Rotary dresser

Abstract

A rotary dresser comprising a metallic base and an abrasive grain layer provided on the metallic base, wherein, if the axial length of the abrasive grain layer is at least 20 mm, positions at which the axial positions are 10%, 30%, 50%, 70%, and 90% with respect to an end surface in the axial direction of the abrasive grain layer are designated as first to fifth measurement positions, and, if the axial length of the abrasive grain layer is less than 20 mm, positions obtained by equally dividing, in the axial direction, a measurement region which is a remaining portion after excluding a range of 2 mm in the axial direction from both end surfaces as regions not to be measured are designated as the first to fifth measurement positions, and the coefficient of variation of the circumferential length of abrasive grains as viewed at a position 10 µｍ below the outermost surface of the abrasive grain layer is at most 0.10 at the first to fifth measurement positions.

Description

Rotary dresser

[0001] This disclosure relates to a rotary dresser. This application claims priority based on Japanese Patent Application No. 2024-221566, which is a Japanese patent application filed on December 18, 2024. All the descriptions contained in the Japanese patent application are incorporated herein by reference.

[0002] Conventionally, a rotary dresser has been disclosed, for example, in Japanese Patent Application Laid-Open No. 2012-091292 (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2012-091292

[0004] The rotary dresser of this disclosure includes a base metal and an abrasive grain layer provided on the base metal. The abrasive grain layer has a binder and abrasive grains fixed in one layer on the base metal by the binder. The abrasive grains are fixed randomly, and the ratio S2 / S1 of the sum S2 of the cross-sectional areas of the abrasive grains to the area S1 of the abrasive grain layer when viewed at a position 100 μm below the outermost surface of the abrasive grain layer is 50% or more and 70% or less. An acting surface is formed on the head of the abrasive grain. If the axial length of the abrasive grain layer is 20 mm or more, the axial positions at 10%, 30%, 50%, 70%, and 90% with reference to the axial end surface of the abrasive grain layer are taken as the first to fifth measurement positions. If the axial length of the abrasive grain layer is less than 20 mm, the range of 2 mm in the axial direction from both end surfaces is excluded from the measurement target, and the remaining part is taken as the measurement region. The positions obtained by equally dividing the measurement region in the axial direction are taken as the first to fifth measurement positions. At the first to fifth measurement positions, the coefficient of variation of the ratio of the circumferential length of the abrasive grains when viewed at a position 10 μm below the outermost surface of the abrasive grain layer at each of the first to fifth measurement positions is 0.10 or less.

[0005] Figure 1 is a photograph of a rotary dresser 90 according to this disclosure. Figure 2 is a graph showing the height of the working surface of the diamond abrasive grains on the surface of the rotary dresser 90 shown in Figure 1. Figure 3 is a graph showing the relationship between the line 53 indicating the height in Figure 2 and the reference line 52. Figure 4 is a cross-sectional view of the rotary dresser 90 showing the base metal 11, the abrasive layer 21, and the binder 22 and abrasive grains 23 constituting the abrasive layer 21. Figure 5 is a cross-sectional view of the rotary dresser 90 along the rotation axis 91 of the rotary dresser 90 used in the embodiment.

[0006] [Problems this disclosure aims to solve] There was a problem with the low shape accuracy of the rotary dresser.

[0007] An embodiment of the present invention will be described below with reference to the drawings, but the scope of the present invention is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the invention. Furthermore, if multiple upper and lower limits are given for a particular parameter, any combination of these upper and lower limits can be used to create a suitable numerical range.

[0008] [Description of Embodiments of the Disclosure] First, embodiments of the Disclosure will be listed and described.

[0009] The rotary dresser of this disclosure comprises a base plate and an abrasive layer provided on the base plate, wherein the abrasive layer has a binder and abrasive grains fixed in a single layer on the base plate by the binder, the difference between the diameter D1 of a first portion of the abrasive layer and the diameter D2 of a second portion of the abrasive layer is 3% or more of D1, the abrasive grains are fixed randomly, the ratio S2 / S1 of the sum of the cross-sectional areas of the abrasive grains to the area S1 of the abrasive layer when viewed at a position 100 μm below the outermost surface of the abrasive layer is 50% or more and 70% or less, an working surface is formed on the head of the abrasive grain, and the axial length of the abrasive layer is 2 If the length is 0 mm or more, the positions at 10%, 30%, 50%, 70%, and 90% of the axial position relative to the axial end face of the abrasive layer are designated as the first to fifth measurement positions. If the axial length of the abrasive layer is less than 20 mm, the area within 2 mm in the axial direction from both end faces is excluded from measurement, and the remainder is designated as the measurement area. The positions obtained by equally dividing the measurement area in the axial direction are designated as the first to fifth measurement positions. The coefficient of variation of the ratio of the circumferential length of the abrasive grains when viewed at a position 10 μm below the outermost surface of the abrasive layer at the first to fifth measurement positions is 0.10 or less.

[0010] Conventional rotary dressers were evaluated by measuring the proportion of the abrasive grain's working surface from a photograph of the abrasive layer's surface. However, in reality, the position of the abrasive grain's working surface varies radially, resulting in what is known as runout. Of the working surfaces, only the positive side, i.e., the surface that is radially outward, acts on the grinding wheel. Conventional methods do not take this runout into account.

[0011] Furthermore, because the abrasive layer is evaluated as a surface, the measured values ​​regarding the positional information of the working surface contain a mixture of circumferential and axial components. Therefore, it is not possible to obtain information about the undulation of the working surface in the axial direction, which is important for shape accuracy.

[0012] When measuring the working surface of a complete shape, the positional information of the surface of the complete shape is included in the positional information of the working surface, so it may not be possible to remove the positional information of the complete shape from the positional information of the working surface.

[0013] Furthermore, a process is required to remove positional information about the shape, making the measurement of the entire circumference and width extremely time-consuming.

[0014] In contrast, in this disclosure, the ratio S2 / S1 of the sum of the cross-sectional areas of the abrasive grains to the area S1 of the abrasive grain layer, measured circumferentially at the same axial position 100 μm below the outermost surface of the abrasive grain layer, is 50% to 70%, indicating a rotary dresser with high-density abrasive grain arrangement. Furthermore, because the measurement is performed circumferentially at the same axial position, the axial position is fixed, and positional information of axial waviness is not included in the measured positional information. As a result, highly accurate positional information regarding the abrasive grains can be obtained by eliminating information on axial waviness.

[0015] If the S2 / S1 ratio is less than 50%, the amount of abrasive grains decreases, shortening the lifespan of the rotary dresser. If the S2 / S1 ratio exceeds 70%, the amount of abrasive grains increases, making it difficult to improve the density of the rotary dresser and thus making the manufacturing of the rotary dresser difficult.

[0016] At the first to fifth measurement positions, the coefficient of variation of the circumferential length of the abrasive grains, as viewed at a position 10 μm below the outermost surface of the abrasive layer, is 0.10 or less. If the coefficient of variation exceeds 0.10, the shape accuracy of the grinding wheel dressed with a rotary dresser deteriorates. The coefficient of variation is calculated as standard deviation / working area.

[0017] Preferably, the average ratio of the circumferential length of the abrasive grains when viewed at a position 10 μm below the outermost surface of the abrasive grain layer at each of the first to fifth measurement positions is 5% to 30%. When a grinding wheel is dressed using a rotary dresser configured in this way, the shape accuracy of the rotary dresser and the grinding wheel dressed by it is further improved.

[0018] Preferably, the average value of the circularity of the abrasive grains is 0.80 or higher. In this case, it becomes easier to manufacture the rotary dresser of this disclosure.

[0019] [Details of Embodiments of the Disclosure] (Overall Configuration) Figure 1 is a photograph of a rotary dresser 90 according to the Disclosure. As shown in Figure 1, the rotary dresser 90 has a base plate 11. Holes 12 are provided in the base plate 11. An abrasive layer 21 is provided on the base plate 11.

[0020] The diameter D of the rotary dresser 90 changes depending on the axial position (rotation axis direction). In this example, the diameter D is shown to be smaller in the central part in the axial direction, but the diameter D may also be larger in the central part in the axial direction. Furthermore, the diameter D may be constant in the axial direction.

[0021] The circumferential shape of the abrasive layer 21 is measured according to the arrows indicating measurement positions 31 to 35. Each of the measurement positions 31 to 35 is located at the same position in the axial direction. In other words, measurement positions 31 to 35 represent the trajectory traced circumferentially across the surface of the abrasive layer 21 at a certain position in the axial direction.

[0022] Figure 2 is a graph showing the height of the working surface of the diamond abrasive grains on the surface of the rotary dresser 90 shown in Figure 1.

[0023] As shown in Figure 1, for example, at measurement position 31, if the needle of the roundness measuring machine is brought into contact with the surface of the abrasive layer 21 and the height of the surface irregularities is measured in the circumferential direction 360 degrees, a graph like the one shown in Figure 2 can be obtained. The roundness measuring machine is not limited to one that brings the needle into contact with the surface of the abrasive layer 21; a non-contact type that does not bring the needle into contact with the surface of the abrasive layer 21 may also be used.

[0024] The vertical axis represents the surface height of the abrasive layer 21. The height at the initial contact point of the needle is set to 0. From that position, the needle swings in the positive and negative directions. The horizontal axis represents the rotation angle. The rotary dresser 90 is rotated once with the needle in contact with the abrasive layer 21. This provides information on the surface height of the abrasive layer 21 for rotation angles from 0 to 360 degrees.

[0025] By performing this operation at measurement positions 31 to 35, information on the height of the abrasive layer 21 can be obtained over the entire width (axial direction) and the entire circumference (circumferential direction) of the rotary dresser 90.

[0026] Furthermore, the waviness of the surface of the abrasive layer 21 can be determined from the data of line 53 in Figure 2. The average value of the data of line 53 is calculated and plotted within a range of minute rotation angles. By continuously connecting the average values ​​at each minute rotation angle, information regarding the waviness of the surface of the abrasive layer 21, shown by line 55, can be obtained. Line 54 indicates the upper limit of the waviness, and line 56 indicates the lower limit of the waviness.

[0027] Figure 3 is a graph showing the relationship between the height line 53 and the reference line 52 in Figure 2. Figure 4 is a cross-sectional view of the base metal 11 and abrasive layer 21 of the rotary dresser 90, and the binder 22 and abrasive grains 23 that make up the abrasive layer 21.

[0028] As shown in Figure 4, in the rotary dresser 90, an abrasive layer 21 is formed on the base metal 11. Figure 4 is a cross-sectional view along the circumferential direction. Therefore, lines 25, 26, and 27 extend in the circumferential direction. The abrasive layer 21 has a plurality of abrasive grains 23 and a binder 22 that holds the plurality of abrasive grains 23. Each abrasive grain 23 has an working surface 24 formed thereon.

[0029] The binder 22 may be a metal bond, a resin bond, or a vitrified bond. From the viewpoint of firmly holding the abrasive grains 23, a metal bond is most preferred for the binder 22. Metal bonds include plating, such as nickel plating.

[0030] The abrasive grains 23 are arranged in a single layer on the surface of the abrasive grain layer 21. Preferably, the abrasive grains 23 are, for example, superabrasive grains. Superabrasive grains are diamond abrasive grains, CBN abrasive grains, or a mixture thereof. The average particle size of the abrasive grains 23 is, for example, 200 μm or more and 1200 μm or less. The average particle size is measured by destroying a part of the rotary dresser 90, taking out about 50 abrasive grains 23, and measuring them using a Malvern image-based particle size distribution device (Mofologi).

[0031] Since each working surface 24 has a different height, the height of each working surface 24 is shown in the graph in Figure 2. In Figure 2, the highest working surface 24 is located 0.021601 mm higher than the starting position of the measurement. Line 51 indicates this position. Line 51 indicates the position of the highest part of the abrasive layer 21.

[0032] In the graph shown in Figure 2, line 51 represents the height of line 25, which indicates the height of the highest working surface 24 shown in Figure 4. Line 25 is an arc shape centered on the rotation center of the rotary dresser 90. Line 25 is the outermost surface of the abrasive layer 21. Line 26 indicates a position 10 μm below line 25.

[0033] (Measurement method at a position 10 μm lower) The position 10 μm lower can be determined from the measurement of roundness. As shown in Figure 3, the position where line 53 intersects line 52 is identified on the graph. Then, the circumferential lengths of the portion where line 53 is above line 52 are denoted as L1, L2, L3, ..., Ln. The ratio LA / LB of the length of the abrasive grains 23 when measured in the circumferential direction at the same axial position at a position 10 μm lower from the outermost surface of the abrasive layer 21 is defined by the following formula.

[0034] LA / LB = L1 + L2 + L3 + ... Ln / length of line 52 LA = L1 + L2 + L3 + ... Ln LB = length of line 52 (rotation angle 360 ​​degrees) These calculations are performed at each measurement position from 31 to 35 in Figure 1.

[0035] Regarding the identification of measurement positions 31 to 35, first, if the length of the abrasive layer 21 in the direction of the rotation axis 91 (axial direction) is 20 mm or more, the abrasive layer 21 is divided into 10 equal parts in the axial direction. The 10% range from one end face and the 10% range from the other end face of the abrasive layer 21 in the axial direction is excluded from measurement. The remaining area (40% on one end side and 40% on the other end side in the axial direction from the axial center) is designated as the measurement area. Within the measurement area, measurement positions 31 to 35 are set at equal intervals along the axial direction.

[0036] In other words, if one end face of the abrasive layer 21 is considered to have an axial position of 0%, and the other end face is considered to have an axial position of 100%, then the positions at 10%, 30%, 50%, 70%, and 90% of the axial position will be the measurement positions 31 to 35.

[0037] When the axial length of the abrasive grain layer 21 is less than 20 mm, the ranges of 2 mm from the end face on one end side and 2 mm from the end face on the other end side are excluded from the measurement targets. The remaining area is defined as the measurement area. Measurement positions 31 to 35 are set at equal intervals along the axial direction in the measurement area. For example, in the case of the abrasive grain layer 21 with an axial length of 10 mm, if the end face on one end side of the abrasive grain layer 21 is defined as the axial position 0% and the end face on the other end side is defined as the axial position 100%, then the positions at the axial positions 20%, 35%, 50%, 65% and 80% become the measurement positions 31 to 35. The reason for not measuring the range of 2 mm in the axial direction from the end face is that it is difficult to improve the accuracy of the abrasive grain layer 21 in this range.

[0038] For these measurement positions 31 to 35, LA / LB is determined. The arithmetic mean of all LA / LB is defined as (LA / LB)(average).

[0039]

[0040] Table 1 shows an example of the relationship between the diameter D of the rotary dresser 90 and LA / LB at the measurement positions 31 to 35. LA / LB can be determined at the measurement positions.

[0041] (Measurement method at a position 100 μm lower) Line 27 indicates the position 100 μm lower than line 25. To determine the cross-sectional area of the abrasive grains 23 at line 27, the surface of the rotary dresser 90 is etched to cut the abrasive grains 23 at line 27, and the sum S2 of the cross-sectional areas of the abrasive grains 23 is determined within a range of at least 10 mm × 10 mm. By dividing this by the area S1 (10 mm x 10 mm) of the visual field, the ratio S2 / S1 of the cross-sectional area of the abrasive grains 23 can be determined.

[0042] (Manufacturing method) In order to manufacture the rotary dresser 90 according to the present disclosure, it is necessary to use abrasive grains 23 with high roundness to improve the density of the abrasive grains 23 and the dispersion of the working area.

[0043] It is preferable that the abrasive grains 23 have distinct crystal faces. In this case, since the working surface ingsurface 24 is formed from the beginning, it is easy to make the working area uniform. Note that a part of the abrasive grains 23 may be ground or polished to form the working surface 24.

[0044] It is preferable that the roundness of the abrasive grains 23 is 0.80 or more. To measure the roundness, a part of the rotary dresser 90 is destroyed to take out about 50 abrasive grains 23. They are measured by an image type particle size distribution apparatus Morphologi manufactured by Malvern to obtain the roundness.

[0045] Roundness = 4π (area) / (perimeter) ２ By averaging the roundness of all the abrasive grain layers 21 within the unit area, the roundness of the abrasive grain layer 21 of the rotary dresser 90 is obtained. (Example 1)

[0046]

[0047]

[0048] Rotary dressers 90 with sample numbers 1 to 16 shown in Table 2 were manufactured. In Table 2, the "abrasive grain density" indicates the ratio S2 / S1 of the sum S2 of the cross-sectional areas of the abrasive grains to the area S1 of the abrasive grain layer 21 when measured in the circumferential direction at the same axial position 100 μm below the outermost surface of the abrasive grain layer 21.

[0049] The "working area ratio" is the average value of the ratio LA / LB of the circumferential lengths of the abrasive grains at the measurement positions 31 to 35 when viewed from the position 10 μm below the outermost surface of the abrasive grain layer 21 at the measurement positions 31 to 35 of the rotary dresser 90.

[0050] The "standard deviation" is the value of SD represented by the following formula when the circumferential lengths of the abrasive grains when viewed from the position 10 μm below the outermost surface of the abrasive grain layer at the first to fifth measurement positions 31 to 35 in the rotary dresser 90 are X1 to X5. Here, X1 to X5 are obtained by LA / LB described above.

[0051]

[0052] X is the arithmetic mean value of X1 to X5. Xi is a general term for X1 to X5. X1 to X5 were measured according to the measurement method shown in FIG. 3.

[0053] The "coefficient of variation" is calculated as the standard deviation / ratio of the area of ​​application in Table 2. The "circularity of the abrasive grain" is calculated by observing multiple abrasive grains within a unit area and determining the value for each grain as 4π × (area) ÷ (perimeter). ２ This is the average value obtained by calculating the circularity using the formula.

[0054] These were used to dress the grinding wheel, and then the workpiece was machined with that grinding wheel. Specifically, the grinding wheel was dressed with a rotary dresser 90. A round bar workpiece was ground with the grinding wheel. The roughness Ra and waviness Wt of the round bar workpiece were measured using a Taylor Bobson Form Talysurf.

[0055] Figure 5 is a cross-sectional view of the rotary dresser 90 along the rotation axis 91 of the rotary dresser 90 used in the embodiment. In the rotary dresser 90, the maximum diameter D1 was 75 mm and the minimum diameter D2 was 71 mm. A recess 92 was formed in the center. The recess 92 was formed in an annular shape on the surface of the abrasive layer 21. The recess had a radius R of 4 mm. The thickness t of the abrasive layer 21 was 1.4 mm. The axial length L of the abrasive layer 21 was 20 mm.

[0056] In the direction along the rotation axis 91 of the abrasive layer 21 (axial direction), the end face of the abrasive layer 21 was located on the extension of the straight line 94. If the axial length L of the abrasive layer 21 is 20 mm or more, the positions at 10%, 30%, 50%, 70%, and 90% of the axial position, with respect to the axial end face of the abrasive layer 21, were designated as the first to fifth measurement positions 31 to 35. If the axial length L of the abrasive layer 21 is less than 20 mm, the area within 2 mm in the axial direction from both end faces was excluded from measurement, and the remainder was designated as the measurement area. The positions obtained by equally dividing the measurement area in the axial direction were designated as the first to fifth measurement positions 31 to 35. At the first to fifth measurement positions 31 to 35, the coefficient of variation of the ratio of the circumferential length of the abrasive grains 23 when viewed at a position 10 μm below the abrasive layer 21 was measured. The area outside the measurement area 36 is the non-measurement area 37 with a width W. The boundary between the measurement area 36 and the non-measurement area 37 is indicated by a line 95.

[0057] The grinding wheel was a WA grinding wheel manufactured by Krenorton. The bonding degree K was #60 (average particle size 250 μm).

[0058] The workpiece was a round bar with a diameter of 40 mm and a width of 130 mm, and the material was S45C. The dressing requirements were as follows:

[0059] Up-dressing peripheral speed ratio: 0.02, Rotary dresser 90 diameter D1: 75 mm, Rotary dresser 90 rotation speed: 200 rpm, Rotary dresser 90 peripheral speed: 0.8 m / s, Grinding wheel diameter: φ300 mm, Grinding wheel rotation speed: 2500 rpm, Grinding wheel peripheral speed: 40 m / s, Cutting speed: 0.02 m / s, Dress-out time: 2 seconds.

[0060] The grinding conditions were as follows: Up-dressing peripheral speed ratio: 0.01, workpiece diameter: φ40 mm, workpiece rotation speed: 200 rpm, workpiece peripheral speed: 0.4 m / s, grinding wheel diameter: φ300, grinding wheel rotation speed: 2500 rpm, grinding wheel peripheral speed: 40 m / s, cutting speed: 0.01 m / s, spark-out: 3 seconds. In sample number 1, the density of abrasive grains 23 was low, making it difficult to form the overall shape.

[0061] For workpiece measurement, a Taylor Bobson Form Talysurf was used. The measurement speed was 0.3 mm / s, the stylus material was diamond, the cone angle was 60 degrees, and the tip radius was 2 μm. The evaluation area was the part of the workpiece corresponding to the center of the recess 92, and the evaluation length was 4 mm. The cutoff λc was 0.8 mm. By evaluating the entire recess 92, the diameter from the D1 area to the D2 area was measured.

[0062] In sample number 12, the rotary dresser 90 showed significant variation, resulting in a deterioration of the workpiece surface roughness.

[0063] In sample number 16, the density of abrasive grains 23 was too high, making it impossible to manufacture the rotary dresser 90.

[0064] When viewed at a position 100 μm below the outermost surface of the abrasive layer, the ratio S2 / S1 of the sum of the cross-sectional areas of the abrasive grains 23 to the area S1 of the abrasive layer 21 was 50% or more and 70% or less. At the first to fifth measurement positions 31 to 35, the coefficient of variation of the ratio of the circumferential length of the abrasive grains 23 when viewed at a position 10 μm below the outermost surface of the abrasive layer 21 was 0.10 or less. Samples 2 to 11 and 13 to 15 received an evaluation of "B" or higher for waviness Wt and roughness Ra, which was a favorable result.

[0065] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope.

[0066] 11 Base metal, 12 Hole, 21 Abrasive layer, 22 Binder, 23 Abrasive grains, 24 Working surface, 25, 26, 27 Lines, 31 to 35 Measurement position, 51 to 56 Lines, 90 Rotary dresser, 91 Rotating shaft, 92 Recess.

Claims

1. The device comprises a base metal and an abrasive layer provided on the base metal, wherein the abrasive layer has a binder and abrasive grains fixed in a single layer on the base metal by the binder, the abrasive grains are fixed randomly, the ratio S2 / S1 of the sum of the cross-sectional areas of the abrasive grains to the area S1 of the abrasive layer when viewed at a position 100 μm below the outermost surface of the abrasive layer is 50% or more and 70% or less, and the heads of the abrasive grains have working surfaces. A rotary dresser in which, if the axial length of the abrasive layer is 20 mm or more, the positions at 10%, 30%, 50%, 70%, and 90% of the axial position relative to the axial end face of the abrasive layer are designated as the first to fifth measurement positions; if the axial length of the abrasive layer is less than 20 mm, the range of 2 mm in the axial direction from both end faces is excluded from measurement, the remainder is designated as the measurement area, and the positions obtained by equally dividing the measurement area in the axial direction are designated as the first to fifth measurement positions; and the coefficient of variation of the circumferential length of the abrasive grains when viewed at a position 10 μm below the outermost surface of the abrasive layer at the first to fifth measurement positions is 0.10 or less.

2. The rotary dresser according to claim 1, wherein the average ratio of the circumferential length of the abrasive grains when viewed at a position 10 μm below the outermost surface of the abrasive grain layer at each of the first to fifth measurement positions is 5% or more and 30% or less.

3. The rotary dresser according to claim 1 or 2, wherein the average value of the circularity of the abrasive grains is 0.80 or higher.

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