JPH06344370A - Mold press molding method and mold assembly therefor - Google Patents

Abstract

PURPOSE:To eliminate molding defect of burrs, short shot and the like by absorbing differences of a packing quantity of resin materials injected into each cavity in a multi-cavity mold press molding method. CONSTITUTION:In an injection molding machine 20, a somewhat excessive packing quantity of resin materials is injected and packed in each of cavities A, B through hot runners 32 and gates 33, and, in each of the cavities A, B, the capacity of the same is expanded by cavity capacity regulating mechanisms 50 for absorbing the excessively packed resin materials, whereby the internal pressure in the cavities A, B is maintained at a constant level to prevent burrs from being caused, and molded articles having no molding defect of short shot and burrs can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold press molding method suitable for molding automobile interior parts and a molding die device for molding the same.

[0002]

2. Description of the Related Art For example, there is a mold press molding method as a method for molding automobile interior parts.

According to this mold press molding method, a semi-molten resin material is distributed and supplied into the upper and lower molds for mold press molding, and by clamping the upper and lower molds, interior parts with little material loss and excellent moldability can be obtained. It is possible to obtain.

In order to carry out this mold press molding method, as shown in FIG. 5, a resin is applied between the upper and lower mold press molds 1 and 2 which can be engaged and tightened and have a desired cavity shape. The molded body is molded, and the resin material is supplied by the injection molding machine 3 connected to the lower mold 1.
Through.

That is, the molten resin is supplied from the nozzle 3a of the injection molding machine 3 to the hot runner 4 formed in the lower mold 1, and the mold of the lower mold 1 is passed through a plurality of gates 5 branched from the hot runner 4. Molten resin is distributed and supplied onto the surface.

In molding mass-produced products such as automobile interior parts, in consideration of molding efficiency, multi-mold press molding is often performed to obtain a plurality of molded products in one press step.

That is, as shown in FIG. 6, the case of taking two pieces will be described as an example. The pair of lower molds 2 are symmetrically mounted on the receiving plate, and the mold surface shape of the upper mold 1 is left and right. It is set to be symmetrical.

Then, a molten resin material is injected and filled from the injection molding machine 3 through the hot runner 4 and the gate 5 into the cavities a and b formed by the upper and lower molds 1 and 2, and molding is performed in accordance with the shapes of the cavities a and b. The product is molded.

[0009]

However, in the conventional multi-mold molding press molding method, although the cavity volumes a and b are the same, the injection molding machine 3 is used.
Therefore, the amounts of the resin material injected and filled into the cavities a and b through the hot runner 4 and the gate 5 are not always the same.

This means that when there is a temperature difference in the hot runner 4 for supplying the resin to each of the cavities a and b, the fluidity of the molten resin differs depending on each gate, or the unmelted resin remains or the spool remains. The change in the flow resistance of the molten resin due to the inclusion of foreign matter in the resin or the like also causes a difference in the supply amount of the resin material to the cavities a and b.

As described above, if the amounts of resin injected and filled in the cavities a and b are not the same, one side is overfilled and burrs are easily generated, and a short shot due to defective filling is generated on the other side.

The present invention has been made in view of the above circumstances, and in a multi-cavity mold press molding method, molding defects such as burrs and short shots can be reliably prevented and the productivity can be remarkably improved. An object of the present invention is to provide a mold press molding method and a molding die device for the molding method.

[0013]

In order to achieve the above-mentioned object, the present invention is designed so that a plurality of cavities formed between upper and lower molds for mold press molding are injected and filled with a resin material by an injection molding machine. In the multi-cavity mold press molding method in which molded products are molded and press-molded, a slightly larger amount of resin material than the reference volume of each cavity is injected and filled into each cavity from an injection molding machine, and the upper and lower mold press molding dies During mold clamping, the internal pressure of the cavity is always kept constant by absorbing excess resin material into the cavity volume adjustment space that communicates with the cavity from the time when the internal pressure of the cavity reaches a predetermined pressure to the end of molding. It is characterized by

Furthermore, the molding die apparatus used in the method of the present invention distributes and supplies the resin material into the cavity through the upper and lower molds for molding press forming a desired cavity space and the gate formed in the lower mold. And a cavity capacity adjusting mechanism for adjusting the capacity of the cavity according to the cavity internal pressure.

[0015]

As apparent from the above construction, the resin material injected from the injection molding machine into each cavity through the hot runner and the gate is slightly larger than the reference volume, that is, it is overfilled. There will be no short shots.

Further, since the excess portion of the resin material which is overfilled in each cavity is accommodated in the cavity volume adjusting space formed in communication with the cavity according to the cavity internal pressure, the cavity internal pressure is always kept constant. Therefore, burrs do not occur.

Furthermore, since the internal pressure of the cavity is always kept constant, an unreasonable load is not applied to the press machine.

[0018]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIGS. 1 and 2 are a side view and a sectional view of a mold press molding apparatus used in the method of the present invention, and FIG. 3 is a sectional view showing a state of the mold press molding apparatus during press molding, and FIG. FIG. 3 is a cross-sectional view of the main parts showing the configuration of another embodiment of the mold press molding die device according to the present invention.

First, referring to FIGS. 1 and 2, the overall structure of the mold press molding apparatus used in the method of the present invention will be described.

The mold press molding apparatus comprises a mold press molding die 10 and an injection molding machine 20 connected to the mold press molding die 10. In the mold press molding die 10, a lower die 30 having a desired die surface shape is a receiving plate. It is fixed at 31,
In order to supply the resin material from the injection molding machine 20 to a predetermined position on the die surface of the lower die 30, a hot runner 32,
A gate 33 is drilled.

Above the lower die 30, an upper die 40 having a die surface substantially the same as the die surface shape of the lower die is provided on an upper table 41.
The upper table 41 is vertically movable by an elevating device (not shown).

The injection molding machine 20 supplies a pelletized material from a hopper 21, heats and melts it with a screw 22, and then a hot runner 32 of a lower mold 30 through a nozzle 23.
It is configured to be supplied to.

Further, the mold press molding apparatus used in the present invention is a multi-cavity molding apparatus for simultaneously molding a plurality of molded products, and as shown in FIG. A pair of lower molds 30 is installed in the.

Therefore, in the hot runner 32, the resin material is injected and filled into the cavities A and B from the two branched hot runners 32a and 32b through the gates 33a and 33b, respectively.

By the way, the feature of the mold press molding apparatus used in the method of the present invention is that the resin material injected and filled in the individual cavities A and B is slightly overfilled, and by doing so, a short circuit caused by defective filling is caused. By reliably preventing shots and varying the cavity capacity with respect to excess resin material, the cavity A,
The internal pressure of B is always kept constant, forming defects such as burrs are eliminated, and productivity is remarkably improved.

That is, the constructional feature is that the cavity capacity adjusting mechanism 50 is installed in the lower mold 30.

In this embodiment, the cavity capacity adjusting mechanism 50 includes a cushion pin 5 installed on the lower mold 30.
1 is urged upward by the spring 52, and the tip surface 51a of the cushion pin 51 is installed so as to form a cavity surface before molding.

The spring 52 is the spring receiver 5
The upper limit position of the cushion pin 51 is regulated by the stopper ring 54, and the spring pressure of the spring 52 can be adjusted by the adjusting bolt 55.

As described above, the cavity capacity adjusting mechanism 50 including the cushion pin 51 spring-biased by the spring 52 is set for each of the cavities A and B.

Next, referring to FIG. 3, the method of the present invention using the mold press molding apparatus having the above-mentioned structure will be described. First, the injection molding machine 20 to the hot runner 3 will be described.
The resin material to be injected and filled into the cavities A and B through the holes 2a and 32b and the gates 33a and 33b is slightly overfilled so as to prevent defective filling in the cavities A and B.

Then, the upper mold 40 descends, and the upper and lower molds 30,
The resin filled in the cavities A and B is subjected to the cavity internal pressure by the engagement pressure tightening of 40, but since the resin material is filled in slightly more than the cavity capacity of the cavities A and B, the upper mold 40 moves down for a predetermined stroke, but reaches a predetermined reference internal cavity pressure by the time it reaches the lowermost position.

With the conventional die structure, when the upper die 40 is continuously lowered to reach the lowermost position, the burr is unavoidable due to the overfilling state. The cavity volume adjusting mechanism 50 is installed so that the internal pressures of A and B are always kept constant, and the cushion pin 51 is pressed downward by the internal cavity pressure to form the cavity volume adjusting space indicated by S ₁ and S 2. The space capacities of the cavities A and B are expanded by the cavity capacity adjusting spaces S ₁ and S ₂ , so that the space internal pressure is always maintained constant.

Therefore, molding defects such as burrs due to overfilling do not occur at all.

At this time, the cushion pin 51 is biased upward by the spring 52, and the internal pressure of the cavity is lower than the spring pressure of the spring 52.
This is a mechanism in which the cushion pin 51 is pressed downward by overcoming the spring pressure of 1. The spring pressure of the spring 52 can be appropriately adjusted by the adjusting bolt 55.

When the molding is completed, the spring 52
The cushion pin 51 moves upward due to the spring pressure of
The stopper ring 54 hits the lower surface of the receiving plate 31, and the tip end surface 51 a of the cushion pin 51 constitutes the mold surface of the lower mold 30.

Thus, according to the method of the present invention, the lower mold 3
The cavity capacity adjusting mechanism 50 is installed at 0 to inject the resin material into the cavities A and B with a slight overfilling effect to surely eliminate short shots. Is eliminated, molding defects such as burrs due to overfilling are eliminated, the defect rate can be significantly reduced, and the product yield is significantly improved.

Further, conventionally, it was necessary to strictly control the mold temperatures of the molds 30 and 40 and various molding conditions in order to avoid defective molding. However, according to the method of the present invention, the cavity volume is increased. The adjusting mechanism 50 enables molding even under relatively rough conditions, which is also a major factor in improving productivity.

In addition, since the internal pressures of the cavities A and B are always constant, there is an advantage that an unreasonable load is not applied to the press device connected to the upper mold 40 and the durability of the press device is improved.

Next, FIG. 4 shows a cavity capacity adjusting mechanism 5.
No. 0 shows the configuration of another embodiment, and an air cylinder 56 may be connected to the cushion pin 51 inserted into the opening of the lower mold 30, and the air valve resistance may be adjusted by the relief valve 57.

In the figure, reference numeral 58 is a check valve, and 59 is a filter. According to this embodiment, the cushion pin 5
The reaction force of 1 can be adjusted more easily.

A hydraulic cylinder can be used instead of the air cylinder 56.

Next, the manufacturing process of an automobile door trim will be specifically described by using the method of the present invention.

(Example 1) Nozzle 23 of injection molding machine 20
Through hot runner 32 and gate 33 through PP
A resin material (composite resin material containing 90 parts by weight of PP resin and 10 parts by weight of talc) was injected and filled in cavities A and B of 4000 g.

At the same time as the resin material is injected and filled in each of the cavities A and B, as shown in FIG.
Is further lowered to the lowermost position, and the upper and lower molds 30 and 40 for press molding are tightened with pressure (press pressure 80 kg / c
m ² and press time 30 seconds), the upper mold 40 moves up and the resin molds A and B molded along the shapes of the cavities A and B are released from the lower mold 30. did.

At this time, the balance of the injection amounts of the cavities A and B is lost due to the influence of the temperature at the time of injection, and when the cavity A is 1920 g and the cavity B is 2080 g, when the press is performed, the cavity B is pressed. On the side, the mold pressure reaches the set pressure first.

However, since the cavity A has not reached the set pressure, the upper die 40 descends until the cavities A and B reach the set pressure, and the cavity B which has reached the set pressure earlier. The cushion pin 51 is lowered and pressed until the cavity A reaches the set pressure, and as a product, 160 g of the product in the cavity B is absorbed by the cushion pin 51.

The resin moldings A and B show no occurrence of short shots, no burrs due to overfilling, and a door trim made of an excellent resin molding along each cavity A and B shape. was gotten.

It should be noted that a convex portion is formed on the back surface of the resin molding B, which has no influence on the external appearance, and the capacity (160 g) of the convex portion is a cavity formed according to the descending stroke of the cushion pin 51. This is an enlarged portion of the cavity corresponding to the capacity adjusting space S ₂ .

[0050]

As described above, the present invention has the following special operational effects.

(1) In the method of the present invention, in a multi-mold molding press molding method, a short shot is surely prevented and an excessive material is injected by injecting and filling a slightly overfilled resin material into each cavity. By providing a cavity capacity adjustment mechanism that accommodates the internal pressure of the cavity, the burr generation due to overfilling can be prevented, and burrs, short shots, etc. can be formed in a multi-cavity mold press molding method. This has the effect that defects can be reliably prevented and moldability can be significantly improved.

(2) According to the method of the present invention, the cavity capacity adjusting mechanism is provided, and the cavity is slightly filled with the resin material which is slightly overfilled.
Since the excess amount is absorbed, even if there is a slight gap in the resin material distributed to each cavity, the difference can be absorbed by the cavity volume adjustment mechanism, so the mold temperature and molding Since the conditions and the like can be set relatively rough, there is an effect that productivity can be improved.

(3) According to the method of the present invention, since the excess amount of the resin material injected and filled in the cavity can be absorbed by the cavity volume adjusting mechanism, the internal pressure of the cavity is always kept constant and the cavity is connected to the upper mold. There is an effect that durability of the pressing device can be improved without applying an unreasonable load to the pressing device.

(4) A mold press molding die apparatus according to the present invention is provided with a cavity capacity adjusting mechanism composed of a cushion pin on the lower die, and the cushion pin is controlled by spring force of a spring or air pressure or hydraulic pressure of an air cylinder. It is a structure that biases the spring toward the cavity side, and adjusts the spring pressure of the spring with an adjustment bolt,
Since the air pressure of the air cylinder can be adjusted by the relief valve, there is an effect that the bearing pressure that matches the molding conditions of the molded product can be set.

[Brief description of drawings]

FIG. 1 is a side view showing the overall configuration of a mold press molding apparatus used in the method of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view showing a molding state of the molding apparatus shown in FIG.

FIG. 4 is a cross-sectional view of essential parts showing the configuration of a second embodiment of the mold press molding apparatus used in the method of the present invention.

FIG. 5 is a side view showing a conventional mold press molding apparatus.

6 is a sectional view taken along line VI-VI in FIG.

[Explanation of symbols]

10 Mold for Molding Mold 20 Injection Molding Machine 30 Lower Mold for Mold Press Molding 32 Hot Runner 33 Gate 40 Upper Mold for Mold Press Molding 50 Cavity Capacity Adjusting Mechanism 51 Cushion Pin 52 Spring 54 Stopper Ring 55 Adjust Bolt 56 Air Cylinder 57 Relief valve A, B Cavities S ₁ , S ₂ Cavity capacity adjustment space

Claims (5)

[Claims] 1. Upper and lower molds (30, 4) for mold press molding
In a multi-cavity mold press molding method in which a plurality of cavities (A, B) formed between 0) are injected and filled with a resin material by an injection molding machine (20) and a plurality of molded products are mold press molded, From the injection molding machine (20), a little more resin material than the reference capacity of each cavity (A, B) is loaded into each cavity (A, B).
B) is injected and filled, and when the upper and lower molds (30, 40) for mold press molding are clamped, an excess amount of resin material is removed from the cavity (A) after the internal pressure of the cavity reaches a predetermined pressure until the molding is completed. , B) and the cavity volume adjusting space (S ₁ , S ₂ ) communicating with the cavity capacity adjusting space (S ₁ , S ₂ ) to keep the internal pressure of the cavity (A, B) constant at all times. 2. A precut skin material is set in advance on the cavity surface of a mold press molding upper die (40) to mold a core material of a required shape by mold press molding, and the skin material is formed on the surface of the core material. The mold press molding method according to claim 1, further comprising: 3. Mold press molding upper and lower molds (30, 40) for forming a desired cavity (A, B) space.
And an injection molding machine (20) for distributing and supplying a resin material into the cavities (A, B) through a gate (33) formed in the lower mold (30), and the cavity internal pressure of each cavity (A, B). A mold apparatus for mold press molding, which comprises a cavity capacity adjusting mechanism (50) for adjusting the capacity of the cavity accordingly. 4. A cavity capacity adjusting mechanism (50) comprises a cushion pin (51) which is vertically movably inserted into a lower mold (30) and a cushion pin (51) which is urged upward. The tip surface (51a) of 51) constitutes a part of the cavity surface.
2) and an adjusting bolt (55) for adjusting the spring pressure of the spring (52), and during the mold press molding, after the internal pressure of the cavity reaches a predetermined pressure, the cavity is lowered according to the internal pressure and the descending stroke The mold apparatus for mold press molding according to claim 3, wherein the cavity volume adjusting spaces (S ₁ , S ₂ ) are formed in accordance with the above. 5. The cavity capacity adjusting mechanism (50) is inserted into a lower mold (30) and, when it is lifted, a vertically movable cushion pin (5) whose front end surface forms a part of the cavity surface.
1) and a driving air cylinder such as an air cylinder (56) that drives the up and down movement of the cushion pin (51),
It is composed of pressure adjusting means such as a relief valve (57) for adjusting the air pressure of the air cylinder (56), and after the internal pressure of the cavity reaches a predetermined pressure during mold press molding,
The cushion pin (51) descends according to the internal pressure, and the cavity volume adjustment space (S
_{1. The} mold apparatus for mold press molding according to claim 3, wherein ₁ , ₁ and S ₂ are formed.