283817A - Finishing method by electro-chemical machining - Google Patents

Abstract

PURPOSE:To make good the surface quality of a workpiece by reversing polarity between a workpiece and an electrode and removing a film on the surface of the electrode before finishing the workpiece. CONSTITUTION:A workpiece 2 processed by electric discharge machining is secured to a workpiece fixing device 3 and an electrode 4 is secured to an electrode fixing device 5. Then, the electrode 4 is switched to the positive side and the workpiece 2 to the negative side. In this state, electro-chemical machining is carried out, thereby removing a film formed on the surface 4a of the electrode 4. This electro-chemical machining process is repeated by the pre-determined times on the basis of the input data of an input device 13. Then, polarity is changed, thereby turning the workpiece 2 to the positive side and the electrode 4 to the negative side. And an electrolytic solution is jetted between processed surfaces 2a and 4a for discharging the removed film. Thereafter, the electro-chemical machining is carried out for finishing the workpiece 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a finishing method using electrolytic machining, and in particular to a method for finishing a three-dimensionally shaped workpiece made of a difficult-to-cut metal in a short time and with high precision. The present invention relates to a finishing method using electrolytic machining that allows for finishing with high precision and obtaining a mirror-like glossy surface.

[Conventional technology] Conventional metal processing methods involve filling the gap between the workpiece and the electrode with an electrolytic solution such as sodium nitrate or sodium chloride, flowing this electrolytic solution at high speed, and inhibiting stable electrolytic action. An electrolytic processing method in which a direct current is passed from the workpiece to the electrode while removing electrolytic products, that is, eluted metal compounds, metal ions, hydrogen gas, etc. 60-44228
The workpiece and the electrode are placed facing each other with a small gap in a machining liquid such as kerosene, and these are connected to an appropriate power source to prevent instantaneous spark discharge or transient arc discharge from occurring in the gap. There is a known electrical discharge machining method (see Japanese Patent Publication No. 60-26646 and Japanese Patent Application Laid-Open No. 60-177819) in which a workpiece is machined by the discharge energy generated.

[Problems to be Solved by the Invention] However, in the former electrolytic processing method, particularly in processing with a three-dimensional bottom (meaning processing on a three-dimensional structure formed in the shape of a concave hole), There are disadvantages in that it is difficult to precisely transfer the electrode to the workpiece, and high-precision surface quality cannot be obtained.In addition, the latter electric discharge machining method has the disadvantage that it is difficult to precisely transfer the electrode to the workpiece. difficult to obtain,
For example, there is an inconvenience in that surface finishing such as mirror finishing requires a lot of time and effort.

Therefore, the present applicant has proposed a finishing method using electrolytic machining to eliminate these inconveniences, in Japanese Patent Application No. 62-27 (31
No. 6 was filed, but in this finishing method, a predetermined pulse current is supplied with the workpiece as an anode (positive potential) and the electrode as a cathode (negative potential with respect to the workpiece). .

By the way, in the finishing method using electrolytic processing,
Generally, a copper electrode that has been subjected to electric discharge machining, which is the main machining process, is used, but the surface of this copper electrode (hereinafter referred to as the electrode surface) is exposed to high temperatures and carbonized by the kerosene-based machining fluid used during electric discharge machining. The carbon deposited thereon forms a graphite film. Although this graphite film is effective in preventing wear of the electrode, when this electrode is used as it is for finishing processing by electrolytic processing, there are the following disadvantages.

In other words, the film formed on the electrode surface is damaged by the centering work between the electrode and the workpiece before finishing or the contact between the electrode and the workpiece (detection of the machining origin) during the initial stage of finishing. If finishing is performed in this state, the graphite film on the electrode surface has a higher electrical resistance than the pure copper surface, so the current density of the supply pulse increases in the area where the film is damaged and the copper is exposed, and the current density in the vicinity The processing progresses significantly.

Therefore, there are significant differences in the processing conditions for each part of the workpiece surface, resulting in striped patterns on the workpiece surface, which significantly impairs the surface quality when a mirror-like glossy surface is desired. .

It is also conceivable to manually remove the film on the electrode surface, but this method requires a great deal of labor and is disadvantageous in that it may impair the shape accuracy of the electrode.

[Purpose of the Invention] Therefore, the present invention aims to eliminate the above-mentioned disadvantages, and to obtain a mirror-like glossy surface by finishing the three-dimensionally shaped work surface of a workpiece such as a difficult-to-cut metal in a short time and with high precision. The purpose of this invention is to realize a finishing method using electrolytic machining.

[Means for Solving the Problems] In order to achieve this object, the present invention arranges a workpiece machined by electrical discharge machining and an electrode used in electrical discharge machining opposite to each other via an electrolytic solution, and In a finishing method in which a pulse is supplied between a workpiece and an electrode and finishing is performed while intermittently removing electrolytic products generated between the workpiece and the electrode, the electrode is an anode and the workpiece is a cathode. a first processing step in which a pulse is supplied to process the workpiece, and a second processing step in which a pulse is applied after the first processing step in which the workpiece is used as an anode and the electrode is used as a cathode. It is characterized by

[Operation] According to the configuration of the present invention, in the first processing step before starting the finishing process of the workpiece, electrolytic machining is performed by reversing the polarity of the pulse supplied between the workpiece and the electrode, and In order to remove the film formed on the electrode surface during electrical discharge machining of objects, the electrode surface can be made into a uniform surface condition during the second machining process, which is finishing machining, and striped patterns can be prevented from occurring on the machined surface. Good surface quality can be obtained.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

1 to 4 show one embodiment of this invention. In FIGS. 1 to 3, reference numeral 1 denotes a processing device capable of implementing the finishing method according to the present invention, and this processing device 1 includes a workpiece fixing device 3 for fixing a workpiece 2, and an electrode for fixing an electrode 4. A fixing device 5, a drive conversion section 7 that converts the rotational motion of the electrode drive section 6 into a reciprocating motion, a power supply device 8 that generates a pulse current, a motor drive control section 9, a processing condition control section 1O, and an electrolyte flow control section 1.
1, an input device 13 for inputting data regarding the workpiece 2, an electrolytic solution filtration device 14, an electrolytic method scattering prevention cover 15, and the like.

The workpiece fixing device 3 is made of highly insulating granite or ceramics, and is, for example,
A workpiece 2 machined by electrical discharge machining is fixed with bolts 16 or the like using a table that is movable in the Y direction or is movable by being supported at three points on the machining device l. Further, the electrode fixing device 5 has an electrode 4 made of, for example, pure copper and used during the electrical discharge machining, attached to the lower end of a rod 17 provided at the lower part of the electrode fixing device 5.
and are fixed so as to maintain a uniform gap 18 in the three-dimensional direction. The electrode fixing device 5 includes the electrode driving section 6.
and the drive converter 7 move up and down to set the gap 18 to a predetermined value. That is, the rotation of the motor 19 is controlled by control signals output from the motor drive control section 9 of the control device 12 based on signals from the rotary encoder 20 and tacho generator 21 of the electrode drive section 6, and the rotational movement of the motor 19 is controlled. The drive conversion unit 7 converts the movement into a reciprocating motion, moves the electrode fixing device 5 up and down, and sets a predetermined gap 18 between the electrode surface 4a and the surface to be processed 2a.

The power supply device 8 supplies a pulse current with a current density (average current per unit area) of 70 A/Cm2 or less between the workpiece 2 and the electrode 4, and the power supply device 8 supplies the workpiece with a pulse current having a current density (average current per unit area) of 70 A/Cm2 or less. It generates a pulse current with a predetermined current density calculated according to the surface area of No.
It is configured as shown in the figure.

In FIG. 4, the DC power supply unit 22 includes a transformer 25 and a rectifier 26. The voltage is lowered to a predetermined value by the transformer 25 and rectified by the rectifier 26 to obtain a DC current. ~27-n.

Further, the charging/discharging section 23 has a gap 1 between the workpiece 2 and the electrode 4.
8, a plurality of capacitors 27-1 to 27-n
and connected to each of these capacitors 27-1 to 27-n,
Diodes 28-1 to 28-0 that prevent backflow of charges to the DC power supply section 22 side, discharge switches 29-1 to 29-n that are opened and closed to discharge charges to the discharge side, and each of the capacitors 27 -1 to 27-n, and a charging switch 30 for supplying and disconnecting power from the DC power supply section 20 to charge the batteries to a predetermined value.

A charging/discharging control unit 24 that controls the charging/discharging unit 23 includes a voltage detector 31 that detects charging voltage values supplied to the capacitors 27-1 to 27-n, and a charging voltage setting unit 36 of the processing condition control unit IO. a voltage comparator 32 that compares the set charging voltage value set with the detected charging voltage value detected by the voltage detector 31; and a current value of the charge discharged into the gap 18 between the workpiece 2 and the electrode 4. a current detector 35 that detects the current value, a current comparator 34 that compares the minimum current value set by the minimum current setting unit 39 of the machining condition control unit 10 and the discharge current value detected by the current detector 35; If the detected current value is equal to or greater than the set current value based on inputs from the pulse generator 37, current waveform setting unit 38, and current comparator 34 of the processing condition control unit 10, each of the capacitors 27-1 to 27 -n
The respective discharge switches 29 are configured to discharge the electric charges of the respective capacitors 27-1 to 27-n as desired to the discharge side, and to stop discharging the electric charges of the respective capacitors 27-1 to 27-n when the detected current value is less than the set current value. -1 to 29-n, and a control signal of the polarity switching control section 40 of the processing condition control section 10 to control the polarity of the pulse current supplied between the workpiece 2 and the electrode 4. It has a polarity switch 41 for switching.

Further, the machining condition control unit IO of the control device 12 that controls the charge/discharge control unit 24 controls each of the capacitors 27-1 to 27-
A charging voltage setting section 36 that sets the charging voltage of n, a pulse generating section 37 that generates a pulse with a predetermined time width, and a current waveform setting section that sets the current waveform of the charge discharged between the workpiece 2 and the electrode 3. 38, a minimum current setting section 39 that sets a minimum current value, a polarity switching control section 40 that controls the polarity switching device 41, and a calculation/processing section that calculates and processes processing conditions etc. based on the input data of the input device 13. It consists of a processing unit (hereinafter referred to as CPU) 46 and the like.

In addition, the reference numeral 44 in FIG. 4 indicates the discharge switches 29-1 to 29.
- Each discharge switch 29-1 ~ due to the back electromotive force when n is opened.
This is a diode that prevents the 29-n from being destroyed.

The human power device 13 inputs the material and surface area of the workpiece, the finishing margin and dimensional accuracy grade, the finished surface roughness, the initial electrode gap, etc., and sends these signals to the motor drive control section of the control device 12. 9 and the processing condition control section 10.

The electrolyte filtration device 14 filters an electrolyte 42 containing electrolytic products generated during processing, and the electrolyte flow control unit 11
Based on the control signal from the electrolyte tank 43, the electrolyte 42
is supplied with a constant hydraulic pressure, and the workpiece surface 2 is
The electrode 4 moves upward every pulse or every few pulses in order to eliminate electrolytic products generated between the electrode surface 4a and the electrode surface 4a.
In synchronization with this, the electromagnetic valve 45 and the like are controlled so as to spout fresh electrolyte 42 between the workpiece 2 and the electrode 4.

Next, a finishing method using this apparatus will be explained.

First, the workpiece 2 machined into a desired shape by electrical discharge machining is fixed to the workpiece fixing device 3, and the electrode 4 used during the electrical discharge machining is fixed to the lower end of the rod 17 of the electrode fixing device 5. 4 is lowered to bring its electrode surface 4a into opposing contact with the surface 2a to be processed of the workpiece 2, and the electrode 4 and the workpiece 2 are immersed in the electrolyte solution 42 of the electrolyte bath 43. Then, the electrode 4 is raised to a position that maintains the initial electrode gap, and when the electrolytic solution 42 fills between the workpiece surface 2a and the electrode surface 4a, the polarity switch 4
1, the electrode 4 is switched to the anode side and the workpiece 2 is switched to the cathode side. In this state, a pulse current of a predetermined current density is supplied between the workpiece 2 and the electrode 4 to perform electrolytic machining. Processing step 1) is performed to remove a film made of, for example, graphite formed on the electrode surface 4a. After performing this electrolytic processing a pre-calculated number of times (one to several times) by the CPU 46 based on the input data of the input device 13, the CPU
A control signal is sent from U46 to the polarity switching control unit 40, and the polarity switching device 41 is operated to switch the polarity of the pulse current supplied between the workpiece 2 and the electrode 4, so that the workpiece 2 is placed on the anode side and the electrode 4 is placed on the anode side. On the cathode side.

Then, the electrode 4 is raised to form a surface to be processed 2a and a surface to be processed 4a.
By spouting the electrolytic solution 42 in between, the removed film and the like are removed, and then the electrode 4 is lowered again to face-to-face contact with the workpiece surface 2a, and this point is set as the origin A, and the initial electrode gap is maintained. When the electrode 4 is raised and the electrolytic solution 42 fills between the surface to be processed 2a and the electrode surface 4a, finishing processing (second processing step) is started using this as the processing origin.

In the first half of finishing machining, a pulse current of a predetermined current density is supplied from the power supply device 8 according to a control signal from the machining condition control unit 10.
For example, a pulsed current with a pulse on time of 10 m5ec or less is supplied between the workpiece 2 and the electrode 4. As a result, the material of the processed surface 2a is eluted.

After supplying a predetermined pulse current once or several times, the motor 19 is driven by a signal from the motor drive control unit 9 to
is raised to separate the electrode surface 4a from the surface to be processed 2a. Due to this separation, electrolytic products between the processed surface 2a and the electrode surface 4a are removed together with the electrolytic solution 42 by the operation of the electromagnetic valve 45 of the electrolytic solution filtering device 14, etc.

After removing the electrolytic products, the electrode 4 is lowered and the electrode surface 4
h comes into contact with the processed surface 2a. As a result, the origin A
and the current position are compared by the control device 12 to measure the machining depth per machining (machining every one pulse or several pulses). Thereafter, the electrode 4 is raised again so that a predetermined gap 18 is maintained between the surface to be processed 2a and the electrode surface 4a, and the electrolyte 42 that does not contain electrolytic products in the electrolyte layer 43 is transferred between the surface to be processed 2a and the electrode surface. 4a, and the electrode 4 is at a predetermined position (
After the electrode surface 4a reaches a position at which a predetermined gap 18 is maintained between the electrode surface 4a and the surface to be processed 2a, and the electrolytic solution has calmed down for 1 to 5 seconds, a pulse current is supplied to perform the next processing. The electrolyte filtration device 1 is provided in the electrolyte layer 43 so as to supplement the electrolyte 42 that is removed together with the electrolytic products generated in one or several electrolytic processes.
Fresh electrolyte 42 is supplied from the clean tank 4.

In this way, the electrolytic solution 42 is filled between the workpiece surface 2a and the electrode surface 4a, which face each other with a predetermined gap 18, and a predetermined pulse current of 10 m5ec or less is applied between the workpiece 2 and the electrode 4. After supplying and dissolving the material of the surface 2a to be processed into the electrolytic solution 42, the electrolytic products generated between the surface 2a and the electrode surface 4a are removed, and the electrode surface 4a is brought into contact with the surface 2a to be processed again. By doing so, a series of finishing steps of measuring the machining depth per knee and accumulating each value is repeated a predetermined number of times according to a signal from the control device 12.

The cumulative value of the machining depth is compared with the set value of the machining depth calculated by the machining condition control unit IO based on the input data inputted by the input device 13, and the cumulative value of the machining depth is determined as the set value of the machining depth. When the difference is within a predetermined value (for example, 1 μm), the CPU 46 outputs a control signal to the current waveform setting unit 38, and the current density of the pulses from the power supply device 8 exceeds 273, which is the current density in the first half of the finishing process. The current density, for example, the pulse on time is changed to a long pulse current of 15 to 60 m5ec. Then, machining is performed a predetermined number of times using this pulsed current having a constant current density in the same manner as described above, and finishing machining is completed.

Next, an example of processing using the finishing method in electrolytic processing according to the present invention will be shown.

Electrode Pure copper Workpiece material Tool steel (surface roughness 20μm) Electrolyte Sodium nitrate solution (concentration 40%) First machining process pulse-on time 15m5ec Current density 40A/cm2 Second machining process (finishing process) Finishing Pulse-on time in the first half of machining 5m5ec Current density 17A/cm2 Pulse-on time in the latter half of finishing machining 15m5ec Current density 4OA/cm2 Finished surface roughness Rmax: 1μm or less Finished surface
Mirror-like glossy surface As described above, in the finishing method by electrolytic machining according to the present invention, the film made of graphite or the like formed on the surface of the electrode during the main machining, electrical discharge machining, is removed from the electrode 4 on the anode side. The electrode surface 4a is removed in the first processing step and then finished in the second processing step using the workpiece 2 as an anode. The processing conditions can be made uniform over the entire area 2a, and striped patterns will not occur on the processed surface 2a, etc.
Good surface quality is obtained. Furthermore, by attaching a workpiece 2 processed into a desired shape and an electrode 4 to the processing device 1, inputting finishing conditions etc. through the input device 13, and starting the processing device 1, a three-dimensional metal curved surface with a mirror-like luster can be produced. It can be obtained unattended and in a short time, and the surface has no accumulation of internal stress, no change in metal structure, no deterioration such as penetration of mechanical cracks, and the quality of heat treatment before processing is not impaired. , it will have a significant effect on quality improvement and mechanization in the field of finishing processing, where labor savings are the slowest in current mold processing.

In the above embodiment, polarity switching is automatically performed by the polarity switching device 41 based on a command from the polarity switching control section 400.
However, the present invention is not limited thereto, and the polarity switch 41 may be operated manually by, for example, a switch provided in the input device 13 before finishing. However, the present invention is not limited to the above embodiments, and any suitable means may be adopted.

Furthermore, in the above embodiment, the cycle for eliminating electrolytic products between the electrode surface 4a and the surface to be processed 2a is performed every pulse, which is most stable over the entire area of the surface to be processed. When the on-time of the pulse is as short as 1 m5 ec, there are few electrolytic products generated in one pulse processing, so that they can be removed every few pulses.

[Effects of the Invention] As explained in detail above, in the finishing method by electrolytic machining according to the present invention, the workpiece machined by electrical discharge machining and the electrode used for electrical discharge machining are connected via machining fluid. In addition, when performing finishing processing while supplying a pulse current between the workpiece and the electrode and intermittently removing electrolytic products generated between the workpiece and the electrode, the electrode is used as an anode. A first machining step in which a pulse is supplied with the workpiece as a cathode for machining; and after the first machining step, a final machining step is performed in which a pulse is supplied with the workpiece as an anode and the electrode as a cathode for final machining. Since the second processing step is configured, the processing conditions are adjusted over the entire surface to be processed in order to remove the film formed on the surface of the electrode used for finishing and to perform finishing with the electrode surface in a uniform state. It is possible to obtain a three-dimensional metal surface that is uniform, has no striped pattern on the processed surface, and exhibits a mirror-like luster with high precision and minute surface roughness in a short time. In addition, it is possible to obtain a surface that does not accumulate internal stress or change the metal structure, shows no deterioration such as the penetration of mechanical cracks, and does not impair the quality of heat treatment before processing. Quality improvement and mechanization in the field can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a finishing device for implementing the present invention, FIG. 2 is a side view of the device, FIG. 3 is a schematic configuration diagram of the device, and FIG. 4 is a block diagram showing a power supply device. . DESCRIPTION OF SYMBOLS 1... Processing device, 2... Workpiece, 40, Electrode, 6
... Electrode drive unit, 7... Drive conversion unit, 8... Power supply device, 9... Motor drive control unit, lO... Processing condition control unit, 11... Processing liquid flow control unit, 12... Control device, 13... Human power device, 14... Processing liquid filtration device,
40...Polarity switching control section, 41...Polarity switching device, 4
6...CPU. 1111 Figure 2

Claims (1)

[Claims] A workpiece machined by electric discharge machining and an electrode used for electric discharge machining are placed opposite each other via an electrolyte, and a pulse is supplied between the workpiece and the electrode to generate electrolysis between the workpiece and the electrode. In a finishing method in which a product is finished while being intermittently removed, a first processing step of processing by supplying a pulse with the electrode as an anode and the workpiece as a cathode, and the first processing step Afterwards, a second process is performed by supplying a pulse that uses the workpiece as an anode and the electrode as a cathode.
A finishing method using electrolytic processing, which consists of the following processing steps.