JP2022110834A - Grinder and control device of grinder - Google Patents

Abstract

To provide a grinder which can accurately perform continuous rotation processing and rotation stop processing on workpiece having a large inertial moment using a motor having a small capacity.SOLUTION: A grinder includes a storage part 40 for storing a plurality of servo parameters for determining a holding torque for holding workpiece W by a main spindle 2, according to a processing method in a state where the workpiece W is in a continuously rotated state or in a rotation stop state, a main spindle control part 20 for controlling the main spindle, and a parameter switching part 50 for acquiring the servo parameter according to the executed processing method from the storage part, and setting the servo parameter to the main spindle control part, wherein the parameter switching part switches the servo parameter to a servo parameter for giving a holding torque higher than the case where a processing method for grinding the workpiece while holding the workpiece in the continuously rotated state so as to hold the workpiece in the rotation stop state with the main spindle against a processing load is performed, to the main spindle, when a processing method for grinding the workpiece while holding the workpiece in the rotation stop state is performed.SELECTED DRAWING: Figure 6

Description

The present invention relates to a grinding machine and a control device for the grinding machine.

Conventionally, in the grinding process of cutting the surface of a workpiece and finishing it to a predetermined shape and dimensional accuracy, there is a method of grinding while the workpiece is continuously rotating, and a method of grinding while the workpiece is stopped rotating. be.

As an apparatus for grinding a workpiece while it is continuously rotated, for example, as in Patent Document 1, there is a grinder that grinds the inner peripheral surface of a cylindrical workpiece while continuously rotating the workpiece and the grinding wheel, respectively. It has been known. As an apparatus for grinding a workpiece while the rotation is stopped, for example, as in Patent Document 2, a grinding wheel is continuously rotated while the workpiece is held in a state where the rotation is stopped by a spindle, and a cylindrical shape is formed. A grinding machine is known which grinds an arc-shaped recessed groove when viewed from the axial direction on the inner surface of a workpiece. Also known is a grinder capable of combined processing, which performs a plurality of these different grinding processes with a single machine.

In a conventional grinder that performs compound machining, control of a spindle that holds a workpiece is performed using one type of servo parameter. In other words, the same servo parameters as those used when grinding the workpiece while it is continuously rotating are also used when grinding the workpiece while the rotation is stopped.

Japanese Patent No. 5443212 JP 2019-72797 A

By the way, when a motor of a certain size is used and the motor drives a spindle to hold a workpiece in a rotating or non-rotating state, as the size of the workpiece increases, the rotor, which is a component part of the motor, and the workpiece become larger. The moment of inertia ratio with the object becomes large.

When the moment of inertia ratio of the workpiece to the rotor is relatively small, for example, 50 or less, grinding is performed while the workpiece is continuously rotated like a conventional grinding machine that performs compound machining. Even if the same parameters as the parameters of are used when grinding while holding the workpiece in a state where rotation is stopped, the deviation of the spindle angle that occurs when rotation is stopped does not affect the machining accuracy. Not a problem. However, a problem arises when using the same size motor for compound machining of larger workpieces. If the moment of inertia ratio of the workpiece to the rotor is very large, e.g. greater than 50, the workpiece is rotated with the same parameters as those for grinding with the workpiece continuously rotated. If it is used for grinding while holding it in a stopped state, the holding force when the motor stops rotating is less than the machining resistance, so the angle deviation of the spindle when rotation stops is large, and machining accuracy cannot be satisfied. . In order to solve this problem, it is easily conceivable to use a motor with a larger capacity to reduce the moment of inertia ratio with the workpiece, but in that case, there is a disadvantage that the size of the apparatus is unavoidable.

The present invention has been made in view of the above points, and its object is to achieve continuous rotary machining and rotation with high accuracy using a small-capacity motor even for workpieces with a very large moment of inertia. To provide a grinding machine capable of stop machining.

In order to achieve the above object, according to the present invention, a plurality of servo parameters for controlling the spindle are used according to the machining method.

Specifically, in the first invention, the grinder performs compound machining while the workpiece is continuously rotated and stopped rotating by a spindle holding the workpiece, wherein the spindle holds the workpiece. A storage unit that stores a plurality of servo parameters that determine a holding torque for holding an object according to a machining method in which the workpiece is continuously rotated or stopped rotating, and a spindle that controls the spindle. and a parameter switching unit that acquires the servo parameters corresponding to the machining method to be executed from the storage unit and sets them in the spindle control unit. When a machining method for grinding an object while holding it in a non-rotating state is performed, the workpiece is continuously held so that the main shaft can hold the workpiece in a non-rotating state against the machining load. It is characterized by switching to the servo parameter that gives a higher holding torque to the main spindle than when a machining method of grinding while holding it in a rotated state is carried out.

According to the above configuration, the machining accuracy can be improved by acquiring the servo parameter corresponding to the machining method from the plurality of servo parameters. In particular, when the workpiece is stopped rotating, the servo parameters can be switched to provide a higher holding torque than when grinding while holding the workpiece in a continuously rotating state. The workpiece can be held, and the angular displacement of the spindle does not occur. With such a configuration, even if the workpiece has a very large moment of inertia, it is possible to perform continuous rotation machining and rotation stop machining with high accuracy using a small-capacity motor.

In the second invention, a plurality of servo parameters are stored for determining a holding torque for the spindle to hold the workpiece according to a machining method in which the workpiece is continuously rotated or stopped rotating. a parameter switching step of acquiring the servo parameters according to the machining method to be executed from the stored storage unit, and setting the acquired servo parameters to a spindle control unit that controls the spindle; In the step, when a machining method is implemented in which the workpiece is ground while holding the workpiece in a non-rotating state, the main shaft can hold the workpiece in a non-rotating state against the machining load. It is characterized in that the servo parameters are obtained that give a higher holding torque to the spindle than when a machining method is performed in which the workpiece is ground while holding the workpiece in a continuously rotating state.

According to the above configuration, as in the first invention, it is possible to improve the machining accuracy by switching from a plurality of servo parameters to servo parameters according to the machining method, and it is possible to improve the machining accuracy of workpieces with a very large moment of inertia. However, by using a small-capacity motor, continuous rotation machining and rotation stop machining can be performed with high accuracy.

As described above, according to the present invention, the spindle is controlled by the servo parameters according to the machining method, so that even a workpiece with a very large moment of inertia can be accurately controlled by using a small-capacity motor. It is possible to perform continuous rotation machining and rotation stop machining well.

It is a lineblock diagram showing an example of a grinder concerning an embodiment of the present invention. FIG. 4 is a cross-sectional view showing a state in which a workpiece is attached to the spindle; 4 is a table for explaining the moment of inertia ratio between a workpiece and a rotor; It is a cross-sectional view showing an example of grooving of a workpiece. It is a schematic diagram which shows an example of another grinding tool. 4 is a flow chart showing an example of processing of a grinding machine during grooving. 10 is a table showing deviation amounts during groove processing in Example 3 and Comparative Example 1. FIG. 10 is a table showing servo parameters used in Example 3;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail based on the drawings. It should be noted that the following description of preferred embodiments is essentially merely illustrative, and is not intended to limit the invention, its applications, or its uses.

(Grinding machine configuration)
FIG. 1 is a configuration diagram showing an example of a grinder according to an embodiment of the present invention. The grinder 1 performs compound machining while the workpiece W is continuously rotated around the spindle 2 by a spindle 2 that holds the workpiece W, and while the rotation is stopped. The grinding machine 1 includes a control device 4, which controls the grinding operation of the workpiece W by the grinding tool 3, the indexing of the position of the workpiece W by the spindle 2, continuous rotation or rotation stop, etc. Various movements of are controlled in an integrated manner.

The main shaft 2 extends vertically. A chuck 6 is provided at the upper end of the spindle 2 , and the spindle 2 holds a workpiece W through the chuck 6 . An electromagnet (not shown) is attached to the chuck 6, and the workpiece W is held on the spindle 2 with a predetermined holding torque by supplying current to the electromagnet.

Specifically, as shown in FIG. 2, a cylindrical workpiece W is held by the spindle 2 via a chuck 6 . The spindle 2 is rotationally driven by a motor 5 . The spindle 2 is rotatably supported by a spindle housing 2a fixed to the work table 10 via upper and lower bearings 9a and 9b.

The motor 5 includes a rotor 5a and a stator 5b. A rotor 5a is fixed to the outer periphery of the main shaft 2, and a stator 5b fixed to the main shaft housing 2a side is positioned on the outer periphery of the rotor 5a. When the stator 5b is energized, the spindle 2 and the workpiece W held by the spindle 2 are integrally rotated. The motor 5 is controlled by servo parameters set in the controller 4, which will be described later. Servo parameters include gain adjustment parameters.

Incidentally, depending on the size of the workpiece W, chucks 6 of different sizes may be attached.

FIG. 3 is a table showing the moment of inertia ratio between the workpiece and the rotor when workpieces W of different sizes are attached when a small-capacity motor is used. A small-capacity motor is here a motor 5 having a rotor 5a with a moment of inertia of 0.06 kg·m ² . In Example 1, a workpiece W having a moment of inertia of 2.9 kg·m ² is attached to the spindle 2 driven by the rotor 5a. The moment of inertia ratio of the workpiece W to the rotor 5a is 48, which can be said to be a relatively small value. In the second embodiment, a workpiece W having a moment of inertia of 16.2 kg·m ² is attached to the spindle 2 driven by the rotor 5a having the same moment of inertia of 0.06 kg·m ² as in the first embodiment. The moment of inertia ratio of the workpiece W to the rotor 5a is 270, which can be said to be a considerably large value.

The grinding tool 3 is a tool for grinding the workpiece W. The grinding tool 3 is vertically movable, and has a grindstone for grinding the workpiece W at its lower end. The grinding machine 1 can be equipped with various grinding tools 3 depending on the machining method. For example, as shown in FIG. 1, the grinding tool 3 may have a grindstone 3a for grooving the workpiece W. As shown in FIG. The grinding wheel 3a is a grinding wheel having a rotating shaft in a direction perpendicular to the vertical direction. When such a grinding tool 3 is used, the grinding wheel rotates and descends, for example, as shown in FIG. Recessed grooves can be ground.

Further, the grinding tool 3 may have a grindstone 3b for cylindrical machining of the workpiece W, as shown in FIG. The grindstone 3b is a cylindrical grindstone having a rotation axis in the vertical direction. The grinding tool 3 having such a cylindrical grindstone 3b is rotated and lowered, and can grind the inner and outer peripheral surfaces of the cylindrical workpiece W to a predetermined dimensional accuracy.

(Configuration of control device)
A control device 4 that controls the grinding machine 1 controls the spindle 2 and the grinding tool 3 by numerical control. The control device 4 has a spindle control section 20 that controls the gain of the spindle 2 in order to bring the workpiece W into a rotating state or a rotation stop state. The spindle controller 20 can control the spindle 2 by controlling the motor 5 that drives the spindle 2 . The control device 4 also has a tool control section 30 for controlling the grinding tool 3, such as grinding operation for the workpiece W, position data, rotation angle data, and the like. The tool control unit 30 can control the grinding tool 3 by controlling a tool drive motor (not shown) for driving the rotation and position movement of the grinding tool 3 .

The control device 4 includes a storage section 40 that stores various data and parameters necessary for controlling the grinder 1 . The storage unit 40 stores operation programs of various machining methods for grinding while the workpiece W is continuously rotated or stopped, and holding torque for the spindle 2 to hold the workpiece W is determined. servo parameters are stored. The storage unit 40 stores a plurality of servo parameters according to the machining method when the workpiece W is continuously rotated or stopped. Servo parameters include, for example, model control gains, position control gains and velocity control gains.

The control device 4 includes a parameter switching unit 50 that acquires various parameters corresponding to the machining method executed by the grinder 1 from the storage unit 40 and sets the acquired parameters to the spindle control unit 20 and the tool control unit 30. . For example, the parameter switching unit 50 acquires servo parameters corresponding to the machining method to be executed from the storage unit 40 and sets the acquired servo parameters in the spindle control unit 20 .

The parameter switching unit 50 holds the workpiece W in a non-rotating state against the machining load of the main spindle 2 when a machining method of grinding the workpiece W while holding the non-rotating one is performed. Therefore, the servo parameters are switched to those that give a higher holding torque to the spindle 2 than in the case where the machining method of grinding while holding the workpiece W in a state of continuous rotation is implemented. The operation of the parameter switching unit 50 may be automatically switched by an operation program stored in advance, but may be appropriately switched by a manual operation such as a monitor operation by an operator or an operation by a controller. good too.

Each component in the control device 4 and the connection relationship between the components are not necessarily limited to the configuration shown in FIG. 1, and the connection relationship is arbitrary. For example, the spindle control unit 20 and the tool control unit 30 may not be independent components, and may control each component as a plurality of functions possessed by one control unit. The storage unit 40 can be composed of various memories such as flash memory, RAM (random access memory), ROM (read only memory), HDD (hard disk drive), SSD (Solid State Drive), and the like. The spindle control unit 20 and the tool control unit 30 can be configured by a CPU, MPU, system LSI, DSP, dedicated hardware, or the like.

(Grinding method and spindle control)
When the servo parameters are switched by the spindle control unit 20, the gain is changed and the responsiveness of the motor 5 is changed. As the responsiveness of the motor 5 changes, the responsiveness of the spindle 2 driven by the motor 5 also changes. The main shaft 2 exhibits quick response to control when a higher gain is applied, and slow but smooth response when a lower gain is applied. Specifically, when the servo parameters that control the spindle 2 have a low gain, the torque sensitivity and maximum current applied to the spindle 2 are controlled to be low, and the holding torque for holding the workpiece W is low. Become. On the other hand, when the servo parameter has a high gain, the torque sensitivity and maximum current applied to the spindle are controlled to be high, and the holding torque for holding the workpiece W is high.

When the workpiece W held by the spindle 2 exhibiting such characteristics is subjected to combined machining in a continuous rotation state and a rotation stopped state, the servo parameters are switched according to the grinding method, and an optimum gain is given to the spindle 2. Therefore, machining accuracy can be improved.

For example, when the inner and outer peripheral surfaces of the workpiece W are ground while the automatic control is turned off and the workpiece W is continuously rotated, or as shown in FIG. On the other hand, in the case of grinding the groove 11 that is recessed in an arc shape when viewed from the direction of the spindle, when the workpiece W is rotated by a predetermined angle θ and indexed to the next groove processing position, Use low gain servo parameters. When grinding a workpiece W in a rotating state or performing a positioning operation, a low-gain servo parameter is used for smooth operation, so that machining accuracy is satisfied without generating vibration during grinding. can be done. If a high-gain servo parameter is used for such a grinding method, vibration occurs during machining, and machining accuracy cannot be satisfied.

Also, for example, the workpiece W is held in a state where rotation is stopped, and as shown in FIG. is required to hold the position of the workpiece W against the grinding load generated during the grinding process. When grinding the workpiece W while the rotation is stopped, high-gain servo parameters are used. By generating a sufficient holding torque in the main spindle 2 using high-gain servo parameters, it is possible to satisfy machining accuracy without causing an angular deviation of the main spindle 2 due to the grinding load of the grinding tool 3 . If a low-gain servo parameter is used for such a machining method, the holding torque cannot resist the grinding load, causing angular deviation of the main spindle 2, and machining accuracy cannot be satisfied. .

(Spindle control during grooving)
Next, as shown in FIG. 4, spindle control when a plurality of grooves 11, which are recessed in an arcuate shape when viewed from the spindle direction, are machined in the inner peripheral surface of the workpiece W in the circumferential direction is shown in the flow chart of FIG. will be explained based on

First, the grinder 1 is powered on. The operator causes the chuck 6 to hold the workpiece W and sets the grinding conditions and the like using an operation panel (not shown), whereby a program is executed in step S1 to start grooving. In step S1, according to a program set by the operator, the parameter switching unit 50 selects a parameter stored in the storage unit 40 to provide a low holding torque to the main shaft 2 so that the main shaft 2 can operate smoothly. 1 is a parameter switching step in which servo parameters are acquired. Note that the first servo parameter may already be set when the power is turned on.

In step S2, the spindle 2 is rotated by a predetermined angle and indexed to the machining groove position of the workpiece W in a state where the first servo parameter of such a lower gain is set.

Next, in step S3, the parameter switching unit 50 selects a high holding torque from among the parameters stored in the storage unit 40 so that the spindle 2 can hold the workpiece W in a stopped state against the machining load. to the spindle 2 to acquire the second servo parameter of high gain. Step S3 is a parameter switching step.

With the high-gain second servo parameter set, in step S4, the spindle 2 holds the workpiece W in a non-rotating state, and the grindstone 3a descends while rotating to reach the inner surface of the workpiece W. A groove 11 is formed by cutting.

Subsequently, in step S5, it is determined whether grooving is to be continued or terminated. At this time, the grindstone 3a is in a state of being raised and separated from the workpiece W once. If the determination is NO and grooving is to be continued, the process proceeds to step S6, which is a parameter switching step.

Step S6 is a preparatory stage for indexing the spindle 2 to the next machined groove position, and the parameter switching unit 50 switches from the high-gain second servo parameter to the lower-gain first servo parameter.

Next, in step S2, the spindle 2 is rotated by a predetermined angle with the first servo parameter having a lower gain set, and indexed to the machined groove position.

After indexing to the position, the second servo parameter with a higher gain is again switched in step S3, and grooving is performed in step S4. In this way, steps S2 to S6 are repeated a plurality of times, and when all groove machining is completed, a determination of YES is made in step S5, and the gain is switched to the first servo parameter of a lower gain in step S7. Machining ends.

In this way, in the case of grinding a plurality of arc-shaped recessed grooves in the inner surface of the workpiece W in the circumferential direction when viewed from the direction of the spindle, the spindle 2 is rotated by a predetermined angle to determine the position. Grinding accuracy can be improved by properly using two types of servo parameters for grinding with W stopped rotating.

FIG. 7 shows a case where grooving is performed using only one type of servo parameter (comparative example 1), and a case where grooving is performed using two types of servo parameters using the same grinding machine as in comparative example 1 (implementation 3) is a table for comparing the grinding accuracy with Example 3). Example 3 has an inertia moment ratio of 324, and Comparative Example 1 has an inertia moment ratio of 115. In Example 3, although the workpiece W2 having a larger moment of inertia ratio than the workpiece W1 machined in Comparative Example 1 was machined, the displacement in the rotational direction of the main spindle 2 after machining was 0.013 μm/cm. N, which was lower than the shift amount of 4.05 μm/N in Comparative Example 1. From these results, it can be seen that using a plurality of servo parameters according to the machining method with the workpiece continuously rotated or stopped rotating improves the machining accuracy more than when only one servo parameter is used. It has been proven that it can be improved. By using a plurality of servo parameters in this way, it is possible to machine a workpiece having a large moment of inertia. It is possible to perform continuous rotation machining and rotation stop machining with high accuracy.

FIG. 8 shows the low-gain first servo parameter and the high-gain second servo parameter used in the machining of the third embodiment. The model control gain, the position control gain, and the velocity control gain are each set to a higher value in the high gain second servo parameter than in the low gain first servo parameter.

The above-described embodiments are merely examples in all respects and should not be construed in a restrictive manner. Furthermore, all modifications and changes within the equivalent range of claims are within the scope of the present invention.

REFERENCE SIGNS LIST 1 grinding machine 2 spindle 2a spindle housing 3 grinding tool 3a grinding wheel 3b grinding wheel 4 control device 5 motor 5a rotor 5b stator 6 chuck 10 work table 11 groove 20 spindle control section 30 tool control section 40 storage section 50 parameter switching section W workpiece

Claims (2)

A grinding machine that performs compound machining while the workpiece is continuously rotated and stopped rotating by a spindle that holds the workpiece,
a storage unit that stores a plurality of servo parameters for determining a holding torque for the spindle to hold the workpiece according to a machining method in which the workpiece is continuously rotated or stopped rotating;
a spindle control unit that controls the spindle;
a parameter switching unit that acquires the servo parameters corresponding to the machining method to be executed from the storage unit and sets them in the spindle control unit;
a controller having
The parameter switching unit is configured to hold the workpiece in a state where the workpiece is stopped from rotating against the machining load of the main spindle when a machining method is performed in which the workpiece is ground while the workpiece is held in a non-rotating state. A grinder characterized in that the servo parameters are switched to provide a higher holding torque to the spindle than when a machining method is implemented in which the workpiece is ground while holding it in a state of continuous rotation so as to be able to do so. A control method for a grinder that performs compound machining while a workpiece is continuously rotated and stopped rotating by a spindle that holds the workpiece, comprising:
from a storage unit storing a plurality of servo parameters for determining a holding torque for the spindle to hold the workpiece according to the machining method in which the workpiece is continuously rotated or stopped rotating; a parameter switching step of acquiring the servo parameters according to the machining method to be executed and setting the acquired servo parameters to a spindle control unit that controls the spindle;
In the parameter switching step, when a machining method is implemented in which the workpiece is ground while the workpiece is held in a non-rotating state, the main shaft holds the workpiece in a non-rotating state against a processing load. A grinder characterized in that the servo parameter is acquired to give a higher holding torque to the spindle than when a machining method is implemented in which the workpiece is ground while holding it in a state of continuous rotation so as to be able to do so. control method.

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