JP2668618B2 - Dimensional change tendency tracking type automatic measurement correction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the diameter of a work continuously machined in a lathe or a grinder so as to correct the size so that the size error is always within the size tolerance.

[0002]

2. Description of the Related Art Conventionally, for example, in the dimension management method for automatically machining a work on a lathe, the work W is measured on or near the machine, and the measured value is close to the upper and lower limit values of the dimensional tolerance. At this point, dimension correction is performed. This correction method is, for example, as shown in FIGS.
In the case of product dimensions of m, the median dimensional tolerance is 50.00mm
OK area with a width of 0.01 mm that does not require correction across
A five-level region of ± OK region of 0.005 mm width and ± NG region deviating from the tolerance is set as a symmetrical region of the correction, and when the measured value enters the ± OK region, in the case of FIG. 0.005 mm, in the case of FIG. 4, the X-axis correction was performed using the difference between the measured value and the median dimensional tolerance as the correction value.

The block diagram of FIG. 5 shows the control system in the case of FIG. 4, in which the measurement value a measured by the measurement sensor 101 is compared with the median value b of the tolerances stored in the setting data storage section 102, and the dimensions are compared. The calculation (a−
b), an error c is obtained, and when the obtained error falls within the ± OK region, the correction determining unit 104 inputs the error c as a correction value to the X-axis servo system to perform the correction.

[0004]

The dimensional control method described in the prior art can be applied to a case where a dimensional change that tends to increase gradually, for example, due to a change over time due to tool wear, heat change, or the like. Since the control is always performed within the width of 1/2 of the tolerance, there is a problem that it is difficult to control the dimensions of a work having a small dimensional tolerance. The present invention has been made in view of such problems of the conventional technique, and an object of the present invention is to add a tendency correction amount to a conventional correction amount when the tendency of dimensional change is in the same direction. It is an object of the present invention to provide an automatic measurement correction method capable of effectively utilizing a width of a dimensional tolerance and realizing a stable value of product accuracy of a workpiece with strict accuracy.

[0005]

In order to achieve the above-mentioned object, the present invention corrects when a measured value of the diameter of a workpiece to be continuously machined enters a correction symmetric region near upper and lower limits of a dimensional tolerance stored in advance. In an automatic measurement correction method for outputting a value and performing a dimensional correction so as to be substantially the median of the dimensional tolerance,
Storing a new predetermined number of measurement data of the measurement value, at the time when the measurement value enters the correction symmetric region,
Only when the tendency of the dimensional change of the measurement data is in the same direction, a dimensional correction is performed by adding a previously stored tendency correction value to the correction value within a range that does not fall within the correction symmetric region.

[0006]

Function: The diameters of continuously processed workpieces are sequentially measured, and when the measured values enter the correction symmetric region, it is checked whether a predetermined number of dimensional errors immediately before have the same tendency, and stored only when the same tendency is observed. The dimensional correction is performed by adding the tendency correction value to the correction value of the difference between the dimensional error and the median of the tolerances.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS This embodiment will be described below with reference to the drawings. In the configuration diagram of the NC lathe in FIG. 1, a spindle 2 is rotatably supported by a spindle headstock 1, and a chuck 3 is concentrically fitted to the tip of the spindle 2. A tailstock 4 is movably fixed on one Z-axis guide provided on a bed (not shown), and a rotation center 6 is detachably mounted on a tip of a tailstock shaft 5 of the tailstock 4. ing. Further, a saddle 7 is movably mounted on the other Z-axis guide on the bed 1 (not shown), and the saddle 7 is moved and positioned by a Z-axis servo motor 8 via a ball screw 9. , A position detector 11 is mounted concentrically. A guide in the X-axis direction is provided on the saddle 7, and a tool post 12 is movably mounted on the X-axis guide.

The tool rest 12 is moved and positioned by an X-axis servomotor 13 via a ball screw 14, and a position detector 16 is concentrically fixed to the X-axis servomotor 13.
A turret 15 is provided on the tool rest 12 so as to be able to rotate and index around a rotation center axis in the Z-axis direction. The turret 15 has a plurality of tool mounting stations on the outer periphery, and measurement is performed on one of the tool mounting stations. The sensor 17 is detachably mounted. The X-axis position signal of the position detector 16 is read by the signal when the measurement sensor 17 contacts the outer periphery of the work W, and the measurement unit 18 outputs the measurement value a.

FIG. 1 is a block diagram showing the control system of this embodiment. The program storage unit 21 is a part for storing a machining program. The program interpreting unit 22 is a unit that interprets the read program and sorts the read programs into necessary places. The control position calculator 23 calculates the control position according to the program coordinate values. The control axis calculation unit 24
This is a part for obtaining a control position for each control axis. The Z-axis servo control unit 25 controls the rotation of the Z-axis servo motor 11. The X-axis servo controller 26 controls the rotation of the X-axis servo motor 13. And more than 21-2
6 is not different from a normal NC servo system.

The setting data storage unit 27 is a portion for storing a median value b, upper and lower limit values, and ± OK regions near the upper and lower limit values which are symmetrical to each other for correction. Dimension error calculator 2
Reference numeral 8 denotes a part for obtaining a dimensional error c from the measured value a and the median value b of the tolerance. The pass / fail determination unit 29 is a unit that determines pass when the dimensional error is within the upper and lower limit values of the tolerance and fails when the dimensional error exceeds the upper and lower limit values. The CRT 30 is a part for displaying the pass / fail. The correction judging unit 31 has a dimensional error of ±
A portion that outputs a correction command for setting the value of the dimensional error to the correction amount C when the correction value is within the OK area. The error data storage unit 32
The part that stores the data of the new predetermined number of dimensional errors,
When a new dimensional error is input and exceeds a predetermined number, the oldest dimensional error is released, and a new predetermined number of error data is always stored.

The tendency analysis / addition determination section 33 is a section for confirming the tendency of the change in the error data and determining whether or not to add the data. The part to output. Trend correction value storage unit 35
Is a part for storing the tendency correction value α input in advance. When the correction value C is output from the correction determination unit 31, the total correction value calculation unit confirms whether the addition signal is output from the tendency analysis / addition determination unit 33, and when the addition signal is output, the trend correction value is calculated. The tendency correction value α is called from the storage unit 35, and the correction value C
This is a part that outputs a correction signal as a total correction value without using the correction value C when an addition command is not issued.

Next, regarding the operation of this embodiment, for example, the product size is φ50 ± 0.01 mm, and the width of the OK region is 0.
The width of the 01 mm and ± OK areas is 0.005 mm, the tendency correction value α is 0.003 mm, and the predetermined number is 4
The graph of the dimension management data shown in FIG. When continuous processing is performed and the dimension measurement value a of the fourth work becomes 50.007 mm and enters the + OK region, the correction value C of −0.007 is obtained from the correction determination unit 31.
Is output to the total correction value calculation unit 36. Then, the total correction value calculation unit 36 confirms whether the trend analysis / addition determination unit 33 has issued an addition command. In this case, since the dimensions are all changed to the + side, an addition signal is output, the correction value α is read from the tendency correction value storage unit, and the X-axis correction is performed using the total correction value of −0.01 mm obtained by calculation C + α. Is performed.

Next, the sixth measured value after correction is 50.00.
In the + OK region at 7 mm, the X-axis correction of -0.01 mm of the sum of the correction value C and the tendency correction value α is performed in this case also because all four error data are dimensionally changed to the + side. Although not shown in FIG. 2, if even one of the four stored error data is dimensionally changed to the negative side (opposite side), or if it is less than the corrected predetermined number of four, No addition of the tendency correction value α is performed.

[0014]

Since the present invention is configured as described above, the following effects can be obtained. When the workpieces that have undergone continuous processing are sequentially measured and the measured values enter the correction symmetry area that is stored in advance, the tendency correction that is stored in the correction values only when the tendency of the dimensional change of a predetermined number of measurement data is in the same direction Dimension correction is performed by adding the
Since the width of dimensional control performed within the width of / 2 has been widened,
It is possible to stabilize the product dimensions of a workpiece having strict dimensional tolerances, thereby facilitating dimension management.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an NC lathe according to an embodiment and a block diagram of a control system.

FIG. 2 is a graph of dimension management data to which a trend correction value is added.

FIG. 3 is a graph of dimension management data with a constant correction amount according to a conventional technique.

FIG. 4 is a graph diagram of dimension management data in which a correction amount according to a conventional technique is a measured value-a median of dimension tolerances.

FIG. 5 is a configuration diagram of a conventional NC lathe and a block diagram of a control system.

[Explanation of symbols]

Reference Signs List 1 headstock 2 spindle 3 chuck 4 tailstock 8 Z-axis servomotor 11, 16 position detector 13 X-axis servomotor 15 turret 17 measurement sensor 32 error data storage unit 33 trend analysis / addition determination unit 35 trend correction value storage unit 36 Total correction value calculation unit W Work

Claims (1)

(57) [Claims] 1. When a measured value of the diameter of a workpiece to be continuously machined sequentially enters a correction symmetric region near upper and lower limits of a dimensional tolerance stored in advance, a correction value is output and a median value of the dimensional tolerance is substantially obtained. In the automatic measurement correction method for performing dimensional correction so that the measured data of a new predetermined number of the measured values is stored, and when the measured values fall within the correction symmetry region, the tendency of dimensional change of the measured data A dimensional change tendency tracking type automatic measurement and correction method characterized in that a dimensional correction is performed by adding a tendency correction value stored in advance to the correction value in a range that does not fall within the correction symmetry area only when the directions are the same.