Rotary Dresser

Abstract

The apparatus comprises a base metal and an abrasive grain layer provided on the base metal. If the axial length of the abrasive grain 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 grain layer are designated as the first to fifth measurement positions. If the axial length of the abrasive grain 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 remaining area is designated as the measurement region. The positions obtained by equally dividing the measurement region in the axial direction are designated as the first to fifth measurement positions. At the first to fifth measurement positions, 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 grain layer is 0.10 or less.

Description

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The rotary dresser of the present 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 a single layer to the base metal by the binder. The abrasive grains are fixed randomly. 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 action 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 respect to the axial end surface of the abrasive grain layer are defined 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 defined as the measurement region. The positions obtained by equally dividing the measurement region in the axial direction are defined 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. [Brief explanation of the drawing]

[0005] [Figure 1] Figure 1 is a photograph of the rotary dresser 90 in accordance with this disclosure. [Figure 2] 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] Figure 3 is a graph showing the relationship between the height line 53 and the reference line 52 in Figure 2. [Figure 4] Figure 4 is a cross-sectional view showing the base metal 11 and abrasive layer 21 of the rotary dresser 90, as well as the binder 22 and abrasive grains 23 that constitute the abrasive layer 21. [Figure 5] 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. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address] There was a problem with the rotary dresser's shape accuracy.

[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 in this Disclosure] First, the embodiments of this 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 the embodiments of this disclosure] (Overall Structure) FIG. 1 is a photograph of a rotary dresser 90 according to the present disclosure. As shown in FIG. 1, the rotary dresser 90 has a base metal 11. The base metal 11 is provided with a hole 12. A grinding grain layer 21 is provided on the base metal 11.

[0020] The diameter D of the rotary dresser 90 varies depending on the position in the axial direction (rotation axis direction). In this example, an example where the diameter D becomes smaller at the central portion in the axial direction is shown, but the diameter D may become larger at the central portion in the axial direction. Further, the diameter D may be constant in the axial direction.

[0021] Measure the circumferential shape of the grinding grain layer 21 according to the arrows indicating the measurement positions 31 to 35. Each of the measurement positions 31 to 35 is arranged at the same position in the axial direction. That is, the measurement positions 31 to 35 are the trajectories that trace the surface of the grinding grain layer 21 in the circumferential direction at a certain position in the axial direction.

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

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

[0024] The vertical axis indicates the height of the surface of the grinding grain layer 21. The height of the position where the needle was first brought into contact is set to 0. The needle swings in the plus and minus directions from that position. The horizontal axis is the rotation angle. The rotary dresser 90 is rotated once with the needle in contact with the grinding grain layer 21. Thereby, information regarding the height of the surface of the grinding grain layer 21 from a rotation angle of 0 to 360 degrees is obtained.

[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 small rotation angles. By continuously connecting the average values ​​at each small 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.

[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, between 200 μm and 1200 μm. The average particle size is measured by destroying a portion 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 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, respectively. The ratio LA / LB of the length of the abrasive grains 23 when measured circumferentially at the same axial position 10 μm below 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 of the measurement positions 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 the end face on one end of the abrasive layer 21 and the 10% range from the end face on the other end are excluded from measurement. The remaining area (40% on one end and 40% on the other end 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 correspond to measurement positions 31 to 35.

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

[0038] Calculate LA / LB for these measurement positions 31 to 35. The arithmetic mean of all LA / LB values ​​is taken as (LA / LB)(mean).

[0039] [Table 1]

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

[0041] (Measurement method at a position 100 μm lower) Line 27 indicates a position 100 μm below 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 along line 27, and the sum S2 of the cross-sectional areas of the abrasive grains 23 within a range of at least 10 mm × 10 mm is determined. By dividing this by the field area S1 (10 mm × 10 mm), the ratio S2 / S1 of the cross-sectional areas of the abrasive grains 23 can be determined.

[0042] (Manufacturing method) In order to manufacture a rotary dresser 90 in accordance with this disclosure, it is necessary to use abrasive grains 23 with high circularity and to improve the density and dispersion of the working area of ​​the abrasive grains 23.

[0043] It is preferable that the abrasive grains 23 have distinct crystalline planes. In this case, since the working surface 24 is formed from the beginning, the working area is also more easily made uniform. In addition, a portion of the abrasive grains 23 may be ground or polished in order to form the working surface 24.

[0044] The circularity of the abrasive grains 23 is preferably 0.80 or higher. To measure the circularity, a portion of the rotary dresser 90 is destroyed and about 50 abrasive grains 23 are extracted. These are then measured using a Malvern image-based particle size distribution device (Mofologi) to determine their circularity.

[0045] Roundness = 4π (area) / (perimeter) 2 The circularity of the abrasive layer 21 of the rotary dresser 90 is determined by averaging the circularity of all abrasive layers 21 within a unit area. (Example 1)

[0046] [Table 2]

[0047] [Table 3]

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

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

[0050] The "standard deviation" is the SD value expressed by the following formula, where X1 to X5 are the circumferential lengths 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 31 to 35 in the rotary dresser 90. Note that X1 to X5 are determined by the above LA / LB.

[0051]

number

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

[0053] The "coefficient of variation" is calculated as the standard deviation / area ratio in Table 2. The "circularity of abrasive grains" is calculated by observing multiple abrasive grains within a unit area and determining the value for each grain using the formula 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 wheels, and then the workpieces were machined with those grinding wheels. Specifically, the grinding wheels were dressed with a Rotary Dresser 90. Round bar workpieces were ground with the grinding wheels. The roughness Ra and waviness Wt of the round bar workpieces 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 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 requirements for the dress were as follows:

[0059] Updressing: Peripheral speed ratio 0.02, Rotary dresser 90 diameter D1: 75mm, Rotary dresser 90 rotation speed: 200rpm, Rotary dresser 90 peripheral speed: 0.8m / s, Grinding wheel diameter: φ300mm, Grinding wheel rotation speed: 2500rpm, Grinding wheel peripheral speed: 40m / s, Cutting speed: 0.02m / s, Dress-out time: 2 seconds.

[0060] The grinding conditions were as follows: Updressing: Peripheral speed ratio 0.01, Workpiece diameter: φ40mm, Workpiece rotation speed: 200rpm, Workpiece peripheral speed: 0.4m / s, Grinding wheel diameter: φ300, Grinding wheel rotation speed: 2500rpm, Grinding wheel peripheral speed: 40m / s, Cutting speed: 0.01m / s, Spark-out: 3 seconds In sample number 1, the density of abrasive grains 23 was low, making it difficult to form a complete 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 variation in the rotary dresser 90 was large, 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 between 50% and 70%. 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. [Explanation of symbols]

[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 positions, 51 to 56 Lines, 90 Rotary dresser, 91 Rotating shaft, 92 Recess.

Claims

1. Base metal and, The base metal is provided with an abrasive layer, The abrasive layer comprises a binder and abrasive grains that are further fixed to the base metal by the binder. The abrasive grains are randomly fixed, 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, when viewed at a position 100 μm below the outermost surface of the abrasive grain layer, is 50% or more and 70% or less. The head of the abrasive grain has an action surface formed thereon. 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, 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 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. The coefficient of variation is calculated as the standard deviation / ratio of the area of ​​application. The standard deviation is the value of SD expressed by formula 1, where X1 to X5 are the ratios of the circumferential length of the abrasive grains to the circumference when viewed at a position 10 μm below the outermost surface of the abrasive grain layer at the first to fifth measurement positions in the rotary dresser. [Math 1] X is the arithmetic mean of X1 to X5, and Xi is a general term for X1 to X5. A rotary dresser in which the ratio of the area of ​​action is X.

2. The rotary dresser according to claim 1, wherein X 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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