JPH0453627A - High precision electrolytic finishing method - Google Patents

Abstract

PURPOSE:To minimize a corner R on an angled curved surface as well as to secure a mirrorlike lustrous surface and such by supplying a work pulse current to an interval between an electrode and a work and then separating them from each other, and supplying a fresh electrolyte to the interval between the electrode and the work, while shifting the electrode in an X-Y direction. CONSTITUTION:An electrode 2 is lowered and a clearance 19 in the Z-axis direction is kept in the specified value, while this electrode 2 is further shifted in the X-axis direction or Y-axis direction, and thereby a clearance between the electrode 2 and a work 4 in the Y-axis direction is set to the specified value. When a pulse current is supplied, the electrode 2 is once put back to the X-axis direction, and afterward, the electrode 2 is lifted up, and simultaneously an electrolyte is spouted out of an injection nozzle 18 and such operation as eliminating an electrolytic product is repeated. Thus, even in a work surface with an orthogonal or obtuse angular curved surface, such electrolytic machining that realizes an accurate form transcription can be performed, thus a highly accurate surface quality is obtainable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrolytic finishing method, and more particularly to an electrolytic finishing method for finishing a three-dimensionally shaped work surface in a short time and with high precision.

[Prior art] As a conventional electrolytic processing method, for example, Japanese Patent Application Laid-Open No. 1986-1978
According to Publication No. 722, the gap between the electrode and the workpiece is filled with an electrolytic solution such as sodium nitrate or sodium chloride, and a pulsed current is passed between the electrode and the workpiece to give the surface of the workpiece a mirror-like finish. is disclosed.

[Problems to be Solved by the Invention] This electrolytic machining method is difficult to solve in complicated three-dimensional bottom machining (machining of a material having a machining surface with a three-dimensional structure formed in the shape of a concave hole). The gap between the workpiece and the electrode, which has a contoured shape, is filled with an electrolytic solution, and the peak current density is set at 30 to 50 A/cm in the early stage of finishing.
2, the on time is set to 2 to 10 msec, and in the latter stage, the peak current density is set to 30 to 50/A cm2, and the on time is set to 20 to 60 msec. As a result, the surface roughness in the first stage of processing is improved, and a mirror-like glossy surface is obtained on the processed surface without impairing the surface roughness in the second stage of processing.

However, according to this method, there was no problem with smooth surface shapes, but when machining objects with right-angled or acute-angled partial shapes as shown in Fig. Even if a sharp corner R is formed, the minimum corner R is 0.2 in the electrolytic finishing process in the subsequent process.
There was an inconvenience that the finish was only about mmR.

On the other hand, according to Japanese Unexamined Patent Publication No. 54-1495, in order to perform equal clearance machining on the entire opposing surfaces of the electrode and the workpiece, energization is performed by moving the electrode and the workpiece relative to each other. is disclosed. However, the results did not change even in experiments using this method.

The reason for this is that electrolytic machining requires a gap of about 50 to 300 μm between the electrode and the workpiece, and the process tends to uniformly process opposing machining surfaces. is possible. That is, in electrolytic machining, when a pulse current is supplied with the electrode facing the workpiece, under high current density conditions (for example, 10 to 25 cm), when the gap is 110 μm and the predetermined machining energy is supplied, the gap is 40 μm. While the amount of machining can be obtained, the gap is 10
When machining energy is supplied under the same conditions as μm,
A processing amount of only about 20 μm can be obtained, and the processed surface is also rough and loses its shape. The reason for this is that electrolytic products and hydrogen gas are generated in the gaps during processing, inhibiting proper electrolytic action. Therefore, even in the case of Fig. 6, under standard machining conditions where the machining energy per unit area (current density The processing was not perfect.

[Purpose of the Invention] Therefore, the present invention eliminates the above-mentioned disadvantages, and in particular improves the corner radius of curved surfaces with angles to a minimum, and finishes a three-dimensionally shaped work surface in a short time and with high precision to create a mirror finish. The purpose of this invention is to realize a high-precision electrolytic finishing method that can obtain a glossy surface with a similar shape.

[Means for Solving the Problem] In order to achieve this object, the first invention of this application includes a step of disposing an electrode and a workpiece facing each other with a predetermined gap in an electrolytic solution, and a step of disposing an electrode and a workpiece facing each other with a predetermined gap between them. , a step of supplying a weak pulse current, a step of separating the electrode and the workpiece in order to widen the gap between them, and a step of supplying a new electrolyte solution between the electrode and the workpiece to remove electrolytic products. and a step of moving the electrode in the X-Y direction relative to the workpiece.

Further, a second invention provides a pulse current in the first invention,
It is characterized in that the voltage is 5.3 to 6.5V and the on time is 30 msec or less.

[Function] According to the invention of this application, the amount of electrolytic products generated and the amount of hydrogen gas generated per pulse current supply are small, so the gap between the electrode and the workpiece can be made smaller. , for example, when the gap is 10μm, the gap is 110μm.
Even if the machining energy conditions are such that a machining amount of only 2 μm can be obtained in the case of m, a machining amount of 20 μm can be obtained. As a result, the gap between the electrode and the workpiece can be made smaller than before, allowing precise curved surface transfer along the shape of the electrode.

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

1 and 2 show one embodiment of this invention.

In FIG. 1, an electrolytic finishing device 1 capable of carrying out the present invention includes an electrode fixing device 3 for fixing an electrode 2, a workpiece 4, and an electrode fixing device 3 for fixing an electrode 2.
A workpiece fixing device 5 that fixes the
A drive conversion section 7 that converts the rotational motion of the shaft motor 6 into reciprocating motion, a big unit 9 that moves the electrode fixing device 3 up and down by supplying air from an air supply device 8, a DC power supply section 10, and a charging/discharging section 11. A power supply device 12 that generates machining pulses, a motor drive control section 13, and a machining condition control section 1
4 and an electrolytic solution flow control section 15, an input device 17 for inputting various data etc. to the workpiece 4, filters the electrolytic solution, and jets out the filtered electrolytic solution through a jetting nozzle 18. As a result, the electrolytic solution filtration device 20 supplies a jet of electrolytic solution to the gap 19 between the electrode 2 and the workpiece 4, a processing tank 21, etc. are included.

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 22 provided at its lower part, with a gap such that the electrode surface 2a and the processed surface 4a of the workpiece 4 are spaced in a three-dimensional direction. Fix it so that it stays at 19. In this electrode fixing device 3, the Z-axis motor 6 rotates in response to a control signal from the motor drive control section 13, and this rotation is converted into vertical movement by the drive conversion section 7 to move up and down. The air supply device 8 is activated by the control signal 13, and air is supplied into the pick unit 9 to move it up and down. Note that the electrode fixing device 3 is driven by using one or both of the Z-axis motor 6 and the air supply device 8 at the same time, depending on processing conditions and the like.

The workpiece fixing device 5 is a table made of highly insulating granite or ceramics, and on its upper surface, for example, a setting jig (not shown) is used to hold the workpiece 4 subjected to die-carving electric discharge machining.
Secure with screws, etc.

A mechanism for controlling the relative positional relationship between the electrode 2 and the workpiece 4 to perform processing is configured as shown in FIG. 2, for example.

That is, the control device 16 includes an input device 17 and various sensors 2.
3 and performs control according to a predetermined program. This sensor 23 is conceptual and actually consists of multiple sensors, including liquid level detection, contact detection between the electrode and workpiece,
A general term for devices that perform functions such as electrolyte pH detection, machining depth detection, and pulse supply frequency detection.

The motor drive control unit 13 freely moves a table (not shown) supporting the electrode 2 to a predetermined position on the X-Y plane (front, rear, left and right directions) by driving an X-axis motor 24 and a Y-axis motor 25. It is moved to change and maintain the relative positional relationship with the workpiece 4. Further, the Z-axis motor 6 and the air supply device 8 are driven to move the electrode 2 up and down, so that a position where the gap 19 with the workpiece 4 is maintained at a predetermined value and a position where the two are separated are alternately obtained. There is.

Furthermore, the control device 16 stores the input machining conditions in a storage device 26, and displays the contents on a display device 27 for the operator's convenience. When the sensor 23 detects that the electrolytic machining has reached a predetermined amount, the machining condition control unit 14 displays a message to that effect.
The processing continues by issuing a signal to the power supply device 12 to supply a pulse current based on the new processing conditions. Processing is continued by automatically switching between the programmed processes, and finally, when the sensor 23 detects that a predetermined process has been completed, processing is terminated.

During that time, the electrode 2 rises and the gap 1 between the electrode 2 and the workpiece 4
When the gap 9 expands, the electrolytic solution is ejected from the ejection nozzle 18, and the electrolytic products generated in the gap 19 are removed. The electrolyte filtration device 20 that performs this function not only supplies the electrolyte based on the surface detection signal of the electrolyte from the sensor 23, but also sprays the electrolyte as the electrode 2 rises.
In order to prevent the electrolytic solution from becoming contaminated, the electrolytic product is filtered while the electrolytic solution is being circulated.

The control contents during processing are stored one by one in the storage device 26, and can be displayed on the display device 27 or printed out using a printer (not shown) for reconfirmation if necessary.

Next, an experiment showing the principle of the invention of this application will be explained with reference to FIG.

The electrode 2 has protrusions E1, E2, E3, and E4 that are approximately perpendicular to each other.
The workpiece 4 had a configuration with an inclined upper surface, and the gap between the two was set to be 10 μm in one example when the two were opposed to each other, and 110 μm on the opposite side. In such a relationship between the electrode 2 and the workpiece 4,
When a pulse current was supplied between the two, the results shown in FIG. 4 were obtained.

That is, Figure 4A shows the result of energization under the machining conditions learned from the conventional machining method, and Figure 4A shows the result of energization under the machining conditions of the invention of this application. be.

Wl, W2, W3, and W4 in FIGS. 4A and 4B are the ridges El, E2, E3 of the electrode 2 shown in FIG.
This is a concave groove indicating the amount of machining of depth T produced as a result of machining in the portion corresponding to E4.

In FIG. 4A, a pulse current was supplied under conventional machining conditions of so-called high current density. As a result, the machining gap is 110
Although the W1 part, which is μm, was processed extremely accurately, as the gap became smaller, the electrode shape transfer deteriorated, and in the W4 part, the roughness of the machined surface was added, making it impossible to put it into practical use. . From this, it is determined that it is not very desirable to reduce the gap between the electrode 2 and the workpiece 4 to 10011 m or less under the conventional machining conditions.

On the contrary, Figure 4A shows the machining results when the current value of the pulse current is decreased and the pulse ON time is also changed to shorten the electrode shape at the W4 portion where the gap is 10 μm. It is clear that while the shape is accurately transferred, as the gap becomes larger, the shape is not transferred. The current conditions in this case are approximately voltage 5.
3~6°5V, pulse width (application time) is 30msec
It was below. From this, if the current value is lowered, even if the gap 19 between the current 2 and the workpiece 4 is made smaller,
It has been found that electrolytic processing can be performed without damaging the processed shape.

In this case, the on-time of the pulse current will be set to a value as close to zero as possible in relation to the pursuit of shape accuracy, based on the size and shape of the workpiece at the practical stage, but it will be kept within the conventional normal range. For mold processing with a shape and precision of 1 to 30 msec is sufficient.

Based on the above findings, the inventor of this application has completed an electrolytic finishing method that can transfer the electrode shape with high precision. That is, when finishing a workpiece having a three-dimensional machined surface formed by electrical discharge machining, the first step is to supply a pulsed current under a relatively large energy condition. (Peak current density is 30-50A/Cm
2, the on time is set to 2 to 10 m5eC. ) As a result, the surface roughness is improved.

The second stage then provides pulsed current at higher energy conditions than the first stage. (The peak current density is 30
~50 A/cm2 and on time of 20 to 60 msec. ) As a result, the processed surface becomes a mirror-like glossy surface without impairing the surface roughness.

Note that machining at this second stage of current value setting is performed in the following third stage.
If a step of processing is performed, the fourth step is the subsequent process.
This also applies to stage processing.

If it is necessary because the shape has a bent portion, a pulse current is supplied in a third step with an energy smaller than that in the first step.

(The voltage applied between the electrode 2 and the workpiece 4 is set to 5.3 to 6.5V, lower than in the first stage, and the on time is 30V.
It should be less than msec. ) In this case, assuming that the area of the processed surface remains unchanged, the current density per unit area will be a much smaller value than in the first stage, but in reality, when estimated from the processing results, The current flows in a concentrated manner locally, and the machining area cannot be specified, so it cannot be determined as an average current density.

In this third stage, the electrode was moved relative to the workpiece in the XY plane to control the gap during machining to be reduced.

The operations at each stage are the same as before.
Only the third stage was corrected as follows. In other words, while lowering the electrode 2 to maintain the gap 19 in the X-axis direction at a predetermined value, the electrode 2 is further moved in the X-axis direction or the Y-axis direction, and the electrode 2 and the workpiece in the 4 is added to set the gap to a predetermined value. After the pulse current is supplied, the electrode 2 is returned to the X-axis or Y-axis direction, and then the electrode 2 is raised, and at the same time, the electrolytic solution is jetted from the jet nozzle 18 to eliminate the electrolytic products in the gap 19. . Then repeat the above operation.

To further explain this point based on FIG.
It is now possible to process a by making the gap 19 as close as 10 um, but in that case, the process has already been completed in the previous stage (the first stage and the second stage above). Since the width of the electrode 2 is relatively small with respect to the inner width of the workpiece 4, the electrode surface 2a and the processed surface 4a of the workpiece 4 cannot come close to each other unless the electrode 2 is moved laterally. . Therefore, in the third step, at least the electrode 2 is moved in the X-Y direction (front, rear, left, and right directions) with respect to the work 4, and the electrode surface 2-a and the workpiece surface of the work 4 are
It becomes necessary to adjust the gap between a and a. This is achieved by operating the X-axis motor 24 and Y-axis motor 25 using the motor drive control section 13.

As a result, as is clear from the comparison with the conventional method shown in Fig. 6, since the gap between the conventional method and the electrical discharge machined surface (indicated by the - dotted chain line) could not be reduced, the surface machined by electrolytic machining is almost the same as the electrical discharge machined surface. However, in the invention of this application, it was possible to obtain an electrolytic machined surface that was a modified electrical discharge machined surface, as shown in FIG.

In addition, in the above explanation, the electrode and the workpiece are positioned facing each other in the vertical direction, but if they are positioned horizontally,
It is also possible to easily eliminate electrolysis products between the two.

In that case, the Z-axis is horizontal, so the X-Y plane is
It is read as a plane perpendicular to the Z-axis (extending in the vertical and front-back directions).

[Effects of the Invention] Since the present invention is configured as described above, it has the following effects.

■Even if the surface to be machined has a curved surface at a right angle or an acute angle, electrolytic processing can be performed that achieves accurate shape transfer, and high-precision surface quality can be obtained.

■Using electrolytic processing that does not consume electrodes, the process includes surface roughness improvement processing to remove surface roughness (first stage), finishing processing to obtain a glossy surface (second stage), and high-precision die engraving (third stage).
step), and it has become possible to manufacture molds with three-dimensional curved surfaces without going through electric discharge machining.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electrolytic finishing apparatus that can carry out the electrolytic finishing method according to the present invention, FIG. 2 is a block diagram showing control details, and FIG. 3 is an experimental diagram showing the principle of this application. An explanatory diagram, FIG. 4 is an enlarged explanatory diagram of the work surface showing the results of the experiment, FIG. 5 is an explanatory diagram showing the situation of electrolytic machining according to the present invention, and FIG. 6 is an explanatory diagram showing the situation of conventional electrolytic machining. It is an explanatory diagram. l... Electrolytic finishing processing device, 2... Electrode, 4...
Workpiece, 12... Power supply device, 13... Motor drive control section, 14... Machining condition control section, 15... Electrolyte flow control section, 16... Control device, 17... Input Device,
23...Sensor, 26...Storage device, 27...Display device. Figure 1 Patent applicant Shizuoka Seiki Co., Ltd. Representative Shigeo Meiki Figure 2

Claims (2)

[Claims] (1) A high-precision electrolytic finishing method characterized by meeting the following requirements A to E. A. Placing the electrode and the workpiece facing each other with a predetermined gap in the electrolytic solution; B. Supplying a weak pulse current between the electrode and the workpiece; C. Enlarging the gap between the electrode and the workpiece. D. Supplying a new electrolytic solution between the electrode and the workpiece to remove electrolytic products; E. Positioning the electrode in the X-Y direction relative to the workpiece. The process of moving to. (2) The high-precision electrolytic finishing method according to claim (1), which satisfies the following requirements. F, the pulse current is 30V at a voltage of 5.3 to 6.5V.
The on time must be less than msec.