JP3104357B2 - Adjustment method for the amount of retraction in internal grinding - 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 grinding an inner surface of a cylindrical workpiece, and particularly to an optimal amount of retraction in an inner grinding process through a multi-step operation of rough grinding, retraction and finish grinding while measuring in-process sizing. How to automatically adjust to a value.

[0002]

2. Description of the Related Art In the inner surface grinding of a work requiring high precision roundness and cylindricity, such as the inner ring of a rolling bearing, after rough grinding, a small amount of a grinding wheel is once retracted and then re-ground, for example, finish grinding. Move to Such a retraction grinding method is effective in order to prevent the taper in the axial direction of the inner surface of the work and to shorten the processing time, particularly in a small-diameter inner cylindrical grinding in which the grinding wheel shaft is likely to bend. The amount of retraction is determined empirically each time depending on the grinding conditions such as the work size, the type of grinding wheel, and the required accuracy. In addition, in grinding the inner surface of a work using a CBN grinding wheel, the sharpness of the grinding wheel immediately after dressing of the CBN grinding wheel is deteriorated,
In order to compensate for the decrease in cylindricity due to this, during the predetermined grinding work time immediately after dressing or during the grinding of a predetermined number of workpieces, the grinding is performed by increasing the normal retraction amount, and then the normal retraction amount A method of returning to the original state has been disclosed (for example, Japanese Patent Application Laid-Open No. 61-17385).
No. 1).

[0003]

In the retraction grinding method, the optimum amount of retraction changes depending on the change in the sharpness of the grinding wheel during grinding. Conventionally, however, the optimum amount of retraction is determined empirically. It is difficult to always maintain the optimum amount of retraction according to the change in the sharpness of the grinding wheel during the cycle. Normally, it tends to be larger than necessary from the viewpoint of processing accuracy, and as a result, there is a problem that the finish grinding time becomes longer. In the above-described method of increasing the retraction amount for a certain period immediately after dressing or for a certain number (work) by retraction grinding using a CBN grinding wheel, the retraction amount is set from grinding data obtained in advance. However, even in this method, the retraction amount must be set to be larger than the truly necessary amount so that even if there is a change in the sharpness of the grinding wheel due to unexpected reasons such as variation in grinding wheel performance, there is no problem in product accuracy. As a result, the finish grinding time becomes longer and cycle time is wasted,
This has the consequence of impairing productivity.

According to the present invention, there is provided an internal grinding retraction system which can automatically adjust a retraction amount to an optimum value corresponding to the sharpness of a grinding wheel, thereby shortening a cycle time while maintaining product accuracy. It is an object of the present invention to provide a method for adjusting the amount.

[0005]

SUMMARY OF THE INVENTION A method for adjusting the amount of retraction in internal grinding according to the present invention is a method for controlling an in-process sizing device instead of a cross slide cutting position in an internal grinding step for performing rough grinding, retraction and finish grinding. The finish grinding time is measured based on the measured grinding wheel cutting position, and the target finish grinding time calculated from the set finish cutting speed and the set finishing allowance is compared with the measured actual finish grinding time. Then, the amount of retraction for the next work is automatically adjusted so that the difference falls within an allowable range.

[0006]

[Function] When finishing grinding after retraction,
The magnitude of this retraction affects the finish grinding time, while the sharpness of the grindstone affects the finish grinding time. In the present invention, the same controlled grinding end point is controlled based on the grinding wheel cutting position measured using the in-process sizing device instead of the cross slide cutting position.
Measures the finish grinding time required for grinding up to the end point of up-grinding, and automatically adjusts the retraction amount in subsequent work grinding so that this actual finish grinding time falls within the predetermined range of the target finish grinding time calculated in advance. Therefore, even if there is a change in the sharpness of the grinding wheel during grinding of multiple workpieces, the retraction amount will be the optimal value according to the sharpness of the grinding wheel,
The finish grinding time is constant and cycle time is not wasted.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a state of deflection of a grinding wheel shaft in the inner surface grinding of the cylindrical work 1. In the case of internal grinding, the mechanical rigidity of the grinding wheel shaft 3 is weak, and the grinding wheel shaft 3 bends due to the normal grinding force applied to the grinding wheel 2 during grinding. A deviation e occurs between the cutting position A and the actual grinding wheel cutting position B on the grinding wheel axis. As a result, the processing hole of the work 1 is tapered, and the cylindricity of the processing hole is reduced. The retraction grinding method solves such a situation, and improves the cylindricity by performing retraction after rough grinding to correct the deflection of the grinding wheel shaft 3 and then moving to finish grinding.

[0008] Figure 2 shows a relationship of the cross slide and the grinding wheel cutting position for different retraction value, FIG. (A) If retraction value R ₁ is excessive, drawing (b) is Li If the traction amount R is proper, FIG. (c) shows the case where the retraction amount R ₂ has become too small. In the figure, the solid line is the cross slide cutting position, and the broken line is the grindstone cutting position. When the retraction amount R is appropriate, the grinding wheel cutting speed and the cross slide cutting speed are the same immediately after the start of finish grinding, and the deflection of the grinding wheel shaft is constant.
Predetermined finishing allowance D detected by in-process sizing device
On the other hand, the grinding is completed in the finish grinding time T. FIG. 2 (c)
When the retraction amount R ₂ is too small as, grinding wheel cutting speed immediately after the finish grinding start faster than cross slide cutting speed, the finish grinding time T ₂ for the same finishing allowance D becomes shorter. In this state, the cylindricity of the work hole decreases. When retraction value R ₁ is excessive in contrast, the grinding wheel cutting speed immediately after the finish grinding start as shown in FIG. 2 (a) is slower than the cross slide cutting speed, finish grinding required to obtain the same finishing allowance D Time T ₁ is long,
Cycle time is wasted. As described above, a large or small retraction amount affects the finish grinding time. Therefore, in the present invention, the amount of retraction is automatically adjusted by measuring the finish grinding time, thereby securing the optimal amount of retraction corresponding to the change in the sharpness of the grinding wheel, and shortening and stabilizing the cycle time. It is.

FIG. 3 is a diagram showing a control flow in in-process fixed size internal grinding according to an embodiment of the present invention. Before starting the grinding, first, a rough cutting speed, a finishing cutting speed, a finishing allowance, a retraction amount, and an allowable finishing grinding time are set. In this setting, it is preferable to actually cut one work and set a value that is considered to be generally appropriate. Next, the target finish grinding time is calculated from the set finish allowance and finish cut speed by (set finish allowance) / (set finish cut speed). Thereafter, grinding is started and the time required for finish grinding is measured. In this case, the end point of the rough grinding and the end point of the finish grinding which are the basis of the measurement are managed not based on the cross slide cutting position but on the basis of the grinding wheel cutting position measured using the in-process sizing device.

Next, the target finish grinding determined as described above is compared with the measured actual finish grinding time, and the difference (absolute value) is determined. When the difference is smaller than the allowable finish grinding time, the retraction amount is an appropriate value, and FIG.
It is determined that the grinding state is as shown in (b), and the next workpiece is ground with the same retraction amount. If the difference is larger than the allowable value, it is determined that the grinding has been performed as shown in FIG. 2A or FIG. 2C. Adjust so as to be in the state of (b). The determination of the new retraction amount is obtained by adding or subtracting {(target finish grinding time) − (measured finish grinding time)} × (finish cutting speed) to the old retraction amount. If the measurement finish grinding time is longer, it corresponds to FIG. 2 (a), so the old retraction amount is reduced,
In the case where the length is shorter, this corresponds to FIG. 2C, and the old retraction is increased. The retraction amount is automatically adjusted to the value obtained by such calculation, and the next work is ground with the retraction amount.

According to the above-described method, the retraction amount can always be adjusted to the optimum value even if the sharpness of the grinding stone changes.
Grinding in which the cross slide cutting speed and the grinding wheel cutting speed as shown in FIG. 2B are always equal can be performed. Therefore, the finish grinding time can be kept constant, so that, for example, when the amount of retraction has been set under the conditions when the sharpness of the grinding stone is poor, the sharpness is improved as shown in FIG. It is possible to prevent the finish grinding time from becoming uselessly long due to the excessive grinding state, and to shorten the cycle time.

[0012]

As described above, according to the present invention, the retraction amount is always adjusted to an optimum value such that the cross-slide cutting speed and the grinding wheel cutting speed become equal even when the cutting quality of the grinding wheel changes. Therefore, the finish grinding time is kept constant, and it is not necessary to set a large retraction amount in order to cope with a change in the sharpness of the grindstone as in the related art, and the cycle time is improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a state in which a grinding wheel shaft is bent in inner surface grinding of a cylindrical work.

FIG. 2 is a diagram showing a relationship between a grinding wheel cutting position and various retraction amounts.

FIG. 3 is a diagram showing a control flow in in-process fixed-size internal grinding according to an embodiment of the present invention.

[Explanation of symbols]

1 cylindrical workpiece 2 grindstone 3 wheel spindle A cross slide cutting position B grindstone cutting position R, R _1, R ₂ retraction value T, T _1, T ₂ finish grinding time D finishing allowance

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B24B 49/00 B24B 49/10 B24B 5/06

Claims (1)

(57) [Claims] In an internal grinding step for performing rough grinding, retraction, and finish grinding, a finish grinding time is measured, and a target finish grinding time is measured and compared with the measured actual finish grinding time. A method for adjusting the amount of retraction in internal grinding, wherein the amount of retraction for the next work is automatically adjusted to fall within the range.