Method for controlling rotational 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

[Technical Field]

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

[0002] Patent Document 1 discloses a centrifugal barrel polishing apparatus having a rotary table driven by a drive motor and a barrel tank mounted at an eccentric position on the rotary table. The barrel tank revolves integrally with the rotary table and rotates on its own axis relative to the rotary table, thereby undergoing planetary rotation. Within the planetary rotating barrel tank, the workpiece is polished by polishing stones. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2010-005712 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In centrifugal barrel polishing, if the centrifugal force acting on the barrel is weak relative to the barrel's rotational speed, chipping, or abnormal defects, will occur in the workpiece. Therefore, the rotational speed and the revolving speed during barrel polishing are set to speeds that take chipping into consideration. However, conventional technical knowledge has not considered chipping reduction during the acceleration process from the polishing stop state until the barrel reaches a polishing rotational speed suitable for chipping reduction. For example, in the barrel polishing apparatus described in Reference 1, the rotation of the rotary table and the rotation of the barrel are driven by only one drive motor, and during the acceleration process from the rotation stop state until the rotational speed of the rotary table and the rotational speed of the barrel reach a target rotational speed suitable for polishing, the rotational speed increases at the same rate as the rotational speed. Since centrifugal force is proportional to the square of the rotational speed, during the acceleration process, the centrifugal force remains relatively small relative to the rotational speed, raising concerns that chipping may occur in the workpiece. Once acceleration is complete and the target rotational speed suitable for polishing is reached, the process transitions to barrel polishing while maintaining that target rotational speed. Therefore, it was difficult to verify the condition of the workpiece during the acceleration process.

[0005] This invention was completed based on the circumstances described above, and aims to reduce chipping that occurs on the workpiece during acceleration in a barrel tank. [Means for solving the problem]

[0006] The rotational speed control method in centrifugal barrel polishing described in the first disclosure is: In centrifugal barrel polishing, in which workpieces are polished by rotating a barrel tank into which workpieces are fed at a predetermined orbital speed and rotational speed during polishing, a rotational speed control method is provided for accelerating the rotational speed of the barrel tank from a stopped state until it reaches the predetermined orbital speed and rotational speed during polishing, The number of revolutions per minute during polishing N t (rpm) and the number of rotations per minute during polishing n t (rpm), the orbital radius R of the barrel tank (m), and the acceleration due to gravity g (9.8 m / s²) 2 ) and the constant C based ont is calculated by the mathematical formula (1) C t =(2πN t / 60) 2 ·R / (g·n t )·····(1) and is defined by the relative centrifugal acceleration F (G) based on the number of revolutions N (rpm) per minute 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 ) by the mathematical formula (2) F=(2πN / 60) 2 ·R / g·····(2) and includes an acceleration control step of changing it over time so as to satisfy the number of revolutions N (rpm) per minute of the barrel tank during acceleration control and the number of revolutions n (rpm) per minute of the barrel tank during acceleration control by the mathematical formula (3) F / n≧C<� t ·····(3) .

[0007] The centrifugal barrel polishing method of the second disclosure in the first disclosure, has the revolution direction and the rotation direction of the barrel tank opposite to each other, and the acceleration control step in which the rotation speed n t (rpm) represents a positive numerical value and the revolution speed N t (rpm) represents a negative numerical value, and a constant-speed polishing step of performing polishing by causing the barrel tank to perform planetary rotation at the revolution speed N (rpm) and the rotation speed n t / N t <0·····(4) within the range of setting t and the rotation speed n t (rpm) during polishing.

Advantages of the Invention

[0008] According to this configuration, it is possible to reduce the impact on the workpiece during the acceleration of the barrel tank.

Brief Description of the Drawings

[0009] [Figure 1] Figure 1 is a plan view of the centrifugal barrel polishing machine of the embodiment. [Figure 2] Figure 2 is a cross-sectional view of a centrifugal barrel polishing machine. [Figure 3] Figure 3 is a graph showing the changes over time in rotational speed and relative centrifugal acceleration in Experiment 1. [Figure 4] Figure 4 is a graph showing the changes in rotational speed and relative centrifugal acceleration over time in Experiment 2. [Figure 5] Figure 5 is a graph showing the changes in rotational speed and relative centrifugal acceleration over time in Experiment 3. [Figure 6] Figure 6 is a graph showing the changes over time in rotational speed and relative centrifugal acceleration in Example 10 of Experiment 4. [Figure 7] Figure 7 is a graph showing the changes over time in rotational speed and relative centrifugal acceleration in Example 11 of Experiment 4. [Modes for carrying out the invention]

[0010] First, embodiments of this disclosure will be listed and described. Any combination of the following embodiments, in a manner that does not create a contradiction, is also included as a form for carrying out the invention. The rotational speed control method in centrifugal barrel polishing described in the first disclosure is: [1] In centrifugal barrel polishing, in which workpieces are polished by rotating a barrel tank into which the workpiece is fed at a predetermined polishing orbital rotation speed and polishing rotation speed, a rotation speed control method for accelerating the rotation speed of the barrel tank from a rotation stop state until it reaches the polishing orbital rotation speed and polishing rotation speed, wherein the polishing orbital rotation speed per minute N t (rpm) and the number of rotations per minute during polishing n t (rpm), the orbital radius R of the barrel tank (m), and the acceleration due to gravity g (9.8 m / s²) 2 ) and the constant C based on t Formula (1) Ct =(2πN t / 60) 2 ·R / (g·n t )·····(1) The following is calculated: the rotational speed N (rpm) of the barrel tank per minute during acceleration control, the orbital radius R (m) of the barrel tank, and the acceleration due to gravity g (9.8 m / s²). 2 The relative centrifugal acceleration F(G) based on ) is given by equation (2) F = (2πN / 60) 2 ·R / g·····(2) Defined by the formula (3), the orbital rotation speed N (rpm) of the barrel tank per minute during acceleration control and the rotational rotation speed n (rpm) of the barrel tank per minute during acceleration control are given by the formula (3). F / n≧C t ...(3) This includes an acceleration control process that changes over time to satisfy the condition.

[0011] The centrifugal force acting on the barrel tank is proportional to the relative centrifugal acceleration F. When the orbital rotation speed N and rotational rotation speed n are controlled so that equation (3) is equal, the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotational rotation speed n during acceleration control is equal to the rotational rotation speed n during polishing. t The ratio of centrifugal force (relative centrifugal acceleration F) to the rotational speed n is maintained at the same value. When the orbital speed N and rotational speed n are controlled such that equation (3) is an inequality, the ratio of centrifugal force (relative centrifugal acceleration F) to the rotational speed n during acceleration control is the same as the rotational speed n during polishing. t A value greater than the ratio of centrifugal force (relative centrifugal acceleration F) to the rotational speed n is maintained. According to this disclosure, in an acceleration control process that increases the orbital speed N and rotational speed n of the barrel tank, the ratio of centrifugal force to rotational speed n is greater than the rotational speed n during polishing. t The occurrence of chipping caused by a ratio smaller than that of centrifugal force is suppressed.

[0012] [2] The acceleration control step preferably includes an orbital-limited acceleration step in which the rotational speed N (rpm) is increased without changing the rotational speed n (rpm) from the state in which the rotation of the barrel tank has stopped. With this configuration, the ratio of centrifugal force (relative centrifugal acceleration F) to rotational speed n increases rapidly immediately after the start of acceleration control, so the effect of suppressing chipping is high.

[0013] In [3][1] or [2], It is preferable that the rotation axis of the barrel tank is in the vertical direction. If the rotation axis of the barrel tank is in the horizontal direction, the direction and magnitude of the resultant force of centrifugal force and gravity acting on the barrel tank will change depending on the position in the barrel tank's orbital path. As a result, the flow state of the mass inside the barrel tank will also fluctuate depending on the position in the barrel tank's orbital path, and a state in which the mass flow becomes violent and chipping is likely to occur may occur. In contrast, if the rotation axis of the barrel tank is in the vertical direction, the centrifugal force acting on the barrel tank is always in the horizontal direction and is not affected by the acceleration of gravity 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 As described in [4][1]~[3], the orbital direction and rotational direction of the barrel bath are opposite to each other, and the rotational speed during polishing is n t (rpm) is expressed as a positive number, and the rotational speed N during polishing is expressed as a positive value. t The acceleration control process in which (rpm) is expressed as a negative value, The aforementioned barrel tank is given by equation (4) -1≦n t / N t <0·····(4) The polishing rotation speed N set within the range t (rpm) and the rotational speed n during polishing. t The process includes a constant-speed polishing step in which the barrel is polished by planetary rotation at (rpm). With this configuration, in the step of centrifugal barrel polishing in which the barrel is rotated planetarily at a constant rotation speed, the occurrence of chipping of the workpiece is suppressed. Therefore, the occurrence of chipping can be consistently suppressed from the start of the acceleration control step until the end of the polishing step.

[0015] <Embodiment 1> Hereinafter, Embodiment 1 of the present invention will be described with reference to Figures 1 to 7. Figures 1 and 2 show a centrifugal barrel polishing machine 10 for carrying out the centrifugal barrel polishing method of Embodiment 1. The centrifugal barrel polishing method is a method of polishing a workpiece (not shown) in a barrel tank 12 by rotating a barrel tank 12 attached to a turret 11 in a planetary pattern. The centrifugal barrel polishing method is a method that sequentially carries out an acceleration control step, a constant speed polishing step, and a deceleration control step.

[0016] As shown in Figures 1 and 2, the centrifugal barrel polishing machine 10 has a revolving shaft 13 that rotates integrally with the turret 11 with its axis oriented vertically, and a revolving motor 15 that transmits rotational force to the revolving shaft 13 via a revolving belt 14. The revolving motor 15 is a motor whose output rotational speed can be varied by inverter control. The revolving shaft 13 and the turret 11 are rotationally driven by the revolving motor 15.

[0017] Multiple (four in this embodiment) barrel tanks 12 are attached to the turret 11. The multiple barrel tanks 12 are arranged at equal angular intervals in the circumferential direction, eccentrically outward in the radial direction from the rotation center of the turret 11 (center of the orbital axis 13). Each barrel tank 12 is capable of rotating integrally with the rotation axis 16, whose axis is oriented vertically. The rotational force of the rotation motor 18 is transmitted to the rotation axis 16 via the rotation belt 17. The rotation motor 18 is a motor whose rotational speed can be changed by inverter control. The barrel tanks 12 and the rotation axis 16 are rotationally driven by the rotation motor 18. Each barrel tank 12 is rotatable relative to the turret 11. In a plan view of the barrel tank 12 parallel to the orbital axis 13 and the rotation axis 16, the inner surface of the barrel tank 12 (not shown) is a regular polygon.

[0018] The rotational speed of the orbital motor 15 and the rotational speed of the rotational motor 18 are individually controlled by the control device 19. By individually rotating the orbital motor 15 and the rotational motor 18, the barrel tank 12 orbits integrally with the turret 11 while rotating on its own axis (relative rotation) relative to the turret 11, thus performing planetary rotation. In a plan view, the direction of orbit of the barrel tank 12 (the direction of rotation of the turret 11) and the direction of rotation of the barrel tank 12 are opposite.

[0019] In the planetary rotating barrel tank 12, the fluidized layer on the surface of the mass (not shown) containing the workpiece and polishing stones (not shown) flows in an avalanche-like manner, and the workpiece is polished by the polishing stones. If the fluidized layer of the mass is thick, chipping is likely to occur on the workpiece, and if the thickness of the fluidized layer is thin, the occurrence of chipping on the workpiece is suppressed. Therefore, in a constant-speed polishing process in which the barrel tank 12 is planetarily rotated at a constant rotation speed, the rotational speed (hereinafter referred to as "rotational speed N during polishing") is set considering the suppression of chipping. t (rpm) and rotational speed (hereinafter referred to as "rotational speed n during polishing") t The setting is "(rpm)". Specifically, the rotational speed N during polishing. t and the rotational speed n during polishing t This is formula (4) -1≦n t / N t <0·····(4) It is set to satisfy the following conditions. Since the orbital direction and rotational direction of the barrel tank 12 are opposite, the rotational speed during polishing is n t This is expressed as a positive number, and the rotational speed during polishing is N. t This is represented by a negative number. Therefore, n t / N t It is a negative value.

[0020] The inventor of this application has determined that, starting from a state where the rotation of the barrel bath 12 is stopped, the rotational speed of the barrel bath 12 is the rotational speed N during polishing. t and the rotational speed n during polishing tWe have devised an acceleration control method that can suppress the occurrence of chipping during the acceleration process leading up to the final stage. This acceleration control method was devised based on the finding that if the centrifugal force acting on the barrel tank 12 is weak relative to the rotational speed of the barrel tank 12, the fluidized bed of the mass becomes thicker, making it easier for chipping to occur on the workpiece, and on experiments described later.

[0021] [Experiment 1] In Experiment 1, a centrifugal barrel polishing machine 10 with a barrel tank 12 having an orbital radius R of 0.18 m was used. The barrel tank 12 was filled with HS-3 polishing stones (not shown), manufactured by Chipton Co., Ltd., which are ball-shaped with a diameter of 3 mm, and one rectangular magnet network (not shown) measuring 10 mm × 5 mm × 2 mm. The amount of polishing stones added was such that the volume, including the gaps between the stones, accounted for 50% of the volume of the barrel tank 12.

[0022] In Experiment 1, the rotational speed N of the barrel bath 12 was determined to be the rotational speed N during polishing after 30 seconds from a stopped state. t The rotational speed during polishing was increased (accelerated) at a constant rate to reach (446 rpm). t This is the target rotational speed N (rpm) to be reached in the acceleration control process of Examples 1 to 4. In the following description, "increasing the rotational speed of the barrel tank 12" and "accelerating the rotational speed of the barrel tank 12" are used synonymously. The rotational speed N of the barrel tank 12 per minute, the orbital radius R (m) of the barrel tank 12, and the acceleration due to gravity g (9.8 m / s²) are used. 2 The relative centrifugal acceleration F(G) based on ) is given by equation (2) F = (2πN / 60) 2 ·R / g·····(2) This is expressed as follows: The relative centrifugal acceleration F is proportional to the square of the orbital rotation speed N. In Experiment 1, the relative centrifugal acceleration F reaches 40G 30 seconds after the rotation has stopped.

[0023] In Experiment 1, four different acceleration control methods were performed, with the same pattern of increase in the orbital rotation speed N, but with different ways of increasing the rotational rotation speed n of the barrel tank 12. In all four cases, the rotational rotation speed n (rpm) was increased from a stopped state to the rotational rotation speed n during polishing after 30 seconds.t The rotation speed during polishing was increased to reach (300 rpm). t This represents the target rotational speed n to be reached in the acceleration control process of Examples 1 to 4. The results of Experiment 1 are shown in Table 1 and Figure 3.

[0024] [Table 1]

[0025] In the conventional example 1, the rotational speed n was increased at a constant acceleration from a state of rotational cessation, similar to the revolutionary speed N.

[0026] In Examples 1-3, the rotational speed during polishing was N. t The rotation speed during polishing is set to 446 rpm, the orbital radius of the barrel tank 12 is set to 0.18 m, and the rotation speed during polishing is n t With the rotation speed set to 300 rpm, the relative centrifugal acceleration F during polishing is... t The rotation speed n during polishing t The 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') Calculated by the constant C t = 0.1334 was obtained. The orbital rotation speed N and rotational rotation speed n in the acceleration control process are given by the following equations (2) and (3-1). F = (2πN / 60) 2 ·R / g·····(2) F / n≧0.1334·····(3-1) The data was modified over time to satisfy the given conditions.

[0027] In Example 1, the rotational speed n is calculated for each elapsed time using formula (5-1) n = F / 0.1334 ·····(5-1) It was modified to satisfy the condition.

[0028] In Example 2, the rotation of the barrel tank 12 was kept stopped (the rotation speed n was not increased) from the rotation stop state until 22.5 seconds, and then the rotation speed n was increased at a constant rate (constant acceleration) from 0 rpm to 300 rpm over a period of 7.5 seconds from 22.5 seconds to 30 seconds. In Example 3, the rotation speed n for 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 30 seconds of acceleration control was repeated 40 times in each example, and the chipping rate in the workpiece was evaluated. Of the four examples, Conventional Example 1 had the highest chipping rate, and Example 1 had the next lowest chipping rate. The chipping rates of Example 2 and Example 3 were similar and lower than that of Example 1. The chipping rates of Conventional Example 1, Example 1, Example 2 and 3 were evaluated as "B: moderate," "A: low," and "AA: very low," respectively.

[0030] The reason why the chipping rate in Examples 1-3 is lower than in Conventional Example 1 can be inferred as follows: In Conventional Example 1, the rotational speed n was increased at a constant rate (acceleration) similar to the revolutionary speed N, resulting in a smaller centrifugal force compared to the rotational speed n, leading to a high incidence of chipping. In contrast, in Examples 1-3, attention was paid to the relative centrifugal acceleration F, which is proportional to the square of the revolutionary speed N, and the revolutionary speed N during polishing was used. t and the rotational speed n during polishing t The constant C is based on the orbital radius R. t The orbital rotation speed N (relative centrifugal acceleration F) and the rotational rotation speed n in the acceleration control process are calculated using a mathematical formula. F / C t ≥n·····(3) The condition was changed to satisfy the given value. In the graph of Figure 3, the area on the line representing Example 1 and the area above the line representing Example 1 are such that the orbital rotation speed N and the rotational rotation speed n are the constant C mentioned above. t This is a region where chipping is reduced, as it changes to satisfy the formula including the following. In Figure 3, the more the graph showing the changes in orbital rotation speed N and rotational rotation speed n bulges upward to the left, the less chipping occurs in the workpiece.

[0031] [Experiment 2] The centrifugal barrel polishing machine 10, polishing stones, workpiece, and the method of increasing the rotational speed N used in Experiment 2 are the same as in Experiment 1. In Experiment 2, while keeping the method of increasing the rotational speed N the same, four different acceleration control methods were performed in which the rotational speed n of the barrel tank 12 increased. In all four cases, the rotational speed n was increased so that it reached 100 rpm in 30 seconds from a stopped state. The results of Experiment 2 are shown in Table 2 and Figure 4.

[0032] [Table 2]

[0033] In the conventional example 2, the rotational speed n was increased at a constant acceleration from a state of rotational cessation, similar to the revolutionary speed N.

[0034] In Examples 4-6, the rotational speed N during polishing was t The rotation speed during polishing is set to 446 rpm, the orbital radius of the barrel tank 12 is set to 0.18 m, and the rotation speed during polishing is n t With the rotation speed set to 100 rpm, the relative centrifugal acceleration F during polishing is calculated. t The rotation speed n during polishing t The 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') Calculated by the constant C t = 0.40003 was obtained. The orbital rotation speed N and rotational rotation speed n in the acceleration control process are given by the following equations (2) and (3-2). F = (2πN / 60) 2 ·R / g·····(2) F / n≧0.4003·····(3-2) The data was modified over time to satisfy the given conditions.

[0035] In Example 4, the rotational speed n is given by formula (5-2) for each elapsed time. n = F / 0.4003 ·····(5-2) It was modified to satisfy the condition.

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

[0037] As described above, the experiment of stopping the revolution and rotation of the barrel tank 12 after 30 seconds of acceleration control was repeated 40 times in each example, and the rate of chipping in the workpiece was evaluated. Of the four examples, Conventional Example 2 had the highest chipping rate, which was about the same as Example 1 in Experiment 1. The next lowest chipping rate was in Example 4, which was about the same as Examples 2 and 3. The chipping rates of Examples 5 and 6 were about the same, and lower than in 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 4-6 in Experiment 2 have a lower chipping rate compared to Conventional Example 1 and Examples 1-3 in Experiment 1. The reason for this is that the orbital rotation speed N is the same in Experiment 1 and Experiment 2, whereas the rotational rotation speed n during polishing in Experiment 1 is the same. t (100 rpm) is the rotational speed n during polishing in Experiment 2. t The reason for this is likely that the mass flow was more stable because it was lower than (300 rpm). Also, in the graph of Figure 4, the region on the line representing Example 4 and the region above the line representing Example 4 are such that the orbital rotation speed N and the rotational rotation speed n are equal to the constant C mentioned above. t This is a region where chipping occurrence is reduced, which changes to satisfy formula (3-2) including the following:

[0039] [Experiment 3] The centrifugal barrel polishing machine 10, polishing stones, and workpieces used in Experiment 3 are the same as those in Experiments 1 and 2. Different from Experiments 1 and 2, the rising pattern of the revolution rotation speed N was increased (accelerated) at a constant rate from the rotation stop state to reach 300 rpm in 30 seconds. In Experiment 3, 30 seconds after the rotation stop state, the relative centrifugal acceleration F becomes 18G.

[0040] In Experiment 3, with the same rising pattern of the revolution rotation speed N, four cases of acceleration control with different ways of increasing the rotation speed n of the barrel tank 12 were carried out. In all four cases, the rotation speed n was increased from the rotation stop state to reach 300 rpm in 30 seconds. The results of Experiment 3 are shown in Table 3 and Figure 5.

[0041]

Table 3

[0042] In Conventional Example 3, the rotation speed n was increased from the rotation stop state with a constant acceleration, similar to the revolution rotation speed N.

[0043] In Examples 7 to 9, the revolution rotation speed N during polishing t was set to 300 rpm, the revolution radius of the barrel tank 12 was set to 0.18 m, and after setting the rotation speed n during polishing t to be 300 rpm, the relative centrifugal acceleration F during polishing t was divided by the rotation speed n during polishing t to obtain a constant C t using the mathematical formulas (2-1) and (3’) F t =(2πN t / 60) 2 ·R / g·····(2-1) C t =F t / n t ·····(3’) and a constant C t = 0.0604 was obtained. The revolution rotation speed N and the rotation speed n in the acceleration control process are given by the following mathematical formulas (2) and (3-3) F = (2πN / 60) 2 ·R / g·····(2) F / n≧0.0604·····(3-3) The data was modified over time to satisfy the given conditions.

[0044] In Example 7, the rotational speed n is given by formula (5-3) for each elapsed time. n = F / 0.0604 ·····(5-3) It was modified to satisfy the condition.

[0045] The acceleration control step in Example 10 includes an orbit-limited acceleration step in which only the orbital speed N is increased without changing the rotational speed n. In Example 8, the rotation of the barrel tank 12 was kept stopped (the rotational speed n was not increased) from the rotation-stopped state until 22.5 seconds, and then the rotational 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 rotational speed n for each elapsed time was calculated using the exponential function exp(0.1901 × each elapsed time).

[0046] As described above, the experiment of stopping the revolution and rotation of the barrel tank 12 after 30 seconds of acceleration control was repeated 40 times in each example, and the chipping rate in the workpiece was evaluated. Conventional Example 3 had the highest chipping rate among the four examples. The next lowest chipping rate was in Example 7, which was about the same as Conventional Example 1. The chipping rates of Examples 8 and 9 were about the same, lower than Example 7, and about the same as Example 1 and Conventional Example 2. The chipping rates of Conventional Example 3, Example 7, Example 8 and 9 were evaluated as "C: High," "B: Medium," and "A: Low," respectively.

[0047] In Experiment 3, Conventional Example 3 and Examples 7-9 had a higher chipping rate overall than Conventional Example 1 and Examples 1-3 in Experiment 1. The reason for this was the rotational speed N during polishing in Experiment 3. t (300 rpm) is the rotational speed N during polishing in Experiment 1. tThe relative centrifugal acceleration F (18.1G) in Experiment 3 is lower than (446 rpm), and the relative centrifugal acceleration F (40G) in Experiment 1 is also lower, suggesting that the cause is unstable mass flow.

[0048] In the graph of Figure 5, the region on the line representing Example 7 and the region above the line representing Example 4 are such that the orbital rotation speed N and the rotational rotation speed n are the constant C mentioned above. t This is a chipping reduction region that changes to satisfy formula (3-3) which includes the following. In Examples 7 to 9, the orbital rotation speed N and the rotational rotation speed n were changed within this chipping reduction region, so the chipping rate is lower than in Example 3.

[0049] [Experiment 4] The centrifugal barrel polishing machine 10, polishing stone, and workpiece used in Experiment 4 are the same as in Experiments 1-3. The pattern of increase in the rotational speed N differs from Experiments 1-3, with the rotational speed N increasing from a stopped state to the polishing rotational speed N in 15 seconds. t The rotational speed during polishing is increased (accelerated) at a constant rate until it reaches (446 rpm), and then from 15 to 30 seconds, the rotational speed during polishing is N t They maintained it.

[0050] In Experiment 4, two different acceleration control methods were performed, with the same pattern of increase in the orbital rotation speed N, but with different ways of increasing the rotational rotation speed n of the barrel tank 12. In both cases, the rotational rotation speed n was increased to reach 300 rpm in 30 seconds from a state of rotation halt. The results of Experiment 4 are shown in Table 4 and Figures 6 and 7.

[0051] [Table 4]

[0052] The acceleration control step of Example 10 includes an orbital-limited acceleration step that increases only the orbital speed N without changing the rotational speed n. In Example 10, the orbital speed N is increased from a rotation-stopped state to the orbital speed N during polishing. tFor 15 seconds until the target was reached, the rotation of the barrel tank 12 was kept stopped (the rotational speed n was not increased), and during the 15 seconds from 15 seconds to 30 seconds, the rotational speed n was increased from 0 rpm to 300 rpm at a constant rate (constant acceleration). The changes in the orbital speed N and rotational speed n in Example 10 are shown in Figure 6. The chipping rate in Example 10 was "AA: very low".

[0053] In Example 11, the rotational speed N is obtained from the rotational stop state to the rotational speed N during polishing. t For 15 seconds until it reaches (446 rpm), the constant C of Example 1 is used. t Formula (3-4) using a constant Ca greater than (0.1334) F / n = Ca·····(3-4) The orbital rotation speed N and rotational rotation speed n are varied to satisfy the following conditions. Between 15 and 30 seconds, the orbital rotation speed N during polishing is... t The rotational speed n was increased while maintaining the same state. The changes in orbital speed N and rotational speed n in Example 11 are shown in Figure 7. The chipping rate in Example 11 was "AA: very low".

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

[0055] In Example 12, the orbital rotation speed N and rotational rotation speed n of the barrel bath 12 were accelerated and controlled in the same manner as in Conventional Example 1, and then the orbital rotation speed N during polishing was the same as in Conventional Example 1. t and the rotational speed n during polishing t Polishing was performed for 5 minutes. In Example 13, the orbital rotation speed N and rotational rotation speed n of the barrel bath 12 were accelerated and controlled in the same manner as in Conventional Example 2, and then the orbital rotation speed N during polishing was the same as in Conventional Example 2. t and the rotational speed n during polishing t Polishing was performed for 5 minutes. Example 14 was carried out in the same configuration as Conventional Example 3, with accelerated control of the orbital rotation speed N and rotational rotation speed n of the barrel bath 12, and then the same polishing orbital rotation speed N as in Conventional Example 3.t and the rotational speed n during polishing t Then, polishing was performed for 5 minutes.

[0056] In each of the 12-14 examples, the chipping rate and edge rounding amount were measured after 5 minutes of polishing, and this process was repeated 10 times. The edge rounding amount is the radius at the midpoint of the length of a 10 mm long corner edge on the outer surface of the magnetic network. The chipping rate and corner edge rounding amount shown in Table 5 are the average values ​​for 10 pieces × 10 times = 100 pieces.

[0057] [Table 5]

[0058] Examples 12 and 14 show the rotational speed n during polishing. t Although the characteristics are the same, the chipping rate in Example 12 is lower than in Example 14, and the amount of edge rounding at the corners of the workpiece, which is the amount of polishing in Example 12, is about 1.5 times greater than 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, and the thickness of the fluidized bed becomes thinner, allowing the workpiece to flow stably within the mass.

[0059] Examples 12 and 13 involve the rotational speed N during polishing. t Although the same, the chipping rate in Example 13 is lower than in Example 12. Also, the amount of edge rounding in Example 13 is less than in Example 12 and equivalent to that of Example 14. This is because the rotational speed n during polishing in Example 13 is the same. t Since the amount is less than in Example 12, in Example 13, the mass is pressed against the outer side of the inner wall of the barrel tank 12, and the rotational speed n during polishing is lower compared to Example 12. t This is thought to be because the thickness of the fluidized bed became thinner, allowing the workpiece to flow very slowly and stably within the mass.

[0060] The rotation speed control method of this embodiment 1 controls the rotation speed of the barrel tank 12 into which the workpiece is fed at a predetermined polishing rotation speed N per minute. t and the rotational speed n during polishing tIn centrifugal barrel polishing, which is performed by planetary rotation, the rotational speed of the barrel tank 12 is changed from a rotation-stopped state to the orbital rotational speed N during polishing. t and the rotational speed n during polishing t This is a method of controlling acceleration until the target is reached.

[0061] This acceleration control method includes the following acceleration control steps. In these acceleration control steps, the number of revolutions per minute during polishing N t And, the number of rotations per minute during polishing n t The constant C is based on the orbital radius R of the barrel tank 12 and the acceleration due to gravity g. t Formula (1) C t =(2πN t / 60) 2 ·R / (g·n t )·····(1) It is calculated by the following equation. Furthermore, the relative centrifugal acceleration F, based on the number of revolutions per minute N of the barrel tank 12 during acceleration control, the orbital radius R of the barrel tank 12, and the gravitational acceleration g, is calculated using equation (2). F = (2πN / 60) 2 ·R / g·····(2) It is defined by the following. Then, the number of revolutions per minute N of the barrel tank 12 during acceleration control and the number of rotations per minute n of the barrel tank 12 during acceleration control are given by equation (3) F / n≧C t ...(3) The changes are made over time to satisfy the condition.

[0062] The centrifugal force acting on the barrel tank 12 is proportional to the relative centrifugal acceleration F. When the orbital rotation speed N and rotational rotation speed n are controlled so that equation (3) is equal, the ratio of the centrifugal force (relative centrifugal acceleration F) to the rotational rotation speed n during acceleration control is equal to the rotational rotation speed n during polishing. t The ratio of centrifugal force (relative centrifugal acceleration F) to the rotational speed n is maintained at the same value. When the orbital speed N and rotational speed n are controlled such that equation (3) is an inequality, the ratio of centrifugal force (relative centrifugal acceleration F) to the rotational speed n during acceleration control is the same as the rotational speed n during polishing. tA value greater than the ratio of centrifugal force (relative centrifugal acceleration F) to the rotational speed n is maintained. According to this embodiment 1, in the acceleration control process that increases the orbital speed N and rotational speed n of the barrel tank 12, the ratio of centrifugal force to rotational speed n is greater than the rotational speed n during polishing. t The occurrence of chipping caused by a ratio smaller than that of centrifugal force is suppressed.

[0063] The acceleration control process in Examples 2, 5, 8, and 10 includes an orbit-limited acceleration process that increases the orbital rotation speed N without changing the rotational rotation speed n, starting from a state where the rotation and orbit of the barrel tank 12 are stopped. This control process makes it possible to maintain a high value for the ratio of centrifugal force (relative centrifugal acceleration F) to rotational rotation speed n from immediately after the start of acceleration control, thus having a high effect in suppressing chipping.

[0064] If the rotational axis 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 barrel tank 12's orbital path. Therefore, the flow state of the mass fluidized bed inside the barrel tank 12 also fluctuates depending on the position in the barrel tank 12's orbital path, and a state in which the mass flow becomes violent and chipping is likely to occur may occur. In view of this, in this embodiment 1, the axes of the orbital axis 13, which is the rotational axis of the barrel tank 12, and the rotational axis 16 are set in the vertical direction. If the rotational axis of the barrel tank 12 is vertical, the centrifugal force acting on the barrel tank 12 is always horizontal and is not affected by the gravitational acceleration acting in the vertical direction, so a state in which chipping is less likely to occur can be maintained.

[0065] Examples 12, 13, and 14 of the centrifugal barrel polishing method of this embodiment 1 include the acceleration control step and the constant-speed polishing step described above. The rotational speed of the barrel tank 12 during polishing is set to the polishing rotational speed N. t Defined as the rotational speed of the barrel bath 12 during polishing, the rotational speed during polishing is n t When defined as such, in the constant-speed polishing process, equation (4) -1≦n t / N t <0·····(4) Polishing rotation speed N set within the range tand the rotational speed n during polishing t The barrel tank 12 was then rotated in a planetary fashion. The orbital direction and rotational direction of the barrel tank 12 were opposite to each other, and the rotational speed during polishing was n t This is a positive value, and represents the rotational speed N during polishing. t n is a negative number. Therefore, t / N t n is a negative value. As shown in Table 5, in all of Examples 12, 13, and 14, n t / N t The value satisfies the above formula. According to the barrel polishing method of this embodiment 1, in the constant-speed polishing process in which centrifugal barrel polishing is performed by planetary rotation of the barrel tank 12 at a constant rotational speed, the occurrence of chipping of the workpiece is suppressed. Therefore, the occurrence of chipping 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 Embodiment 1 described above in the description and drawings, and the following embodiments are also included in the technical scope of the present invention. In the barrel polishing machine of Embodiment 1, the rotation axis of the barrel tank is in the vertical direction, but the axial direction of the rotation axis (orbital axis and rotational axis) of the barrel tank may be in the horizontal direction. Even when the rotation axis of the barrel tank is horizontal, the acceleration control method of this disclosure can reduce the rate of chipping compared to conventional acceleration methods. In the acceleration control steps of Experiments 1 to 4 described above, the orbital rotation speed N was increased until the relative centrifugal acceleration F reached a target value of 18G or 40G. However, the target value of the relative centrifugal acceleration F in the acceleration control step may be set to around 5G to 15G, which is the conventional centrifugal barrel polishing range. In this case as well, in the polishing step, it is preferable to set the value obtained by dividing the rotational rotation speed n by the orbital rotation speed N so that -1 ≤ n / N < 0. In the conventional examples 1 to 3 and examples 1 to 14 of Embodiment 1 described above, the workpiece and polishing stone were placed in a barrel tank and the workpiece was polished by the polishing stone. However, it is also possible to place only the workpiece in the barrel tank and use a "mutual grinding" method in which the workpieces polish each other by coming into contact with each other. In this case as well, the occurrence of chipping in the workpiece can be suppressed by the acceleration control method of this disclosure. In the deceleration process following the constant-speed polishing process, the rotational speed N during polishing is expressed in equation (2). t Substituting this into the equation gives the relative centrifugal acceleration F. t Then, equation (5) F≧F t -C t ·n·····(5) By controlling the deceleration so that the rotational speed n of the barrel tank per minute changes over time to satisfy the conditions, the occurrence of chipping during the deceleration process can be suppressed. [Explanation of Symbols]

[0067] 10…Centrifugal barrel polishing machine 12… Barrel tank 13…Axis of revolution (center of rotation axis) 16…Axis of rotation (center axis of rotation)

Claims

1. In centrifugal barrel polishing, in which workpieces are polished by rotating a barrel tank into which workpieces are fed at a predetermined orbital speed and rotational speed during polishing, a rotational speed control method is provided for accelerating the rotational speed of the barrel tank from a stopped state until it reaches the predetermined orbital speed and rotational speed during polishing, The target number of rotations per minute during polishing is N, which is the target number of rotations per minute for performing the polishing. ｔ (rpm) and n, which is the target rotational speed per minute during polishing, which is the target rotational speed to achieve for the polishing. ｔ (rpm), the orbital radius R of the barrel tank (m), and the acceleration due to gravity g (9.8 m / s²). ２ ) and the constant C based on ｔ Formula (1) C ｔ =(2πN ｔ / 60) ２ ・R / (g・n ｔ )・・・・・(1) Calculated by, The number of revolutions per minute N (rpm) of the barrel tank during acceleration control, the revolution radius R (m) of the barrel tank, and the relative centrifugal acceleration F (G) based on the gravitational acceleration g (9.8 m / s ２ ), are expressed by mathematical formula (2) F=(2πN / 60) ２ ・R / g・・・・・(2) Defined by, The orbital rotation speed N (rpm) of the barrel tank per minute during acceleration control and the rotational rotation speed n (rpm) of the barrel tank per minute during acceleration control are given by formula (3). F / n≧C ｔ ・・・・・(3) A method for controlling the rotational speed in centrifugal barrel polishing, which includes an acceleration control step that changes the rotational speed over time to satisfy the following conditions.

2. The rotational speed control method in centrifugal barrel polishing according to claim 1, wherein the acceleration control step includes an orbital-limited acceleration step of increasing the orbital rotational speed N (rpm) without changing the rotational rotational speed n (rpm) from a state in which the rotation of the barrel tank has stopped.

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

4. The method described in claim 1 or claim 2, wherein the orbital direction and rotational direction of the barrel bath are opposite to each other, and the rotational speed during polishing is n ｔ (rpm) is expressed as a positive value, and the rotational speed N during polishing is expressed as a positive value. ｔ The acceleration control process in which (rpm) is expressed as a negative value, The barrel tank is given by formula (4) -1≦n ｔ / N ｔ <0・・・・・(4) The polishing rotation speed N set within the range ｔ (rpm) and the rotational speed n during polishing. ｔ A centrifugal barrel polishing method that includes a constant-speed polishing step in which polishing is performed by planetary rotation at (rpm).

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