JPH0628901B2 - Method of heating mold cavity for plastic molding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for raising the temperature of a mold cavity during molding of a plastic, and more particularly, to raising the temperature of the mold cavity before molding to obtain an optimum high temperature condition for molding. The present invention relates to a novel improvement that enables the temperature to be lowered after the molding as well as the molding.

[Conventional technology]

Conventionally, there are various methods for raising the temperature of the mold cavity for plastic molding of this kind, but a typical method among them is not mentioned here, although the literature name disclosing the method is not mentioned. In general, the temperature inside the mold cavity is controlled by causing a heat medium to flow through the guide hole formed in the mold.

[Problems to be Solved by the Invention]

The conventional mold cavity temperature raising method for plastic molding is
Since it was configured as described above, there were the following problems.

That is, in general, the temperature of the mold cavity during molding is
The higher it is, the better the molding is and the better the transferability is. However, in the case of the conventional method of heating the mold cavity by guiding the heat medium into the mold, the mold cavity is heated to a high temperature. However, it is necessary to lower the mold temperature after molding to take out the molded product, and it is extremely difficult to control the temperature rise and temperature drop in a short time via the heat medium. It was difficult, and it was impossible to quickly raise both the temperature rise and the temperature fall.

Therefore, in the conventional molding method, it has been a reality that the quality (particularly the surface condition) of the molded product or the productivity must be sacrificed.

The present invention has been made to solve the above problems, and in particular, the temperature of the mold cavity is raised before molding, and the mold is molded at a high temperature suitable for molding, and the temperature is lowered after molding. It is an object of the present invention to provide a method for raising the temperature of a mold cavity that can be performed.

[Means for Solving the Problems]

A method of raising the temperature of a mold cavity for plastic molding according to the present invention is a method of raising the temperature of a pair of molds to a predetermined temperature, wherein the mold cavity is heated under an open state,
A heating element is positioned in the die cavity of the die to raise the temperature of the die cavity above the predetermined temperature, and after the heating element is separated from the die cavity, the die is closed. It is the method.

[Work]

In the method for raising the temperature of the mold cavity for plastic molding according to the present invention, the temperature of the mold is constantly adjusted to a predetermined temperature suitable for taking out a molded product, and the heating element is set at the stage when the mold is in an open state. The mold is moved into the cavity, the temperature of the mold cavity is raised in this state, and the heating element is moved to the outside of the mold after the temperature is raised to the predetermined temperature or higher.

Since the mold is closed in this heated state, the mold cavity is kept at a raised temperature higher than the predetermined temperature, and in this state the raw material is supplied into the mold cavity and molded at high temperature. Is done.

After this molding is completed, the temperature of the mold cavity drops to the predetermined temperature during mold temperature control, that is, the temperature at which the molded product is taken out.
The molded product is cooled and can be taken out.

〔Example〕

Hereinafter, a method for raising the temperature of a mold cavity for plastic hollow molding will be described in detail as a preferred embodiment of a method for raising the temperature of a mold cavity for plastic molding according to the present invention with reference to the drawings. 1 to 4 are for showing a method for raising the temperature of the mold cavity for plastic molding according to the present invention, and FIGS. 1 to 3 are the molding machines showing the state of raising the temperature of the mold. And FIG. 4 is a flow chart.

In the figure, reference numeral 1 is an accumulator head connected to an extruder 2, and a pair of molds 3, which are in an open state and a closed state, are provided below the injection port 1a of the accumulator head 1. 4 are provided.

Each of the molds 3 and 4 has a mold cavity 5 formed of a recess.
Is formed, and when the molds 3 and 4 are in the closed state, the mold cavity 5 having a predetermined shape is formed.

At a position near each of the molds 3 and 4, a heating element 7 provided on a carriage 6 and made of a heat source such as a far-infrared heater, a gas heater, and a laser is provided along a vertical direction A and a horizontal direction B by a conveying means (not shown). It is movably arranged.

The molding machine for showing the method of raising the temperature of the mold cavity for plastic molding according to the present invention is configured as described above, and its operation will be described below.

First, as shown in the flow chart of FIG. 4, starting in the first step 10, the heating element 7 moves along the lateral direction B to a position below the molds 3 and 4, and the second step 11 advances. It becomes the limit.

In the above-mentioned state, the temperature of each of the molds 3 and 4 is adjusted via the heat medium to a predetermined temperature which is a molded product taking-out temperature suitable for taking out the molded product.

At the same time, the rising start delay timer is activated in the third step 12, the heating element 7 is turned on in the fourth step 13, and
In the fifth step 14, the temperature raising time timer is started, and in the sixth step 15, the heating element 7 starts to rise.

Next, the heating element 7 rises along the ascending / descending direction A, and at the ascent end of the seventh step 16, the mold cavity 5 in the open state is closed.
The temperature inside the mold cavity 5 is raised by the temperature raising time timer of the fifth step 14 until it reaches a high temperature state sufficiently higher than the predetermined temperature during the temperature control.

When the heating of the heating element 7 is completed, the eighth step 1
The heating element 7 is turned off by 7 and the heating element 7 starts to descend by the ninth step 18, and reaches the lowering limit by the 10th step 19.

At the aforementioned lower limit, the heating element 7 is located immediately below the molds 3, 4, and the backward start delay timer of the 11th step 20 is actuated to start the backward start of the 12th step 21 and the backward limit of the 13th step 22. The heating element 7 is the original first step 10
It returns to the standby position at that time, and the 14th step 23 is stopped.

It should be noted that, at the retreat limit of the thirteenth step 22 described above, the molding machine is automatically operated, and the raw material extruded by the extruder 2 is in the closed state shown in FIGS. 2 to 3 through the injection port 1a of the accumulator head 1. The parison 30 is injected into the mold cavity 5.

The parison 30 is molded under extremely favorable conditions in the mold cavity 5 in a high temperature state, and molding with a good surface state is performed. At the end of molding, the temperature of the mold cavity 5 is set to the molds 3 and 4. Since the temperature has fallen to the predetermined temperature, which is the temperature at which the molded product is taken out, the molds cooled after molding can be taken out in a good condition by opening the molds 3 and 4. .

Therefore, the mold cavity 5 has to be heated to a temperature higher than the predetermined temperature only for a short time until the transfer is completed at the time of molding, and the heating element 7 shown in the above operation is turned on. Experiments have shown that time is sufficient.

Also, the heater capacity of the heating element 7 (shape, quantity, etc.)
It has also been confirmed that a molded product excellent in transferability can be obtained without increasing the control cycle by making the distance between the mold cavity 5 and the mold cavity 5 appropriate and controlling the heat generation time and the timing of injection.

In this embodiment, the case of molding a plastic hollow molding parison has been described, but it goes without saying that the invention can be applied to various moldings such as an injection molding method as well as a parison.

〔The invention's effect〕

Since the method for raising the temperature of the mold cavity for plastic molding according to the present invention is configured as described above, the following effects can be obtained.

That is, after maintaining the mold itself at a constant temperature at the molded product ejection temperature, which is the specified temperature, the mold cavity is directly heated by the heating element when the mold is opened, so that the temperature is above the specified temperature. Sometimes the mold cavity has a high temperature that is optimal for molding, and when the molded product is taken out, the mold temperature drops to a specified temperature, so two contradictory temperature conditions can be easily achieved with the same mold, and the transfer is always performed. Molding with excellent properties can be achieved, and the yield can be greatly improved.

[Brief description of drawings]

1 to 4 are for showing a method for raising the temperature of the mold cavity for plastic molding according to the present invention, and FIGS. 1 to 3 are the molding machines showing the state of raising the temperature of the mold. And FIG. 4 is a flow chart. 3 and 4 are molds, 5 is a mold cavity, and 7 is a heating element.

Claims (1)

[Claims] 1. A method of raising the temperature of a pair of molds (3, 4) to a predetermined temperature in a mold cavity temperature raising method for plastics molding, wherein the molds (3, 4) are opened. The heating element (7) is positioned in the mold cavity (5) of the mold (3, 4) to raise the temperature of the mold cavity (5) above the predetermined temperature, and the heating element (7) is A method for raising the temperature of a mold cavity for plastic molding, characterized in that the mold (3, 4) is closed after being separated from the mold cavity (5).