JPS58145429A - Treatment of plastic injection molding with metal insert - Google Patents

Abstract

PURPOSE:To reduce the amount of residual strain for preventing the occurence of cracks and deformation by a method in which the resin in contact with the metal insert of a plastic injection molding having the metal insert inside is remelted and allowed to cool naturally. CONSTITUTION:The resin in contact with the outside of a metal insert 1 is melted by the metal insert 1 heated by induced current through a coil 6 wound around the outside of the resin portion 2 of a molding 3 in such a way as to alleviate the residual strain of the resin. Then, heating is rapidly stopped to cool it naturally. In the coil 6, an alternate magnetic field is formed by the action of a high-frequency current generator 7 to generate induced current in the metal insert 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a processing method for reducing residual strain in plastic injection molded articles having metal inserts.

When injection molding is performed by inserting metal into a plastic injection molded product, large distortions may remain in the plastic around the metal insert due to the difference in thermal expansion coefficient during the cooling process after injection of molten resin. many. For example, in the case of aluminum inserts, the coefficient of thermal expansion of aluminum is 2.3 x 10'-5/c, and that of general plastic is 6 to 12 x 10'-5/c.
The difference becomes residual strain. This residual strain is the force necessary to hold the insert, but if the level is too large.

Problems such as cracks and deformation occur in the molded product.

The present invention was proposed for the purpose of eliminating the problems caused by the above-mentioned residual strain, and the present invention is made by heating the metal insert of a plastic injection molded product having a metal insert with an appropriate heating means to raise the temperature. The present invention relates to a method for processing a plastic injection molded product having a metal insert, which is characterized in that the resin in the portion in contact with the resin portion is remelted and then allowed to cool naturally.

Hereinafter, one embodiment of the method of the present invention will be specifically explained with reference to the accompanying drawings.

FIG. 1 shows an example of a plastic injection molded article having a metal insert treated by the method of the present invention. 3 is formed by inserting the metal (aluminum) insert 1 into the pin 4a of the female mold 4, closing the male mold 5, and injecting molten plastic (ABS resin) into the mold, as shown in FIG. be done. The molded article 3 obtained by K in this manner is as follows.

As mentioned earlier, due to the difference in thermal expansion coefficient between the metal (aluminum) insert 1 and the ABS resin, a large strain remains in the ABS resin 2 at the interface with the metal insert 1, causing cracks and deformation in the molded product B. Therefore, the residual strain is reduced as shown in FIG. In the same figure, 6
is a coil wound around the outer periphery of the ABS resin part of the molded product 6 as shown in the figure, and a high frequency current generator 7 is interposed between both ends of the coil 6.
, an alternating magnetic field is formed in the coil 6 and an induced current is generated in the metal insert 1. Due to this induced current and Joule loss due to the resistance of the metal concert 1, the metal insert 1 is heated and its temperature increases.

This heat simultaneously propagates to the part of the ABS resin 2 in contact with the outer periphery of the metal insert 1, raises the temperature of that part, remelts it, and causes A
Reduces residual strain in BS resin 2. After that, heating is immediately stopped and the product is allowed to cool naturally.

One embodiment of the treatment method of the present invention is configured as described above, and when the treatment method is applied to a plastic injection molded product having a metal insert, the residual strain of the molded product can be easily reduced. This has the practical effect of eliminating the risk of cracks or deformation occurring in the molded product.

Next K shows experimental data regarding the method of the present invention.

Aluminum insert 1 inner diameter 10φ, outer diameter 24
First, the residual strain of the injection molded product 3 made of ABS resin 2 with an outer diameter of 32φ is measured using a strain gauge as shown below.
K and measured. That is, as shown in FIG. 4, the strain cage 8 is attached to the upper end surface of the ABS resin 2 of the molded product 3 with an adhesive, and the input voltage eiQ is applied through the bridge 9, R, Ho, and the strain gauge Adjust and fix the resistors R1, R2, and R3 of the bridge 9 so that the output voltage of the bridge 8 becomes zero. Next, with the strain gauge 8 attached as shown in Figure 5, the upper end surface of the ABS resin was cut out to be slightly thicker than the strain gauge 8, and the output voltage of the strain gauge 8 at that time was measured. , by converting the output power e into the amount of strain, we measured the amount of residual strain in molded product 3, and found that there was a residual strain of 0.61%, whereas the same part of the molded product after treatment according to the present invention had a residual strain of 0.61%. The residual strain is 0.15
%, and it was confirmed that the distortion was reduced by 0.16%.

In addition, in the above embodiment, a case was described in which the molded product is heated by high-frequency heating means to remelt the interface between the metal insert and the resin and reduce residual strain. is not limited to high-frequency heating (although any other appropriate heating means may be used as long as it is capable of re-melting the interface portion).

In summary, 1. the present invention is to heat the metal insert of a plastic injection molded product having a metal insert (V) with an appropriate heating means to raise the temperature so that the resin in the part where the metal insert contacts the resin part is remelted. 1. According to the present invention, the amount of residual strain in a plastic injection molded product having a metal insert can be reduced. The practical effect of this method is that it is possible to easily obtain a VC molded product without the risk of cracking or deformation.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an example of a plastic injection molded product having a metal insert, FIG. 2 is an explanatory diagram of the molding procedure for the molded product, and FIG. 4 and 5 are explanatory diagrams of an example of a method of measuring residual and strain of a molded product. 1: Metal insert, 2: Resin part, 3: Injection molded product, 4: Female mold, 5: Male mold, 6: Coil. 7: High frequency, current generator. Procedural Amendment Statement March 811, 1981 Haruki Shimada, Commissioner of the Patent Office 1, Indication of the Case 1988 Patent Application No. 27288 0 Title of Invention Method for Processing Plastic Injection Molded Articles Having Metal Insertion 3, Amendment Relation to the case of a person who does Toramon-chome 2-29-7, Miyakominato-ku
, Contents of the amendment, and the content of the amendment) The scope of the claims is amended as shown in the attached sheet. (2) "Dissolution" on page 2, line 13, page 5, lines 12 and 15, and page 6, line 1, is corrected to "melting". [Claims] After heating the metal insert of a plastic injection molded product having a metal insert to raise the temperature using an appropriate heating means to remelt the resin in the part where the metal insert contacts the resin part, A method for processing a plastic injection molded product having a metal insert, which is characterized by natural cooling.

Claims (1)

[Claims] The metal insert of a plastic injection molded product having a metal insert is heated to raise the temperature using an appropriate heating means to remelt the resin in the part where the metal insert contacts the resin part, and then the resin is allowed to cool naturally. A method of processing plastic injection molded parts with metal inserts.