JP2000061810A - Magnetic polishing method and magnetic polishing apparatus - Google Patents

Abstract

[PROBLEMS] To find out optimal polishing conditions for improving the polishing performance in a magnetic polishing method using a mixed type magnetic abrasive using ferromagnetic material particles 2, abrasive grains 3 and a binder 4. Further, the present invention provides a magnetic polishing apparatus capable of performing uniform polishing regardless of the thickness of an object to be polished. SOLUTION: As ferromagnetic material particles 2, irregular-shaped particles having a hardness Hv of 300 or less are used. The ferromagnetic material particles 2 are coated with a material having low hardness. The bonding material 4 has a melting point of 30 to 65 ° C.
Use oils and fats. The mixed type magnetic abrasive 1 was prepared by mixing ferromagnetic particles 40 to 70% by volume, abrasive grains 15 to 35% by volume,
It is composed of a mixing ratio of up to 35% by volume. The magnetic polishing apparatus further includes a magnetic flux number measuring device for detecting the magnetic flux number of the magnetic circuit, and adjusts the power of the electromagnet in accordance with the change in the magnetic flux number to polished the non-magnetic material to be polished with the thickness partially different. Is polished at a constant polishing pressure.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnetic polishing method and a magnetic polishing apparatus for polishing an object to be polished with a magnetic abrasive in a magnetic field.

[0002]

2. Description of the Related Art A magnetic polishing method in which a magnetic abrasive is magnetically attracted to an object to be polished so that the objects to be polished are relatively moved while being pressed against each other is known as a magnetic polishing method. Alternatively, since the magnetic polishing material follows the irregularities of the object to be polished, it is effective for surface finishing and deburring of the object to be polished having a complicated shape such as a mold.

Conventionally, as a magnetic abrasive, as shown in FIG. 14, abrasive grains 101 such as aluminum oxide having a particle size of several μm are adhered to the surface of a ferromagnetic material particle 100 having a particle size of several 100 μm in a metal bonded state. However, the magnetic abrasive grains in which the abrasive grains 101 and the ferromagnetic material particles 100 are integrated are used. However, the magnetic abrasive grains have a special manufacturing method, are high in cost, and have a small number of types. There is a problem that it is difficult to optimize the conditions.

In order to solve such a problem, the present inventor discloses in Japanese Patent Laid-Open No. 5-42476 that the ferromagnetic material particles and the abrasive particles are separated and held by a binder such as oily wax. We proposed a new magnetic polishing method using mixed magnetic abrasives.

According to the magnetic polishing method using this mixed type magnetic abrasive, compared with the case of using the conventional magnetic abrasive grains,
Since there are no abrasive grains on the surface of the magnetic abrasive grains that become the magnetic resistance and the magnetic field is several tens of times stronger, a polishing force of several tens of times was obtained, and the polishing force was dramatically increased. Further, the degree of freedom in selecting the ferromagnetic material particles, the abrasive grains, and the binder is high, and the cost is low.

[0006]

However, a new magnetic polishing method using such a mixed magnetic abrasive is as follows:
Polishing conditions have not been fully clarified because polishing is performed by a mechanism that is completely different from conventional magnetic polishing methods and the selection of ferromagnetic material particles, abrasive grains, and binders that make up magnetic polishing materials is wide. It was Therefore, it has been demanded to improve the polishing performance such as the polishing amount and the finished surface in the magnetic polishing method.

The present invention has been made in view of the above-mentioned demands, and the optimum polishing conditions for improving the polishing performance in a magnetic polishing method using a mixed magnetic abrasive containing ferromagnetic material particles, abrasive grains and a binder. The purpose is to find out.

Further, in the conventional magnetic polishing apparatus, when the object to be polished is a non-magnetic material having a partially different thickness, the magnetic resistance changes as the thickness of the object to be polished changes. Changes, and the number of magnetic flux decreases in the thick part,
Since the number of magnetic flux increases in the thin part, the pressing force of the ferromagnetic material particles against the work piece changes, and as a result, the cutting amount of the abrasive grains changes, and the polishing force partially changes depending on the thickness of the work piece. There is a problem that changes to.

Therefore, an object of the present invention is to provide a magnetic polishing apparatus capable of performing uniform polishing regardless of the thickness of the object to be polished.

[0010]

The present inventors repeated experiments while examining the polishing mechanism of a magnetic polishing method using a mixed magnetic abrasive containing ferromagnetic material particles, abrasive grains, and a binder. And found the optimum polishing conditions.

That is, in the magnetic polishing method according to the first aspect of the present invention, the mixed magnetic abrasive containing the ferromagnetic material particles, the abrasive grains and the binder as the main components is pressed against the object to be polished by the magnetic attraction force. In the magnetic polishing method for polishing the object to be polished by relatively moving the mixed magnetic abrasive and the object to be polished, the ferromagnetic material particles are irregularly shaped particles.

According to a second aspect of the present invention, there is provided a magnetic polishing method in which ferromagnetic material particles, abrasive grains, and a mixed magnetic abrasive material containing a binder as a main component are pressed against an object to be polished by magnetic attraction. In the magnetic polishing method of polishing the object to be polished by relatively moving the type magnetic abrasive and the object to be polished, the Vickers hardness Hv of the ferromagnetic material particles is 300.
It is characterized by the following.

According to a third aspect of the present invention, there is provided a magnetic polishing method in which ferromagnetic material particles, abrasive grains, and a mixed magnetic abrasive material containing a binder as a main component are pressed against an object to be polished by magnetic attraction. In a magnetic polishing method for polishing an object to be polished by relatively moving a die-shaped magnetic abrasive and the object to be polished, the ferromagnetic material particles are coated with a material having a hardness lower than that of the ferromagnetic material particles. It is characterized by

According to a fourth aspect of the present invention, there is provided a magnetic polishing method, wherein a mixed magnetic abrasive containing ferromagnetic material particles, abrasive grains, and a binder as main components is pressed against an object to be polished by a magnetic attractive force, and these are mixed. In the magnetic polishing method for polishing the object to be polished by relatively moving the mold magnetic abrasive and the object to be polished, the binder is a fat or oil having a melting point of 30 to 65 ° C.

According to a fifth aspect of the present invention, there is provided a magnetic polishing method according to the fourth aspect.
In the magnetic polishing method described above, the binder is lauric acid.

According to a sixth aspect of the present invention, there is provided a magnetic polishing method in which a mixed magnetic abrasive containing ferromagnetic material particles, abrasive grains, and a binder as main components is pressed against an object to be polished by magnetic attraction to mix them. In the magnetic polishing method of polishing the object to be polished by moving the type magnetic abrasive and the object to be polished relative to each other, the mixed magnetic abrasive is 40
˜70% by volume, the abrasive grains are 15 to 35% by volume, and the binder is 15 to 35% by volume.

The magnetic polishing method according to claim 7 is the method according to claim 6.
In the magnetic polishing method described above, each component is supplied so as to maintain a mixing ratio range of the mixed magnetic polishing material during polishing.

In the magnetic polishing method according to the present invention, a mixed magnetic abrasive containing ferromagnetic material particles, abrasive grains and a binder as main components is pressed against an object to be polished by a magnetic attraction force to mix these. In the magnetic polishing method for polishing the object to be polished by relatively moving the die magnetic abrasive and the object to be polished, a part or all of the magnetic abrasive is replaced during polishing.

Further, a magnetic polishing apparatus according to a ninth aspect is provided with a yoke forming a magnetic circuit, an electromagnet, and a power source for supplying electric power to the electromagnet, and a magnetic material is attached to an object to be polished arranged in a void portion in the magnetic circuit. In a magnetic polishing apparatus that presses an abrasive with a magnetic attraction force and relatively moves the object to be polished and the magnetic abrasive to polish the object to be polished, the number of magnetic fluxes for detecting a change in the number of magnetic fluxes of the magnetic circuit. A measuring device is provided, and the magnetic flux number measuring device changes the electric power of the power source according to the change of the magnetic flux number, and controls so as to maintain the magnetic flux number of the magnetic circuit.

In this magnetic polishing apparatus, a magnetic flux number measuring device detects a change in the magnetic flux number of the magnetic circuit, and the electric power to the electromagnet is adjusted based on the change in the magnetic flux number. This detects a decrease in the number of magnetic fluxes when polishing a thick part of the object to be polished, increases the electric power to the electromagnet to increase the polishing force, and when polishing a thin part of the object to be polished. Since the increase in the number of magnetic fluxes can be detected to reduce the power supply to the electromagnet to reduce the polishing force, it is possible to perform uniform polishing at a constant polishing pressure regardless of the thickness of the object to be polished.

According to a tenth aspect of the present invention, there is provided a magnetic polishing apparatus according to the ninth aspect, further comprising a supply device for supplying a part or all of components constituting the magnetic polishing material to the object to be polished. Characterize.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.

The magnetic polishing method of the present invention comprises ferromagnetic material particles,
While pressing the mixed magnetic abrasive containing abrasive grains and the binder as the main components against the object to be polished by magnetic attraction, the magnetic abrasive and the object to be polished are moved relatively to each other. It is to be polished.

FIG. 1 schematically shows a method of performing magnetic polishing using a general magnetic polishing apparatus. (A) is a case of polishing the outer surface of a cylinder of a magnetic material, (b) is a non-magnetic material. The case where the inner surface of the circular tube of material is polished is shown.

The magnetic polishing apparatus shown in FIG.
The opposite magnetic poles are the S magnetic pole 11 and the N magnetic pole 12, and the exciting coil 13 is wound around the yoke 10 at a position slightly apart from the magnetic pole at the tip of the yoke.
Make up 15. A power source (not shown) is connected to the exciting coil 13 to supply electric power to the exciting coil 13.
The object to be polished 20 is arranged between the magnetic poles 11 and 12, and is attached to, for example, a motor and a vibration exciter via a ball spline so that rotation about an axis and vibration in the axial direction are given. .

In the mixed magnetic polishing material 1, the binder is solid at room temperature, and after the power supply of the exciting coil is turned on, it is filled as a lump in the space between the magnetic poles 11 and 12 and the object to be polished 20. It A magnetic circuit is constituted by the yoke 10, the magnetic poles 11 and 12, the mixed magnetic abrasive 1, and the object to be polished 20, and the mixed magnetic abrasive 1 is covered by the magnetic field between the magnetic poles 11 and 12 and the object to be polished 20. The surface of the polishing object 20 is pressed.

In this state, when the object to be polished 20 is rotated and axially vibrated, the binder is initially in a solid state.
The processing area temperature rises due to frictional heat, and as soon as it reaches the melting point, it begins to melt, and the ferromagnetic material particles in the mixed magnetic abrasive 1 are arranged in a brush shape along the lines of magnetic force, and the holding force of the binder causes grinding. The particles and the ferromagnetic material particles are combined. Since the mixed magnetic abrasive 1 stays at that position due to the magnetic force, the object 20 to be polished is polished by the abrasive grains due to the relative movement between the object 20 to be polished and the ferromagnetic material particles 1.

In the magnetic polishing apparatus of FIG. 1B, the S magnetic pole 11 and the N magnetic pole 12 at the tip of the yoke 10 face each other in a direction orthogonal to each other, and the exciting coil 13 is slightly separated from the magnetic pole at the tip of the yoke 10. The electromagnets 13 and 14 are wound around the position yoke 10. A power source (not shown) is connected to the exciting coil 13 to supply electric power to the exciting coil 13. The object to be polished 20 is arranged between the magnetic poles 11 and 12,
For example, it is attached to a motor and a vibration exciter via a ball spline so that rotation about an axis and vibration in the axial direction are applied.

The mixed magnetic abrasive 1 is filled in the circular tube 20. When the exciting coil 13 is turned on, a magnetic circuit is constituted by the yoke 10, the magnetic poles 11 and 12, and the mixed magnetic abrasive material 1. The ferromagnetic material particles in the magnetic abrasive material 1 are
The inner surface of the circular tube 20 is pressed against the inner surface of the circular tube 20 by suction.

In this state, when the circular tube 20 is rotated and vibrated in the axial direction, the binder is melted by frictional heat, and the ferromagnetic material particles in the circular tube remain at the position due to the magnetic force. The inner surface of the circular pipe 20 is polished by the relative movement of the mixed magnetic polishing material with the.

FIG. 2 schematically shows the polishing mechanism of the magnetic polishing method according to the present invention. The ferromagnetic material particles 2 are
The object to be polished 20 is pressed by a magnetic force to exert a vertical force Px. Further, while receiving a force Pm held in the magnetic field, the object 20 to be polished is relatively moving as indicated by an arrow, so that the force Py to rotate together with the object 20 to be polished is received, and these forces are horizontally applied. The force of the difference Ps = Pm-Py is received. Px
Abrasive grain direction component force Pb of force Pa that is a combination of Ps and Ps is applied to the abrasive grain 3 sandwiched between the ferromagnetic material particle 2 and the object 20 to be polished, and the abrasive grain 3 has a vertical spin on the object 20 to be polished. A component force Pv is given. In this way, the surface of the object to be polished 20 is shaved by the abrasive grains 3 that have received the polishing pressure, and a notch is generated, so that the object to be polished 20 is polished. At this time, abrasive grains 3
The binder 4 is a combination of the ferromagnetic particles 2 and the ferromagnetic particles 2.

From these facts, the ferromagnetic material particles 2 need to have a function of receiving a magnetic force and giving a polishing pressure to the abrasive grains 3, and therefore the required characteristics are that the magnetic characteristics are good and the particle diameter is Being suitable, the shape can hold the abrasive grains well,
The hardness is not too high, it is easily available, and it is inexpensive. Regarding the magnetic properties, it can be mentioned that the coercive force is small, the maximum magnetic flux density is high, and the magnetic permeability is high.

Specific examples of the material of the ferromagnetic material particles 3 include iron and an alloy of iron and nickel.

Further, since the abrasive grains 3 have a function of polishing the object to be polished, it is possible to select the material, hardness and particle size according to the kind of the object to be polished. Specifically, aluminum oxide, Examples thereof include chromium oxide and iron oxide.

The present inventor has conducted detailed experiments on the components constituting the mixed magnetic abrasive 1 and has clarified the mechanism of polishing.

First, the particle diameters of the ferromagnetic material particles and the abrasive particles were examined. FIG. 3 is a graph in which the polishing amount is measured by changing the particle size ratio between the abrasive grains and the ferromagnetic material particles. FIG. 3A shows an initial surface roughness of 5 to 8 μmR using steel balls as ferromagnetic material particles, aluminum oxide as abrasive grains, and palmitic acid as a binder.
The outer surface of the SK3 circular tube of y was polished. Figure 3
(B) is obtained by polishing the inner surface of a stainless steel circular tube having an initial surface roughness of 10 to 15 μmRy using steel balls as ferromagnetic material particles, aluminum oxide as abrasive grains, and lauric acid as a binder. is there.

From the result of FIG. 3 (a), from the polishing amount of the outer surface of the circular tube, there is an optimum particle size ratio to the ferromagnetic material particles in the abrasive particle size, and the particle size ratio (abrasive particle / ferromagnetic material particle). ) Is 0.05 ~
It is about 0.3, preferably about 0.2. Also, FIG.
From the result of (b), there is an optimum value for the particle size ratio of the abrasive particle size / ferromagnetic material particle from the polishing amount on the inner surface of the circular tube. The optimum value is
It is about 0.01 to 0.2, preferably about 0.02 to 0.1. Therefore, the general abrasive grain size / ferromagnetic material grain size ratio is 0.01 to 0.3, and preferably 0.02 to
The optimum value is about 0.2.

The reason why there is an optimum value in the particle size ratio of abrasive particle size / ferromagnetic material particle is considered as follows. As shown in FIG. 4, when the particle size of the abrasive grains 3 becomes relatively large, the back force Pv against the object to be polished 20 among the force Pb given from the ferromagnetic material particles 2 becomes gradually smaller, and the polishing force becomes smaller. It is expected to decrease.

On the contrary, when the grain size of the abrasive grains 3 becomes too small, as shown in FIG. 5, the initial surface roughness R of the object to be polished 20 is increased.
It is considered that when the grain size of the abrasive grains 3a is smaller than y, the abrasive grains 3a are clogged in the concave portions of the surface roughness and the polishing function cannot be exerted. Actually, when the grain size of the abrasive grains is 7 μm, which is smaller than the initial surface roughness of 5 to 8 μmRy in the polishing of the outer surface of the circular pipe, and when the grain size of the inner surface of the circular pipe is smaller than 4 μm, the initial roughness is almost the same. Could not be improved. Therefore, as shown in 3b of FIG. 5, it is preferable to select an abrasive grain having a particle size larger than the initial surface roughness Ry of the object to be polished, and the optimum grain size corresponding to the particle size of the abrasive grain. It is preferable to select ferromagnetic material particles having a particle size.

Further, the shape and material of the ferromagnetic material particles and the material of the abrasive grains were examined. FIG. 6 is a three-dimensional graph showing the results of polishing the outer surface of the circular pipe. X axis is particle size 80-100μ
The shape and the material of the ferromagnetic material particles of m are shown, and B-Fe is a steel ball having hardness Hv (Vickers hardness) of 900, B-45Ni.
Is a 45% Ni permalloy ball, A-Fe is an iron powder of indefinite shape manufactured by a water atomizing method, and has a hardness Hv of 200 to 300, and A-45Ni is an indefinite shape of 45Ni.
Permalloy powder with hardness Hv of about 120, A-78Ni
Is an irregularly shaped 78Ni permalloy powder with a hardness Hv of 1
It is about 40. The Y axis indicates the type of abrasive grains having a grain size of 6 to 7 μm, and chromium oxide and aluminum oxide are used. Z
The axis indicates the surface roughness (μm) of the object to be polished after polishing.

The water atomizing method is a method for directly producing molten powder by dropping it into a cooling liquid such as water and then rapidly cooling it to form an irregularly-shaped powder having large irregularities.

From the results shown in FIG. 6, the shape of the ferromagnetic material particles is
Apparently, the irregular shape has a better finishing effect than the spherical shape. Further, it is recognized that a good finishing effect can be obtained when the hardness of the ferromagnetic material particles is low. As for the material of the abrasive grains, chromium oxide gave a better finishing effect than aluminum oxide. In particular, the combination of A-78Ni and chromium oxide was optimal, and a mirror surface of 0.08 μmRy was obtained.

It is considered as follows that the irregular-shaped ferromagnetic material particles can obtain a better finishing effect than the ball-shaped ferromagnetic material particles. As shown in FIG. 7, the irregular-shaped ferromagnetic material particle 2A can hold a large number of abrasive grains 3 in the irregular-shaped concave portion, while the spherical ferromagnetic material particle 2B retains the abrasive grain 3. I can't. Therefore, in the case of a sphere,
The back surface force applied to the ferromagnetic material particles 2B is transmitted to the object to be polished 20 through a small number of abrasive grains 3, and the polishing pressure acting on the abrasive grains 3 increases, leaving scratch marks and leaving a finished surface. become worse. On the other hand, in the case of the irregular shape, the back force is transmitted to the object to be polished 20 through the large number of abrasive grains 3 held in the irregular concave portion, so that the polishing pressure per abrasive grain becomes small, It is considered that a good finished surface can be obtained.

Another experiment was conducted on the hardness of the ferromagnetic material particles. In order to study the difference due to the hardness of the ferromagnetic material particles, a steel ball with a hardness of Hv900 was annealed, and Hv30
Polishing was performed by using a steel ball reduced to 0 and Hv200 and using aluminum oxide as abrasive grains. The graph of the result is shown in FIG.

In FIG. 8, the bar graph shows the polishing amount, and the line graph shows the surface roughness. When the hardness of the ferromagnetic material decreases, the polishing amount increases and the finished surface tends to be good.

The reason for this is that when the hardness of the ferromagnetic material particles becomes low, the abrasive grains bite into the surface of the ferromagnetic material, the abrasive grains are easily held by the ferromagnetic material particles, and the polishing pressure transmitted to the abrasive grains increases. Therefore, it is considered that the polishing amount increases. Also,
It is considered that when the hardness of the ferromagnetic material particles is high, scratch marks are left on the finished surface of the object to be polished. Therefore, the hardness Hv of the ferromagnetic material particles is preferably low, and together with the result of FIG. 6, the Vickers hardness Hv is 300 or less, preferably about 70 to 200.

Further, the lower the hardness of the ferromagnetic material particles, the better the holding force of the abrasive grains and the better the polishing performance.
As shown in, it is possible to use the coated ferromagnetic material particles 2C in which the surface of the ferromagnetic material particles 2 is coated with a material 5 having a hardness lower than that of the ferromagnetic material particles, for example, a resin. When the ferromagnetic material particles 2 are coated with this coating material 5, the result shown in FIG.
As shown in FIG. 5, the abrasive grains 3 are better bited into, and the polishing performance for the object to be polished 20 is improved. Further, when polishing an object to be polished having a hardness lower than that of the ferromagnetic material particles, if the hardness of the coating material is equal to or lower than that of the object to be polished, the coating material does not damage the object to be polished. There is also an advantage that it is possible to eliminate the possibility that scratches will be generated by the magnetic material particles. This is effective, for example, in polishing a soft polishing object such as a plastic lens. Therefore, as the coating material, from this point of view, for example, polyolefin such as polyamide, polyimide, polyethylene, thermoplastic resin such as diene polymer, fluorine-containing polymer, phenol resin, epoxy resin, silicone polymer, etc. Curable resin etc. can be illustrated. Further, as the coating material, a metal having a low hardness can be adopted, and for example, it can be coated by a method such as vapor deposition, CVD and sputtering.

The binder is a characteristic component of the mixed magnetic polishing material of the magnetic polishing method according to the present invention. The functions required for the binder are the function of holding the abrasive particles to the ferromagnetic material particles, the function of transmitting the magnetic force of the ferromagnetic material particles to the abrasive particles as the polishing pressure, the circulating function of promoting the spontaneous action of the abrasive particles, and the abrasive material. Examples thereof include a lubrication function, a cooling function, and a chemical polishing function that reduce the frictional force between the particles and the object to be polished, or the ferromagnetic material particles and the object to be polished.

The melting point of this binder was examined.
The inner surface of the circular pipe was polished using the binders of the types shown in Table 1 below, using 175 μm steel balls as the ferromagnetic material particles and aluminum oxide having a particle size of 4 μm as the abrasive grains. The mixing ratio of the mixed magnetic abrasives is as follows: ferromagnetic material particles: abrasive particles: binder = 50
% By volume: 25% by volume: 25% by volume. The result is shown in FIG.

[0050]

[Table 1]

The bar graph in FIG. 10 shows the polishing amount, and the line graph shows the finished surface roughness. GF that is liquid at room temperature
With the above grinding oil, almost no polishing was possible because there was no retention of the abrasive grains. Also, the metal soap MS having a melting point of 65 ° C.
Almost no polishing was possible because it did not melt during polishing. The fatty acids FAI to FAIII, which are solid at room temperature and have a melting point that melts due to frictional heat during polishing, were excellent in both the amount of polishing and the finished surface. Lauric acid (FAI) with a melting point of 45 ° C
Optimum polishing performance was obtained when using. The polishing performance tended to gradually decrease as the melting point of the oil and fat increased.

From the results of FIG. 10, it was found that the binder is preferably a solid at room temperature, that is, an oil having a melting point of 30 ° C. or higher and 65 ° C. or lower. This indicates that the bonding material has an important function of bonding the ferromagnetic material particles and the abrasive particles.

Further, the mixing ratio of the ferromagnetic material particles, the abrasive grains, and the binder, which compose the mixed magnetic abrasive, was examined.
FIG. 11 (a) shows a steel ball of 175 μm as a ferromagnetic material particle, aluminum oxide having a particle diameter of 4 μm as an abrasive grain, and lauric acid as a binder, and the mixing volume ratio of the abrasive grain and the binder is fixed to 1: 1. Then, the results of polishing the inner surface of the stainless steel tube by changing the mixing ratio of the ferromagnetic material particles are shown. The bar graph shows the polishing amount, and the line graph shows the finished surface roughness.

As shown in FIG. 11 (a), when the ferromagnetic material particles are 0% by volume, there is no ferromagnetic material particles, so that the polishing pressure cannot be obtained and the polishing cannot be performed. The ratio of ferromagnetic material particles is 0
The polishing performance gradually increases as the content increases from 5% to 5
When the content is 0% by volume, the polishing amount is the largest and the finished surface is good. When it exceeds 50% by volume, the polishing performance gradually decreases, and when the ferromagnetic material particles are 100% by volume, it is hardly polished because there are no abrasive grains.

In FIG. 11B, the ferromagnetic material particles are 50
The results of experiments were performed by fixing the content to 50% by volume and changing the mixing ratio of the abrasive grains and the binder for the remaining 50% by volume. The experimental conditions are the same as those in FIG.

As shown in FIG. 11 (b), when the mixing ratio of the abrasive grains is 0% by volume, almost no polishing is performed. The polishing performance improves as the mixing ratio of abrasive grains increases, and
At the volume% (abrasive grains: binder = 1: 1), the polishing amount was the largest and the finished surface was good. When it exceeds 25% by volume, the polishing performance is gradually reduced to 50% by volume, that is,
When the content of the binder is 0% by volume, the holding force of the abrasive grains by the binder is lost, and the abrasive is hardly polished.

From these results, the mixing ratio of the mixed magnetic abrasive is as follows: ferromagnetic material particles: abrasive particles: binder = 50% by volume: 2
Focusing on 5% by volume: 25% by volume, ferromagnetic material particles: abrasive grains: binder = 40 to 70% by volume: 15 to 35% by volume:
It has been found that a range of 5 to 35% by volume is suitable.

The reason why the mixing ratio of this ferromagnetic material particle: abrasive particle: binding material = 50% by volume: 25% by volume: 25% by volume is most preferable is considered as follows.

When the ferromagnetic material particles have a spherical shape, the ferromagnetic material particles reduce the magnetic resistance along the lines of magnetic force.
It has been observed to arrange in a simple cubic structure as shown in 2. If the radius of the ferromagnetic material particles is a, 12 volumes of ferromagnetic material particles in the cube shown in the 4πa ^3/3, because the volume of the cube is 8a ^3, cube shown in Figure 12 of ferromagnetic material particles The volume ratio of 4 / 3πa ³ / 8a ³ =
It becomes π / 6≈0.5236% by volume. The remaining about 48% by volume will be occupied by the abrasive grains and the binder. Since it is necessary for the abrasive grains to move around freely in the voids between the ferromagnetic material particles, assuming that the abrasive grains are also filled in the voids between the ferromagnetic material particles with a simple cubic structure, the amount of the abrasive grains is 48% by volume. × 0.
52 = 25% by volume, the binder is the remaining 23% by volume.
This value is almost the same as the optimum value obtained by the experiment, that is, the mixing ratio of ferromagnetic material particles: abrasive particles: bonding material = 50% by volume: 25% by volume: 25% by volume.

In the magnetic polishing method according to the present invention, there is such an optimum range for the mixing ratio of the mixed magnetic polishing material. However, since the object to be polished is subjected to rotation, vibration, etc., the abrasive grains and the binder are likely to be scattered during polishing due to the centrifugal force of the rotary motion. Therefore, since the mixing ratio of the mixed magnetic abrasive changes during polishing, one or both of the abrasive grains and the binder may be maintained during polishing so as to keep the mixing ratio of the mixed magnetic abrasive in the optimum range. Is preferably replenished appropriately.

Further, in the polishing, the finished surface roughness of the object to be polished is improved as the processing progresses, but when the abrasive grain diameter and the ferromagnetic material particle diameter are changed to the optimum ones according to the finished surface roughness,
The finished surface is improved. Therefore, it is preferable to replace part or all of the mixed magnetic abrasive during polishing. In the magnetic polishing method according to the present invention, it is easy to replace the mixed magnetic polishing material. Turn on the excitation coil power
When it is set to FF, the magnetic attraction force of the ferromagnetic material particles disappears, so that the magnetic abrasive material can be easily removed by the movement of the object to be polished or an external magnetic attraction device. After that, turn on the electromagnet
While supplying the smaller ferromagnetic material particles, abrasive grains, and binder that are more suitable to the finished surface and polishing again, the magnetic abrasive material that was on the finished surface can be replaced, and a good finished surface can be obtained. Obtainable. Of course, the magnetic abrasive may be replaced a plurality of times during polishing.

In the mixed magnetic abrasive, components other than the ferromagnetic material particles, the abrasive grains, and the binder may be appropriately blended according to the purpose of polishing.

In the magnetic polishing method according to the present invention, the polishing performance can be improved more than before by combining the above-mentioned polishing conditions. For example, on the outer surface of the circular tube of SK3, 50% by volume of irregular shape 78Ni having a particle size of 80 to 100 μm as ferromagnetic material particles and a particle size of 6 to 7 μ as abrasive grains are used.
In the case of using a mixed type magnetic abrasive containing 25% by volume of chromium oxide and 25% by volume of palmitic acid as a binder, the initial roughness of 5 to 8 μmRy was 0.08 μmRy in one step of polishing. I was able to finish it to a mirror surface.

On the inner surface of the circular tube of SUS304, 50% by volume of steel balls having a particle size of 175 μm as ferromagnetic material particles, 25% by volume of aluminum oxide having a particle size of 4 μm as abrasive grains, and 25% by volume of lauric acid as a binder. When the mixed magnetic abrasive used at a mixing ratio of 10% was used, the initial roughness of 10 to 15 μmRy could be finished to 0.9 μmRy by one-step polishing.

The magnetic polishing method according to the present invention includes, for example,
Polishing the inner surface of stainless steel pipes and bottles,
It is effective for polishing the outer surface of metal tubes and rods, polishing of molds, polishing of glass molds for manufacturing plastic lenses, polishing of plastic lenses and glass lenses, and polishing of surfaces that cannot be polished by ordinary tools. .

Next, a magnetic polishing apparatus of the present invention suitable for polishing a non-magnetic material such as a plastic lens will be described with reference to FIG. In this magnetic polishing device 30, a substantially U-shaped yoke 31 is arranged in the vertical direction. The exciting coil 13 is wound around the yoke 31, and the power source for supplying power to the exciting coil is a variable power source 33 capable of changing the power. The power from the variable power source 33 is supplied to the exciting coil 13 to configure the DC electromagnet 34, and the power of the DC electromagnet 34 can be adjusted by the variable power source 33. Also, the yoke 3
A vertically downward spindle 35 is rotatably arranged above the upper portion of the first magnet 1, and a cylindrical rotating magnetic pole 36 made of a magnetic material is vertically attached to the spindle, and the side surface of the rotating magnetic pole 36 is a yoke. Reference numeral 31 is a magnetic pole surface 36a that is close to or abuts the end surface of the upper portion, and the lower end surface of the rotating magnetic pole faces the magnetic pole surface 37 of the lower portion of the yoke. Further, an object support device (not shown) is provided, the object 20 is arranged on the upper end surface of the lower magnetic pole of the yoke, and the object 20 is horizontally moved by a vibrator (not shown) such as vibration or rocking. It is possible to give directional movement.

Further, a magnetic flux number measuring device 39 for detecting the magnetic flux number is arranged on the yoke 31, and a controller (not shown) controls the variable power source 33 to the electromagnet 3 when the magnetic flux number decreases.
4 is increased, and when the number of magnetic fluxes is increased, the variable power source 33 is controlled so as to decrease the power supply to the electromagnet 34.

Further, there is provided a magnetic abrasive material supplying device 40 for supplying a ferromagnetic material, abrasive grains and a bonding material into the space between the magnetic pole surface 36a of the rotating magnetic pole 36 and the object to be polished.

When polishing an object to be polished of a non-magnetic material such as a plastic lens with this apparatus, the object to be polished 20 is attached to the object supporting device, and the object to be polished 20 serves as the magnetic pole surface 36a of the rotary magnetic pole 36. It is arranged in the space between the magnetic poles 37 below the yoke 31, and the variable power supply 33 is turned on to generate a magnetic field from the electromagnet 34. Then, the magnetic abrasive material supply device 40
The ferromagnetic material, the abrasive grains, and the bonding material are supplied from a predetermined mixing ratio to give movement to the object to be polished 20, and the spindle 3
Rotate 5. As a result, the ferromagnetic material particles 2 are arranged in a brush shape along the lines of magnetic force as the binder melts, and function as the magnetic brush 6. The magnetic brush 6 rotates with the rotation of the spindle 35, and a relative motion occurs with the object to be polished 20 together with the motion of the object to be polished 20, and the magnetic brush 6 is coupled to the ferromagnetic material particles in the shape of the magnetic brush. The object to be polished 20 is polished by the abrasive grains held by the material.

Magnetic flux flow L in this magnetic polishing apparatus
13, as shown in FIG. 13, a yoke 31, a rotating magnetic pole 36,
The ferromagnetic material particles 2 and the lower magnetic pole 37 are arranged in this order, and the non-magnetic material to be polished 2 between the ferromagnetic material particles 2 and the lower magnetic pole 37 is formed.
0 is the magnetic resistance.

In an object to be polished made of a non-magnetic material such as a plastic lens, the thickness of which varies depending on the processing position, when the thickness of the object to be polished changes, the magnetic resistance increases and the number of magnetic flux decreases at a thick portion, resulting in a strong magnetic field. The pressing force of the magnetic material particles against the object to be polished is weakened and the abrasive grains are less bite, resulting in poor polishing performance. As a result, the finishes differ in the parts having different thicknesses, and uneven polishing occurs.

In the magnetic polishing apparatus of the present invention, when the change of the magnetic flux number is detected by the magnetic flux number measuring device 39 for detecting the change of the magnetic flux, the electric power from the variable power source 33 to the electromagnet 34 is adjusted so that the magnetic flux number is constant. Is configured to be. for that reason,
When polishing a thick portion of the object to be polished 20, the number of magnetic fluxes decreases. Therefore, when the electric power to the electromagnet 34 is increased to increase the polishing force, and when polishing a thin portion of the object to be polished 20, Since the number of magnetic fluxes increases, the power supply to the electromagnet 34 can be reduced to reduce the polishing force. Therefore, regardless of the thickness of the workpiece 20, the polishing can be performed uniformly with a constant polishing pressure. It is possible, and uneven polishing is less likely to occur.

Therefore, the magnetic polishing apparatus 30 of the present invention is
Lens made of non-magnetic material such as plastic, glass, stainless steel, brass, etc., with partially different thickness,
It can be suitably used for polishing an object to be polished such as a glass mold for lens production and a metal mold.

Further, since the magnetic abrasive supply device 40 is provided, the abrasive particles and the binder lost during polishing are supplied so that the mixing ratio in the optimum range of the magnetic abrasive described above is maintained. Can be

Further, even when the magnetic polishing material is replaced according to the roughness of the finished surface, the variable power source 33 of the electromagnet 34 is turned off.
In this case, the magnetic abrasive can be easily removed by the rotation of the spindle 35 and the external suction device, and new magnetic abrasive can be quickly supplied by the magnetic abrasive supply device 40.

The magnetic polishing apparatus of the present invention can use magnetic abrasive grains in which an ordinary ferromagnetic material and abrasive grains are integrated, and the type of magnetic abrasive material is not limited.

Further, in the above-mentioned magnetic polishing apparatus, the lower portion of the yoke is wide so as to receive the workpiece, but it is of course possible to form the magnetic pole so as to face the rotating magnetic pole as usual.

[0078]

According to the magnetic polishing method of the present invention, the polishing performance such as the polishing amount and the finished surface in the magnetic polishing method using the ferromagnetic material particles, the abrasive grains and the binder as the magnetic polishing material can be improved. .

Further, the magnetic polishing apparatus of the present invention can polish an object to be polished of a non-magnetic material having partially different thicknesses with a constant polishing pressure, and can uniformly polish regardless of the thickness.

[Brief description of drawings]

FIG. 1 schematically shows a magnetic polishing method using a magnetic abrasive, where (a) shows polishing of the outer surface of a cylinder and (b) shows polishing of the inner surface of the cylinder.

FIG. 2 is a schematic diagram illustrating a polishing mechanism of a magnetic polishing method using a mixed magnetic abrasive.

FIG. 3 is a graph showing the polishing amount when the particle diameter ratio of abrasive grains and ferromagnetic material particles is changed, and (a) is the polishing of the outer surface of the circular pipe,
(B) shows the case of polishing the inner surface of the circular pipe.

FIG. 4 is a schematic view for explaining that the polishing force transmitted from the ferromagnetic material particles decreases as the particle size of the abrasive particles increases.

FIG. 5 is a schematic diagram illustrating that polishing cannot be performed if the grain size of the abrasive grains is smaller than the initial surface roughness of the material to be polished.

FIG. 6 is a graph showing the surface roughness after polishing when the material and shape of the ferromagnetic material particles and the material of the abrasive grains are changed.

FIG. 7 is a schematic diagram illustrating a polishing mechanism when the ferromagnetic material grains have an irregular shape and a spherical shape.

FIG. 8 is a graph showing the polishing amount and the surface roughness when the hardness of the ferromagnetic material particles is changed.

FIG. 9 is a schematic diagram for explaining the mechanism of polishing by the coated ferromagnetic material particles in which the surfaces of the ferromagnetic material particles are coated.

FIG. 10 is a graph showing the amount of polishing and the surface roughness when the inner surface of a circular pipe is polished using binders having different melting points.

FIG. 11 is a graph showing a polishing amount and a surface roughness when polishing is performed by changing a mixing ratio of a mixed magnetic abrasive, (a) is a mixing ratio of ferromagnetic material particles, and (b) is an abrasive grain. The case where the mixing ratio is changed is shown.

FIG. 12 is a schematic diagram showing a state in which ferromagnetic material particles are arranged in a simple cubic structure along lines of magnetic force.

FIG. 13 is a configuration diagram showing a configuration of a magnetic polishing apparatus of the present invention.

FIG. 14 is a sectional view showing a structure of magnetic abrasive grains used in a conventional magnetic polishing method.

[Explanation of symbols]

1 ... Mixed magnetic abrasive, 2 ... Ferromagnetic material particles, 3 ... Abrasive particles,
4 ... Binder, 10 ... Yoke, 11, 12 ... Magnetic pole, 13 ...
Excitation coil, 14, 15 ... Electromagnet, 20 ... Object to be polished, 3
0 ... Magnetic polishing device, 31 ... Yoke, 33 ... Variable power supply, 3
4 ... Electromagnet, 35 ... Spindle, 36 ... Rotating magnetic pole, 36
a ... magnetic pole surface, 37 ... lower magnetic pole, 39 ... magnetic flux number measuring device, 4
0 ... Magnetic abrasive supply device

Continued front page    (72) Inventor Shin Miyazawa             Seiko, 3-3-3 Yamato, Suwa City, Nagano Prefecture             -In Epson Corporation F-term (reference) 3C058 AA07 AA09 AA12 AB01 AB04                       CA01 CA03 CA04 CA06 CA07                       CB01 CB03 CB10 DA02 DA11

Claims (10)

[Claims] 1. A mixed magnetic polishing material containing ferromagnetic material particles, abrasive grains, and a binder as main components while being pressed against the object to be polished by a magnetic attractive force, and the mixed magnetic abrasive material and the object to be polished. In the magnetic polishing method for polishing the object to be polished by relatively moving and, the ferromagnetic material particles are irregularly shaped particles. 2. A mixed magnetic polishing material containing ferromagnetic material particles, abrasive grains and a binder as main components while being pressed against the object to be polished by a magnetic attractive force, and the mixed magnetic abrasive material and the object to be polished. In the magnetic polishing method for polishing the object to be polished by relatively moving and, the Vickers hardness Hv of the ferromagnetic material particles is 300 or less. 3. A mixed magnetic abrasive containing ferromagnetic material particles, abrasive grains, and a binder as main components while being pressed against the object to be polished by a magnetic attraction force. In a magnetic polishing method for polishing the object to be polished by relatively moving and, the ferromagnetic material particles are coated with a material having a hardness lower than that of the ferromagnetic material particles. . 4. A mixed magnetic polishing material containing ferromagnetic material particles, abrasive grains, and a binder as main components while being pressed against the object to be polished by a magnetic attractive force, and the mixed magnetic abrasive material and the object to be polished. In the magnetic polishing method for polishing the object to be polished by relatively moving and, the binder is an oil or fat having a melting point of 30 to 65 ° C., wherein 5. The magnetic polishing method according to claim 4, wherein the binder is lauric acid. 6. A mixed magnetic abrasive containing ferromagnetic material particles, abrasive grains, and a binder as main components while being pressed against the object to be polished by a magnetic attraction force, and the mixed magnetic abrasive and the object to be polished. In the magnetic polishing method for polishing the object to be polished by relatively moving and, the mixed magnetic abrasive has 40 to 7 ferromagnetic particles.
A magnetic polishing method characterized in that the mixing ratio is 0% by volume, the abrasive grains are 15 to 35% by volume, and the binder is 15 to 35% by volume. 7. The magnetic polishing method according to claim 6, wherein each component is supplied so as to maintain the range of the mixing ratio of the mixed magnetic abrasive during polishing. 8. A mixed magnetic polishing material containing ferromagnetic material particles, abrasive grains and a binder as main components while being pressed against the object to be polished by a magnetic attractive force, and the mixed magnetic abrasive material and the object to be polished. In the magnetic polishing method for polishing the object to be polished by relatively moving and, a part or all of the magnetic polishing material is exchanged during polishing. 9. A yoke comprising a magnetic circuit, an electromagnet, and a power supply for supplying electric power to the electromagnet, the magnetic polishing material being pressed against the object to be polished arranged in the void portion of the magnetic circuit by a magnetic attraction force. In the magnetic polishing apparatus for polishing the object to be polished by relatively moving the object to be polished and the magnetic abrasive, a magnetic flux number measuring device for detecting a change in the number of magnetic flux of the magnetic circuit is provided, and the magnetic flux number is measured. The magnetic polishing apparatus is characterized in that the electric power of the power source is changed by a device according to the change in the number of magnetic fluxes, and control is performed so as to maintain the number of magnetic fluxes in the magnetic circuit. 10. The magnetic polishing apparatus according to claim 9, further comprising a supply device that supplies a part or all of the components constituting the magnetic polishing material to the object to be polished.