JPH1177780A - Plastic molding method and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a molded product of high accuracy even with respect to a molded product having an uneven wall thickness shape large in wall thickness distribution such that wall thickness changes suddenly. SOLUTION: Temp. control plates 13, 14 regulating the whole temp. of a mold are provided on the outsides of a fixed mold 11 and a movable mold 12 and die plates 17, 18 are provided on the outsides of them through insulating plates 15, 16. A pair of molds 11, 12 are clamped under predetermined pressure at the time of molding by a mold clamping mechanism 19. Split mold temp. regulating means 20a, 20b (20) capable of locally controlling temp. rapidly and finely and pressure detection means 21a, 21b are provided in the vicinity A of the boundary surface of the wall thickness sudden change part of a forming part of a cavity 27 and in the vicinity B of a molten resin injection gate part and operation control parts 22a, 22b operating set temps. corresponding to the detection results of the pressure detection means to control the split mold temp. regulating means 20 are provided and, by this constitution, the temp. in the vicinity of the boundary surface of the wall thickness sudden change part and that in the vicinity of the molten resin injection gate part are controlled to desired temps. rapidly and finely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic molding method and a molding apparatus, and more particularly, to a molded article having a thin portion and a thick portion, and having a large wall thickness distribution such that the wall thickness changes rapidly. The present invention also relates to a plastic molding method and a plastic molding apparatus capable of obtaining a molded product having high unevenness (especially, small optical distortion affecting optical characteristics) even with a molded product having an uneven thickness.

[0002]

2. Description of the Related Art In a plastic molding method and apparatus in which a molten resin is injected and filled into a mold for forming a cavity and then solidified by cooling to obtain a molded product, the influence of the shape of the molded product on shrinkage is extremely small. large. In particular, if there is an extreme imbalance in the thickness of the molded product, there will be variations in the cooling rate, and therefore, the shrinkage of each part of the molded product will differ,
Deterioration of shape accuracy and generation of optical distortion are likely to occur.

Conventionally, in this type of molded product, the temperature of the mold is raised to a temperature higher than the glass transition point of the resin to increase the fluidity of the resin, and then the resin is injected. After the injection, the mold is cooled. The molded product is taken out. In this case, as a molding die,
For example, as described in Japanese Patent Publication No. 7-51305, the heat medium passage in the mold is arranged at a short distance from the mold surface when the surface area of the mold is large, and There has been proposed a method in which the surface temperature of a molded article is made uniform by, for example, disposing the molded article from the upstream side to the downstream side so as to decrease the distance from the mold surface.

[0004]

Thus, in the above-described molding die, the temperature distribution on the cavity surface depends on the distance from the cavity surface to the heating element or the cooling element. However, since the setting of the distance varies depending on the shape of the molded product, it is extremely difficult to set the optimal arrangement of the heat medium passages.

[0005] Further, oil or water is used as a heat medium,
It takes time for heat exchange, cannot perform rapid heating,
Strict temperature setting is difficult, especially for molded parts with a large thickness ratio between thin and thick parts and a sudden change in thickness. There was a problem that it was difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a thin part and a thick part in one molded product, and a large deviation of the thickness distribution such that the thickness changes rapidly. It is an object of the present invention to provide a plastic molding method and a plastic molding apparatus capable of obtaining a molded product having high wall thickness (particularly, having a small optical distortion that affects optical characteristics).

[0007]

According to the first aspect of the present invention, a molten resin is injected and filled into a mold which forms a cavity comprising at least one thin portion and a thick portion, and then cooled by cooling. In a plastic molding method for obtaining a molded product by solidification, a divided mold temperature control means is provided near a boundary surface of a sudden change in thickness and in a vicinity of a molten resin injection gate portion. It is characterized by locally and quickly and finely controlling the temperature of the surface and the vicinity of the molten resin injection gate, thereby uniformizing the pressure in a portion where the pressure is likely to be unevenly distributed in a short time, preventing molding distortion, It is intended to obtain an accurate molded product.

According to a second aspect of the present invention, in the first aspect of the present invention, the local temperature control in the vicinity of the boundary of the suddenly changing thickness and the vicinity of the molten resin injection gate is performed by controlling the temperature of the resin glass under the pressure during the molding process. It is characterized in that it is carried out in a temperature range not lower than the transition point, thereby promoting the relaxation of the strain due to the molecular orientation strain and the difference in volume shrinkage, preventing the molding strain, and obtaining a molded product having high precision transferability. It is made possible.

In a third aspect of the present invention, in the first or second aspect of the present invention, a split type temperature control means and a pressure detection means are provided in the vicinity of the boundary surface of the sudden thickness change portion and in the vicinity of the molten resin injection gate. Based on the detection result of the pressure detecting means, the local temperature control is performed by the split-type temperature adjusting means, so that the temperature at a desired position can be more appropriately adjusted to an optimum value. Things.

According to a fourth aspect of the present invention, a molten resin is injected and filled into a mold for forming a cavity comprising at least one thin portion and a thick portion, and then solidified by cooling to obtain a molded product. In the plastic molding apparatus to be obtained, divided temperature control means and pressure detection means provided near the boundary between the thin-walled part and the thick-walled part where the wall thickness suddenly changes and near the molten resin injection gate part, and detection by the pressure detection means Having operation control means for controlling the adjustment operation of the split-type temperature adjustment means based on the result,
The pressure in a portion where the pressure is apt to be unevenly distributed is made uniform in a short time to prevent molding distortion and to obtain a highly accurate molded product.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the pressure detecting means is a piezoelectric pressure sensor with a built-in temperature sensor, so that it is not necessary to separately provide a thermocouple for temperature measurement. In addition, appropriate temperature adjustment linked to pressure behavior can be performed.

According to a sixth aspect of the present invention, in the invention of the fourth aspect, the cavity forming portion and the gate portion of the mold are constituted by a plurality of mold members, and the vicinity of the boundary surface of the suddenly changing portion and the molten resin The injection gate portion is characterized by being made of a material having higher thermal conductivity than other portions,
By forming the cavity forming portion and the gate portion of the mold from a plurality of mold members, and by configuring the vicinity of the boundary between the suddenly changing thickness and the vicinity of the molten resin injection gate portion with a material having higher thermal conductivity than other portions, This allows the desired temperature to be quickly adjusted.

According to a seventh aspect of the present invention, in the fourth aspect of the present invention, the split type temperature control means provided near the boundary surface of the suddenly changing thickness portion and near the molten resin injection gate portion is provided on the surface of the ceramic material with a thin film electric resistance. A thin-film electric resistor is formed on the surface of the ceramic material by providing a split-type temperature control means provided near the boundary of the sudden change in the thickness and near the molten resin injection gate. By using a planar heater, the temperature at a desired position can be quickly and satisfactorily adjusted to a higher temperature range.

According to an eighth aspect of the present invention, in accordance with the seventh aspect of the present invention, the planar heater is constituted by a divided control planar heating element having a plurality of lattice shapes. The split control type planar heating element having the lattice shape described above allows the temperature at a desired position to be more finely adjusted quickly and satisfactorily.

According to a ninth aspect of the present invention, in accordance with the fourth aspect of the present invention, the split-type temperature control means provided near the boundary surface of the rapidly changing thickness portion and near the molten resin injection gate is an electromagnetic induction heating means. Characteristically, the temperature of the desired position can be quickly increased with a relatively simple structure by using the electromagnetic induction heating means as the split-type temperature control means provided near the boundary surface of the rapidly changing thickness and near the molten resin injection gate. And it was made to be able to adjust well.

According to a tenth aspect of the present invention, in the invention of the fourth aspect, the divided type temperature control means provided near the boundary surface of the sudden thickness change portion and near the molten resin injection gate is a flexible heater. Therefore, by using a flexible heater as the divided type temperature control means provided near the boundary surface of the rapidly changing thickness portion and near the molten resin injection gate portion, the temperature at the desired position can be quickly and satisfactorily regardless of whether the surface is flat or curved. Adjustable.

According to an eleventh aspect of the present invention, in the invention of the fourth aspect, the split-type temperature adjusting means provided near the boundary surface of the suddenly changing thickness and near the molten resin injection gate is a split control type ring heater. Therefore, by using a split control type ring heater as the split type temperature adjusting means provided near the boundary surface of the rapidly changing thickness portion and near the molten resin injection gate portion, the temperature at a desired position can be quickly and more finely adjusted. It can be adjusted well.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to achieve the above-mentioned object, the applicant of the present invention has a thin molded part having a thin part and a thick part, and a large deviation of the thickness distribution such that the thickness changes suddenly. A molding experiment was performed on a molded product having a wall shape, and an occurrence state of optical distortion was examined. The resin used in the experiment was polycarbonate (Teijin Kasei Panlite L1225L), and the confirmed shapes were as follows. Symmetrical type: concave type, convex type (thin part 5 mm, thick part 20 m
m, width 10 mm) Asymmetric: step shape (wall thickness 5 mm, 10 mm, 20)
mm, width 10 mm) Molding conditions were as follows: mold temperature at the time of injection was 170 [° C], after holding for 3 minutes, slowly cooling at a cooling rate of about 1 [° C / min] per minute, and at 130 [° C]. The molded product was taken out.

FIGS. 6 (A) to 6 (C) show the aforementioned symmetrical shape (FIG. 6 (A): concave type, FIG. 6 (B): convex type) and asymmetric type (FIG. 6 (C): hierarchical shape). 2) shows the state of optical distortion in each shape observed by the polarizing plate. In the experiment, the mold temperature at the time of injection was set to a high temperature, and after being kept at the same temperature for a certain period of time, the cooling was performed slowly. A large amount of optical distortion remains in B. This result indicates that it is necessary to control the temperature more precisely and more precisely in the vicinity A of the boundary portion including the vicinity B of the gate portion than in the other portions.

The present invention is based on the above-mentioned phenomenon, and is directed to a method of molding a molded article having a thin-walled portion and a thick-walled portion, and having an uneven thickness with a large thickness distribution. The present invention is characterized in that the temperature in the vicinity of the boundary of the suddenly changing thickness and in the vicinity of the molten resin injection gate is locally and quickly and finely controlled.

FIG. 1 is a block diagram for explaining one embodiment of a plastic molding method and apparatus according to one embodiment of the present invention. In FIG. 1, a cavity comprising a thin portion and a thick portion is formed. The pair of molds includes a fixed mold 11 and a movable mold 1.
And 2. As shown in FIG. 1, outside the fixed mold 11 and the movable mold 12 in the mold clamping direction, a temperature control plate 13 which has both heating and cooling functions therein and regulates the temperature of the whole mold is provided. , 14 are provided. The outside of the temperature control plates 13 and 14 is a heat insulating plate 15,
16 are supported by right and left die plates 17 and 18, respectively. At the time of molding, the mold clamping mechanism 19 clamps the pair of molds at a predetermined pressure from the mold clamping direction.

The divided temperature control means 20 (heaters 20a ₁ and 20a ₁₎ capable of controlling the temperature locally and quickly and finely are located near the boundary A of the sudden change in the thickness of the cavity forming part and near the molten resin injection gate B. 20a ₂ , 20a ₃ , 20a ₄ and a heater controller 20b) are provided. The split mold temperature control means 20 includes pressure detection means 21 (internal pressure sensor 21a, internal pressure detection section 21) similarly provided in the vicinity A of the boundary surface of the sudden change in thickness and the vicinity B of the molten resin injection gate.
A calculation control unit 22 (calculation unit 22a, output control unit 22b) that calculates and controls the set temperature according to the detection value result of b).
It has.

FIG. 2 is an enlarged view of part II of FIG. 1. In FIG. 2, a thin-film electric resistor is formed on the surface of a ceramic material having good heat conductivity as a division type temperature control means 20. an example of using a planar heater 20a _1. Figure 3 shows a perspective view of the plane heater 20a _1. Thick sudden change in the vicinity and the molten resin injection gate is buried in the vicinity of these planar heater 20a ₁ consists division control type planar heating element H in which the plurality of grating pattern, desired positions by energizing the timely external Can be quickly and satisfactorily adjusted to a finer temperature range.

[0024] FIG. 4 (A), split as the temperature adjusting means 20, a main part configuration diagram for explaining an example of using the electromagnetic induction heating member 20a _2, FIG. 4 (B) FIG. 4 (A ) IV
In B-part enlarged view, this example, the heating member 20a ₂ to the electromagnetic induction heating coil is wound in the thick-changing part near A and the molten resin injection gate near B are plurality buried, the electromagnetic induction heating unit the 20a ₂ is heated by an external high-frequency generator (not shown), quickly and finely is obtained so as to adjust the temperature.

FIG. 5A is a main part configuration diagram for explaining an example in which a flexible heater 20a ₃ (silicon rubber heater) is used as the split type temperature control means 20.
(B) is a VB enlarged view of FIG. 5 (A), by using a flexible heater 20a _3, are possible directly onto the thick-changing part regardless of planar-curved cavity having a complicated shape This is suitable for adjusting the temperature at a desired position of the.

[0026] FIG. 6 (A) is a split-type temperature regulating means 20, a main part configuration diagram for explaining an example of using a split-controlled ring heater 20a _4, FIG. 6 (B) 6
FIG. 6A is an enlarged view of a portion VI, and FIG.
a perspective view of a _4, the heater 20a ₄ consists multidivided heating resistor heater which can freely control the heating value,
In addition, the small size allows quick and fine temperature control.

The temperature control in the vicinity of the rapidly changing thickness portion and the vicinity of the molten resin injection gate portion is performed immediately after injection and filling until the difference in resin internal pressure due to the difference in thickness is eliminated. The presence or absence of this resin internal pressure difference is determined by the pressure detecting means 2.
1 (the internal pressure sensor 21a, the internal pressure detecting unit 21b), and calculates and controls the set temperature based on the result.
Perform appropriately with the signal from b). Since the pressure detecting means 21 is a piezoelectric pressure sensor 21a with a built-in temperature sensor, it is not necessary to provide a separate thermocouple for temperature measurement in another part, and it is necessary to perform appropriate temperature adjustment linked to the pressure behavior. Can be.

The temperature condition is set in a temperature range not lower than the glass transition point of the resin under the pressure during the molding process, so that the molecular orientation distortion generated during the injection filling process into the cavity and the internal pressure of the resin during the cooling process can be ensured. In addition, it is possible to eliminate both strains caused by a difference in volume shrinkage due to non-uniform cooling rate and the like.

In the present invention, the cavity forming portion and the gate forming portion of the mold comprising the thin portion and the thick portion are formed of a plurality of mold members, and the vicinity of the rapidly changing thickness portion and the vicinity of the molten resin injection gate portion. Is made of a material having a higher thermal conductivity (for example, an aluminum alloy, a copper alloy, or a composite of a metal and a ceramic having a higher thermal conductivity) than the other portions. It is a structure which can efficiently adjust the temperature to a desired temperature.

As described above, the use of the plastic molding method and the plastic molding apparatus according to the present invention makes it possible, in particular, to form a single molded product having a thin portion and a thick portion and having a sudden change in thickness. Even with respect to a molded product having an uneven thickness with a large thickness distribution, it is possible to obtain a molded product with high accuracy (particularly, small optical distortion that affects optical characteristics).

[0031]

According to the first aspect of the present invention, a molten resin is injected and filled into a mold for forming a cavity comprising at least one thin portion and a thick portion, and then is solidified by cooling to form a mold. In the plastic molding method for obtaining a product, the temperature of the portion is rapidly and finely controlled locally by the split-type temperature control means provided near the boundary surface of the rapidly changing thickness portion and near the molten resin injection gate portion. Since the temperature in the vicinity of the boundary of the sudden change in the thickness and the vicinity of the molten resin injection gate is locally and quickly and finely controlled, the pressure in the portion where the pressure tends to be unevenly distributed can be made uniform in a short time, As a result, molding distortion can be prevented and a highly accurate molded product can be obtained.

According to a second aspect of the present invention, in the first aspect of the present invention, the local temperature control in the vicinity of the boundary of the sudden change in the thickness and in the vicinity of the molten resin injection gate is performed by controlling the resin glass under pressure during the molding process. The temperature is controlled in the temperature range above the transition point, so local temperature control near the boundary of the sudden change in the thickness and near the molten resin injection gate is controlled by the temperature above the glass transition temperature of the resin under the pressure during the molding process. Since it is performed in the region, the relaxation of the strain due to the molecular orientation strain and the difference in the volume shrinkage can be further promoted, and as a result, a molded product having high precision transferability can be obtained by preventing molding distortion.

According to a third aspect of the present invention, in the first or second aspect of the present invention, a split type temperature control means and a pressure detection means are provided in the vicinity of the boundary surface of the rapidly changing thickness portion and in the vicinity of the molten resin injection gate. Based on the detection result of the detecting means, local temperature control is performed by the split-type temperature controlling means. Means,
Since the local temperature control is performed by the divided temperature control means based on the detection result of the pressure detection means, the temperature at a desired position can be more appropriately adjusted to the optimum value.

According to a fourth aspect of the present invention, a molten resin is injected and filled into a mold for forming a cavity comprising at least one thin portion and a thick portion, and then solidified by cooling to obtain a molded product. In the plastic molding apparatus to be obtained, a split-type temperature adjusting means and a pressure detecting means are provided in the vicinity of a boundary surface of a sudden change in thickness and in a vicinity of a molten resin injection gate, and the split-type temperature adjusting means is provided based on a detection result of the pressure detecting means. The plastic molding apparatus is provided with a split-type temperature adjusting means and a pressure detecting means in the vicinity of the boundary surface of the suddenly changing wall thickness and in the vicinity of the molten resin injection gate, and the pressure detecting means is provided. Operation control means for controlling the adjusting operation of the split-type temperature adjusting means based on the detection result of the means. Can be made uniform between, as a result, prevent forming distortion, it is possible to obtain a high-precision molded products.

According to a fifth aspect of the present invention, in the fourth aspect, since the pressure detecting means is a piezoelectric pressure sensor with a built-in temperature sensor, the pressure detecting means is a piezoelectric pressure sensor with a built-in temperature sensor. In addition, there is no need to provide a separate thermocouple for temperature measurement, and appropriate temperature control linked to pressure behavior can be performed.

According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the cavity forming portion and the gate portion of the mold are constituted by a plurality of mold members, and the vicinity of the boundary between the suddenly changing portion of the thickness and the injection of the molten resin. Since the vicinity of the gate portion is made of a material having higher thermal conductivity than the other portions, the cavity forming portion and the gate portion of the mold are formed of a plurality of mold members, and
Since the vicinity of the boundary surface of the portion where the thickness changes suddenly and the vicinity of the molten resin injection gate portion are made of a material having higher thermal conductivity than other portions, the temperature can be quickly adjusted to a desired temperature.

According to a seventh aspect of the present invention, in accordance with the fourth aspect of the present invention, the split type temperature control means provided near the boundary of the sudden change in the thickness and near the molten resin injection gate is provided with a thin film electric resistance on the surface of the ceramic material. Since the heater is a planar heater, the split type temperature control means provided near the boundary of the sudden change in thickness and near the molten resin injection gate has a thin-film electric resistor formed on the surface of the ceramic material. Therefore, the temperature at a desired position can be quickly and well adjusted to a higher temperature region.

According to an eighth aspect of the present invention, in accordance with the seventh aspect of the present invention, since the planar heater comprises a divided control planar heating element having a plurality of lattice shapes, the planar heater has a plurality of lattice shapes. The temperature of the desired position can be finely and quickly adjusted satisfactorily because of the division control type sheet heating element.

According to a ninth aspect of the present invention, in accordance with the fourth aspect of the present invention, the split-type temperature adjusting means provided near the boundary surface of the suddenly changing thickness and near the molten resin injection gate is an electromagnetic induction heating means. Since the split-type temperature control means provided near the boundary of the sudden change in thickness and near the molten resin injection gate is an electromagnetic induction heating means, the temperature at the desired position can be quickly and satisfactorily adjusted with a relatively simple structure. can do.

According to a tenth aspect of the present invention, in accordance with the fourth aspect of the present invention, the divided type temperature control means provided near the boundary of the suddenly changing thickness portion and near the molten resin injection gate is a flexible heater. Since the divided type temperature control means provided near the boundary of the sudden change portion and near the molten resin injection gate is a flexible heater, it is possible to quickly and satisfactorily control the temperature at a desired position regardless of a flat surface or a curved surface. it can.

According to an eleventh aspect of the present invention, in the invention of the fourth aspect, the split-type temperature adjusting means provided near the boundary surface of the rapidly changing thickness portion and near the molten resin injection gate is a split control type ring heater. Since the split-type temperature control means provided near the boundary surface of the portion where the thickness changes suddenly and near the molten resin injection gate is a split control type ring heater, the temperature at a desired position can be finely and quickly adjusted finely. be able to.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram for explaining an embodiment of a plastic molding method and apparatus according to the present invention.

FIG. 2 is a main part configuration diagram showing an example in which a planar heater is used as a split-type temperature control unit.

FIG. 3 is a perspective view showing an example of a planar heater.

FIG. 4 is a main part configuration diagram showing an example in the case of using an electromagnetic induction heating means as a division type temperature control means.

FIG. 5 is a main part configuration diagram showing an example in which a flexible heater is used as a split-type temperature control unit.

FIG. 6 is a main part configuration diagram showing an example in the case of using a split control type ring heater as a split type temperature adjusting means.

FIG. 7 is a diagram showing a state of optical distortion in each shape observed by a polarizing plate.

[Explanation of symbols]

11, 12: a pair of molds (fixed mold, movable mold), 13, 1
4: Temperature control plate, 15, 16 ... Heat insulation plate, 17, 18 ...
Die plate, 19: mold clamping mechanism, 20: split temperature control means, 21: pressure detection means, 22: arithmetic control unit, 2
3, 24: cavity forming portion, 25, 26: gate portion,
27 ... cavity.

Claims (11)

[Claims] A molten resin is injected into a mold forming a cavity comprising at least one thin portion and a thick portion.
In a plastic molding method of filling and then solidifying by cooling to obtain a molded article, a divided mold temperature control means is provided near the boundary between the thin portion and the thick portion and near the boundary between the suddenly changing thickness and the molten resin injection gate. A plastic molding method characterized by locally and quickly and finely controlling the temperature in the vicinity of the boundary surface of the rapidly changing wall thickness and in the vicinity of the molten resin injection gate by the split-type temperature control means. 2. The method according to claim 1, wherein the local temperature control in the vicinity of the boundary surface of the sudden thickness change portion and in the vicinity of the molten resin injection gate is performed in a temperature region equal to or higher than the glass transition point of the resin under the pressure during the molding process. The plastic molding method according to claim 1, wherein 3. A split type temperature control means and a pressure detecting means near a boundary surface of the sudden thickness change portion and near a molten resin injection gate, and based on a detection result of the pressure detecting means, the split type temperature adjusting means is provided. 3. The plastic molding method according to claim 1, wherein local temperature control is performed by adjusting means. 4. A molten resin is injected into a mold forming a cavity comprising at least one thin portion and a thick portion.
In a plastic molding apparatus which fills and then solidifies by cooling to obtain a molded product, a divided mold temperature control provided near the boundary between the thin-walled portion and the thick-walled portion where the thickness suddenly changes and near the molten resin injection gate. Means and pressure detecting means,
An operation control means for controlling an adjusting operation of the split mold temperature adjusting means based on a detection result of the pressure detecting means. 5. The plastic molding apparatus according to claim 4, wherein said pressure detecting means is a piezoelectric pressure sensor with a built-in temperature sensor. 6. A cavity forming portion and a gate portion of the mold are constituted by a plurality of mold members, and a material having a higher thermal conductivity in the vicinity of a boundary surface of a rapidly changing thickness portion and in the vicinity of a molten resin injection gate portion than other portions. 5. The plastic molding apparatus according to claim 4, wherein the plastic molding apparatus comprises: 7. A split type temperature control means provided in the vicinity of the boundary surface of the suddenly changing thickness portion and in the vicinity of the molten resin injection gate is a planar heater having a thin film electric resistor formed on the surface of a ceramic material. The plastic molding apparatus according to claim 4, wherein 8. The plastic molding apparatus according to claim 7, wherein said sheet heater comprises a division control type sheet heating element having a plurality of lattice shapes. 9. The plastic molding apparatus according to claim 4, wherein the split-type temperature control means provided near the boundary surface of the rapidly changing thickness portion and near the molten resin injection gate is an electromagnetic induction heating means. 10. The temperature control means provided in the vicinity of the boundary surface of the sudden change in thickness and in the vicinity of the molten resin injection gate is a flexible heater.
A plastic molding apparatus as described. 11. The plastic molding apparatus according to claim 4, wherein the split-type temperature control means provided near the boundary surface of the sudden change in thickness and near the molten resin injection gate is a split control type ring heater. .