JPH0436829B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting thermal displacement of an NC grinding machine, and more specifically, it corrects the influence of thermal displacement of the wheel head, column, etc. in a so-called overhead type NC grinding machine, This makes it possible to perform highly accurate grinding.

In grinding machine forming machines that use surface grinders, spline grinders, etc. to perform form-grinding, numerical control program drive methods, or NC forming methods, have recently replaced the conventional template copying method as a method for forming free-form surfaces. is being put into practical use.

As shown in Fig. 1, the wheel forming device uses a diamond tool 3, which has the outer circumferential surface of a wheel 2 attached to a rotating shaft 1 and placed on the grinding blade surface, to move left and right (X-axis direction) and back and forth (Y-axis). direction) and tip R accuracy and to avoid interference with the grinding wheel 2, it performs rotational drive around the Z axis (C direction), and is controlled according to a numerical control program, that is, NC
The grinding wheel is controlled to form the outer circumferential surface of the grinding wheel into a predetermined shape.

By the way, there are two ways to install the wheel forming device on a grinding machine:
There is a way to attach it to the grinding head. Comparing these, in terms of efficiency and molding accuracy,
The latter method, that is, the overhead type, is superior because the grinding wheel can be formed during the grinding cycle, and the mutual positional relationship between the grinding device and the grinding wheel is fixed.

However, on the other hand, this overhead type NC milling machine had the following problems due to the fact that it was attached to the milling head. In other words, heat generated during grinding operations causes thermal displacements such as elongation of the grinding head and tilting of the column back and forth, and naturally there is a relative relationship between the wheel forming device attached to the grinding head and the table of the grinding machine. A displacement occurs. Then, even if the grinding wheel is formed into a predetermined shape using the NC program, the relative position between the grinding wheel (strictly speaking, the formed shape of the grinding wheel) and the workpiece will shift, and the grinding accuracy of the workpiece (the grinding shape of the workpiece will be affected). This results in a decrease in the positional accuracy (positional accuracy).

In addition, in the method in which the wheel forming device is installed on the table, even if the relative position between the grinding wheel and the workpiece changes due to thermal displacement of the column or the grinding head, the relative position between the wheel forming device and the workpiece remains unchanged. No deviation occurs.
Therefore, by being formed by the forming device, the grinding wheel has an appropriate shape that maintains positional accuracy regardless of thermal displacement, and the above-mentioned problems do not occur.

In addition, the wear of the grinding wheel due to molding is
This is canceled using existing technology that corrects the depth of cut of the grinding wheel into the workpiece based on the depth of cut of the diamond roots.

The present invention corrects the relative displacement between the table and the wheel forming device due to thermal displacement of the column or the wheel head of the overhead type NC wheel forming device, thereby correctly correcting the relative position between the wheel and the workpiece. It is an object of the present invention to provide a thermal displacement correction method that maintains and improves grinding accuracy.

A thermal displacement correction method according to the present invention for achieving the above-mentioned object is an NC grinding machine in which a wheel forming device is attached to the wheel head, and a workpiece is controlled by a sensor attached to the wheel forming device. The present invention is characterized in that a reference position on the table to be placed is measured, and the coordinate system of the NC program of the wheel forming apparatus is corrected based on the measurement result.

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 2 shows the main structure of an NC grinding machine using the method of the present invention, in which FIG. 2A is a plan view, FIG. 2B is a front view, and FIG. 2C is a side view.

As shown in FIG. 2, the wheel 2 for grinding the workpiece 17 on the table 18 is pivotally supported by a grinding wheel head 5, and the grinding wheel head 5 is erected close to the table 18 on which the workpiece 17 is placed. It is attached to the front surface of the column 4 that is vertically slidable. A wheel forming device is attached to the upper part of this wheel head 5.

The forming head 6 of the wheel forming device is supported by an X-axis slide 8 and is movable in the X-axis direction by an X-axis drive motor 9, and the X-axis slide 8 is mounted on a Y-axis slide 10 and driven by the Y-axis. It is movable in the Y-axis direction by a motor 11. This Y-axis slide 10
It is supported on a base 7 provided on the upper part of the grinding wheel head 5, and therefore the forming head 6 is movable in the X-axis direction and the Y-axis direction with respect to the grinding wheel head 5.

In addition, the forming head 6 has an arm 12 that extends in the vertical direction (Z-axis direction) and has a diamond tool 3 attached to its tip, and the top arm 12 is rotated around the Z-axis by a C-axis drive motor 13. It is now possible to move. Therefore, by rotating this arm 12, the diamond tool 3 can be tilted at an arbitrary angle with respect to the circumferential surface of the grinding wheel 2.

Here, in order to drive the wheel forming device with an NC program, an NC program drive device (not shown) is used.
A drive signal is sent to the X-axis drive motor 9, Y-axis drive motor 11, and C-axis drive motor 13 of the molding device.

Furthermore, a measuring unit 14 is fixed to the side surface of the molding head 6. The measuring unit 14 has a measuring arm 16 that can be moved up and down by a drive motor (not shown), and a touch sensor 15 is attached to the tip of the measuring arm 16.

On the other hand, on the table 18 to which the workpiece 17 is fixed, a reference block 19, which serves as a reference position on the table 18, is fixed at the end position of the grinding stroke.

In the above-mentioned NC grinding machine, first the table 18
A workpiece 17 is fixed on top of the reference block 19 in a predetermined positional relationship. On the other hand, the position of the reference block 19 on the X-axis of the forming device is measured in advance by the touch sensor 15, and the data is inputted to the NC program drive device as a reference setting value, and the coordinate settings for grinding are determined. conduct.

Next, if the grinding device is to be used during the grinding operation, the table 18 is stopped at the end of the grinding stroke, and the measuring arm 16 of the forming device is lowered to the reference block position 15. Then, the X-axis drive motor 9 is driven to move the X-axis slide 8, and the touch sensor 15 at the tip of the measurement arm 16 is set to the reference block 1.
The current position of the X-axis slide 8 at the moment of contact with the X-axis slide 8 is read using, for example, an induction scale. Next, this measured value is compared with the reference set value, and the X-axis coordinate system of the NC program drive device is shifted by the difference. Note that this calculation and coordinate shift operation are performed by the data processing function of the NC device. After the measurement described above, the measuring arm 16 is raised and stored in the measuring unit 14. These series of operations are programmed into the machine control device as an automatic sequence.

Subsequently, while the table 18 is returned to the grinding work starting position, the grinding wheel 2 is formed according to a predetermined NC program using the corrected coordinate system.

Note that the NC program for the above-described correction operation does not necessarily need to be executed every time the wheel is formed. This is because thermal deformation of large structures such as the column 4 and grinding head 5 of the grinding machine progresses relatively slowly. Therefore, it is particularly efficient to carry out the process during grinding in final finish grinding, which requires high precision.

As described above in detail with reference to embodiments, according to the present invention, in an NC grinding machine having a so-called overhead type wheel forming device, the NC grinding machine of the wheel forming device is By correcting the coordinate system of the program, it becomes possible to perform highly accurate grinding.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the principle of the wheel forming method, Figure 2
The figures show the main structure of an NC grinding machine using the method of the present invention, in which figure a is a plan view, figure b is a front view, and figure c is a side view. In the drawing, 2 is a grindstone, 3 is a diamond tool, 4 is a column, 5 is a grinding head, 6 is a forming head of a grinding machine, 8 is an X-axis slide, 9 is a Y-axis slide, and 10 is an X-axis drive motor. , 11 Y-axis drive motor, 12 arm, 13 C-axis drive motor, 14
1 is a measurement unit, 15 is a touch sensor, 16 is a measurement arm, 18 is a table, and 19 is a reference block.

Claims (1)

[Claims] 1 The wheel forming device is attached to the wheel head.
In the NC grinding machine, a sensor attached to the wheel forming device measures the reference position on the table on which the work is placed, and based on this measurement result, the coordinate system of the NC program of the wheel forming device is determined. A thermal displacement correction method characterized by: