JPH05162068A - Retraction amount adjustment method for internal grinding - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if there is a change in the sharpness of the grinding stone, the retraction amount can always be automatically adjusted to the optimum value, the unnecessary finishing grinding time can be prevented, and the cycle time can be shortened. With the goal. [Constitution] In the internal grinding process that performs rough grinding, retraction and finish grinding, the finish grinding time is measured based on the grinding wheel cutting position, and the target finish grinding time calculated from the set finishing cutting speed and the set finishing allowance. The calculated actual finishing grinding time was compared and calculated, and the retraction amount for the next work was automatically adjusted so that the difference was within the allowable range.

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 work, and in particular, an optimum amount of retraction in an inner surface grinding process that undergoes multi-step operations of rough grinding, retraction and finish grinding while measuring in-process sizing. Regarding the method of automatically adjusting to the value.

[0002]

2. Description of the Related Art In the inner surface grinding of a work such as an inner ring of a rolling bearing, which requires highly accurate roundness and cylindricity, a small amount of a grindstone is temporarily retracted after rough grinding, and then re-grinding such as finish grinding Move to. Such a retraction grinding method is effective for preventing axial tapering of the inner surface of the work and shortening the processing time, especially in the small-diameter inner surface cylindrical grinding where the grindstone shaft easily bends. The amount of retraction is determined empirically each time according to the grinding conditions such as the work size, type of grindstone, required accuracy, etc. Further, in the work inner surface grinding using the CBN grindstone, deterioration of the sharpness of the grindstone immediately after the dressing of the CBN grindstone,
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 the specified number of workpieces, the grinding is performed with a larger amount than the normal retraction amount, and then the normal retraction amount. A method of returning is also disclosed (for example, Japanese Patent Laid-Open No. 61-17385).
No. 1).

[0003]

In the retraction grinding method, the optimum retraction amount also changes depending on the change in the grinding wheel sharpness during grinding, but conventionally, the optimum retraction amount has been empirically determined. It is difficult to always maintain the optimum amount of retraction according to changes in the sharpness of the whetstone during the cycle. Usually, it tends to be unnecessarily large in view of processing accuracy, and as a result, there is a problem that the finish grinding time becomes long. Further, in the above-described method of increasing the retraction amount only for a certain period immediately after dressing or for a certain number (workpieces) in the retraction grinding with the CBN grindstone, the retraction amount is set based on previously obtained grinding data. However, even with this method, the retraction amount must be set larger than the truly necessary amount so that there is no problem in product accuracy even if there is a change in the sharpness of the grindstone due to unexpected reasons such as variations in grindstone performance. As a result, the finishing grinding time becomes long and the cycle time is wasted.
This results in a loss of productivity.

According to the present invention, the amount of retraction can be automatically adjusted so as to always be the optimum value corresponding to the sharpness of the grindstone, and thus the cycle time can be shortened while maintaining the product accuracy. It is to provide a quantity adjustment method.

[0005]

A method for adjusting a retraction amount for inner surface grinding according to the present invention uses an in-process sizing device instead of a cross slide cutting position in an inner surface grinding step of performing rough grinding, retraction and finish grinding. The finish grinding time is measured based on the grinding wheel cutting position measured by using, 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. However, the retraction amount for the next work is automatically adjusted so that the difference falls within the allowable range.

[0006]

[Operation] When finishing grinding after retraction,
The magnitude of this retraction amount affects the finish grinding time, while the sharpness of the grindstone affects the finish grinding time. In the present invention, the finish grinding time is measured based on the grinding wheel cutting position measured using the in-process sizing device instead of the cross slide cutting position, and the actual finish grinding time is the target finish grinding time calculated in advance. Since the retraction amount in the subsequent work grinding is automatically adjusted so that it falls within the predetermined range of, even if there is a change in the grinding wheel sharpness during the grinding work of multiple works, the retraction amount is the optimum value according to the grinding wheel sharpness. Therefore, the finishing grinding time becomes constant and the cycle time is not wasted.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a bending state of a grindstone shaft in the inner surface grinding of a cylindrical work 1. In the case of inner surface grinding, the mechanical rigidity of the grindstone shaft 3 is weak, and the normal-line grinding force applied to the grindstone 2 during grinding causes bending of the grindstone shaft 3 to cut the cross slide for holding and holding the grindstone spindle device. A deviation e occurs between the insertion position A and the actual grinding wheel cutting position B on the axis of the grinding wheel. As a result, the machined hole of the work 1 is tapered, and the cylindricity of the machined hole is reduced. The retraction grinding method solves such a situation. After the rough grinding, the retraction is performed to correct the deflection of the grindstone shaft 3 and then to the finish grinding to improve the cylindricity.

FIG. 2 shows the relationship between the cross slide and the grindstone cutting position with respect to different retraction amounts. FIG. 2 (a) shows a case where the retraction amount R ₁ is too large, and FIG. When the traction amount R is appropriate, FIG. 7C shows the case where the retraction amount R ₂ is 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 wheel cutting speed and the cross slide cutting speed become the same immediately after the start of finish grinding, and the deflection of the wheel shaft is constant.
Predetermined finishing allowance D detected by in-process sizing device
On the other hand, the polishing is completed in the finish grinding time T. Figure 2 (c)
When the retraction amount R ₂ is too small as described above, the grinding wheel cutting speed immediately after the start of the finish grinding becomes faster than the cross slide cutting speed, and the finish grinding time T ₂ becomes shorter for the same finishing allowance D. In this state, the cylindricity of the work hole decreases. On the contrary, when the retraction amount R ₁ is excessively large, the grinding wheel cutting speed immediately after the start of the finishing grinding becomes slower than the cross slide cutting speed as shown in FIG. 2A, and the finishing grinding required to obtain the same finishing allowance D. Time T ₁ is long,
Cycle time is wasted. As described above, the large and 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, and thereby the optimum amount of retraction corresponding to the change in the sharpness of the grindstone is secured, and the cycle time is shortened and stabilized. Is.

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

Next, the target finish grinding calculated as described above is compared with the measured actual finish grinding time, and the difference (absolute value) is calculated. If the difference is smaller than the allowable finish grinding time, the retraction amount is an appropriate value and
It is determined that the grinding state is as shown in (b), and the next work is ground with the same retraction amount. If the difference is larger than the allowable value, it is determined that the grinding is performed as shown in FIG. 2A or FIG. Adjust so that the state of (b) is achieved. The new retraction amount can be determined by adding or subtracting {(target finish grinding time)-(measured finish grinding time)} × (finish cutting speed) to the old retraction amount. If the measured finish grinding time is longer, it corresponds to Fig. 2 (a), so the old retraction amount is reduced.
When the length is short, the case 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 method, the retraction amount can always be adjusted to the optimum value even if the sharpness of the grindstone changes.
It is possible to always perform grinding in which the cross slide cutting speed and the grinding stone cutting speed are equal as shown in FIG. Therefore, the finish grinding time can be kept constant, and when the sharpness is improved because the retraction amount is set under the condition when the sharpness of the grindstone is poor, as shown in FIG. It is possible to prevent unnecessary finishing of the finishing grinding time due to a different grinding state, and it is possible to shorten the cycle time.

[0012]

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

[Brief description of drawings]

FIG. 1 is a schematic view showing a bending state of a grindstone shaft during inner surface grinding of a cylindrical work.

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

FIG. 3 is a diagram showing a control flow in in-process sizing inner surface grinding according to an embodiment of the present invention.

[Explanation of symbols]

1 Cylindrical work 2 Grindstone 3 Grindstone axis A Cross slide cutting position B Grindstone cutting position R, R ₁ , R ₂ Retraction amount T, T ₁ , T ₂ Finish grinding time D Finishing allowance

Claims (1)

[Claims] 1. A target finish calculated from a set finish cutting speed and a set finishing allowance by measuring a finish grinding time with reference to a grinding wheel cutting position in an inner surface grinding process in which rough grinding, retraction and finish grinding are performed. A method for adjusting the amount of retraction in internal grinding, which compares and calculates the grinding time and the measured actual finishing time, and automatically adjusts the amount of retraction for the next work so that the difference falls within the allowable range. ..