JPS6345284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a quality control method for plastic molded products, and in particular, to a method for controlling the quality of plastic molded products, and in particular, by installing practically unnecessary protrusions on plastic molded products and measuring the breaking strength of the protrusions, the quality of the molded products can be determined. Regarding how to manage.

Conventionally, quality control of plastic molded products has mainly been based on nondestructive inspections such as checking the quality of appearance and measuring dimensions, and strength has been statistically estimated from destructive tests using samples. However, with this method, the molded product becomes unusable after the destructive test.
They must be discarded, and there is a risk that the shipped items will contain defective items, depending on the number of items sampled from the population. In addition, when a product that fails a sample test is found, the inspection requires a detailed study of the population, which takes a long time. In particular, in the case of plastic, if it is left in a heated state for a long time in the cylinder of an injection molding machine, it may deteriorate and its strength may decrease. In such a case, the plastic in the cylinder is discarded, but if something that should have been discarded accidentally remains in the cylinder or if it is not disposed of sufficiently, a defective product is produced. However, such defective products are difficult to detect by non-destructive inspections such as appearance and dimensions, and may not be detected by destructive sampling tests, which may result in accidents in the market.

The purpose of the present invention is to improve the drawbacks of the prior art as described above, and to provide a quality control method for plastic molded products that does not render the molded products unusable as a result of testing and that allows all products to be inspected. That is.

The main points of the present invention will be explained using examples.

The present invention eliminates a practically unnecessary protrusion 1 from a plastic molded product such as the conventional example shown in FIG.
As in the embodiment shown in the figure, the plastic molded product is integrally molded, the protrusions are broken, and the quality of the plastic molded product is controlled from the breaking strength or the condition of the broken surface. In particular, it is desirable to install the protrusion at the end of the molded product, where internal strain is likely to occur and strength problems are likely to occur. Also, the third
As in the embodiment shown, a hole 3 is provided at the end of the protrusion 2 to create a weld line caused by the fusion of plastic flows behind flow obstacles during molding flow. It is desirable to generate a weld line 4, which is generally considered to have low strength, so that the breaking strength of the weld line can be measured.

Note that the shape of the molded product and the shape and position of the protrusions are not limited to the above embodiments. Furthermore, since the condition of the fractured surface of plastic changes as it deteriorates, quality can also be controlled by observing the condition of the fractured surface. For example, rubber reinforcing resins such as acrylonitrile-butadiene rubber-styrene copolymer, styrene-butadiene rubber copolymer, acrylonitrile-ethylene propylene rubber-styrene copolymer, acrylonitrile-acrylic rubber-styrene copolymer, polyethylene,
Thermoplastic resins such as olefin resins such as polypropylene are known to have a whitening phenomenon in which the fractured surface becomes white, but as this phenomenon becomes less likely to occur due to deterioration, deterioration can also be detected from this whitening state. It is possible.

Here, any method of destructive testing is acceptable as long as the strength can be detected, and there are many test methods such as constant speed deformation, constant load deformation, impact, repeated loading, and continuous loading. The same goes for observing the state of whitening; in this case, even if you cut it out with pliers, nippers, etc., the whitening phenomenon will be observed. Further, the number of protrusions is not limited to one, and may be increased as necessary. Further, the cross-sectional shape and dimensions of the protrusion are not particularly limited.

According to the present invention, the strength is detected by destroying protrusions that are unnecessary for practical use, so the test does not render the molded product unusable. Therefore, inspection of all products is also possible. In addition, as testing methods, impact, cutting with pliers or nippers, etc. can be used, and since partial destruction is required, strength can be evaluated in a short time. Therefore,
Inspection time can be shortened and defective products can be prevented from appearing on the market.

As shown in FIG. 4, a projection may be provided on the boss 5 of the molded product.

As shown in FIG. 5, protrusions may be provided on the ribs 6 of the molded product.

As shown in Figure 6, in place of the protrusion,
An unnecessary hole 7 is provided at a position where it would be no problem even if there were a hole, a weld line 8 was created at a position where it would be practically impossible to destroy the weld line 7.
The breaking strength may also be measured. Here, the shape of the hole 6 is not particularly limited to a circular shape.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a conventional embodiment, Fig. 2 is a perspective view of an embodiment according to the present invention in which an unnecessary protrusion is installed, and Fig. 3 is a hole installed at the end of an unnecessary protrusion to generate a weld line. FIG. 4 is a perspective view of a modified example of the present invention in which an unnecessary protrusion is installed at the end of the boss of a molded product, and FIG. 5 is a perspective view of an example in which an unnecessary projection is installed at the end of the rib of the molded product. Perspective view of a modification of the invention, No. 6
The figure shows a perspective view of a modification of the invention in which holes are provided instead of protrusions. 1... Practically unnecessary protrusion, 2... Protrusion with a hole, 3
... Hole at the end of the protrusion, 4... Weld line, 5... Boss, 6... Rib, 7... Unnecessary hole.

Claims (1)

[Scope of Claims] 1. Quality of a plastic molded product characterized by integrally molding a practically unnecessary protrusion into a plastic molded product, destroying the protrusion, and controlling the quality from its breaking strength or the state of the fractured surface. Management law. 2. A method for quality control of plastic molded products according to claim 1, characterized in that the protrusion is installed at the end of the flow of molten metal during molding of the molded product. 3. A method for quality control of plastic molded products according to claims 1 and 2, characterized in that the molding is performed so that holes are formed at the ends of the protrusions.