JP2022144898A - Centrifugal barrel polishing method - Google Patents

Abstract

To suppress variation in surface roughness of an inner peripheral surface when performing centrifugal barrel polishing of the inner peripheral surface of a hollow part for a work-piece having a shape with the hollow part.SOLUTION: According to a centrifugal barrel polishing method for polishing a work-piece 50 having a hollow part 52, in a polishing process, the work-piece 50, into the hollow part of which a polishing material is inputted, is held by a barrel case, and a rotation speed n and a revolution speed N of the barrel case are set so that a relative centrifugal acceleration F falls within a range defined by 10<F<40, and a rotational speed ratio n/N falls within a range defined by -0.9<n/N<-0.1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a technology for centrifugal barrel polishing a workpiece.

Patent Literature 1 describes a centrifugal barrel polishing method for polishing a workpiece put into a barrel case by rotating the barrel case around its rotation axis and revolving around its revolution axis.

JP 2020-069545 A

In some cases, a work having a hollow portion inside is subjected to centrifugal barrel polishing of the inner peripheral surface of the hollow portion in a state in which an abrasive is put into the hollow portion and sealed. In such a case, for example, depending on the shape of the hollow portion of the workpiece, the surface roughness of the inner peripheral surface may vary greatly.

The present invention has been made in view of the above problems, and suppresses variations in the surface roughness of the inner peripheral surface of a work having a hollow portion when the inner peripheral surface of the hollow portion is subjected to centrifugal barrel polishing. for the purpose.

In order to solve the above-mentioned problems, the present invention provides a centrifugal barrel polishing method for polishing a workpiece, comprising: a holding step of holding the workpiece, in which an abrasive is put into the hollow portion, in a barrel case; and a polishing step of polishing the workpiece held in the barrel case by revolving around the revolution axis while rotating around the axis. In the polishing process, N is the revolution speed of the barrel case, n is the rotation speed of the barrel case, the direction of revolution of the barrel case is positive, and R is the radius of revolution about the revolution axis of the barrel case. , F=4π ² ×N ² ×R/g is the relative centrifugal acceleration, which is the ratio of the gravity g to the centrifugal acceleration applied to the barrel case due to the revolution of the barrel case, 10<F<40, −0. The rotation speed n and revolution speed N of the barrel case are set so as to fall within the range defined by 9<n/N<-0.1.
The term "abrasive material" as used herein refers to a material in which an abrasive material is contained in a base material, a material composed only of a base material, or a material in which the surface of a base material is coated with an abrasive material. In addition to these, an abrasive material may be added separately as necessary.

The inventor of the present invention came to the idea that the inner peripheral surface of the hollow portion can be suitably polished if the abrasive material can be spread throughout the hollow portion of the workpiece. In general, the relationship between the rotation speed n and the revolution rotation speed N of the barrel case is such that the rotation speed n is in the opposite direction to the revolution rotation speed N and has the same absolute value. It is known that the workpiece can be suitably polished while suppressing wear of the material (that is, n/N=-1). However, even when n/N=-1, for example, if the relative centrifugal acceleration F is small (for example, less than 10), the sufficient centrifugal acceleration does not act on the abrasive, and the abrasive is pushed into the hollow of the workpiece. In some cases, the inner peripheral surface cannot be sufficiently polished due to jumping inside. In this respect, as a result of diligent research, the inventor has found that the absolute value of the rotation speed n in the barrel case is made slower than the absolute value of the revolution speed N, so that the abrasive is polished in the hollow part of the workpiece. It was found that it is possible to make it easier to If the barrel case does not rotate, the abrasive will not flow and the work cannot be polished. That is, -0.9<n/N<-0.1 is set. Further, by increasing the force applied to the abrasive due to the centrifugal force that accompanies the revolution of the barrel case, the flow of the abrasive that accompanies the rotation of the barrel case is stabilized, and the inner peripheral surface of the hollow portion can be suitably polished. In this regard, as a result of extensive research, the inventors have found that by setting the relative centrifugal acceleration F in the range of 10<F<40, the wear of the abrasive can be suppressed and the flow of the abrasive inside the hollow portion can be suppressed. was found to be stable. If the relative centrifugal acceleration F greatly exceeds 40, the polishing efficiency, which indicates the amount of wear of the abrasive against the amount of polishing of the workpiece, is significantly reduced. As a result, when centrifugal barrel polishing is performed on the inner peripheral surface of the hollow portion of the workpiece, variations in the surface roughness of the hollow portion can be suppressed.

ADVANTAGE OF THE INVENTION According to this invention, when centrifugally barrel-polishing the hollow part of a workpiece|work, the dispersion|variation in the surface roughness in a hollow part can be suppressed.

The block diagram of a polishing apparatus. The figure explaining the workpiece|work which has a hollow part. The figure explaining the movement of the polishing material in the conventional work. FIG. 4 is a diagram for explaining the movement of the abrasive within the work of the present invention; FIG. 5 is a diagram for explaining the relationship between the polishing amount, polishing efficiency, and relative centrifugal acceleration; The process drawing explaining the process of centrifugal barrel polishing.

<Embodiment>
A polishing apparatus according to this embodiment will be described with reference to the drawings. A polishing apparatus 100 shown in FIG. 1 is an apparatus capable of performing centrifugal barrel polishing on a work. The polishing apparatus 100 includes an operation panel 10 , a sequencer 11 , a revolution drive circuit 12 , a rotation drive circuit 13 and a barrel mechanism section 20 .

First, the configuration of the barrel mechanism section 20 will be described. The barrel mechanism section 20 mainly includes a sun shaft 21 , a turret disk 22 , a barrel case 23 , a revolution motor 24 and a rotation motor 25 . The sun shaft 21 is a shaft member attached rotatably in a predetermined direction, and is an example of a revolution shaft in this embodiment. The turret disk 22 is penetrated by the sun shaft 21 and held rotatably around the sun shaft 21 .

The barrel case 23 is a holding member capable of holding the workpiece 50 . The barrel case 23 has a rotation shaft 28 and is rotatably attached to the turret disk 22 via the rotation shaft 28 . Specifically, the barrel case 23 has a gripping member such as a clamp, and holds the work 50 in the polishing apparatus 100 by gripping the outer circumference of the work 50 with the gripping member. In FIG. 1, four barrel cases 23 are rotatably attached to the turret board 22 . The rotation axis 28 of the barrel case 23 is arranged eccentrically by the revolution orbit radius R from the center of the position through which the sun axis 21 penetrates in the turret disk 22 .

The revolution motor 24 is a drive source for rotating the turret disk 22 . A revolution drive pulley 26 is attached to the output shaft of the revolution motor 24 . A revolution driven pulley (not shown) connected to a revolution driving pulley 26 via a V-belt is provided on the outer circumference of the turret disk 22 . By rotating the output shaft of the revolution motor 24 , the V-belt is driven and the turret disk 22 can be rotated.

The rotation motor 25 is a drive source for rotating the barrel case 23 . A rotation drive pulley 27 is attached to the output shaft of the rotation motor 25 . The rotation of the rotation motor 25 is transmitted to the barrel case 23 via a well-known planetary gear mechanism, causing the barrel case 23 to rotate in the direction D2 opposite to the direction D1 of rotation of the turret disk 22 . For example, as a planetary gear mechanism, a sun pulley fixed to the sun shaft 21, a sun gear fixed to the sun shaft 21 and rotating together with the sun pulley, a planetary gear fixed to the output shaft of the rotation motor 25, and a sun and a reduction gear that reduces the rotation speed of the gear and transmits it to the planetary gear. A V-belt, which is a transmission member, is stretched between the rotation drive pulley 27 and the sun pulley. As a result, the sun pulley rotates according to the rotation of the output shaft of the rotation motor 25 to rotate the sun shaft 21 and the sun gear. The rotational speed of the sun gear is reduced by the reduction gear and transmitted to the planetary gear. As a result, the barrel case 23 rotates in the rotation direction D2 around the rotation shaft 28 fixed to the planetary gear.

The sequencer 11 is a programmable controller that stores a predetermined program in memory. The sequencer 11 receives signals corresponding to operating conditions of the polishing apparatus 100 from the operation panel 10 . Operating conditions that can be set by operating the operation panel 10 are, for example, the rotation speed n, the revolution speed N, the polishing time, and the acceleration/deceleration time.

The output from the sequencer 11 is input to the drive circuit 12 for revolution and the drive circuit 13 for rotation. The revolution drive circuit 12 outputs a drive signal for controlling the revolution rotation speed N of the revolution motor 24 and the polishing time according to the signal according to the operating conditions input from the sequencer 11 . In this embodiment, the revolution drive circuit 12 feedback-controls the rotation speed of the revolution motor 24 so that the rotation speed of the turret disk 22 detected by the sensor approaches the target speed. The rotation drive circuit 13 outputs a drive signal for controlling the rotation speed n of the rotation motor 25 and the polishing time according to the signal according to the operating conditions input from the sequencer 11 . In this embodiment, the rotation drive circuit 13 feedback-controls the rotation motor 25 so that the rotational speed of the barrel case 23 detected by the sensor approaches the target speed. Alternatively, the revolution driving circuit 12 and the rotation driving circuit 13 may openly control the rotational speeds of the revolution motor 24 and the rotation motor 25, respectively.

In the polishing apparatus 100 configured as described above, when centrifugal barrel polishing is performed on the inner peripheral surface of the hollow portion of the work, the hollow portion of the work is filled with an abrasive material M, and the hollow portion is sealed with a lid or plug. While being held by 23, centrifugal barrel polishing is performed. At this time, variations in the surface roughness of the hollow portion may occur in the workpiece after polishing.

FIG. 2 is a cross-sectional view of a workpiece 50 having a hollow portion as an example. The workpiece 50 has an opening 51 formed on the outer peripheral surface and a hollow portion 52 which is a space continuously extending from the opening 51 . In addition, in the work 50 shown in FIG. 2, the inside of the hollow portion 52 is partially shown, and illustration of other portions is omitted. In this embodiment, the hollow portion 52 extends inside the workpiece 50 in a bent state. In addition, the maximum size of the inner diameter of the hollow portion 52 differs from the opening 51 toward the back. Specifically, the maximum inner diameter of the hollow portion 52 decreases from the vicinity of the opening 51 toward the hollow portion 52 . In other words, when the maximum inner diameter of the hollow portion 52 near the opening 51 is L1, and the maximum inner diameters of the recessed portions are L2 and L3, respectively, L1>L2. >L3.

3 and 4 are cross-sectional views centering on a portion of the hollow portion 52 in the workpiece 50. FIG. In addition, in FIGS. 3 and 4, the illustrated abrasives M are smaller than the actual abrasives M for ease of explanation. As the barrel case 23 rotates in the D2 direction, the abrasive M in the hollow portion 52 flows along the inner peripheral surface of the hollow portion 52 and polishes the inner peripheral surface of the hollow portion 52 .

Regardless of the shape of the hollow portion 52 , if the abrasive M can be distributed to every corner of the hollow portion 52 as the barrel case 23 rotates, the abrasive M will flow on each inner peripheral surface of the hollow portion 52 . Quantity variability can be reduced. Here, in order to spread the abrasive material M to every corner of the hollow portion 52, the rotation speed n of the barrel case 23 should be slowed down. In particular, since the maximum inner diameter of the work 50 decreases as it progresses through the hollow portion 52 from the vicinity of the opening 51, if the rotation speed n is increased, the abrasive M may flow in at once and cause clogging. . In general, the relationship between the rotation speed n and the revolution rotation speed N of the barrel case 23 is such that the rotation speed n is opposite to the revolution rotation speed N and has the same absolute value (that is, n/N =-1), the apparatus structure is simple, and it is known that the workpiece 50 can be satisfactorily polished while suppressing consumption of the polishing material M to some extent. On the other hand, if the barrel case 23 does not rotate (that is, n=0), the polishing material M does not flow within the barrel case 23, and the work 50 cannot be polished.

Therefore, in the polishing apparatus 100 of the present invention, when polishing the workpiece 50, the rotation speed n and the revolution rotation speed are adjusted so that the ratio of the rotation speed N to the rotation speed n satisfies the following (Equation 1). Determine speed N. The minus sign indicates that the rotation speed n and the revolution rotation speed N are in opposite directions.
−0.9<n/N<−0.1 … (Formula 1)

In addition, if the abrasive material M is slightly moved inside the hollow part 52 while being pressed against the inner peripheral surface, the abrasive material can be slid along the inner peripheral surface and the polishing can be stabilized. It is possible to improve the polishing power for As shown in FIG. 4, centrifugal acceleration Fc due to the revolution of the barrel case 23 is applied to the workpiece 50 and the abrasive M in the barrel case 23 . The centrifugal acceleration Fc serves as a force that presses the abrasive material M inside the hollow portion 52 toward the inner peripheral surface of the hollow portion 52 . In FIG. 4, a centrifugal acceleration Fc greater than the centrifugal acceleration Fc shown in FIG.

In this embodiment, the centrifugal acceleration Fc applied to the abrasive material M due to the revolution of the barrel case 23 is determined from the viewpoint of suppressing abrasion of the abrasive material M as much as possible while maintaining a high level of abrasive force. FIG. 5 is a diagram in which the relative centrifugal acceleration F is plotted on the horizontal axis, and the polishing amount Q and the polishing efficiency E are plotted on the vertical axis. The relative centrifugal acceleration F is the ratio of the gravity g to the centrifugal acceleration Fc applied to the barrel case 23 due to the revolution of the barrel case 23, and is a value calculated by the following (Equation 2). The unit of the relative centrifugal acceleration F is dimensionless.
F=4π ² ×N ² ×R/g (Formula 2)
Note that N is the revolution speed, and the unit is [rps]. R is the orbital radius shown in FIG. 1, and the unit is [m]. g is gravitational acceleration, and the unit is [m/s ² ]. A gravitational acceleration of 9.8 [m/s ² ] may be used.

The polishing amount Q is the polishing amount of the workpiece (the weight of the workpiece removed during polishing) per unit time (for example, 30 minutes), and the unit is [mg]. The polishing efficiency E is a value defined as the ratio of the polishing amount Q of the workpiece per unit time to the wear amount W of the abrasive per unit time, and is calculated by the following (Equation 3). Note that the unit of the polishing efficiency E is dimensionless.
E=Q/W... (Formula 3)

Since the polishing efficiency E is a value obtained by dividing the polishing amount Q of the workpiece 50 by the abrasion amount W of the abrasive, it is an index showing how much the polishing of the workpiece 50 progressed when the abrasion of the abrasive M reached a predetermined amount. Become. In other words, it can also be said to be an index showing how much the abrasion of the abrasive material M is suppressed when the work 50 is polished to a predetermined amount, and it is determined by taking into consideration the progress of polishing of the workpiece and the progress of the abrasion of the abrasive material M. , is an index showing how efficiently the abrasive M contributes to the polishing of the workpiece 50 .

The polishing apparatus 100 polishes the inner peripheral surface of the work 50 by applying centrifugal acceleration Fc caused by the revolution to the polishing material M while causing the polishing material M to flow within the work 50 due to the rotation of the barrel case 23 . Therefore, there is a correlation between the relative centrifugal acceleration F, the polishing amount Q, and the polishing efficiency E. That is, it is considered that the polishing amount Q of the workpiece 50 is affected by the flow rate proportional to the rotation speed n of the barrel case 23 and the relative centrifugal acceleration F. Therefore, in the diagram shown in FIG. 5, the range of the relative centrifugal acceleration F in which the polishing amount Q and the polishing efficiency E are optimal is determined.

As shown in FIG. 5, as the relative centrifugal acceleration F increases, the polishing amount Q of the workpiece 50 increases, while the polishing efficiency E generally tends to decrease. On the other hand, the polishing efficiency E transitions in a downward convex shape with an inflection point (minimum value) at the point Eβ, and then transitions in an upward convex shape with an inflection point (maximum value) at the point Eγ. These will be described in detail by defining the ranges of the relative centrifugal acceleration F (areas a, b, c, d, and e). Note that the region a is a region showing a value smaller than the relative centrifugal acceleration F at the polishing efficiency Eα. A region b is a region from the relative centrifugal acceleration F at the polishing efficiency Eα to a value excluding the relative centrifugal acceleration F at the polishing efficiency Eβ. A region c is a region from the relative centrifugal acceleration F at the polishing efficiency Eβ to a value excluding the relative centrifugal acceleration F at the polishing efficiency Eγ. A region d is a region from the relative centrifugal acceleration F at the polishing efficiency Eγ to a value excluding the relative centrifugal acceleration F at the polishing efficiency Eδ. A region e is a region where the relative centrifugal acceleration F is greater than or equal to the polishing efficiency Eδ. Here, in the polishing efficiency E, the point Eα is a value indicating the same value as the inflection point Eγ (maximum point) of the polishing efficiency E. The point Eδ has the same value as the inflection point Eβ (minimum point) of the polishing efficiency E.

When the relative centrifugal acceleration F is within the region a, although the polishing efficiency E is higher than in the regions b, c, d, and e, the polishing amount Q is extremely small, so this region cannot be said to be a good region. In addition, when the relative centrifugal acceleration F is less than 10, the force with which the abrasive M is pressed against the inner peripheral surface of the work 50 attached to the barrel case 23 is weak, and when n/N=-1, the abrasive M is reduced. By jumping in the workpiece 50, it is not possible to press against the inner peripheral surface, which increases the possibility of surface roughness variations. On the other hand, when the relative centrifugal acceleration F is within the range of the region e, the polishing efficiency E is remarkably lowered although the polishing amount Q is high. In particular, when the relative centrifugal acceleration F greatly exceeds 40, there is a concern that the abrasive material M may cause dents on the inner peripheral surface of the workpiece 50 . At this time, if the work is made of a brittle material, there is a concern that the abrasive material M may be chipped and cracked.

Therefore, when the relative centrifugal acceleration F is a value near the regions b, c, and d (10<F<40), the polishing efficiency E maintains a high value and can be said to be a favorable region. In particular, when the relative centrifugal acceleration F is a value (15<F<35) near the regions c and d, the value of the polishing efficiency E is maintained at a particularly high value (Eβ<E<Eγ).

In this embodiment, when polishing the workpiece 50 in the polishing apparatus 100, the value of the revolution rotation speed N is determined so that the relative centrifugal acceleration F calculated by the above (formula 2) satisfies the following (formula 4). ing.
10<F<40... (Formula 4)

Further, from the viewpoint of maintaining both the polishing amount Q and the polishing efficiency E at high values, the value of the revolution rotation speed N may be determined such that the relative centrifugal acceleration F satisfies the following (Equation 5).
15<F<35... (Formula 5)

Next, the procedure of the centrifugal barrel polishing method using the polishing apparatus 100 will be described with reference to FIG.
Prior to each step shown in FIG. 6 , the operator inputs operating conditions of the polishing apparatus 100 by operating the operation panel 10 . The operating conditions include the revolution speed N, the rotation speed n, the polishing time, the movable time, and the like. These operating conditions are not limited to direct input of values by the operator operating the operation panel 10. , the sequencer 11 may read the values. In this case, the sequencer 11 may store operating conditions corresponding to work types.

In step S<b>11 (hereinafter, the step is simply referred to as S), a loading step of loading the abrasive material M into the hollow portion 52 of the workpiece 50 is performed. As the abrasive material M used in the charging step, for example, a polishing stone obtained by bonding an abrasive material with a binder that is a base material is used. As the abrasive material contained in the abrasive material M, an abrasive material having hardness higher than that of the workpiece 50 can be used. In the charging step, an abrasive having a tap density of 2 [g/cm ³ ] or more is charged into the hollow portion 52 . Here, "tap density" is the density obtained by putting the powder in a container under specified conditions, tapping the container, and dividing the powder weight by the container volume with the gaps between the powders filled. be. When a polishing stone is used as the abrasive material M, it refers to the density of the polishing stone obtained by filling the container with the polishing stone and tapping the container. When the abrasive is added separately, the tap density excluding the separately added abrasive is 2 g/cm ³ or more. Reducing the maximum size of the abrasive material M according to the inner dimension of the hollow portion 52 may reduce the abrasive power of the abrasive material M. Therefore, in the present embodiment, by using the abrasive M having a tap density of 2 [g/cm ³ ] or more, the decrease in the abrasive power due to the reduction in the dimension of the abrasive M is suppressed. As a specific method of putting the abrasive M into the work 50, the abrasive M is put into the hollow portion 52 of the work 50, and if necessary, water and compound (detergent for barrel polishing) are put in so as not to leak. Seal.

In S<b>12 , a holding step is performed in which the workpiece 50 loaded with the abrasive M is held in the polishing apparatus 100 by the barrel case 23 . Specifically, the workpiece 50 is held in the polishing apparatus 100 by gripping the outer circumference of the workpiece 50 with the gripping member of the barrel case 23 .

In S<b>13 , a polishing step of polishing the inner peripheral surface of the workpiece 50 is performed by causing the barrel case 23 to rotate and revolving due to the rotation of the turret disk 22 . Specifically, the operator operates the operation panel 10 to cause the sequencer 11 to start rotating and rotating the barrel case 23 . The sequencer 11 outputs signals according to operating conditions to the revolution drive circuit 12 and the rotation drive circuit 13 to cause the revolution drive circuit 12 to drive the revolution motor 24 and cause the rotation drive circuit 13 to rotate. The diversion motor 25 is driven.

In the polishing step executed in S13, the rotation speed n and the revolution rotation speed N output from the sequencer 11 are obtained by the above (Equation 1), ( Its value is determined so as to satisfy Expression 4). Note that the polishing step performed in S13 may be performed a plurality of times depending on the type of work.

When the operating time in the polishing process in S13 has passed, the driving of the revolution motor 24 and the rotation motor 25 is stopped, and after a predetermined period of time has passed, the process proceeds to S14 to execute the recovery process. In the collection step, the work 50 is removed from the barrel case 23, the work 50 is separated from the first abrasive M1, and the work 50 is washed and dried.

<Example>
Next, an embodiment in which the workpiece 50 is subjected to centrifugal barrel polishing according to the steps shown in FIG. 6 will be described.
In Examples, as shown in Table 1, Examples 1 to 8 with different operating conditions including relative centrifugal acceleration F and rotational speed ratio n/N were performed. In Examples 1-8, the polishing process was performed for 480 minutes. In Examples 1 to 8, as the abrasive M, a ceramic abrasive stone manufactured by Tipton was used. A ceramic abrasive stone is an abrasive material obtained by firing and bonding an abrasive material with a clay binder. The grinding stone diameter (maximum dimension) is one-third or less of the minimum inner dimension of the workpiece 50, and the tap density is 2 [g/cm ³ ] or more.

In the comparative example, the relative centrifugal acceleration F and the rotation speed ratio n/N were performed under conditions different from the above (Equation 1) and (Equation 4) for the same process as in the example.

In the example and the comparative example, the surface roughness Ra [μm] of the hollow portion 52 after the polishing process was measured. Specifically, the surface roughnesses Ra1, Ra2, and Ra3 were measured at first, second, and third measurement points at different distances from the opening 51 in the hollow portion 52 of the workpiece 50 . The first measurement point is the point closest to the opening 51 in the hollow portion 52 compared to the other measurement points, and is the point where the inner dimension is L1 in FIG. 2 . The third measurement point is the farthest (backward) point from the opening 51 in the hollow portion 52 compared to the other measurement points, and in FIG. 2 is the point where the inner dimension is L3. The second measurement point is the middle point between the first measurement point and the third measurement point in the hollow portion 52, and is the point where the inner dimension is L2 in FIG. In addition, standard deviations of surface roughnesses Ra1, Ra2, and Ra3 were calculated in each example.

Measurement results of surface roughness in Examples 1 to 8 will be described.
In any of Examples 1 to 8, the surface roughness Ra1, the surface roughness Ra2, and the surface roughness Ra3 increase in order. That is, even after centrifugal barrel polishing, the surface roughness Ra of the hollow portion 52 of the workpiece 50 increases as the distance from the opening portion 51 increases.

In Examples 4 to 8, where the relative centrifugal acceleration F is within the range of "19<F<40", the surface roughness Ra1 at the first measurement point is a value of "1.61" or less, The surface roughness Ra2 at the second measurement point was "3.77" or less, and the surface roughness Ra3 at the third measurement point was "4.86" or less. Here, the above range of "19<F<40" is a range set from the viewpoint of maintaining both the polishing amount Q and the polishing efficiency E at high values in FIG. 5 and the above (Equation 5). . In Examples 4 to 8 in which the relative centrifugal acceleration F is within the range of "19<F<40", the surface roughnesses Ra1, Ra2, and Ra3 at all measurement points are generally small compared to other examples. value. In Examples 4 to 8, the standard deviation of the surface roughness Ra was a value of "0.79" or more and "1.38" or less, and the variation was small compared to other examples. .

Furthermore, the relative centrifugal acceleration F is within the range of "19<F<40" and the rotational speed ratio "n/N" is within the range of "-0.7<n/N<-0.5" In Examples 7 and 8, the surface roughness Ra1 at the first measurement point is a value of "1.28" or less, and the surface roughness Ra2 at the second measurement point is "2.61" or less. The surface roughness Ra3 at the third measurement point was "3.22" or less. Moreover, in Examples 7 and 8, the standard deviation of the surface roughness Ra was a value of "0.79" or more and "0.81" or less. rice field.

In Examples 4 to 8, the polishing stone diameter [mm] (maximum dimension) of the polishing stone is the smallest compared to other embodiments. However, in Examples 4 to 8, since the tap density of the polishing stone was 2 [g/cm ³ ] or more, the surface roughness Ra1, Ra2, Ra3 and the standard deviation were large compared to other examples. It made no difference. In particular, in Examples 7 and 8 where the tap density is 3 [g/cm ³ ], the surface roughnesses Ra1, Ra2, Ra3 and the standard deviation are smaller than those of the other examples.

Next, the measurement results of the surface roughness of the comparative example will be described.
In both Comparative Examples 1 and 2, the surface roughness Ra1, the surface roughness Ra2, and the surface roughness Ra3 increase in order. That is, even after centrifugal barrel polishing, the surface roughness Ra in the hollow portion 52 of the workpiece 50 is not improved from the state before polishing as the distance from the opening 51 increases. In Comparative Examples 1 and 2, the standard deviations of the surface roughness Ra were "1.99" and "1.90", which were larger values than all of Examples 1-8.

The measurement results of surface roughness in Examples and Comparative Examples are summarized.
In comparison between Examples 1 to 8 and Comparative Examples 1 and 2, there was no significant difference in the surface roughness Ra1 at the first measurement point near the opening 51. FIG. This is because in the hollow portion 52, at the first measurement point, which is close to the opening 51, the polishing stone easily spreads, and the influence of the parameters (F, n/N) on the centrifugal barrel polishing is low. On the other hand, in Comparative Examples 1 and 2, the surface roughness Ra2 at the second measurement point, which is farther from the opening 51 than the first measurement point, generally has a larger value than in Examples 1-8. Further, in Comparative Examples 1 and 2, the surface roughness Ra3 at the third measurement point, which is the farthest from the opening 51, has a larger value (6.39, 6.55) than in Examples 1 to 8. rice field. Furthermore, in Comparative Examples 1 and 2, the standard deviation of the surface roughness Ra was a larger value than in Examples 1-8. This is because as the distance from the opening 51 increases, it becomes more difficult for the polishing stone to reach the inside of the hollow portion 52, and the influence of the parameters (F, n/N) on centrifugal barrel polishing increases. That is, in the polishing apparatus 100, by setting the revolution rotation speed N and the rotation rotation speed n so as to satisfy the above (Equation 1) and (Equation 4), the variation in the surface roughness of the hollow portion 52 of the workpiece 50 can be reduced. could be reduced.

In the embodiment described above, the following effects can be obtained.
In the centrifugal barrel polishing method, in the polishing step of polishing the workpiece 50 held in the barrel case 23, the relative centrifugal acceleration F is in the range of "10<F<40", and the rotational speed ratio n/N is "-0. The rotation speed n and the revolution speed N are set so as to fall within the range defined by ".9<n/N<-0.1". As a result, when the inner peripheral surface of the hollow portion 52 of the workpiece 50 is subjected to centrifugal barrel polishing, variations in surface roughness on the inner peripheral surface can be suppressed.

In the polishing process, the rotation speed n and the revolution rotation speed N are set so that the relative centrifugal acceleration F falls within the range defined by "19<F<40". As a result, variations in the surface roughness of the inner peripheral surface of the hollow portion 52 with respect to the workpiece 50 can be suitably suppressed while suppressing wear of the abrasive M.

In the polishing step, the rotation speed n and the revolution rotation speed N are set so that the rotation speed ratio n/N falls within the range specified by "-0.7<n/N<-0.5". there is As a result, variations in the surface roughness of the inner peripheral surface of the hollow portion 52 with respect to the workpiece 50 can be further suppressed.

The maximum dimension of the abrasive M is one-third or less of the minimum inner dimension of the hollow portion of the workpiece 50 . As a result, even if the hollow portion 52 does not extend linearly within the workpiece 50, the abrasive material M can be easily distributed throughout the hollow portion 52 as the barrel case 23 rotates. Variation in surface roughness of the inner peripheral surface at 52 can be suppressed.

In the holding step, an abrasive M having a tap density of 2 [g/cm ³ ] or more is put into the hollow portion 52 of the workpiece 50 . As a result, even when the size of the abrasive material M is reduced in accordance with the inner size of the hollow portion 52, it is possible to suppress a decrease in the abrasive power and, in turn, reduce the surface roughness of the inner peripheral surface of the hollow portion 52. .

<Other embodiments>
turn into stone
The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the scope of the invention. For example, the following modifications are possible.
In the above-described embodiment, the abrasive M was a ceramic abrasive stone that contained an abrasive in a ceramic binder. Instead of this, an abrasive material M in which a binding material, which is a base material, is made of a synthetic resin may be used. Further, the abrasive material M is not limited to one in which an abrasive material is contained in a binder, and may be one in which only a base material is used, or one in which an abrasive material is coated on the surface of a base material. In addition to these, an abrasive material may be added separately.

In the embodiment described above, the polishing apparatus 100 drives the revolution motor 24 and the rotation motor 25 to rotate and revolve the barrel case 23 . Alternatively, the barrel case 23 may be rotated and revolved by driving only the revolution motor 24 . In this case, the rotation of the output shaft of the revolution motor 24 should be transmitted to the sun shaft via the transmission mechanism.

DESCRIPTION OF SYMBOLS 100... Polishing apparatus, 23... Barrel case, 50... Work, 52... Hollow part, M... Abrasive material

Claims (5)

A centrifugal barrel polishing method for polishing a workpiece,
a holding step of holding the workpiece, in which the abrasive is put into the hollow portion, in the barrel case;
A polishing step of polishing the workpiece held in the barrel case by rotating the barrel case around the rotation axis and revolving around the revolution axis;
and run
Let N be the revolution speed of the barrel case,
Let n be the rotation speed of the barrel case,
The direction of revolution of the barrel case is assumed to be positive,
Let R be the radius of revolution around the axis of revolution of the barrel case,
When F=4π ² ×N ² ×R/g is the relative centrifugal acceleration, which is the ratio of the gravity g to the centrifugal acceleration applied to the barrel case due to the revolution of the barrel case,
In the polishing step,
10<F<40,
-0.9<n/N<-0.1,
A centrifugal barrel polishing method in which the rotation speed and the revolution speed of the barrel case are set so as to be within the range defined by. 2. The method according to claim 1, wherein in the polishing step, the rotation speed n and the revolution speed N of the barrel case are set so that the relative centrifugal acceleration falls within a range defined by 19<F<40. The described centrifugal barrel polishing method. In the polishing step, the rotation speed n and the revolution speed N of the barrel case are set so as to fall within a range defined by -0.7<n/N<-0.5. 2. The centrifugal barrel polishing method according to 2. The centrifugal barrel polishing method according to any one of claims 1 to 3, wherein the maximum dimension of the abrasive is one-third or less of the minimum inner dimension of the hollow portion of the workpiece. The centrifugal barrel polishing method according to any one of claims 1 to 4, wherein the abrasive charged into the hollow portion of the work in the holding step has a tap density of 2 g/cm ³ or more.

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