JPH07100258B2 - Electrolytic finishing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic finishing method, and more particularly to an electrolytic finishing method capable of controlling a machining amount of a work and obtaining high machining accuracy.

[Prior Art] Conventionally, an electric discharge machined work and an electrode having an electrode surface that follows the machined surface of the work are arranged in a stationary electrolytic solution so as to face each other with a predetermined gap, and a single electrode is provided between the electrodes. While supplying the processing pulse of, the electrolyte is intermittently ejected into the gap,
As an electrolytic finishing method for finishing the work while removing the machining waste in the gap, for example, Japanese Patent Laid-Open No. 63-114815
The one disclosed in the publication is known.

[Problems to be Solved by the Invention] By the way, in this electrolytic finishing method, it is difficult to accurately control the amount of machining of the work, and there is a disadvantage that high machining accuracy cannot be obtained.

In other words, in this electrolytic finishing method, a monograph obtained by an experiment (trial machining) was performed in order to confirm the roughness of the electric discharge machined surface of the workpiece during finishing and obtain the required roughness surface. From, enter the target machining amount. Further, an arithmetic expression is obtained from the electrochemical equivalent of each material and the data of the processing efficiency by the experiment, and the arithmetic expression is used to calculate the Coulomb amount per unit area corresponding to the input processing amount, and based on the clone amount. To set the machining count.

Then, normally, if the processing is performed under the same conditions as in the experiment, the processing accuracy (dimensional accuracy) falls within about ± 5% with respect to an arbitrary processing amount. However, it is difficult to perform the actual processing under the same conditions as in the experiment due to changes in the concentration, temperature, pH, etc. of the electrolytic solution. Further, since the surface shape of the work is complicated, it is difficult to calculate the accurate area thereof, and the error of the input area deviates the amount of Coulomb per unit area, which adversely affects the processing accuracy. In addition, it is difficult to perform the conditions for removing the electrolyte in the gap by the flushing operation at the same level as in the experiment, and for workpieces with complicated shapes, it is difficult to reliably remove them over the entire surface, resulting in machining efficiency. Is deteriorated and the actual machining amount is smaller than the input machining amount, and it is not possible to obtain high machining accuracy such as the target dimensional accuracy cannot be obtained.

Therefore, an object of the present invention is to eliminate the above-mentioned inconvenience, and in particular, to realize an electrolytic finishing processing method capable of controlling the processing amount of a work and obtaining high processing accuracy.

[Means for Solving the Problem] In order to achieve this object, the first invention of the present application provides a work machined into a predetermined shape and an electrode having an electrode surface that follows the machined surface of the work. In the one in which the workpiece is finish-machined while being opposed to each other at a predetermined gap in the electrolytic solution and supplying a machining pulse between the electrodes, and supplying a jet flow of the electrolytic solution to the gap to eliminate machining chips, A step of setting a target machining amount (D) of the work and a machining number (N) of the finishing process necessary to obtain the machining amount; and when the finishing process reaches a predetermined machining number, A step of measuring the machining amount of the work and calculating the machining efficiency based on the machining amount, the calculated machining efficiency, the machining amount (D) and the number of machining times (N)
And a predetermined machining efficiency based on the above, and a step of increasing or decreasing the current density of the machining pulse according to the comparison result. The second invention is the first invention, wherein the calculated When the processing efficiency is out of a predetermined range with respect to the predetermined processing efficiency, the method further comprises a step of increasing or decreasing the number of finishing processes.

[Operation] According to the configuration of the first invention of this application, the target machining amount D and the number of finishing processes N for obtaining the machining amount D are performed.
And are set, and the actual machining amount Δdi of the workpiece is measured when the finishing machining reaches the predetermined machining number Ni. Then, the actual machining efficiency Ki is calculated based on the measured machining amount Δdi and the machining frequency Ni, and the machining efficiency Ki is compared with the machining efficiency K based on the machining frequency N and the machining amount D. When the actual machining efficiency Ki is out of the predetermined range with respect to the predetermined machining efficiency K, the current density of the machining pulse is increased or decreased, and the next finishing machining is performed by this machining pulse. As a result, the processing amount of the work is brought close to the target processing amount D.

Further, according to the configuration of the second invention, when the calculated machining efficiency Ki is out of the predetermined range with respect to the predetermined machining efficiency K, the current density is changed and the number of machining of the next finishing machining is calculated. The machining amount of the work is changed to a predetermined machining amount D in a shorter time.

[Embodiment] An embodiment of the first and second inventions of this application will be described in detail and specifically with reference to the drawings.

In FIG. 1, an electrolytic finishing apparatus 1 capable of carrying out the inventions of this application includes an electrode fixing device 3 for fixing an electrode 2.
Work fixing device 5 for fixing work 4, servo motor 6
Control unit 1 including a drive conversion unit 7 for converting the rotational motion of the above into a reciprocating motion, a power supply device 8 for generating a machining pulse, a head drive control unit 9, a machining condition control unit 10, an electrolytic solution flow control unit 11, and the like.
2. An input device 13 for inputting various data, an electrolytic solution filtering device 14 for filtering an electrolytic solution, a processing tank 15 and the like.

The electrode fixing device 3 has a lower end of a rod 16 provided under the electrode fixing device 3 and an electrode 2 made of, for example, pure copper or graphite.
Is fixed so that the electrode surface 2a and the processed surface 4a of the work 4 maintain a uniform gap 17 in the three-dimensional direction. The electrode fixing device 3 moves up and down by the rotation of the servo motor 6 according to the control signal of the head drive control unit 9, and the electrode surface 2a and the processed surface 4a.
And are set to a predetermined gap 17. The work fixing device 5 is a table made of high-insulating granite or ceramics, and the work 4 processed by die-cutting electric discharge machining is fixed to the upper surface of the work fixing device 5 by a set jig or the like not shown.
In FIG. 1, reference numeral 18 is a jet nozzle for jetting a clean electrolytic solution into the gap 17.

The input device 13 uses the material and the processing area of the work 4, a target processing amount D (hereinafter referred to as a designated processing amount), and the processing amount D.
The total number of finishing operations N, which will be described later, required to obtain
The conditions of the machining pulse, the initial electrode gap δ, etc. are input, and these signals are output to the head drive controller 9 and the machining condition controller 10 of the controller 12.

Further, the electrolytic solution filtering device 14 is for filtering an electrolytic solution containing an electrolytic product generated in the processing, based on a control signal of the electrolytic solution flow control unit 11, electrolyzes the processing tank 15 at the start of processing. In addition to supplying the liquid, in order to eliminate the machining chips generated in the gap 17 between the electrode 2 and the workpiece 4 during machining, the gap 17 is cleaned in synchronization with the electrode 2 which moves upward every time a machining pulse is supplied. The electrolytic solution is ejected through the ejection nozzle 18.

A power supply device 8 for supplying a machining pulse of a predetermined condition between the electrode 2 and the workpiece 4 and the machining condition control unit 10 for controlling the power supply device 8 are configured as shown in FIG. 2, for example. .

That is, the power supply device 8 includes a DC power supply unit 19 and a charging / discharging unit 20, and the DC power supply unit 19 includes a transformer 21 and a rectifier 22. The transformer 21 lowers the voltage to a predetermined value, and the rectifier 22
To obtain a direct current, and a condenser 23-1 described later
~ 23-n.

The charging / discharging unit 20 also includes a plurality of capacitors 23-1 to 23-n for discharging electric charges between the electrodes and each of these capacitors 23-1 to 23-n.
diodes 24-1 to 24-n connected to n to prevent the reverse flow of charges to the DC power supply unit 19 side, discharge switches 25-1 to 25-n opened and closed to discharge charges to the discharge side, and It comprises a charging switch 26 and the like for cutting off the power source from the DC power source unit 19 in order to charge each of the capacitors 23-1 to 23-n in a predetermined manner.

The processing condition control unit 10 detects the charging voltage value of the capacitors 23-1 to 23-n, the voltage value detected by the voltage detector 27, and the output from the D / A converter 28. A voltage comparator 29 for comparing the value with a value, a charge detector 30 for detecting completion and start of charging of the capacitors 23-1 to 23-n by an output signal from the voltage comparator 29, and a discharge between the electrodes. Current detector 31 for detecting the current value of the electric charge, a peak hold circuit 32 for holding the peak value of the current value detected by this current detector 31, and the peak value and D / A held by this peak hold circuit 32. A current comparator 34 for comparing the output value of the converter 33 and a pulse generator 37 for generating a pulse having a predetermined time width.
And the discharge switches 25-1 according to an input signal from the current waveform setting unit 38 that sets the current waveform of the electric charge discharged between
To a gate circuit 35 for outputting an opening / closing drive signal to 25-n, and a charging voltage for setting a charging voltage value to be supplied to each of the capacitors 23-1 to 23-n and outputting the signal to the D / A converter 28. Set the value of the current flowing between the setter 36 and the pole and set the signal to the D /
A current setting device 39 that outputs to the A converter 33, and a CPU 40 that calculates and processes processing conditions and the like based on the input signals from each circuit
And a contact detector 41 for detecting the contact between the electrode 2 and the work 4. In the figure, reference numeral 42 is a diode that prevents the discharge switches 25-1 to 25-n from being destroyed by the back electromotive force.

As shown in FIG. 3, the contact detector 41 includes a reference power source 43 for supplying a reference voltage below the decomposition voltage between the electrodes, a resistor 44 for current detection, and resistors 45, 46 at both ends of the resistor 44, respectively. Amplifier 47, which connects its input side via
It is composed of a comparator 49 and the like for comparing the output signal of 47 and the signal set by the variable resistor 48. Reference numeral 50 in FIG. 3 is a resistance for current detection of the current detector 31. The decomposition voltage is a voltage at which the electrode reaction of the electric double layer composed of the work 4, the electrolytic solution, and the electrode 2 starts.

The contact detector 41 detects the inter-electrode current based on the reference voltage supplied from the reference power source 43, compares the inter-electrode current with the reference current set by the variable resistor 48, and the inter-electrode current is the reference. When it becomes larger than the current, it outputs a contact detection signal to the CPU 40.

Next, the first invention of this application will be described based on the flowcharts of FIGS.

During the finishing process, for example, the electrode 2 used in the die-sinking electric discharge machining of the work 4 is fixed to the lower end of the rod 16 of the electrode fixing device 3, and the work 4 is fixed (60) to the work fixing device 5, respectively. After the centering of the electrode 2 and the work 4, the following data and the like are input (61) by the input device 13.

D: Specified amount of machining N: Total number of machining of finishing machining 2 to obtain the designated amount of machining δ: Initial electrode gap n: Number of machining per finishing machining 1 N ₁ : Machining per finishing machining 2 When the electrolytic solution such as sodium nitrate is supplied to the processing tank 15 and the automatic finishing operation is started (62), the CPU4
At 0, a predetermined machining pulse is supplied from the power supply device 8 to perform the finishing machining 1 (63).

This finishing process 1 (63), as shown in FIG.
Is set to a position where the initial electrode gap δ is maintained (63-1),
A single machining pulse with a peak current density of ip ₁ and a pulse width of t ₁ is supplied between the electrodes (63-2). When this processing pulse is turned off, the electrode 2 is raised (63-3) and the gap
The electrolytic solution is jetted from the jet nozzle 18 to the nozzle 17 (63-4) to remove machining chips, such as electrolytic products generated by the supply of the machining pulse, from the gap 17 and lower the electrode 2 (63-
5) and reset to the position set in the step (63-1). And the counter a of the CPU 40 (not shown)
Is cleared (63-6), and the count number Ca of the counter a is
Is incremented by 1 (63-7), and it is judged (63-8) whether or not the counted number Ca is a predetermined number, that is, the number of times of machining n input and set in the step (61), and this judgment (63-
If NO in step 8), the process returns to step (63-2), and steps (63-2) to (6) are performed until YES is obtained in the determination (63-8).
Repeat 3-7).

The machining pulse in the finishing machining 1 is to remove the oxide film and the like generated and adhered to the machining surface 4a of the work 4 by supplying a machining pulse for improving the surface roughness described later. The current density ip ₁ is set to 30 to 50 A / cm ² , the pulse width t ₁ is set to ²⁰ msec or more, and the processing number n is set to 3 to 10.

When the oxide film or the like on the machined surface 4a of the work 4 is removed by the finish machining 1 (63), it is judged whether the machining by the finish machining 1 is the first machining (64), and if it is the first machining, this judgment (64) ) YES, and jumps to step (71) described later. In addition, if finishing machining 1 is performed twice or more, the judgment (64) will be NO, and the machining amount Δdi of the work 4 will be measured (65).
To do.

This step (65) will be described in detail with reference to FIG. First, in order to measure the machining amount Δdz in the Z-axis direction (65-1), a counter b (not shown) of the CPU 40 is cleared (65-1).
a) and add +1 (65-1) to the count number Cb of the counter b.
b) and lower the electrode 2 by a predetermined distance t, for example, 1 μm (65-1
c) Allow. Then, the presence or absence of the contact detection signal from the contact detector 41 is judged (65-1d), and this judgment (65-1d) is made.
If NO, return to step (65-1b) and make a judgment (65-1b).
Steps (65-1b) to (65-1c) until YES in step d)
repeat. When the judgment (65-1d) is YES, the moving amount Lz of the electrode 2 is calculated (65-1e) by the following formula (1), and CP is calculated.
Store in U40.

Lz = Cb × t (1) where Cb is the count number of the counter b. The amount of movement Lz is, for example, the lowest point on the Z axis of the electrode 2 set in the step (63-1) as the reference point A, that is, the origin (0, 0, 0) of the XYZ axis. Remember, electrode 2 is work 4
It is calculated based on the coordinates of the Z-axis of the reference point A when touching.

When the movement amount Lz is calculated, the machining amount Δdz in the Z-axis direction is calculated based on this value by the following equation (2) (65-1f).
To do.

Δdz = (Cb × t) −δ (2) where δ is the initial electrode gap set by the input device 13.

When the processing amount Δdz is calculated, the moving amount Lz (= Cb ×
Then, the electrode 2 is set to the initial position (65-1g), and the process proceeds to the step (65-2) for measuring the machining amount Δdx in the X-axis direction.

Step (65-2) includes steps (65-1a) to (65-1a).
-1f) The same as steps (65-2a) to (65-2f), first calculate the machining amount Δdx (+) in the plus (+) direction of the X axis, and then in both (+) and (-) directions. Is judged (65-2g) and NO is returned, and step (65-2g) is executed again.
Processing amount Δd in the (-) direction of the X axis according to a) to (65-2f)
Calculate x (-). And the machining amount in both directions Δdx
When (+) and Δdx (−) are calculated, the machining amount Δdx in the X-axis direction is calculated (65-2h) by the following equation (3).

Δdx = (Δd × (+) + Δd × (−)) / 2 (3) When the machining amount Δdx is calculated, the electrode 2 is moved by the movement amount Lx (−) in the (+) direction and set to the initial position. (65-2i),
A series of steps for measuring the machining amount Δdx in the X-axis direction (65-
2) is ended.

When the machining amount Δdx in the X-axis direction is calculated in this step (65-2), the machining amount Δdy in the Y-axis direction is calculated by the same method as that in step (65-2) (the description thereof is omitted).
Is measured (65-3). And the machining amount of each axis Δdz, Δ
Based on dx and Δdy, the machining amount Δdi is calculated by the following equation (4).
Is calculated (65-4).

Δdi = (Δdz + Δdx + Δdy) / 3 (4) The above is the step (65) of calculating the processing amount Δdi.

When the machining amount Δdi is calculated in this step (65), the cumulative machining amount d is calculated based on the machining amount Δdi (6
6) Do. Then, this cumulative machining amount d is determined by the above step (6
It is judged (67) whether or not the designated processing amount D input and set in 1) is within the predetermined value r (67), and if this judgment (67) is NO, that is, the cumulative processing amount d has not reached D ± r. In this case, the machining efficiency Ki is calculated (68) by the following equation (5) based on the machining amount Δdi calculated in step (65) and the number of machining times N ₁ .

Ki = Δdi / N ₁ (5) When the machining efficiency Ki is calculated, the machining efficiency Ki is the predetermined machining efficiency K, that is, the designated machining amount D input in step (61) and this machining amount D. It is judged (69) whether or not the processing efficiency K calculated from the predetermined number of times of processing N necessary for the above is within the range of the predetermined value s.

As shown in FIG. 7, this judgment (69) is based on the fact that the measured actual machining efficiency Ki (dotted line a in the figure) is within a predetermined range with respect to the ideal machining efficiency straight line A obtained through experiments or the like. It is to determine whether or not there is, and in this determination (69) YES
In case of NO, the process proceeds to step (71), and in case of NO, that is, when the actual machining efficiency Ki is not within the range of K ± s, the peak current density ip ₂ of the machining pulse of finishing machining 2 (71) is increased or decreased. Let This peak current density ip ₂ should be
When the machining efficiency Ki is K + s or more by the control signal of 40,
Reduce the setting voltage of the charging voltage setting device 36 to improve processing efficiency.
When Ki is K-s or less, the setting voltage is increased.

Then, the finishing pulse 2 (71) is performed a predetermined number of times N ₁ by the same step as the finishing symbol 1 (63) by the machining pulse having the increased or decreased peak current density ip ₂ . The machining pulse in the finishing machining 2 has, for example, a peak current density ip ₂ of 30 to 50 A / cm ² and a pulse on time t ₂ of
The pulse off time toff _{2 of the} pulse is 10 msec or less, and a pulse train of 5 consecutive single pulses with 100 to 500 msec is used.
Of course, it is also possible to use a single pulse similar to the finishing process 1.

When finishing process 2 is performed N ₁ times a predetermined number of times, step (6
Return to 3) and perform finishing process 1. Then, each step is repeated, and when the cumulative machining amount d is within the range of the predetermined value r with respect to the designated machining amount D in the judgment (67), the judgment (67) is executed.
The result is YES and the finishing process is completed (72).

As described above, in this embodiment, after the oxide film and the like formed on the machined surface 4a of the work 4 is removed by the finish machining 1, the actual machining amount Δdi is measured, and the measured machining amount Δdi is calculated. Based on this, the machining efficiency Ki is calculated, and this Ki is compared with a predetermined machining efficiency K, and the machining efficiency Ki is K ±.
When the value is out of the range of s, the peak current density ip ₂ of the machining pulse of the finishing machining 2 for improving the surface roughness is increased / decreased and changed, so that the finishing machining can be performed while controlling the machining amount.
The processing amount can be brought close to the designated processing amount D, and the dimensional accuracy of the work 4 can be improved. Also, the actual processing efficiency Ki
Is smaller than the predetermined machining efficiency K, the peak current density of the machining pulse is increased, so that the machining time can be shortened. Further, even when the calculation accuracy of the processing area S of the processing surface 4a of the work 4 is poor, the calculated actual processing efficiency
This can be corrected by Ki, and a processing pulse having a predetermined peak current density ip ₂ according to the processing area S can be supplied.

FIG. 8 is a flow chart showing an embodiment of the second invention of this application. The feature of this embodiment is that in the judgment (69), when the machining efficiency Ki is outside the range of K ± s, that is, the judgment (69). )
When NO in NO, the peak current ip2 is changed (70), and the machining number Ni + 1 is calculated (73) based on the measured machining amount Δdi, and this is set (74) as the machining number of finishing machining 2 (71). In point. Since other steps are the same as those in FIG. 4, the same reference numerals are given and detailed description thereof will be omitted.

As shown in FIG. 9, the calculation of the machining number Ni + 1 in step (73) is carried out by the following equation (6) from the measured machining amount Δdi, for example, Δd ₂ and the machining number N ₁ (73). .

Ni + 1 = Δd × (N ₁ / Δd ₂ ) (6) However, Δd is a predetermined processing amount (for example, 10 μm) obtained when the number of processing is N ₁ . In the case of this embodiment, in the determination (69), it is determined whether or not the calculated machining efficiency Ki is within a predetermined range t with respect to the predetermined machining efficiency K. The range t is, for example, −50. Set to%.

As described above, in this embodiment, the peak current density ip ₂ is increased or decreased based on the machining efficiency Ki, and the machining number Ni + 1 of the next finishing machining 2 is calculated and set. When K is less than Ks, ip ₂ is increased and the number of machining operations Ni + 1 for the next finishing is also increased. Therefore, when the machining efficiency is low, the machining pulse is increased with the increased peak current density ip ₂ Finishing processing can be performed without frequently measuring Δdi, and the processing efficiency Ki can approach the predetermined processing efficiency K in a short time, and the processing time of the entire finishing processing can be shortened.

In each of the above-mentioned examples, the processing amount was measured by Z
Although the measurement is performed in three directions of the axis, the X-axis, and the Y-axis, the present invention is not limited to this, and for example, only the Z-axis may be measured.

Further, in each of the above embodiments, the electrode was moved when measuring the processing amount, but the work may be moved, and the flowcharts in the above embodiments are merely examples, and the flowcharts are combined. It goes without saying that appropriate changes can be made without departing from the gist of each invention of the application.

[Effects of the Invention] Since the inventions of this application are configured as described above, the following effects are achieved.

(First Invention) When finishing machining reaches a predetermined number of machining times, the actual machining amount is measured to calculate the machining efficiency, and the machining pulse current density is increased or decreased based on this machining efficiency. It is possible to perform finishing processing while controlling the above, and it is possible to improve the dimensional accuracy of the work.

If the actual machining efficiency is less than the specified machining efficiency, the peak current density of the machining pulse is increased.
The finishing time can be shortened.

Even if the calculation accuracy of the machining area of the work is inferior, it can be corrected by measuring the actual machining efficiency, and it is possible to supply a predetermined machining pulse according to the machining area. The surface is obtained.

(Second Invention) Since the current density is increased / decreased and the number of times of the next finishing process is increased / decreased on the basis of the calculated processing efficiency, the entire finishing process time can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrolytic finishing apparatus according to the present invention, FIG. 2 is a block diagram of the same part, FIG. 3 is a circuit diagram of the contact detector, and FIG. 4 is one of the first invention. FIG. 5 is a flowchart showing an embodiment, FIG. 5 and FIG. 6 are flowcharts of the main part, and FIG. 7 is a diagram showing the relationship between the number of times of machining and the amount of machining,
FIG. 9 is a flowchart showing an embodiment of the second invention, and FIG. 9 is a diagram showing the relationship between the number of times of machining and the amount of machining. 1 ... Electrolytic finishing device, 2 ... Electrode, 2a ... Electrode surface, 4 ... Work piece, 4a ... Machining surface, 8 ... Power supply device, 9 ... Head drive control unit, 10 ... Machining condition control Part 11 ... Electrolyte flow control part, 12 ... Control device, 18 ... Jet nozzle, 40 ... CPU, 41 ... Contact detector.

Claims (2)

[Claims] 1. A. A workpiece machined into a predetermined shape and an electrode having an electrode surface following the machined surface of the workpiece are arranged in an electrolytic solution so as to face each other with a predetermined gap, and a machining pulse is supplied between the gaps of the workpiece and the gap. In the one for finishing the work while supplying the jet of the electrolytic solution to the machine to remove the machining waste, A step of setting a target machining amount (D) of the work and a number of finishing processes (N) necessary to obtain the machining amount; Measuring a machining amount of the work when the finishing machining reaches a predetermined machining frequency, and calculating machining efficiency based on the machining amount; d. Comparing the calculated machining efficiency with a predetermined machining efficiency based on the machining amount (D) and the number of machining times (N), and increasing or decreasing the current density of the machining pulse according to the comparison result. Electrolytic finishing method. 2. The electrolytic finishing method according to claim 1, wherein: When the calculated machining efficiency is out of a predetermined range with respect to a predetermined machining efficiency, a step of increasing or decreasing the number of times of the finishing machining is performed, the electrolytic finishing process method.