Magnetic barrel polishing method

Abstract

To provide a magnetic barrel polishing method capable of sufficiently polishing a hard metal material used in a noble metal accessory and the like.SOLUTION: A magnetic barrel polishing method arranges a container 6 storing working liquid 9, magnetic media 10 and workpiece 11 in an upper part of a rotating disc 4 arranged with a permanent magnet 7, imparts a change in magnetic flux density to the magnetic media 10 by rotating the rotating disc 4 and driving the magnetic media 10 in the working liquid 9, and polishes the workpiece 11, and polishes the workpiece 11 at a flow rate of the working liquid in a region adjacent to an inner wall surface 6a of the container 6 of -0.2 to 0.4 m / s.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetic barrel polishing method, and more particularly to a polishing method useful for polishing hard metals used in precious metal accessories and the like. [Background technology]

[0002] Magnetic barrel polishing is a type of barrel polishing technology that uses magnetism, in which a processing liquid, magnetic media, and workpieces are placed in a container, and the magnetic media are driven by applying a change in magnetic flux density from the outside, causing them to collide with the workpiece and polish it. This polishing method can polish workpieces with complex shapes by using small pin-shaped magnetic media, so it is widely used in the jewelry industry and other areas as a method for polishing the surfaces of precious metal accessories made by lost-wax precision casting.

[0003] A conventional method is known in which a large number of small abrasive pieces made of a magnetic material are loaded into a container together with the metal to be polished, a disk with alternating south pole zones and north pole zones is rotated on the underside of the container, and the container is placed in a magnetic field in which the south poles and north poles violently convert into each other, causing the small abrasive pieces to rotate violently and become agitated, allowing the small abrasive pieces to penetrate forcefully into the fine details of the metal to be polished, thereby polishing the entire surface evenly (Patent Document 1).

[0004] In addition, a polishing method is known in which an auxiliary member extending in the height direction is provided at a position off the center point of the bottom surface of the polishing container, thereby breaking up the circular swirling flow of the polishing liquid and abrasive, and causing the abrasive to move in the diameter direction as well, thereby expanding the contact with the workpiece and significantly improving the polishing effect (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Tokuhei 04-26981 [Patent Document 2] Patent Publication No. 2001-179598 Summary of the Invention [Problem to be solved by the invention]

[0006] The polishing method described in Patent Document 1 is for polishing small metal products such as rings, ring frames, and precision machine parts efficiently and beautifully with high precision. Materials generally used for precious metal accessories are silver (SV925), gold (K18), platinum (Pt900), etc., and the Vickers hardness of these lost-wax precision castings is about 60 to 140 HV. However, in recent years, the jewelry industry has seen an increase in accessories made of materials that are harder than before, with a hardness of 200 HV or more, and the above polishing method has a problem in that it cannot polish such hard materials sufficiently.

[0007] In addition, the polishing method described in Patent Document 2 aims to improve the polishing effect by increasing the contact with the object to be polished by breaking up the circular swirling flow of the polishing liquid and abrasive. However, the polishing effect was not necessarily sufficient for jewelry made of materials with a hardness of 200 HV or more.

[0008] In general, in magnetic barrel polishing, the movement of the magnetic media creates a water flow in the processing fluid inside the container. It is believed that the greater the kinetic energy of the magnetic media, the higher the processing performance, and so it has been empirically considered that conditions that generate a strong water flow are favorable. However, small workpieces such as precious metal jewelry are processed by the relative collision motion with the magnetic media while being carried by the processing fluid, so it is believed that the generation of the water flow has some effect on the processing performance. To process a hard workpiece, the workpiece and the magnetic media need to collide violently, but depending on how the workpiece is carried in the water flow, even if the magnetic media moves at high speed, it may not collide violently with the workpiece.

[0009] Therefore, the inventors have conducted in-depth research into the effect of water flow on the processing performance of the workpiece, and have found conditions under which it is possible to polish jewelry made of harder precious metal materials than conventional precious metal jewelry by controlling the flow rate of the processing fluid. In other words, the object of the present invention is to provide a magnetic barrel polishing method that can sufficiently polish hard metal materials used in precious metal jewelry. [Means for solving the problem]

[0010] In order to solve the above problems, the magnetic barrel polishing method according to the present invention includes a container containing a machining fluid, magnetic media, and a workpiece, which is disposed above a rotating platen on which a permanent magnet is disposed, and the rotating platen is rotated to change the magnetic flux density to drive the magnetic media in the machining fluid, thereby polishing the workpiece, comprising: The area adjacent to the inner wall surface of the container where the magnetic flux density is |B|<50 mT occupies 3.1 to 12.6% of the area of ​​the area corresponding to the entire bottom surface of the container, The workpiece is polished while the flow velocity of the machining fluid in the region adjacent to the inner wall surface of the container is within a range of −0.2 to 0.4 m / s.

[0011] In addition, in the magnetic barrel polishing method according to the present invention, A magnetic barrel polishing method in which a container containing a processing fluid, magnetic media, and a workpiece is placed above a rotating platen on which a permanent magnet is placed, and the rotating platen is rotated to change the magnetic flux density to drive the magnetic media in the processing fluid and polish the workpiece, In a region corresponding to the entire bottom surface of the container, a first concentric circle is drawn on the inner wall surface of the container, and a second concentric circle having a smaller radius than the first concentric circle but having the same center as the first concentric circle is drawn. Between the first and second concentric circles, there are a region where the magnetic flux density is Bz≧50mT, a region where the magnetic flux density is Bz≦-50mT, a region where the magnetic flux density is Bxy≧50mT, and a region where the magnetic flux density is | B | When the magnetic flux density Bz is greater than or equal to 50 mT and the magnetic flux density Bxy is greater than or equal to 50 mT inside the second concentric circle, the magnetic flux density Bz is greater than or equal to 50 mT or less than or equal to -50 mT inside the first concentric circle, | B | <50mT in the opposite direction to the direction that does not include the area where the magnetic flux density is Bxy ≥ 50mT The above Spin the turntable. Effect of the Invention

[0012] According to the magnetic barrel polishing method of the present invention, the "forward water flow" generated by the revolution motion of the magnetic media in the area adjacent to the inner wall surface of the container and the "reverse water flow" generated by the paddle motion of the magnetic media in the area near the center of the container cancel each other out, and the flow rate of the machining fluid becomes close to zero, improving the machining performance of the magnetic barrel polishing and enabling even hard metal materials to be sufficiently polished. Note that "adjacent" refers to a state of being close and in contact.

[0013] Furthermore, according to the magnetic barrel polishing method of the present invention, by rotating the turntable in an appropriate direction, a "reverse water flow" generated by the paddle motion of the magnetic media can be appropriately generated in the area near the center of the container. [Brief description of the drawings]

[0014] [Figure 1] 1 is a conceptual diagram of a magnetic barrel polishing apparatus used in a magnetic barrel polishing method of the present invention. [Diagram 2] 4 is a plan view showing the arrangement of permanent magnets provided on the upper surface of the rotating disk. FIG. [Diagram 3] This is a schematic diagram of two water currents occurring in a container, causing stagnation at the confluence. [Figure 4] FIG. 4 is a plan view showing the magnetic flux density in a top plate region corresponding to the bottom surface of the container. [Diagram 5] FIG. 1 is a schematic diagram of the paddle motion of magnetic media based on a simplified model. [Figure 6] 1 is a schematic diagram showing the magnetic flux density in a container and the direction in which magnetic media falls. [Figure 7] FIG. 4 is a conceptual diagram showing an example of a machining fluid flow rate measuring means. [Figure 8] This is a graph evaluating the change in flow rate and processing performance depending on the amount of media. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the magnetic barrel polishing method according to the present invention will be described in detail with reference to the drawings. The drawings are schematic representations of a magnetic barrel polishing apparatus used in the magnetic barrel polishing method according to the present invention. The actual dimensions of these items do not necessarily match the dimensions shown in the drawings. Furthermore, duplicated descriptions may be omitted as appropriate, and identical members may be given the same reference numerals. Furthermore, it should be noted that the technical scope of the present invention is not limited to the embodiments described below, but extends to the inventions set forth in the claims and their equivalents.

[0016] A magnetic barrel polishing machine used in the magnetic barrel polishing method of the present invention is shown in Fig. 1. This magnetic barrel polishing machine 1 includes a casing 2, a rotating disk 4 rotated by the drive of a motor 3 arranged inside the casing 2, a top plate 5 arranged on the upper part of the casing 2, and a container 6 placed on the top plate 5.

[0017] A plurality of permanent magnets 7 are arranged on the upper surface of the rotating plate 4. As shown in FIG. 2, the permanent magnets 7 are arranged in a concentric circle around the rotating plate 4, with a circular N-pole permanent magnet 7a and a circular S-pole permanent magnet 7b. In this embodiment, two N-pole permanent magnets 7a and two S-pole permanent magnets 7b are arranged alternately around the rotation center 8 of the rotating plate 4, and two N-pole permanent magnets 7a and two S-pole permanent magnets 7b are arranged alternately around the outside of the rotating plate 4, and four N-pole permanent magnets 7a and four S-pole permanent magnets 7b are arranged around the outside of the rotating plate 4. The outermost N-pole permanent magnets 7a and the outermost S-pole permanent magnets 7b are arranged in pairs of magnets of the same pole along the outer periphery of the rotating plate 4. In this way, the N-pole permanent magnets 7a and the S-pole permanent magnets 7b are arranged in three rows on the upper surface of the rotating plate 4. In addition, on the same circumference, permanent magnets of the same pole are arranged in positions facing each other across the rotation center 8 of the rotating plate 4. By rotating the rotating disk 4 on which the multiple permanent magnets 7 are arranged in this manner, a change in magnetic flux density is imparted, and the magnetic media in the container 6 is driven.

[0018] The container 6 placed on the top plate 5 of the casing 2 has a cylindrical shape. When placing the container 6 on the top plate 5, it is preferable to arrange the container 6 so that the center of the bottom surface of the container 6 is located within 20 mm from the rotation center 8 of the turntable 4. It is more preferable if it is within 10 mm, and even more preferable if it is within 5 mm. If the center of the bottom surface of the container 6 is farther away from the rotation center 8 of the turntable 4 than 20 mm, two water flows wf1 and wf2 as shown in FIG. 3 may be generated in the container 6. In such a case, stagnation of the flow occurs at the confluence 15 of the two water flows wf1 and wf2, making it impossible for the workpiece 11 to change its position, resulting in localized polishing.

[0019] The container 6 contains water 9, which serves as the processing liquid, magnetic media 10, and a workpiece 11. The magnetic media 10 is, for example, a stainless steel pin having a diameter of 0.5 mm and a length of 5.0 mm. The workpiece 11 is made of silver (SV925), gold (K18), platinum (Pt900), which are used as precious metal accessories, as well as precious metal materials with a hardness of 200HV or more and small metal parts for precision machinery.

[0020] As shown in Fig. 4, the area corresponding to the entire bottom surface of the container on the top plate 5 on which the container 6 is placed includes an area 13a where the magnetic flux density is less than 50mT, i.e., an area a4 where the magnetic flux density is B<50mT as shown in Fig. 6, and an area 13b where the magnetic flux density is 50mT or more, i.e., an area a1 where the magnetic flux density is Bz≧50mT, an area a2 where Bz≦-50mT, and an area a3 where Bxy≧50mT as shown in Fig. 6. In particular, in this embodiment, the area 13a where the magnetic flux density is less than 50mT adjacent to the inner wall surface 6a of the container 6 occupies 3.1 to 12.6% of the entire area of ​​the bottom surface of the container 6. If it is less than 3.1%, the revolution of the magnetic medium 10 is not performed sufficiently, and conversely, if it is more than 12.6%, the revolution of the magnetic medium 10 becomes too dominant. This is because in either case, it is difficult to generate a substantially waterless flow in the region adjacent to the inner wall surface 6a of the vessel 6.

[0021] As described above, the size of the container 6 is preferably such that the region 13a adjacent to the inner wall surface 6a of the container 6, where the magnetic flux density is less than 50 mT, is 3.1 to 12.6% of the total area of ​​the bottom surface of the container 6. A container size that satisfies this condition is preferably one in which the diameter of the container bottom is greater than 85 mm and less than or equal to 120 mm. The region adjacent to the inner wall surface 6a of the container 6 refers to a ring-shaped region t with a width of about 15 mm that is formed between the inner wall surface 6a of the container 6 and a circle 6b drawn inside it, as shown by the diagonal lines in FIG. 4.

[0022] When water 9 is poured into the container 6 as the machining fluid, the height of the water surface is preferably at least 1.5 times the thickness of the magnetic media 10 deposited in the container 6. At least 2 times is more preferable, and at least 2.5 times is even more preferable. If the amount of water is less than 1.5 times, there is too little water and it is difficult to invert the workpiece in the water. On the other hand, from the viewpoint of workability, it is desirable to keep the amount of water to 80% or less of the height of the container 6.

[0023] In the present invention, the polishing of the workpiece 11 by the magnetic medium 10 is substantially performed in the region adjacent to the inner wall surface 6a of the container 6, and as described above, polishing is performed in the ring-shaped region t with a width of about 15 mm formed inside the inner wall surface 6a of the container 6. Therefore, it is desirable to perform magnetic barrel polishing in a state where no water flow occurs in the region adjacent to the inner wall surface 6a of the container 6. In the magnetic flux density on the top plate 5 as described above, in the region adjacent to the inner wall surface 6a, the "forward water flow" generated by the revolution motion of the magnetic medium 10 rotating around the rotation axis of the turntable 4 following the rotation of the turntable 4 and the "reverse water flow" generated by the paddle motion near the center of the container where the magnetic medium 10 changes its inclination following the change in magnetic flux density caused by the rotation of the turntable 4 cancel each other out, so that the machining liquid in the region adjacent to the inner wall surface 6a of the container 6 can be made to be a substantially waterless flow.

[0024] FIG. 5 shows a schematic diagram of the paddle motion of the magnetic medium based on a simplified model. In the figure, the arrow A in the magnetic medium 10 indicates the direction of the magnetic moment of the magnetic medium 10, the arrow B in the dashed line indicates the magnetic field lines, the arrow C indicates the moving direction of the permanent magnet 7, and the arrow D indicates the moving direction of the magnetic medium 10. As shown in this figure, the paddle motion refers to the magnetic medium 10 changing its posture from a left tilt to a right tilt in the opposite direction to the moving direction of the magnet. The mechanism of such paddle motion is considered as follows. A torque acts on the magnetic medium 10 so that the direction of its magnetic moment coincides with the direction of the magnetic field lines, so the magnetic medium 10 is aligned along the magnetic field lines. When the permanent magnet 7 moves, a torque acts on the magnetic medium 10, changing its posture, and it paddles while falling in the opposite direction to the moving direction of the permanent magnet 7 as shown in FIG. 5.

[0025] When the magnetic medium 10 paddles, the standing magnetic medium 10 does not fall toward a place with a weak magnetic flux density. In other words, if there are places with strong and weak magnetic flux density in the direction in which the standing magnetic medium 10 is about to fall, it will fall toward the place with the strong magnetic flux density. For example, as shown in FIG. 6, when a first concentric circle and a second concentric circle with a smaller radius than the first concentric circle and the same center are drawn on the inner wall surface of the container in an area corresponding to the entire bottom surface of the container, the first concentric circle and the second concentric circle include an area a1 where the magnetic flux density is Bz≧50mT, an area a2 where Bz≦−50mT, an area a3 where Bxy≧50mT, and an area a4 where B<50mT, and the second concentric circle also includes an area where Bxy≧50mT inside the second concentric circle. These magnetic flux density regions a1, a2, a3, and a4 are values ​​obtained when the magnetic flux density on each of the first and second concentric circles is continuously measured around one circumference in a clockwise or counterclockwise direction. Here, Bz is the vertical component of the magnetic flux density B, and the vertical upward direction is positive. Therefore, the force that lifts the magnetic media 10 is stronger in regions a1 and a2. Also, Bxy is the horizontal component of the magnetic flux density B. Therefore, the force that knocks down the magnetic media is stronger in region a3. Meanwhile, the force that gathers the magnetic media is weaker in region a4. Note that B, Bz, and Bxy have the following relationship: B=√(Bz 2 +Bxy 2 ) As a result of the forces acting on the magnetic media being different in each region, between the first concentric circle c1 and the second concentric circle c2, the magnetic media standing in region a1 or region a2 will experience different paddle motion depending on the direction of rotation of the rotating disk.

[0026] That is, in FIG. 6, when the rotating disk rotates in the clockwise direction d1, the magnetic media standing in the region a1 or region a2 falls in the counterclockwise direction and performs a paddle motion. At this time, the magnetic media falls in the circumferential direction between the first concentric circle c1 and the second concentric circle c2 (the direction in which the magnetic media falls is indicated by the arrow d1'). On the other hand, when the rotating disk rotates in the counterclockwise direction d2, the magnetic media standing in the region a1 or region a2 falls in the clockwise direction and performs a paddle motion, but at this time, the magnetic media falls toward the region a3 where Bxy≧50mT is slightly inside the circumference of the second concentric circle c2 (the direction in which the magnetic media falls is indicated by the arrow d2'). This is because the magnetic flux density in the region a4 is smaller than that in the region a3, so the magnetic media tries to fall toward the region a3 where the force of the fall is stronger than that in the region a4. The magnetic medium is likely to tilt in the direction of arrow d1' as described above when the line e1 extending from region a1 or a2 to region a4 includes region a3, and the magnetic medium is likely to tilt in the direction of arrow d2' when the line e2 extending from region a1 or a2 to region a4 does not include region a3, as shown in Fig. 6. Note that in this embodiment, the lines e1 and e2 extending from region a1 or a2 to region a4 are on the first concentric circle c1, but are not limited thereto and may be on a line extending from region a1 or a2 to region a4 between the first concentric circle c1 and the second concentric circle c2.

[0027] For the above reasons, the paddle motion differs depending on the rotation direction of the turntable 4. In particular, when the magnetic media 10 in the area adjacent to the inner wall surface 6a of the container 6 are tilted slightly inward, the revolution motion of the magnetic media 10 near the inner wall surface 6a is not disturbed, so that the revolution motion near the inner wall surface 6a and the paddle motion near the center are performed simultaneously, and the "forward water flow" generated by the revolution motion of the magnetic media and the "reverse water flow" generated by the paddle motion of the magnetic media in the area near the center of the container cancel each other out, so that the flow rate in the area adjacent to the inner wall surface 6a of the container 6 can be made close to zero. Therefore, when the magnetic media are tilted in the clockwise direction and perform paddle motion, the "reverse water flow" generated by the paddle motion of the magnetic media in the area near the center of the container is more likely to occur than when the magnetic media are tilted in the counterclockwise direction, so it is preferable to rotate the turntable 4 in the counterclockwise direction d2.

[0028] The amount of magnetic media 10 put into the container 6 also affects the likelihood of forward or reverse water flow. That is, the smaller the amount of media, the easier it is to have a forward water flow, and the more the amount of media, the easier it is to have a reverse water flow. Therefore, it is necessary to select an appropriate amount of media. As a means for selecting the amount of media, for example, as shown in FIG. 7, a pitot tube 12 is installed in an area adjacent to the inner wall surface 6a of the container 6 at a height of 20 mm from the top plate 5, and a preferable amount of media can be selected while measuring the water flow velocity parallel to the inner wall surface when the magnetic media is added sequentially while operating the magnetic barrel polishing machine. The preferable amount of media is the amount of media when the rotation direction of the turntable is -0.2 m / s to 0.4 m / s. Moreover, the amount of media when the rotation direction is -0.14 m / s to 0.3 m / s is more preferable, and the amount of media when the rotation direction is -0.07 m / s to 0.2 m / s is even more preferable. With a flow velocity in this range, no upward flow occurs on the wall surface, so the phenomenon of the workpiece floating up is suppressed and the polishing force does not decrease. If the negative flow velocity is greater than -0.2 m / s, the magnetic media moving in a paddle motion may press the workpiece against the inner wall of the container, resulting in polishing only one side of the workpiece. On the other hand, if the positive flow velocity is greater than 0.4 m / s, the proportion of forward water flow increases, which generates an upward flow that causes the workpiece to float, resulting in a decrease in polishing power. The reason why the polishing power is lower the higher the workpiece floats is because the magnetic flux density is weaker at higher positions.

[0029] In addition, the lower the rotation speed of the turntable 4, the smaller the water flow rate can be, but at a low rotation speed, the processing power becomes weak. Therefore, a rotation speed of 200 rpm or more is preferable. More preferably, the rotation speed is 600 rpm or more, and further preferably, the rotation speed is 800 rpm or more. On the other hand, if the rotation speed is too high, the water flow becomes forward, so a rotation speed of 1200 rpm or less is preferable.

[0030] [Example 1] In this example, in order to investigate the effect on the processing performance, the processing performance was evaluated when the flow rate was changed by the amount of media. The mirror-finished workpiece was roughened using a magnetic barrel polishing machine (MBF-300 manufactured by Imahashi Manufacturing Co., Ltd.), and the processing performance was evaluated by the surface roughness. The conditions of the workpiece were as follows. Material of the workpiece: SUS316L, shape of the workpiece: square piece with one side of 15 mm and thickness of 0.3 mm, hardness of the workpiece: 157 HV, surface roughness of the workpiece before the test: Ra 0.04 μm. A cylindrical container with an inner diameter of 100 mm was placed in the center of the top plate of the magnetic barrel polishing machine, and in addition to the above workpiece (0.6 g), 120 g of SUS304 pin media with a diameter of 0.5 mm and a length of 5 mm and 300 ml of water were placed in the container. The water flow velocity was measured when the rotating plate was rotated at 1000 rpm for 15 minutes in a counterclockwise direction (hereafter referred to as CCW) in a plan view. The surface of the workpiece was roughened to increase the surface roughness, and the processing performance was evaluated by the magnitude of the surface roughness Ra after roughening. As described above, the water flow velocity in the area adjacent to the inner wall surface of the container was measured using a Pitot tube. A polypropylene L-shaped tube with an inner diameter of 6 mm, a nose tube of 15 mm, and a base tube of 210 mm was used as a Pitot tube for measuring total pressure. The difference Δh [m] between the water level in the area adjacent to the inner wall surface of the container and the water level inside the Pitot tube was measured, and the flow velocity v was calculated from v = √(2gΔh). Here, v [m / s] is the flow velocity, g [m / s 2 ] is the gravitational acceleration. Furthermore, the surface roughness meter used was a surfcorder DSF1000 manufactured by Kosaka Laboratory. The method for evaluating the surface roughness was based on JIS B 0601:2013. Here, the reference length was 0.8 mm, and the evaluation length was 4 mm. The measurements were performed at three locations on each side of the workpiece (six locations in total). The results of Example 1 are shown in Table 1 and FIG. 8 together with the following Examples 2-4 and Comparative Examples 1-5. In FIG. 8, the error bars indicate the maximum and minimum values.

[0031] [Example 2] The same procedure as in Example 1 was followed except that the amount of media was 80 g. The water flow rate was measured, and the workpiece surface was roughened and the surface roughness Ra after roughening was evaluated.

[0032] [Example 3] The same procedure as in Example 1 was followed except that the amount of media was 100 g. The water flow rate was measured, and the workpiece surface was roughened and the surface roughness Ra after roughening was evaluated.

[0033] [Example 4] The same procedure as in Example 1 was followed except that the amount of media was 150 g. The water flow rate was measured, and the workpiece surface was roughened and the surface roughness Ra after roughening was evaluated.

[0034] [Comparative Example 1] The same procedure as in Example 1 was followed except that the amount of media was 50 g. The water flow rate was measured, and the workpiece surface was roughened and the surface roughness Ra after roughening was evaluated.

[0035] [Comparative Example 2] The same procedure as in Example 1 was followed, except that the amount of media was 50 g and the rotation direction was clockwise (hereinafter referred to as CW). The water flow rate was measured, and the workpiece surface was roughened, and the surface roughness Ra after roughening was evaluated.

[0036] [Comparative Example 3] The same procedure as in Example 1 was followed except that the amount of media was 80 g and the rotation direction was CW. The water flow rate was measured and the workpiece surface was roughened, and the surface roughness Ra after roughening was evaluated.

[0037] [Comparative Example 4] The same procedure as in Example 1 was followed except that the amount of media was 100 g and the rotation direction was CW. The water flow rate was measured and the workpiece surface was roughened, and the surface roughness Ra after roughening was evaluated.

[0038] [Comparative Example 5] The same procedure as in Example 1 was followed except that the amount of media was 150 g and the rotation direction was CW. The water flow rate was measured and the workpiece surface was roughened, and the surface roughness Ra after roughening was evaluated.

[0039] [Table 1]

[0040] From the above results, it was found that in the region adjacent to the inner wall of the container, when the water flow rate is near zero, the surface roughness after roughening is greater than that of each comparative example, and the variation in surface roughness is also smaller than that of each comparative example, resulting in higher machining performance. This is thought to be because when the flow rate is low, the upward flow on the wall is suppressed and the workpiece does not float up, so machining performance does not decrease.

[0041] [Example 5] In this example, the surface roughness of a ring-shaped sample was evaluated to be as small as possible. A 0.3 mm thick SUS316L plate was sandwiched between #600 emery paper and rolled to a processing rate of 10%, to adjust the surface roughness and hardness. The surface roughness was Ra1.07 μm and the Vickers hardness was 204 HV. The plate was attached to the outer surface of a silver (SV925) ring (inner diameter 16 mm) with adhesive tape to obtain a ring-shaped sample. The rotating disk was rotated at a speed of 1000 rpm, rotated in a CCW direction, and magnetic barrel polishing was performed with a media amount of 120 g, and the water flow rate was measured and the surface roughness of the sample was measured. The results of Example 5 and Comparative Example 6 are shown in Table 2.

[0042] [Comparative Example 6] Magnetic barrel polishing was carried out in the same manner as in Example 5, except that the amount of media was 50 g.

[0043] [Table 2]

[0044] From the above results, it was found that the surface roughness can be reduced by selecting an appropriate amount of media so that the water flow velocity is close to zero. As with the roughening process, it is believed that if the flow velocity is small, the upward flow on the wall surface is suppressed and the workpiece does not float up, so the polishing power does not decrease.

[0045] [Example 6-12] In this example, the magnetic flux density distribution in the container was changed by changing the size of the container used, and the relationship between the ratio of the area of ​​the region adjacent to the inner wall surface of the container where the magnetic flux density is less than 50 mT and the flow rate of water was investigated. In this example, when the diameter of the container was changed to 95 mm, 100 mm, and 120 mm, the total area of ​​the region adjacent to the inner wall surface of the container where the magnetic flux density is less than 50 mT was in the range of 3.1 to 12.6% of the total area of ​​the bottom surface of the container. The amount of media was in the range of 80 to 170 g, and the rotation speed of the rotating disk was in the range of 700 to 1200 rpm. It was confirmed that the flow rate of water became zero in all containers. The results of Examples 6-12 are shown in Table 3 together with Comparative Examples 7-15 and 16-24.

[0046] [Comparative Example 7-15] The relationship between the ratio of the area of ​​the region adjacent to the inner wall surface of the container where the magnetic flux density is less than 50 mT and the water flow rate was investigated when the size of the container used was 85 mm in diameter. The amount of media and the rotation speed of the rotating disk were the same as in Example 6-12. In this case, the total area of ​​the region adjacent to the inner wall surface of the container where the magnetic flux density is less than 50 mT was 2.2% of the total area of ​​the bottom surface of the container, and the water flow rate could not be reduced to zero.

[0047] [Comparative Examples 16-24] The relationship between the ratio of the area of ​​the region adjacent to the inner wall surface of the container where the magnetic flux density is less than 50 mT and the water flow rate was investigated when the size of the container used was 150 mm in diameter. The amount of media and the rotation speed of the turntable were the same as in Example 6-12. The total area of ​​the region adjacent to the inner wall surface of the container where the magnetic flux density is less than 50 mT was 25.6% of the total area of ​​the bottom surface of the container, and in this case the water flow rate could not be reduced to zero.

[0048] [Table 3] [Explanation of symbols]

[0049] 1 Magnetic barrel polishing machine 2 Casing 3 Motor 4 Turntable 5. Tabletop 6 containers 6a Inner wall surface of container 6b A circle indicating a position approximately 15 mm inside the inner wall of the container 7. Permanent Magnets 7a N pole permanent magnet 7b S pole permanent magnet 8 Rotation Center 9 Water (processing fluid) 10 Magnetic media 11 Work 12 Pitot tube 13 Top area equivalent to the entire bottom surface of the container 13a Magnetic flux density area below 50mT 13b Area with magnetic flux density of 50mT or more 15 Confluence A The direction of the magnetic moment of the magnetic media B magnetic field lines C Magnet movement direction D Direction of magnetic media movement a1 Region where magnetic flux density Bz≧50mT a2 Magnetic flux density Bz≦-50mT region a3 Region where magnetic flux density Bxy ≧ 50mT a4 Magnetic flux density B<50mT c1 First concentric circle c2 Second concentric circle d1 Clockwise direction of the wheel d1' The direction in which the magnetic media falls when the rotating disk rotates clockwise d2 Counterclockwise rotation of the wheel d2' The direction in which the magnetic media falls when the rotating disk rotates counterclockwise e1 On a line going counterclockwise from the area where the magnetic flux density is Bz≧50mT or Bz≦-50mT to the area where B<50mT e2 On a line going clockwise from the area where the magnetic flux density is Bz≧50mT or Bz≦-50mT to the area where B<50mT wf1,wf2 water flow

Claims

1. A magnetic barrel polishing method in which a container containing a machining fluid, magnetic media, and workpieces is placed above a turntable on which a permanent magnet is arranged, and the turntable is rotated to change the magnetic flux density and drive the magnetic media in the machining fluid to polish the workpiece, wherein an area adjacent to the inner wall surface of the container where the magnetic flux density is |B|<50 mT occupies 3.1 to 12.6% of the area of ​​an area equivalent to the entire bottom surface of the container, and the flow rate of the machining fluid in the area adjacent to the inner wall surface of the container is within a range of -0.2 to 0.4 m / s, and the workpiece is polished in the magnetic barrel polishing method.

2. A magnetic barrel polishing method in which a container containing a processing fluid, magnetic media, and workpieces is placed above a turntable on which a permanent magnet is arranged, and the turntable is rotated to change the magnetic flux density to drive the magnetic media in the processing fluid and polish the workpieces, wherein a first concentric circle is drawn on the inner wall surface of the container in an area corresponding to the entire bottom surface of the container, and a second concentric circle having the same center as the first concentric circle and a smaller radius than the first concentric circle is drawn, and a region where the magnetic flux density is Bz ≧ 50 mT is defined between the first concentric circle and the second concentric circle. a region where the magnetic flux density is Bz≦-50mT, a region where the magnetic flux density is Bxy≧50mT, and a region where the magnetic flux density is |B|<50mT, and the region where the magnetic flux density is Bxy≧50mT is also included inside a second concentric circle, the magnetic barrel polishing method rotating the turntable in a direction opposite to a direction that does not include a region where the magnetic flux density is Bxy≧50mT on a line that is between the first and second concentric circles and extends from the region where the magnetic flux density is Bz≧50mT or Bz≦-50mT to the region where the magnetic flux density is |B|<50mT.

3. A magnetic barrel polishing method in which a container containing machining fluid, magnetic media and workpieces is placed above a turntable on which a permanent magnet is arranged, and the turntable is rotated to change the magnetic flux density to drive the magnetic media in the machining fluid and polish the workpieces, wherein the flow rate of the machining fluid in a ring-shaped area approximately 15 mm wide adjacent to the inner wall surface of the container is within the range of -0.2 to 0.4 m / s.

4. A magnetic barrel polishing method described in any one of claims 1 to 3, wherein the magnetic media revolves along the rotational direction of the turntable in the area adjacent to the inner wall surface of the container, and performs a paddle motion in the area near the center excluding the area adjacent to the inner wall surface of the container.

5. A magnetic barrel polishing method as described in claim 4, wherein, in the region adjacent to the inner wall surface of the container, a forward water flow generated by the orbital motion of the magnetic media and a reverse water flow generated by the paddle motion of the magnetic media cancel each other out.

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