JPH01216751A - Method for detecting center of rotary shaft - Google Patents

Abstract

PURPOSE:To detect the center of a main spindle simply and rapidly on a machine by moving a noncontact displacement meter faced to a steel ball installed on a rotary shaft in two directions perpendicularly to the rotary shaft and detecting the least varying position of its output as the center of the rotary shaft. CONSTITUTION:A preparatory member 15 in which a semispherical steel ball 5 is eccentrically embedded in the vicinity of the center of the chuck 3 of a main spindle 1 is held by a chuck claw 4, a noncontact displacement meter 12 installed on the upper base 7 of a tool rest is brought close to the steel ball 5 while rotating the main spindle 1, the tool rest is moved in the X direction watching the output of the displace ment meter 12, and the tool rest is stopped in the position of detecting the minimum position of the varying width of the output. Then, the tool rest is moved in the Y direction and stopped at the time of equally detecting the minimum width of the output. This position is determined to be the rotation center of the main spindle 1 and a tool 14 is faced to the main spindle 1 side in the center position of the displace ment meter 2 based on the difference in the known heights of the displacement meter 12 and a cutting edge to carry out the cutting of a workpiece held by the chuck 3 by NC, thereby enabling the cutting of a nonspherical lens, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the axis center of a main spindle or a rotating shaft of an industrial machine during machining of a precision lathe.

Conventional technology When performing ultra-precision machining, such as machining an aspherical lens, using a conventional lathe, it is important to match the center of the spindle with the center height of the tool tip, and it is not easy to determine whether the two match. Therefore, trial cutting was performed to evaluate the shape accuracy of the workpiece.

Problems that the invention aims to solve Test-cutting a workpiece requires careful work and takes a long time, and it is necessary to remove the workpiece, measure it again on the measuring machine stand, calculate the error, adjust the position, and then cut it again. This has the problem of requiring preparation time before starting regular machining, which is troublesome and reduces work efficiency.

The present invention does not require trial cutting and can be easily performed on a machine.

The purpose of this invention is to provide a method that can quickly detect the center of the spindle.

Means for Solving the Problems A rotating shaft with a steel ball attached near the center of the tip is rotated, and a non-contact displacement meter attached to a movable table facing the steel ball is moved in two directions perpendicular to the rotating shaft. The non-contact type displacement meter is moved to detect the minimum variation position of the output in the two directions with respect to the rotation axis.

A steel ball is attached to the center of the end face of the operating rotation shaft, such as the main shaft, and rotated. A non-contact displacement meter attached to a moving platform that moves in two directions of the x and y axes perpendicular to the main axis is first moved in the x-axis direction to the position of minimum detection output, then moved to the y-axis direction to the position of minimum detection output. Stop the platform. The displacement meter position at this position is the center of the main shaft.

Embodiment Although the turret on the saddle in this embodiment is expressed in an experimental manner, it will be specifically described in order to make the intention of the present invention clear in practice.

In a well-known NC precision lathe, a headstock 2 rotatably supporting a main spindle 1 is placed on a two-axis direction guide surface of a bed so that it can be positioned using the NC, and a gripping device such as a vacuum chuck 3 is attached to the front end of the main spindle 1. is fitted. A set-up 15 in which a semi-cooked food 5 is intentionally buried slightly eccentrically in the center where it does not interfere with the chuck jaws 4 is held by the chuck jaws 4.

On the other hand, a saddle 6 is placed on the main inner surface of the bed in the X-axis direction so as to be movable in the X-axis direction, and its positioning is controlled by an NC. saddle 6
A tool rest is provided on the top so that it can be rotated and positioned, and this tool rest is fixed on an upper stand 7 having a tool mounting groove 7a in the Z-axis direction and a flat lower surface 7b, and an index stand (not shown) on the saddle 6. The upper surface 8a is a sloped surface, and the lower surface 8 is a sloped surface.
A wedge body 9 is interposed between b and the upper surface 8a, and as this wedge body 9 is advanced and retreated by a bolt lO, the upper stand 7 is moved only in the vertical direction while being sandwiched between the guides 18b.

The wedge body 9 is urged by a spring 11 to 4i'e without backlash of the screw. Although not shown, the lower stand 8 partially covers the upper part of the upper stand 7, and acts to constantly press the lower surface 7b of the base against the wedge body 9 by the force of a strong spring.

In the tool mounting groove 7a of the upper stand 7, a non-contact displacement gauge 12 is fixed with a pin 13 facing the main shaft 1, and a tool 14 is fixed with a pin 13 on the opposite side. The output of the displacement meter 12 is amplified by an amplifier 16 and input to the display. and tool 1
The difference between the heights of the four cutting edges and the center height of the displacement meter 12 is measured in advance. Since the steel ball 5 is mounted eccentrically with respect to the center of rotation of the main shaft, the center locus of the steel ball 5 forms a circle whose radius is the amount of eccentricity, as shown in FIG. When the displacement meter 12 is moved in the direction of the arrow at a position away from the center of the spindle, the distance between the apex of the steel ball 5 and the ball surface at the (1) and (In) positions of the displacement meter 12 is as shown in Fig. 3. j, , j, the output of the displacement meter 12 also changes. When the main shaft l is rotated in this state, the distance jil tt t changes in proportion to the amount of eccentricity due to the eccentricity of the steel ball 5 at the position where the displacement meter 12 is located.

In addition, the output similarly fluctuates at position (II), but because it is close to the center of the steel ball 5! , the fluctuation is smaller compared to .

Therefore, the position of the center of rotation of the steel ball 5 measured by the displacement meter 12 becomes the smallest when the output is fluctuating. That is, this is clearly seen in FIG. 4, which shows the displacement in the X-axis direction. According to the same principle, the position of the minimum displacement fluctuation in the Y-axis direction becomes the center of rotation of the steel ball, so if you bring out the center in the X-axis direction and then the center in the Y-axis direction, the position of zero fluctuation width will be the main axis as shown in Figure 5. Become the center.

In FIG. 6 of the flowchart of the center detection method, in step S1, the chuck claw 4 grips the setup 15 in which the semi-cooked material 5 is eccentrically buried near the center of the chuck 3 of the main shaft. In step s2, the displacement meter 12 attached to the upper stand 7 of the tool rest is brought close to the steel ball 5, and if necessary, the main shaft is rotated to check the output state. In step S3, the main axis l
In step s4 of rotating the tool post, the tool rest is moved in the X-axis direction while observing the output of the displacement meter 12. In step S5, the process from step S4 is repeated until the minimum position during output fluctuation is detected, and the tool rest is stopped at the detected position.

In step S6, the tool rest is moved in the seven wheel (height) direction. In step S7, the process from step s6 is repeated to detect the minimum output, and when detected, the process is stopped.

In step S8, the upper stand 7 is positioned so that the height of the tool matches the center position of the displacement meter based on the known height difference between the displacement meter and the cutting edge.

The tool on the positioned tool rest is moved toward the spindle side, and the workpiece gripped by the chuck is cut using the NC@111 to cut an aspherical lens or the like.

Although this embodiment has been described with reference to the main shaft and tool rest of a lathe, the present invention is not limited to this; it can be similarly applied to detecting the center position of any machine.

Furthermore, it is also possible to calculate the output of the displacement meter within the NC device, find the minimum fluctuation point, and automate positioning by X- and Y-axis control.

Effects As detailed above, the present invention can detect the center of the spindle on the machine and accurately align the tool on the turret with the center, greatly improving machining accuracy even in special machining such as aspherical lenses. can be improved. Moreover, there is an effect that center detection can be performed extremely easily in a short period of time.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the present invention, Figure 2 is a diagram showing the positional relationship between the locus of the center of the steel ball and the plane of the displacement meter, Figure 3 is a diagram showing the positional relationship of the height, and Figure 4 5 is a diagram showing a state in which the output of the displacement meter in the X-axis direction is fluctuating, FIG. 5 is a diagram showing a state in which the output of the displacement meter in the X-axis direction is fluctuating, and FIG. 6 is a flowchart for detecting the center of the rotation axis. l...Main shaft 5...Steel ball 7...Upper stand 8...Lower stand
9. Wedge

Claims (1)

[Claims] (1) Rotate a rotating shaft with a steel ball attached near the center of the tip, move a non-contact displacement meter attached to a moving table facing the steel ball in two directions perpendicular to the rotating shaft, and A method for detecting the center of a rotating shaft, characterized in that the position of minimum variation in the output in the two directions of the contact displacement meter is detected as the center of the rotating shaft.