JPS60166433A - Method and apparatus for injection-molding synthetic resin - Google Patents

Abstract

PURPOSE:To execute the operation of inflow of a molten resin to be injected smoothly and unforcibly by previously heating a cavity die section partially and heat-insulating it immediately before the operation of injection molding. CONSTITUTION:A heating mechanism 14 is held by both dies 3a, 3b. Heaters 17 for the heating mechanism 14 are ignited, and each cavity die section 7a, 7b is heated through hole sections 16. Temperatures where the cavity die sections 7a, 7b are heated partially are detected by sensitive sensors buried near the cavity die sections 7a, 7b, and heater heating is stopped in the heating mechanism 14 at a point of time when the cavity die sections are heated sufficiently. Molds are released once, the heating mechanism 14 is retreated, and both dies 3a, 3b are closed instantaneously and normal injection-molding operation is executed. A refrigerant from pipings 19 is flowed forcibly into flowing holes 18 in masks 15 so that positions except the cavity die sections 7a, 7b are heated unnecessarily on the heating operation of the heating machanism 14. Accordingly, an injected molten resin smoothly spreads over all the corners rapidly, and the operation of injection is completed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a new synthetic resin injection molding method and apparatus, and more specifically, to a method and apparatus for locally heating the inner surface of a mold cavity. The present invention relates to a synthetic resin injection molding method and an apparatus thereof.

[Prior art]

Conventionally, synthetic resin injection molding apparatuses as shown in FIGS. 1 and 2 are generally known.

Describing the structure of the drawings, 1 is a fixed plate, 2 is a movable plate, and both plates 1 and 2 have a pair of molds 3a that can be opened and closed.
+3b is fixed. Reference numeral 4 indicates tie rods that support both plates 1.2, and a plurality of tie rods are arranged in parallel on the molding apparatus main body a, and the movable platen 2 is moved by a desired hydraulic mold clamping mechanism 5.
It is designed to be able to move back and forth along this tie rod 4. Reference numeral 6 indicates a cavity formed by a pair of molds 3a and 3b, and a cavity mold portion 7 is formed on the contact/separation surface of each mold 3''*3b so that a desired molded product can be processed.
a, 7b are formed. 8 is a gate bored in the cavity mold part 7a of the mold 3a fixed to the fixed platen 1 (Itll), through which the molten resin injected by a desired injection mechanism 9 is effectively injected into the cavity 6 through the runner part 10. Reference numeral 11 indicates a runner heating cylinder disposed in the runner part 10, which has a built-in heater to prevent the molten resin in the runner part 10 from cooling and solidifying, thereby enabling runner-less injection operation. Reference numeral 12 denotes a sharp local heating section formed at the tip of the runner heating cylinder 11, which faces the gate 8 and which intermittently heats the resin material located at the gate 8 each time an injection molding operation is performed. Moreover, it is possible to heat locally, for example, the configuration shown in Patent No. 762148 (see Japanese Patent Publication No. 48-5093) invented by the present applicant is shown.In this conventional example, a runnerless system is used. However, a so-called runner one-type injection molding apparatus that does not include a runner heating cylinder 11 is also widely known. 13 indicates holes for cooling water flow drilled in the mold 3a #3b, and the molding operation is performed. The mold is cooled at the time.

An overview of the operation will be explained in the above configuration.

Prior to the injection operation of the injection mechanism 9, the movable platen 2 moves toward the fixed platen 1' by the action of the hydraulic mold clamping mechanism 5, and both plates 1 and 2
The molds 3 at 3 b are brought into close contact and the so-called mold is closed. After the injection mechanism 9 operates, the desired molten resin passes through the runner part 10, passes through the gate 8, and is filled into the cavity 6 and cooled and solidified, the movable platen 2 is moved from the fixed platen 1 by the action of the hydraulic mold clamping mechanism 5. The molds 3a, 3b are separated, the so-called mold is opened, and the molded product formed in the cavity 6 is extracted from the mold by the action of a molded product ejection pin (not shown).

When the local heating section 12 is provided at the tip of the runner heating cylinder 11 as shown in the figure, the section 12 is intermittently heated every time the injection mechanism 9 performs an injection operation. 8
The solidified resin in the gate 8 is locally heated and melted to allow the resin to flow through the gate 8 to perform the molding operation.

The general outline of conventionally known injection molding equipment and injection molding methods has been explained above, but in such conventional examples, the injection pressure must be increased to meet the current diversified demands for precision molding, high quality processing, etc. , it is necessary to deal with higher resin heating temperatures and an increase in hydraulic mold clamping force, which inevitably increases the size and cost of the equipment.

By the way, in the conventional example, since the pair of molds 3a and 3b forming the cavity 6 are constantly cooled by the cooling action of the cooling water passing through the cooling water circulation holes 13, the inner surface of the cavity 6 is also cooled. Forced. Therefore, by the action of the injection mechanism 9, the cavity 6 is cooled while the molten resin flows into the cavity 6 through the gate 8.
It is rapidly cooled on the inner surface, tends to solidify, reduces fluidity, and increases so-called flow resistance, that is, contact resistance, and therefore has no choice but to rely on increased injection pressure and temperature rise of the molten resin.

Moreover, if the high-temperature molten resin comes into contact with the air inside the cavity 6, there is a risk that the resin will be oxidized and deteriorated.
There is a disadvantage that vacuum treatment must be performed. □ [Object of the invention] This invention was made by focusing on the above points, and the mold 3a
, the inner surface of the cavity 6 of 3b is locally heated to keep it warm, and the inflow operation of the injected molten resin is performed smoothly and effortlessly, and injected at a low injection pressure with perfect fluid fluidity.
In addition, the molten resin is poured into the cavity 6 at an appropriate melting temperature, eliminating the disadvantage of resin oxidation and deterioration due to high temperatures, and providing a high quality synthetic resin injection molding method and apparatus with excellent moldability. It is about providing.

[Structure of the invention]

That is, in this invention, the cavity mold parts 7a and 7b of the pair of molds 3a and 3b forming the cavity 6 are locally heated and kept warm each time an injection molding operation is performed, and the cavity 6 is kept warm. The present invention relates to a synthetic resin injection molding method in which an injection molding operation is carried out, and a synthetic resin injection molding apparatus equipped with a heating mechanism that locally heats both cavity mold parts 7a and 7b in a cavity 6 when the mold is opened.

〔Example〕

Examples of the present invention will be described below with reference to the drawings. Components that are the same as or correspond to those of the conventional example are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

Reference numeral 14 denotes a heating mechanism which is arranged between the two molds 3a and 3b when they are open, and can escape to another position when the molds are closed.

Reference numeral 15 designates a mask having a heat-insulating structure, which has holes 16 for locally applying heat only to the cavity type 1 (S7a, 7b) of the cavity 6, such as one molded product or two or more multiple molded products. They are provided on both sides of the heating mechanism 13. In the figure, there are four holes 16, so four holes 16 are bored. 017 indicates a heater arranged inside the hole 16, and in the figure, the mask 15 The mask 15 is arranged so that a heat generating body of your choice can be placed in a desired state and the thermal energy to be radiated is not released to the outside by the mask 15. It radiates directionally toward the opening surface to the cavity mold parts Ta and γb to form the part 7a.
, 7b can be locally heated. 18 is a circulation hole for a cooling medium such as cooling water provided in the mask 15;
When the mask 15 comes into contact with the molds 3a and 3b, the heater 11
The structure is such that parts other than the cavity mold parts 7a and 7b are not heated. Reference numeral 19 indicates piping for introducing and extracting a cooling medium into the communication hole 18.

By the way, if the injection molding method is a runner type,
Since the gate 8 is not heated or not heated prior to the molding operation, the configuration of the heating mechanism 14 shown in FIG. 3 may be used, but if the injection molding method is a runnerless method,
Since the resin is always exposed to the gate portion 8, a structure is required to prevent the resin in the gate portion 8 from melting due to the heating action of the heating mechanism 14. Reference numeral 20 denotes a presser rod for locally covering the gate 8 and moving the heating, and is inserted and fixed into the hole 16 of the mask 15 so as to contact the gate 8 of the cavity mold part γa. Reference numeral 21 denotes a flow hole in the presser rod 20, which is configured to supply a desired cooling medium, ie, water or gas, from the outside of the heating mechanism 14 through a pipe 22 as necessary.

Furthermore, the cavity mold portions γa and 7 forming the cavity 6 are
Temperature sensors (not shown) are buried in necessary locations inside b to detect when the cavity mold parts 7a and 7b are heated to a predetermined temperature. After detecting that the set temperature has been reached, the heating operation of the heating mechanism 14 can be automatically stopped.

The heating mechanism 14 is located between the molds 3a and 3b, and controls the molding apparatus main body a by an appropriate control mechanism before and after the operation of heating the cavity mold portions 7a and γb of the molds 3a and 3b. Allows temporary escape above or to the side.

Further, the surfaces of the cavity mold parts 7a and γb forming the cavity 6 described above are subjected to induction hardening,
Secondary processing may be performed to give a skin effect and obtain a heat storage effect by external heating 6.51. .

The molding method according to the present invention will be explained based on the above structure.

As shown in FIG. 4(a), when the molds 3a and 3b are in the open state, the heating mechanism 14, which is located at the chain line position, is moved into the molds 3a and 3b as shown by the solid line arrows, and is maintained at the solid line position.

Next, the mold 3b is moved in the direction of the arrow by the moving operation of the moving plate 2, and both molds 3a and 3b are moved as shown in FIG. 3).
3b sandwich the heating mechanism 14. In this state, the mask 15 of the heating mechanism 14 has the holes 16 positioned relative to the cavity mold parts γa and 7b as shown in FIG. 3 or 7, and only these cavity mold parts γa and 7b can be locally heated. It can be a state. In the case of FIG. 7, since the runnerless molding method is used, the tip of the presser rod 20 covers the gate 8 to prevent it from being heated.

After the position in this state is detected, the heater 11 of the heating mechanism 14 is ignited and passes through the hole 16 to each cavity mold part 7.
Heat a + 7 b. A temperature suitable for the heating temperature depending on the resin used is set in advance, and the temperature for locally heating the cavity mold parts 7a, 7b is set using a sensor buried near the cavity mold parts 7a, 7b. The heating mechanism 14 stops heating the heater when it is detected by the sensor and is sufficiently heated, the mold is opened once to the state shown in FIG. 4(a), and the heating mechanism 14 escapes to the chain line position as shown by the chain line arrow. Immediately, as shown in FIG. 3(C), both molds 3a and 3b are closed, that is, closed, and a normal injection molding operation is performed.

However, during the heating operation of the heating mechanism 14, the cavity mold part 7a
, 7b so that parts other than 7b are not heated unnecessarily.
Of course, the cooling medium from 9 is forced to flow into the communication holes 18 of the mask 15.

In this way, the high temperature molten resin injected by the injection mechanism 9 is injected from the runner 10 through the gate 8 into the cavity 6.
Since a and γb are preheated and maintained at the desired temperature, the injected molten resin is in a cold state; it quickly spreads to every corner smoothly and effortlessly without getting wet, completing the injection operation. do.

Then, the molds 3a and 3b perform a mold opening operation, and the mold 3b receives the action of the molded product take-out pin during the mold opening process to take out the desired molded product. Thereafter, the same operation can be repeated repeatedly to perform continuous molding work.

〔Effect of the invention〕

According to the present invention, a plurality of paired molds capable of forming a molded product are heated in advance by locally heating the inner surface of the cavity, that is, the cavity mold portion, each time an injection molding operation is performed, that is, immediately before the injection molding operation is performed. Since the molten resin is injected into the cavity, it will not cool and solidify, and the flow resistance will not increase excessively due to excessive cooling and fluidity. Therefore, it has the advantage of being able to mold a wide range of molded products, from large molded products to small thin-layer molded products, with extremely low injection pressure, and without heating the molten resin to an unnecessarily high temperature. be.

Moreover, with this invention, various high-quality molded products can be produced at low cost using a small injection molding machine, including high-precision molded products at low pressures and low temperatures that were previously considered impossible, such as video molded products such as the CD70 Tsupi. Moreover, it has the characteristic of being able to produce at high efficiency.

In addition, since it is only necessary to add a heating mechanism, the present invention has the advantage that it can be widely provided as a high-quality, high-precision synthetic resin molding machine without being particularly expensive compared to conventional injection molding machines.

[Brief explanation of the drawing]

1 and 2 are an overall view and an enlarged cross-sectional view of a mold section showing a general and schematic configuration of a conventional synthetic resin molding device, and FIG. 3 is a specific example of a synthetic resin molding method according to the present invention. An enlarged cutaway side view showing the mold and heating mechanism of the main parts of the synthetic resin molding apparatus showing an example, FIG. FIG. 5 is an explanatory diagram of the state of the heat exchanger (a) seen from the cross-sectional direction. FIG. 6 is a perspective view showing the general heat of the heating mechanism.
This figure is an enlarged cutaway side view of the main part showing Example 1 in addition to FIG. 3. 1 ・・・・・・・・・ Fixed plate 2 ・・・・・・・・・ Movable plate 3a, 3b ・・・・・・ Mold 6 ・・・・・・・・・ Cavity 1a, γb ・... Cavity mold part 8 ...
...... Gate 9 ...... Injection mechanism 10 ...... Runner part 11 ...
...... Runner heating cylinder 12 ......
・ Local heating section 13 ...... Cooling water distribution hole 14 ... Town... Heating mechanism 15 ...... Mask 11 Town... Heater 18 ... River... Cooling medium distribution hole 20 River...
・・・・・・ Presser rod a ・・・・・・・・・ Forming device main body Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] +11 When a plurality of paired molds are closed, molten resin is injected into the cavity constituted by the molds by a desired injection means, and after solidification, the molds are separated and the inside of the cavities is injected. A synthetic resin injection molding method in which a molded product is taken out, in which the inner surface of a mold cavity is locally heated and kept warm each time a molten resin is injected. (2) The synthetic resin injection molding method according to claim 1, wherein the inner surface of the cavity of the mold is locally heated from the contact/separation opening/closing surface side of the υ mold by a desired heating means. (3) An injection mechanism for injecting the desired molten resin, a plurality of molds that are paired with each other and each has a cavity mold part that can form a cavity, and a desired mold clamping mechanism that can open or close the molds. A synthetic resin injection molding apparatus comprising a heating mechanism that is sandwiched between a plurality of molds and can locally heat a cavity mold part. (4) The synthetic resin injection molding apparatus according to claim 3, wherein the heating mechanism includes a mask having a heat-insulating structure and having holes on both sides for locally heating the cavity mold part. (5) The synthetic resin molding apparatus according to claim 4, wherein the mask includes a presser rod that locally covers the gate of the cavity mold portion to prevent heating.