JPH01316129A - Finishing work through electrolytic working - Google Patents

Abstract

PURPOSE:To obtain the surface roughness with high precision in a short time by surely removing an oxidized film by comparing the between-electrode current detection value and the electric current value set according to the property, etc. of a workpiece and increasing and decreasing the electric current density of the pulse current supplied between the electrodes. CONSTITUTION:The electric pulse current having a prescribed electric current density is supplied into an electrode gap 17 between an electrode 2 and a workpiece 4 which are oppositely arranged through a static electrolytic solution, and the between-electrode current value is detected by a working condition control part 10 through an electric charge/discharge part 26. When the electric current value reduces to a prescribed current value by the formation of the oxidized film of a worked surface 4a, the automatic switching to the electric pulse current having a high current density is performed, and the electric pulse current is supplied in a prescribed number of times, and after the oxidized film on the worked surface 4a is removed, the electric pulse current having a prescribed electric current density is restored. Further, the above specific current value is automatically set according to the between-electrode current value and the property of the workpiece 4 at the start of working. Thus, the surface roughness of the worked surface can be improved with high precision in a short time.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a finishing method using electrolytic processing, and in particular, it can finish a three-dimensionally shaped work surface in a short time and with high precision to create a mirror-like glossy surface. The present invention relates to a finishing method using electrolytic machining.

[Prior Art] As a conventional metal processing method, an electrolytic processing method is known. In this electrolytic processing method, the gap between the workpiece and the electrode is filled with an electrolytic solution such as sodium nitrate or thorium chloride, and this electrolytic solution is flowed at high speed. This process involves passing a direct current from the workpiece to the electrode while removing metal compounds, metal ions, hydrogen scum, etc. (Unexamined Japanese Patent Publication No. 1986-
71921 and Japanese Patent Laid-Open No. 60-44228) Problems to be Solved by the Invention However, this electrolytic machining method has a fatal flaw as a machining means. In other words, especially in bottom machining of a three-dimensional shape (machining of a three-dimensional structure formed in the shape of a concave hole), even if the gap force between the workpiece and the electrode is constant at 4, the electrolytic The flow path resistance of the gap changes depending on the position of the liquid inlet, the distance from the inlet, the degree of curvature of the three-dimensional shape of the workpiece surface, etc., and the electrolyte can be flowed into the gap at a different flow rate. It is impossible to flush.

Therefore, the removal effect of electrolytic products generated in the gap differs depending on the position, and the progress of processing differs, making it difficult to precisely transfer the electrode to the workpiece. If surface quality is desired, another polishing step is required, which is disadvantageous in that it takes a lot of time and effort to finish the surface to be machined.

Therefore, in order to eliminate these inconveniences, Kanto Toyama devised a solution that could be applied to the workpiece by keeping the electrolyte in a static state and supplying a pulsed current with a low current density between the electrode and the workpiece during the early stage of finishing. In addition to improving the surface roughness of the surface, a pulsed current with high current density is intermittently supplied during this machining to remove the oxide film that is generated on the workpiece surface during machining, and also to filed an application (see Japanese Patent Application No. 117486/1986) for a finishing method using electrolytic processing to obtain a glossy surface by supplying a pulsed current with a high current density.

However, in this finishing method using electrolytic processing, a pulsed current with a high current density is supplied at regular intervals to remove the oxide film during the first half of the finishing process. The degree of formation of the oxide film differs depending on the shape of the workpiece, the means for removing electrolytic products, etc. Therefore, for example, if the cycle is shortened and the timing of switching to the high current density pulse current is earlier, The progress of improving the surface roughness is delayed, resulting in longer machining time, and if the cycle is lengthened and the timing is delayed, an oxide film with high electrical resistance will grow locally, changing the current density flowing through each part.
There have been disadvantages in that it is difficult to set the pulse current switching timing to the optimum processing conditions, such as fluctuations in the amount of processing per area, which disrupts the accuracy of the processed shape and makes it difficult to obtain high-precision surface quality.

In addition, the timing to switch to a pulsed current with a high current density, or the timing to switch from a high current density to a pulsed current with a low current density, is determined depending on the shape of the workpiece, the processing area, the type of means for removing electrolytic products, etc. This has the disadvantage of lowering the work efficiency of finishing machining.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to optimize the switching timing of the pulse current, and to improve work efficiency.
In particular, it is an object of the present invention to realize a finishing method using electrolytic machining that can finish a three-dimensionally shaped work surface in a short time and with high precision to obtain a mirror-like glossy surface.

[Means for Solving the Problem] In order to achieve this object, the first invention of this application is to electrolyze a workpiece and an electrode having an electrode surface patterned after the surface of the workpiece in a stationary state. a step of supplying a pulsed current having a predetermined current density between the machining electrodes and detecting a current value between the electrodes based on the pulsed current; The method comprises the steps of: comparing the current value with a predetermined current value set depending on the properties of the object; and increasing/decreasing the current density of the pulse current based on the comparison result; and supplying the increased/decreased pulse current between the electrodes. It is characterized by

In addition, a second invention provides a method in which a workpiece and an electrode having an electrode surface patterned after the surface of the workpiece are placed opposite to each other via a stationary electrolyte solution, and a predetermined current density is applied between the electrodes. a step of supplying a pulsed current, a step of detecting a current value between machining points based on the pulsed current, and a step of setting a lower limit current value based on the current value between machining holes and the properties of the workpiece at the beginning of machining. The method is characterized by comprising a step of comparing the gap current value and the lower limit current value during processing, and increasing or decreasing the current density of the pulse current based on the comparison result.

[Function] According to the configuration of the first invention of this application, a pulse current having a predetermined current density is supplied between the opposed electrodes and the workpiece through a stationary electrolyte, and Detects the current value between the machining areas based on the pulsed current, and when this current value decreases due to the formation of an oxide film on the workpiece surface and becomes less than a predetermined current value, the pulsed current is supplied between the machining areas. Automatically switches the current density to a pulsed current with a high current density, supplies this pulsed current a predetermined number of times to remove the oxide film on the workpiece surface, and then supplies a pulsed current with a predetermined current density again. The current density of the pulse current can be changed according to the degree of formation of an oxide film on the surface to be processed, and the surface to be processed can be finished in a short time and with high precision.

Further, according to the configuration of the second invention, the lower limit current value is automatically calculated based on the machining current value at the start of machining and the properties of the workpiece, and the lower limit current value and the machining current value during machining are Since the current density of the pulse current is switched by comparing the current density with the current density of the pulse current, there is no need to input the switching timing, and work efficiency can be improved.

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

1 to 7 show one embodiment of this invention.

In FIG. 1.2, an electrolytic finishing apparatus 1 capable of carrying out the present invention includes an electrode fixing device 3 for fixing an electrode 2, a workpiece fixing device 5 for fixing a workpiece 4, and an electrode drive unit 60.
A control device 12 consisting of a drive conversion section 7 that converts rotational motion into reciprocating motion, a power supply device 8 that generates a pulse current, a motor drive control section 9, a processing condition control section 10, an electrolyte flow control section 11, etc., and a workpiece. 4, an electrolyte filtration device 14 for filtering the electrolyte, a processing tank 15, and the like.

The electrode fixing device 3 has an electrode 2 made of, for example, pure copper or graphite attached to the lower end of a rod 16 provided at its lower part, so that the electrode surface 2a and the processed surface 4a of the workpiece 4 are aligned three-dimensionally. It is fixed so that a gap 17 is maintained. The electrode fixing device 3 is moved up and down by the electrode driving section 6 and the drive conversion section 7 to set the gap 17 to a predetermined value. That is, the rotary encoder 18 of the electrode drive unit 6
The motor 20 is controlled by a control signal outputted from the motor drive control section 9 in response to a signal from the tachogenerator 19.
is rotated to move the electrode fixing device 3 up and down to set a predetermined gap 17 between the electrode surface 2a and the surface to be processed 4a.

The workpiece fixing device 5 is a table made of highly insulating granite or ceramics, and is mounted on the X-Y table 21 (not shown) of the electrolytic finishing device 1 together with the bottom plate of the processing tank 15, such as bolts, etc. Fix it by.

Further, the workpiece 4 is fixed to the upper surface of the workpiece fixing device 5 with bolts 22, etc., so that the workpiece 4
, the workpiece fixing device 5 and the processing tank 15 are connected to the X-Y table 2
It moves integrally in the X direction and the X direction by rotating the moving knob 23 and 240 of No. 1.

A power supply device 8 that supplies a predetermined pulse current between the electrode 2 and the workpiece 4, and a processing condition control unit 10 of the control device 12 that controls the power supply device 8 are configured as shown in FIG. 3, for example. Configure as shown.

That is, the power supply device 8 includes a DC power supply unit 25 and a charging/discharging unit 26, and the DC power supply unit 25 includes a transformer 27 and a rectifier 28.
The voltage is lowered to a predetermined value by a transformer 27 and rectified by a rectifier 28 to obtain a direct current, which is supplied to capacitors 29-1 to 29-n, which will be described later.

The charging/discharging unit 26 also includes a plurality of capacitors 29-1 to 29-n that discharge charges between electrodes, and each of these capacitors 29-
Diodes 30-1 to 30-n connected to diodes 1 to 29-n to prevent backflow of charges to the DC power supply section 25 side, and capacitor 2
Discharge switches 3111 to 31-n that are opened and closed to discharge the charges of 9-1 to 29-n, and each of the capacitors 29-
It consists of a charging switch 32 and the like that supplies power from the DC power supply section 25 to charge the batteries 1 to 29-n to a predetermined value.

The machining condition control unit 10 that controls the charging/discharging unit 26 includes a voltage detector 33 that detects the charging voltage values of the capacitors 29-1 to 29-n, and a D/D ratio between the charging voltage values detected by the voltage detector 33 and A voltage comparator 35 that compares the output value from the A converter 34, and a charging detector 36 that detects the completion and start of charging of the capacitors 29-1 to 29-n based on the output signal from the voltage comparator 35. and a current detector 37 that detects the inter-electrode current value of the charge discharged between the electrodes.
a current comparator 40 that compares the peak value held by the peak hold circuit 38 with the output value of the D/A converter 39; Opening/closing drive signals are provided to each of the discharge switches 31-1 to 31-n by human signals from a pulse generator 41 that generates pulses with a predetermined time width and a current waveform setting device 42 that sets the current waveform of the charge discharged between the poles. a gate circuit 43 that outputs
Set the charging voltage value to be supplied to 9-n and send that signal to the D
a charging voltage setter 44 that outputs to the /A converter 34; a current setter 45 that sets a current value between electrodes and outputs the signal to the D/A converter 39; and input data of the input device 13, etc. A CPU 46 that calculates and processes processing conditions etc. based on the
It consists of a contact detector 47 and the like that detect contact between the electrode 2 and the workpiece 4. In addition, the reference numeral 48 in the figure is the discharge switch 31-1.
~31-n is opened, each discharge switch 31 is
This is a diode that prevents -1 to 31n from being destroyed.

Note that the control of the CPU 46 when the capacitors 29-1 to 29-n are charged and discharged will be explained here. First, CP
U46 is based on the machining area S of the workpiece 4 inputted in advance by the input device 13 and the on-time ton (hereinafter referred to as pulse width) of the single pulse current supplied between the poles.
A charging voltage value at which the peak current density of the supplied pulse current becomes a predetermined value is calculated using a characteristic table input in advance to the storage device, and is output to the charging voltage setter 44 of the processing condition control section 10. This set voltage value ■ is calculated, for example, by the following formula.

V=VQ+ (KIXδx r ) + (K2+ T
+S) However, VO2 Fixed voltage Kl, 2: Constant δ: Electrode gap ■: Current density S: Machining area And when the capacitors 29-1 to 29-n are charged at a predetermined charging voltage value, charging is completed. The signal is C from the charge detector 36.
It is input to PU46. This signal causes CPO46 to
A control signal is output to the pulse generator 41 and the current waveform setting device 42 to turn on the gate circuit 43, and the discharge switch 3 is turned on.
All or part of 1-1 to 31-n are turned on at the same time, and a predetermined pulse current is supplied between the electrodes. A current value between electrodes based on this pulse current is detected by a current detector 37, and a peak value at that time is held by a peak hold circuit 38. This held peak value is compared with a signal value obtained by converting the digital signal of the current setting device 45 into an analog signal by a D/A converter 39 by a current comparator 40,
The result is input to the CPU 46. In this case, the comparison method of the current comparator 40 is to increase the count value of the current setter 450 counter (not shown) one step at a time from 0, and the value obtained by D/A converting the second value is the peak hold circuit 3 days. When the peak value of is exceeded, the output of the current comparator 40 is inverted,
The count value of the counter at that time is stored in the CPU 46 as the peak value of the inter-electrode current value.

Based on the stored peak value, the CPU 46 corrects the set voltage value V of the charging voltage setter 44 (for example, if the stored peak value is lower than the provisionally set set current value, the set voltage value ■ is increased, the peak value is larger than the set current value, the set voltage value V is decreased), and the lower limit current value is calculated by multiplying the peak value by a constant determined based on the properties such as the material and processing area S of the workpiece 4, etc. This is then set in the current setting device 45.

Then, a pulse current of a predetermined peak current density is again supplied between the electrodes from the capacitors 29-1 to 29-n charged based on the corrected set voltage value V, and the current detector 37 detects the current between the electrodes. While detecting the value, the peak hold circuit 38 holds the peak value, and the current comparator 40 compares this peak value with the lower limit current value set by the current setting device 45, and the peak value is lower than the lower limit current value. CPU4 when
A signal is output to 6.

Based on this output signal from the current comparator 40, the CPU 46 increases the set voltage value ■ of the charging voltage setter 44 to a voltage value at which a pulse current with a high current density is obtained. The above is C
This is control of PtJ46.

FIG. 4 is a circuit configuration diagram embodying the schematic configuration diagram of FIG. 3, and the same parts as in FIG. 3 will be described below with the same reference numerals.

The DC power supply section 25 includes each coil 27-1 of the transformer 27.
27-3 to drop the voltage to a predetermined value, and rectify it by each of the diodes 28-1 to 28-3 to obtain a DC power source, which is output via the resistor 50.

The discharge switch 311 (discharge switch 31-1 to 31-3
1-n all have the same configuration, so the discharge switch 31-1
) are five transistors 51-1 to 51-1.
55-1 and six resistors 56-1 to 61-1,
Each of the transistors 51-1 to 5
5-1 are turned on one after another to discharge the charge in the capacitor 29-1. Reference numeral 63-1 in the figure is a resistor connected in parallel with the capacitor 29-1.

Further, the charging switch 32 includes four transistors 6
4 to 67 and five resistors 68 to 72, each transistor 64 to 67 is turned on and off by the output of the voltage comparator 35.
It is turned off to supply and disconnect power from the DC power supply unit 25, and charge each of the capacitors 29-1 to 29-n to a predetermined value. Note that a diode 73 with one end connected is connected between the DC power supply section 25 and the charging switch 32 to protect the charging switch 32.
The other end is grounded via a capacitor 74 and a resistor 75.

The voltage detector 33 includes a capacitor 76 whose one end is grounded.
The charging voltage value obtained by dividing the voltage by two series resistors 77 and 78 connected in parallel with this capacitor 76 is output. The output side of this voltage detector 33 is connected to one input side of a comparator 80 of the voltage comparator 35 via a resistor 79. The other input end of the comparator 80 is connected to the output side of the D/A converter 34 via a resistor 81. Between the resistor 79.81 and the comparator 80, a dihode 82.
Connect 83. A resistor 84 is connected to the output side of the comparator 80, a diode 85 whose one end is grounded is connected to the resistor 84, and the base of the transistor 64 of the charging switch 32 is connected to the resistor 84.

This voltage comparator 33 compares the set voltage value Vs outputted from the D/A converter 34 and the charging voltage value V1 detected by the voltage detector 33, and the comparison result is explained in the charging switch 32 and later. Output to charge detector 36.

The charge detector 36 is composed of two flip-flops (hereinafter referred to as F° F) 86 and 87 pulled up to the power supply by a resistor 93, and three gates 88 to 90, and the voltage comparator 35 The output side of is connected to one trigger terminal of one FF 86 and to one trigger terminal of the other FF 87 via a gate 88 .

Then, one output of FF86 is passed through gate 89 to C
It is connected to the terminal 91 of the PtJ 46, and one output of the FF 87 is connected to the terminal 92 of the CPU 46 via the gate 90.

With this configuration, a charging start signal can be detected through the terminal 91, and a charging completion signal can be detected through the terminal 92.

The current detector 37 has a resistor 94 on the ground side of the electrode 2, and connects the resistor 94 on the electrode 2 side with two coils 95.9.
6 and a capacitor 97, and a resistor 98 connected in series with this filter, to one input side of an amplifier 99, and the other input end of this amplifier 99 is connected to a resistor 100. Ground through. This amplifier 99 has its output side connected to the input end connected to the resistor 98 via a resistor 101, and its output side connected to one input end of an amplifier 102. The amplifier 102 has the other input terminal grounded through a resistor 103, and its output side connected to one input terminal through a resistor 104, and detects and outputs a current value between electrodes.

The peak hold circuit 38 connects the output side of the amplifier 102 of the current detector 37 to the other input terminal of the amplifier 105, and connects one input terminal of this amplifier 105 to the output side via a diode 106. . Further, one input side of the amplifier 105 is connected to one input side and an output side of the amplifier 108 via a resistor 107, and the output side of the amplifier 105 is connected to the other input side of the amplifier 108 via a diode 109. Connecting. The other input side of the amplifier 108 is grounded via a capacitor 110, and an analog switch 1 is connected across the capacitor 110.
Connect 11. An analog switch 111 is connected to the pulse generator 41.

This peak hold circuit 38 holds (retains) the peak value of the inter-electrode current value detected by the current detector 37,
This value is output to the current comparator 40, and the held peak value is reset by a reset pulse from the pulse generator 41.

The output side of the D/A converter 39 and the output side of the amplifier 108 of the peak hold circuit 38 are connected to a resistor 112, respectively.
．． 113 to the input side of the comparator 114 of the current comparator 40, and a diode 115, 116 is connected between each resistor 112, 113 and the comparator 114, respectively.
Connect. A resistor 117 is connected to the output side of the comparator 114, and one end of this resistor 117 is connected to a diode 11 that is grounded.
8 and is also connected to the terminal 119 of the CPU 46.

Each AND game of the gate circuit 43) 62-1 to 62-
n connects the temporary storage device 42a of the current waveform setting device 42 and the output terminal of the pulse generator 41, and the capacitor 29- Each of the discharge switches 31-1 to 31-n is driven to open and close in order to control charging and discharging of the switches 1 to 29-n.

That is, in order to discharge the charge of each capacitor 29-1 to 29-n to the discharge side as desired by the ON signal of the machining command pulse of the pulse generator 41, each AND gate 62-1
~62-n are all or partially turned on at the same time, and each transistor 51-1~ of discharge switch 31-1~31-n is turned on.
51-n to discharge charges from each of the capacitors 29-1 to 29-n, and to stop the discharge of charges from each of the capacitors 29-1 to 29-n by the off signal of the processing command pulse. Each of the AND gates 62-1 to 62
-n at the same time, each discharge switch 31-1 to 31
-n transistors 51-1 to 51-n are turned off to stop discharging charges from each capacitor 29-1 to 29-n.

The contact detector 47 is, for example, a constant current generator 4 as shown in FIG. a and a contact detection section 47b. That is, the constant current generating section 47a includes two amplifiers 121 and 122, a transistor 123, eight resistors 124 to 131, a variable resistor 132, a capacitor 133, and three diodes 134 to 136 (135 is Zener diode), etc., and is connected to a resistor 139 (for example, a low resistance of 3 Ω) between a terminal 137 connected to the workpiece 4 and a terminal 138 connected to the electrode 2, through a noise cutting filter to be described later. Provides constant current.

Further, the contact detection section 47b includes two coils 140,
(1) A capacitor 143 and series resistors 144 and 145 with one end grounded are connected to one end of the coil 140, and the series resistor 144 is connected to one end of the coil 140.
．． The divided voltage obtained by 145 is supplied to one input side of an amplifier 147 via a resistor 146. One input side of this amplifier 147 is grounded via a capacitor 148. The other input side of the amplifier 147 is connected to its output side via a resistor 149 and grounded via a resistor 150. The output side of the amplifier 147 is connected to the amplifier 1
One input side of the amplifier 151 is connected to a power supply via a variable resistor 152 and a resistor 153.

The output side of the amplifier 151 is connected to an FF via a resistor 154.
155, and a resistor 156.
is connected to the input side of gate 157 via. The output side of this gate 157 is connected to a buzzer terminal 158, and when the electrode 2 comes into contact with the workpiece 4, an alarm is issued by a buzzer or the like (not shown). The trigger terminal of the FF 155 is grounded through a capacitor 159 and a diode 160, and
The D terminal is pulled up to the power supply by a resistor 161, and a capacitor 1 with one end grounded is connected to the resistor 161.
Connect 62. One output side of FF155 is resistor 16
3 to the input side of a gate 1640, and the output side of this gate 164 is connected to a photocoupler 166 which is connected to the power supply by a resistor 165. The output side of the photocoupler 166 is connected to a transistor 167, and the collector and emitter of this transistor 167 are connected to the terminal 1 of the CPU 46.
Connect to 68 and 169 respectively. Note that the terminal 170 is a terminal of the CPU 46 for resetting the FF 155.

This touch detector 47 constantly supplies a constant current to a resistor 139 connected between the terminals 137 and 138 by a constant current generator 47a, and when the electrode 2 and the workpiece 4 come into contact, the contact between the terminals 137 and 138 is detected. The abnormal voltage value when a short circuit occurs is detected by the contact detection section 47b, and the signal is sent to the terminal 16.
8. Output from 169 to CPU 46, and also output from terminal 1
58, an alarm is emitted from a buzzer or the like.

The input device 13 of the electrolytic finishing processing apparatus 10 inputs information such as the material of the workpiece 4, the processing area S, the finishing allowance and the grade of dimensional accuracy, the pulse width of the supplied pulse current and the number of times of kneading (one pulse or every few pulses). The number of times of supply per machining, electrode gap, etc. are input, and these signals are output to the motor drive control section 9 and the machining condition control section 10 of the control device 12.

The electrolytic solution filtering device 14 filters an electrolytic solution containing electrolytic products generated during processing, and is configured as shown in FIG. 6, for example. That is, the electrolyte filtration device 14 is
The return electrolyte containing a large amount of electrolytic products from the solenoid valve 17
1, a centrifugal separator 174 that pumps up the electrolytic solution in the dirty tank 172 with a pump 173 and centrifuges it, and an electrolytic solution that does not contain the electrolyzed products separated by the centrifugal separator 174. A clean tank 175 that stores liquid and this clean tank 1
75 and includes a heater 183 and a fan (not shown) rotated by a motor 184.
76, a pump 177 for pumping up the electrolyte from the clean tank 175, and a pump 177 for pumping up the electrolyte from the clean tank 175, and a pump 177 for pumping up the electrolyte from the clean tank 175, and a pump 177 for pumping up the electrolyte from the clean tank 175, and a pump 177 for pumping up the electrolyte from the clean tank 175, and a pump 177 for pumping up the electrolyte from the clean tank 175, and a pump 177 for pumping up the electrolyte from the clean tank 175, and a pump 177 for pumping up the electrolyte from the clean tank 175, and a pump 177 for pumping up the electrolyte from the clean tank 175.
Solenoid valve 1 for supplying to the processing tank 15 after passing through 78
79, an electromagnetic valve 181 for ejecting the electrolytic solution passed through the filter 178 into the gap between the electrode 2 and the workpiece 4 by a blowing nozzle 180, and removing electrolytic products generated in the gap; It consists of a throttle valve 182 and the like that returns the electrolyte that has passed through the filter 178 to the liquid temperature regulator 175.

In addition, 185.186 in Fig. 6 is the pump 173.177.
The motor that drives the motor, 187.188 is the dirty tank 1
72 is an upper limit float switch and a lower limit float switch for detecting the liquid level, 189 is a float switch for detecting the liquid level in the processing tank 15, and 190 is a motor for driving the centrifuge 174.

Electrolyte flow control section 11 that controls this electrolyte filtration device 14
is for supplying an electrolytic solution into the machining tank 15 based on a control signal from the machining condition control unit IO, and for eliminating electrolytic products generated between the electrode surface 2a and the workpiece surface 4a during machining. Then, solenoid valves 179 and 181 are installed so that clean electrolyte (temperature-adjusted electrolyte that has passed through filter 178) is spouted between electrode 2 and workpiece 4 by jet nozzle 180.
, pumps 173, 177, etc., which will be explained below.

First, the electrolytic solution containing the electrolytic products in the processing tank 15 is discharged into the dirty tank 172 by an overflow pipe (not shown) and by actuating the solenoid valve 171 in response to a signal from the electrolytic solution flow control section 11. . The liquid level in the dirty tank 172 is detected by the upper and lower float switches 187 and 18, and the signals thereof are input to the electrolyte flow control section 11. When the liquid level in the dirty tank 172 reaches a predetermined value, the electrolytic solution flow control unit 11 controls the float switches 187 and 188 to indicate whether the liquid level is above or below.
At some point in time, a drive signal is output to the motor 185 of the pump 173 to pump up the electrolyte in the dirty tank 172 and send it to the centrifuge 174.

In the centrifugal separator 174, a motor 190 rotates in response to a control signal from the electrolyte flow control section 11, and the centrifugal separator 174 separates the electrolyte. Then, the electrolytic solution that has been separated and does not contain electrolytic products is stored in the liquid temperature regulator 176, where it is adjusted to a reference liquid temperature. At this time, if the temperature of the centrifuged electrolyte is below the reference temperature, the heater 183 is energized by the control signal of the electrolyte flow control device 11 to heat the electrolyte, and if the temperature of the electrolyte exceeds the reference temperature, is the electrolyte flow control section 11
The motor 184 is rotated by the control signal, and the electrolyte is cooled by the fan, so that the temperature of the electrolyte is always constant.

The temperature-adjusted electrolytic solution is stored in the clean tank 175. Then, the electrolytic solution pumped up by the pump 177 and passed through the filter 178 is transferred to the electromagnetic valve 179 by a control signal from the electrolytic solution flow control section 11 when starting processing.
is activated to supply a predetermined amount into the machining tank 15, and during machining, the solenoid valve 181 is intermittently raised by the control signal from the electrolyte flow control unit 11, for example, every - or several times. It is operated in synchronization with the operating electrode 2, and is ejected from the ejection nozzle 180 into the gap between the electrode 2 and the workpiece 4,
Eliminate electrolysis products in the gap. Note that the pump 177 is constantly operating during processing to pump up the electrolyte in the clean tank 175, but if the electrolyte is not operating, the electrolyte is pumped through the liquid temperature regulator 176 via the stop valve 182.
returned inside.

Note that the supply of the electrolyte is not limited to the above embodiment, and for example, first and second cylinders connected in series are provided, and the first cylinder is supplied with the electrolyte to the processing tank 15 side and the clean tank 175 side. In addition to providing a pair of reverse flow valves to prevent backflow, a compressor is connected to the second cylinder, and the compressor operates the second cylinder to operate the first cylinder. The sucked electrolyte may be jetted out between the electrode 2 and the workpiece 4.

Next, an example of the finishing operation performed by the electrolytic finishing apparatus 1 will be explained with reference to the flowchart shown in FIG.

During finishing, the electrode 2 used for electrical discharge machining of the workpiece 4, or the remainder cut out by wire-cut electrical discharge machining, is fixed as the electrode 2 to the lower end of the electrode fixing device 30 rod 16, Fix the workpieces 4 to the workpiece fixing device 5 (200)
b. The machining area S of the workpiece 4, the pulse width t Onl to t On3 of the supplied pulse current, using the input device 13;
Parameters such as the number of machining times N1, N2, electrode gap δ, etc. are input (201). Then, the electrode 2 is lowered to bring the electrode surface 2a into contact with the surface to be processed 4a (202), and the contact detector 47 detects the position, which is set as the origin A.

Next, the solenoid valve 179 is operated to supply electrolyte from the clean tank 175 into the processing tank 15 (203), and when the float switch 189 is operated, the electrode 2 is raised to maintain the initial electrode gap δ. Set electrode 2 at the position (
204), and when the electrolytic solution fills between the electrode surface 2a and the surface to be processed 4a and the electrolytic solution is stationary (meaning the state where the flow and movement of the electrolytic solution has almost stopped) (205), the first machining (-th (206).

If this judgment (206) is YES, that is, if this is the first machining, a predetermined peak current density corresponding to the machining area S of the workpiece 4 is transmitted from the power supply 8 by the control signal of the machining condition control unit 100. A single pulse current (hereinafter referred to as a first pulse current) for improving surface roughness having a predetermined pulse width ton in fpt is supplied (20?) between the electrode 2 and the workpiece 4.

Then, when a pulse current is supplied between the electrodes, the current detector 37 detects the inter-electrode current value o (208).
L/, the peak hold circuit 38 holds the peak value, and the CPU 46 calculates the lower limit current value ■1 from this peak value and parameters related to the properties such as the machining area S of the workpiece 4 manually input (209) L/ , is set in the current setting device 45. In addition, the calculation of the lower limit current value ■1 in this case is as follows:
For example, 11=IoXK3 (N3 is a constant of 1 or less).

Then, a single pulse current that is the same as the first pulse current is supplied between the electrodes (210), and the current value between the electrodes Ii at that time.
is detected (211). When the inter-electrode current value Ii is detected, the motor 20 is driven by the signal from the motor drive control section 9 to raise the electrode 2 (212), separating the electrode surface 2a from the workpiece surface 4a, and increasing the electrode surface 2a. The electrolyte filtering device 1 removes the electrolytic products eluted between the
4, the electrolytic solution is ejected (213) from the ejection nozzle 180 and removed.

After removing the electrolytic products, the electrode 2 is lowered (214) to bring the electrode surface 2a into contact with the surface to be processed 4a, the contact detector 47 detects the position, and this position and the origin A are connected. C
The PU 46 compares and measures the machining depth (215). The first pulse current has a peak current density ip1 of 15 A/cm2, a pulse width of 70nl of 4 msec, a jpt of 100A/cm2, and a tOni of 10
It has been experimentally confirmed that a pulse of 0 m5ec can significantly improve the surface roughness of the processed surface 4a whose processing area is 1 cm2 to 300 cm2.

Then, the machining depth measured in step (215) and the preset setting value are compared (216). If the machining depth does not reach a predetermined difference (for example, 1 μm) from the set value, step (211) ) is the lower limit current value 11 calculated in step (209) or less (217) b, if 1i<II (N
O) returns to step (204). In this case, since the step (206) is the second processing, the result is No, and the process returns to step (210>).

If YES in step (21?), that is, if the inter-electrode current value fi becomes lower limit current value 11 or less, the current comparator 40 outputs a signal to the CPU 46, and this signal causes the CPU 46 to set the charging voltage setting device. 44 and current waveform setting device 4
A single pulse for oxide film removal having a predetermined pulse width tOn2 with a peak current density jllz higher than the first pulse current and a pulse current supplied from the power supply device 8. The current is switched to the current (hereinafter referred to as second pulse current) (218), and the electrode 2 is raised to set it at the same position as in the step (204) (219). In this case, the electrode 2 and the workpiece 40
The gap becomes larger as processing progresses.

Then, the electrolytic solution between the electrode surface 2a and the processed surface 4a remains stationary (
220) L/, the second pulse current is supplied between the electrode 2 and the workpiece 4 (221) L/, the oxide film etc. generated on the workpiece surface 4a is peeled off from the workpiece surface 4a, and the electrode 2 is raised (222) and the electrolytic solution is ejected into the gap (223) b to remove the electrolytic solution containing the peeled oxide film etc. from the gap.

Then, the electrode 2 is lowered (224) and it is determined whether or not the predetermined number of machining is N1 (225).
If NO in step 225), the process returns to step (219), and processing using the second pulse current is performed a predetermined number of times N1.

If the determination (225) is YES, the pulse current supplied from the power supply device 8 is switched to the first pulse current (226), that is, the peak current density is reduced, and the process proceeds to step (204'). Continue the transfer finishing process. Note that this second pulse current has a peak current density of 5 to IOA/cm2 and a pulse width of 10 to 15 m.
When the machining depth becomes within a predetermined difference from the set value through this series of machining in which the value obtained by adding sec A single pulse current (hereinafter referred to as the third pulse current) for forming a glossy surface has a predetermined peak current density lp3 and a predetermined pulse width t on3, which is a pulse current supplied from the power supply device 8 according to the processing area S. ) (227). Then, with this third pulse current, steps (219) to (22) described above are performed.
5') Repeat the same process a predetermined number of times N2228)
~(234), complete all finishing operations (235)
'). This third pulse current has a peak current density ip
3 is 30-50A/cm2, pulse width is 20-60m
Although 5 ec is optimal, the same conditions as the second pulse current can also be used.

Note that the detection of the timing to switch the pulse current in step (216) is not limited to detection by comparing the machining depth and the set value described above, but also by calculating the amount of glue per unit area from the machining allowance to the end of machining, for example. Detection can also be controlled using the lever value.

Further, in the above embodiment, a case was explained in which a single pulse was used as the first to third pulse currents.
It is also possible to use pulse trains that provide multiple single pulses in succession. Furthermore, in the above embodiment, in order to eliminate electrolytic products after supplying a predetermined pulse current,
Although the electrode 2 has been raised once, if the electrode 2 is provided with one or more electrolyte jet holes or suction holes, the electrode 2 is not raised and the electrode 2 is moved to the position set at the initial electrode gap. In a fixed state, the electrolytic solution can be ejected or sucked from the ejection hole by appropriate means to remove the electrolytic products.

Further, in the above embodiment, the machining area of the workpiece 4 is input and set using the input device 13, but for example, by supplying a reference voltage between the machining electrodes and detecting the peak current value between the machining electrodes at that time, The CPU 46 can also automatically calculate and set the value using this peak current value and a conversion formula obtained through experiments in advance.

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

Machining example 1> Electrode Pure copper workpiece material Tool steel Surface area of workpiece surface 25 cm2 Electrode gap 0.1 mm Machining fluid Sodium nitrate solution (concentration 40%)
) 1st pulse current peak current density 15A/cm2 Pulse width 4m5ec 2nd pulse current peak current density 25A/cm2 Pulse width
20'm5ec 3rd pulse current peak current density 48 A/cm m2 pulse width
40m5ec Finished surface roughness Rmax: 1μm or less Finished surface
Machining example 2 for mirror-like glossy surface Electrode Pure copper Workpiece material Tool steel Surface area of workpiece surface 10m2 Electrode gap 0.1mm Machining fluid Sodium nitrate solution (concentration 40%)
) 1st pulse current peak current density 60A/crn2 On time 5m5ec 2nd pulse current peak current density 65A/crn2 Pulse width 15m5ec 3rd pulse current peak current density 48 A/crn2 On time
40m5ec Finished surface roughness Rmax: 1μm or less Finished surface,
Mirror-like glossy surface As described above, in the above embodiment, the switching to the high current density pulse current for removing the oxide film is performed by detecting the decrease in the inter-electrode current value due to the formation of the oxide film. Regardless of the shape of the workpiece, the size of the machining area, etc., the pulse current can be switched so that the degree of oxide film formation is always the same, and the oxide film formed on the workpiece surface 4a can be reliably removed. Surface roughness can be improved in a short time without being affected by the coating. It has been experimentally confirmed that the current value between the machining electrodes that decreases due to the formation of an oxide film is approximately proportional to the 0.2 power of the machining area, with the initial machining current value as a reference.

In the above embodiment, the lower limit current value was automatically calculated based on the inter-electrode current value obtained by the first pulse current supply, but the present invention is not limited thereto; for example, in step (201), the lower limit current value A lower limit current value corresponding to the machining area S of the workpiece is calculated and inputted in advance by the device 13,
The current setting device 45 of the CPU 46 may be set, that is, steps (206) to (209) in FIG. 7 may be omitted.

The lower limit current value 11 in this case is calculated, for example, from the known machining area S and the peak current density j[+ determined in advance by experiment according to this machining surface fff S, the total current I ( =SX i p+) is determined, and from this total current ■, it is calculated as I+=I XK3 (K3 is a constant of 1 or less).

9. In the above embodiment, only the inter-electrode current value due to the first pulse current was detected, but for example, the inter-electrode current value due to the second and third pulse currents may be detected, and this current value and the setting The current value may be compared with the current value, and based on the comparison result, the current may be switched to the first pulse current or the finishing process may be terminated.

Generally speaking, in the above embodiments, the current density was explained as the peak current density, but it goes without saying that the average current density may be used as the current density, and the present invention is not limited to the field of mold processing. Slight internal stress on the surface due to mechanical processing has become a problem, such as finishing processing of silicon single crystal or gallium histobase materials for semiconductor production, and mirror finishing of aluminum disks for magnetic storage devices using single crystal diamond. It can also be applied to finishing processing in the field. Furthermore, in conjunction with automatic conveyance equipment,
Of course, it is also possible to use it for finishing processing after heat treatment of mass-produced hypoid cars and the like.

[Effects of the Invention] Since the first and second inventions of this application are constructed as described above, they produce the following effects.

(First invention) Detecting the current value between the machining areas based on the pulsed current supplied between the machining areas, comparing the current value between the machining areas and a set current value set based on the properties of the workpiece, etc., and detecting the comparison result. Based on this, in order to increase or decrease the current density of the pulsed current, it is possible to switch to a pulsed current with a high current density while keeping the degree of oxide film generated during machining to improve surface roughness always the same. It can be removed reliably, the surface roughness of the processed surface can be improved in a short time and with high precision, and a mirror-like glossy surface can be easily obtained.

(Second invention) Since the lower limit current value is automatically calculated and set based on the machining current value at the initial stage of machining, input settings are made one by one according to the properties such as the shape of the workpiece and the size of the machining area. There is no need to do this, and work efficiency can be improved.

[Brief explanation of the drawing]

Fig. 1 is a front view of an electrolytic finishing apparatus capable of carrying out the present invention, Fig. 2 is a block diagram of the apparatus, Fig. 3 is a block diagram of its main parts, and Fig. 4 is a circuit configuration diagram of the main parts. , FIG. 5 is a circuit configuration diagram of a contact detector of the same device, FIG. 6 is a schematic configuration diagram of an electrolyte filtration device of the same device, and FIG. 7 is a flowchart showing an example of finishing operation. 1... Electrolytic finishing processing device, 2... Electrode, 4...
Workpiece, 8... Power supply device-9... Motor drive control section, 1O... Machining condition control section, 11... Electrolyte flow control section, 12... Control device, 13... Input device, 14... Electrolyte filtration device, 37... Current detector, 38... Peak hold circuit, 44... Charging voltage setter, 45... Current setting device, 46... CP
U. 1st blade/72 24 Fig. 2

Claims (2)

[Claims] (1) A finishing method using electrolytic machining, which includes the following steps: A. A workpiece and an electrode having an electrode surface patterned after the surface of the workpiece are placed opposite each other via a stationary electrolyte,
Supplying a pulsed current having a predetermined current density between the poles. B. Detecting a current value between electrodes based on this pulse current. C. Comparing this machining current value with a predetermined current value set according to the properties of the workpiece, and increasing or decreasing the current density of the pulsed current based on the comparison result. D. Supplying the increased or decreased pulse current between the electrodes. (2) A finishing method using electrolytic machining, which includes the following steps: B. A workpiece and an electrode having an electrode surface patterned after the surface of the workpiece are placed opposite each other via a stationary electrolyte,
Supplying a pulsed current having a predetermined current density between the poles. B. A step of detecting a current value between electrodes based on this pulse current. C. At the beginning of machining, a lower limit current value is set based on the machining current value and the properties of the workpiece, and during machining, the machining current value and the lower limit current value are compared, and increasing or decreasing the current density of the pulsed current based on the comparison result;