JPH08229817A - Grinding method and device - Google Patents

Abstract

PURPOSE: To execute dressing of a conductive grinding wheel in forming a free curvature surface by grinding work using the grinding wheel. CONSTITUTION: A work 20 is installed on a work table 10, so a free curvature surface 22 is formed by grinding work to the work 20 by a rotary grinding wheel 40 installed on a spindle 30. The grinding wheel 40 is a conductive grinding wheel such as a metal bond grinding wheel, and a grinding wheel correcting device 60 is provided to face the grinding wheel 40. The grinding wheel correcting device 60 is an in-process electrolytic dressing device, and electrolytic dressing is executed to only an action surface 50 of the grinding wheel 40.

Description

Detailed Description of the Invention

[0001]

[Industrial application] This technology is a mold for grinding solid materials such as metal, glass, and ceramics with precision and small surface roughness, for example, optical parts and press or injection molding of optical parts. In the industrial field of manufacturing, especially during the grinding process of the mold having a free-form surface shape called so-called non-axisymmetric that does not have a rotation target axis, so-called in-process dressing grinding that sharpens the grindstone by electrolytic dressing, The present invention relates to a technique for shaping a grindstone by electric discharge machining.

[0002]

2. Description of the Related Art Conventionally, as a method for precisely processing a solid material such as metal, glass or ceramics with a small surface roughness, cutting has been mainly performed. That is, this is a method in which an extremely hard single crystal diamond is used as a tool, a workpiece made of a soft metal such as aluminum, copper, or brass is rotated at a high speed to cause the tool to cut, and this is cut. However, in these cutting processes, iron-based and cobalt-based materials react with diamond to increase tool wear. Alternatively, it is difficult to perform accurate machining with materials that are difficult to cut, such as ceramics and cemented carbide. Therefore, for example, when manufacturing an optical component by injection molding of resin or press working of glass, if it is desired to process the mold, durability with these soft materials,
It could not be used due to heat resistance.

Therefore, as a material that is often used for these purposes, an iron-based material is pre-processed, an electroless NiP alloy plating layer is formed on this material, and this layer is precisely cut with a diamond tool. There is a way to do it. According to this method, since the NiP alloy is harder than the soft metal, it can be used as a mold for resin injection molding. However, even in such a method, the adhesion, wear resistance, and durability of the NiP alloy plated layer become a problem, and the formation of pinholes when forming the plated layer becomes a big problem, which can be easily used. I could not say.

Therefore, when machining a material having high wear resistance and durability such as carbon steel, stainless steel, cemented carbide or a hard and brittle material such as ceramic glass, a grinding tool is used instead of the diamond tool. Is often used. That is, it is a method of rotating a workpiece, cutting a grindstone rotated at a high speed, and grinding. However, as a drawback in the grinding process, there are problems such as deterioration of accuracy due to wear of the grindstone and clogging of the grindstone. In particular, when a fine grindstone is used to reduce the surface roughness, clogging occurs extremely easily, which deteriorates workability and accuracy.

Further, conventionally, the shape of the workpiece is limited to the shape to be rotated because the workpiece is rotated and the cutting or grinding is performed while positioning the tool. Therefore, it has begun to realize a three-dimensional free surface shape by scanning a grindstone with three axes of XYZ.

In normal cutting, such machining cannot be performed because the tool itself does not move. Since this method is carried out by grinding, there is a problem of wear of the grindstone, especially when a fine grindstone used to reduce the surface roughness is used, the wear becomes large, and the grindstone of the grinding The problem of clogging deteriorates workability and accuracy. These grinding problems are applied to a commonly used grindstone called a resin bond grindstone in which the binder of the abrasive grains is made of resin.

In response to such a problem, in recent years, a method of grinding a metal-bonded fine abrasive grain grinding wheel while electrolytically dressing in-process has been developed. However, the effect of contributing to an increase in processing speed has been recognized. In this method, the grinding liquid is used as an electrolytic solution, and an electrolytic electrode is provided to cause electrolysis between the grinding stone and the abrasive, and the grinding wastes clogged mainly between the abrasive grains are electrolytically eluted to perform dressing. In this way, a good processing state is maintained.

[0008]

However, in electrolytic dressing, not only grinding dust, which is the main cause of clogging of the metal bond grindstone, but also metal, which is the binder of the abrasive grains, is eluted, so long-term machining is required. Doing so caused the shape of the grindstone to collapse. In particular, when machining a so-called non-axis symmetrical shape in which there is no axis to be rotated by grinding, it is necessary to perform high-precision shape machining while scanning the grindstone under XYZ three-axis control. The machining time is twice to 100 times, but in such a case, the influence of the electrolytic dressing on the shape of the grindstone cannot be ignored, and it is extremely difficult to perform high-precision machining by electrolytic dressing using a metal bond grindstone. there were. The present invention provides a technique for solving the above-mentioned problems.

[0009]

As a basic means of the present invention, the in-process electrolytic dressing means is arranged at a position different from the working surface of the grindstone with respect to the object to be processed, and the in-process electrolytic dressing means is provided only on the working surface of the grindstone. Electrolytic dressing is performed.

[0010]

In the free-form curved surface grinding process, only the portion where the grindstone working surface grinds the workpiece is electrolytically dressed. At this time, the position where the grindstone is acting is calculated in advance according to the progress of processing, and electrolytic dressing is performed while moving the electrolytic dressing electrode and the flat plate electrode along the outer circumference of the grindstone to that position. Further, the wire electrode and the wire electric discharge grinding head calculate beforehand the change in the length of the tangential arc of the grindstone working surface due to the change in the R of the workpiece, and perform the electrolytic dressing by accurately swinging by the tangential arc length. . Further, since the wire electrode runs along the wire guide, the wear of the electrode can be ignored and the shape of the grindstone can be maintained for a long time.

[0011]

FIG. 1 is a front view showing a first embodiment of the present invention,
FIG. 2 is a plan view. The grinding machine indicated by reference numeral 1 as a whole is
It has a table 10 for holding a work (workpiece) 20 and a spindle 30 of a machining head which is controlled to move in three-dimensional three-axis (X, Y, Z) directions with respect to the table 10. The work 20 is, for example, a die for pressing or injection molding, and its surface 22 is ground to a mirror surface.

When the shape of the surface 22 of the work 20 has a rotation target axis, the table 10 holding the work 20 can be rotated about the axis C ₁ to grind the work 20. . However, work 2
When the shape of the surface 22 of 0 is a so-called non-axisymmetric shape (free-form surface shape) that does not have a rotational symmetry axis, the work 2
It is necessary to fix the table holding 0 and move the grinding head side along the non-axisymmetric surface to be machined to perform the grinding process.

The grinding apparatus 1 of the present invention employs a structure in which the machining head is controlled in the three X, Y, and Z directions. The main shaft 30 rotatably supported by the processing head is rotationally driven in the direction of arrow A by a motor (not shown). A grindstone 40 is attached to the tip of the spindle 30. Whetstone 40
For example, the grinding surface 42 is formed into an arc surface, and has a shape suitable for processing a free-form surface.

Therefore, while rotating the main shaft 30, X, Y,
The surface 22 of the work 20 is processed by controlling the movement in the Z-axis direction. The shape of the surface 22 of the workpiece 20, for example, indicated by the trajectory P ₁ is on Figure 1, the trajectory P ₂ are on Figure 2
It is a free-form surface shape indicated by. In this grinding process, the grinding surface 42 of the grindstone 42 and the surface 22 of the work 20 come into contact with each other at the processing portion 50. This processed portion 50 is formed on the circumferential surface having the deformation R ₁ on the grinding surface 42 of the grindstone 40. This processed portion actually has a ring shape having a certain width dimension.

The coordinate position of the grindstone 40 of the processing section 50 on the X-axis changes depending on the surface 22 of the work 20. Therefore, in the present invention, by applying electrolytic dressing as a means for correcting the grindstone only to the machined portion of the grindstone, clogging of the workpiece is prevented, and electrolysis of metal bonds other than the machined portion is avoided. is there.

The electrolytic dressing device 60 includes a table 6
5 and a dressing electrode 62 attached to the table 65. The position of this table 65 is controlled by a three-axis control device with R interpolation. The control device of the grinding device 1 recognizes the current coordinate position of the processing unit 50 based on the shape of the grindstone and the shape of the processing surface of the work.

Therefore, by controlling the table 65 of the electrolytic dressing device 60 so as to correspond to the coordinate position of the processed portion 50 of the grindstone 40, the dressing electrode 62 is made to face the processed portion 50 of the grindstone 40 and the processed portion 50 of the grindstone 40 is controlled. In-process electrolytic dressing can be applied only to the periphery. Therefore, it is possible to prevent the clogging of the grindstone by eluting only the grinding dust attached to the processed portion of the grindstone and to continue the efficient grinding.

FIG. 3 is a front view showing a second embodiment of the present invention, and FIG. 4 is a plan view. Grinding device 1A according to the present embodiment
Similar to the grinding apparatus 1 of the first embodiment, has a grinding head including a table 10 on which a work 20 is mounted and a spindle 30 that holds a grindstone 40 and grinds it. The grinding head is controlled to move along the three axes of X, Y and Z, and the work 20
Surface 22 is mirror-finished to a free surface. A wire discharge device 80 is provided on the opposite side of the work table 10 across the main shaft 30.

The wire electric discharge machine 80 has a table 85 whose movement is controlled along the three axes of X, Y and Z, and a stand 84 which is erected on the table 85.
A disk-shaped wire guide 82 is provided above the shaft 81.
Can be mounted rotatably. Disk-shaped wire guide 8
2 has a groove 83 on the peripheral surface, and the wire 86 is guided by the groove 83.

The wire 86 is sent in the direction of the arrow F by a wire supply device (not shown), and discharged by the power supply device. Tip 86a of wire 86
When the processing part 50 of the grindstone 40 is approached, an electric discharge is generated between the grindstone 40 and the electrically conductive grindstone 40.
Electrical discharge machining. Grinding wheel processing part 5 by this electric discharge machining
0 melts, and the grinding dust accumulated between the abrasive grains is removed. The conductive grindstone 40 is, for example, a metal bond grindstone,
As the abrasive grains, high hardness fine abrasive grains such as tungsten carbide, CBN and diamond are used.

By performing wire electric discharge machining, the metal bond is also melted at the same time, and the abrasive grains are also removed and removed.
Therefore, the grinding surface 42 of the metal bond grindstone 40 is dressed (sharpened), and truing (shape creation) of the grinding surface 42 is possible by selecting the electric discharge machining conditions. Therefore, in the grinding apparatus of the present invention, dressing can be achieved on the same machine together with truing of a metal bond grindstone, and efficient grinding can be achieved.

[0022]

As described above, in free-form curved surface grinding, electrolytic dressing is performed only on the portion where the grindstone working surface is grinding the workpiece, which is a main cause of so-called clogging. Since only the grinding dust is electrolyzed, the effect of minimizing the deformation of the grindstone shape can be achieved and high precision machining becomes possible. In addition to the dressing of the grindstone, truing can be performed by providing a wire discharge grinding device as the grindstone repairing device.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of the present invention.

FIG. 2 is a plan view of an embodiment of the present invention.

FIG. 3 is a side view of another embodiment of the present invention.

FIG. 4 is a plan view of another embodiment of the present invention.

[Explanation of symbols]

10 Work Table, 20 Workpiece, 30 Grindstone Spindle, 40 Grinding Wheel, 60 Electrolytic Dressing Device, 62 Electrolytic Dressing Electrode, 65 Electrolytic Dressing Device Table, 80 Wire Electric Discharge Machine, 82 Wire Guide, 86 Wire.

Claims (5)

[Claims] 1. A method for grinding a free-form surface using a grindstone on a work piece, wherein a whetstone correcting means is arranged at a position different from the position where the working surface of the grindstone acts on the work piece, and A grinding method characterized by correcting only a surface. 2. The grinding method according to claim 1, wherein the grindstone correcting means is in-process electrolytic dressing means. 3. The grinding method according to claim 1, wherein the grindstone correcting means is wire discharge grinding means. 4. A work table for holding a workpiece,
The grinding head having a spindle for holding and rotating the grindstone, the in-process electrolytic dressing device arranged at a position different from the working surface of the grindstone, and the work table and the grinding head It is equipped with a three-dimensional control device and a device for three-dimensionally controlling the in-process electrolytic dressing device relative to the grinding head.The control device is installed at a position facing the working surface of the grindstone with respect to the workpiece. A grinding machine characterized by controlling a process electrolytic dressing machine. 5. A work table for holding a workpiece,
A grinding head having a spindle for holding and rotating the grindstone, a wire discharge grinding device arranged at a position different from the working surface of the grindstone, and a work table and a grinding head It is equipped with an original control device and a device for three-dimensionally controlling the wire electric discharge grinding device relative to the grinding head. The control device is equipped with a wire electric discharge grinding device at a position facing the working surface of the grindstone for the workpiece. A grinding machine characterized by controlling the machine.