JPH0862144A - Surface inspection method for molding - Google Patents

Abstract

PURPOSE: To obtain a surface inspection method for molding in which the surface of a molding can be inspected prior to painting. CONSTITUTION: A switch 22 is turned on to actuate an ultraviolet light 14 and to irradiate an objective molding 24 with ultraviolet rays 28. An inspector then observes the molding 24 placed in a housing 12 through a window 18 made in the top face of the housing 12. In this regard, a defective part on the surface of the molding 24 looms in white but the ground color appears as it is at other parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded product surface for inspecting the surface of a molded product made of a synthetic resin for defects, particularly deterioration of the synthetic resin due to thermal decomposition before coating the surface of the molded product. It relates to the inspection method.

[0002]

2. Description of the Related Art Conventionally, when a synthetic resin molded article is produced by injection molding, and the surface of the molded article is coated, a water resistance test in which it is immersed in warm water for a predetermined number of days is performed. Blister (coating swelling; a phenomenon in which the coating film floats or peels off) may occur in the part where the coating film is formed.

The occurrence of such blister is caused by a defect on the surface of the molded product.
In particular, deterioration due to thermal decomposition of the synthetic resin can be mentioned.

For example, when a molded product of synthetic resin is produced by injection molding using a hot runner die, if the temperature of the hot runner portion of the hot runner die is higher than the appropriate temperature, the resin passes through that portion. At times, thermal decomposition occurs, and when the thermally decomposed resin appears on the surface of the molded article, the above-mentioned problems occur. For example, when the synthetic resin is aromatic nylon, its softening temperature is about 2
Although it is 70 ° C. to 280 ° C., when the heating temperature is about 300 ° C. or higher, the aromatic nylon causes thermal decomposition.

Even when the temperature of the hot runner portion is an appropriate temperature, when the resin stays in the hot runner portion due to the operation stop of the injection molding machine or the like and the staying time becomes long, the stayed resin is The above problem also occurs when the resin is heated to cause thermal decomposition and then the operation of the injection molding machine is started and the thermally decomposed resin appears on the surface of the molded product.

Such a defect on the surface of the molded product, that is, deterioration due to thermal decomposition of the synthetic resin does not appear as a change in the shape of the surface of the molded product or a change in color and luster, but rather the crystallinity of the synthetic resin. Since it appears as a decrease or a decrease in molecular weight, it cannot be easily detected by human eyes or touch.

[0007]

As described above, if the surface of the molded product is defective, the strength of the coating will be reduced at the defective portion when the surface is coated, and the surface will not be exposed to water for a long time. When exposed to the like, the above-mentioned blisters may occur on the surface.

However, as described above, the surface defect of the molded product, that is, the deterioration due to the thermal decomposition of the synthetic resin, cannot be easily detected by human eyes or tactile sensation. It was not possible to detect whether or not there was a defect on the surface of the molded product until a blister was confirmed on the surface of the molded product after the coating was applied to the product and a water resistance test was performed.

That is, conventionally, even if there is a defect on the surface of a molded product, it can be detected only after coating the surface of the molded product and conducting a water resistance test, that is, after molding. Since at least a predetermined number of days have passed since then, there was a problem that until that time, it was not possible to take measures to solve the defect.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to apply the coating to the surface of the molded product,
It is an object of the present invention to provide a method for inspecting the surface of a molded product, which is capable of inspecting the surface of the molded product for defects.

[0011]

In order to achieve the above-mentioned object, the invention according to claim 1 is a method for inspecting the surface of a molded article for inspecting the surface of the molded article made of synthetic resin for defects. In the above, the surface of the molded article before coating is irradiated with ultraviolet rays, and the presence or absence of defects on the surface is inspected based on the difference in color of each part of the surface at the time of irradiation.

That is, if a defect occurs on the surface of the molded product, when ultraviolet rays are irradiated, the defective part appears, for example, as white, and the non-defective part remains the ground color. appear. Therefore, it is possible to easily inspect whether or not there is a defect on the surface of the molded product by human eyes.

In the invention described in claim 1, ultraviolet rays mean electromagnetic waves in a wavelength range of about 1 nm to about 400 nm, and colors mean those expressed by attributes of hue, brightness and saturation. Examples of the above-mentioned synthetic resin constituting the molded product include thermoplastic resins such as polyamide (nylon), polyethylene, polypropylene, vinyl chloride resin, polystyrene, ABS, methacrylic resin, polycarbonate, polyacetal, thermoplastic polyester, and fibrin. Based plastics, phenylene oxide resin, fluororesin, etc. are considered.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the configuration of a molded product surface inspection device used when inspecting the surface of a molded product for defects by the molded product surface inspection method as one embodiment of the present invention.

The molded product surface inspection apparatus 10 shown in FIG. 1 mainly comprises a housing 12, and an ultraviolet light 14 and an ultraviolet filter 16 mounted on the upper surface of the housing 12.

An alternating current power source 20 is connected to the ultraviolet light 14 via a switch 22, and when the switch 22 is turned on, the ultraviolet light 14 emits light, toward the inside of the housing 12, for example, Ultraviolet rays 28 having a wavelength of about 366 nm are irradiated.

Further, the ultraviolet filter 16 is provided in the eye 2 of the inspector.
The purpose is to protect 6 from ultraviolet rays, and the ultraviolet rays reflected inside the housing 12 are blocked, but visible light from the inside of the housing 12 passes through.

Further, a door 12a rotatable in the direction of arrow A is provided on the side surface of the housing 12, so that the molded product 24 to be inspected can be taken in and out of the housing 12. There is.

Now, the method for inspecting the surface of the molded article of this embodiment will be described with reference to FIG. First, the molded product 24 to be inspected is prepared. As the molded product 24, a synthetic resin molded product produced by injection molding using a hot runner mold, which is not yet coated, is prepared.

Next, the inspector opens the door 12a of the housing 12 and sets the prepared molded product 24 at a predetermined position on the bottom surface of the housing 12. Thereafter, the switch 22 is turned on to cause the ultraviolet light 14 to emit light, and the molded product 24 to be inspected is irradiated with ultraviolet rays 28, so that the inspector can view the inside of the housing 12 through the observation window 18 on the upper surface of the housing 12. Peep and observe the molded product 24.

When the observation is completed, the switch 22 is turned off to stop the emission of the ultraviolet light 14, the inspector opens the door 12a of the housing 12, and the molded product 24 inside the housing 12 is taken out.

FIG. 2 is a perspective view showing a state of the surface of the molded product 24 observed in a normal state and a state of the surface of the molded product 24 observed during irradiation of ultraviolet rays.

FIG. 2A shows the appearance of the surface of the molded product 24 observed in a normal state (that is, in visible light). As described above, for example, a defect on the surface of the molded product 24,
That is, even if there is deterioration due to thermal decomposition, it cannot be detected by the inspector's eye 26 in a normal state, so as shown in FIG. Both the color and luster look uniform.

FIG. 2B shows the appearance of the surface of the molded product 24 observed during the irradiation of ultraviolet rays. The surface of the molded product 24 is irradiated with ultraviolet rays 28, and the surface is irradiated with the ultraviolet filter 16
2B, the surface color is divided into a white portion W and a ground color portion N, as shown in FIG. 2B. Of these, the white portion W is a defect, that is, a portion that is deteriorated by thermal decomposition, and the other ground-colored portion N is a portion that is not defective. In FIG. 2B, the boundary between the white portion W and the ground color portion N is clearly drawn, but in reality, the color may gradually change at the boundary portion.

By the way, the reason why the portion where the deterioration due to the thermal decomposition appears to appear white is that the optical property of the resin in the portion changes due to the thermal decomposition and the fluorescent reaction is caused. It is thought that this is because it becomes as shown. That is, when the ultraviolet ray 28 is applied to a portion where deterioration due to thermal decomposition occurs, the portion emits fluorescence. Since the fluorescence is visible light, it passes through the ultraviolet filter 18 and reaches the inspector's eye 26.
As a result, it looks white to the inspector.

Also, looking at the actual trial results, when the surface of the molded product 24 is coated and subjected to a water resistance test, the portion where blisters occur on the surface of the molded product 24 is
It surely coincides with the above-mentioned part W that appears white.

FIG. 2C shows the appearance of the surface of another molded article 24 'observed during the irradiation of ultraviolet rays. In the case of this molded product 24 ′, since there is no defective portion on the surface thereof, even if the surface is irradiated with ultraviolet rays 28 and the surface is observed through the ultraviolet filter 16, it is possible to obtain the result shown in FIG. As shown in, the surface color is only the background color portion N, and the white portion W is not visible.

As described above, according to the molded product surface inspection method of this embodiment, it is possible to inspect the surface of the molded product for defects before the surface of the molded product is coated. Therefore, for example, if it is detected that the surface of the molded product has a defect as shown in FIG. 2B even immediately after the molding, a measure for eliminating the defect, for example, It is possible to immediately take measures such as controlling the temperature of the hot runner portion of the hot runner mold so as to be an appropriate temperature.

[0029]

As described above, according to the first aspect of the present invention, it is possible to inspect the surface of the molded product for defects before the surface of the molded product is coated. It is not necessary to wait for 10 days after molding as in the conventional case, and measures can be taken even when the surface of the molded product is defective immediately after molding.

According to the first aspect of the invention, the presence or absence of a defect is visually inspected by human eyes based on the difference in color of each portion of the surface, so that the inspection can be easily performed. Furthermore, since it suffices to irradiate ultraviolet rays to perform the inspection, the device used when carrying out the invention described in claim 1 has a simple structure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration of a molded product surface inspection device used for inspecting the surface of a molded product for defects by a molded product surface inspection method as one embodiment of the present invention.

FIG. 2 is a perspective view showing a state of a surface of a molded article 24 observed in a normal state and a state of a surface of a molded article 24 observed during irradiation of ultraviolet rays.

[Explanation of symbols]

 10 ... Molded product surface inspection device 12 ... Housing 12a ... Door 14 ... UV light 16 ... UV filter 18 ... Window 20 ... AC power supply 22 ... Switch 24, 24 '... Molded product 26 ... Eye 28 ... UV light

Claims (1)

[Claims] 1. A method of inspecting a surface of a molded article made of a synthetic resin for the presence or absence of defects, the method comprising: irradiating the surface of the molded article before coating with ultraviolet rays, A method for inspecting a surface of a molded article, which comprises inspecting whether or not there is a defect on the surface based on a difference in color of each part of the surface.