JP5565172B2 - Workpiece surface position variation measuring method and grinding machine - Google Patents

Description

  The present invention relates to measurement of grinding characteristics of a grinding machine, and more specifically, a workpiece surface position for measuring natural frequency and shape accuracy using dynamic pressure generated in a coolant fluid between the workpiece and a grinding wheel. The present invention relates to a variation measuring method and a grinding machine.

In the grinding machine, in order to grind the workpiece with high accuracy and high efficiency, the natural frequency of the workpiece support system and the grinding wheel support system can be grasped to avoid resonance and chatter on the workpiece processing surface. It has been practiced to select a grinding wheel and workpiece rotational speed that are small. For this purpose, it is necessary to measure the natural frequency and to measure the shape of the workpiece surface.
As a means for grasping the natural frequency, a conventional technique 1 (for example, refer to Patent Document 1) in which a vibration pickup is attached to a processing apparatus to measure vibration, and a shape measurement data of a ground workpiece surface is subjected to frequency analysis to perform natural vibration. There is prior art 2 (for example, refer to Patent Document 2) for measuring the number.
In addition, there is a conventional technique 3 (for example, see Patent Document 3) in which a measuring device is provided on a grindstone to measure the shape of a workpiece on the machine.

Japanese Patent Laid-Open No. 5-138499 JP 2001-179620 A JP-A-6-91489

In the prior art 1, in order to measure the vibration by attaching the vibration pickup to the processing apparatus, a special measuring device is required. In order to measure the vibration of the workpiece itself, the vibration pickup must be attached to the work piece, Takes time. Also, the shape of the workpiece cannot be measured.
In the prior art 2, it is not necessary to attach the vibration pickup to the workpiece, but a special device is required for shape measurement and frequency analysis, which is expensive and requires time for measurement.
In the prior art 3, the shape can be measured immediately after machining the workpiece on the machine, but a special device is required and the cost is high.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a simple method capable of measuring the natural frequency of a workpiece system and the shape accuracy of the workpiece on the machine in a short time.

In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a workpiece support means for supporting and rotating a cylindrical workpiece, and a grinding wheel support for supporting and driving a grinding wheel by a driving device. Means, a workpiece moving means for moving the workpiece support means to grind the workpiece with the grinding wheel, a grinding wheel moving means for moving the grinding wheel support means, and a grinding fluid at a grinding point. In a grinding method using a grinding machine provided with a grinding fluid supply means to supply and a control means for performing grinding control based on a predetermined grinding program,
A dynamic pressure measuring step for measuring a dynamic pressure generated in the grinding fluid in a gap between the workpiece and the grinding wheel during rotation of the grinding wheel;
And a workpiece surface position fluctuation calculating step for calculating the position fluctuation of the workpiece surface based on the measured dynamic pressure fluctuation, which is a fluctuation of the dynamic pressure.

  A feature of the invention according to claim 2 is that, in the invention according to claim 1, the dynamic pressure measurement step is configured by a step of detecting a load fluctuation of a drive motor of the grinding wheel moving means.

  The invention according to claim 3 is characterized in that, in the invention according to claim 1 or 2, the rotation of the workpiece is stopped and the dynamic pressure fluctuation is measured, and the frequency having the maximum amplitude is measured by the workpiece support system. It is regarded as a natural frequency.

Feature of the invention according to claim 4 is the invention according to claim 1 or claim 2, calculates the radius variation of the workpiece outer circumference as a function of the dynamic pressure fluctuations in the work Monokai rolling, workpiece outer diameter shape Is to measure.

A feature of the invention according to claim 5 is a workpiece support means for supporting and rotating the cylindrical workpiece,
A grinding wheel support means for supporting the grinding wheel and rotating it with a driving device
A workpiece moving means for moving the workpiece support means;
Grinding wheel moving means for moving the grinding wheel support means;
Grinding fluid supply means for supplying the grinding fluid to the grinding action point;
Dynamic pressure measuring means for measuring the dynamic pressure generated in the grinding fluid in the gap between the workpiece and the grinding wheel during rotation of the grinding wheel by detecting the load of the drive motor of the grinding wheel moving means;
And a workpiece surface position fluctuation calculating means for calculating a fluctuation of the workpiece surface position based on the measured dynamic pressure fluctuation, which is a fluctuation of the dynamic pressure.

  According to the first and second aspects of the invention, the dynamic pressure that changes due to the fluctuation of the gap between the grinding wheel and the workpiece can be measured by detecting the load fluctuation of the drive motor of the grinding wheel moving means. The variation of the surface position of the workpiece can be measured from the measured value of the load variation by the workpiece surface position variation calculation process. The load fluctuation detection is a basic function of the grinding wheel moving means, and the work surface position fluctuation calculation is performed by adding a calculation program to the control means without adding a special device. Fluctuation measurement can be realized on-board at low cost.

  According to the invention which concerns on Claim 3, the natural frequency of the workpiece type | system | group including workpiece itself can be measured at low cost for a short time, without adding a special apparatus.

  According to the invention which concerns on Claim 4, the unevenness | corrugation of the surface of a workpiece can be measured in low cost in a short time, without adding a special apparatus.

  According to the invention which concerns on Claim 5, the natural frequency of the workpiece type | system | group including workpiece itself and the unevenness | corrugation of the surface of a workpiece can be measured in a short time at low cost, without adding a special apparatus. A board can be provided.

It is the schematic which shows the whole structure of the grinding machine of this embodiment. FIG. 2 is a cross-sectional arrow view of FIG. It is a conceptual diagram which shows the dynamic pressure generation | occurrence | production state of this embodiment. It is a graph which shows the relationship between the dynamic pressure of this embodiment, and the amount of gaps.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4 based on examples of cylindrical grinding machines.
As shown in FIGS. 1 and 2, the grinding machine 1 includes a bed 2, a grinding wheel base 3 supported on the bed 2 by a grinding wheel base feed 8 so as to be reciprocable in the X axis direction, and a Z orthogonal to the X axis. A table 4 capable of reciprocating in the axial direction is provided. The grinding wheel base 3 rotatably supports the grinding wheel 7, and the grinding wheel 7 is rotationally driven by a grinding wheel shaft rotating motor (not shown). A grinding wheel guard 13 is attached to the side surface of the grinding wheel base 3 so as to cover the grinding wheel 7. A grinding liquid nozzle 12 is installed on the front surface of the grindstone guard 13. On the table 4, a spindle 5 that grips and rotatably supports one end of the workpiece W and is rotationally driven by a spindle motor (not shown), and a center pusher that rotatably supports the other end of the workpiece W A workpiece 6 is provided, and the workpiece W is supported by the main shaft 5 and the tailstock 6 and is rotationally driven during grinding. A truing device 10 that rotatably supports a truing roll 9 that is rotationally driven by a truing motor 11 is attached to the main shaft 5.

  The grinding machine 1 includes a control device 30 that executes automated grinding and truing by executing a predetermined program. As a functional configuration of the control device 30, an X-axis control means 31 that controls the feed of the grindstone table 3, a Z-axis control means 32 that controls the feed of the table 4, a truing control means 33 that controls the truing device 10, and the spindle 5 A spindle control means 34 for controlling the rotation, a grindstone axis control means 35 for controlling the rotation of the grindstone 7, an arithmetic means 36 for calculating the workpiece surface position fluctuation value and fluctuation period from the dynamic pressure fluctuation value, and the like.

A method for measuring dynamic pressure in the grinding machine 1 will be described below.
While the grinding wheel 7 is rotated, the grinding wheel base 3 is advanced to a predetermined position while supplying the grinding fluid 20 from the grinding fluid nozzle 12, and the grinding wheel 7 is brought close to the workpiece W. The grinding fluid 20 passes through the gap between the grinding wheel 7 and the workpiece W and drops onto the bed 2 while following the grinding wheel 7. At this time, the grinding fluid 20 passes through a narrow wedge-shaped gap at a high speed, thereby generating a dynamic pressure as indicated by an arrow from the grinding wheel 7 to the workpiece W in FIG. As shown in FIG. 4, the relationship between the dynamic pressure, which is the product of the dynamic pressure and the area where the dynamic pressure acts, and the gap amount, the smaller the gap between the grinding wheel 7 and the workpiece W, the smaller the dynamic pressure. The dynamic pressure increases as the rotational speed of the grinding wheel 7 increases, the width of the contact portion between the grinding wheel 7 and the workpiece W increases, and the supply amount of the grinding fluid increases.
Due to the generation of dynamic pressure, forces in opposite directions act on the grinding wheel 7 and the workpiece W. This force is transmitted to the driving motor of the grinding wheel base feed 8 through the grinding wheel 7 and the grinding wheel base 3. The magnitude of the dynamic pressure can be measured by detecting the increase value of the drive current, which increases the drive current of the drive motor to generate a resistance force against the applied force, and performing a predetermined calculation.

The measurement of the natural frequency of the workpiece support system is performed as follows.
While the rotation of the workpiece W is stopped, the grindstone table 3 is advanced to a position where the dynamic pressure can be detected while supplying the grinding fluid 20, and then the grindstone table 3 is moved to a position where the grinding wheel 7 does not contact the workpiece W. After advancing rapidly, quickly retract to the original position. Due to this rapid back-and-forth movement, an impact force is applied to the workpiece, and the workpiece support system starts free vibration at the natural frequency of the system. The natural frequency of the workpiece support system is measured by measuring the period of the dynamic pressure fluctuation caused by the fluctuation of the gap due to this vibration. Specifically, the drive current flowing through the drive motor of the grindstone head feed 8 is detected, the detected current value fluctuation data is subjected to FFT analysis, and the frequency having the maximum amplitude is set as the natural frequency of the workpiece support system.
In the above embodiment, the rotation of the workpiece W is stopped. However, when the unevenness of the surface of the workpiece W is small, the natural frequency may be measured with the workpiece W rotated.
Here, if the surface position of the grinding wheel fluctuates, the dynamic pressure fluctuates even if the surface position of the workpiece is constant, and the vibration of the workpiece cannot be measured accurately. In order to prevent this, it is effective to make the surface position of the grinding wheel 7 constant at the contact position of the workpiece W by making the truing position of the grinding wheel 7 in phase with the contact position of the workpiece W. is there.

The unevenness on the surface of the workpiece W is measured as follows.
The table 4 is moved to a position where the measurement location of the workpiece W faces the grinding wheel 7. While the rotation of the workpiece W is stopped, the grindstone table 3 is advanced to a position where the dynamic pressure can be detected while supplying the grinding fluid. While rotating the workpiece W by the spindle 5, the dynamic pressure variations due to variations in the workpiece surface position from the rotation center for recording the rotation phase of the spindle 5. Assuming that the dynamic pressure fluctuation value is ΔP, the conversion coefficient is K, and the unevenness on the surface of the workpiece W is S, the dynamic pressure fluctuation value is converted into the unevenness on the surface of the workpiece W by S = K · ΔP. As the conversion coefficient K, a value obtained in advance by experimenting with the rotation speed of the predetermined grinding wheel 7, the width of the contact portion between the predetermined grinding wheel 7 and the workpiece W, and the supply amount of the predetermined grinding fluid is used.

<Deformation of this embodiment>
You may implement the measurement of dynamic pressure by measuring the force added to a grindstone axis.
The dynamic pressure may be measured by measuring the force applied to the workpiece. In this case, the sum of the force applied to the spindle and the force applied to the tailstock is used as the dynamic pressure.

W: Workpiece 3: Wheel head 4: Table 5: Spindle 6: Tailstock 7: Grinding wheel 8: Wheel head feed 9: Truing roll 10: Truing device 11: Truing motor 30: Control device

Claims (5)

A workpiece support means for supporting and rotating a cylindrical workpiece; a grinding wheel support means for supporting and rotating the grinding wheel by a driving device; and the workpiece for grinding the workpiece by the grinding wheel. Grinding control is performed based on a predetermined grinding program, a workpiece moving means for moving the support means, a grinding wheel moving means for moving the grinding wheel support means, a grinding fluid supply means for supplying a grinding fluid to the grinding action point, and In a grinding method using a grinding machine equipped with a control means,
A dynamic pressure measuring step for measuring a dynamic pressure generated in the grinding fluid in a gap between the workpiece and the grinding wheel during rotation of the grinding wheel;
A workpiece surface position fluctuation measuring method comprising a workpiece surface position fluctuation calculating step of calculating a position fluctuation of the workpiece surface based on a dynamic pressure fluctuation which is a fluctuation of the measured dynamic pressure. Constituting the hydrodynamic force measuring step in the process for detecting a load fluctuation of the drive motor of the grinding wheel movement means, work surface position variation measuring method according to claim 1.   The workpiece surface position variation according to claim 1 or 2, wherein the rotation of the workpiece is stopped, the dynamic pressure variation is measured, and the frequency having the maximum amplitude is regarded as the natural frequency of the workpiece support system. Measuring method. Calculates the radius variation of the workpiece outer circumference as a function of the dynamic pressure fluctuations in the work Monokai rolling, the workpiece outer diameter shape measurement, workpiece surface position variation measuring method according to claim 1 or claim 2. A workpiece support means for supporting and rotating the cylindrical workpiece;
A grinding wheel support means for supporting the grinding wheel and rotating it with a driving device
A workpiece moving means for moving the workpiece support means;
Grinding wheel moving means for moving the grinding wheel support means;
Grinding fluid supply means for supplying the grinding fluid to the grinding action point;
Dynamic pressure measuring means for measuring the dynamic pressure generated in the grinding fluid in the gap between the workpiece and the grinding wheel during rotation of the grinding wheel by detecting the load of the drive motor of the grinding wheel moving means;
A grinding machine provided with a workpiece surface position fluctuation calculating means for calculating a fluctuation of a workpiece surface position based on a dynamic pressure fluctuation which is a fluctuation of the measured dynamic pressure.

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