JP2957472B2 - Grinding wheel shape correction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting the shape of a grinding wheel, and more particularly, to a truing of a grinding wheel capable of alleviating shape deformation due to centrifugal expansion at the time of machining a workpiece in a grinding wheel used at a high peripheral speed. About technology.

[0002]

2. Description of the Related Art In a conventional cylindrical grinder or surface grinder, when the peripheral speed of a grinding wheel a exceeds 60 m / sec, there is a risk that a grinding wheel (abrasive layer) b is broken by centrifugal force due to rotation. Therefore, the peripheral speed of the grinding wheel a at the time of machining the workpiece has been set to be within approximately 60 m / sec. However, recently, even with this kind of grinding machine, there is a tendency to increase the peripheral speed of the grinding wheel a due to a demand for improvement in machining efficiency. At present, high peripheral speed grinding at a peripheral speed of 200 m / sec has been realized.

As the grinding wheel b used at such a high peripheral speed, a CBN wheel or a diamond wheel is used, and the truing of these grinding wheels b is shown in FIG. 5 (a). Using such a method, that is, using a diamond dresser (dressing device) c,
A method is used in which the dresser c is traversed in the axial direction of the grindstone surface (see the arrow in FIG. 5A) for truing. In order to minimize the wear of the diamond stone of the dresser c, the peripheral speed of the grinding wheel a during truing is usually set to 80 m / sec or less.

If the grinding wheel width (length in the axial direction of the grinding wheel a) L of the grinding wheel b is long, the diamond stone of the dresser c wears out during the truing, so that the grinding wheel at the truing start and end points. In order to prevent a difference in the corrected dimension b, the peripheral speed of the grinding wheel a is set to be lower than 80 m / sec.

[0005]

However, in a grinding machine that performs high peripheral speed grinding, if the grinding wheel a is trued at a low peripheral speed of 80 m / sec or less as described above,
When grinding wheel a is rotated at high peripheral speed during work processing,
The entire surface (grinding surface) of the grinding wheel a is bent outward and swells by the action of the centrifugal force due to the rotation (hereinafter, this state is referred to as “centrifugal expansion”). The dimensions will be different from when truing.

Incidentally, such a centrifugal expansion of the grinding wheel a means that when the grinding wheel width L of the grinding wheel a is narrow, for example, about 10 mm, the grinding wheel a hardly undergoes a shape deformation as described later. At the time of truing, the dimensional deviation due to the centrifugal expansion is eliminated by uniformly correcting the entire surface of the grinding wheel a to a constant size (the amount swelled by the centrifugal expansion) without considering the shape deformation. Was.

However, when the grinding wheel width L of the grinding wheel a becomes long, the grinding wheel shaft e of the grinding wheel d serving as a core of the grinding wheel a
When mounted on the grinding wheel d, both ends of the grinding wheel d are fixed to the grinding wheel shaft e (see FIGS. 5 (a) and 5 (b)), so that the amount of centrifugal expansion at these ends is more restricted than that at the center. Will be done. In other words, in such a case, there is a difference in the amount of centrifugal expansion between both ends and the center of the grinding wheel a.
As shown in FIG. 5 (b), the shape of the surface is distorted in the shape of a convex center with only a central portion protruding.

For this reason, in such a case, it is no longer possible to eliminate the shape deformation due to centrifugal expansion only by the dimensional correction of a uniform constant dimension in the radial direction with respect to the grinding wheel a during the truing as described above. In this state, the cylindricity of the grinding wheel a is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a grinding wheel which is deformed by centrifugal expansion when used at a high peripheral speed. An object of the present invention is to provide a truing method of a grinding wheel that can obtain accuracy.

[0010]

As a means for achieving the above object, the present invention relates to a method for correcting the shape of a grinding wheel in a grinding machine for performing a high peripheral speed grinding, wherein the truing of the grinding wheel is used for work processing. It is characterized in that a shape deformation due to centrifugal expansion of the grinding wheel at the time is predicted, and a cut correction is performed on an abrasive layer formed on the surface of the grinding wheel according to the predicted shape deformation.

In predicting the shape deformation,
The grinding wheel is centrifugally expanded, and this state is transferred to the shape transfer model, and the cut into the abrasive grain layer is corrected according to the shape transferred to the shape transfer model, or the grinding wheel is centrifuged. The shape deformation at the time of expansion is theoretically calculated, and the cut correction to the abrasive grain layer is performed based on the calculation result.

In other words, in the present invention, the truing of the grinding wheel is performed at a lower peripheral speed than that of the workpiece processing, and the deviation of the shape of the grinding wheel between the tooling and the workpiece processing (deformation due to centrifugal expansion). Pre-measurement or calculation is predicted in advance, and when truing a grinding wheel, the grinding wheel is cut in accordance with this shape loss to compensate for and eliminate the shape loss of the grinding wheel during work processing. In order to obtain a desired accuracy in processing the work.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to in-feed grinding will be described below in detail with reference to the drawings.

FIG. 1 shows a method for correcting the shape of a grinding wheel according to the present invention.
This method is shown in FIG. 3 and is a method for correcting the shape of the grinding wheel 1 in various types of grinding machines such as a cylindrical grinding machine and a surface grinding machine. More specifically, centrifugal expansion occurs in the grinding wheel 1 during work processing. This is a truing method applied to a grinding machine that performs high peripheral speed grinding.

That is, in the grinding machine that performs such high peripheral speed grinding, the surface (grinding surface 5) of the grinding wheel (abrasive layer) 2 is centrifugally expanded by the rotation of the grinding wheel 1 as described above. Although it expands outward from the initial shape, when the grinding wheel width L of the grinding wheel 1 is long, the grinding surface 5 further loses its shape due to the centrifugal expansion.

Therefore, according to the present invention, in the truing of the grinding wheel 1, as shown in FIG. 1 (a), the centrifugal expansion amount ΔR at each axial position of the grinding wheel 1 at the time of machining the workpiece (during high peripheral speed rotation). _a (see the two-dot chain line in FIG. 1 (b)) in advance, and for each axial position on the surface of the grinding wheel 2, the predicted centrifugal expansion ΔR _a
By adding the same amount of cutting correction (cutting amount ΔR _b ) as described above, the shape of the grinding wheel 1 is corrected.

In other words, at the time of truing of the grinding wheel 1, a shape deformation due to the centrifugal expansion of the grinding wheel 1 at the time of work processing is predicted, and the shape is formed on the surface of the grinding wheel 1 in accordance with the predicted shape deformation. By performing the cut correction on the abrasive layer 2, a state of ΔR _a = ΔR _b is created.

In other words, in the present invention, the shape deviation of the entire grinding wheel 1 is grasped by previously grasping the amount of centrifugal expansion ΔR _a at each position on the surface of the grinding wheel 2. In order to offset the shape of the grinding wheel 1 at the time of processing the workpiece (see FIG. 1 (b)), the grinding surface 5 at the time of processing the workpiece has a desired shape. FIG. 1B shows a state in which the grinding wheel 1 trued according to the present invention is processing a workpiece.

By the way, the centrifugal expansion of the grinding wheel 1 is such that when the grinding wheel width L of the grinding wheel 1 is narrow, for example, about 10 mm, the shape of the grinding surface 5 due to the centrifugal expansion hardly occurs. Therefore, the cutting correction to the grinding wheel 2 in this case can be dealt with only by performing uniform dimensional correction (ΔR _b = constant) in the radial direction from the end to the center of the grinding wheel 2.

On the other hand, when the grinding wheel width L of the grinding wheel 1 is wide, as shown in FIG. It cannot be dealt with simply by dimensional correction. Therefore, in such a case, in addition to the dimensional correction, a shape correction taking into account the shape deformation of the grinding surface 5 (a different centrifugal expansion amount ΔR _a at each position from the end 2a to the center 2b of the grinding wheel 2) Is necessary).

The prediction of the shape deformation due to such centrifugal expansion can be achieved by actually measuring or theoretically calculating the shape deformation. Description will be made below in order from the actual measurement.

A: Measure shape deformation due to centrifugal expansion
If a case of actually measuring such a shape collapses, 2
As shown in (a), first, an uncorrected grinding wheel 1 'in which no correction for centrifugal expansion is performed is prepared, and the grinding wheel 1' is rotated at a high peripheral speed to perform centrifugal expansion. Then, in this state, a work for shape transfer (model for shape transfer) W
a is sent to the processing position of the grinding machine to be ground, and the shape of the ground surface 5 'of the grinding wheel 2' is transferred to this shape transfer work Wa.

In truing, FIG.
As shown in (b), using the workpiece Wa on which the shape of the ground surface 5 'has been transferred as a template, the dressing device 4 connected to the copying device 3 that operates in accordance with the workpiece Wa follows the shape of the workpiece Wa. In this way, the shape of the workpiece Wa is transferred to the grinding surface 5 of the grinding wheel 2.

That is, in this case, the grinding wheel 1 'before shape correction.
Is transferred from the end 2a of the grinding wheel 2 to the central portion 2b of the grinding wheel 2 by transferring the shape of the grinding surface 5 'at the time of centrifugal expansion to the grinding surface 5 of the grinding wheel 1 performing truing as it is via the workpiece Wa for transferring the shape. It performs a cut correction according to different centrifugal expansion amount [Delta] R _a, respectively, in each position to.

In the case of actual measurement, the shape of the workpiece Wa to which the shape has been transferred as described above is measured by a shape measuring device (not shown), and the cutting amount of the dressing device is corrected using numerical control described later. It is also possible to carry out.

B: Calculate Shape Deformation Due to Centrifugal Expansion
In this case, the shape deformation of the grinding wheel 1 at the time of high peripheral speed rotation can be grasped not only by the actual measurement as described above but also by the following calculation.

In this regard, as a result of various tests conducted by the applicant on the state of shape deformation of the ground surface 5 at high peripheral speed rotation, it was found that the analysis results by the finite element method (FEM) agreed well with the actually measured values. found. Therefore, shape deformation due to centrifugal expansion of the grinding wheel 1 can be theoretically grasped by using the finite element method.

[0028] That is, the function [Delta] R _P (X of the centrifugal expansion amount [Delta] R _P at an arbitrary point P on the surface of the grinding wheel 2 and the distance X from the end 2a of the grinding wheel 2, a circumferential speed V of the grinding wheel 1, V)
And then, on the basis of this function is to calculate the depth of cut [Delta] R _b dressing device 4 at the time of truing (see Figure 3 (a)). In this case, the function ΔR
_P (X, V) is allowed to store the numerical control device (not shown), it is configured to instruct the cutting amount [Delta] R _b with respect to the dressing apparatus 4 by the numerical controller.

The function ΔR _P (X, V) is specifically obtained as follows.

That is, as shown in FIG. 3 (b), the amount of centrifugal expansion ΔR ₀ in the central portion 2b of the grinding wheel 2 is
Since it is known that the depth is proportional to the square of the peripheral speed V, the depth of cut at this position (central portion) 2b is first calculated (determination of the dimension correction amount).

[0031] Then, the relationship between the centrifugal expansion amount [Delta] R _P in P centrifugal expansion amount [Delta] R ₀ and any other point in the central portion 2b, the shape of the grinding surface 5 during centrifugal expansion by the dotted line shown in FIG. 3 (b) By drawing a substantially arc as shown, it is possible to capture this as a quadratic function. Therefore, the position of the point P in this case is expressed as follows in relation to the central portion 2b.

[0032] That is, as shown in FIG. 3 (b), the difference between the centrifugal expansion amount [Delta] R ₀ of the centrifugal expansion amount [Delta] R _P and the central portion 2b of the arbitrary point P and [Delta] R, relative to the central portion 2b (x
If = 0) the distance on the horizontal axis of the central portion 2b and the point P is x ^{_{as, ΔR = a (V 2 2}} -V 1 2) x 2 ... formula (wherein, a is the coefficient, V ₁ is Peripheral speed during truing, V
₂ indicates the peripheral speed at the time of processing the workpiece. Also, the coefficient a
Is calculated from the analysis result of the centrifugal expansion amount by the finite element method or the actual centrifugal expansion amount. ) (Determination of the shape correction amount).

However, the coefficient a in the above equation differs depending on the dimensions (eg, width, inner diameter, outer diameter) and material of the grinding wheel (grinding wheel) 1. Therefore, if any of these is changed, the coefficient a is also renewed. You need to recalculate.

Thus, by grasping the shape correction amount ΔR with respect to the dimension correction amount (ΔR ₀ ) as a quadratic function (the above equation), the shape correction amount ΔR at each position of the ground surface 5 is calculated. And this is calculated as the dimension correction amount Δ
Do it subtracted from R _0, can be obtained depth of cut [Delta] R _b dressing device 4 in each position of the grinding surface 5. Therefore, this calculation is performed by the numerical control device, and the cut amount Δ
By controlling R _b , it is possible to realize the cutting correction to the grinding wheel 1.

The method for correcting the shape of a grinding wheel according to the present invention can be appropriately designed without being limited to the above embodiment.

For example, as shown in FIG. 4, the present invention is applicable to a case where the workpiece W is a stepped workpiece. In this case, a stepped grindstone is also used as the grinding wheel 2 because the workpiece W has a different diameter portion, but even in such a case, the grinding wheel 2 has a desired cylindricity when grinding the outer peripheral surface of the work W. Therefore, by applying the present invention to each of the different diameter portions of the grinding wheel 2, highly accurate processing can be realized.

In each of the above embodiments, the case of in-feed grinding is taken as an example, but the present invention is not limited to this and can be applied to through grinding. However, in that case, it is unnecessary to use the copying apparatus 3 as described above, and it is sufficient to calculate the centrifugal expansion amount by the calculation based on the finite element method described above.

[0038]

As described above in detail, according to the present invention, when truing a grinding wheel, a shape deformation due to centrifugal expansion of the grinding wheel at the time of work processing is predicted, and the grinding wheel is adjusted in accordance with the predicted shape deformation. Since the cutting depth is corrected for the abrasive layer formed on the surface of the wheel, even if the grinding wheel is trued at a lower peripheral speed than during workpiece processing, the shape is lost due to centrifugal expansion of the wheel during workpiece processing. The adverse effect on the processing accuracy due to this can be suppressed to a very small extent. As a result, a highly accurate and stable grinding process can be realized even when a grinding wheel having a long grinding wheel width is used.

Since truing of the grinding wheel at a low peripheral speed does not adversely affect the machining accuracy, truing at a low peripheral speed is possible in a grinding wheel having a long grinding wheel width, and the diamond stone of the dresser is worn. Can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method of correcting the shape of a grinding wheel according to the present invention. FIG. 1 (a) shows the state of a grinding wheel in which the amount of centrifugal expansion of a grinding wheel is predicted and the surface is subjected to a cutting correction. FIG. 1B shows a state in which the grinding wheel is used at a high peripheral speed.

FIG. 2 shows a case in which the method for correcting the shape of a grinding wheel according to the present invention is carried out using a copying apparatus, and FIG. 2 (a) is an explanatory view showing a step of creating a template of the copying apparatus;
(b) is an explanatory view showing a state in which cutting correction is applied to the grinding wheel using the copying apparatus.

FIG. 3 (a) is an explanatory diagram for explaining a function when a centrifugal expansion amount is predicted by calculation in the grinding wheel shape correcting method according to the present invention, and FIG. 3 (b) is the same. FIG. 9 is an explanatory diagram for specifically explaining how to derive a function.

FIG. 4 is an explanatory view showing an example in which the present invention is applied to a stepped workpiece.

FIG. 5 (a) is an explanatory view showing a conventional truing method of a grinding wheel, and FIG. 5 (b) is an explanatory view showing a state of centrifugal expansion of a grinding wheel trued by this method during work processing. It is.

[Explanation of symbols]

Reference Signs List 1 grinding wheel 1 'grinding wheel before shape correction 2 grinding wheel 2a end of grinding wheel 2b center of grinding wheel 3 copying device 4 dressing device 5 grinding surface ΔR _a centrifugal expansion amount of grinding wheel ΔR _b cut into grinding wheel Correction amount L Wheel width W Work Wa Work for shape transfer (model for shape transfer)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B24B 53/00 B24B 53/08 B24D 5/02

Claims (3)

(57) [Claims] 1. A method for correcting the shape of a grinding wheel in a grinding machine that performs high peripheral speed grinding, wherein the truing of the grinding wheel is predicted by predicting a shape deformation due to centrifugal expansion of the grinding wheel during work processing. A method of correcting the shape of a grinding wheel, comprising performing a cutting correction on an abrasive layer formed on the surface of the grinding wheel according to the deformed shape. 2. In predicting the shape deformation, a grinding wheel is centrifugally expanded, and this state is transferred to a shape transfer model, and the cut correction to the abrasive layer is transferred to the shape transfer model. The method for correcting the shape of a grinding wheel according to claim 1, wherein the method is performed according to the following. 3. The method according to claim 1, wherein in predicting the shape deformation, the shape deformation during centrifugal expansion of the grinding wheel is theoretically calculated, and the cut in the abrasive layer is corrected based on the calculation result. How to correct the shape of the grinding wheel.