JP2024038596A - Resin molding inspection method, inspection device, and computer program used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently inspect the state of the thickness deviation of resin moldings and obtain objective and highly reliable inspection results.

SOLUTION: The inspection range of a bottle as a blow molded resin molding is illuminated by excitation light such as ultraviolet light, and detection object light such as fluorescence in a wavelength region different from the wavelength region of the excitation light is radiated from the bottle. The inspection range of the bottle being illuminated by the excitation light is imaged in such a way that the wavelength region of the detection object light is included in the wavelength region of the imaging object, whereas the wavelength region of the excitation light is excluded from the wavelength region of the imaging object, and the state of thickness deviation in the inspection range is inspected on the basis of the intensity distribution of the detection object light in the captured image.

SELECTED DRAWING: Figure 9

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention is a method for inspecting the uneven thickness of a blow-molded resin molded product by utilizing the phenomenon that when a resin molded product is irradiated with excitation light in a specific wavelength range, light with different wavelength ranges is emitted. Regarding etc.

There is a known method for inspecting the suitability of an inspection target by utilizing the phenomenon that when a resin molded product is irradiated with excitation light in a specific wavelength range, light in a wavelength range different from that of the excitation light is emitted from the resin molded product. There is. For example, by illuminating a bottle made of PET resin (polyethylene terephthalate resin) with ultraviolet light and causing the bottle to emit fluorescence, it is possible to create a connection between the bottle and the inspection object, such as a label wrapped around the bottle or a printed part on the bottle. A method has been proposed in which a difference in brightness is generated in the object, and the quality of the object to be inspected is determined using the difference in brightness as a clue (for example, see Patent Documents 1 and 2).

Japanese Patent Application Publication No. 2008-281477 JP2022-37644A

A resin bottle is formed by blow molding a generally hollow cylindrical preform. In blow molding, molding defects are caused by uneven wall thickness, which is caused by local insufficient stretching of the resin and uneven wall thickness due to errors in the shape of the preform, control errors in temperature and other various parameters that affect molding quality, etc. It may occur as a type of. Inspection for molding defects is left to visual inspection by an operator, but uneven thickness defects require an understanding of subtle differences in wall thickness and are difficult to identify by visual inspection alone. Therefore, it was necessary for the operator to determine the state of uneven thickness while also using tactile sensation. However, such work is inefficient, and the operator's proficiency level may affect the quality of the test, which may impair the objectivity and reliability of the test results. If uneven thickness defects occur, it is necessary to adjust various parameters that affect molding quality, such as the temperature control parameters of the molding machine, but if the inspection quality is not sufficient, the adjustment work can be a trial and error process. As a result, efficiency deteriorates. Therefore, it is desired to develop an inspection method that can improve the efficiency of a series of operations from inspecting the state of uneven thickness to adjusting parameters to eliminate defects. The above-mentioned conventional inspection method uses the bottle to emit fluorescence to function as a light source, thereby determining the presence or absence of defects in the inspection target such as the label attached to the bottle. It is not intended to inspect molding defects.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an inspection method for resin molded products that can efficiently inspect the state of uneven thickness of resin molded products and obtain objective and highly reliable test results. do.

A resin molded product inspection method according to one aspect of the present invention is a resin molded product inspection method for inspecting the state of uneven thickness in a blow-molded resin molded product, and includes a method for inspecting a resin molded product that has a wavelength different from the wavelength range of the irradiated light. A step of illuminating an inspection range of the resin molded product with excitation light that can be emitted from the resin molded product using light in the area as detection target light, and the inspection of the resin molded product illuminated with the excitation light. A procedure for imaging a range such that the wavelength range of the detection target light is included in the wavelength range of the imaging target while the wavelength range of the excitation light is excluded from the wavelength range of the imaging target, and the captured image and a step of inspecting the state of uneven thickness in the inspection range based on the intensity distribution of the detection target light inside.

A resin molded product inspection device according to one aspect of the present invention is a resin molded product inspection device that inspects the state of uneven thickness in a blow-molded resin molded product, and has a wavelength range different from that of the irradiated light. illuminating means for illuminating an inspection range of the resin molded article with excitation light that can be emitted from the resin molded article as detection target light; an imaging means for imaging an inspection range such that the wavelength range of the detection target light is included in the wavelength range of the imaging target, while the wavelength range of the excitation light is excluded from the wavelength range of the imaging target; and inspection means for inspecting the state of uneven thickness in the inspection range based on the intensity distribution of the detection target light in the image, and outputting an inspection result.

A computer program according to one aspect of the present invention is a resin molded product inspection device that inspects the state of uneven thickness in a blow-molded resin molded product, and the computer program uses light in a wavelength range different from that of the irradiated light. illumination means for illuminating an inspection range of the resin molded product with excitation light that can be emitted from the resin molded product as detection target light; and an illumination unit that illuminates the inspection range of the resin molded product illuminated with the excitation light, An inspection device comprising an imaging means for capturing an image such that the wavelength range of the detection target light is included in the wavelength range of the imaging target, while the wavelength range of the excitation light is excluded from the wavelength range of the imaging target. An applied computer program that controls the computer of the inspection device based on an image acquisition unit that acquires an image captured by the imaging unit, and the intensity distribution of the detection target light in the acquired image. It is configured to function as an inspection means for inspecting the state of uneven thickness in the inspection range and outputting the inspection results.

1 is a diagram showing an example of an inspection device used in an inspection method according to an embodiment of the present invention. FIG. 3 is a diagram showing the results of measuring a three-dimensional fluorescence spectrum when a sample piece made of polyethylene terephthalate resin was irradiated with ultraviolet light. The figure which shows an example of the relationship between the spectral intensity of the ultraviolet light which illuminates a bottle, the spectral intensity of fluorescence emission of a bottle, and the spectral sensitivity of a filter. The figure which shows an example of the spectral sensitivity of a camera. FIG. 3 is a diagram illustrating an example of uneven thickness defects that are inspected by the inspection method according to one embodiment. An example of an image showing the difference in fluorescence emission between a normal bottle with no uneven thickness and a bottle with uneven thickness. FIG. 7 is a diagram showing the degree of variation in wall thickness in the inspection range of each bottle shown in FIG. 6 based on the correspondence between the measured value of fluorescence intensity and the probability density. FIG. 7 is a diagram showing the correspondence between the average value of the measured fluorescence intensity in the inspection range of each bottle shown in FIG. 6 and the standard deviation regarding the variation in wall thickness. 2 is a flowchart illustrating an example of the procedure of an inspection process executed by the inspection unit of the inspection apparatus in FIG. 1. FIG.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an example of an inspection device used in an inspection method according to one embodiment of the present invention. In the inspection method of this embodiment, when a resin molded product is irradiated with excitation light in a specific wavelength range, light in a wavelength range different from that of the excitation light is emitted as detection target light, and the intensity of the detection target light is The state of uneven thickness of the resin molded product is inspected by utilizing the property that there is a relationship between the thickness of the resin molded product and the larger the wall thickness, the higher the intensity of the light to be detected. In the following embodiment, ultraviolet light in a specific wavelength range is used as an example of excitation light, and the state of uneven thickness is inspected using fluorescence generated in response to the ultraviolet light irradiation as an example of detection target light. The inspection device 1 in FIG. 1 inspects a bottle 2 as an example of a resin molded product to be inspected.The inspection device 1 includes an image acquisition unit 10 that acquires an image based on fluorescence of the bottle 2; The apparatus includes a processing section 20 that processes the acquired image and inspects the state of uneven thickness. The bottle 2 is formed, for example, by blow-molding a generally hollow cylindrical preform made of PET resin in a predetermined mold (molding mold). The body 2a of the bottle 2 has a generally cylindrical shape, and the shoulder 2c between the neck 2b and the body 2a has a generally truncated conical shape. The bottom portion 2d has a shape in which the center portion is recessed inward along the axis AX.

The image acquisition unit 10 includes an illumination device 11 as an example of illumination means for illuminating the bottle 2, and an imaging device 12 as an example of an imaging means for taking an image of the bottle 2. The illumination device 11 illuminates the inspection range of the bottle 2 with predetermined illumination light. The inspection range may be the entire bottle 2 or a part of the bottle 2. The illumination device 11 irradiates the bottle 2 with ultraviolet light in a wavelength range that can cause the bottle 2 to emit fluorescence as illumination light. Specific examples of the wavelength range of ultraviolet light will be described later. In the example of FIG. 1, the range from the body 2a to the shoulder 2c of the bottle 2 is set as the inspection range. The lighting device 11 includes, for example, an upper illuminator 11a that illuminates the inspection range from diagonally above, and a lower illuminator 11b that illuminates the same inspection range of the bottle 2 from diagonally below. However, the inspection range of the bottle 2 may be changed as appropriate as described above, and the configuration and illumination direction of the illumination device 11 may also be changed as appropriate according to the inspection range of the bottle 2. For example, when inspecting the neck 2b and shoulder 2c of the bottle 2, the illumination device 11 and the imaging device 12 may be placed in accordance with their positions. When inspecting the bottom part 2d, the camera 13 of the imaging device 12 is arranged below the bottle 2 so that its imaging optical axis Lp coincides with the axis AX, and the illumination device 11 is also arranged to illuminate the bottom part 2d from an oblique direction. may be placed in

The imaging device 12 includes a camera 13 and a filter 14 that limits the wavelength range of light incident on the camera 13 to a range suitable for inspection. The camera 13 converts an optical image of the bottle 2 into an electrical image signal using, for example, an image sensor such as a CCD or a CMOS. The camera 13 images the inspection range of the bottle 2 emitting fluorescent light. The imaging direction is set, for example, so that the bottle 2 is imaged from the same side as the illumination direction by the lighting device 11. In the example of FIG. 1, the imaging optical axis Lp of the camera 13 is oriented in the horizontal direction, and the illuminators 11a and 11b are arranged so that the optical axes La and Lb of the illuminators 11a and 11b extend symmetrically across the imaging optical axis Lp. and a camera 13 are arranged. Note that the imaging direction does not necessarily need to be set on the same side as the illumination direction by ultraviolet light, as long as an image that clearly reflects the intensity distribution of fluorescence generated in the bottle 2 can be taken. For example, depending on the inspection range of the bottle 2, the relationship between the illumination direction and the imaging direction is different from that shown in FIG. may be set to .

The imaging range of the camera 13 may be set so that at least an image of the inspection range of the bottle 2 can be captured. Note that during the inspection, the bottle 2 may be stationary or may be moving. For example, the moving bottle 2 may be sequentially imaged by installing the camera 13 on a beverage filling line and causing the camera 13 to perform an imaging operation at the timing when the bottle 2 reaches the imaging range of the camera 13. If only a part of the inspection range can be imaged with one imaging operation using one camera 13, such as capturing an image of the entire circumference of the bottle 2 as an inspection range, the bottle 2 may be rotated and the entire circumference of the bottle 2 may be imaged. An image of the entire inspection range may be captured by controlling the imaging operation of the camera 13 so that the image is captured in multiple times. The bottle 2 may be fixed, and the illumination device 11 and the imaging device 12 may be moved around the bottle 2 to capture an image of the entire inspection range. Alternatively, a plurality of cameras 13 may be provided to take images of the bottle 2 from different directions, and the inspection range of the bottle 2 may be shared in the circumferential direction by these cameras 13 to take images. The lighting device 11 may be lit all the time, or may be controlled to be lit in synchronization with the imaging operation of the camera 13. Note that the inspection range does not necessarily need to be set around the entire circumference of the bottle 2. Further, the inspection range does not necessarily need to be set as a surface having a certain extent. For example, a plurality of spot-like detection positions may be set on the bottle 2, a set of these detection positions may be set as an inspection range, and an image of each detection position may be imaged by the camera 13 as an image of the inspection range. In order to capture such an image, for example, from the image captured by the image sensor of the camera 13, a pixel group corresponding to the detection position may be outputted from the camera 13 as an image signal readout target, or Alternatively, an image signal corresponding to the imaging range of the image sensor may be output, and an image signal corresponding to the detection position may be extracted from the image signal to obtain an image of the detection range. When a set of a plurality of spot-shaped detection positions is used as an inspection range, the accuracy of inspection can be improved by increasing the number of detection positions. In any case, the imaging range of the camera 13 may be set to include the inspection range, and the inspection range may be set to at least a part of the imaging range of the camera 13.

Regarding the wavelength range to be imaged by the camera 13, the filter 14 is arranged such that the wavelength range of fluorescence generated in the bottle 2 is included in the wavelength range of the imaged object, while the wavelength range of ultraviolet light illuminating the bottle 2 is included in the wavelength range of the imaged object. The wavelength range of the incident light to the camera 13 is adjusted so that it is excluded from the wavelength range. However, the spectral characteristics of the filter 14 do not necessarily need to be set to completely block the incidence of the ultraviolet light wavelength range into the camera 13. The wavelength range of ultraviolet light is such that the image captured by the camera 13 shows a brightness distribution reflecting the distribution of fluorescence intensity, and the influence of the wavelength range of ultraviolet light on the brightness distribution is substantially eliminated from the image. It is only necessary that the filter 14 restricts the passage of the light. In other words, the spectral characteristics of the filter 14 are such that the wavelength range of the ultraviolet light that illuminates the bottle 2 is limited compared to the wavelength range of the fluorescence generated in the bottle 2 with respect to the wavelength range of the light incident on the camera 13. It is sufficient if it is set. To that extent, the filter 14 is not limited to completely blocking the incidence of ultraviolet light in the wavelength range, but may be one that relatively reduces the amount of incident light in the ultraviolet wavelength range compared to that in the fluorescence wavelength range. There may be.

On the other hand, regarding the wavelength range of fluorescence, it is sufficient that the amount of fluorescence necessary for inspection is incident on the camera 13. The spectral characteristics of the filter 14 may be set so that the entire wavelength range of the fluorescence passes through the filter 14 and enters the camera 13, or the filter 14 restricts the incidence of part of the wavelength range of the fluorescence into the camera 13. may be done. For example, in the wavelength range of fluorescence, for a part of the wavelength range on the short wavelength side that is relatively close to the wavelength range of ultraviolet light as illumination light, the filter 14 restricts its passage, and the restricted wavelength range The spectral characteristics of the filter 14 may be set so that fluorescence with wavelengths longer than that of the filter 14 passes through the filter 14 and enters the camera 13.

The reason why the filter 14 is used to limit the wavelength range of the imaging target is as follows. The light directed from the bottle 2 toward the camera 13 includes not only fluorescence generated in the bottle 2 but also ultraviolet light reflected by the bottle 2. When ultraviolet light enters the camera 13, the resulting image is affected by the ultraviolet light, which may impede inspection for molding defects based on the fluorescence intensity distribution. On the other hand, the wavelength range of fluorescence generated in PET resin does not match the wavelength range of the irradiated ultraviolet light, and a difference occurs between the two wavelength ranges. Therefore, if the spectral characteristics of the filter 14 are set so that the wavelength range of fluorescence is included in the wavelength range of the object to be imaged by the camera 13, while the wavelength range of ultraviolet light is excluded from the wavelength range of the object to be imaged, It is possible to capture an image that accurately reflects the intensity distribution of fluorescence by suppressing the influence of reflected light. Note that it is not necessarily necessary to use the filter 14 as a separate component from the camera 13 as a means for selecting the wavelength range of the imaging target. For example, if the camera 13 has a function that allows selection of the wavelength range in which the image sensor of the camera 13 exhibits sensitivity, the wavelength range of the imaging target may be adjusted using that function. Note that the wavelength range of the excitation light and the wavelength range of the fluorescence to be detected may be such that the reflected light from the bottle 2 contains higher-order light components such as secondary light with a wavelength twice that of the excitation light. If light in a wavelength range different from any of the above is included as a disturbance component and the disturbance component affects the brightness difference in the image, the filter 14 spectroscopy is adjusted so that the disturbance component is also removed from the wavelength range of the imaging target. The characteristics and the sensitivity of the camera 13 may be set.

Note that the illumination light of the bottle 2 in the environment where the image acquisition unit 10 is installed is mainly the illumination light from the illumination device 11, and the image reflecting the intensity distribution of fluorescence generated in the bottle 2 is captured by the camera 13. Ambient light in the visible range, such as natural light, may be included as long as the image is captured in the image. That is, the bottle 2 may be illuminated only by the illumination light from the illumination device 11 while blocking the environmental light, or some environmental light may be used as long as it does not substantially affect the image reflecting the intensity distribution of fluorescence. may be incident on bottle 2. Alternatively, the filter 14 or the like may be used to remove from the image captured by the camera 13 the influence of light in the visible range that is unnecessary for capturing an image reflecting the fluorescence intensity.

Next, a specific study regarding selection of the wavelength range of ultraviolet light of the illumination device 11 will be explained with reference to FIGS. 2 to 4. FIG. 2 shows the results of measuring a three-dimensional fluorescence spectrum when a sample piece of PET resin was irradiated with ultraviolet light. The vertical axis is the wavelength of the irradiated ultraviolet light, and the horizontal axis is the wavelength of fluorescence. The density of the contour lines in the figure indicates the fluorescence intensity, and the denser the contour lines, the higher the fluorescence intensity. According to FIG. 2, when PET resin is irradiated with ultraviolet light around 365 nm, relatively high intensity fluorescence is generated in the wavelength range of 380 to 430 nm.

FIG. 3 shows the relationship between the spectral intensity of ultraviolet light illuminating the bottle 2, the spectral intensity of fluorescence emission from the bottle 2, and the spectral sensitivity of the filter 14. In FIG. 3, the horizontal axis represents the wavelength, and the vertical axis represents the spectral intensity of ultraviolet light and fluorescence and the spectral sensitivity of the filter 14, respectively. As understood from FIG. 3, when a PET resin is illuminated with ultraviolet light whose spectral intensity peaks around 365 nm, fluorescence occurs in the wavelength range of 380 nm to 430 nm. Although the spectral intensity distribution of ultraviolet light and the spectral intensity distribution of fluorescence partially overlap, if the wavelength range of ultraviolet light is in the range of 360 nm to 380 nm, the spectral characteristics of the filter 14 can be changed from approximately 400 nm to long wavelengths. If the setting is made to allow the light from the bottle 2 to pass through and to restrict the passage of the shorter wavelength range, the fluorescence generated in the bottle 2 can be efficiently transmitted to the camera 13 while suppressing the incidence of ultraviolet light to the camera 13. It can be input to

According to FIG. 2, it is possible to obtain more fluorescence by setting the wavelength range of the ultraviolet light so that the peak is around 320 nm. However, in that case, the wavelength range of fluorescence also shifts to the shorter wavelength side. As shown in FIG. 4, the spectral sensitivity of a general camera used for the purpose of capturing images in the visible light range is highest near 550 nm. The sensitivity of the camera is substantially lost at around 1000 nm on the long wavelength side and around 400 nm on the short wavelength side. Therefore, if the wavelength range of ultraviolet light is set to around 320 nm, the wavelength range of fluorescence may deviate from the wavelength range in which the camera 13 exhibits sufficient spectral sensitivity. Therefore, it is preferable that the ultraviolet light emitted from the lighting device 11 be set in the range of 360 nm to 380 nm as described above.

Next, with reference to FIG. 5, an example of uneven thickness defects to be detected by the inspection method of this embodiment will be described. Blow molding of the bottle 2 involves heating the preform to the glass transition temperature to soften it into a rubber-like state, and then stretching the preform in the direction of the axis AX of the bottle 2 (Fig. 1) using a stretching rod. This is carried out by introducing gas pressure into the preform, thereby stretching the preform in two axial directions (vertical and horizontal), and cooling and solidifying it. If there is a shape error in the preform, or various operations and controls during the molding process, such as temperature control related to resin heating such as heater output (heating amount) to heat the preform, stretching operation with a stretching rod, mold If there is a deficiency in the temperature control, etc. of each part of the preform, the preform may not be stretched uniformly, and molding defects may occur. For example, if stretching is insufficient locally, uneven thickness defects may occur where the thickness becomes non-uniform. FIG. 5 shows an example in which an uneven thickness portion D1 occurs in the shoulder portion of the bottle 2, and FIG. 5(b) shows an example in which an uneven thickness portion D2 occurs in the bottom portion of the bottle 2. Alternatively, as shown in FIG. 5(c), a misaligned portion D3 may occur at the bottom as a result of uneven stretching. The misaligned portion D3 is where a core portion with a relatively large wall thickness should normally be formed around the axis AX of the bottom of the bottle 2, but due to uneven stretching, it is a portion that is deviated from the center of the bottom portion. This occurs due to an increase in wall thickness. Therefore, the misaligned portion D3 can also be regarded as a type of defective thickness unevenness like the uneven thickness portions D1 and D2. In addition, uneven thickness may occur at other locations such as the body.

When the uneven thickness defect as described above occurs, a change occurs in which the fluorescence intensity increases compared to the normal level at the portion where the thickness increases. Therefore, the distribution of fluorescence intensity when ultraviolet light is irradiated on the bottle 2 with defective thickness unevenness is different from the distribution of fluorescence intensity during normal times when defective thickness unevenness does not occur. For example, when a defective thickness occurs, the distribution of fluorescence intensity changes so that there are areas where the fluorescence intensity is high or low compared to the normal distribution of fluorescence intensity. The difference in the distribution of fluorescence intensity does not necessarily need to be evaluated as a difference in the height of the fluorescence intensity associated with the position of the bottle 2. For example, a change in which the degree of variation in fluorescence intensity when uneven thickness defects occurs is greater than the degree of variation in fluorescence intensity during normal times can also be regarded as a change in the distribution of fluorescence intensity.

Next, a specific study on the relationship between the fluorescence intensity of the bottle and the state of uneven thickness will be explained. Figure 6 is an example of an image of the shoulder of a bottle, where (a) is an image of a normal bottle with no uneven thickness defects, and (b) is an image of a bottle with some uneven thickness defects. , Figure (c) is an image of a bottle in which the thickness unevenness defect has further progressed. The uneven thickness defects shown in FIGS. 6(b) and 6(c) were caused by setting the output of the heater for heating the area where the shoulder part of the mold is formed to be lower than the reference value. For example, Fig. 6(a) shows the case where the heater output is set to 75% of the standard output, Fig. 6(b) shows the case when the heater output is set to 65%, and Fig. 6(c) shows the case where the heater output is set to 55%. This is the case when it is set to . From the comparison of FIGS. 6(a) to 6(c), it can be confirmed that the fluorescence intensity at the location where the uneven thickness defect occurs is higher than that in the normal case. Moreover, the degree of the uneven thickness defect may be correlated with the output of the heater, that is, the value of the parameter that controls the temperature of the mold.

Figure 7 shows the relationship between the measured values and the probability density of the measured values when the circumferential direction of each bottle in Figures 6 (a) to (c) is changed by 10 degrees and the fluorescence intensity is measured in each direction. The results are shown below. In this case, the entire circumference of the bottle is the inspection range. Sample 1 corresponds to the bottle in FIG. 6(a), sample 2 corresponds to the bottle in FIG. 6(b), and sample 3 corresponds to the bottle in FIG. 6(c). Therefore, the heater output of samples 1 to 3 is 75 %, 65%, and 55%. The horizontal axis in FIG. 7 is the illuminance measurement value, which corresponds to the fluorescence intensity. The vertical axis is the probability density, which is a value that quantitatively indicates the frequency with which illuminance measurement values appear. The higher the probability density, the more frequently the illuminance measurement value appears.

As is clear from FIG. 7, in Sample 1 in which no thickness deviation defects occur, the measured illuminance values tend to concentrate in a relatively narrow range with a peak around 42, and the variation in fluorescence intensity is relatively small. On the other hand, in Samples 2 and 3 where uneven thickness defects occur, there is a tendency for the variation in the measured illuminance values to be large, and the degree of variation is larger in Sample 3 than in Sample 2, and the peak of the probability density is also higher than in Sample 2. Sample 3 is smaller. Therefore, it is understood that the greater the variation in bottle wall thickness due to uneven wall thickness defects, the greater the variation in fluorescence intensity tends to be.

Figure 8 shows the relationship between the average value of the measured values and the standard deviation of the obtained measured values when the fluorescent intensity of the shoulder of the bottle was measured by changing the circumferential direction of the bottle by 10 degrees. The results are shown below. In this case as well, the entire circumference of the shoulder of the bottle is the inspection range. The average illuminance value on the horizontal axis in the figure represents the fluorescence intensity of images captured every 10 degrees by the average value in the image, and corresponds to a value obtained by further averaging the representative values of the images at each angle. The standard deviation on the vertical axis indicates the degree of variation in the representative value of fluorescence intensity obtained by measuring every 10 degrees of the bottle. In this measurement, bottles were molded by varying the heater output for heating the preform from 55% to 90% in 5% increments, and the relationship between the average illumination value and standard deviation was investigated for each heater output. Note that the heater output of 75α% is an example in which a slight correction is added to the heater output of 75%.

As is clear from FIG. 8, the average value and standard deviation of the fluorescence intensity tend to decrease as the heater output increases, and there is a gap between the average value and the standard deviation of the fluorescence intensity as shown by the straight line Rx. There is a relationship that changes approximately in direct proportion. However, when the heater output becomes excessively large, the relationship between the average value and standard deviation of the fluorescence intensity clearly deviates from the proportional relationship shown by the straight line Rx. In FIG. 8, as shown in the region Er, deviation from the proportional relationship is shown at 90% of the heater output, and it is estimated that there is an upper limit of the heater output between 80% and 90% of the heater output. .

In the example of FIG. 8, the average value of fluorescence intensity correlates with the average value of wall thickness when inspecting the entire circumference of the bottle. Therefore, the standard deviation correlates with the magnitude of variation in wall thickness in the circumferential direction of the bottle, and the greater the variation, the greater the standard deviation. As is clear from the example of the image in FIG. 6, the greater the degree of uneven thickness defect, the greater the average value of the fluorescence intensity of the bottle and the greater the standard deviation. Therefore, according to FIG. 8, the smaller the heater output is and the less the heating amount is, the more noticeable the uneven thickness defects appear, and as long as the heater output does not exceed the upper limit, the heating amount is compensated for by increasing the heater output. It can be confirmed that the variation in wall thickness has converged and uneven thickness defects are less likely to occur.

According to the above study, by determining the standard deviation of the fluorescence intensity appearing in the image of the bottle inspection area, it is possible to quantitatively understand the state of uneven thickness in the bottle inspection area. The standard deviation of fluorescence intensity is an example of an index value that quantitatively indicates the state of the distribution of fluorescence intensity in the inspection range, in other words, the degree of variation in fluorescence intensity, and is an objective and quantitative indicator of the state of uneven thickness. It can be used as a highly reliable test result. If there is a correlation like a straight line Rx between the average value of fluorescence intensity and the standard deviation, and if this relationship is known in advance, the distribution of fluorescence intensity can be quantified by the standard deviation, and the obtained standard deviation can be expressed as a straight line. The heater output may be adjusted (increased) so that it is reduced in accordance with the relationship of Rx and converged to an allowable range. According to this, it is possible to save labor in at least a part of the adjustment work of temperature control parameters, etc. for eliminating defective thickness unevenness, and to improve work efficiency. Furthermore, as illustrated in the region Er in FIG. 8, if the relationship between the average value of the fluorescence intensity and the standard deviation deviates from the predetermined correspondence relationship as shown by the straight line RX, the heater output exceeds the upper limit. For reasons such as this, there is a possibility that some kind of molding defect other than uneven thickness has occurred. For example, when the resin is heated excessively, stretching progresses excessively, and the molecular chains of the resin become oriented, resulting in increased density and crystallization, which may result in molding defects such as whitening. Therefore, it is also checked whether the relationship between the average value of the fluorescence intensity and the standard deviation deviates from a predetermined correspondence relationship (for example, a proportional relationship shown by the straight line RX), and if it deviates, it is examined. By outputting the results, it is also possible to check for molding defects such as whitening. Alternatively, it is possible to output as an inspection result not only the presence or absence of molding defects such as whitening, but also the fact that some abnormal state has occurred with respect to the blow molding conditions.

Returning to FIG. 1, the processing section 20 of the inspection device 1 will be explained. The processing unit 20 inspects the state of uneven thickness in the inspection range of the bottle 2 based on the distribution of fluorescence intensity in the image captured by the image acquisition unit 10. The processing unit 20 is configured using, for example, a computer unit including a CPU and an internal storage device necessary for its operation. The processing section 20 is provided with an image adjustment section 21 and an inspection section 22. The image adjustment section 21 and the inspection section 22 are provided as logical devices realized by, for example, a combination of the computer hardware of the processing section 20 and an inspection program PG, which is an example of a computer program as software. However, at least a portion of the processing unit 20 may be configured as a physical device combining logic circuits such as LSI. Note that the processing unit 20 may be connected to various input means such as a keyboard and a pointing device for the operator of the inspection apparatus 1 to input appropriate instructions. In FIG. 1, illustration of input means is omitted.

The image adjustment unit 21 receives the image signal output from the camera 13 and performs image processing suitable for the inspection by the inspection unit 22 to convert the image captured by the camera 13 into an image suitable for the inspection by the inspection unit 22. adjust. For example, the image adjustment unit 21 may perform correction processing for image brightness, contrast, and the like. The inspection section 22 receives the image signal processed by the image adjustment section 21 and inspects the state of uneven thickness in the inspection range of the bottle 2 . Thereby, the inspection section 22 functions as an example of inspection means.

The processing of the inspection unit 22 may be configured as appropriate as long as the state of uneven thickness is inspected based on the distribution of fluorescence intensity in the inspection range. For example, the inspection unit 22 calculates the standard deviation of the fluorescence intensity based on the distribution of fluorescence intensity in the image captured by the camera 13, thereby calculating the degree of variation in fluorescence intensity in the inspection range, in other words, the degree of variation in wall thickness. It is also possible to generate data quantitatively representing the test result, and display the obtained data on the monitor 23 as the test result, or store it in the storage device 24 as the test result. The means for outputting test results is not limited to the monitor 23 and the storage device 24, but a printer may be connected as the output means. The larger the variation in wall thickness, the larger the standard deviation. Therefore, a reference value for determining whether or not there is a thickness unevenness defect is set for the standard deviation, and the calculated standard deviation is compared with the reference value to determine whether or not there is an uneven thickness defect. It may also be carried out as an inspection of the state of uneven thickness.

The inspection result of the uneven thickness state generated by the inspection unit 22 is provided to the control device of the blow molding machine, and the parameters of the temperature adjustment means that affect the quality of blow molding are controlled in a direction to eliminate the uneven thickness state. good. For example, the output of a heater for heating the preform may be controlled according to the test results output from the test section 22. For example, when a specific location of the bottle 2 is set as the inspection range and there is a risk of uneven thickness in that range, an operation may be performed to increase the output of the heater at the location corresponding to the inspection range. The temperature adjustment means is not limited to a heater, but may be a cooling device that partially cools the mold, and may control the cooling conditions during blow molding in a direction that eliminates the uneven thickness state. Alternatively, the parameters of the operation of the stretch rod inserted into the preform during the blow molding process may be controlled. In any case, the processing of the inspection unit 22 yields inspection results that quantitatively indicate the state of uneven thickness, and the parameters of various molding conditions that affect the quality of blow molding are controlled by referring to the inspection results. It's okay to be.

FIG. 10 shows an example of a procedure for inspecting uneven thickness defects in the inspection section 22. In the inspection process, the inspection section 22 first obtains an image of the inspection range set on the bottle 2 from the camera 13 via the image adjustment section 21 (step S1). As described above, when only a part of the inspection range is captured in one imaging operation of one camera 13, the same camera 13 is operated repeatedly at a period synchronized with the rotation of the bottle 2. The image of the inspection range may be acquired by using the camera 13, or each of the images from a plurality of cameras 13 which share images of the inspection range may be acquired. Alternatively, the bottle 2 may be repeatedly imaged while the illumination device 11 and the imaging device 12 are moved around the bottle 2.

Next, the inspection unit 22 calculates an index value indicating the degree of variation in wall thickness in the inspection range based on the distribution of fluorescence intensity in the obtained image of the inspection range (step S2). In this process, for example, the image of the inspection range is divided into unit areas of appropriate size, the average value of the fluorescence intensity for each unit area is calculated, and the standard deviation of the obtained average value is calculated as the index value. good. Thereafter, the inspection unit 22 generates inspection data indicating the inspection result based on the calculated index value, and outputs this to the monitor 23 and the storage device 24 (step S3). In this case, in addition to the standard deviation, various information obtained from the image acquired in step S1, such as the average value of fluorescence intensity for each unit area and the maximum value of fluorescence intensity, are stored in the data in association with the index value. It's fine. The index value such as the standard deviation is compared with a predetermined determination value indicating a defective thickness unevenness, and the presence or absence of a defective thickness unevenness is determined in step S3, and the determination result may be included in the inspection data. When the relationship between the average value of fluorescence intensity and the standard deviation is known in advance, such as the straight line Rx in FIG. An appropriate value of the heater output for heating the preform may be calculated, and the adjustment amount of the temperature control parameter may be output as part of the inspection data. In addition to the temperature control parameters, various molding conditions that affect the degree of uneven thickness may be adjusted according to the inspection results. In addition, in step S3, it is also checked whether the relationship between the average value of the fluorescence intensity and the standard deviation deviates from a predetermined correspondence relationship as exemplified by the straight line RX. It may be output as part of the inspection results that there is a possibility that a molding defect such as the above has occurred or that some abnormality has occurred in the molding conditions.

As explained above, according to the inspection device 1 of the present embodiment, the inspection range of the bottle 2 to be inspected is illuminated with ultraviolet light from the illumination device 11, and an image of the bottle 2 emitting fluorescence is displayed in the wavelength range of the fluorescence. The camera 13 captures an image from the same side as the illumination direction of the ultraviolet light through the filter 14 so that the wavelength range of the ultraviolet light is included in the wavelength range of the imaged target while being excluded from the wavelength range of the imaged target. The state of uneven thickness in the inspection range of the bottle 2 can be inspected based on the distribution of fluorescence intensity in the image. According to such an inspection method, the uneven thickness of the bottle 2 can be inspected by image processing without depending on the operator's visual inspection, which improves inspection efficiency and provides an objective and highly reliable inspection method. It is possible to obtain test results. Note that when inspecting the uneven thickness of the bottom shown in Figure 5(b) or the misalignment shown in Figure 5(c), there may be areas where the fluorescence intensity locally increases even in a normal state with no uneven thickness. arise. If such a location is included in the inspection range of Bottle 2, the area that should appear as a bright area in the image during normal operation is determined in advance, and that area is excluded from the calculation of index values such as standard deviation. By applying processes such as determining the difference between the fluorescence intensity in normal conditions and the fluorescence intensity in the actual inspection range and calculating the standard deviation etc. from the obtained brightness/darkness distribution, bright areas that appear even in normal conditions can be calculated. It is possible to calculate the index value so as to exclude the influence and inspect the state of uneven thickness in the same manner as above.

The present invention is not limited to the above-mentioned embodiment, but can be applied to the inspection of uneven thickness in various resin molded products formed by blow molding. Furthermore, the excitation light used for illuminating the resin molded product is not limited to ultraviolet light. The excitation light only needs to be able to emit light in a wavelength range different from the wavelength range of the irradiated light from the resin molded product, and the excitation light that can emit Raman scattered light as the detection target light is used for illumination. May be used for. Therefore, the excitation light is not limited to the ultraviolet range, but may include the visible light wavelength range. In any case, if the wavelength range of the detection target light is different from that of the excitation light and it is possible to capture an image of the detection target light while excluding the image of the excitation light wavelength range, the excitation light and the detection target light can be separated. The combination may be changed as appropriate. The material for the resin molded product is not limited to PET resin, but various resins can be used as long as they can be used as blow molding materials and emit light in a wavelength range different from the excitation light as the detection target light when irradiated with the excitation light. A material may be used as a material. Furthermore, the resin molded products to be inspected are not limited to bottle-shaped containers, and resin molded products for various uses may be inspected as long as they are formed by blow molding.

In the above configuration, the standard deviation of the fluorescence intensity was determined as an index value that quantitatively indicates the degree of variation in the intensity of the detection target light, but when inspecting the state of uneven thickness, the degree of variation in wall thickness is objectively determined. Various index values may be determined as long as they can be determined. For example, instead of or in addition to the standard deviation, various values used statistically as values indicating the degree of dispersion, such as variance, may be obtained. In the above embodiment, the state of uneven thickness is grasped by the degree of variation in the intensity of the detection target light, and the degree of variation is expressed quantitatively by index values such as standard deviation. However, the method for inspecting the state of uneven thickness is This is not the only example. The method of expressing the degree of variation using an index value is an example of a method of inspecting the state of uneven thickness based on the intensity distribution of the light to be detected, and the state of uneven thickness may be inspected using any other appropriate method. is possible. For example, the intensity distribution of the detection target light in a normal resin molded product that is judged to have no uneven thickness defects is prepared as the reference data, and the intensity distribution of the detection target light in the image acquired in the actual inspection is used as the reference data. By comparing with data and determining whether or not the difference in intensity distribution exceeds an allowable range, it may be inspected whether or not a thickness deviation exceeding an allowable range has occurred. A graph or other data that visualizes the intensity distribution of the light to be detected may be generated and output as the inspection results without determining the presence or absence of uneven thickness defects. In any case, the intensity distribution of the detection target light correlates with the wall thickness distribution of the resin molded product in the inspection range, so by using that correlation, the state of uneven thickness can be evaluated based on the intensity distribution. Is possible.

In the above embodiment, the imaging device 12 including the camera 13 is used as the imaging means, but the imaging means is not necessarily limited to an example using a camera. In the inspection of the present invention, if data representing the signal intensity corresponding to the intensity of the detection target light in the inspection range of the resin molded product can be obtained, uneven thickness can be detected based on the intensity distribution of the detection target light indicated by the data. It is possible to check the condition. Therefore, data that reflects the intensity of the detection target light is obtained using various sensors that output detection signals according to the intensity of the detection target light, and based on the intensity distribution of the detection target light in the obtained data. The state of uneven thickness may be inspected. For example, data indicating the intensity distribution of the detection target light in the inspection range may be acquired using a light intensity sensor having a two-dimensional planar detection range. Alternatively, data indicating the intensity distribution of the detection target light in the inspection range may be acquired by scanning the inspection range with a one-dimensional light intensity sensor (line sensor). The data acquired in this manner is substantially equivalent to the image data acquired by the camera 13 of the above configuration in that it has a signal intensity that corresponds to the intensity distribution of the detection target light. Therefore, such data is also included in the concept of "image" in the present invention, and a detection device using various sensors for acquiring such data is included in the concept of "imaging means" in the present invention. It is included in

Various aspects of the present invention derived from each of the embodiments and modifications described above will be described below. In the following description, in order to facilitate understanding of each aspect of the present invention, corresponding components illustrated in the accompanying drawings will be added in parentheses, but the present invention is not limited to the illustrated form. It's not something you can do.

A resin molded product inspection method according to one aspect of the present invention is a resin molded product inspection method for inspecting the state of uneven thickness in a blow-molded resin molded product (2), and includes the following: A procedure for illuminating an inspection range of the resin molded product with excitation light that can be emitted from the resin molded product using light in different wavelength ranges as detection target light, and the resin molded product illuminated with the excitation light. imaging the inspection range in such a way that the wavelength range of the detection target light is included in the wavelength range of the imaging target, while the wavelength range of the excitation light is excluded from the wavelength range of the imaging target; and and a step of inspecting the state of uneven thickness in the inspection range based on the intensity distribution of the detection target light in the image.

A resin molded product inspection device (1) according to one aspect of the present invention is a resin molded product inspection device that inspects the state of uneven thickness in a blow-molded resin molded product (2), and is configured to illumination means (11) for illuminating an inspection range of the resin molded product with excitation light that can emit light in a wavelength range different from the wavelength range from the resin molded product as detection target light; The inspection range of the illuminated resin molded product is configured such that the wavelength range of the detection target light is included in the wavelength range of the imaging target, while the wavelength range of the excitation light is excluded from the wavelength range of the imaging target. an imaging means (12) for taking an image, and an inspection means (22) for inspecting the state of uneven thickness in the inspection range based on the intensity distribution of the detection target light in the captured image and outputting an inspection result. , it includes.

A computer program (PG) according to one aspect of the present invention is a resin molded product inspection device (1) that inspects the state of uneven thickness in a blow-molded resin molded product (2), illumination means (11) for illuminating an inspection range of the resin molded product with excitation light that can emit light in a wavelength range different from the wavelength range from the resin molded product as detection target light; and illumination with the excitation light. The inspection range of the resin molded product is set such that the wavelength range of the detection target light is included in the wavelength range of the imaging target, while the wavelength range of the excitation light is excluded from the wavelength range of the imaging target. A computer program that is applied to an inspection apparatus that includes an image capturing means (12) that captures an image, the computer (20) of the inspection apparatus having an image capturing means (12) that acquires an image captured by the image capturing means. 22, S1), and inspection means (22, S2, S3) for inspecting the state of uneven thickness in the inspection range based on the intensity distribution of the detection target light in the acquired image, and outputting the inspection result; It is configured to function as

When a blow-molded resin molded product is illuminated with excitation light, detection target light having a wavelength range different from that of the excitation light is emitted from the resin molded product in response to the illumination. The intensity of the light to be detected increases as the thickness of the resin increases. Therefore, the intensity distribution of the detection target light in the image reflects variations in the thickness of the resin molded product in the inspection range. Therefore, according to the above aspect, it is possible to grasp the state of uneven thickness using the intensity distribution of the detection target light as a clue. Since the state of uneven thickness can be inspected by image processing without relying on the operator's visual observation, inspection efficiency can be improved and objective and highly reliable inspection results can be obtained.

In the above aspect, the excitation light may be, for example, ultraviolet light, and the detection target light may be fluorescence generated in the resin molded product. In the inspection procedure, an index value quantitatively indicating the degree of variation in the intensity of the detection target light may be calculated. Furthermore, in the inspection procedure, a standard deviation of the intensity of the detection target light in the inspection range may be calculated as the index value. The same applies to the processing of the inspection means. By calculating the standard deviation, which quantifies the degree of variation in the intensity of the light to be detected, as an index value, the state of uneven thickness can be objectively indicated, and objective information can be used to adjust molding conditions such as the resin heating temperature during molding. It is possible to provide test results that serve as a guideline.

In the inspection procedure, it may also be inspected whether the relationship between the average value of the intensity of the detection target light in the inspection range and the standard deviation deviates from a predetermined correspondence relationship. The same applies to the processing of the inspection means. A correspondence relationship may be observed between the average value and standard deviation of the intensity of the light to be detected, such that the worse the uneven thickness is, the larger the average value and standard deviation become. However, if molding defects such as whitening occur or are likely to occur due to inappropriate molding conditions, the relationship between the average value and standard deviation may deviate from such a correspondence relationship. There is. Therefore, by including in the inspection whether the relationship between the average value of the intensity of the detection target light and the standard deviation deviates from the predetermined correspondence relationship, it is possible to check whether or not other molding defects have occurred in addition to the state of uneven thickness. It is possible to obtain information as inspection results to determine whether or not there is a risk of such occurrence, and whether the molding conditions are appropriately set.

1 Inspection device 2 Bottle (resin molded product)
11 Lighting device (lighting means)
12 Imaging device (imaging means)
13 Camera 14 Filter 20 Processing unit (computer)
22 Inspection Department (Inspection Means)
D1, D2 Uneven thickness portion D3 Misalignment portion

Claims (15)

A resin molded product inspection method for inspecting the state of uneven thickness in a blow molded resin molded product, the method comprising:
a step of illuminating an inspection range of the resin molded product with excitation light that can emit light in a wavelength range different from the wavelength range of the irradiated light from the resin molded product as detection target light;
The inspection range of the resin molded product illuminated with the excitation light is such that the wavelength range of the detection target light is included in the wavelength range of the imaging target, and the wavelength range of the excitation light is outside the wavelength range of the imaging target. a procedure for taking an image while excluding the
A step of inspecting the state of uneven thickness in the inspection range based on the intensity distribution of the detection target light in the captured image;
Inspection method for resin molded products containing 2. The method for inspecting a resin molded product according to claim 1, wherein in the inspection step, an index value quantitatively indicating the degree of variation in intensity of the detection target light is calculated. 3. The method for inspecting a resin molded product according to claim 2, wherein in the inspection step, a standard deviation of the intensity of the detection target light in the inspection range is calculated as the index value. The resin molding according to claim 3, wherein in the testing step, it is also tested whether the relationship between the average value of the intensity of the detection target light in the testing range and the standard deviation deviates from a predetermined correspondence relationship. Product inspection method. The method for inspecting a resin molded article according to any one of claims 1 to 4, wherein the excitation light is ultraviolet light and the detection target light is fluorescence generated in the resin molded article. A resin molded product inspection device that inspects the state of uneven thickness in a blow molded resin molded product,
illumination means that illuminates an inspection range of the resin molded product with excitation light that can cause the resin molded product to emit light in a wavelength range different from the wavelength range of the irradiated light as detection target light;
The inspection range of the resin molded product illuminated with the excitation light is such that the wavelength range of the detection target light is included in the wavelength range of the imaging target, and the wavelength range of the excitation light is outside the wavelength range of the imaging target. an imaging means for taking an image in such a manner that the
Inspection means for inspecting the state of uneven thickness in the inspection range based on the intensity distribution of the detection target light in the captured image, and outputting an inspection result;
Inspection equipment for resin molded products including The resin according to claim 6, wherein the inspection means calculates an index value quantitatively indicating the degree of variation in intensity of the detection target light, and generates and outputs data indicating the inspection result based on the calculation result. Molded product inspection equipment. 8. The resin molded product inspection apparatus according to claim 7, wherein the inspection means calculates a standard deviation of the intensity of the detection target light in the inspection range as the index value. The resin molded article according to claim 8, wherein the inspection means also inspects whether the relationship between the average value of the intensity of the detection target light in the inspection range and the standard deviation deviates from a predetermined correspondence relationship. inspection equipment. The inspection device for a resin molded article according to any one of claims 6 to 9, wherein the excitation light is ultraviolet light, and the detection target light is fluorescence generated in the resin molded article. A resin molded product inspection device for inspecting the state of uneven thickness in a blow molded resin molded product, wherein light in a wavelength range different from the wavelength range of the irradiated light is emitted from the resin molded product as detection target light. an illumination means for illuminating an inspection range of the resin molded product with excitation light that can illuminate the inspection range of the resin molded product illuminated with the excitation light; A computer program that is applied to an inspection apparatus, the computer program comprising: an imaging means that captures an image in such a way that the wavelength range of the excitation light is included in the wavelength range of the imaging target, while being excluded from the wavelength range of the imaging target,
The computer of the inspection device,
an image acquisition unit that acquires an image captured by the imaging unit; and an image acquisition unit that inspects the state of uneven thickness in the inspection range based on the intensity distribution of the detection target light in the acquired image, and outputs an inspection result. A computer program configured to function as a testing means. The computer according to claim 11, wherein the inspection means calculates an index value quantitatively indicating the degree of variation in intensity of the detection target light, and generates and outputs data indicating the inspection result based on the calculation result. program. 13. The computer program according to claim 12, wherein the inspection means calculates a standard deviation of the intensity of the detection target light in the inspection range as the index value. 14. The computer program product according to claim 13, wherein the inspection means also inspects whether the relationship between the average value of the intensity of the detection target light in the inspection range and the standard deviation deviates from a predetermined correspondence relationship. The computer program according to any one of claims 11 to 14, wherein the excitation light is ultraviolet light, and the detection target light is fluorescence generated in the resin molded product.

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