JPS6171921A - Method of finishing surface - Google Patents

Abstract

PURPOSE:To enable a mirror surface to be precisely finished for a short time in the surface working of a mirror surface metal mold for molding an optical element by pressing a pellet type working tool for fixing cathode grains against a workpiece of anode to supply current thereto in electrolyte for moving said tool relative to the workpiece. CONSTITUTION:A conductive workpiece 2 is fixedly held by a workpiece holding means 4. A rod body 6 has a spherical end conforming to a semispherical recess provided in the holding means 4. A plurality of working tools 8 are fixedly held by a working tool holding means 10 and bonded to the convex spherical surface with synthetic resin system adhesives 12. Also, the holding means 10 is secured fixedly to a base body 14 to rotate about the axis X. Around the base body 14 is formed a electrolytic tank by a side wall 16 in which electrolyte 18 is contained. The positive pole of a DC stabilizing source 20 is connected to the rod body 6 and the negative pole is connected to the base body 14 through a brush 22. In working, the base body 14 is rotated while the rod body 6 is swung horizontally.

Description

[Detailed description of the invention] [Technical field] The present invention relates to a method of surface processing a conductive material.

[Prior Art] Mechanical methods, chemical methods, or electrical methods are used for surface processing of various metal materials, particularly for mirror-finishing the surfaces. Specific examples of this type of processing include optical elements (e.g. lenses or prisms, etc.)
A mirror-finished mold for molding can be exemplified. Since such molds must maintain a predetermined dimensional accuracy under changing conditions of temperature and pressure, extremely hard materials such as stainless steel, super steel, and various alloy steels are used as materials.

Conventionally, in surface processing of molds made of such hard materials, many steps were required to achieve a mirror surface due to the hardness of the materials. For example, after forming the surface into a predetermined shape and size by electric discharge application]-, rough lapping is performed with 'M# diamond paste with a particle size of about 40 to 25 pL,
Next, wrap with 'Mt and diamond paste with a particle size of about 16-6cm, and then wrap it with a particle size of 3-1p.
The mirror finish was done with - grade free diamond paste. In other examples, rough grinding is performed with a #80 to #200 diamond grindstone, and then #400 to #200 diamond grindstone is used for rough grinding.
Perform semi-finish grinding with a 1000 diamond grindstone,
Furthermore, mirror polishing was performed using a diamond grindstone with a roughness of 2,000 to 3,000, and finally the chain was finished with a polylens. In this way, the conventional method requires a large number of steps, and each time the process changes, it is necessary to change tools, clean the workpiece, and in some cases re-set the workpiece to another machine. Therefore, so-called set-up takes time, and this causes cost savings.

[Object of the Invention] In view of the above-mentioned prior art, the present invention provides a surface finish that allows precision mirror finishing in a short period of time through a relatively simple process.
The purpose is to provide a method for processing

[Summary of the Invention] According to the present invention, the above object is to prevent electrolysis between a conductive workpiece and a conductive machining tool holding means that holds a plurality of abrasive-fixed pellet type machining tools. A workpiece characterized in that a liquid is made to exist, the workpiece is energized with the workpiece as an anode and the workpiece holding means as a cathode, while the workpiece is brought into pressure contact with the workpiece and moves relative to the workpiece. This is achieved by a method of finishing the surface of a pressurized object.

[Embodiments of the Invention] Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view showing an embodiment of the processing method of the present invention.

In the figure, 2 is a workpiece, and the workpiece 2 is a conductor.
[Have sex.] 4 is an L stage for holding the workpiece 2, and this means also has conductivity.

The lower surface of the workpiece 2 is to be mirror-finished, and the lower surface and side surfaces are fixedly held by the holding means 4. Reference numeral 6 designates a rod for transmitting the driving force for the movement of the holding means 4, and the tip thereof is spherical, and is adapted to the four hemispherical parts provided on the - side of the holding means 4.

8 is a pellet which is a processing tool, and the pellet 8 has a grain size of, for example, 5 to 10. degree of diamond powder or C
It is obtained by mixing abrasive grains such as BN (cubic boron nitride) powder with metal powders such as Sn, Cu or Fe in a specified mixing ratio, stirring, compressing, heating and sintering. Pellet-type processing tools are widely used in general glass processing. A large number of machining tools 8 are fixedly held on two surfaces of a conductive machining tool holding means 10. The upper surface of the holding means IO has a convex spherical shape, and the processing tool 8 is adhered onto the convex spherical surface with a non-conductive synthetic resin adhesive 12. The upper surfaces of all the processing tools 8 are machined into curved surfaces having a predetermined radius of curvature R, and the upper bodies of the processing tools 8 are arranged so that their upper surfaces are located on a spherical surface with a radius of curvature H. ing. The holding means 10 is fixed to the conductive base 14 by screws provided at the bottom thereof. The base 14
can rotate around the axis of rotational symmetry X of the spherical surface of −1− radius H. A cylindrical side wall 1 is provided around the base 14.
6 are formed, and these form an electrolytic cell. The electrolytic cell contains an electrolytic solution 18 such as a NaNO3 aqueous solution or a KNO3 aqueous solution.

Reference numeral 20 denotes a direct VIE stabilized power supply, the positive electrode of which is connected to the conductive rod 6, and the negative electrode of which is brought into contact with the outer peripheral surface of the rotating shaft at the bottom of the body 14 via a sliding brush 22. ing.

During machining, the base body 14 is driven to rotate around the axis X, and the rod 6 is horizontally swung by the base body 11 (these driving means are not shown here). FIG. 2 is a plan view showing the relationship between the workpiece 2, the processing tool 8, and its holding means 10 at this time. The machining tool holding means 10 rotates at a constant angular velocity in the direction of arrow A, while the workpiece 2 swings on the machining tool 8 in the direction of arrow B with a constant amplitude. This kind of relative interlocking is the same as that in general processing such as lens polishing, and the workpiece 2 thereby rotates in the direction of arrow C, and the contact between the workpiece 2 and the tool 8 is controlled by the workpiece. Averaged over the entire surface.

The workpiece is removed by electrolysis on the part of the surface of the workpiece 2 that does not come into contact with the tool 8, while the passivation film that is generated as the electrolysis progresses on the part of the surface of the workpiece 2 that comes into contact with the tool 8. Removal is performed using fixed abrasive grains.

The processing speed of electrolytic processing, that is, the removal speed of the workpiece can be increased by increasing the current density. However, as the current density increases, the surface roughness of the machined surface increases. Therefore, it is preferable to use a high current density in the early stage of processing when emphasis is placed on electrolytic removal efficiency, and to use a low current density in the latter stage of processing when emphasis is placed on mirror finish of the surface. For example, as shown in Figure 3(a), by continuously decreasing the current density as the machining time progresses, a sufficient machining speed can be obtained at the beginning of machining, and at the end of machining. A sufficient mirror finish can be obtained. Alternatively, the current density may be gradually reduced stepwise at certain time intervals as shown in FIG. 3(b). Furthermore, the current density may be pulsed as shown in FIG. 3(C). In this case, there is a time period during which no current is applied, during which only mechanical removal of the workpiece by the processing tool 8 is performed.

In the example below (1), the case where there is a sufficient workpiece and the machining tool is below is illustrated, but conversely, it is also possible to have a machining tool above and the workpiece below. A specific example of the case is shown in the 4th IN. In this example,
A processing tool holding means 10 is located at the lower part of the rod 6, and is applied to the lower surface of the holding means 10 through an adhesive 12.
8 are fixedly held. The object 2 to be processed is fixedly held by a holding means 4 fixed to a base body 14.

In addition, in the following embodiment -1-, the processing tool is a pellet-type processing tool in which abrasive grains such as diamond are sintered with metal.
However, as a processing tool, it is also possible to use a tool in which abrasive grains such as diamond are fixed with non-conductive resin, and in this case, it is necessary to consider electrical insulation using adhesive. do not have.

Further, in the above embodiments, the electrolytic solution is present only in the electrolytic cell, but the electrolytic solution may be pumped and circulated from outside using a pump or the like. This removes the electrolyte, which becomes dirty as the addition progresses, outside the electrolytic tank. The electrolyte can be maintained at a predetermined concentration by appropriately cleaning the electrolyte in H.

[Effects of the Invention] According to the present invention as described in (2) below, it is possible to achieve good results in a relatively short time, at low cost, and without the need for exchanging tools, replacing machines, or cleaning workpieces during machining. A surface with a mirror finish can be obtained.

[Brief explanation of the drawing]

1 and 4 are cross-sectional views showing an embodiment of the method of the present invention, FIG. 2 is a plan view showing the relationship between a workpiece and a processing tool, and FIGS. ) and (C) are graphs showing changes in current density. 2: Workpiece 4: Workpiece holding means 6: Rod body
8 Processing tool 10: Processing tool holding means 12: Adhesive 14: Base
16: Side wall 18: Electrolyte 20: DC stabilized power supply 22: Sliding brush Fig. 3 (a) Time Fig. 3 (b) Time Fig. 3 (C) NuA Fig. 4 Harumun

Claims (2)

[Claims] (1) An electrolytic solution is caused to exist between the conductive workpiece and a conductive processing tool holding means which holds a plurality of abrasive fixed pellet type processing tools, and the workpiece is used as an anode and the processing tool is held. A method for finishing the surface of a workpiece, characterized in that a means is used as a cathode to energize the workpiece, while a processing tool is brought into pressure contact with the workpiece and moved relative to the workpiece. (2) The surface finishing method of item 1, in which the applied current is gradually reduced as the processing progresses.