JP2003340528A - Device and method for evaluating dimensional accuracy of press-formed product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To support to specify a part that causes a dimensional error of a press-formed product. <P>SOLUTION: The support is carried out as follows: (S1) shape-data of a metal mold are read; (S2) shape-data of the press-formed product pressed by the metal mold are read; (S3) the minimum radius of curvature of a curved part of the mold is calculated based on the read shape-data of the mold; (S4) an evaluation range for evaluating the dimensional accuracy is calculated from the calculated minimum curvature radius; (S5) shape data existing in the evaluation range are extracted from the shape data of the press-formed product; (S6) a main curvature of a curved surface formed by the shape data of the press-formed product is calculated; (S7) the shape data of the mold corresponding to the extracted shape data of the press-formed product are extracted, and a main curvature of a curved surface formed by the extracted shape data of the mold is calculated; (S8) the difference between the calculated curvatures of both curved surfaces is calculated; and (S9) the calculated difference of the curvatures is displayed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press-molded product dimensional accuracy evaluation method and apparatus for enabling accurate evaluation of press-molded product dimensional accuracy.

[0002]

2. Description of the Related Art A typical defect that occurs in a press-formed product is poor dimensional accuracy. Some products are made by combining multiple press-formed products. In general, the press-molded product used as a part of such a product has a tolerance in the size of its mating portion so that the mating with other parts can be performed smoothly.

Generally, in press molding of iron or aluminum, elastic recovery occurs, so that the shape of the press-formed product after pressing does not become the same as the shape of the mold. Therefore, the dimensions of the mating portion of the press-formed product must be within the tolerance even if elastic recovery occurs.

[0004]

At present, for example,
Although there is a technique for improving the prediction accuracy of the springback amount as disclosed in Japanese Patent Laid-Open No. 2000-313933, it is difficult to accurately predict the size of the meeting portion in consideration of elastic recovery.

Therefore, the shape of the die itself is gradually corrected by trial and error so that the shape of the press-molded product after pressing becomes a desired shape. Since it takes a lot of man-hours to modify the mold, it leads to a longer mold making period, a longer product development period, and a higher development cost.

The present invention has been made to alleviate the problems of the conventional techniques as described above, and is capable of assisting in identifying the portion causing the dimensional error of the press-formed product. An object of the present invention is to provide a dimensional accuracy evaluation method and an apparatus thereof.

[0007]

[Means for Solving the Problems] In order to solve the above problems,
In order to achieve the object, the method for evaluating the dimensional accuracy of a press-formed product according to the invention as set forth in claim 1 includes a step of reading shape data of a die and a step of reading shape data of a press-formed article pressed by the die. And a step of obtaining a minimum radius of curvature of the curved surface portion of the die based on the read shape data of the die, a step of obtaining an evaluation range for evaluating dimensional accuracy from the obtained minimum radius of curvature, and the press forming The step of extracting the shape data existing in the evaluation range from the shape data of the product, the step of obtaining the curvature of the curved surface formed by the extracted shape data of the press molded product, and the shape data of the extracted press molded product. A step of extracting the shape data of the corresponding mold, a step of obtaining a curvature of a curved surface formed by the extracted shape data of the die, and a difference between the obtained curvatures of the curved surfaces. Characterized in that it comprises a step of displaying, the.

According to a fifth aspect of the present invention, there is provided a press-molded product dimensional accuracy evaluation apparatus, including a mold shape data storage means for storing mold shape data, and a press-formed product pressed by the mold. Press-formed product shape data storage means for storing shape data, minimum curvature radius calculation means for calculating the minimum curvature radius of the curved surface portion of the mold based on the shape data of the mold, and dimensions from the calculated minimum curvature radius An evaluation range calculating means for calculating an evaluation range for evaluating accuracy, and a press for extracting shape data existing in the evaluation range from the shape data of the press-formed product and calculating the curvature of the curved surface formed by the shape data. Surface curvature calculation means, shape data extraction means for extracting shape data of the mold corresponding to shape data existing in the evaluation range of the press-formed product, and the extracted metal Mold surface curvature calculating means for calculating the curvature of the curved surface formed by the shape data of the above, and curvature difference calculating means for calculating the difference between the curvature in the evaluation range of the press-formed product and the curvature in the evaluation range of the mold. A curvature difference storage means for storing the calculated curvature difference and a display means for displaying the stored curvature difference.

[0009]

As described above, according to the dimensional accuracy evaluation method for a press-formed product and the dimensional accuracy evaluation device for a pressed-formed product according to the present invention, the difference in the displayed curvatures is examined to obtain the press-formed product. The cause of the dimensional error can be efficiently identified, and an efficient rework is possible when correcting the shape of the mold.

Efficient reworking can shorten the mold making period, shorten the product development period, and reduce the development cost.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a press-formed product dimensional accuracy evaluation method and a press-formed product dimensional accuracy evaluation apparatus according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a schematic configuration of a press-molded product dimensional accuracy evaluation apparatus according to the present invention.

The press-molded product dimensional accuracy evaluation apparatus comprises a mold shape data storage unit 10 and a press-molded product shape data storage unit 1.
2, minimum curvature radius calculation unit 20, evaluation range calculation unit 22, shape data extraction unit 24, press surface curvature calculation unit 26, mold surface curvature calculation unit 28, curvature difference calculation unit 30, curvature difference storage unit 40, display 42. Have.

The mold shape data storage unit 10 stores the mold shape data created by CAD. The press-formed product shape data storage unit 12 stores the result of actual measurement of the press-formed product using a precision measuring device such as a three-dimensional measuring device as the shape data of the press-formed product.
As the shape data of the press-molded product, the shape data of the press-molded product after springback consideration may be used, which may be created by the mold shape data.

The minimum radius of curvature calculator 20 calculates the minimum radius of curvature of the curved surface of the mold based on the mold shape data stored in the mold shape data storage 10. When the mold has a plurality of curved surface portions, the minimum radius of curvature of all the curved surface portions is calculated.

The evaluation range calculation unit 22 is used to evaluate the dimensional accuracy of the press-formed product from the minimum curvature radius of the curved surface portion obtained by the minimum curvature radius calculation unit 20 (set on the curved surface portion). Is calculated.

The shape data extraction unit 24 extracts the shape data of the die corresponding to the shape data existing in the evaluation range among the shape data of the press molded products stored in the press molded product shape data storage unit 12. To do.

The press surface curvature calculation unit 26 extracts the shape data of the press-formed product existing in the evaluation range obtained by the evaluation range calculation unit 22 and calculates the curvature of the curved surface formed by the extracted shape data.

The mold surface curvature calculation unit 28 extracts the shape based on the mold shape data extracted by the shape data extraction unit 24, which exists in the evaluation range and corresponds to the shape data of the press-formed product. The curvature of the curved surface formed by the data is calculated.

The curvature difference calculation unit 30 calculates the curvature in the evaluation range of the press-formed product obtained by the press surface curvature calculation unit 26 and the curvature in the mold evaluation range obtained by the mold surface ratio calculation unit 28. Calculate the difference of.

The curvature difference storage unit 40 includes a curvature difference calculation unit 3
The difference in curvature obtained by 0 is stored.

The display 42 has a curvature difference storage section 40.
Show the difference in curvature stored in.

FIG. 2 is a flow chart showing the procedure of the method for evaluating the dimensional accuracy of a press-formed product according to the present invention. The procedure shown in this flowchart is executed by the press-molded product dimensional accuracy evaluation apparatus of FIG. This procedure will be described below with reference to FIGS. 3 and 4.

First, the minimum radius-of-curvature calculation unit 20 reads the shape data of the mold stored in the mold shape data storage unit 20 (S1). The mold shape data here is surface data in which the radius of the curved surface and the like are described.
Created by.

Next, the evaluation range calculation unit 22 reads the shape data of the press-formed product stored in the press-formed product shape data storage unit 12 (S2). The shape data of the press-formed product here is point cloud data obtained by actual measurement.

The minimum radius of curvature calculating section 20 obtains the minimum radius of curvature of the curved surface portion of the mold based on the shape data of the mold read in the step S1. When the mold has a plurality of curved surface portions, the minimum radius of curvature of all the curved surface portions is obtained (S3). As a calculation algorithm of the minimum radius of curvature, a commonly used known calculation algorithm is used.

The evaluation range calculator 22 is used to evaluate the dimensional accuracy of the press-formed product from the minimum radius of curvature of the curved surface obtained by the minimum radius of curvature calculator 20 (set on the curved surface). Ask for. The evaluation range is obtained for all curved surface portions (S4).

The evaluation range is specifically determined as follows. The solid line in FIG. 3 indicates the outer shape line of the actual mold. The circles scattered along the outline shape line are C
It is mold shape data (point cloud data) set by AD.

Here, the evaluation range is L, the obtained minimum radius of curvature of the curved surface of the mold is r, and the ratio of the circular arc to the circumference is c.
Is 1/4, 2πrc (1/4 arc length), and the number n of shape data existing in the arc is 9,

In the formula for obtaining the evaluation range, 3 / n
For example, there is a fillet shape that forms a ridge line in the fine shape of a press-formed product, but in order to evaluate the dimensional accuracy of this fillet shape, shape data of at least three points on a circular arc is specified. This is because, if exists, this curvature can be reproduced. In the above case, as shown in FIG. 3, there are 9 points of shape data on a 1/4 circular arc, but if there is 3 points of shape data, the shape size is minimized under the influence of noise. Since the accuracy can be evaluated, the evaluation range only needs to be 1/3 of the 1/4 arc. If the evaluation range is set to the minimum size in this way, the calculation amount can be reduced.

Further, considering the setting error of the evaluation range L,
Set the lower and upper limits of the setting as follows. here,
If L _p is an average interval in which shape data exists, the evaluation range L may be selected in the range of 4L _p ≦ L ≦ 2πrc · 3 / n. This is because if the evaluation range L is within this range, accurate evaluation is possible.

The lower limit value 4L _p is obtained as follows. As shown in FIG. 4, the average interval at which the shape data of the mold exists is L _p , and if this average interval is coarse, the actual shape as shown by the dotted line in the figure from the shape data of three points including the evaluation symmetry points is shown. A curvature value different from the curvature value is calculated. As described above, when the average interval is coarse, the shape data of 3 points is not sufficient, and therefore the shape data of 5 points is used as shown in the figure. That is, the range of 4L _p centered on the evaluation symmetry point is set as the evaluation range L. How to obtain such an evaluation range
This is particularly effective when the average interval of shape data is coarse.

Generally, the shape evaluation based on the curvature has an advantage that the generality of the evaluation is easily obtained because it is a shape index that does not depend on the coordinate system and it is sensitive to the change of the shape.
If shape evaluation is performed using measurement data including noise, local undulations are evaluated, and therefore, there is a disadvantage that highly reliable evaluation cannot be performed.

Considering the advantages and disadvantages of the shape evaluation based on the curvature, it is found that how to define and calculate the curvature is very important when performing the shape evaluation. That is, it is desirable to calculate the curvature within the maximum evaluation range that allows shape evaluation. In the present embodiment, the evaluation range is set so that the finest shape of the mold can be evaluated.

Next, the press surface curvature calculation unit 26 takes out the shape data of the press-formed product stored in the press-formed product shape data storage unit 12 and obtains it from the shape data as described above. The shape data (evaluation points) existing in the evaluation range are extracted (S5).

The press surface curvature calculating unit 26 has been extracted by the shape data extracting unit 24 obtains the principal curvatures K _{CA T} of curved surfaces formed by the shape data of the press-molded product present in the evaluation range (S6).

Then, the shape data extraction unit 24 extracts the shape data of the mold corresponding to the shape data existing in the evaluation range of the press-formed product from the mold shape data storage unit 10,
Mold surface curvature calculating unit 28 calculates a principal curvatures K _{CA D} curved surface formed in the shape data of the extracted die (S7).

The curvature difference calculation unit 30 calculates the main curvature K _CAT of the curved surface of the press-formed product calculated by the press surface curvature calculation unit 26 and the k of the mold and the main curvature of the mold calculated by the mold surface curvature calculation unit 28. The curvature K _CAD is acquired, and the absolute value of K _CAT −K _CAD , which is the difference between the main coverage ratios of both curved surfaces, is obtained (S8).

The curvature difference calculation unit 30 stores the obtained difference in the main station ratios in the curvature difference storage unit 40 (S9). The curvature difference stored in the curvature difference storage unit 40 is displayed on the display 4
2 is displayed (S10).

Based on the curvature difference displayed on the display 42 for each curved surface, the mold designer can assume the cause of the distortion in the shape after pressing. For example, among several curved surfaces in a mold, the curved surface having the largest curvature difference has a large influence on the other portions, and therefore it is understood that the shape of the curved surface may be modified. If the mold repair work is performed based on such an assumption, the mold repair work can be completed with a smaller number of man-hours than the repair work currently performed.

According to the above embodiment, it is possible to easily identify the part that causes the dimensional error.
Efficient and accurate measures can be taken. For this reason, it is possible to efficiently rework the shape of the mold.

Further, since the amount of calculation is small, it is possible to efficiently find out the cause of the dimensional error of the press-formed product even with a computer having only general analysis ability, and to carry out an efficient reworking. Thus, it is possible to shorten the mold production period, the product development period, and the development cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a press-formed product dimensional accuracy evaluation apparatus according to the present invention.

FIG. 2 is a flowchart showing a procedure of a method for evaluating dimensional accuracy of a press-formed product according to the present invention.

FIG. 3 is a diagram provided for explaining a step of obtaining an evaluation range.

FIG. 4 is a diagram provided for explaining a step of obtaining an evaluation range.

[Explanation of symbols]

10 ... Mold shape data storage unit, 12 ... Press-formed product shape data storage unit, 20 ... Minimum curvature radius calculation unit, 22 ... Evaluation range calculation unit, 24 ... Shape data association processing unit, 26 ... Press surface curvature calculation unit, 28 ... Mold surface curvature calculation unit, 30 ... Curvature difference calculation unit, 40 ... Curvature difference storage unit, 42 ... Display.

Claims (5)

[Claims] 1. A step of reading shape data of a mold, a step of reading shape data of a press-molded product pressed by the mold, and A step of obtaining a minimum radius of curvature, a step of obtaining an evaluation range for evaluating the dimensional accuracy from the obtained minimum radius of curvature, a step of extracting shape data existing in the evaluation range from the shape data of the press-formed product, A step of obtaining a curvature of a curved surface formed by the extracted shape data of the press-formed product, a step of extracting shape data of the mold corresponding to the extracted shape data of the press-formed product, and the extracted mold The dimensional accuracy evaluation of the press-formed product characterized by including the step of obtaining the curvature of the curved surface formed by the shape data of Valuation method. 2. The evaluation range is L = 2πrc · 3 / n L: evaluation range r: minimum curvature radius c of curved surface part of mold: ratio of arc to circumference n: data existing in arc of 2πrc The value is obtained by an expression represented by a number.
A method for evaluating the dimensional accuracy of a press-formed product according to. 3. The evaluation range L is selected such that 4L _p ≦ L ≦ 2πrc · 3 / n L _p : a range that satisfies an average interval in which shape data exists.
A method for evaluating the dimensional accuracy of a press-formed product according to. 4. The step of obtaining the minimum radius of curvature of the curved surface portion of the mold is to obtain the minimum radius of curvature of all the curved surface portions existing in the die, and the subsequent steps are steps of determining the dimensional accuracy for all the curved surface portions. The dimensional accuracy evaluation method for a press-formed product according to claim 1, wherein the method is repeatedly executed until the evaluation is completed. 5. A mold shape data storage unit for storing shape data of a mold, a press-molded product shape data storage unit for storing shape data of a press-molded product pressed by the mold, A minimum curvature radius calculation means for calculating a minimum curvature radius of the curved surface portion of the mold based on shape data; an evaluation range calculation means for calculating an evaluation range for evaluating dimensional accuracy from the obtained minimum curvature radius; Press surface curvature calculation means for extracting shape data existing in the evaluation range from the shape data of the molded product and calculating the curvature of the curved surface formed by the shape data, and a shape existing in the evaluation range of the press molded product. Shape data extraction means for extracting the shape data of the mold corresponding to the data, and a mold surface curvature calculator for calculating the curvature of the curved surface formed by the extracted mold shape data. A step, a curvature difference calculation means for calculating a difference between a curvature in the evaluation range of the press-formed product and a curvature in the evaluation range of the mold, a curvature difference storage means for storing the obtained difference in curvature, and a stored curvature And a display unit for displaying the difference between the press-formed product dimensional accuracy evaluation device and the press-formed product dimensional accuracy evaluation device.