JPH10557A - Abrasive grain projection evaluation method for grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately understand abrasive grain projection states by evaluating the abrasive grain projection states based on a relative load curve expressed by the projecting relative depth, which is expressed by the ratio of the absolute depth from an abrasive grain foremost part of a measured section curve to the wheel surface to a mean abrasive grain size. SOLUTION: A sectional curve 5 formed from abrasive grain 2 and binder 3 is measured to find a first relative load curve. Secondly, the absolute depth is found by multiplying the relative depth of the ordinate axis of the first relative load curve by the maximum height obtained from the sectional curve 5. In a second relative load curve, the ordinate axis and the abscissa axis are expressed by an projection relative depth (expressed by %) and a relative load length (expressed by %) respectively. The projection relative depth is a value, which is expressed by a percentage, obtained by dividing the absolute depth by the mean abrasive size of a grinding wheel. One of evaluation indexes for the abrasive grain projection states is the sectional depth equivalent to the maximum increase of the relative load length.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for evaluating protrusion of abrasive grains of a grinding wheel such as a diamond wheel. The abrasive protrusion evaluation method of the grinding wheel of the present invention,
It is used for determination of dressing or truing time of the grinding wheel, determination of dressing amount or truing amount, analysis of grinding action, and the like.

[0002]

2. Description of the Related Art The processing efficiency, grinding resistance, grinding accuracy, and the like of a grinding wheel greatly depend on the state of abrasive grains protruding from the grinding wheel. Many abrasive grains protrude at random from the surface of the grinding wheel. Therefore, in analyzing the grinding action of the grinding wheel, it is necessary to evaluate the state of abrasive grain protrusion using a quantity (amount of abrasive grain protrusion) that is directly related to the grinding action and is representative of the state of projection of many abrasive grains. .

For example, if a grinding wheel is used for a certain period of time, the grinding ability is reduced due to wear of abrasive grains, or the shape accuracy is deteriorated due to uneven wear of the grinding surface. Deterioration of work accuracy due to deterioration of shape accuracy,
Grinding of brittle materials such as silicon wafers and fine ceramics causes the generation or increase of residual strain and cracks. Therefore, it is necessary to make the dressing tool or the truing tool protrude the abrasive grains serving as the cutting blade or correct the shape of the tip at an appropriate time. For this purpose, it is preferable to measure the protrusion amount of the abrasive grains of the grinding wheel, obtain the relationship between the protrusion amount of the abrasive particles, the grinding resistance, and the processing accuracy, and determine the timing of dressing or the like based on the result.

As one of the methods for measuring the amount of protrusion of abrasive grains, there is a method of measuring with a surface roughness meter. JP-A-5-30283
No. 0 discloses a "method for measuring the amount of protruding abrasive grains of a superabrasive grain", which measures the center line average roughness and the center line peak height of the superabrasive grain surface with a stylus type surface roughness meter, Calculate the average value of the data of the line average roughness and the average value of the data of the center line peak height, and calculate the sum of the average value of the center line average roughness data and the average value of the center line peak height data. It is characterized in that it is obtained as an abrasive protrusion amount. According to this method, an accurate value of the amount of protrusion of the grindstone of the superabrasive grindstone can be obtained in a much shorter time than the conventional method.

[0005]

In the conventional method for measuring the amount of protrusion of abrasive grains, the amount of protrusion of abrasive grains is measured from the sum of the average value of the center line average roughness and the average value of the center line peak height. In the process of calculating the center line average roughness, as is clear from the definition, even a portion that is a space portion (tip pocket) is included. The abrasive grain protrusion indicates the height at which the abrasive grains protrude from the bond material.Including the chip pocket, which is the space between the abrasive grains, gives a physically wrong value. Become. Therefore, there is no reasonable correlation between the sum of the average value of the center line average roughness and the average value of the center line peak heights and the amount of protrusion of the abrasive grains even if both are approximate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for evaluating the abrasive grain protrusion of a grinding wheel, which can accurately know the abrasive grain protrusion state of the grinding wheel.

[0007]

According to the present invention, there is provided a method for evaluating the protrusion of abrasive grains of a grinding wheel, comprising the steps of: The state of abrasive grain protrusion is evaluated based on a relative load curve expressed using the relative depth of protrusion, which represents the absolute depth from to the wheel surface as a ratio to the average abrasive grain size.

[0008] In the above method for evaluating abrasive protrusion of the grinding wheel, the relative depth of the protrusion corresponding to the maximum increment of the relative load length indicated by the relative load curve, the reference relative load set in advance, is used as an evaluation index of the abrasive protrusion state. The relative protrusion length corresponding to the length, the relative load length corresponding to the preset reference relative protrusion depth, or the cross-sectional area ratio occupied by the chip pocket can be used.

According to the present invention, the state in which the abrasive grains are projected is evaluated using a relative load curve composed of the projected depth and the relative depth. Therefore, the evaluation does not include a chip pocket, and only considers a portion where the abrasive grains are projected from the binder. Therefore, it is possible to accurately know the abrasive grain protrusion state of the grinding wheel.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a required relative load curve is obtained as follows. First, a cross-sectional curve of the grinding action surface of the grinding wheel is measured over a predetermined measurement length, and a first relative load curve is determined from the measured cross-sectional curve. Next, based on the first relative load curve, a second relative load curve in which the vertical axis protrudes and is set as a relative depth is obtained.

A method for obtaining the second relative load curve will be described below. FIG. 1 is a cross-sectional view schematically showing an enlarged part of the grinding wheel 1. In order to determine the first relative load curve, a cross-sectional curve 5 formed by the abrasive grains 2 and the binder 3 is measured by a surface roughness meter. As a method for measuring the cross-sectional curve, a stylus method, a light wave interferometry, or a light cutting method is used. As the measurement length, an appropriate value is selected from the standard values of JIS and a measuring device together with the abrasive particle diameter of the grinding wheel to be measured. From the measured cross-sectional curve 5, the first relative load length t _j is obtained by the following equation.

(Equation 1) In the above equation, j is a relative depth when the sectional curve 5 is divided in the height direction. The relative depth indicates the depth for each division when the maximum height Rmax is divided by a predetermined number in the height direction, as a percentage of the maximum height. The number of divisions in the height direction is, for example, 10 or 2
0. b _ij is the length of the substantial portion of the profile curve 5 is cut when cut in cutting height j, n is the number of points, taken in cutting height j, l _m is the measurement length. The first relative load curve is obtained by plotting the relative depth on the vertical axis and the relative load length on the horizontal axis, and is expressed in percentage. FIG. 2 shows an example of a first relative load curve obtained by measuring a grinding wheel after truing and dressing.

Next, the absolute depth is obtained by multiplying the relative depth on the vertical axis of the first relative load curve by the maximum height Rmax obtained from the original sectional curve 5. With this absolute depth as the vertical axis,
Redraw the first relative load curve. For example, when such processing is performed on FIG. 2, the result is as shown in FIG. Thus, the absolute depth is expressed in units of length, for example, μm.

In the second relative load curve, the vertical axis protrudes and the relative depth (expressed in%), and the horizontal axis represents the relative load length (expressed in%). The protruding relative depth is the absolute depth shown in FIG.
The value obtained by dividing by the average abrasive particle diameter d of the grinding wheel is expressed as a percentage. Since the average grain size is known for a commercially available grinding wheel, the average grain size d can be determined by converting the grain size into a grain size. For example, the average abrasive grain size of No. 140 is about 104 μm.

One of the evaluation indexes of the abrasive grain protrusion state is the sectional depth corresponding to the maximum increment of the relative load length indicated by the second relative load curve as described above. The cross-sectional depth corresponding to the maximum increment can be determined computationally or graphically from surface roughness measurements. In the latter case, the position of the maximum gradient is directly obtained from the relative load curve, or a gradient diagram with respect to the relative depth is drawn from the relative load curve as shown in FIG.
Find the relative depth corresponding to the maximum value of the gradient. When the measurement is performed at a plurality of points on the grinding action surface, the average value of the evaluation index is obtained for the plurality of points, and the state of the abrasive grain protrusion can be evaluated based on the average value.

Another one of the evaluation indices of the state of protruding abrasive grains is as follows:
This is a cross-sectional depth corresponding to a preset reference relative load length. The obtained section depth may be compared with a preset reference section depth. The relative load length at this time is desirably, for example, 50%, that is, the ratio of the portion occupied by the abrasive grains and the bond to the portion occupied by the chip pocket is halved, but is set depending on the concentration of the abrasive grains and the specifications of the bond. You may change the value.

Still another evaluation index of the abrasive grain protrusion state is a relative load length corresponding to a predetermined reference protrusion relative depth. Reference section depth, for example, 20%
The relative load length with respect to is determined to evaluate the state of abrasive grain protrusion. Generally, it is desirable that the abrasive grains protrude 30 to 40% of the abrasive particle diameter. If the content is more than 50%, the bond cannot hold the abrasive grains and drops. Therefore, the value of the reference section depth is, for example, 20% of the abrasive grain size,
By determining the ratio of the relative load length to this, it can be determined whether or not a sufficient chip pocket is secured in the cross section.

For example, in the example of FIG.
Look at the 0% part. In the case after truing, the relative load length is almost 100%, and it can be seen that most of the measured length is occupied by the abrasive grains or the bond material, and there is almost no chip pocket. This is in good agreement with the fact that truing alone has no grinding performance on the grinding wheel.

Next, after truing and further dressing, the relative load length is approximately 30%.
It can be expected that a sufficient chip pocket is secured on the surface of the grinding wheel, and that the abrasive grains serving as cutting edges are sufficiently protruding. This is in good agreement with the fact that after dressing the grinding wheel exhibits very good grinding performance.

Still another evaluation index of the state of protruding abrasive grains is a sectional area ratio occupied by a chip pocket. The cross-sectional area ratio occupied by the chip pocket is the ratio of the area of the upper right part of each curve shown in FIG. 4 to the entire graph. In this case, the area of the entire graph is the total area when the relative depth of the protrusion is set to 0% to 100%. In the graph of FIG. 4, the protrusion relative depth is displayed only from 0% to 50%. This is because the region of 50% or more is generally a region where the abrasive grains fall off from the bond material, and is generally in a state where it hardly occurs. However, it is more reasonable in the physical sense to calculate the cross-sectional area ratio occupied by the chip pockets and to make the relative depth up to 100%. The protruding state of the abrasive grains may be determined by comparing the cross-sectional area ratio of the chip pocket thus obtained with a preset reference cross-sectional area ratio. This reference cross-sectional ratio is a value obtained from the ideal state by calculation, or an empirically preferable value,
This may be adopted.

[0020]

[Example] Grinding wheel (mesh size: No. 140,
(Average abrasive particle size: 104.0 μm, binder: resin bond)
Was subjected to truing using a cup-type rotary truer, and finished to a roundness of 3 μm or less. With respect to the truing grinding wheel, the amount of abrasive protrusion was measured. Then, GC
The grinding wheel was dressed with a 220H stick type dresser, and the amount of the abrasive grains projected in the dressed state was measured. The measuring device is a stylus type surface roughness meter. The surface roughness meter used has a function of outputting a maximum height Rmax as a standard, a first relative load curve, and a relative load length for each relative depth. The division in the height direction is 10
It is equally divided and the relative depth is output every 10%. The measurement results are shown in Tables 1 and 2 and FIGS.

In Table 1, the relative depth and the relative load length after truing and after dressing are output results provided as standard on a surface roughness meter. In the present invention, it is necessary to first determine the absolute depth in order to determine the second relative load curve. The absolute depth is obtained by multiplying the relative depth by the maximum height Rmax after truing and after dressing. Next, this absolute depth is divided by the average abrasive grain size and converted into a percentage to determine the relative protrusion depth. The second relative load curve as shown in FIG. 4 can be obtained by taking the protrusion relative depth thus obtained on the vertical axis and the relative load length on the horizontal axis.

In addition, in Table 1, in order to obtain the cross-sectional area ratio occupied by the chip pockets, the area ratios of the chip pockets are approximately calculated for each section of the relative depth and are also shown. The sum of the chip pocket area ratios is the cross-sectional area ratio occupied by the chip pockets. Here, the chip pocket area ratio for each section of each relative depth is approximately calculated as follows, for example.

That is, the ratio of the chip pocket area to the relative depth of 20% is 3.4% of the relative load length and the protrusion relative depth of 1.98% to the relative depth of 10%, and the relative depth to the relative depth of 20%. Using 11.3% of the depth and 3.96% of the projected relative depth, it is calculated by the following equation. Chip pocket area ratio% = [｛(100% -3.4%)
× (100% -11.3%)｝ × (3.96% -1.9)
8%)] / (2 × 100%) Here, 100% of the denominator is used to normalize the numerator to the cross-sectional area ratio because the numerator is a multiplication of percentages. The sum of the chip pocket area ratios obtained in this way is taken as the sectional area ratio occupied by the chip pockets with respect to the entire graph. This value is 7.69% and 23.6 after truing and after dressing, respectively.
4%.

Table 2 is for evaluating the state of abrasive grain protrusion by the relative protrusion depth corresponding to the maximum increment of the relative load length. Here, for example, the relative depth is 10% and 2%.
Relative load length increments between 0% are expressed as intermediate values of relative depth, ie, values for 15% relative depth. For the relative depths of 0% and 100%, the relative load length increment was set to 0% because the values are both ends. The relative depth of protrusion in the table is a value with respect to an intermediate value of the relative depth. That is, for example, the protrusion relative depth with respect to the relative depth of 15% is an intermediate value of the protrusion relative depths with respect to the relative depths of 10% and 20%.

[0025]

[Table 1]

[0026]

[Table 2]

FIG. 2 is a first relative load curve, in which the relationship between the relative depth and the relative load length shown in Table 1 is graphed. FIG. 3 is a relative load curve using an absolute depth (relative load length × Rmax) instead of the relative depth used in FIG. FIG. 4 is a second relative load curve using the projected relative depth instead of the relative depth used in FIG. The vertical axis in FIG. 4 is obtained by dividing the absolute depth in FIG. The vertical axis in FIG. 5 is the relative depth of protrusion in Table 2, and the horizontal axis is the relative load length increment relative thereto.

From Table 2 and FIG. 5, it can be seen that the overhang relative depth corresponding to the maximum increment in relative load length is about 7% after truing and about 26% after dressing. That is, it is understood that the protrusion of the abrasive grains is sufficiently ensured by the dressing. In addition, the relative load length 50
From FIG. 4, it can be seen that the protrusion relative depth corresponding to% is about 7% after truing and about 24% after dressing.

As is apparent from Table 1, the cross-sectional area ratio occupied by the tip pocket is about 8% after truing and about 24% after dressing. Therefore, the cross-sectional area ratios of the abrasive grains are about 93% and 76%, respectively, and it can be seen that the protrusion of the abrasive grains is sufficiently ensured by the dressing.

[0030]

According to the present invention, since the protrusion of the abrasive grains of the grinding wheel is evaluated using the relative load curve, it is possible to know the state of the abrasive grains of the grinding wheel accurately.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view schematically showing a part of a grinding wheel.

FIG. 2 is an example of a first relative load curve.

FIG. 3 is an example of a relative load curve using an absolute depth instead of a relative depth.

FIG. 4 is an example of a second relative load curve using a protruding relative depth instead of a relative depth.

FIG. 5 is a diagram illustrating an example of a relationship between a relative protrusion depth and a relative load length increment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Grinding wheel 2 Abrasive grain 3 Binder 5 Cross section curve 7 Tip pocket

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noriyuki Marutani 239 Shimohirama, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Inside (72) Inventor Etsuko Shimada 239 Shimohirama, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Kuroda Seiko Co., Ltd. Inside

Claims (5)

[Claims] 1. A method for evaluating the state of protrusion of abrasive grains using the surface roughness of a grinding wheel, wherein the absolute depth of the measured cross-sectional curve from the tip of the abrasive grains to the wheel surface is determined with respect to the average abrasive grain diameter. A method for evaluating abrasive grain protrusion of a grinding wheel, which evaluates the state of abrasive grain protrusion based on a relative load curve expressed using a relative protrusion depth expressed as a ratio. 2. The method of claim 1, wherein in the relative load curve, the relative depth of the protrusion corresponding to the maximum increment of the relative load length is used as an evaluation index of the state of the protrusion of the abrasive grain. 3. The method according to claim 1, wherein, in the relative load curve, a relative protrusion depth corresponding to a preset reference relative load length is used as an evaluation index of a state of abrasive grain protrusion. 4. The method according to claim 1, wherein, in the relative load curve, a relative load length corresponding to a preset reference relative depth is used as an evaluation index of the abrasive grain projection state. 5. The method for evaluating abrasive protrusion of a grinding wheel according to claim 1, wherein in the relative load curve, a cross-sectional area ratio occupied by a chip pocket is used as an evaluation index of an abrasive protrusion state.