JPH10296733A - Molding method for improving sinkmark and mold temperature controlling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sinkmarks by a method wherein a mold temperature is raised and the cooling of a surface, the finer external appearance of which is wanted to obtain, is started from the completion of the filling of a molten resin and the cooling a surface opposite to the above-mentioned surface is started when the temperature becomes lower than the glass transition temperature or the thermal deformation temperature of a using resin. SOLUTION: By cooling a molten resin injected from an injection cylinder in a cavity formed between a fixed mold 1 side and a movable mold 2 side with cooling water pipes respectively arranged on the fixed mold 1 side and on the movable mold 2 side, a desired molded article is obtained. A temperature sensor 3 is arranged in the mold so as to lower the temperature of the reproductive portion of the cavity shape on the fixed mold 1 side, which is the cavity surface raised higher than the glass transition temperature or thermal deformation temperature in order to obtain a finer external appearance, in order to sense the lowering of the temperature of the mold below the glass transition temperature or the thermal deformation temperature of a resin used. Just after the lowering, cooling water is quickly circulated on the movable mold side so as to solidify the molten resin in order to faithfully reproduce the cavity shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article obtained by injection molding or gas-assist molding of a thermoplastic synthetic resin. And a mold temperature control system suitable for carrying out the molding method.

[0002]

2. Description of the Related Art Various molded products made of engineering plastics, also called thermoplastic synthetic resin, especially high-performance resin, are widely used for various products. Furthermore, these products are appearance parts and have a design in which reinforcing ribs are installed in order to maintain their functions, and are required to have both strength and appearance.

In order to obtain a sample having a good appearance, it is effective to increase the temperature of the mold. However, in particular, when ribs are formed on the back side, sink marks on the surface of the molded product (which occur with cooling after molding). (Dent) is a problem.

If the pressure at the time of molding is increased more than necessary in order to eliminate such defects, problems such as burrs and a decrease in shape accuracy occur. Also, when the mold temperature is lowered,
Contrary to the intended purpose of improving the appearance,
Incompatible.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, and uses an engineering plastic to improve the sink mark, which provides a molded article having a good appearance and no sink marks. It is an object of the present invention to provide a mold temperature control system suitable for carrying out this molding method.

[0006]

The object of the present invention is to provide
In order to obtain a molded product with high appearance without sink marks by using thermoplastic resin, the mold temperature is raised above the glass transition temperature or thermal deformation temperature of the resin used. The problem is solved by a molding method which starts from the time of completion and improves the sink to start cooling on the opposite side when the temperature falls below the glass transition temperature or the heat distortion temperature of the resin used.

Another object of the present invention is to provide a molding method in which the temperature of a mold at the time of molding is raised to a temperature equal to or higher than the glass transition temperature or thermal deformation temperature of the resin used in order to obtain a high-appearance molded product made of a thermoplastic resin. The problem is solved by a mold temperature control system, wherein a mold temperature at the time of cooling can be controlled independently for each of a fixed mold side and a movable mold side.

Whether the temperature has dropped below the glass transition temperature or the heat distortion temperature of the resin used is sensed by a temperature sensor embedded in the mold, and the supply of cold water to the opposite surface is started. In addition, it is possible to measure the decrease in the temperature in advance and accurately estimate the decrease in time, and therefore, it is possible to perform timer control.

[0009]

According to the molding method for improving sink marks using the mold temperature control system according to the present invention, the molten resin injected into the mold heated above the glass transition temperature or heat deformation temperature of the resin used. When the filling is completed, cooling is started from the surface layer on one side. That is, when the cooling of the side for which a high appearance is desired is started first, the molten resin in that portion starts to be solidified.

Further, the resin filled in the cavity is rapidly cooled to a temperature lower than a glass transition temperature or a heat deformation temperature, thereby faithfully reproducing the shape of the cavity. At this time, the resin in contact with the surface on the opposite side where the surface high appearance is desired and the surface on the opposite side are easily deformable because the temperature is higher than the glass transition temperature or the heat deformation temperature. It occurs so as to be pulled toward the surface where cooling and solidification has started, contributing to the reproduction of the shape of that surface.

Thereafter, in order to lower the surface temperature of the surface whose cooling has been delayed, cooling of the surface is started. This start time is provided by a temperature sensor installed in the cavity or a timer adjusted by a pre-determined time.

As a result, on one side of the molded product, there is obtained a molded product having a high appearance and being free from a change in wall thickness such as a rib or boss on the opposite side and having no sink mark.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be disclosed below with reference to the accompanying drawings showing embodiments. FIG. 1 is a model diagram of a mold temperature control system when the anti-sink molding method according to the present invention is carried out. Injection from an injection cylinder into a cavity formed between a fixed mold side and a movable mold side. The molten resin thus obtained is cooled by cooling water pipes provided on each of the fixed mold side and the movable mold side to obtain a desired molded product.

In the mold, a temperature sensor is installed, and in order to obtain a high appearance, a cavity surface having a glass transition temperature or a heat deformation temperature or higher, that is, a portion where the cavity shape on the fixed mold side is reproduced, is used. When the filling of the cavity is completed, lower the temperature of the corresponding part,
Further, it senses that the temperature of the corresponding portion has dropped below the glass transition temperature or the heat distortion temperature. Then, the cooling water on the movable mold side is immediately circulated immediately to solidify the molten resin and faithfully reproduce the cavity shape.

FIG. 2 is a time chart showing a change in mold temperature according to the molding method for improving sink marks according to the present invention. In this embodiment, it is assumed that the cavity surface on the fixed mold side has a high appearance. After the start of resin injection and the end of resin injection marked on the horizontal axis, which is the time axis, cooling of the mold, for example, the fixed mold side, which is initially located on the surface for which a high appearance is desired, is started, and the temperature accompanying this cooling When the change reaches a predetermined value, cooling on the opposite side, in this example, the movable mold side is started. Such cooling is performed by rapid circulation of cooling water while monitoring the cavity surface temperature.

FIG. 3 is a plan view, a front view, and an AA sectional view showing an example of a molded product formed by the molding method for improving sink marks according to the present invention. This part is 150 mm
It is a box-shaped body with a size of × 80 mm, a height of 12 mm, and a thickness of 2.5 mm, and a 1.6-mm rib is formed at the center. Molded products molded at a mold temperature higher than the glass transition temperature or thermal deformation temperature to improve the appearance will have sink marks on the opposite surface of the ribs even after cooling, and this will be measured with a surface roughness meter Then 0.
Although a dent of 15 mm was confirmed, according to the molding method of the present invention, the dent was 0.02 mm, and a good molded product that could not be visually confirmed was obtained.

[0017]

According to the molding method for improving sink marks according to the present invention, there is provided a method for molding a thermoplastic synthetic resin in which a mold temperature is raised to a glass transition temperature or a heat deformation temperature or higher, a molten resin is injected and then cooled. By making the cooling start timing different by a temperature sensor or a timer provided in the mold, it is possible to obtain a molded product having no sink mark and having a good appearance.

[0016]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a mold temperature control system for carrying out a molding method for improving sink marks according to the present invention.

FIG. 2 is a time chart in temperature control for a molding method for improving sink marks according to the present invention.

FIG. 3 is a diagram showing an example of a molded product with ribs obtained by a molding method for improving sink marks according to the present description.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed mold 2 Movable mold 3 Temperature sensor 4 Heating / cooling water inlet 5 Heating / cooling water outlet 6 Switching device for hot / cold water 7 Temperature controller

Claims (6)

[Claims] 1. A molding method in which a mold temperature during molding is raised to a temperature higher than a glass transition temperature or a heat deformation temperature of a used resin in order to produce a molded article having a high appearance without using sink, using a thermoplastic high-performance resin. The mold temperature control system that allows the mold temperature during cooling to be independently controllable on each of the fixed mold side and the movable mold side is used. Starting cooling of the mold on the surface to obtain the appearance, and further cooling the opposite mold surface when the temperature falls below the glass transition temperature or heat deformation temperature of the resin used. , A molding method for improving sink marks. 2. A temperature sensor mounted in the mold detects that the temperature of the mold on the surface for which a high appearance is desired is lowered to a predetermined temperature, and cools the opposite surface by a temperature controller interlocked with the temperature sensor. A molding method for improving sink marks, wherein 3. A method in which the mold temperature of the surface for which a high appearance is desired to be reduced to a predetermined temperature is estimated for a predetermined time, and cooling of the movable side is started by a temperature controller linked with a timer. A molding method for improving sink marks, characterized in that: 4. The molding method according to claim 1, wherein the mold temperature is individually controlled while injecting a high-pressure gas into the molten resin in a molded article having a hollow portion. 5. In order to produce a molded article having a high appearance without sink marks by using a thermoplastic high-performance resin, the molding temperature at the time of molding is raised to a temperature higher than a glass transition temperature or a heat deformation temperature of the resin used. A mold temperature control system for a method, wherein a mold temperature during cooling of a molten resin can be controlled independently for each of a fixed mold side and a movable mold side. . 6. The mold temperature control system according to claim 5, wherein the temperature of each of the fixed mold and the movable mold is adjusted by switching between cold water and hot water.