JPH07266224A - Grinder - Google Patents

Abstract

PURPOSE:To improve the circularity of the surface to be ground in spite of a short machining time, and to restrict the lowering of dimension accuracy at minimum in a grinder. CONSTITUTION:A control means 130 operates a driving means 100 so as to perform the pre-stage grinding of the surface Wa to be ground of a work W and the finish grinding to be followed the pre-stage grinding with a grinding wheel 19, and concludes the finish grinding when the outer diameter of the surface to be ground, which is measured by a measuring means 120, achieves the finish target diameter A computing means 90 computes the distance corresponding to the deflection of the work W due to the grinding resistance at the the of concluding the finish polishing. Furthermore, the control means 130 performs the grinding with a grinding wheel during the one turn of the work W, which is continued to the conclusion of the finish polishing, and also moves a grinding wheel stock and a work at a distance corresponding to the computed deflection of the work in the direction for separating from each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding device for grinding a cylindrical outer diameter of a workpiece.

[0002]

2. Description of the Related Art In a grinding machine such as a cylindrical grinder, as shown in FIG. 8, centers 15a, 16 of a headstock and a tailstock are used.
A grindstone base provided with a grindstone wheel 19 that rotates with respect to the workpiece W supported by a is fed to grind the outer diameter of the surface Wa to be ground. As shown by the solid line G in the diagram of FIG. 9, the grindstone is moved in order from the rough grinding G1, the fine grinding G2, and the fine grinding G3 while decreasing the feed speed in order to reduce the surface of the workpiece W to be ground.
If the outer diameter of Wa is represented by a value converted to the position of the wheel head, for example, it decreases as indicated by the broken line H. With this kind of grinding machine,
The work piece is bent due to the grinding resistance required for grinding,
The positions of the solid line G and the broken line H at a certain moment differ by the amount of this bending.

Therefore, in this type of cylindrical grinding, the processing is performed while measuring the outer diameter of the surface to be ground during grinding using an in-process measuring device in order to obtain high accuracy.
When the outer diameter of the surface to be ground Wa reaches the rough grinding completed diameter, the feed speed is switched from the rough grinding feed to the fine grinding feed, and when it reaches the fine grinding completed diameter, it is switched from the fine grinding feed to the fine grinding feed to reach the finishing target diameter D. If it reaches, the grinding process is completed, and as shown by the solid line G4, the whetstone head is immediately retreated backward. Alternatively, after the fine grinding is finished, the grindstone head is stopped for a predetermined time as shown by the two-dot chain line G5 to perform spark-out, and then the grindstone head is retracted rapidly as shown by the two-dot chain line G6.

[0004]

When the grindstone head is fast-forwarded and retracted immediately after fine grinding, the shape of the grinding surface Wa is as shown in FIG.
Since it becomes a part of the spiral surface exaggerated as shown in Fig. 4, it is necessary to set the fine grinding feed rate to a predetermined small value or less in order to maintain the circularity of the surface to be ground Wa at a predetermined value. Therefore, there is a problem that the processing time increases. If the spark-out is performed, the roundness can be increased even if the fine grinding speed is increased, but the spark-out for this purpose requires the workpiece W to be rotated several revolutions or more. The diameter of the surface Wa decreases due to the springback of the bending of the workpiece W as shown by the alternate long and short dash line H5 in FIG. 9, and this decrease amount becomes e at the end of the sparkout, so that there is a problem that the dimensional accuracy decreases. The diameter of the surface Wa to be ground when the spark-out is completely performed is a value obtained by subtracting twice the bending of the workpiece W at the end of the fine grinding from the diameter of the circle shown by the broken line in FIG.

An object of the present invention is to solve each of the problems described above, to increase the roundness in spite of the short processing time and to minimize the deterioration of the dimensional accuracy.

[0006]

To this end, the grinding apparatus according to the present invention, as shown in FIG. 1, has a grinding wheel base 13 having a grinding wheel 19 which is rotationally driven by a motor, the grinding wheel 19 and the grinding wheel 19 thereby. Driving means 100 for relatively moving the grindstone base 13 and the workpiece W in a direction in which the workpieces W to be ground approach or separate from each other, and position detection means 110 for detecting the position of the grindstone base 13 with respect to the workpiece W. , Measuring means 1 for measuring the outer diameter of the surface Wa to be ground of the workpiece W during grinding
20 and the driving means 100 are operated in the approaching direction to perform the pre-stage grinding of the grinding surface Wa by the grinding wheel 19 and the subsequent finish grinding, and the outside of the grinding surface Wa measured by the measuring means 120. In the grinding apparatus including the control means 130 for finishing the finish grinding when the diameter reaches the finish target diameter, the distance corresponding to the bending of the workpiece W on the ground surface Wa due to the grinding resistance at the time of finishing the grinding is calculated. The calculation means 90 is provided, and the control means 130 obtains the grindstone base 13 and the work W by the calculation means 90 while performing grinding by the grinding wheel 19 during the number of revolutions of the work following the completion of the finish grinding. It is characterized in that it is relatively moved in the separating direction by a predetermined distance.

Here, it is conceivable that the calculating means calculates a distance corresponding to the bending based on the rigidity of the workpiece W.

Alternatively, the calculating means calculates a distance corresponding to the bending based on the position of the grindstone base 13 detected by the position detecting means and the outer diameter of the workpiece detected by the measuring means. It is possible to

[0009]

The control means 130 causes the grinding wheel base 13 and the grinding wheel 19 to approach each other via the driving means 100, and finishes the surface to be ground Wa of the workpiece W by the grinding wheel 19 and finishes the measurement.
When the outer diameter of the surface to be ground Wa measured by 0 reaches a predetermined finishing target diameter D, finish grinding is completed. Also, the calculation means 9
0 calculates the distance corresponding to the deflection of the workpiece W at the end of finish grinding. During the number of rotations of the workpiece W following the end of the finish grinding, the control means 130 moves the grindstone 13 and the workpiece W in the direction away from each other by the distance calculated by the computing means 90. The surface to be ground Wa, which was in the shape of a part of the spiral surface immediately after finishing grinding, was rounded by the grinding during one revolution of the workpiece from the completion of finishing grinding. By the movement of the object W and the grinding wheel 19 in the separating direction, the deflection of the workpiece W, which gives the grinding resistance required for grinding the surface Wa to be ground by the grinding wheel 19, decreases to 0, so that grinding is not performed.

[0010]

EXAMPLES The present invention will be described below with reference to examples shown in FIGS. As shown in FIG. 2, a headstock 14 and a tailstock 16 for bearing a main spindle 15 and a tailstock 16 are placed on the left and right sides of a worktable 12, which is guided and supported on a bed 11 of a grinding machine 10 so as to be movable in the left-right direction (Z direction). The workpiece W is coaxially provided so as to be opposed to each other in the direction of the center 1 provided on the spindle 15 and the tailstock 16.
Both ends are supported by 5a and 16a. The spindle 15 is rotationally driven by a motor 18 provided on the spindle stock 14, and the workpiece W has a left end portion protruding from the spindle 15 to prevent the detent member 1 from rotating.
7 and is rotated together with the main shaft 15.

A grindstone base 13 is guided and supported on the bed 11 so as to be movable in a horizontal X direction orthogonal to the Z direction, and a grindstone wheel 19 such as a CBN grindstone is parallel to the spindle 15 on the grindstone base 13. It is supported by a simple grindstone shaft 20 and is rotationally driven by a motor 22 via a V-belt rotation transmission mechanism 21. The servomotor 23 provided in the bed 11 is controlled and driven by a drive circuit 41 that operates based on a control pulse distributed from the pulse distribution circuit 34 of the numerical controller 30, and the grindstone base 13 is driven via a feed screw device (not shown). To feed in the X direction. Position detector 2 such as encoder
Reference numeral 5 detects the moving position of the grindstone 13 via the rotation angle of the servomotor 23, and the detected value is the sensor controller 4
It is input to the numerical control device 30 via 2.

The in-process measuring device 24 installed on the work table 12 engages the tip ends of a pair of measuring elements 24a with the surface to be ground Wa of the work W being ground to determine its outer diameter. Direct and continuous measurement, and its measurement signal (analog signal)
Is input to the numerical controller 30.

As shown in FIG. 2, the numerical control device 30 has a
Central processing unit (CPU) that controls and manages the entire grinding machine
3, a memory 32, an interface 33 for exchanging data with the outside, and a pulse distribution circuit 34 for distributing and transmitting drive pulses in response to a command from the CPU 31. The measuring device 24 is connected to the CPU 31 via the AD converter 35, and the sensor controller 42 is connected to the CPU 31. This sensor controller 42 is a CPU
The position detector 25 is connected to the position detector 25 described above. Further, the interface 33 is connected to an input device 40 such as a keyboard for inputting control data and the like, and the pulse distribution circuit 34 is connected to the servo motor 23 described above via a drive circuit 41. The memory 32 stores a machining program for machining the workpiece W and other data.

In the relationship between the present embodiment and the claims, the servomotor 23 is the driving means 100, the position detector 25 is the position detecting means 110, the measuring device 24 is the measuring means 120, the CPU 31 and the pulse distribution circuit 34. Is the control means 130, and the CPU 31 and the memory 32 are the calculation means 14
0 respectively.

Next, the operation of the present embodiment configured as described above will be described with reference to the flow chart shown in FIG. 3 and FIGS.
Will be described with reference to FIG. When the grinding device starts to operate according to a command from the input device 40, the grinding process is started according to the processing program shown in the flowchart of FIG. First, the CPU 31 of the numerical control device 30 performs the rough grinding in step 101. That is, the grindstone 19 rotates, the workpiece W supported by the headstock 14 and the tailstock 16 is rotated at a predetermined speed by the motor 18, and the CPU 31 sets the grindstone 13 at a preset rough grinding feed speed. Move forward,
Rough grinding of the workpiece W is performed. The CPU 31 decodes the grindstone rough grinding feed command in the machining program and gives a command value to the pulse distribution circuit 34, whereby the pulse distribution circuit 34.
By applying a pulse signal sent from the servo motor 23 to the servo motor 23 via the drive circuit 41, the servo motor 23 is driven to perform rough grinding.

In this case, when the cutting feed is applied to the grindstone base 13, the cutting feed position of the grindstone base 13 which changes moment by moment is detected by the position detector 25, and the detected value is input to the CPU 31 via the sensor controller 42. To be done. The tracing stylus 24a of the measuring device 24 is engaged with the ground surface Wa of the workpiece W, whereby the outer diameter of the ground surface Wa is measured in-process, and the measured value is converted into a digital signal by the AD converter 35. And is input to the CPU 31. In FIG. 4, a solid line A represents the cutting feed position of the grinding wheel base 13 detected by the position detector 25, and a broken line B represents the diameter of the grinding surface Wa detected by the measuring device 24 converted into the position of the grinding wheel base 13. is there.

In the rough grinding, the position of the grindstone base 13 detected by the position detector 25 decreases at a high rough grind cutting feed rate as shown by the solid line A1 in FIG.
If the contact is made, the surface to be ground Wa is ground by the grinding wheel 19, and the diameter of the surface to be ground Wa measured by the measuring device 24 decreases as shown by the broken line B1. The deflection of the workpiece W on the ground surface Wa due to the grinding resistance between the workpiece W and the grinding wheel 19 (including the deflection by the supporting portion of the workpiece W) (hereinafter simply referred to as the deflection of the workpiece W) is the solid line A and It is shown as the difference between the dashed lines B. When the rough grinding progresses and the diameter of the surface to be ground Wa shown by the broken line B1 reaches the rough grinding completion diameter D1 input in advance from the input device 40, the CPU 31 determines in step 102 that the rough grinding is completed, and the control operation is performed. Proceed to the fine grinding in step 104.

In step 104, the CPU 31 advances the grindstone base 13 at a fine-grinding feed speed slower than the rough-grind feed speed, fine-grinds the workpiece W as in the rough-grind feed, and detects it by the position detector 25. The cutting feed position of the grindstone base 13 is decreased as shown by the solid line A2, and the measuring device 24
The outer diameter of the surface to be ground Wa detected by is decreased as shown by the broken line B2, and these detected values are input to the CPU 31.
If the fine grinding progresses and the diameter of the surface Wa to be ground indicated by the broken line B2 reaches the fine grinding completion diameter D2 previously input from the input device 40, C
The PU 31 determines in step 105 that the fine grinding is completed and advances the control operation to the fine grinding in step 106.
During this fine grinding, the deflection of the workpiece W due to grinding resistance is
As indicated by the difference between the solid line A2 and the broken line B2, it gradually decreases and converges to a constant value.

At step 106, the CPU 31 advances the grindstone base 13 at a fine grinding feed rate slower than the fine grinding feed rate as shown by the solid line A3, and finely grinds the workpiece W as described above. As a result, the diameter of the surface to be ground Wa measured by the measuring device 24 decreases as shown by the broken line B3, and when the finish target diameter D input in advance is reached, the CPU 31 determines in step 107 that the fine grinding has been completed. The control operation is advanced to the backward movement amount calculation in step 108. During this fine grinding, the deflection of the workpiece W due to the grinding resistance gradually decreases as shown by the difference between the solid line A3 and the broken line B3, and converges to a constant value smaller than that in the fine grinding.

In step 108, the CPU 31 calculates the amount of retreat corresponding to the bending of the workpiece W due to the grinding resistance at the end of the fine grinding according to the following expression 1. Amount of retreat = Workpiece diameter-Grinding surface diameter obtained from grindstone position ... 1 = (D / 2) -H However, the workpiece diameter and grindstone position in the above formula are measured at the end of fine grinding. It is the diameter of the workpiece W and the position of the grindstone 13 detected by the device 24 and the position detector 25, and the error due to thermal displacement or the like is excluded. The diameter obtained from the grindstone position here is the distance H from the rotation center O of the workpiece W shown in FIG. 5 to the tip position of the grinding wheel 19.

At the following step 109, the CPU 31
Calculates the retreat speed for retreating the grinding wheel head 13 by the above-mentioned retreat amount during the rotation of the workpiece W by the following equation 2. Backward speed = backward amount × rotational speed of the workpiece W ... 2 In this formula 2, the grinding wheel head 13 is retracted by the amount of the backward movement while the workpiece W makes one revolution. Instead, it may be rotated several times such as 0.5 rotation and 2 rotations. In this case, the equation 2 is transformed into the following equation 2a. Retraction speed = Retraction amount × Rotation speed of workpiece W / rotation speed ... 2a However, if this rotation speed is increased, the roundness is improved but the dimensional accuracy is deteriorated and the cycle time is extended.
If it is less than one rotation, the roundness will be poor. For this reason, experimentally, it is a circularity to retract in one rotation,
It is a desirable value in terms of dimensional accuracy and cycle time.

The CPU 31 then proceeds to the next step 110.
In order to move the workpiece W by the above-mentioned amount of deflection while the workpiece W makes one revolution at the above-mentioned rotation speed, the grinding stone head 13 is slowly retracted at the above-described retreat speed (see solid line A4 in FIG. 4) to finish the target diameter D. To the position corresponding to, while grinding by the grinding wheel 19 is continued. In the following step 111, the CPU
In step 31, the grindstone base 13 is fast-forwarded and retracted (see the solid line A5 in FIG. 4), and the machining program shown in the flowchart in FIG. 3 ends.

At the time when the fine grinding in step 107 is completed, as shown in FIG. 5, the surface to be ground Wa of the workpiece W has a shape forming a part of the spiral surface, and the surface to be ground Wa is a grindstone. It is bent in the direction away from the grinding wheel 19 due to the grinding resistance acting between the wheel 19 and the wheel 19, and the amount of bending is equal to the above-mentioned amount of retreat. Therefore, the flexure of the workpiece W becomes 0 after the completion of one rotation accompanied by the retreat of the grinding wheel base 13 in step 110, and the grinding wheel 19 is in a position in contact with the circle shown by the broken line in FIG. Then, during this one rotation, the portion outside the circle of the broken line is ground and the surface to be ground Wa is made into the shape shown by the circle of the broken line, and the subsequent grinding is not performed. Therefore, the roundness does not decrease even if the fine grinding feed is increased, and the diameter of the grinding surface Wa detected by the measuring device 24 decreases by the amount shown by c in FIG. Unlike the case of the prior art in which spark-out is performed, there is no reduction in the diameter due to springback of the bending of the workpiece W. Therefore, the decrease in dimensional accuracy is the minimum necessary for rounding, and is smaller than that in the conventional technique for performing sparkout. Since the reduction value c of the diameter is the same as the cutting feed amount per one rotation of the workpiece W at the time of fine grinding, the reduction of the dimensional accuracy can be reduced by increasing the finishing target diameter D accordingly. You can

In the above embodiment, the amount of retreat (= deflection of the workpiece W due to the grinding resistance at the end of fine grinding) for calculating the retreat speed at the time of low speed retreat of the wheel head 13 indicated by the solid line A4 in FIG. , The diameter of the workpiece W detected by the measuring device 24 and the position detector 25 at the end of the fine grinding and the wheel head 1
The calculation is performed based on the position of 3. On the other hand, in the flowchart of the modified example shown in FIG.
In step 103 following the completion of rough grinding, the amount of retreat is calculated by the following equation 3. Retreat amount = (workpiece diameter-diameter obtained from the grinding wheel position) x fine grinding speed / rough grinding speed ... 3 However, the workpiece diameter and the grinding wheel position in the above formula 3 are measured at the end of rough grinding, respectively. The diameter of the workpiece W and the position of the grindstone 13 detected by the device 24 and the position detector 25.

The inside of the parentheses of the above equation 3 is the deflection of the workpiece W at the end of rough grinding. On the other hand, the grinding wheel 19 with the same rotation speed
In the case of continuously grinding by means of, the deflection of the work due to the grinding resistance in the converged state becomes the grinding speed (the cutting feed speed of the grinding wheel) as long as the time interval is short and therefore the change in the sharpness of the grinding wheel 19 is small. Since they are proportional, they have the following relationship. Fine grinding speed / rough grinding speed = deflection amount during fine grinding / deflection amount during rough grinding Therefore, the retreat amount according to the above equation 3 is substantially the same as the retreat amount according to the previous equation 1.

The modified embodiment of FIG. 6 is the same as the embodiment shown in FIGS. 2 to 5, except that step 108 is deleted as described above, and instead the backward movement amount is calculated in step 103 as described above. The same effect can be obtained. The calculation of the retreat speed in this modified embodiment is not limited to the position of step 109, but steps 103 and 1
It may be performed at an arbitrary time point between 10. In this modified embodiment, since there is a time margin in the calculation of the reverse speed as compared with the above-mentioned embodiment, there is no possibility that the operation of step 110 will be delayed. In this modified embodiment, step 102
The amount of retreat is calculated between Step 105 and Step 104. However, between Step 105 and Step 106, the amount of retreat is calculated based on the workpiece diameter at the end of fine grinding, the wheel head position, and the fine grinding speed and the fine grinding speed. May be calculated.

In the modified embodiment shown in the flow chart of FIG. 7, instead of calculating the retreat amount each time machining is performed as in each of the above-described embodiments, the workpiece information (shape, material, etc.) of each workpiece is previously stored.
The rigidity of the workpiece is calculated based on the above, and using the value and the machining information, the retreat amount corresponding to the deflection of the workpiece W due to the grinding resistance at the end of the fine grinding is calculated by the following equation 4 and the memory 32
To remember. Amount of retreat = k × fine grinding speed / rigidity of workpiece ... 4 However, k is an experimentally obtained coefficient. In the modified embodiment of FIG. 7, step 100 is added and step 108 is deleted. 2 to 5 are the same as the above-mentioned embodiment. First, the CPU 31 reads in the retreat amount of the corresponding workpiece stored in the memory 32 in step 100, performs rough grinding, fine grinding and fine grinding in steps 101 to 107 as in each of the above-described embodiments, and then executes steps 109 and 1.
In step 10, the backward speed calculation and the grinding wheel head low speed backward step are performed to perform the machining. As a result, the same operational effects as those of the above-described respective embodiments can be obtained. Also in this modified embodiment, the calculation of the reverse speed may be performed at any time between step 100 and step 110. Alternatively, the backward speed may be calculated in advance based on the processing information, stored in the memory 32, read in step 100, and the calculation in step 109 may be omitted. As in the case of the modified example described above, in this modified example as well, there is a time margin in the calculation of the reverse speed, so there is no risk of delay in the operation of step 110.

Further, in a grinding machine in which grinding conditions (grinding head feed rate, feed rate, etc.) are automatically determined by calculation when performing grinding, the rigidity of the workpiece may be used. In the grinding machine, the rigidity is not used only for obtaining the amount of retreat, which is effective.

In the relationship between each of the above-described embodiments and claims, rough grinding and fine grinding correspond to pre-stage grinding, and fine grinding corresponds to finish grinding.

[0030]

As described above, according to the present invention, since the surface to be ground is rounded from the completion of the finish grinding to one revolution of the workpiece, the finishing grinding feed rate is increased to reduce the machining time. Even if it is done, the roundness of the surface to be ground does not decrease, and since the grinding is not performed after the completion of the finish grinding and after the rotation of the workpiece W1, the deterioration of the dimensional accuracy is minimized.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a grinding apparatus according to the present invention.

FIG. 2 is a diagram showing an overall configuration of an embodiment of a grinding apparatus according to the present invention.

FIG. 3 is a flowchart showing a machining program of the embodiment shown in FIG.

FIG. 4 is an explanatory view of the operation of the embodiment shown in FIG.

5 is an explanatory view showing a surface to be ground and its vicinity at the time of completion of finish grinding in the embodiment shown in FIG. 2. FIG.

FIG. 6 is a flowchart of a modification of the machining program shown in FIG.

FIG. 7 is a flowchart of another modification of the machining program shown in FIG.

FIG. 8 is a diagram showing a main part of an example of a grinding apparatus targeted by the present invention.

FIG. 9 is an explanatory diagram of an operation of a conventional grinding device.

[Explanation of Codes] 13 ... Grinding stone base, 19 ... Grinding wheel, 90 ... Computing means, 100
... drive means, 110 ... position detection means, 120 ... measurement means, 130 ... control means, W ... workpiece, Wa ... ground surface.

Claims (3)

[Claims] 1. A grindstone base having a grindstone wheel that is driven to rotate by a motor, and drive means for relatively moving the grindstone base and the workpiece in a direction in which the grindstone wheel and a workpiece ground by the grindstone wheel move toward or away from each other. Position detecting means for detecting the position of the grindstone with respect to the workpiece, measuring means for measuring the outer diameter of the surface to be ground of the workpiece during grinding, and the driving means for operating in the approaching direction. Grinding provided with a control means that performs pre-stage grinding of the surface to be ground by a grinding wheel and subsequent finish grinding, and finishes the finish grinding when the outer diameter of the surface to be ground measured by the measuring means reaches a finish target diameter. In the apparatus, there is provided computing means for computing the distance corresponding to the deflection of the work surface to be ground due to the grinding resistance at the end of the finish grinding, and the control means is provided for the work following the completion of the finish grinding. A grinding apparatus characterized in that, during the rotation of the number of crops, while the grinding wheel is grinding, the grinding wheel base and the workpiece are relatively moved in the separating direction by the distance obtained by the calculation means. 2. The grinding apparatus according to claim 1, wherein the computing means computes a distance corresponding to the bending based on the rigidity of the workpiece W. 3. The calculation means calculates a distance corresponding to the deflection based on the position of the grindstone base 13 detected by the position detection means and the outer diameter of the workpiece detected by the measurement means. The grinding apparatus according to claim 1.