Method for controlling rotation speed in centrifugal barrel polishing and centrifugal barrel polishing method

Abstract

The present invention reduces chipping that occurs in a workpiece during acceleration of a barrel tank.　This method for controlling rotation speed includes an acceleration control step for calculating a constant Ct based on a number Nt (rpm) of revolutions per minute while polishing, a number nt (rpm) of rotations per minute while polishing, a revolution radius R (m) of a barrel tank (12), and gravitational acceleration g (9.8 m / s2) according to formula (1): (1): Ct = (2πＮt / 60)2·Ｒ / (g·nt), defining a relative centrifugal acceleration F(G) based on a number N (rpm) of revolutions per minute of the barrel tank (12) during acceleration control, the revolution radius R (m) of the barrel tank (12), and gravitational acceleration g (9.8 m / s2) according to formula (2): (2): F = (2πＮ / 60)2·Ｒ / g, and varying over time the number N (rpm) of revolutions per minute of the barrel tank (12) during acceleration control and a number n (rpm) of rotations per minute of the barrel tank (12) during acceleration control so as to satisfy formula (3): (3): F / n ≥ Ct.

Description

Method for controlling rotation speed in centrifugal barrel polishing and centrifugal barrel polishing method

[0001] The present invention relates to a method for controlling the rotation speed in centrifugal barrel polishing and a centrifugal barrel polishing method.

[0002] Patent Document 1 discloses a centrifugal barrel polishing machine having a rotary table rotated by a drive motor and a barrel tank attached at an eccentric position on the rotary table. The barrel tank revolves integrally with the rotary table and rotates relative to the rotary table, thereby performing planetary rotation. Workpieces are polished by abrasive stones inside the barrel tank during planetary rotation.

[0003] JP 2010-005712 A

[0004] In centrifugal barrel polishing, if the centrifugal force acting on the barrel tank is weak relative to the rotational speed of the barrel tank, chipping, i.e., abnormal defects, can occur in the workpiece. Therefore, the revolution speed and rotational speed during barrel polishing are set to speeds that take chipping reduction into consideration. However, conventional common knowledge has not considered chipping reduction during the acceleration process from a stopped state until the barrel tank reaches a polishing rotational speed suitable for chipping reduction. Therefore, in the barrel polishing apparatus described in Reference 1, the rotation of the turntable and the rotational speed of the barrel tank are driven by only one drive motor, and during the acceleration process from a stopped state until the revolutional speed of the turntable and the rotational speed of the barrel tank reach the target rotational speed suitable for polishing, the rotational speed increases at the same rate as the revolutional speed. Because centrifugal force is proportional to the square of the revolutional speed, during the acceleration process, the centrifugal force remains relatively small compared to the rotational speed, raising concerns about chipping of the workpiece. Once acceleration is complete and the target rotation speed suitable for polishing is reached, the process transitions to the barrel polishing process, maintaining the target rotation speed, making it difficult to verify the chipping condition of the workpiece during the acceleration process.

[0005] The present invention was developed in light of the above circumstances, and an object of the present invention is to reduce chipping that occurs in workpieces during acceleration of a barrel tank.

[0006] The first disclosed method for controlling the rotation speed in centrifugal barrel polishing is a method for controlling the rotation speed of a barrel tank, into which a workpiece is placed, to be accelerated from a stopped state until the rotation speed reaches the revolution speed during polishing and the rotation speed during polishing, in centrifugal barrel polishing, in which polishing is performed by planetary rotating a barrel tank into which a workpiece is placed at a predetermined revolution speed during polishing and a rotation speed during polishing, and ｔ (rpm) and the number of rotations per minute during polishing n ｔ (rpm), the revolution radius R (m) of the barrel tank, and the gravitational acceleration g (9.8 m / s ２ ) and a constant C based on ｔ , as expressed in equation (1) C ｔ = (2πN ｔ / 60) ２ ・R / (g・n ｔ ) (1) is calculated by the revolution speed N (rpm) of the barrel tank during acceleration control, the revolution radius R (m) of the barrel tank, and the gravitational acceleration g (9.8 m / s ２ ) and the relative centrifugal acceleration F (G) based on the equation (2) F = (2πN / 60) ２ The revolution speed N (rpm) of the barrel tank during acceleration control and the rotation speed n (rpm) of the barrel tank during acceleration control are defined by the following formula (3): F / n≧C ｔ The acceleration control step includes changing the acceleration with time so as to satisfy the following expression (3).

[0007] The centrifugal barrel polishing method of the second disclosure is the method of the first disclosure, wherein the revolution direction and the rotation direction of the barrel tank are opposite to each other, and the rotation speed during polishing is n ｔ (rpm) is expressed as a positive number, and the revolution speed N ｔ the acceleration control step in which (rpm) is expressed as a negative value, and the barrel tank is rotated in a manner that satisfies the formula (4): −1≦n ｔ / N ｔ The revolution speed N during polishing is set in the range of <0 (4) ｔ (rpm) and the rotation speed n during polishing ｔand a constant speed polishing step in which polishing is performed by planetary rotation at 1000 rpm.

[0008] This configuration can reduce chipping of the workpieces during acceleration of the barrel tank.

[0009] Figure 1 is a plan view of a centrifugal barrel finishing machine according to an embodiment. Figure 2 is a cross-sectional view of the centrifugal barrel finishing machine. Figure 3 is a graph showing the change in rotation speed and relative centrifugal acceleration over time in Experiment 1. Figure 4 is a graph showing the change in rotation speed and relative centrifugal acceleration over time in Experiment 2. Figure 5 is a graph showing the change in rotation speed and relative centrifugal acceleration over time in Experiment 3. Figure 6 is a graph showing the change in rotation speed and relative centrifugal acceleration over time in Example 10 of Experiment 4. Figure 7 is a graph showing the change in rotation speed and relative centrifugal acceleration over time in Example 11 of Experiment 4.

[0010] First, embodiments of the present disclosure will be listed and explained. Any combination of the following embodiments without causing any contradiction is also included in the embodiments for carrying out the invention. The first disclosed method for controlling the rotation speed in centrifugal barrel polishing is as follows: [1] In centrifugal barrel polishing, in which polishing is performed by planetary rotating a barrel tank into which workpieces are placed at a predetermined polishing revolution rotation speed and polishing rotation rotation speed, the method accelerates and controls the rotation speed of the barrel tank from a rotation stop state until the rotation speed reaches the polishing revolution rotation speed and polishing rotation rotation speed, and the polishing revolution rotation speed N per minute is set to 0.05. ｔ (rpm) and the number of rotations per minute during polishing n ｔ (rpm), the revolution radius R (m) of the barrel tank, and the gravitational acceleration g (9.8 m / s ２ ) and a constant C based on ｔ , as expressed in equation (1) C ｔ = (2πN ｔ / 60) ２ ・R / (g・n ｔ ) (1) is calculated by the revolution speed N (rpm) of the barrel tank per minute during acceleration control, the revolution radius R (m) of the barrel tank, and the gravitational acceleration g (9.8 m / s ２) and the relative centrifugal acceleration F (G) based on the equation (2) F = (2πN / 60) ２ The revolution speed N (rpm) of the barrel tank during acceleration control and the rotation speed n (rpm) of the barrel tank during acceleration control are defined by the following formula (3): F / n≧C ｔ The acceleration control step includes changing the acceleration with time so as to satisfy the following expression (3).

[0011] The centrifugal force acting on the barrel tank is proportional to the relative centrifugal acceleration F. When the revolution speed N and the rotation speed n are controlled so that the formula (3) is equal, the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n during acceleration control is ｔ When the revolution speed N and the rotation speed n are controlled so that the formula (3) is unequal, the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n during acceleration control is maintained at the same value as the ratio of the rotation speed n during polishing ｔ According to the present disclosure, in the acceleration control process of increasing the revolution speed N and the rotation speed n of the barrel tank, the ratio of the centrifugal force to the rotation speed n is maintained at a value greater than the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n during polishing. ｔ The occurrence of chipping due to the ratio of centrifugal force to the axial direction being smaller than the ratio of the centrifugal force to the axial direction is suppressed.

[0012] [2] The acceleration control step preferably includes a revolution-limited acceleration step of increasing the revolution speed N (rpm) without changing the rotation speed n (rpm) from a state where the barrel tanks are stopped from rotating. According to this configuration, the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n increases rapidly immediately after the start of the acceleration control, which is highly effective in suppressing chipping.

[0013] [3] In [1] or [2], it is preferable that the rotational axis of the barrel tank is vertical. If the rotational axis of the barrel tank is horizontal, the direction and magnitude of the resultant force of centrifugal force and gravity acting on the barrel tank changes depending on the position in the revolution path of the barrel tank. Therefore, the flow state of the mass in the barrel tank also varies depending on the position in the revolution path of the barrel tank, which can cause the mass to flow violently and become prone to chipping. In contrast, if the rotational axis of the barrel tank is vertical, the centrifugal force acting on the barrel tank is always horizontal and is not affected by gravitational acceleration acting in the vertical direction, so a state in which chipping is less likely to occur can be maintained.

[0014] The centrifugal barrel polishing method of the second disclosure is [4] described in [1] to [3], wherein the revolution direction and the rotation direction of the barrel tank are opposite to each other, and the rotation speed during polishing is n ｔ (rpm) is expressed as a positive number, and the revolution speed N ｔ the acceleration control step in which (rpm) is expressed as a negative value, and the barrel tank is rotated in a manner that satisfies the formula (4): −1≦n ｔ / N ｔ The revolution speed N during polishing is set in the range of <0 (4) ｔ (rpm) and the rotation speed n during polishing ｔ and a constant-speed polishing process in which polishing is performed by planetary rotation at a constant rotation speed of 1000 rpm. According to this configuration, in the process of centrifugal barrel polishing in which the barrel tank is rotated in planetary rotation at a constant rotation speed, chipping of the workpiece is suppressed. Therefore, chipping can be consistently suppressed from the start of the acceleration control process to the end of the polishing process.

[0015] <Embodiment 1> A first embodiment of the present invention will now be described with reference to Figures 1 to 7. Figures 1 and 2 show a centrifugal barrel finishing machine 10 for performing the centrifugal barrel finishing method of this embodiment 1. The centrifugal barrel finishing method involves planetary rotation of a barrel tank 12 attached to a turret 11, thereby polishing workpieces (not shown) within the barrel tank 12. The centrifugal barrel finishing method involves sequentially performing an acceleration control process, a constant-speed polishing process, and a deceleration control process.

[0016] 1 and 2, the centrifugal barrel finishing machine 10 has a revolution shaft 13 whose axis is oriented vertically and which rotates integrally with the turret 11, and a revolution motor 15 which transmits rotational force to the revolution shaft 13 via a revolution belt 14. The revolution motor 15 is a motor whose output rotation speed can be varied by inverter control. The revolution shaft 13 and the turret 11 are rotated by the revolution motor 15.

[0017] A plurality of barrel tanks 12 (four in this embodiment) are attached to the turret 11. The barrel tanks 12 are arranged at equal angular intervals in the circumferential direction at positions eccentric to the center of rotation of the turret 11 (the center of the revolution shaft 13) in the radial direction. Each barrel tank 12 is rotatable integrally with a rotation shaft 16 whose axis is oriented vertically. The rotation force of a rotation motor 18 is transmitted to the rotation shaft 16 via a rotation belt 17. The rotation motor 18 is a motor whose rotation speed can be changed by inverter control. The barrel tanks 12 and the rotation shaft 16 are rotated by the rotation motor 18. Each barrel tank 12 is rotatable relative to the turret 11. In a plan view of the barrel tanks 12 parallel to the revolution shaft 13 and the rotation shaft 16, the inner surface (not shown) of the barrel tank 12 forms a regular polygon.

[0018] The rotation speed of the revolution motor 15 and the rotation motor 18 are individually controlled by a control device 19. By individually driving and rotating the revolution motor 15 and the rotation motor 18, the barrel tanks 12 rotate (relatively rotate) on their axes with respect to the turret 11 while revolving integrally with the turret 11, performing planetary rotation. In a plan view, the revolution direction of the barrel tanks 12 (the rotation direction of the turret 11) and the rotation direction of the barrel tanks 12 are opposite to each other.

[0019] In the planetary rotating barrel tank 12, the fluidized layer on the surface of the mass (not shown) containing the workpiece and the grinding stones (not shown) flows like an avalanche, and the workpiece is polished by the grinding stones. If the fluidized layer of the mass is thick, chipping of the workpiece is likely to occur, and if the fluidized layer is thin, chipping of the workpiece is suppressed. Therefore, in the constant speed polishing process in which the barrel tank 12 is rotated in planetary rotation at a constant rotation speed, the revolution speed (hereinafter referred to as "revolution speed during polishing N") is set to a value that takes into consideration the suppression of chipping. ｔ (rpm)) and the rotation speed (hereinafter referred to as "rotation speed during polishing n ｔ Specifically, the revolution speed N ｔ and the rotation speed during polishing n ｔ is expressed by the formula (4) -1≦n ｔ / N ｔ <0 (4) Since the revolution direction and rotation direction of the barrel tank 12 are opposite to each other, the rotation speed n ｔ is expressed as a positive number, and the revolution speed during polishing is N ｔ is expressed as a negative number. ｔ / N ｔ is a negative value.

[0020] The inventors of the present application have determined that the rotational speed of the barrel tank 12 is increased from the state in which the rotation of the barrel tank 12 is stopped to the revolution speed N ｔ and the rotation speed during polishing n ｔ This acceleration control method was devised based on the knowledge that if the centrifugal force acting on the barrel tanks 12 is weak relative to the rotation speed of the barrel tanks 12, the mass fluidized layer becomes thick, making the workpieces more likely to chip, and on the experiments described below.

[0021] [Experiment 1] In Experiment 1, a centrifugal barrel finishing machine 10 was used, in which the revolution radius R of the barrel tank 12 was 0.18 m. Tipton Corporation's HS-3 grinding stones (not shown), each shaped like a ball with a diameter of 3 mm, were placed in the barrel tank 12, along with a 10 mm x 5 mm x 2 mm rectangular magnet network (not shown). The amount of grinding stones placed was such that the volume, including the gaps between the grinding stones, was 50% of the volume of the barrel tank 12.

[0022] In Experiment 1, the revolution speed N of the barrel tank 12 was increased from the stopped state to the polishing revolution speed N ｔ The rotation speed was increased (accelerated) at a constant rate to reach (446 rpm). ｔ is the target revolution speed N (rpm) to be achieved in the acceleration control process in Examples 1 to 4. In the following description, "increasing the revolution speed of the barrel tank 12" and "accelerating the rotation speed of the barrel tank 12" are used synonymously. The revolution speed N of the barrel tank 12 per minute, the revolution radius R (m) of the barrel tank 12, and the gravitational acceleration g (9.8 m / s ２ ) and the relative centrifugal acceleration F (G) based on the equation (2) F = (2πN / 60) ２ It is expressed as: R / g (2) The relative centrifugal acceleration F is proportional to the square of the revolution speed N. In experiment 1, the relative centrifugal acceleration F reaches 40 G 30 seconds after the rotation has stopped.

[0023] In Experiment 1, four examples of acceleration control were performed in which the rotational speed n of the barrel tank 12 was increased in different ways, while the revolution speed N was increased in the same manner. In all four examples, the rotational speed n (rpm) was increased from a stopped state to the polishing rotational speed n in 30 seconds. ｔ The rotation speed during polishing was increased to reach (300 rpm). ｔ is the target rotation speed n to be achieved in the acceleration control process in Examples 1 to 4. The results of Experiment 1 are shown in Table 1 and FIG.

[0024]

[0025] In the first conventional example, the rotation speed n is increased at a constant acceleration from a stopped state, similar to the revolution speed N.

[0026] In Examples 1 to 3, the revolution speed N ｔ is set to 446 rpm, the revolution radius of the barrel tank 12 is set to 0.18 m, and the rotation speed during polishing n ｔ is set to 300 rpm, and the relative centrifugal acceleration F ｔ The rotation speed during polishing is n ｔ Constant C divided by ｔ Formulas (2-1) and (3') F ｔ = (2πN ｔ / 60) ２ ・R / g...(2-1) C ｔ =F ｔ / n ｔ ....(3') is calculated by the constant C ｔ The revolution speed N and rotation speed n in the acceleration control process are calculated using the following formulas (2) and (3-1): F = (2πN / 60) ２ The ratio was changed over time so as to satisfy the following conditions: R / g (2) F / n≧0.1334 (3-1).

[0027] In the first embodiment, the rotation speed n was changed for each elapsed time so as to satisfy the following equation (5-1): n=F / 0.1334 (5-1).

[0028] In Example 2, the rotation of the barrel tanks 12 was kept stopped (the rotation speed n was not increased) from the rotation stopped state until 22.5 seconds, and the rotation speed n was increased from 0 rpm to 300 rpm at a constant rate (constant acceleration) for 7.5 seconds from 22.5 seconds to 30 seconds. In Example 3, the rotation speed n at each elapsed time was calculated using the exponential function exp (0.1901 × each elapsed time).

[0029] As described above, the experiment of stopping the revolution and rotation of the barrel tank 12 after performing acceleration control for 30 seconds was repeated 40 times for each example, and the chipping rate of the workpieces was evaluated. Conventional Example 1 had the highest chipping rate among the four examples, and Example 1 had the next lowest chipping rate after Conventional Example 1. The chipping rates of Examples 2 and 3 were similar and lower than Example 1. The chipping rates of Conventional Example 1, Example 1, Examples 2 and 3 were evaluated as "B: medium," "A: low," and "AA: very low," respectively.

[0030] The reason why the chipping rate in Examples 1 to 3 is lower than that in Conventional Example 1 can be inferred as follows: In Conventional Example 1, the rotation speed n was increased at the same constant rate (acceleration) as the revolution speed N, so the centrifugal force was smaller than the rotation speed n, resulting in more chipping. In contrast, in Examples 1 to 3, attention was focused on the relative centrifugal acceleration F, which is proportional to the square of the revolution speed N, and the revolution speed N during polishing ｔ and the rotation speed during polishing n ｔ and a constant C based on the revolution radius R ｔ The revolution speed N (relative centrifugal acceleration F) in the acceleration control process and the rotation speed n in the acceleration control process are calculated using the formula F / C ｔ 3, the area on the straight line representing Example 1 and the area above the straight line representing Example 1 are areas where the revolution speed N and the rotation speed n are equal to or greater than the constant C ｔ In Figure 3, the more the graph showing the change in revolution speed N and rotation speed n bulges upward to the left, the less chipping occurs in the workpiece.

[0031] [Experiment 2] The centrifugal barrel finishing machine 10, grinding stone, workpiece, and the manner in which the revolution speed N was increased were the same as those used in Experiment 1. In Experiment 2, the manner in which the revolution speed N was increased was the same, and four examples of acceleration control were performed in which the rotation speed n of the barrel tank 12 was increased in different ways. In all four examples, the rotation speed n was increased from a stopped state to 100 rpm in 30 seconds. The results of Experiment 2 are shown in Table 2 and Figure 4.

[0032]

[0033] In Conventional Example 2, the rotation speed n is increased at a constant acceleration from a stopped state, similar to the revolution speed N.

[0034] In Examples 4 to 6, the revolution speed N ｔ is set to 446 rpm, the revolution radius of the barrel tank 12 is set to 0.18 m, and the rotation speed during polishing n ｔ is set to 100 rpm, and the relative centrifugal acceleration F ｔ The rotation speed during polishing is n ｔ Constant C divided by ｔ Formulas (2-1) and (3') F ｔ = (2πN ｔ / 60) ２ ・R / g...(2-1) C ｔ =F ｔ / n ｔ ....(3') is calculated by the constant C ｔ The revolution speed N and rotation speed n in the acceleration control process are calculated using the following formulas (2) and (3-2): F = (2πN / 60) ２ The ratio was changed over time so as to satisfy the following conditions: R / g (2) F / n≧0.4003 (3-2).

[0035] In Example 4, the rotation speed n was changed for each elapsed time so as to satisfy the following equation (5-2): n=F / 0.4003 (5-2).

[0036] The acceleration control step in Example 5 includes a revolution-limited acceleration step in which only the revolution rotation speed N is increased without changing the rotation rotation speed n. In Example 5, the rotation of the barrel tanks 12 was kept stopped (the rotation rotation speed n was not increased) from the rotation stop state until 20 seconds, and the rotation rotation speed n was increased from 0 rpm to 100 rpm at a constant rate (constant acceleration) over 10 seconds from 20 seconds to 30 seconds. In Example 6, the rotation rotation speed n at each elapsed time was set to a value calculated using the exponential function exp (0.1535 × each elapsed time).

[0037] As described above, the experiment in which the revolution and rotation of the barrel tank 12 were stopped after 30 seconds of acceleration control was repeated 40 times for each example, and the chipping rate of the workpieces was evaluated. Conventional Example 2 had the highest chipping rate among the four examples, and was similar to Example 1 of Experiment 1. Example 4 had the next lowest chipping rate after Conventional Example 2, and was similar to Examples 2 and 3. The chipping rates of Examples 5 and 6 were similar and lower than Example 4. The chipping rates of Conventional Example 2, Example 4, Examples 5 and 6 were evaluated as "A: low," "AA: very low," and "AAA: extremely low," respectively.

[0038] Conventional Example 2 and Examples 4 to 6 in Experiment 2 had a lower chipping rate than Conventional Example 1 and Examples 1 to 3 in Experiment 1. The reason for this is that the revolution rotation speed N was the same in Experiment 1 and Experiment 2, whereas the rotation rotation speed n ｔ (100 rpm) is the rotation speed n during polishing in Experiment 2 ｔ 4, the area on the line representing Example 4 and above the line representing Example 4 is where the revolution speed N and the rotation speed n are equal to the constant C ｔ This is a chipping reduction region that changes to satisfy the formula (3-2) including:

[0039] [Experiment 3] The centrifugal barrel finishing machine 10, grinding stone, and workpiece used in Experiment 3 were the same as those used in Experiments 1 and 2. The manner in which the revolution speed N was increased was different from that in Experiments 1 and 2. The revolution speed N was increased (accelerated) at a constant rate from a stopped state to 300 rpm in 30 seconds. In Experiment 3, the relative centrifugal acceleration F reached 18 G 30 seconds after the rotation stopped state.

[0040] In Experiment 3, four examples of acceleration control were performed in which the rotational speed n of the barrel tanks 12 was increased in different ways, while the revolution speed N was increased in the same manner. In all four examples, the rotational speed n was increased from a stopped state to 300 rpm in 30 seconds. The results of Experiment 3 are shown in Table 3 and FIG. 5.

[0041]

[0042] In Conventional Example 3, the rotation speed n is increased at a constant acceleration from a stopped state, similar to the revolution speed N.

[0043] In Examples 7 to 9, the revolution speed N ｔ is set to 300 rpm, the revolution radius of the barrel tank 12 is set to 0.18 m, and the rotation speed during polishing n ｔ is set to 300 rpm, and the relative centrifugal acceleration F ｔ The rotation speed during polishing is n ｔ Constant C divided by ｔ Formulas (2-1) and (3') F ｔ = (2πN ｔ / 60) ２ ・R / g...(2-1) C ｔ =F ｔ / n ｔ ....(3') is calculated by the constant C ｔ The revolution speed N and rotation speed n in the acceleration control process are calculated using the following formulas (2) and (3-3): F = (2πN / 60) ２ The ratio was changed over time so as to satisfy the following conditions: R / g (2) F / n≧0.0604 (3-3).

[0044] In Example 7, the rotation speed n was changed for each elapsed time so as to satisfy the following equation (5-3): n=F / 0.0604 (5-3).

[0045] The acceleration control step in Example 10 includes a revolution-limited acceleration step in which only the revolution rotation speed N is increased without changing the rotation rotation speed n. In Example 8, the rotation of the barrel tanks 12 was kept stopped (the rotation rotation speed n was not increased) from the rotation stop state until 22.5 seconds, and the rotation rotation speed n was increased from 0 rpm to 300 rpm at a constant rate (constant acceleration) over 7.5 seconds from 22.5 seconds to 30 seconds. In Example 9, the rotation rotation speed n at each elapsed time was calculated using the exponential function exp (0.1901 × each elapsed time).

[0046] The experiment in which the revolution and rotation of the barrel tank 12 were stopped after the acceleration control for 30 seconds as described above was repeated 40 times for each example, and the chipping rate of the workpieces was evaluated. Conventional Example 3 had the highest chipping rate among the four examples. Example 7 had the next lowest chipping rate after Conventional Example 3, and was similar to Conventional Example 1. The chipping rates of Examples 8 and 9 were similar, lower than Example 7, and similar to Examples 1 and Conventional Example 2. The chipping rates of Conventional Example 3, Example 7, Examples 8, and 9 were evaluated as "C: high," "B: medium," and "A: low," respectively.

[0047] Conventional Example 3 and Examples 7 to 9 in Experiment 3 had a higher chipping rate overall than Conventional Example 1 and Examples 1 to 3 in Experiment 1. The reason for this is that the revolution speed N ｔ (300 rpm) is the revolution speed N during polishing in Experiment 1 ｔ (446 rpm), and the relative centrifugal acceleration F (18.1 G) in Experiment 3 is also lower than the relative centrifugal acceleration F (40 G) in Experiment 1, which is thought to be due to the instability of the mass flow.

[0048] In the graph of FIG. 5, the area above the line representing Example 7 and the line representing Example 4 is where the revolution speed N and the rotation speed n are equal to the constant C. ｔ In Examples 7 to 9, the revolution rotation speed N and the rotation rotation speed n were changed within this chipping reduction region, so the chipping rate was lower than in Example 3.

[0049] [Experiment 4] The centrifugal barrel finishing machine 10, grinding stone, and workpiece used in Experiment 4 were the same as those used in Experiments 1 to 3. The manner in which the revolution speed N increased was different from Experiments 1 to 3, and the revolution speed N during polishing increased from the stopped state to 15 seconds. ｔ (446 rpm), and then from 15 seconds to 30 seconds, the revolution speed during polishing is N ｔ maintained.

[0050] In Experiment 4, two examples of acceleration control were performed in which the rotational speed n of the barrel tanks 12 was increased in different ways, while the revolution speed N was increased in the same manner. In both examples, the rotational speed n was increased from a stopped state to 300 rpm in 30 seconds. The results of Experiment 4 are shown in Table 4 and Figures 6 and 7.

[0051]

[0052] The acceleration control step of Example 10 includes a revolution limited acceleration step of increasing only the revolution speed N without changing the rotation speed n. In Example 10, the revolution speed N is increased from the rotation stop state to the polishing revolution speed N ｔ The rotation of the barrel tank 12 was stopped (the rotation speed n was not increased) for 15 seconds until the rotation speed reached 300 rpm, and then the rotation speed n was increased from 0 rpm to 300 rpm at a constant rate (constant acceleration) for 15 seconds from 15 seconds to 30 seconds. The changes in the revolution speed N and the rotation speed n in Example 10 are shown in Figure 6. The chipping rate in Example 10 was rated "AA: very low."

[0053] In Example 11, the revolution speed N from the rotation stop state is increased to the revolution speed N ｔ During the 15 seconds until the rotation speed reaches 446 rpm, the constant C ｔ The revolution speed N and the rotation speed n are changed so as to satisfy the formula (3-4) using a constant Ca larger than (0.1334): F / n=Ca (3-4) During the period from 15 seconds to 30 seconds, the revolution speed N during polishing is ｔ The rotation speed n was increased while maintaining the value N. The change in the revolution speed N and the rotation speed n in Example 11 is shown in Figure 7. The chipping rate in Example 11 was "AA: very low."

[0054] [Experiment 5] In Experiment 5, barrel polishing was performed using the same centrifugal barrel polishing machine 10 as in Experiments 1 to 4. In the barrel polishing, 50 vol% of the same abrasive stone HS-3 as in Experiments 1 to 4 was placed in the barrel tank 12, and 10 of the same magnetic networks as in Experiments 1 to 4 were placed therein.

[0055] In Example 12, the revolution speed N and rotation speed n of the barrel tank 12 are accelerated in the same manner as in Conventional Example 1, and then the revolution speed N during polishing is set to the same value as in Conventional Example 1. ｔ and the rotation speed during polishing n ｔ In Example 13, the revolution speed N and rotation speed n of the barrel tank 12 were accelerated in the same manner as in Conventional Example 2, and then the revolution speed N during polishing was set to the same value as in Conventional Example 2. ｔ and the rotation speed during polishing n ｔ In Example 14, the revolution speed N and rotation speed n of the barrel tank 12 were accelerated in the same manner as in Conventional Example 3, and then the revolution speed N during polishing was increased to the same value as in Conventional Example 3. ｔ and the rotation speed during polishing n ｔ Polishing was carried out for 5 minutes.

[0056] For each of Examples 12 to 14, the chipping rate and edge rounding were measured 10 times after 5 minutes of polishing. The edge rounding is the radius at the center of the length of a 10 mm corner edge on the outer surface of the magnetic network. The values ​​for the chipping rate and edge rounding of the corners shown in Table 5 are the average values ​​for 10 pieces x 10 times = 100 pieces.

[0057]

[0058] In Examples 12 and 14, the rotation speed during polishing was n ｔ Although the values ​​are the same, the chipping rate in Example 12 is lower than that in Example 14, and the amount of rounding of the edges of the workpieces, which is the amount of polishing in Example 12, is about 1.5 times greater than that in Example 14. This is thought to be because in Example 12, the relative centrifugal acceleration F is large, so the mass is pressed against the inner wall of the barrel tank 12, the thickness of the fluidized layer is thin, and the workpieces flow stably within the mass.

[0059] In Examples 12 and 13, the revolution speed N ｔ Although the number of rotations during polishing n in Example 13 is the same, the chipping rate in Example 13 is lower than that in Example 12. The amount of edge rounding in Example 13 is smaller than that in Example 12 and is equivalent to that in Example 14. ｔis smaller than that of Example 12, so in Example 13, the mass is pressed against the outer side of the inner wall of the barrel tank 12, and the rotation speed n during polishing is lower than that of Example 12. ｔ This is thought to be because the thickness of the fluidized bed became thinner, and the workpieces flowed extremely slowly and stably within the mass.

[0060] The rotation speed control method of the first embodiment is to rotate the barrel tank 12 into which the workpieces are loaded at a predetermined revolution speed N per minute during polishing. ｔ and the rotation speed during polishing n ｔ In the centrifugal barrel polishing, the polishing is performed by planetary rotation at 1000 rpm, and the rotation speed of the barrel tank 12 is changed from the rotation stop state to the revolution speed N ｔ and the rotation speed during polishing n ｔ This is a method of controlling acceleration until the target is reached.

[0061] This acceleration control method includes the following acceleration control step: In this acceleration control step, the number of revolutions N per minute during polishing is set to N ｔ and the number of rotations per minute during polishing n ｔ and a constant C based on the revolution radius R of the barrel tank 12 and the gravitational acceleration g. ｔ , as expressed in equation (1) C ｔ = (2πN ｔ / 60) ２ ・R / (g・n ｔ ) (1) Furthermore, the relative centrifugal acceleration F based on the revolution speed N per minute of the barrel tank 12 during acceleration control, the revolution radius R of the barrel tank 12, and the gravitational acceleration g is calculated by the following formula (2): F=(2πN / 60) ２ R / g (2) Then, the revolution speed N of the barrel tank 12 per minute during acceleration control and the rotation speed n of the barrel tank 12 per minute during acceleration control are defined by the following formula (3): F / n≧C ｔ .... (3) is changed over time to satisfy the following.

[0062] The centrifugal force acting on the barrel tank 12 is proportional to the relative centrifugal acceleration F. When the revolution speed N and the rotation speed n are controlled so that the formula (3) is equal, the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n during acceleration control is ｔ When the revolution speed N and the rotation speed n are controlled so that the formula (3) is unequal, the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n during acceleration control is maintained at the same value as the ratio of the rotation speed n during polishing ｔ According to the first embodiment, in the acceleration control process for increasing the revolution speed N and the rotation speed n of the barrel tank 12, the ratio of the centrifugal force to the rotation speed n is maintained at a value greater than the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotation speed n during polishing. ｔ The occurrence of chipping due to the ratio of centrifugal force to the axial direction being smaller than the ratio of the centrifugal force to the axial direction is suppressed.

[0063] The acceleration control process in Examples 2, 5, 8, and 10 includes a revolution-limited acceleration process in which the revolution speed N is increased without changing the rotation speed n, starting from a state in which the rotation of the barrel tanks 12 is stopped. This control process makes it possible to maintain a high ratio of centrifugal force (relative centrifugal acceleration F) to the rotation speed n immediately after the start of acceleration control, thereby effectively suppressing chipping.

[0064] When the central axis of rotation of the barrel tank 12 is horizontal, the direction and magnitude of the resultant force of centrifugal force and gravity acting on the barrel tank 12 change depending on the position in the revolution path of the barrel tank 12. Therefore, the flow state of the fluidized mass layer in the barrel tank 12 also varies depending on the position in the revolution path of the barrel tank 12, which can cause the mass to flow violently and lead to a state in which chipping is likely to occur. In view of this, in the first embodiment, the axes of the revolution axis 13 and the rotation axis 16, which are the central axes of rotation of the barrel tank 12, are set vertically. If the central axis of rotation of the barrel tank 12 is vertical, the centrifugal force acting on the barrel tank 12 is always horizontal and is not affected by gravitational acceleration acting in the vertical direction, so that a state in which chipping is unlikely to occur can be maintained.

[0065] Examples 12, 13, and 14 of the centrifugal barrel polishing method of the present embodiment 1 include the acceleration control step and the constant speed polishing step. ｔ The rotation speed of the barrel tank 12 during polishing is defined as n ｔ When the above definition is given, in the constant speed polishing process, the following formula (4) is satisfied: −1≦n ｔ / N ｔ <0... (4) The revolution speed N during polishing is set in the range ｔ and the rotation speed during polishing n ｔ The barrel tank 12 was rotated in a planetary rotation at a speed of n ｔ is a positive number, and the revolution speed during polishing N ｔ is a negative number. ｔ / N ｔ is a negative value. As shown in Table 5, in all of Examples 12, 13, and 14, n ｔ / N ｔ The value of satisfies the above formula. According to the barrel polishing method of the present embodiment 1, chipping of the workpiece is suppressed in the constant-speed polishing process in which the barrel tanks 12 are rotated in planetary rotation at a constant rotation speed to perform centrifugal barrel polishing. Therefore, chipping of the barrel tanks 12 can be consistently suppressed from the start of the acceleration control process to the end of the polishing process.

[0066] Other Embodiments The present invention is not limited to the first embodiment described above and illustrated in the drawings. The technical scope of the present invention also includes the following embodiments. In the barrel finishing machine of the first embodiment, the rotational axis of the barrel tank is vertical, but the axial direction of the rotational axis (the revolution axis and the rotation axis) of the barrel tank may be horizontal. Even when the rotational axis of the barrel tank is horizontal, the acceleration control method disclosed herein can reduce the chipping rate compared to conventional acceleration methods. In the acceleration control process of Experiments 1 to 4, the revolution speed N was increased until the relative centrifugal acceleration F reached a target value of 18 G or 40 G. However, the target value of the relative centrifugal acceleration F in the acceleration control process may be set to approximately 5 G to 15 G, which is the range of conventional centrifugal barrel finishing. In this case, too, in the polishing process, it is preferable to set the value obtained by dividing the rotational speed n by the revolution speed N so as to satisfy the relationship -1≦n / N<0. In the above-mentioned conventional examples 1 to 3 and examples 1 to 14 of the first embodiment, the workpiece and the grinding stone are placed in the barrel tank, and the workpiece is polished by the grinding stone. However, it is also possible to place only the workpiece in the barrel tank, and perform "co-polishing" in which the workpieces come into contact with each other and polish each other. In this case, too, the occurrence of chipping in the workpiece can be suppressed by the acceleration control method of the present disclosure. In the deceleration process after the constant speed polishing process, the revolution speed N during polishing is added to the formula (2) ｔ The relative centrifugal acceleration obtained by substituting ｔ Then, the following equation (5) F≧F ｔ -C ｔ By controlling the deceleration so that the rotation speed n per minute of the barrel tank is changed over time so as to satisfy the following equation (5), it is possible to suppress the occurrence of chipping during the deceleration process.

[0067] 10... Centrifugal barrel finishing machine 12... Barrel tank 13... Revolution axis (rotation center axis) 16... Rotation axis (rotation center axis)

Claims

1. In centrifugal barrel polishing, in which polishing is performed by planetary rotating a barrel tank into which a workpiece is placed at a predetermined polishing revolution rotation speed and polishing rotation rotation speed, a rotation speed control method is provided for accelerating and controlling the rotation speed of the barrel tank from a stopped state until it reaches the polishing revolution rotation speed and polishing rotation rotation speed, ｔ (rpm) and the number of rotations per minute during polishing n ｔ (rpm), the revolution radius R (m) of the barrel tank, and the gravitational acceleration g (9.8 m / s ２ ) and a constant C based on ｔ , as expressed in equation (1) C ｔ = (2πN ｔ / 60) ２ ・R / (g・n ｔ ) (1) is calculated by the revolution speed N (rpm) of the barrel tank during acceleration control, the revolution radius R (m) of the barrel tank, and the gravitational acceleration g (9.8 m / s ２ ) and the relative centrifugal acceleration F (G) based on the equation (2) F = (2πN / 60) ２ The revolution speed N (rpm) of the barrel tank during acceleration control and the rotation speed n (rpm) of the barrel tank during acceleration control are defined by the following formula (3): F / n≧C ｔ A method for controlling the rotation speed in centrifugal barrel polishing, including an acceleration control step of changing the rotation speed over time so as to satisfy the following expression (3).

2. A method for controlling the rotation speed in centrifugal barrel polishing as described in claim 1, wherein the acceleration control process includes a revolution-limited acceleration process for increasing the revolution speed N (rpm) without changing the rotation speed n (rpm) from a state in which the barrel tank is stopped from rotating.

3. A method for controlling the rotation speed in centrifugal barrel polishing according to claim 1 or 2, wherein the central axis of rotation of the barrel tank is vertical.

4. The method according to claim 1 or 2, wherein the revolution direction and rotation direction of the barrel tank are opposite to each other, and the rotation speed during polishing is n ｔ (rpm) is expressed as a positive number, and the revolution speed N ｔ the acceleration control step in which (rpm) is expressed as a negative value, and the barrel tank is rotated in a manner that satisfies the formula (4): −1≦n ｔ / N ｔ The revolution speed N during polishing is set in the range of <0 (4) ｔ (rpm) and the rotation speed n during polishing ｔ and a constant speed polishing step in which polishing is performed by planetary rotation at 1000 rpm.

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