JP4420490B2 - ELID surface grinder electrode support apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode support apparatus and method for an ELID surface grinder that grinds a workpiece while performing electrolytic dressing.
[0002]
[Prior art]
Conventionally, a flat lapping machine has been mainly used to process a high-precision magnetic disk substrate. This flat lapping machine is a lapping machine of a double-sided simultaneous lapping system, for example, gears are cut around the fixture to which the workpiece is attached, meshed with the central and peripheral gears and rotated while the fixture rotates, Pressure is applied by a cylinder, and a free abrasive is interposed between a tool called a lapping (or lapping machine) and a workpiece, and machining is performed by relative movement between the lapping and the workpiece.
[0003]
However, the above-described conventional lapping apparatus (for example, a flat lapping machine) has a feature that high processing accuracy can be obtained with relatively simple equipment, but has the following problems.
(1) Since processing is performed using a free abrasive, the processing speed is very slow (1/10 or less of grinding), and processing takes time. For this reason, usually, a large facility is used to process a plurality of magnetic disk substrates at the same time, but the processing time per sheet is nevertheless long.
(2) Since the reference lapping machine is processed with high accuracy in advance and the workpiece is processed in accordance with this, if the accuracy of the lapping machine itself decreases due to wear or the like, the machining is required again. In this case, the “rubbing adjustment” is usually performed by rubbing the upper and lower lapping machines. However, this method makes the uneven part flat, but the perpendicularity to the rotation axis cannot be secured, and the parallelism of the workpiece after machining Decreases. In other words, with the constant pressure lap method, truing (rubbing adjustment) can be performed on the machine, but even if the flatness of the grindstone (lapping machine) is improved, the parallelism between the workpiece holding jig and the grindstone cannot be readjusted, so both sides of the workpiece The parallelism (thickness accuracy) cannot be improved by this adjustment.
[0004]
Furthermore, in recent years, hard disk damage, particularly motor damage, has frequently occurred. One cause of this is an unbalance in the thickness of the magnetic disk substrate. That is, the eccentric force generated by the unbalance of the magnetic disk substrate has a problem that the bearing life of the motor is reduced and the motor is damaged in a short time. Therefore, in order to increase the reliability of the hard disk, it is strongly desired to increase the parallelism (thickness accuracy) of the magnetic disk substrate more than before. However, when this is attempted to be achieved with the above-described conventional lapping machine, the processing time becomes longer and there is a problem that is not practical.
[0005]
In order to solve the various problems described above, inventors of the present invention, previously, "mirror finishing apparatus and method for magnetic disk substrates" - invented (Japanese Patent Application No. 10 136 198, unpublished) the applicant did. As schematically shown in FIG. 4, the present invention includes a metal bond grindstone 2 that rotates around a vertical axis Z1 and has a horizontal machining surface 2a, and a horizontal support surface 4a that faces the machining surface. The workpiece holding and rotating means 4 that rotates about the vertical axis Z2 and the metal bond grindstone as an anode, the electrode 6a that is non-contactingly facing the processed surface of the metal bond grindstone as a cathode, and between the two electrodes A voltage application means 6 for applying a pulsed voltage and a grinding liquid supply means 8 for supplying a conductive grinding liquid to the processed surface of the metal bond grindstone are provided. The work holding and rotating means 4 is a disc-shaped magnetic disk substrate 1. Alternatively, the disc-shaped truing grindstone is configured to be held and rotated in close contact with the support surface, and to be movable horizontally and vertically, whereby (A) the processing surface 2a of the metal bond grindstone is flat on the machine. Processed, then metal Simultaneously (B) grinding of the support surface 4a of the work holding and rotating means and (C) grinding of the magnetic disk substrate 1 attached to the work holding and rotating means while electrolytically dressing the grinding wheel. Is what you do. In this figure, reference numerals 3 and 5 denote driving devices.
[0006]
By this apparatus and method, the processing speed of the magnetic disk substrate can be greatly increased as compared with the conventional lapping apparatus, and the parallelism (thickness accuracy) and surface roughness of both surfaces can be increased more than before. It became so.
[0007]
[Problems to be solved by the invention]
In mirror-processing apparatus described above, the electrode 6a is against set in a non-contact on the processed surface 2a of the grinding wheel 2, and the gap for example 0.1 - must be set precisely within a range of 0.15 mm. Therefore, conventionally, the electrodes have been fixed horizontally by an electrode clamping device. However, since the grindstone gradually becomes thinner due to the electrolytic dressing, it was necessary to readjust the gap as needed. Further, not only re-adjustment with a shim or the like is required when the grindstone is worn, but also the gap needs to be adjusted each time when exchanging or cleaning the grindstone or removing the electrode. For this reason, there is a problem that these operations require time and the overall processing efficiency is lowered. Further, since this adjustment requires skill, there is a problem that the reproducibility of the gap is poor and the grinding performance is deteriorated when experience is insufficient.
[0008]
The present invention has been developed to solve such problems. That is, the object of the present invention is to make it possible to easily adjust the gap between the processing surface of the grindstone without requiring skill, and to eliminate the need for readjustment even when the grindstone is worn, replaced, or cleaned. An object of the present invention is to provide an electrode support apparatus and method for a surface grinder.
[0009]
[Means for Solving the Problems]
According to the present invention, there is provided an electrode support device for supporting an electrode (16a) opposite to a horizontal processing surface (10a) of a conductive grindstone (10) rotating about a vertical axis, wherein the electrode is moved up and down. An electrode guide (18) that is movably supported, an electrolytic solution supply means (20) that supplies an electrolytic solution between the electrode and the grindstone, and is mounted on the grindstone side of the electrode (16a). A contact prevention material (17) made of an insulating material thinner than the gap; and means for adjusting the gap between the electrode and the grindstone by flowing an electrolytic solution on the processed surface and lifting the electrode by hydroplaning. An electrode support device for an ELID surface grinder is provided.
[0010]
According to the present invention, there is also provided an electrode support method for supporting an electrode (16a) opposite to a horizontal processing surface (10a) of a conductive grindstone (10) rotating about a vertical axis, Is attached to the grindstone side of the electrode (16a), and a contact prevention material (17) made of an insulating material thinner than a desired gap between the electrode and the grindstone is attached to the electrode (16a). An electrode support method for an ELID surface grinder is provided, in which electrodes are lifted by planing and a predetermined gap is formed therebetween.
[0011]
According to the apparatus and method of the present invention, the electrode is supported by the electrode guide (18) so as to move up and down, and the electrolyte is supplied between the electrode and the grindstone by the electrolyte supply means (20), and the electrode is obtained by hydroplaning. And a predetermined gap is formed between them. Since this gap is substantially proportional to the supply amount of the electrolytic solution, the gap can be maintained by appropriately maintaining this supply amount. Therefore, no skill is required, the gap can be easily adjusted by controlling the flow rate, and readjustment is unnecessary even when the wheel is worn, replaced, or cleaned.
[0012]
Further, this configuration, the gap at the time of abnormality (e.g., abnormal stop of the grinding wheel) can either be prevented interpolar short even plummeted.
[0013]
The means for adjusting the gap between the electrode and the grindstone includes a gap detector (21) for measuring the gap between the electrode and the grindstone, and an electrolyte flow rate control valve (22) for controlling the flow rate of the electrolyte. It is preferable to control the flow rate of the electrolyte so that the gap detected by the detector maintains a predetermined constant value. With this configuration, the gap can be automatically adjusted.
[0014]
Further, (A) an electrolyte is supplied between the electrode and the grindstone, and the electrode is lifted by hydroplaning, and then a voltage is applied between the electrode and the grindstone. (B) supply of the electrolyte is stopped and / or It is preferable to stop the voltage application when the rotation is stopped. With this configuration, it is possible to prevent a short-circuit between the electrodes when there is an abnormality (for example, when the grindstone is abnormally stopped) without a contact prevention material.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to a common member and the overlapping description is abbreviate | omitted.
The inventors of the present invention, the electrolytic in-process dressing grinding method (Electrolytic Inprocess Dressing: ELID grinding method) referred to as "electrolytic dressing method and apparatus for conducting grindstone" was invented and (Kokoku 6 - No. 075823). In this method and apparatus, a voltage is applied to a conductive grindstone, and the conductive grindstone is dressed by electrolysis so that a good mirror surface and a smooth flat surface can be obtained at high efficiency and high speed.
This ELID grinding method does not cause clogging of the grindstone due to electrolytic dressing, so if the abrasive grains are made fine, an extremely excellent machining surface such as a mirror surface can be obtained by grinding and lapping using a free abrasive The mirror surface can be machined at a speed several tens of times higher than the above. The present invention is a further development of such an ELID grinding method to improve accuracy.
[0016]
FIG. 1 is an overall configuration diagram of an ELID surface grinding apparatus provided with an electrode support device of the present invention. The ELID surface grinding apparatus includes a metal bond grindstone 10 having a horizontal machining surface 10a, a work holding / rotating means 4 having a horizontal support surface 4a opposite to the machining surface 10a of the metal bond grindstone 10, a voltage applying means 16, and an electrolytic solution. Supply means 20 is provided.
[0017]
The metal bond grindstone 10 is driven to rotate about a vertical axis Z1 by the driving device 3. This metal bond grindstone 10 is composed of a cerium oxide abrasive grain or CBN abrasive grain and a joint part containing cast iron and cobalt as components, and an “electrolytic dressing” can be performed in which the joint part is electrolyzed to sharpen the abrasive grain. ing.
The work holding and rotating means 4 is also rotationally driven by another drive device 5 around a vertical axis Z2 that is configured in parallel with high accuracy to the axis Z1 of the metal bond grindstone 10. Further, the work holding and rotating means 4 holds and rotates a disk-shaped member, that is, a magnetic disk substrate 1 as a workpiece, or a truing grindstone having a shape similar to this, in close contact with the support surface 4a. It is configured to be movable vertically. The work holding / rotating means 4 may be, for example, a vacuum chuck device or a mechanical chuck device.
[0018]
The voltage application means 16 includes an electrode 16a that is not contacted with the processing surface 10a of the metal bond grindstone 10, a power supply for electrolytic dressing (ELID power supply 16b), a power supply body 16c that feeds the metal bond grindstone 10, and these. The power supply line 16d is electrically connected. The metal bond grindstone 10 is used as an anode, the electrode 16a is used as a cathode, and a pulse voltage is applied between both electrodes.
Further, the grinding fluid supply means 20 comprises a nozzle 20a for grinding fluid, a supply device 20b, and a pipe 20c that communicates these, and the processing surface 10a of the metal bond grindstone 10, that is, the processing surface 10a, the electrode 16a, and the support surface 4a. In addition, a conductive grinding fluid is allowed to flow between the magnetic disk substrate 1 and the magnetic disk substrate 1.
With the above-described configuration, the processing surface 10a of the metal bond grindstone 10 is electrolytically dressed, and at the same time, the support surface 4a of the work holding and rotating means 4 is ground and the magnetic disk substrate 1 attached to the work holding and rotating means 4 is ground. Can be alternately performed on the machine.
[0019]
2 is a view taken in the direction of arrow I in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line II - II ′ in FIG. As shown in these drawings, the electrode support device of the present invention includes an electrode guide 18 that supports the electrode 16a so as to be movable up and down, and the above-described electrolyte supply means 20 that supplies the electrolyte between the electrode 16a and the grindstone 10. It consists of. In this example, the electrode guide 18 includes an inner end guide 18a and an outer end guide 18b. The inner end guide 18a and the outer end guide 18b have a radial inner surface that is sufficiently spaced from the inner and outer ends of the electrode 16a, and a circumferential guide surface that guides both ends in the circumferential direction of the electrode 16a with a slight gap. Have. With this configuration, the electrode 16a does not move in the circumferential direction and can freely move up and down in the vertical direction. The electrode guide is not limited to this configuration, and another structure, for example, a structure that urges the electrode downward or upward with a thin flat spring may be used as long as the electrode 16a is supported so as to be movable up and down.
[0020]
Furthermore, the contact preventing material 17 is attached to the grindstone side (the lower surface in this example) of the electrode 16a by pasting or the like. The contact prevention member 17 is desired gap electrode 16a and the grinding wheel 10 (e.g., 0.1 - 0.15 mm) made of a thin insulating material than. As this insulating material, for example, a ceramic foil can be used.
[0021]
As shown in FIG. 2, the electrode support apparatus of the present invention further includes a gap detector 21 that measures the gap between the electrode 16a and the grindstone 10, and an electrolyte flow rate control valve 22 that controls the flow rate of the electrolyte, detected by the detector 21 gaps predetermined constant value (e.g., 0.1 - 0.15 mm) so as to control the flow rate of the electrolyte to hold. As the gap detector 21, for example, a light reflection sensor can be used.
[0022]
According to the apparatus and method of the present invention described above, the electrode 16a is supported by the electrode guide 18 so as to be movable up and down, the electrolyte solution is supplied between the electrode and the grindstone by the electrolyte solution supply means 20, and the electrode 16a is formed by hydroplaning. It floats and a predetermined gap is formed between them. Since this gap is substantially proportional to the supply amount of the electrolytic solution, the gap can be kept constant over the entire surface of the electrode 16a by appropriately maintaining this supply amount. Therefore, no skill is required, the gap can be easily adjusted by controlling the flow rate, and readjustment is unnecessary even when the wheel is worn, replaced, or cleaned.
[0023]
Further, the contact prevention material 17 can prevent a short circuit between the electrodes even when the gap is suddenly reduced in an abnormal state (for example, when the grindstone is abnormally stopped).
Furthermore, the gap can be automatically adjusted by providing the gap detector 21 and the electrolyte flow rate control valve 22 to control the flow rate of the electrolyte.
[0024]
Further, using the electrode support device of the ELID surface grinding machine described above, (A) after supplying the electrolyte between the electrode and the grindstone and lifting the electrode by hydroplaning, a voltage is applied between the electrode and the grindstone. (B) When the supply of the electrolyte solution is stopped and / or the rotation of the grindstone is stopped, the voltage application is stopped, so that even when there is no contact preventive material, a short-circuit between the electrodes can be performed at the time of abnormality (for example, when the grindstone is abnormally stopped). Can be prevented.
[0025]
【Example】
Using the electrode support device shown in FIG. 2, the amount of lift of the electrode by hydroplaning was measured. Using a pair of nozzles with elongated tips at a position approximately 10 cm ahead of the electrode on the upper surface of the grinding wheel, the electrolytic solution is applied to the grinding wheel surface at a rotation speed of the grinding wheel of 100 rpm and an electrolyte supply amount of about 2 liters / minute. Flowed to the average. At this time, adjustment was made so that almost no wave was generated on the surface of the electrolytic solution.
[0026]
The measured floating float, that is, the gap between the electrode and the grindstone, was confirmed to be stable over the entire surface of the electrode in the range of 0.15 mm to 0.2 mm as a result of light reflection measurement, and it was confirmed that the electrolytic dressing of the grindstone could be performed well. It was done.
[0027]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the case where one side of the workpiece is machined has been described in detail. However, the present invention is not limited to this and can be similarly applied to double-side grinding.
[0028]
【The invention's effect】
As described above, the ELID surface grinder electrode support apparatus and method of the present invention can easily adjust the gap between the grindstone processing surface without requiring skill, and the grindstone can be worn and replaced. Even when cleaning, etc., it has an excellent effect that readjustment is unnecessary.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an ELID surface grinding apparatus provided with an electrode support device of the present invention.
FIG. 2 is a view taken in the direction of arrow I in FIG.
3 is a cross-sectional view taken along the line II - II ′ of FIG.
FIG. 4 is a schematic diagram of an unpublished mirror surface processing apparatus according to a prior application.
[Explanation of symbols]
1 Workpiece (magnetic disk substrate)
2 Metal bond grindstone 2a Work surface 3, 5 Drive device 4 Work holding rotation means 4a Support surface 6a Electrode 6 Voltage application means 8 Grinding fluid supply means 10 Conductive grindstone 10a Work surface 16 Voltage application means 16a Electrode 16b Power supply (ELID power supply)
16c Feeder 17 Contact prevention material 18 Electrode guide 18a Inner end guide 18b Outer end guide 20 Electrolyte supply means 20a Nozzle 20b Supply device 20c Pipe 21 Gap detector 22 Electrolyte flow control valve

Claims (4)

An electrode support device that supports an electrode (16a) opposite to a horizontal processing surface (10a) of a conductive grindstone (10) that rotates about a vertical axis, and that supports the electrode so as to move up and down A guide (18), an electrolyte supply means (20) for supplying an electrolyte between the electrode and the grindstone, and an insulating material attached to the grindstone side of the electrode (16a) and thinner than a desired gap between the electrode and the grindstone An electrode for an ELID surface grinder , comprising: a contact prevention material (17) comprising: means for adjusting the gap between the electrode and the grindstone by flowing an electrolytic solution over the processed surface and lifting the electrode by hydroplaning Support device. The means for adjusting the gap between the electrode and the grindstone includes a gap detector (21) for measuring the gap between the electrode and the grindstone, and an electrolyte flow rate control valve (22) for controlling the flow rate of the electrolyte, and the gap detector in the sensed gap to control the flow rate of the electrolyte to maintain a predetermined constant value, it ELID surface grinder of the electrode support device according to claim 1, wherein the. An electrode support method for supporting an electrode (16a) facing a horizontal processing surface (10a) of a conductive grindstone (10) rotating about a vertical axis, the electrode being supported so as to be movable up and down, A contact prevention material (17) made of an insulating material thinner than a desired gap between the electrode and the grindstone is attached to the grindstone side of the electrode (16a), and the electrode is floated by hydroplaning by flowing an electrolyte on the processed surface. An electrode support method for an ELID surface grinder, wherein a predetermined gap is formed in the ELID surface grinder. (A) After supplying an electrolyte between the electrode and the grindstone and lifting the electrode by hydroplaning, a voltage is applied between the electrode and the grindstone, and (B) supply of the electrolyte is stopped and / or rotation of the grindstone is stopped. 4. The electrode support method for an ELID surface grinder according to claim 3 , wherein the voltage application is stopped at the time.

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