JPH06246589A - Noncircular workpiece error correcting method by in-machine measurement - Google Patents

Abstract

PURPOSE:To provide a method of correcting an error by measuring a noncircular workpiece, machined by an NC lathe, on a machine. CONSTITUTION:A noncircular workpiece W is cut according to a machining program with built-in noncircular shape data, and a contact sensor (touch sensor) 8A fitted to a turret 7 is indexed into a machining position. The positions of an X-axis at the time of touch signals being outputted by the advance of a tool rest 3 every time a C-axis is indexed pitch by pitch in regular succession from an origin are detected by a position detector 6 to prepare measured data. The measured data is stored and compared with the shape data to obtain a shape error. At the time of being the allowable value or more, the shape error is stored as the correction value data, and the moving position of the tool rest 3 at the generating machining time is corrected to offset the error part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a machining error when creating a non-circular work such as a cam in an NC lathe.

[0002]

2. Description of the Related Art Conventionally, a non-circular workpiece such as a cam in an NC lathe is created by a machining program in which a rotation angle of a spindle 101 and an X-axis position of a tool rest 102 are incorporated in a machining program as shown in FIG. Processing is performed by synchronous control based on data (lift data). In such a generating method, since the tool post 102 reciprocates at least once in the X axis direction with respect to the rotation of the spindle, the tool post 102 moves in the X axis in the saddle 103.
Even if control is performed according to the shape data between the turret and the turret, the bed is forced by the mass and acceleration of the reciprocating turret to generate vibration. FIG. 7 is a graph showing the relative vibration between the headstock and the saddle, which is obtained based on the vibration measurement values measured by the sensor 104 attached to the point a of the headstock and the sensor 105 attached to the point b of the saddle. FIG. 8 is a graph in which the upper side represents the vibrations of the headstock and the saddle, and the lower side represents the relative vibrations.

FIGS. 9 and 10 are graphs showing the shape error generated in the work by such relative vibration. In order to reduce this kind of error, there is no way to reduce the weight of the tool rest or reduce the vibration by reducing the speed, but there is a limit in both and it is difficult to reduce the machining error. Therefore, the procedure for manually inputting the shape error measured by the shape measuring instrument located at a remote place such as the temperature-controlled room to correct the processed shape data and re-processing is repeated several times until the target accuracy is obtained.

[0004]

According to the error correction method described in the prior art, the created work is carried to the shape measuring device at a remote place to measure the shape error, and the processed shape data is corrected manually. It has a problem that it is a waste of time and labor. The present invention has been made in view of the above problems of the conventional technique, and the purpose thereof is to obtain a shape error in a processing site and perform correction to obtain a processing accuracy close to the input shape data. The present invention intends to provide an error correction method that can achieve this.

[0005]

In order to achieve the above object, an error correction method for non-circular workpieces by in-machine measurement according to the present invention is a reciprocating motion of a tool post in the X-axis direction at the time of non-circular workpiece creation processing by an NC lathe. A method for correcting a machining error caused by relative vibration between a spindle and a tool rest by a contact sensor attached to the tool rest every time a non-circular work piece machined by shape data stored in advance is indexed by a predetermined pitch. When the X-axis position of the tool rest is read, measurement data is created and the shape error is calculated by comparing the measurement data with the shape data. When it is large, the shape data is corrected using the shape error as a correction value.

A method for correcting a machining error caused by relative vibration between the spindle and the tool rest due to reciprocating motion of the tool rest in the X-axis direction when creating a non-circular workpiece by an NC lathe, and using shape data stored in advance. The machined non-circular work is rotated at low speed, and the non-contact sensor attached to the tool rest that is operated synchronously with the spindle based on the shape data continuously measures the amount of change in the X-axis gap with the work to directly shape the shape. An error is obtained, and when the obtained shape error is larger than a previously stored allowable value, the shape data is corrected using the shape error as a correction value.

A method of correcting a machining error caused by relative vibration between the spindle and the tool rest due to reciprocating motion of the tool rest in the X-axis direction when creating a non-circular work by an NC lathe, and at the same speed as during machining. With the shape data, the spindle and the turret are operated synchronously, and the amount of change in the X-axis gap between the spindle and the concentric reference circular ring is continuously measured by the non-contact sensor attached to the turret. Forming data, calculating the shape error by comparing the measured data with the shape data, and correcting the shape data by using the shape error as a correction value when the obtained shape error is larger than an allowable value stored in advance. .

[0008]

According to the first aspect of the present invention, the non-circular work after the creation processing is compared with the shape data of the measurement data measured by the contact sensor such as a touch sensor on the machine. When the obtained shape error is equal to or more than the allowable value, the shape error is detected. Correction is performed as a correction value. According to a second aspect, the non-circular work that has been subjected to the creation processing is measured for the amount of gap change by a non-contact sensor for length measurement using a laser beam or the like during low-speed synchronous operation on the machine. When the value is equal to or more than the allowable value, the shape error is corrected using the correction value. According to a third aspect of the present invention, a reference circular ring provided concentrically with the spindle is used to measure the amount of gap change by a non-contact sensor requiring length measurement during synchronous operation at the same speed as during machining, and the obtained measurement data is used as shape data. The shape error is obtained by comparison, and when the shape error is equal to or larger than the allowable value, the shape error is corrected using the correction value data.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS This embodiment will be described below with reference to the drawings. First Embodiment In the NC lathe shown in FIG. 1, a saddle 2 is movably mounted on a Z-axis direction guide (not shown) provided on a bed 1, and the saddle 2 is provided on the saddle 2 in the X-axis direction. The tool rest 3 is movably mounted on the guide. The tool rest 3 is moved and positioned by a X-axis servomotor 4 fixed to the saddle 2 via a ball screw 5, and a linear position detector 6 for detecting the X-axis position is provided in parallel with the X-axis guide. The turret 7 is provided with a turret 7 that can be swivel-indexed around a swivel center axis in the Z-axis direction.
A tool T and a non-contact sensor (touch sensor) 8A are attached to the tool attachment station on the outer periphery. On the other hand, a spindle is rotatably supported by a spindle stock 9, and the spindle is rotated by a C-axis servomotor 10 to hold a non-circular work (cam) W by a chuck at the tip of the spindle.

The block diagram portion of FIG. 1 is a servo system for generating the cam W. The shape data storage unit 11 is a portion that stores the lift amount of the cam W per predetermined turning angle. The program storage unit 12 is a unit that stores a machining program that incorporates shape data. The program interpretation unit 13 is a unit that interprets a machining program and sorts commands. The position control unit 14 is a part that performs position control according to a command. The C-axis drive unit 15 and the X-axis drive unit 16 include a C-axis servo motor 10 and an X-axis servo motor 4, respectively.
11 to 16 are the same as the conventional ones. Measurement data storage unit 17
Is a portion that detects the X-axis position of the tool rest 3 when a touch signal is output from the touch sensor 8 and stores the measurement data of the X-axis position corresponding to the spindle rotation angle. The shape error calculation and storage unit 18 is a unit that compares the measurement data with the shape data to obtain the shape error and stores the shape error. The error allowance storage unit 19 is a unit that stores an error allowance input in advance. The error comparison unit 20 compares the shape error with the allowable value, and outputs the shape error as a correction value when the error is equal to or larger than the allowable value. The correction value data setting unit and the storage unit 21 is a storage unit that stores an error value corresponding to the spindle turning angle as correction value data.

Next, the first operation of this embodiment will be described with reference to the flow chart of FIG. In step S1, the material is held by the spindle chuck, and the non-circular work W is created based on the shape data. In step S2, the turret 7 of the tool rest 3 is rotated to index the touch sensor 8 to the processing position. Next, after indexing the C-axis to the origin, in step S3 the tool rest 3 is moved to the workpiece W side in the X-axis direction,
In step S4, it is confirmed whether the touch sensor 8 comes into contact with the surface of the work and a touch signal is output. And N
If O, the process returns to step S4, and if YES, in step S6, the X-axis position of the tool post 3 when the touch signal is output is read from the linear position detector 6, and the tool post 3 is read.
Is slightly moved to the work side opposite to the X-axis, and touch sensor 8
Away from the work W.

Next, in step S7, the tool rest 3 is slightly moved to the side opposite to the work, and then the C axis is indexed by one pitch and the X axis position is read by the touch sensor 8.
In step S8, it is confirmed whether or not the vehicle has turned 360 °. If NO, the process returns to step S4, YES
In the case of, the measurement data of the X-axis position corresponding to the C-axis indexing angle is stored in step S9, the shape error is calculated by comparing the measurement data with the shape data in step S10, and stored in advance in step S11. The allowable value of the error to be made is compared with the shape error, and it is confirmed whether it is within the allowable value. If NO, the shape error is stored as correction value data in step S12, the X-axis coordinate value of the shape data is corrected by the correction value data, and the work is reworked in step S13. When it is returned and YES in step S11, the process ends. Finally, the corrected correction value data is stored and the actual cutting process is started.

Second Embodiment The second embodiment in FIG. 1 is different from the first embodiment only in that a non-contact sensor 8B for measuring a distance by a laser beam or the like is attached in place of the touch sensor 8A, and the others are the same. It is the same. The second operation of the embodiment will be described with reference to the flowchart of FIG. In step S21, the non-circular work held by the spindle chuck is machined according to the shape data, the non-contact sensor 8B of the tool rest 3 is indexed to the machining position in step S22, and the C axis is indexed to the origin in step S23. .

Next, in step S24, the tool rest 3 is moved forward in the X-axis direction so that a predetermined gap is formed between the workpiece surface processed by the non-contact sensor and the spindle (workpiece) is rotated at low speed in step S25. The tool post is synchronously moved by the shape data, and the amount of change in the gap in the X-axis direction is continuously measured. In step S26, it is confirmed whether the C-axis has rotated 360 °. If NO, the process returns to step S24, and if YES, the amount of change in the gap corresponding to the turning angle is stored as a shape error in step S27, and it is confirmed in step S28 whether the shape error is within an allowable value. To be done. If NO, step S29
In step S30, the shape error is stored as correction value data, and in step S30, the correction is performed to rework the non-circular work, and the process returns to step S22. If YES in step S28, the process ends.

Third Embodiment In FIG. 4, the only difference from the first embodiment is that a reference perfect circular ring 23 is concentrically fitted to the tip of the main shaft 22, and the tool rest 3 is provided with the second embodiment. A non-contact sensor 8B similar to the above is attached, and the others are the same. The third operation of the third embodiment will be described with reference to the flowchart of FIG. In step S31, the non-contact sensor 8B of the tool post 3 is indexed to the processing position, and in step S32, the tool post 3 is moved until the non-contact sensor 8B and the tool post 3 form a predetermined gap.
Move axially forward. Next, in step S33, the spindle 22 is rotated at the same speed as during machining, and the tool post 3 is synchronously operated based on the shape data to continuously measure the amount of change in the clearance.

Next, in step S34, it is confirmed whether the C-axis has rotated a predetermined amount. If NO, the process returns to step S33, and if YES, step S35.
In step 1, the average value of the measured values for the same turning angle measured during a predetermined rotation is obtained to generate measurement data for one rotation, the measurement data is compared with the shape data, and the shape error is calculated and stored. Next, in step S36, it is confirmed whether the shape error is within the allowable value. If NO, the shape error is stored as correction value data in step S37, the correction is performed in step S38, and the amount of change in the gap is continuously measured again, the process returns to step S34, and YES is obtained in step S36. If finished. Note that X
The axial position is not limited to being detected by the linear position detector, and a rotary encoder fixed to the X-axis servo motor may be used as long as machining accuracy is allowed.

[0017]

Since the present invention is configured as described above, it has the following effects. The in-machine measurement was performed to find and correct the shape error caused by the relative displacement between the main spindle and the tool due to the reciprocating motion of the tool post during creation processing, and the error was canceled out, so the error can be easily corrected at the work site. This makes it possible to eliminate the trouble of carrying the workpiece to a remote measuring room or the like for measurement and improving the machining accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram of first and second NC lathes and an NC servo system according to an embodiment.

FIG. 2 is a flowchart showing the first operation of the embodiment.

FIG. 3 is a flowchart showing the second operation of the embodiment.

FIG. 4 is a block diagram of an NC lathe and an NC servo system according to a third embodiment.

FIG. 5 is a flowchart showing the third operation of the embodiment.

FIG. 6 is an NC in which a conventional vibration measuring sensor is attached.
It is a side view of a lathe.

FIG. 7 is a graph diagram in which a relative vibration amount of a headstock and a saddle of a conventional technique is measured.

FIG. 8 is a waveform diagram showing respective vibrations of a headstock and a saddle of a conventional technique, and a waveform diagram showing relative vibrations of the two.

FIG. 9 is a graph showing a shape error of a work piece due to relative vibration of a conventional technique.

FIG. 10 is a graph showing a shape error of a processed work due to relative vibration of a conventional technique.

[Explanation of symbols]

1 bed 2 saddle 3 turret 4 X-axis servo motor 6 linear position detector 7 turret 8A contact sensor 8B non-contact sensor 9 headstock 10 C-axis servo motor 17 measurement data storage unit 18 shape error calculation and storage unit 19 error Allowable value storage unit 20 Error comparison unit 21 Correction value data setting unit and storage unit 23 Reference perfect circular ring W Non-circular work T-byte

Claims (3)

[Claims] 1. A method for correcting a machining error caused by relative vibration between a spindle and a tool rest caused by reciprocating motion of the tool rest in the X-axis direction when creating a non-circular work by an NC lathe, and a shape stored in advance. Each time a non-circular work machined by data is indexed by a predetermined pitch, the X-axis position of the tool post is read when the contact sensor attached to the tool post comes into contact with the work to create measurement data. In-machine measurement of a non-circular work characterized in that a shape error is obtained by comparing with the shape data, and when the obtained shape error is larger than an allowable value stored in advance, the shape data is corrected using the shape error as a correction value. Error correction method for non-circular workpieces. 2. A method for correcting a machining error caused by relative vibration between a spindle and a tool rest caused by reciprocating movement of the tool rest in the X-axis direction when creating a non-circular work by an NC lathe,
A non-circular workpiece machined with shape data stored in advance is rotated at a low speed, and a non-contact sensor attached to a tool rest that is operated synchronously with the spindle based on the shape data continuously changes the gap in the X-axis direction with the workpiece. Non-circular by in-machine measurement of the non-circular workpiece characterized in that the shape error is directly measured to obtain the shape error, and the shape data is corrected using the shape error as a correction value when the obtained shape error is larger than an allowable value stored in advance. Workpiece error correction method. 3. A method for correcting a machining error caused by relative vibration between a spindle and a tool rest due to reciprocating motion of the tool rest in the X-axis direction when creating a non-circular work by an NC lathe.
The spindle and the turret are operated synchronously at the same speed as during machining based on the shape data, and the non-contact sensor attached to the turret continuously changes the gap in the X-axis direction between the spindle and the concentric reference circular ring. To form measurement data, and compare the measurement data with the shape data to obtain a shape error. When the obtained shape error is larger than a pre-stored allowable value, the shape data is set to the shape error as a correction value. A method for correcting an error of a non-circular work by in-machine measurement of the non-circular work characterized by performing correction.