JPS625746B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an automatic measuring device that measures the relative positional relationship caused by thermal displacement of the main spindle and tool post of a numerically controlled lathe and corrects the amount of change. It is related to.

[Conventional technology]

In numerically controlled lathes, heat generated from the spindle bearing as the spindle rotates causes the spindle to displace in the spindle direction (Z), the spindle head in the direction perpendicular to the spindle (X), and the cutter to move. The position of the turret changes little by little during operation due to heat generated from the ball screw nut that drives the turret in the X and Z directions. As a result, the relative distance between the chuck end face of the spindle and the tool cutting edge of the tool rest changes. For this reason, an error due to thermal deformation occurs with respect to the machining dimensions instructed by the machining instruction tape, and the dimensional accuracy of the workpiece deteriorates. Especially after the primary processing of the workpiece,
This error becomes a problem when the workpiece is held upside down in the chuck and secondary processing is performed. That is,
As shown in Figure 1 (B), an item that was planned to be finished to a thickness of A according to the command from the numerical control device caused an error due to thermal displacement, and as shown in Figure 1 (B), the thickness was
The size will be A′. Therefore, it is necessary to measure the workpiece and correct the tool edge position based on the measurement results. Some measuring devices are driven independently, but numerically controlled lathes have relatively high-precision moving parts (digital drive parts), so it is ideal to use this. However, in general, in order to reduce the movement range of the machine, it is desirable to make the movement range of the measuring instrument as close as possible to the processing range required for measurement. For this reason, in many cases, a measuring device is attached in place of one tool on a tool post with multiple tools, and the workpiece is directly measured. However, this method has the following drawbacks.

The first is that the measuring instrument has electrical wiring for retrieving measurement results, so if the measuring instrument is attached to a tool post, there is no electrical connection mechanism or movable connection mechanism for the tool post to be indexed. Measures for moving cables connecting the stand and the fixed side are required, which is expensive.

Second, since measurement is performed directly between the measuring instrument and the workpiece, the workpiece must be cleaned, and the position of the measuring instrument or the measuring head must be replaced depending on the shape of the workpiece, which reduces versatility. Missing.

[Problem that the invention seeks to solve]

The present invention was developed in view of the above problem, and when machining on a numerically controlled lathe is completed, the distance between the tool rest positioned at a specific measurement position and the reference surface of the chuck is measured based on a command from the numerical control. This method attempts to improve machining accuracy by comparing the current measurement value with the previous measurement value and correcting the difference.

[Means for solving problems and their effects]

The present invention provides an operating piece on a movable part such as a tool post of an automatic lathe, etc., and a measuring device is provided on the spindle head, which has relatively little thermal displacement, so as to be movable so as to come into contact with the reference surface of the chuck. By moving the measuring device by a certain amount and activating the actuating piece, it is intended to measure the change in the measured value due to the movement of the measuring device by a certain amount with respect to the reference surface of the chuck. Therefore, the actuating piece 9 of the tool rest 8 engages with the engaging portion of the main body 12, and is always pulled out by a certain amount, so that the contact of the measuring device 11 comes into contact with the chuck back reference surface. The amount of movement at this time is a constant amount each time based on numerical control commands. Therefore, the error between the value measured by the measuring device before machining and the value measured by the measuring device when the main spindle undergoes thermal displacement after several machining operations becomes the value to be corrected.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, a spindle head 1 rotatably supporting a spindle 2 is mounted on the left end of the bed 5. A chuck 3 having a reference surface 3a on the back is attached to the end face of the main shaft 2, and the chuck grips the workpiece W via a claw. Further, a guide surface 5a is provided on the bed 5 in parallel to the main shaft 2, and a saddle 6 is mounted on the guide surface so as to be slidable in the Z direction. The saddle is numerically driven and controlled by a servo motor and a ball screw mounted on the bed 5. A sliding surface 6a is formed in the upper part of the saddle 6 in a direction perpendicular to the main shaft axis, and a cross slide 7 is mounted on the sliding surface so as to be slidable in the X direction. The cross slide is numerically driven and controlled by a servo motor and a ball screw provided on the saddle 6. A tool rest 8 having a freely indexable turret head 8a is mounted on the cross slide 7. On the tool mounting surface of the turret head 8a, an operating piece 9 having a constant length and having a reference surface for operating a measuring device to be described later in place of the tool is attached. This actuating piece is constantly cleaned with coolant and is not affected by chips. Further, a rod 10 is provided in the spindle axial direction on the front surface of the spindle head 1, which is close to the processing area and is relatively less affected by heat, within a range where the turret head 8a described later is numerically controlled by the drive of the motor. A measuring instrument mounting body 12 is provided on the rod so as to be slidable in the Z direction, and a spring 13 is inserted between the rod 10 and the body 12 to normally press the body 12 toward the main shaft. Further, a measuring device 11 such as a differential transformer or the like composed of a coil and a contactor is attached to the main body 12 so as to face the chuck reference plane, and the tip of the main body 12 is connected to the actuating piece 9. A joint portion 12a is provided. The main body 12 and the chuck 3 are covered with a cover 14 attached to the front surface of the spindle head 1.
In particular, the joints between the cover 14 and the outer periphery of the chuck 3 and between the cover 14 and the tip of the main body 12 are designed to have a simple shape, and are designed to prevent chips from entering inside using a well-known labyrinth or other means. has been done.

The operation of the automatic measuring device according to the present invention will be explained below.

As the workpiece is machined, the length from the spindle bearing to the end surface of the workpiece may change due to the heat of the spindle 2 bearing or the heat during cutting, or the length from the spindle bearing to the end surface of the workpiece may change due to heat from the ball screw. This causes a change in the position of the turret. In this state, the turret 8 is numerically driven and controlled according to the tape positioning command, and the actuating piece 9 of the turret head 8a of the turret 8 is moved from point I in FIG.
The actuating piece 9 engages the main body 12 at this point, and is further moved by a certain amount to the point E for measurement, so that the main body 12 is moved as indicated by the two-dot chain line in FIG. moved to position. During this time, measuring device 1
The contact 1 remains on the back reference surface of the chuck 3, and the coil side of the measuring device 11 moves relatively. The mounting part of the measuring instrument 11 is a place where there is relatively little heat influence, so
Measuring instruments are considered absolute positions. An output voltage is generated from the measuring device 11 due to the relative movement. This output voltage is connected to the A/
The signal passes through the D converter 16 and becomes a digital signal. This digital signal enters the first register 17 as data. The data entered in the first register maintains this state until the next measurement. Next, after processing, when measurement is performed in the same manner as described above, the digital signal from the measuring device 11 passes through the A/D converter and enters the first register 17. At the same time, the value before processing in the first register 17 is shifted to the second register 18. At the same time as this shift is completed, both enter operation 19,
The next measured value is subtracted from the first measured value to obtain that value (correction amount). Next, when the tape is started and a correction command is issued as the next tape command, the correction amount in the arithmetic circuit is written into the memory in the correction control circuit of the numerical control device 20. The tape is activated with this memory write completion signal and processing begins again.

The above operations are repeated to machine the workpiece while reducing the mutual error between the spindle end and the tool post turret caused by thermal displacement of the spindle bearing or ball screw.

The above explanation deals with the case of correcting thermal deformation in the direction of the spindle axis (Z direction) of a lathe, but in the second embodiment shown in FIG. An example will be shown in which thermal deformation is corrected. That is, the second embodiment provides an automatic measuring device that relatively measures the elongation of the spindle head from the mounting position of the measuring instrument to the center of the spindle and the displacement of the tool rest due to the ball screw in the X-axis direction.

The configuration of the numerically controlled machine tool in the first embodiment is exactly the same, and the other components have the same functions. These same items are all given the same number.

In the second embodiment, the outer periphery of the chuck 3 is used as a reference surface, and the movement of the tool rest 8 in the X-axis direction is used to move the cutout reference surface of the actuating piece 9 in the direction of the arrow in FIG. Push the rear part of the mounting body 12 by a certain amount.

The main body 12 moves toward the chuck reference plane against a spring on a rod attached to a portion of the spindle head 1 that is less affected by heat. During this time, measuring device 1
The first contact remains on the chuck outer circumferential reference surface, and the coil side of the measuring device 11 moves relatively. This relative movement causes the measuring device 11 to generate an output voltage. After this, the same digital processing as in the first embodiment,
Calculation processing is performed to find the correction amount.

Although this example uses a simple hook mechanism,
It is also possible to use a hook-and-pinion mechanism in which the actuating piece pushes the rack and operates the measuring rack via the pinion. Further, although the present invention utilizes the movement of the tool rest, the measuring instrument 11 may be moved relative to the chuck simply by using a cylinder without using the tool rest, and the thermal deformation of the main shaft may be measured. As described above, modifications of the present invention are expected without departing from the technical idea of the present invention as described in the claims.

〔Effect of the invention〕

Therefore, since the operating piece of the movable part only operates the measuring instrument, no wiring or the like is required. In addition, the reference surface to be measured is between the chuck and the turret, which have the most influence on the machining of the workpiece, and since the measurement is performed inside the cover, the actual machining error can be measured regardless of chips. be able to.

[Brief explanation of the drawing]

Figure 1 A and B are explanatory diagrams of the influence of thermal deformation of the lathe on the workpiece, Figure 2 is a plan view of a lathe equipped with the automatic measuring device of the present invention, and Figure 3 is the automatic measuring device of the present invention. FIG. 3 is a plan view showing another embodiment of a lathe equipped with the following. In the figure, 8...turret, 9...actuating piece, 1
0... Rod, 11... Measuring device, 12... Measuring device mounting body, 13... Spring, 14... Cover, 15... Cable, 16... A/D converter,
17...first register, 18...second register,
19... Arithmetic circuit, 20... Numerical control device.

Claims (1)

[Claims] 1. In an automatic lathe, a spindle head rotatably supports the spindle, a workpiece gripping chuck attached to the end of the spindle and having a reference surface for measurement on the back surface or outer circumference, and a relative heat exchanger near the spindle. An actuated device is installed on a fixed part with little influence and is movable forward and backward in a direction perpendicular to a chuck measurement reference plane, and the chuck is measured by the movement of the actuated device. a measuring device mounted at an opposing position to come into contact with a reference surface for the tool; and a tool rest having a turret head that is movable relative to the spindle in a direction parallel to the spindle axis and in a direction perpendicular to the spindle axis. an actuating piece that is mounted on the turret head of the tool post and moves into engagement with the actuated device as the tool post moves and brings the measuring device into contact with a measuring reference surface of the chuck; Consists of a cover that covers the reference surface,
When the actuating piece moves the actuated device by moving the turret to the measuring point and the measuring device comes into contact with the measuring reference surface of the chuck, the change in distance between the measuring point of the tool post and the measuring reference surface of the chuck is detected. An automatic measuring device characterized by measuring.