JPS6350103Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an injection mold that prevents stringing. More specifically, when thermoplastic resin is molded into a target object, so-called "stringing" occurs in which the molten resin is suspended in a thin thread between the sprue attached to the molded product and the cylinder nozzle of the injection molding machine. This relates to an injection mold that has been designed to avoid this problem.

When manufacturing objects from thermoplastic resin by injection molding, it has traditionally been necessary not only to shorten the molding cycle, but also to streamline and unmanned methods such as automatic removal of molded products from molds. It is. In such cases, the target molded product formed by the core and cavity of the mold is often attached to the movable mold side and opened. Many molded products are attached with sprue, which is cut from the molded product in a separate process.

When the molding cycle is shortened, the molten resin solidifies between the sprue of the molded product and the cylinder nozzle of the injection molding machine, and there is no time for it to break, so when the mold is opened,
Between the sprue of the molded product and the cylinder nozzle,
So-called stringing occurs in which the molten resin is suspended in the form of a thread. If stringing occurs, it will be difficult to automatically remove the molded product, the stringy resin will get caught in the dividing surface of the mold, damaging the mold core surface, cavity surface, etc. Problems such as getting caught in the split surface and causing burrs on the molded product occur frequently.

One way to prevent the above stringiness is to lower the cylinder temperature, nozzle temperature, etc. of the injection molding machine, but if you follow this method, weld lines may be noticeable on the molded product, or the appearance may be affected. This is undesirable because it may worsen the situation.

Another way to prevent the above stringiness is to install a backflow prevention valve in the nozzle.
Although methods such as providing a screw back mechanism in the cylinder have been proposed, the above-mentioned troubles have not been fully resolved.

In such a situation, the inventor of the present invention has developed an injection molding method that prevents the so-called "stringing" in which molten resin is suspended in a thin thread between the sprue attached to the molded product and the cylinder nozzle of the injection molding machine. As a result of intensive study in order to provide a molding die, the present invention was completed.

Therefore, the gist of the present invention is to provide a stringing-preventing injection mold, which is characterized by being equipped with a sprue bush made of a metal material with high thermal conductivity. exists in

Hereinafter, the present invention will be described in detail based on the drawings, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

FIG. 1 is a longitudinal cross-sectional side view of the main parts of an example of a stringing prevention injection molding mold according to the present invention.

In the figure, 1 is the injection molding machine cylinder, 2 is the nozzle, 3 is the gate, 4 is the locating ring, 5 is the fixed side mounting plate, 6 is the cavity bush, 7 is the sprue bush, 8 is the sprue, and 9 is the Each cooling water hole is shown.

In the anti-stringing injection mold according to the present invention, the sprue bush is made of a metal material with high thermal conductivity. This sprue bushing functions to dissipate heat from the sprue section and lower the temperature of the sprue.

The metal material constituting the sprue bushing is preferably selected from copper-silver, aluminum, beryllium steel, sirumin, brass, naval brass, beryllium brass, and the like.

The sprue bush prepared from the above-mentioned metal material with high thermal conductivity is fitted into the cavity bush or core bush according to a conventional method, fixed with a fixed side mounting plate, locating ring, etc., and molded into a mold. Finish it.

The anti-stringing injection mold according to the present invention has particularly remarkable effects as described below, and its practical value is extremely high.

(1) In the stringing prevention injection molding mold according to the present invention, the sprue bush is made of a metal material with high thermal conductivity, so this sprue bush acts as a heat dissipator and accelerates the cooling and solidification of the sprue. ,
When the mold is opened, the molten resin threads that form between the sprue of the molded product and the nozzle are cooled in the sprue bushing, making them difficult to stretch, and the threads are cut by the time the mold opening is completed. , no stringiness occurs.

(2) When molding a target object using the anti-stringing injection mold of the present invention, as in the conventional method,
There is no need to set the cylinder temperature, nozzle temperature, etc. low, and the problem of poor appearance of the object does not occur. Further, there is no need to use an injection molding machine equipped with complicated mechanisms such as a check valve and a cylinder screw back.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional side view of the main parts of an example of a stringing prevention injection molding mold according to the present invention. In the figure, 1 is an injection molding machine cylinder, 2 is a nozzle, 3 is a gate, 4 is a locating ring, 5 is a fixed side mounting plate, 6 is a cavity bush, 7 is a sprue bush, 8 is a sprue, and 9 is a Each cooling water hole is shown.

Claims (1)

[Scope of utility model registration request] A stringing prevention injection mold, characterized in that the mold is equipped with a sprue bush made of a metal material with high thermal conductivity.