JPH0441644B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field Related to the Invention) This invention relates to a method for forming narrow grooves that are essential when locally electrodepositing the surface of a cylindrical non-conductive article such as a synthetic resin. It is related to.

(Prior Art) One method of locally electrodepositing the surface of a non-conductive article is described in Japanese Patent Publication No. 45-37843. This direction can be summarized as follows. 6th
In the figure, a is, for example, the cutting angle α and the depth.
A cross section of a mm notch is shown. A non-conductive article provided with such a notch is coated with a uniform layer b on the inside of the notch a by electroless plating as shown in FIG. When plating is then carried out in an electroplating bath, the metal c at the sharp internal corner portions will be dissolved in the electrolyte, and the current density at such portions will be too low to electrodeposit the metal. Since the current is thus cut off at this part, only the left surface of the notch a connected to the power supply is covered with a metal layer d, as shown in FIG.
That is what it is.

It is difficult to select the cutting depth and cutting angle α of such a notch a. It would be undesirable if the angle α was too large, and it would be undesirable if the angle α was too shallow, and it was not easy to form such a notch.

(Problems to be Solved by the Invention) The present invention provides a notch, which is essential in the direction of electrodeposition as described above, when molding a cylindrical non-conductive article, at the same time as drawing it out at the time of demolding. Provided is a method for forming a narrow V-shaped notch that opens upwardly between a small diameter portion, and facilitates the forming of the notch, which is essential for localized electrodeposition of non-conductive articles. The aim is to reduce costs.

(Means for solving the invention) A mold for injection molding has a large diameter hole, a small diameter hole concentric with the large diameter hole, and an annular V provided between the large diameter hole and the small diameter hole.
The annular V-shaped groove has a horizontal surface that extends from the peripheral wall of the small diameter hole in a direction substantially perpendicular to the axis, and a horizontal surface that projects obliquely upward from the peripheral wall of the large diameter hole and forms an acute angle β. The annular V-shaped groove is filled when the non-conductive resin is injection molded into the mold and then pulled out from the large diameter hole side to remove the mold. The annular protrusion was squeezed in the axial direction from the large diameter hole of the mold and forcibly removed from the mold to form a narrow upwardly opening V-shaped notch between the annular protrusion and the small diameter part.

(Example) FIG. 1 shows a part of an injection mold used in the method of the present invention. This is a partial view of a mold for molding a columnar part A of a molded product (for example, a knob for an electrical appliance) as shown in FIG. 2, and a V-shaped notch B is formed at the base of the columnar part A. Then, it is locally electrodeposited on the columnar part A at the top of this V-shaped notch.

In Fig. 1, 1 is a large diameter hole of the mold, 2 is a small diameter hole, and 3 is an annular V between the large diameter hole 1 and the small diameter hole 2.
It is a shape groove. As an example, the large diameter hole 1 and the small diameter hole 2 shown in FIG. 2 have a diameter difference of 2δ. The V-shaped groove 3 has a horizontal surface 3a extending substantially perpendicularly to the axis 4 of the small diameter hole 2 and an inverted conical surface 3 extending obliquely upward from the peripheral wall of the large diameter hole 1 and matching the horizontal surface 3a at an acute angle β.
It is composed of b.

The angle β between the horizontal surface 3a and the conical surface 3b is such that when the molded product is pulled out to the larger diameter side and demolded, as will be described later, the mold is forcibly demolded to form a narrow V-shaped notch that opens upward. With this V-shaped notch, the optimum angle is selected depending on the molding material to achieve ideal localized electrodeposition.

In addition, although the difference δ between the radii of the large-diameter hole 1 and the small-diameter hole 2 and the dimensions of the V-shaped groove 3 are exaggerated in the figure, the "knob" of the electrical product as shown in Fig. 2 is extremely small. , the diameter d of the small diameter hole 2 is 1.8 mm, the diameter D of the large diameter part 1 is 2 mm, so δ is about 0.1 mm, and the protrusion dimension of the annular V-shaped groove 3 provided therein is also very small. .

Also, the diameters D, d, etc. of the large diameter hole 1 and the small diameter hole 2, etc. are also selected in advance through experiments at their optimum values depending on the type of resin, plating conditions, etc.

(Molding method) In the normal injection molding process, resin is completely filled into the mold by applying appropriate pressure, temperature, speed, and time in the injection process. In the cross-sectional view of FIG. 1, the annular V-shaped groove 3 is also completely filled with resin. After the cooling process, which is the next step, the mold opening process begins, and once the mold is completely opened, the final product ejecting process begins. The mold opening process will be illustrated and explained next.

As shown in Fig. 1, the annular protrusion filling the annular V-shaped groove 3 with a wide opening during the injection molding process is removed when the mold opening process is completed (at this time). The molded product has the temperature of the mold), 3rd
A V-shaped groove with a very narrow opening is formed by narrowing down as shown in FIGS.

(Effect of the invention) The tongue-like annular protrusion filled in the injection molding process is squeezed during the mold opening process to form a narrow V-shaped groove, making it possible to create an appropriate mold. Once set, it can be molded very easily. If you try to create a similar groove using other methods,
Not only is it extremely difficult to make the mold, but
It is certain that it is inferior in terms of cost, mold life, etc.

Since a V-shaped groove with such a narrow width can be easily formed, local electrodeposition on the surface of a cylindrical non-conductive article such as a knob can be carried out more easily and economically.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a mold for carrying out the method according to the invention. FIG. 2 is a sectional view of an article (knob of an electrical appliance) to which the method of the present invention is applied. Figures 3 to 5
The figure is an explanatory diagram of the molding method. 6 to 8 are explanatory diagrams of a known local electrodeposition method. In the figure, 1...large diameter hole (of the mold), 2...
Small diameter hole (in the mold), 3... annular V-shaped groove (in the mold),
3a...Horizontal surface, 3b...Inverted conical surface, 4... Axis center.

Claims (1)

[Claims] 1 A mold for injection molding consists of a large diameter hole 1, a small diameter hole 2 concentric with the large diameter hole 1, and an annular V-shaped groove 3 provided between the large diameter hole 1 and the small diameter hole 2, and the annular V-shaped groove 3
a horizontal surface 3a extending from the circumferential wall of the small diameter hole 2 in a direction substantially perpendicular to the axis; and an inverted conical surface 3b extending diagonally upward from the circumferential wall of the large diameter hole 1 and meeting the horizontal surface 3a at an acute angle β. After injection molding a non-conductive resin into this mold, when removing the mold by pulling it out from the large diameter hole 1 side while retaining the elasticity before complete cooling, the annular V-shaped groove By squeezing the annular protrusion filled in 3 through the large diameter hole 1 of the mold and forcibly demolding, a narrow upwardly opening V-shaped notch is formed between the annular protrusion and the small diameter part. A method for forming narrow grooves for locally electrodepositing the surface of a cylindrical non-conductive article.