JPH11248638A - Automatic detection method for surface of press-molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make quantitatively measurable of a cracking or curving in-line by confirming a portion where a surface defect is liable to occur through a specified number of detection is applied onto a preliminarily trially produced press-molded product. SOLUTION: A molding line with the use of the automatic surface detection method for a pressed product is, for example, provided with a laser device 8 for applying a laser slit beam to a molded product 5, and a testing base 7 above which an image pick-up device 9 to take in an image of the surface of the product 5 corresponding to the slit beam. Under the same conditions as the case of production in in the line a test press molding is carried out for producing a specified number of products, and through the inspection on these products the generation tendency of surface defects are confirmed. According to the tendency, an inspection portion is specified, and the installation place and direction are determined for every inspection portions, thereby enabling an in-line inspection in a short time. Also, according to surface defect amount of the test piece, an allowable amount corresponding to each inspection portion is set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic surface inspection method for a press-formed product, and more particularly, to an automatic surface inspection for a press-formed product capable of quantitatively in-line inspecting the constriction depth, cracks, etc. of a formed panel. About the method.

[0002]

2. Description of the Related Art Cracks and constrictions (a dent state just before a crack) generated in a press-formed product, if detected in a post-process after the press working, cause extremely large waste of work or cause the problem. This causes a major problem such as a troublesome work of removing (line-off) the product from the line. For example, in press lines such as molded panels for automobiles, welding and painting are performed after press working. If cracks or dents (dents) on the surface are detected in the inspection process after painting, these defects are detected. It takes a lot of time and labor to remove or replace the product, rework it, repaint it, and recheck these reworked parts. It is one of the important issues for improving the efficiency of the press line to prevent defective products from flowing out to the post-process and eliminate these reworking operations. Conventionally, many methods have been proposed for inspecting such surface and internal scratches and defects.

For example, Japanese Unexamined Patent Publication No. 7-286968 discloses a surface defect inspection for irradiating an inspection object with light and detecting a surface defect of the inspection object based on the amount of reflected light from the inspection object. In the apparatus, a light projecting means for irradiating the object to be inspected with light, a plurality of light receiving means set at a predetermined light receiving solid angle for receiving light reflected from the object to be inspected, There is disclosed a surface defect inspection apparatus including a light guiding unit for guiding the reflected light to the unit, and a signal processing unit for processing a signal from the light receiving unit.

Japanese Patent Application Laid-Open No. Hei 6-201607 discloses that an inspection section on a surface to be inspected is irradiated with a one-dimensional lattice pattern in which light intensity periodically changes in one direction. A surface inspection method has been disclosed in which the pattern image information read is subjected to a differentiation process in accordance with the stripe direction of the lattice, and the result is subjected to a threshold process to detect an abnormal portion of the inspection unit. .

Japanese Unexamined Patent Publication No. Hei 8-159743 discloses a non-contact type transmitting probe which is arranged obliquely so that an ultrasonic wave is incident on the surface of a material to be measured, a surface reflected wave from a material surface and a material. Two non-contact type receiving probes which are inclined at regular reflection positions for detecting internal reflected waves passing through the inside, respectively, receive electric signals of reflected waves detected by the two receiving probes, and receive surface reflected waves. And a signal processing system that detects the thickness of the material to be measured based on the elapsed time from the time when the internal reflection wave is detected to the time when the internal reflected wave is detected. The ultrasonic probe quickly measures the distance from the non-contact probe to the surface of the material to be measured, eliminating the effects of the distance fluctuations. Thereby making it possible to measure the remaining wall thickness.

[0006]

However, the following problems arise in the above-described conventional inspection methods and the like. The surface defect inspection apparatus disclosed in Japanese Patent Application Laid-Open No. 7-286968 requires a press-formed product having a complicated three-dimensional surface, in which the light receiving means needs to be arranged at a solid light receiving angle with respect to the light projecting means. When inspecting
It is very difficult for the light receiving means to accurately follow the three-dimensional surface. Further, this inspection apparatus only detects reflected light from the surface of a hot-rolled steel sheet conveyed at a high speed, for example, and only detects the presence or absence of a surface defect by comparing the magnitude of the received light amount. However, it is difficult to measure the actual defect amount. However, the depth of the constriction and crack of the press-formed product is very small (for example, about ten and several microns), and it is difficult to quantitatively measure the constriction depth and the like.

In the surface inspection method disclosed in Japanese Patent Application Laid-Open No. Hei 6-201607, the presence or absence of a flaw is detected by differentiating the image signal of the surface to be inspected. It is difficult.

Further, in the thickness measuring device disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-159743, a material to be inspected having a complicated three-dimensional curved surface such as a press-formed product is used.
It is very difficult to scan the transmitting probe and the two receiving probes following the curved surface, and to keep the respective probes in a predetermined positional relationship with each other. Therefore, there is a problem that the detection accuracy cannot be maintained high.

As described above, although the process of detecting a molding defect in a press-formed product is a very important process, it is not completely automated, and a part which still relies on a visual inspection by an operator is very large. There are many situations. For this reason, since the inspection time is required, the in-line operation efficiency is reduced, and the mental stress and the fatigue degree of the worker are increased as compared with other processes, so that the operation efficiency is reduced. Further, the detection accuracy varies depending on the skill level and the fatigue level, and the influence of the detection error on the subsequent process cannot be ignored.

The present invention has been made in view of the above-mentioned problems, and provides an automatic surface inspection method for a press-formed product capable of measuring in-line accurate and quantitatively the constriction or crack of the press-formed product. It is intended to be.

[0011]

Means for Solving the Problems, Functions and Effects In order to achieve the above object, an invention according to claim 1 is directed to an automatic surface inspection method for a press-formed product, in which a trial-produced press-formed product is prepared in advance. A step of performing a predetermined number of inspections to confirm a location where a surface defect has occurred, and specifying an inspection location from the location where the surface defect has occurred;
A measuring device is individually applied to at least one of the specified inspection locations to measure the amount of surface defects.

According to the first aspect of the present invention, a predetermined number of press-formed products are inspected in advance to check the locations where surface defects are likely to occur at the time of molding, and based on the occurrence locations, the press-formed products are inspected. The locations to be inspected are specified, and the inspection apparatus is individually applied to at least one of the specified inspection locations to measure the surface defect amount. Therefore, by focusing on areas where surface defects are likely to occur during molding, long-term inspections and full-scale inspection equipment are not required as in the case of full-surface inspection. Since the inspection is practically possible, the inspection can be performed relatively easily in a short time. In addition, the inspection accuracy does not vary due to the skill and fatigue of the operator in the conventional inspection process, and a press-formed product having a defect flows out to a subsequent process, so that the processing operation does not take much time. The efficiency of the entire press line can be improved.

According to a second aspect of the present invention, in the method for automatically inspecting a press-formed product according to the first aspect, the step of measuring the amount of surface defects is performed in-line.

According to the second aspect of the present invention, the measurement of the amount of surface defects is performed in-line, so that the automatic surface inspection in the line can be performed with high accuracy and in a short time. Efficient work can be performed on the entire line.

According to a third aspect of the present invention, in the automatic surface inspection method for a press-formed product, a predetermined number of test-produced press-formed products are inspected in advance to confirm a tendency of surface defects at a plurality of locations, A step of specifying a plurality of inspection locations based on the occurrence tendency, a step of setting an allowable value of the surface defect amount of the plurality of inspection locations based on inspection data of the prototype press-formed product, For each molded product,
A step of individually applying a measuring device to at least one inspection point out of the plurality of specified inspection points, measuring the surface defect amount, and comparing the measured surface defect amount with the set allowable value. Determining whether the inspection is successful or not.

According to the third aspect of the present invention, the tendency of occurrence of surface defects, which are likely to be generated during molding by a plurality of prototype press molded products, is confirmed in advance, and the inspection location of the press molded product is specified. In addition, the surface defect amount is measured by the inspection device at the specified inspection location. As a result, the automatic surface inspection of the press-formed product can be practically performed, so that the inspection can be performed in-line with high accuracy and at high speed. At this time, based on the inspection data of the prototype press-formed product, an allowable value of the surface defect amount at the inspection location is set, and the actually measured surface defect amount is compared with the set allowable value. Since the pass / fail of the inspection is determined, the pass / fail of the inspection result during the automatic surface inspection can be accurately and easily determined. As described above, in the production line including the press forming process, the surface defect amount of the press-formed product is measured accurately, reliably, and at a high speed, and the pass / fail is determined, so that the in-line inspection can be performed on the high-speed production line. .

According to a fourth aspect of the present invention, there is provided an automatic surface inspection method for a press-formed product according to the first, second or third aspect.
According to the method, the installation position and the direction of the measuring device are set in accordance with the tendency of occurrence of surface defects at the inspection location.

According to the fourth aspect of the present invention, the type, size and direction of occurrence of surface defects at inspection locations are checked in advance, and the amount of defects is determined in accordance with this tendency. The installation position and direction of the measuring device are set so that measurement can be performed with a predetermined accuracy. Thereby, it is set so as to be suitable for the measuring method (for example, when measuring with the laser slit light, the line irradiated with the laser slit light on the molded article is substantially perpendicular to the direction of the constriction), Measurement can be performed with high accuracy.

According to a fifth aspect of the present invention, there is provided an automatic surface inspection method for a press-formed product according to any one of the first to fourth aspects, further comprising a step of recording or displaying a measurement result of the surface defect amount or the like. And

According to the fifth aspect of the present invention, since the inspection result such as the amount of surface defects can be recorded or displayed, it becomes easy for an operator to grasp the tendency of the occurrence of the defect, and before the occurrence of a serious defect. , A predetermined response action can be taken.
As a result, in addition to the effects of the first to fourth aspects of the present invention, the number of molded articles rejected due to surface defects is greatly reduced, and the efficiency of the production line can be improved.

According to a sixth aspect of the present invention, in the automatic surface inspection method for a press-formed product according to the third aspect, after the step of judging pass / fail, a step of line-off of a rejected product is provided. .

According to the sixth aspect of the present invention, the rejected molded product is lined off, that is, removed from the production line by the pass / fail judgment based on the measurement result, so that there is no influence on the post-process of the production line. . As a result,
In addition to the effect of the invention described in claim 3, the operation rate of the entire line can be improved.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic explanatory view of a molding line employing an automatic surface inspection method for a press-formed product according to the present invention. In the figure, a press machine 1 has a bolster 2 provided at a lower portion of a main body frame, and a slide 3 provided at the upper portion of the main body frame so as to be movable up and down so as to face the bolster 2. A mold 4 is mounted between the slides 3. The slide 3 is driven up and down, and a predetermined molded product 5 is press-produced by the mold 4. Although FIG. 1 shows an example of a transfer press in which a plurality of dies 4 are attached, the present invention is not limited to the number of dies.

On the outside of the molded product discharge side of the press machine 1,
For example, an unloading device 6 composed of a general-purpose transfer robot is installed. The unloading device 6 takes out the molded article 5 from the press machine 1 and transports and sets it on the inspection table 7 in the next process. Or, a rejected product whose inspection result is determined to be rejected is removed out of line (off line). The transfer device 6 has a hand that can grip the molded product 5 without damaging it. In the present invention, the transfer device 6 is not limited to one transfer robot. For example, the transfer device 6 is configured by a plurality of transfer robots, each of which is for taking out from the press machine 1, for transferring to the inspection table 7, and It can also be used for product line-off.

Above the inspection table 7, a plurality of measuring devices for the surface inspection device are provided. Each measuring device includes a laser device 8 for irradiating the molded product 5 on the inspection table 7 with laser slit light, and an imaging device 9 for capturing an image of the surface of the molded product 5 corresponding to the laser slit light. The laser device 8 forms a thin linear slit light having a predetermined width into the molded product 5.
Is irradiated from a predetermined direction to a predetermined inspection location specified in advance. Further, the imaging device 9 can be constituted by, for example, a CCD device having a large number of pixels arranged two-dimensionally, and captures an image in the vicinity of the corresponding predetermined inspection point from a direction perpendicular to the molded article 5. So that it is oriented in a predetermined direction.

The image processing device 10 receives image signals from the respective image pickup devices 9 and performs predetermined image processing described later to calculate the amount of surface defects occurring at each inspection location.
Then, a pass / fail judgment of the molded article 5 is performed based on the magnitude of the defect amount. This pass / fail judgment is performed by comparing a permissible value set corresponding to the surface defect amount of a predetermined number of inspection locations specified in advance with the calculated defect amount. The image processing device 10 can be configured by a computer device mainly including a microcomputer or the like, for example.
Further, the image processing apparatus 10 is provided with a display device 11, and the display device 11 is adapted to display the results of the determination such as the measured defect amount and the pass / fail information. Display device 1
1 can be configured by a graphic display device such as a CRT device or a liquid crystal display device, or a character display device such as an LED. It should be noted that the measured results such as the defect amount and the pass / fail information are not only displayed on the display device 11, but also recorded on a recording device (not shown) or an external storage memory (floppy disk, hard disk, or the like). It is also possible for an operator to be able to refer to the determination result outside the work site.

Next, with reference to FIGS. 2 and 3, an example of a method for measuring the amount of surface defects of a press-formed product, in this case, the depth of constriction generated on the surface during molding will be described. FIG. 2 shows the relationship between the surface defect (constriction) of the molded article 5 and the laser slit light. In the figure, it is assumed that a constriction 21 having a depth d has occurred on the surface of the molded product 5. The constriction 21 usually tends to occur at a predetermined place determined by molding conditions such as the thickness, shape, and sliding speed of molding of the molded product 5, and therefore, the molded product when pressed under the same molding conditions It is possible to confirm this tendency by inspecting 5 for a predetermined number of points. In the automatic surface inspection method of a press-formed product according to the present invention,
Inspection of a plurality of molded products 5 prototyped under the same molding conditions in advance is performed, and the locations where the constriction 21 is likely to occur, the constriction length, the constriction depth, the direction of occurrence, and the like are confirmed, and based on this tendency, A plurality of locations to be inspected are specified in advance. Further, based on the inspection data measured in advance, an allowable value for the pass / fail judgment of the press-formed product is set, and the allowable value is stored in the image processing apparatus 10.

Based on this tendency, a position where the laser device 8 irradiates laser slit light,
The direction of the line 22 of the laser slit light, the angle between the laser slit light and the surface of the molded article 5 (hereinafter referred to as the irradiation direction) θ
Are set, and each laser device 8 corresponding to each inspection location is installed according to the set values. Usually, the laser device 8 is installed so that the line 22 of the laser slit light is substantially perpendicular to the direction in which the constriction 21 occurs (that is, the length direction). Further, each of the imaging devices 9 is installed in a direction perpendicular to the surface of the molded article 5 at the corresponding inspection location, and captures the image of the constriction 21 from the upper surface.

In the inspection under such conditions, when the generated constriction 21 is irradiated with the laser slit light, the laser slit light reaches the bottom of the constriction 21. At this time, the irradiation direction θ of the laser slit light is oblique to the surface.
Therefore, the line 22 of the laser slit light in the constriction 21 becomes extremely curved according to the cross-sectional shape of the constriction 21. Looking at the image of the laser slit light at the constriction 21, the line 22 has a convex shape in the constriction 21, and the vertex P of the convex shape corresponds to a point on the bottom surface of the constriction 21.

FIG. 3 is a view showing the laser slit light and the constriction 21 viewed from the direction of the straight line 22. The method of calculating the constriction depth d by the image processing apparatus 10 will be described with reference to FIG. In the figure, the length Y represents the length of a straight line PQ that is vertically lowered from the vertex P to the straight line 22 when the straight line 22 and the convex vertex P are viewed from the imaging device 9 in a plan view. The length Y can be obtained by performing image processing on image data captured by the imaging device 9 and calculating the distance between the convex vertex P and the straight line 22. The surface A formed by the laser slit light
And the angle formed by the surface of the molded product 5, ie, the straight line PQ
Is equal to the irradiation direction θ, the constriction depth d can be obtained from the following Expression 1.

D = (G / B) × y × tan θ where y represents the length on the image of the imaging device 9 corresponding to the length Y, and G is the direction along the straight line PQ Represents the number of pixels of the image pickup device 9 of the image pickup device 9, and B represents the number of pixels of the image pickup device 9 in the direction along the straight line PQ.
(The actual length seen in the image).

Next, an inspection method using the above-described automatic surface inspection apparatus will be described step by step. 1) First, a plurality of molded products 5 press-molded under the same predetermined molding conditions are inspected to confirm the tendency of defects such as constriction and cracks to occur. Identify. 2) Then, based on the measured value for each of the inspected defects,
Set the allowable value of the surface defect amount at the inspection location.

3) Next, in an actual automatic in-line inspection, a measuring device for an inspection device (here, a laser device) 8 and the imaging device 9) to capture an image for each inspection location. 4) The image processing apparatus 10 calculates the surface defect amount (here, the constriction depth) for each inspection location. 5) The calculated amount of surface defects is compared with the permissible value to determine whether or not the permissible range is satisfied. 6) The pass / fail judgment result and the measurement result are displayed on the display device 11 or recorded on the recording device. 7) Passed products are transported to the subsequent process as they are, and rejected products are removed from the line (line off).

As described above, when inspecting the amount of surface defects of an object to be inspected, inspection has conventionally been performed over the entire surface of the object to be inspected. However, in the automatic surface inspection method for press-formed products according to the present invention, The inspection locations are specified at a plurality of predetermined locations in consideration of the fact that the locations where surface defects (eg, necking, cracks, etc.) of press-formed products occur tend to be always limited to fixed locations. That is, a trial press molding is performed in advance under the same molding conditions as during production in a line, a predetermined number of molded products are manufactured, and these molded products are inspected to determine the tendency of surface defects to occur (the occurrence location, Size, direction, etc.). Then, based on this tendency, locations that are likely to occur are specified as inspection locations, and the installation location and direction of the measuring device are determined for each inspection location according to the occurrence tendency. As a result, it is possible to perform automatic surface inspection of the molded product in-line in a short time.

Further, based on the measured surface defect amount of the prototype molded product, an allowable value corresponding to each inspection location is set,
At the time of the automatic inspection on the actual line, the pass / fail judgment of the molded product can be made by comparing the measured value at each detection point and the allowable value for each molded product. As a result, an appropriate pass / fail judgment is made for each inspection location, so that inconveniences caused by surface defects at the time of molding in a subsequent process can be reduced. Then, the measurement result and the pass / fail judgment result are displayed on the display device 1.
Since the information is displayed on the recording device 1 or recorded on the recording device, the operator can grasp the tendency of the occurrence of the defect based on these results and predict whether or not a serious defect will occur. Therefore, a predetermined measure can be taken in advance before a defect occurs, and the occurrence of a defect can be prevented. Further, since the line that is determined to be rejected is lined off, there is no need to remove defective products in the post-process, and it is possible to eliminate wasteful work and improve the operation rate of the line.

Note that the in-line inspection in the above description includes, for example, a method of sampling, and the same effect can be obtained in this case.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a molding line employing an automatic surface inspection method for a press-formed product according to the present invention.

FIG. 2 shows the relationship between constriction on the surface of a molded article and laser slit light.

FIG. 3 is a diagram illustrating a method for calculating a constriction depth.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Press machine 5 Molded product 7 Inspection table 8 Laser device 9 Imaging device 10 Image processing device 11 Display device

Claims (6)

[Claims] 1. An automatic surface inspection method for a press-formed product, comprising: a step of previously inspecting a predetermined number of test-produced press-formed products to identify a location where a surface defect has occurred, and specifying an inspection location from the location where the surface defect has occurred; A step of individually applying a measuring device to at least one of the specified inspection locations and measuring the amount of surface defects, thereby automatically inspecting a press-formed product. 2. The automatic surface inspection method for a press-formed product according to claim 1, wherein the step of measuring the surface defect amount is performed in-line. 3. An automatic surface inspection method for a press-formed product, wherein a predetermined number of test-produced press-formed products are inspected in advance to confirm the tendency of surface defects at a plurality of locations, and a plurality of inspections are performed based on the tendency. Specifying a location, and setting an allowable value of the surface defect amount of the plurality of inspection locations based on the inspection data of the prototype press-molded product. A step of individually applying a measuring device to at least one of the plurality of inspection locations to measure the amount of surface defects; and comparing the measured amount of surface defects with the set allowable value to determine whether the inspection is successful or not. A method for automatically inspecting the surface of a press-formed product. 4. The automatic surface inspection method for a press-formed product according to claim 1, wherein an installation position and a direction of the measuring device are set according to a tendency of occurrence of surface defects at the inspection location. Characteristic automatic surface inspection method for press-formed products. 5. The automatic surface inspection method for a press-formed product according to claim 1, further comprising a step of recording or displaying a measurement result of the surface defect amount or the like. Automatic surface inspection method. 6. The automatic press-molded product surface inspection method according to claim 3, further comprising a step of line-off of the rejected product after the pass / fail determination step. Surface inspection method.