JP2006056006A - Injection foam molding method and injection foam molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection foam molding method capable of preventing a swirl mark or silver from appearing on the surface of a molded product at injection foam molding due to an injection molding machine for successively injecting a foamable resin in a plurality of mold cavities different in resin filling volume to fill the mold cavities, and an injection foam molding machine. <P>SOLUTION: In the injection foam molding method for injecting the foamable molten resin in the mold cavities within a mold unit from an injection unit to mold the molded products, when the pressurized foamable resin is injected in the mold cavities to fill the mold cavities, a resin injecting/filling speed is controlled so that the time required until the flow leading end parts of the resin in the mold arrive at the terminal in the mold cavities is made markedly shorter than a foam forming time and the surfaces of the resin are solidified before the foams on the surfaces of the resin coming into contact with the mold cavities are grown and the core parts of the molded products become a foamed resin material filled with grown foams. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an injection foam molding method using a mold having a plurality of mold cavities having different shapes and sizes, and in particular, injection foam molding in which the injection speed is individually controlled for each mold cavity. The present invention relates to a method and an injection foam molding machine.

  Injection foam molded products by injection molding machines are hardened with the surface non-foamed, then the interior is highly foamed with the aim of making the appearance look good and light molded products. After the foaming resin is injected into the mold at high pressure and the surface of the molded product that is in contact with the mold is cooled and hardened, the mold cavity volume is expanded to lower the internal pressure of the molded product. 2. Description of the Related Art Conventionally, an injection foam molding method for foaming the inside of a product is known.

  However, such an injection-foamed molded product can trap the foaming gas generated by the resin pressure suddenly dropping when the foamable resin is injected, or expand the mold cavity to the molded product volume. When the surface solidification layer cannot follow the movement of the inner surface of the mold, it peels off from the inner surface of the mold, and a free solidified surface of the resin that does not follow the inner surface of the mold is generated. Marks) and silver (silver stripes) are likely to occur.

  Conventionally, in order to prevent this, for example, a solidified layer and an inner part that are in contact with the mold surface after completion of injection filling are prepared by completely filling the melted foamable plastic composition by reducing the volume of the cavity during or immediately after injection. A method has been proposed in which, after cooling to a state in which a molten layer is mixed, the volume of the cavity is expanded to the volume of the target molded product and further cooled, and then the foamed plastic molded product is taken out (for example, Patent Document 1). .)

  In addition, a method has been proposed in which a mold having a heat insulating layer on the mold cavity surface is used, the injected foamable resin is brought into pressure contact with the mold cavity surface, and then the mold cavity volume is expanded to foam the inside. (For example, patent document 2).

JP-A-8-300392 JP 2000-71277 A

  In both of the above-mentioned conventional proposals described in Patent Document 1 or Patent Document 2, when the mold is opened and closed for foaming, the mold is moved to a fixed position at a constant speed. When it is difficult to respond to changes in temperature conditions and the mold moving speed is too fast, expansion due to foaming is not in time, and foaming gas or air enters between the molded product and the mold, and when the mold moving speed is slow The resin hardens during the expansion of the foam, and the foaming gas and air can get into the space between the molded product and the mold. In either case, there is a possibility that the swirl mark (foaming gas mark) or silver (silver stripe mark) There is a problem that there is.

Further, there is a problem that a mold having a plurality of mold cavities having different shapes and sizes cannot be adopted because the injection conditions differ depending on the shape and size of each mold cavity.
The present invention has been proposed in order to solve the above-described problems, and in a mold having a plurality of mold cavities having different shapes and sizes, when the foamable resin is sequentially injected and filled into the plurality of mold cavities. An object of the present invention is to provide an injection foam molding method and an injection foam molding machine that can prevent swirl marks and silver from appearing on the surface of a molded product.

  The present invention has been made in order to solve the above-described conventional problems, and each of the inventions described in the claims as an injection foam molding method and an injection foam molding machine are the following (1) to (10). ) Are used.

  (1) The first means is an injection foam molding method in which a foamable molten resin is injected from an injection unit into a mold cavity in a mold unit to mold a molded product, and the mold cavity is pressurized. When the foamable resin is injected and filled, the time required for the resin flow front end in the mold cavity to reach the end in the mold cavity is much shorter than the foam generation time, and the foam bubbles on the resin surface in contact with the mold The resin injection rate is controlled so that the resin surface is solidified before the resin grows and the core part of the molded product becomes a foamed resin material filled with the grown bubbles.

  (2) The second means uses a mold unit having a plurality of mold cavities having different shapes and sizes and a resin passage for each mold cavity, and the foamable molten resin is injected into the mold unit from the injection unit. In the injection foam molding method for molding a plurality of molded articles by injection, a resin passage and a resin gate opening / closing means are provided in each mold cavity, and the resin gate opening / closing means is opened into the first mold cavity and pressurized. After the predetermined amount of foamable resin is injected and filled, the resin gate opening / closing means is closed, and then the resin gate opening / closing means is opened into the second mold cavity to apply the pressurized predetermined amount of foamable resin. After injection filling, the resin gate opening / closing means is closed, and similarly, the resin gate opening / closing means is opened / closed into the mold cavity, and a predetermined amount of resin is injected and filled in order, so that all the mold cavities are filled. The time for the resin flow tip to reach the end of the cavity is much shorter than the foam generation time, and the resin surface solidifies before the foam bubbles grow on the resin surface in contact with the mold. The resin injection and filling speed is controlled so that the foamed resin material is filled with water.

  (3) The third means is characterized in that, in the injection foam molding method according to the first or second aspect, the time required for injection filling into the mold cavity is 1 second or less.

  (4) The fourth means is the injection foam molding method according to any one of the first to third aspects, wherein a resin reservoir is provided at a terminal side of the mold cavity, and the resin expands and expands and leaks from the mold cavity. It is characterized in that it is accommodated.

  (5) The fifth means is the injection foam molding method according to any one of the first to third aspects, wherein a projecting core that can be put in and out of the mold cavity is provided, and the volume of the foamed and expanded resin is accommodated. It is characterized by that.

  (6) An injection foam molding machine according to a sixth means is an injection foam molding machine in which a foamable molten resin is injected and filled into a mold unit by an injection unit to form a plurality of molded products. A plurality of mold cavities having different shapes and sizes, a plurality of resin passages respectively connected to the plurality of mold cavities, a plurality of resin gate opening / closing means for opening and closing the resin passages, and the mold And a control device for opening and closing the plurality of resin passages by the plurality of resin gate opening and closing means in order to sequentially inject and fill the foam cavity with the foamable molten resin.

  (7) The seventh means is the injection foam molding machine according to the sixth aspect, wherein the control device controls the injection speed in accordance with a preset injection screw stroke and injection speed pattern and fills each cavity. After completion, pressurize the resin, reset the screw position after pressure release as the injection start position to the next cavity, and control the injection speed according to the preset injection screw stroke and injection speed pattern Features.

  (8) The eighth means is the injection foam molding machine according to the sixth or seventh aspect, wherein the plurality of resin reservoirs respectively connected to the plurality of mold cavity end sides, and the plurality of mold cavities from the plurality of mold cavities. And a plurality of heating means respectively provided in the passage to the resin reservoir.

  (9) The ninth means is the injection foam molding machine according to the sixth or seventh aspect, wherein the plurality of projecting cores respectively provided in the plurality of mold cavities so as to be able to enter and exit, and the operations of the plurality of projecting cores. And a hydraulic circuit to be controlled.

  (10) A tenth means is the injection foam molding machine according to the ninth aspect, wherein the hydraulic circuit for controlling the operation of the protruding core is a pipe connected to a core cylinder chamber in which the plurality of protruding cores are housed. And a plurality of compression springs for urging the plurality of projecting cores toward the mold cavity, and a plurality of flow rate adjusting valves respectively interposed in the plurality of pipes.

The invention according to each claim described in the claims employs the means described in the above (1) to (10), and thus has the following effects.
(1) Since the invention according to claim 1 employs the first means, injection foaming in which a foamable molten resin is injected from an injection unit into a mold cavity in the mold unit to mold a molded product. In the molding method, when injecting and filling pressurized foamable resin into the mold cavity, the time required for the resin flow front end in the mold cavity to reach the end in the mold cavity is significantly higher than the foam generation time. The resin injection rate is controlled so that the resin surface solidifies before the foam bubbles grow on the resin surface in contact with the mold, and the core of the molded product becomes a foamed resin material filled with the grown bubbles. As a result, the foam surface of the molten gas accompanying the decrease in the internal pressure of the resin merges and the resin surface solidifies before it grows into large particles, so that no noticeable foaming marks appear on the surface of each molded product, and the skin of the molded product is hard Become strong, And, since the slow bubble core portion is large bubbles grow are generated, light and durable molded article is obtained.

(2) Since the invention according to claim 2 employs the second means, a mold unit having a plurality of mold cavities having different shapes and sizes and a resin passage for each mold cavity is used. In an injection foam molding method in which a foamable molten resin is injected from an injection unit into a mold unit to form a plurality of molded products, out of a plurality of mold cavities, from a mold cavity having a long cooling time after filling with resin In order, each mold cavity is provided with a resin passage and a resin gate opening / closing means, and after the resin gate opening / closing means is opened into the first mold cavity, a predetermined amount of foamable resin is injected and filled, The resin gate opening / closing means is closed, then the resin gate opening / closing means is opened into the second mold cavity to inject and fill a predetermined amount of foamable resin, and then the resin gate opening / closing means is closed. Likewise By sequentially opening and closing the resin gate opening and closing means into the mold cavity injection filling a predetermined amount of resin, it is possible to the time of the entire injection process cycle the shortest.
Furthermore, the time for the resin flow front end in all the mold cavities to reach the end of the cavity is much shorter than the foam generation time, and the resin surface solidifies before the foam bubbles grow on the resin surface in contact with the mold, By controlling the resin injection and filling speed so that the core of the molded product becomes a foamed resin material filled with the grown bubbles, before the foamed bubbles of the molten gas accompanying the drop in the resin internal pressure merge and grow into large particles Because the resin surface solidifies, no noticeable foaming marks appear on the surface of each molded product, the skin of the molded product becomes hard and durable, and bubbles grow slowly in the core part, generating large bubbles, A light and durable molded product can be obtained.

  (3) Since the invention according to claim 3 employs the third means, in addition to the effect according to the invention of claim 1 or 2, the time required for injection filling into the mold cavity is all 1 By setting it to 2 seconds or less, the appearance of the surface of the molded product can be improved.

  (4) Since the invention according to claim 4 employs the fourth means, in addition to the effect according to the invention according to any one of claims 1 to 3, a resin is provided on the end side of the mold cavity. Since the reservoir is provided to accommodate the resin that has expanded and expanded and leaked from the mold cavity, it is possible to cover variations in the amount of the injected resin and at the same time, it is possible to perform pressureless foaming.

  (5) Since the invention according to claim 5 employs the fifth means, in addition to the effect according to any one of claims 1 to 3, it can be taken in and out of the mold cavity. Protruding cores are provided to accommodate the volume of foamed and expanded resin, so that injection filling under pressure is possible, and at the same time the projecting core is pushed out, so that the mold cavity has a shape after expansion due to foaming. And a molded product having an accurate expansion coefficient and shape can be obtained.

  (6) Since the invention according to claim 6 employs the sixth means, an injection foam molding machine for molding a plurality of molded products by injecting and filling a foamable molten resin into a mold unit by an injection unit. And a plurality of mold cavities having different shapes and sizes provided in the mold unit, a plurality of resin passages respectively connected to the plurality of mold cavities, and a plurality of resins that open and close the resin passages, respectively. A plurality of molds, comprising: gate opening and closing means; and a controller for opening and closing the plurality of resin passages by the plurality of resin gate opening and closing means in order to inject and fill the foamable molten resin sequentially from the mold cavity. Among the cavities, injection molding is performed in order from the mold cavity having a long cooling time after filling with the resin, and the time for one cycle of the entire injection process can be minimized.

  (7) Since the invention according to claim 7 employs the seventh means described above, in addition to the effect according to the invention according to claim 6, the control device, after completion of each cavity filling, Since the pressure release is performed and the screw position after the pressure release is reset as the injection start position for the next cavity, it is possible to cover the variation in the injection resin amount.

  (8) Since the invention according to claim 8 employs the eighth means, in addition to the effect according to the invention according to claim 6 or 7, each of the plurality of mold cavities is connected to the end side of the mold cavity. A plurality of resin reservoirs and a plurality of heating means respectively provided in the passages from the plurality of mold cavities to the plurality of resin reservoirs, so that the resin filled in the mold cavities expands and expands. In this case, the excess resin is heated by the heating means and smoothly flows out to the resin reservoir, so that pressureless foaming is possible.

  (9) Since the invention according to claim 9 employs the ninth means, in addition to the effect according to the invention according to claim 6 or 7, it is possible to enter and exit each of the plurality of mold cavities. A plurality of projecting cores provided and a hydraulic circuit that controls the operation of the plurality of projecting cores are provided. When the foamed resin is filled, the projecting cores are extruded at a predetermined pressure by the hydraulic circuit, and the mold The cavity can be shaped after expansion by foaming, and a molded product having an accurate expansion rate and shape can be obtained.

  (10) Since the invention according to claim 10 employs the tenth means, in addition to the effect according to the invention according to claim 9, the hydraulic circuit for controlling the operation of the protruding core includes Pipes connected to a core cylinder chamber in which a plurality of projecting cores are housed, a plurality of compression springs for biasing the plurality of projecting cores toward the mold cavity, and a plurality of pipes, respectively. In addition, the projecting core enters the mold cavity by the compression spring before filling with foamed resin, and the projecting core hardly moves in a short time when filling with molten resin. At the time of slow expansion due to foaming of the filled resin, the protruding core is pushed by the foaming pressure as the bubbles grow, and is drawn into the mold side at a predetermined speed by the flow rate adjusting valve. Bubbles grow slowly and feel big There sturdy molded article is obtained lightly generated.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an injection foam molding machine and an injection foam molding method of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view partially showing a cross section of a mold unit having a plurality of mold cavities, an electric injection unit, and a control system according to an embodiment of the present invention.
2 is a cross-sectional view of the mold in FIG. 1, FIG. 3 is a cross-sectional view in the case where the resin reservoir of the mold in FIG. 1 is provided, and FIG. 4 is a case in which the protruding core of the mold in FIG. FIG. 5 is a cross-sectional view and FIG. 5 is a block diagram of the control process of the mold unit and the injection unit in FIG.

First, a mold unit, an injection unit, and a control system will be described with reference to FIGS.
The injection molding machine includes an injection unit 1, a mold unit 5, various pipes, electric wires, a control device, and the like mounted on a common table (not shown).

(Configuration of injection unit)
First, the structure of the injection unit 1 will be described with reference to FIG.
A fixed frame 13 of the injection unit 1 and a moving frame 14 that moves toward the fixed frame 13 on the common table are attached to one end of the common table (not shown).
An injection cylinder 3 is integrally provided at the center of the fixed frame 13.
The tip of the injection cylinder 3 is connected to a support plate 8 of the mold unit 5 described later.

An injection screw 2 is built in the injection cylinder 3 so as to be able to move forward and backward.
One end side of the injection screw 2 is attached to the moving frame 14 so as to be rotatable and restrain movement in the axial direction.
The moving frame 14 is provided with a screw rotation driving motor 4 for rotating the injection screw 2.

A plurality of ball screw nuts 16 are provided around the fixed frame 13 symmetrically with respect to the axis of the injection screw 2.
A ball screw shaft 15 is rotatably inserted into each ball screw nut 16.
One end side of each ball screw shaft 15 is attached to the moving frame 14 so as to be rotatable and restrain movement in the axial direction.
The moving frame 14 is provided with a servo motor 17 that rotationally drives the ball screw shafts 15.
The plurality of ball screw nuts 16, the ball screw shaft 15, and the servo motor 17 constitute an electric ball screw device.

The injection unit 1 is configured as described above, and the foamed resin in the injection cylinder 3 is kneaded by rotating the injection screw 2 by the screw rotation driving motor 4.
Then, by rotating each ball screw shaft 15 synchronously by each servo motor 17, each ball screw shaft 15 advances while rotating inside the ball screw nut 16 in the fixed frame 13.
Along with this, the moving frame 14 and the injection screw 2 also move forward, and the kneaded foamed resin in the injection cylinder 3 is injected into the mold unit 5.

The injection unit 1 and the mold unit 5 are provided with various detectors (not shown) that detect pressure, temperature, position, and the like, and detection signals from these various detectors are transmitted from the control device 40. Input to the control circuit 42.
Then, the control circuit 42 receives the rotation speed signal of the servomotor 17 so that the speed and position of the screw 2 in the injection process of the injection screw 2 are set and stored in the setting device 41 and stored. In addition, the screw rotation driving motor 4 and the servo motor 17 are feedback-controlled.

(Configuration of mold unit)
Next, the structure of the mold unit 5 will be described.
The mold unit 5 includes a support plate 8 fixed on a common base (not shown) of the injection molding machine, a fixed mold 6 disposed in the opposite side of the injection unit 1 in close contact with the support plate 8, and fixed. The movable mold 7 is arranged to face the fixed mold 6 so as to be movable toward the cavity forming surface side of the mold 6, and various pipes, electric wires, a control device, and the like.

  The opposing surfaces of the fixed mold 6 and the movable mold 7 are first, second, and third mold cavities 12a, 12b, and 12c that receive molten resin when the fixed mold 6 is coupled to the movable mold 7. Is formed.

  FIG. 2 shows an example of the first, second, and third mold cavities 12a, 12b, and 12c. The opposing surfaces of the fixed mold 6 and the movable mold 7 are shown in FIG. Thus, the mold cavity 12 is formed.

The movable mold 7 is largely movable in a direction away from the fixed mold 6 when the molded product is taken out.
In addition, a hot runner 9 is mounted in the fixed mold 6 and the support plate 8 at a distance from the fixed mold 6 and the support plate 8.
In the hot runner 9, resin passages 10a, 10b, and 10c that connect the injection cylinder 3 and the first, second, and third mold cavities 12a, 12b, and 12c are formed.
The hot runner 9 is always heated so that the molten resin flowing inside the hot runner 9 does not harden.

The inlet portions 11a, 11b, and 11c to the first, second, and third mold cavities 12a, 12b, and 12c of the hot runner 9 are constricted in a conical shape, and the plunger-shaped resin gate valves 18a, 18b, and 18c It is a valve seat.
Each resin gate valve 18a, 18b, 18c penetrates the hot runner 9 and the support board 8 in a liquid-tight manner, and is coupled to three sets of hydraulic cylinders 19a, 19b, 19c provided on the support board 8.
The inlet portions 11a, 11b, 11c, the resin gate valves 18a, 18b, 18c and the hydraulic cylinders 19a, 19b, 19c form resin gate opening / closing means, respectively.

Each hydraulic cylinder 19a, 19b, 19c is connected to the switching valve 43 via a pipe.
The switching valve 43 is switched by a control circuit 42 in the control device 40.
On the other hand, in the setting device 41, the timing order of the first, second, and third mold cavities 12a, 12b, and 12c in the injection process is set.
At the time of injection molding, the control circuit 42 sends an opening / closing operation signal to the switching valve 43 in accordance with the timing sequence set in the setting device 41, and the switching valve 43 opens and closes the resin gate valves 18a, 18b, 18c. The hydraulic oil is individually pumped to each hydraulic cylinder 19a, 19b, 19c.

Next, based on FIG. 3, the case where the mold resin reservoir 21 is provided in each of the first, second, and third mold cavities 12a, 12b, and 12c will be described.
As shown in FIG. 3, at least one of the first, second, and third mold cavities 12a, 12b, and 12c has a plurality of resin reservoirs 21 formed on the end side thereof. Yes.
The end side of the mold cavity 12 and each resin reservoir 21 are connected to each other by a gap 23 with a spacer 22.
The periphery of the gap 23 is surrounded by a heating means 24 such as an electric heater.

In the above-described configuration, when molten moldable resin is filled into the mold cavity 12, the volume of the resin expands due to foaming, and excess resin protrudes from the mold cavity 12 through the gap 23 into the resin reservoir 21.
At this time, the cooling means of the resin near the end side of the mold cavity 12 is delayed by the heating means 24 around the gap 23.

Further, based on FIG. 4, a case where a protruding core 25 of the mold is provided in each of the first, second and third mold cavities 12a, 12b and 12c will be described.
As shown in FIG. 4, a protruding core 25 is provided in at least one of the first, second, and third mold cavities 12a, 12b, and 12c.
The protruding core 25 is movably provided in a core cylinder chamber 26 provided in the movable mold 7, and the tip of the protruding core 25 enters and exits the mold cavity 12.

The other end of the protruding core 25 is coupled to a ram 29 accommodated in the hydraulic cylinder 30 via a rod 27.
The rod 27 passes through the rod through hole 28 in a non-liquid-tight manner.
In the hydraulic cylinder 30 opposite to the rod 27 of the ram 29, a compression spring 31 for urging the projecting core 25 toward the mold cavity 12 via the ram 29 and the rod 27 is incorporated.
The pressing force of the compression spring 31 is balanced with the foaming pressure in the mold cavity 12.

Both sides (rod side and spring side) of the ram 29 of the hydraulic cylinder 30 are connected to the liquid tank 34 via pipes 33a and 33b.
The liquid tank 34 is provided for collecting and filling the hydraulic fluid in accordance with the change in the volume of the core cylinder chamber 26 accompanying the movement of the protruding core 25.
Further, a flow rate adjusting valve 32 is interposed in the middle of the pipe 33 a connected to the core cylinder chamber 26 through the rod through hole 28 and the chamber on the rod 27 side of the ram 29 of the hydraulic cylinder 30. .

In the above-described configuration, the projecting core 25 protrudes into the mold cavity 12 by the pressing force of the compression spring 31 before filling with the foamable resin.
When the foamable resin is filled into the mold cavity 12, the flow of the hydraulic fluid is throttled by the flow rate adjustment valve 32 in the middle of the pipe 33 a connected to the core cylinder chamber 26 even if the filling resin pressure is high. The protruding core 25 in the core cylinder chamber 26 does not move suddenly.

Thereafter, along with the foaming of the foamable resin, the protruding core 25 gradually moves against the pressing force of the compression spring 31.
Then, the hydraulic fluid in the core cylinder chamber 26 flows to the rod side of the ram 29 of the hydraulic cylinder 30 via the rod through hole 28.
The surplus hydraulic fluid based on the diameter difference between the core cylinder chamber 26 and the hydraulic cylinder 30 is collected in the liquid tank 34 via the pipe 33 a and the flow rate adjustment valve 32.

(Injection molding process)
Next, a control process when injection molding is performed by an injection molding machine will be described based on the control process block diagram of FIG.
The horizontal axis in FIG. 5 is the time axis.

In FIG. 5, a block diagram showing a molten resin injection and plasticizing process by the injection cylinder 3 and the injection screw 2 of the injection unit 1 is shown in the uppermost stage.
Below that, there are a block diagram showing the injection filling process and the foam cooling process of the first mold cavity 12a, and an operation process chart showing the opening and closing timing of the gate valve 18a of the first mold cavity 12a. It is shown.

Similarly, in the lower part of the block diagram and the operation process diagram of the first mold cavity 12a and the resin gate valve 18a, a block diagram showing the injection filling process and the foam cooling process of the second mold cavity 12b, and The operation | movement process figure showing the opening / closing timing of the gate valve 18b of the 2nd metal mold | die cavity 12b is shown.
Similarly, in the lower part of the block diagram and the operation process diagram of the second mold cavity 12b and the gate valve 18b, a block diagram showing the injection filling process and the foam cooling process of the third mold cavity 12c, and The operation | movement process diagram showing the timing of opening and closing of the resin gate valve 18c of 3 mold cavity 12c is shown.

Furthermore, in the lower stage, a stroke diagram showing the forward / backward movement position of the injection screw 2 in accordance with each of the above-described steps, the moving speed (V ₁ , V ₂ , V ₃ ) of the injection screw 2, and the filling time ( The operation process diagram showing _TJ1 , _TJ2 , _TJ3 ) is shown.
S represents the full stroke.

V ₁ , V ₂ , V ₃ and T _J1 , T _J2 , and T _J3 in FIG. 5 are the moving speed and filling of the screw when filling the _first , _second , and _third mold cavities 12a, 12b, and 12c, respectively. Shows time.

When the first, second, and third mold cavities 12a, 12b, and 12c are filled with pressurized foamable resin, the resin flow front ends in the first, second, and third mold cavities 12a, 12b, and 12c The filling time T _J1 , T _J2 , and T _J3 for the portion (flow front) to reach the end of each of the first, second, and third mold cavities 12a, 12b, and 12c are much shorter than the cooling (foaming) time. .
In this way, the foamed bubbles on the resin surface in contact with the first, second, and third mold cavities 12a, 12b, and 12c are solidified before the bubbles grow, and the core of the molded product is filled with the grown bubbles. The resin injection speed is controlled so that the foamed resin material is obtained.

Then, the servo motor 17 controls the rotational speed of the ball screw shaft 15 of the injection unit 1 (that is, the moving speed of the injection screw 2), the rotational torque, and the resin gate valves 18a, 18b, and 18c, respectively. For each of the three mold cavities 12a, 12b, and 12c, injection filling and cooling (foaming) of the molten resin are performed individually in order from the longest cooling time.
After completion of injection filling into the final third mold cavity 12c, the rotation of the ball screw shaft 15 is returned to lower the resin pressure (pressure reduction process), and the injection screw 2 is retreated while rotating, and newly Resin is added into the injection cylinder 3 to perform melt plasticization (plasticization injection screw rotation process).
When the melt plasticization is completed, the injection screw 2 stops rotating.

In the meantime, the mold clamping device (not shown) continues the mold clamping during the foam cooling process, and after all the molded products are cooled and solidified, the pressure is lowered, the molds are opened, and the molded products are taken out. This completes one cycle.
Then, after the mold clamping is performed again, the next injection to molded product extraction process starts.

  Further, as shown in FIG. 5, in the injection filling process of the molten resin by the injection screw 2, after the first injection filling to the first mold cavity 12a and the injection filling to the second mold cavity 12b. At a later time, there is provided a depressurizing and depressurizing process in which the resin pressure due to the depressurization of the servomotor 17 for a short time is removed, the rotation of the servomotor 17 is stopped and the injection screw 2 is stopped by applying a brake.

  In the depressurizing and depressurizing step, when the injection screw 2 is moved forward and the injection filling into the first mold cavity 12a is finished, the resin gate valve 18a is closed, the current of the servo motor 17 is turned off, the torque is reduced to zero, The ball screw shaft 15 is freely rotated to release the resin pressure, and then the rotation shaft of the servo motor 17 is braked to stop the injection screw 2.

The position where the injection screw 2 is stopped in the depressurization and depressurization process is reset as the advance start position of the injection screw 2 for injection filling into the second mold cavity 12b, the resin gate valve 18b is opened, In accordance with the stroke of the injection screw 2 from the position, the servo motor 17 is rotated to control the speed of the injection screw 2.
That is, as shown in FIG. 5, rapidly increasing the speed of the injection screw 2 at the time of the start of injection, then perform the filling and maintaining a constant speed V _2, and decelerates the speed is stopped just before the elapsed filling time T _J2 .
The same applies to the case of shifting to the injection into the third mold cavity 12c.

In the injection filling process and cooling foaming process of each of the first, second and third mold cavities 12a, 12b and 12c, the first, second and third mold cavities 12a, 12b and 12c are as shown in FIG. In the case of the mold cavity 12 having a closed shape, the foamable resin is fully filled in the mold cavity 12, and volume expansion due to foaming is performed by the amount the molded article is reduced in volume by cooling after filling.
The contact surface of the molded product with the mold is quickly cooled to obtain a surface in which foamed bubbles are not noticeable.

When each of the first, second, and third mold cavities 12a, 12b, and 12c is the mold cavity 12 having the resin reservoir 21 as shown in FIG. The resin flows out from the mold cavity 12 through the gap 23 into the resin reservoir 21.
Although the volume of the molded product expands due to foaming after filling, a portion of the volume expanded portion of the molded product is transferred to the resin reservoir 21 by heating the vicinity of the gap 23 with heating means 24 such as an electric heater to delay cooling and solidification. Easily drains.
The contact surface of the molded product with the mold is quickly cooled to obtain a surface in which foamed bubbles are not noticeable.

When each of the first, second, and third mold cavities 12 a, 12 b, and 12 c is a mold cavity 12 having a protruding core 25 as shown in FIG. 4, the protruding core 25 protrudes into the mold cavity 12. In the state, the foamable resin is filled in the mold cavity 12.
At this time, even if the resin pressure is high, the flow rate of the hydraulic fluid is reduced by the flow rate adjusting valve 32 interposed in the middle of the pipe 33a, and the protruding core 25 hardly moves suddenly.

When the filling of the resin is finished and the protruding core 25 continues to be pressed by the foaming pressure, the protruding core 25 is pulled into the movable mold 7 against the pressing force of the compression spring 31, and the molded product is foamed over time. Inflate.
The contact surface of the molded product with the mold is quickly cooled to obtain a surface in which foamed bubbles are not noticeable.

According to the injection foam molding machine and the injection foam molding method of the above-described embodiment of the present invention, the injection start position of the injection screw 2 is reset for each of the first, second, and third mold cavities 12a, 12b, and 12c. Since the injection is performed according to the stroke of the injection screw 2 from the injection start position according to the injection conditions set for each of the first, second, and third mold cavities 12a, 12b, and 12c, the molded product No variation in weight, poor shape, etc. occur.
Further, the mechanism for electrically driving the ball screw shaft 15 does not exceed the planned stop position when the moving speed found in the hydraulic operation is high, and more accurate and precise position and speed control is possible.

  Further, when the first mold cavity 12a is larger and thicker than the second mold cavity 12b, and the third mold cavity 12c is smaller and thinner than the second mold cavity 12b, foaming of the molten resin is performed. The cooling time for the third mold cavity 12c is the shortest, the second mold cavity 12b is the next shortest, the first mold cavity 12a is the longest, and each of the first, second, and third mold cavities 12a. , 12b and 12c, the cooling and foaming process of the resin is performed during the injection filling and foaming cooling process of the next mold cavity, so that the third mold cavity having the shortest cooling time as shown in FIG. Is the last step, the time required for one cycle of the entire injection step can be minimized.

The present invention has been described above with respect to the injection foam molding machine and the injection foam molding method according to the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and has a specific structure within the scope of the present invention. Needless to say, various changes may be made.
Although three mold cavities having different shapes and sizes are shown in the drawing, the present invention is not limited to this. For example, a total of six shapes and sizes of three columns and two rows are different from each other. A mold cavity may be formed, and there may be a mold cavity having the same shape and size among a plurality of mold cavities.

  The resin used for injection foam molding is polypropylene (with talc 15 Wt%), the foaming agent is master batch type 1 W t%, the molded product is length x width x height 250 mm x 350 mm x 90 mm, and the wall thickness is 1.5 mm. Molding was carried out in the case of 3 mm mold cavities of 2 mm and 3 mm.

  As a result of the experiment, the result of the experiment in which each mold cavity was individually filled was as follows.

何れの金型キャビティも、樹脂の充填時間が１秒以下の場合に、成形品の表面は良好な外観という結果が得られた。

In any of the mold cavities, when the resin filling time was 1 second or less, the surface of the molded product had a good appearance.

It is a schematic diagram which shows in part a cross section of a mold unit having a plurality of mold cavities, an electric injection unit, and a control system according to an embodiment of the present invention. It is sectional drawing of the metal mold | die in FIG. It is sectional drawing at the time of providing the resin reservoir of the metal mold | die in FIG. It is sectional drawing at the time of providing the protrusion core of the metal mold | die in FIG. It is a control process block diagram of the die unit and the injection unit in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection unit 2 Injection screw 5 Mold unit 6 Fixed mold 7 Movable mold 8 Support board 9 Hot runner 12 Mold cavity 12a 1st mold cavity 12b 2nd mold cavity 12c 3rd mold cavity 18a , 18b, 18c Resin gate valve 19a, 19b, 19c Hydraulic cylinder 21 Resin reservoir 22 Spacer 23 Clearance 24 Heating means 25 Projection core 26 Core cylinder chamber 27 Rod 28 Rod through hole 29 Ram 30 Hydraulic cylinder 31 Compression spring 32 Flow rate adjustment Valves 33a and 33b Hydraulic circuit 34 Liquid tank 40 Control device 41 Setter 42 Control circuit 43 Switching valve

Claims (10)

In an injection foam molding method for molding a molded product by injecting a foamable molten resin into a mold cavity in a mold unit from an injection unit,
When injecting and filling the foamed resin pressurized into the mold cavity,
The time for the resin flow front end in the mold cavity to reach the end in the mold cavity is much shorter than the foam generation time,
The resin surface is solidified before the foam bubbles grow on the resin surface in contact with the mold, and the core part of the molded product is controlled by the resin injection and filling speed so that it becomes a foamed resin material filled with the grown bubbles. Injection foam molding method. Using a mold unit with multiple mold cavities with different shapes and sizes and resin passages for each mold cavity, foamable molten resin is injected into the mold unit from the injection unit to form multiple molded products In the injection foam molding method to
A resin passage and a resin gate opening / closing means are provided in each mold cavity,
After opening the resin gate opening / closing means into the first mold cavity and injecting and filling a predetermined amount of foamable resin that has been pressurized, the resin gate opening / closing means is closed,
Subsequently, after opening the resin gate opening / closing means into the second mold cavity and injecting and filling a predetermined amount of foamable resin that has been pressurized, the resin gate opening / closing means is closed,
Similarly, by opening and closing the resin gate opening and closing means into another mold cavity and sequentially injecting and filling a predetermined amount of resin,
The time for the resin flow tip in all mold cavities to reach the end of the cavity is much shorter than the foam generation time,
The resin surface is solidified before the foam bubbles grow on the resin surface in contact with the mold, and the core part of the molded product is controlled by the resin injection and filling speed so that it becomes a foamed resin material filled with the grown bubbles. Injection foam molding method.   3. The injection foam molding method according to claim 1, wherein the time for injection filling into the mold cavity is 1 second or less.   The injection foam according to any one of claims 1 to 3, wherein a resin reservoir is provided on a terminal side of the mold cavity to accommodate the resin that has expanded and expanded and leaked from the mold cavity. Molding method.   The injection foam molding method according to any one of claims 1 to 3, wherein a projecting core that can be taken in and out is provided in the mold cavity to accommodate a volume of the expanded resin. In an injection foam molding machine that molds a plurality of molded products by injecting and filling foamable molten resin into a mold unit by an injection unit,
A plurality of mold cavities of different shapes and sizes provided in the mold unit;
A plurality of resin passages respectively connected to the plurality of mold cavities;
A plurality of resin gate opening and closing means for opening and closing the resin passage,
An injection foam molding machine comprising: a control device that opens and closes each of the plurality of resin passages by the plurality of resin gate opening and closing means so as to sequentially inject and fill the mold cavity with foamable molten resin. The controller is
Control the injection speed according to the preset injection screw stroke and injection speed pattern,
After filling each cavity, release the resin pressure,
Reset the screw position after depressurization as the injection start position to the next cavity,
The injection foam molding machine according to claim 6, wherein the injection speed is controlled according to a preset injection screw stroke and injection speed pattern. A plurality of resin reservoirs respectively connected to the plurality of mold cavity end sides;
The injection foam molding machine according to claim 6 or 7, further comprising a plurality of heating means respectively provided in a path from the plurality of mold cavities to the plurality of resin reservoirs. A plurality of projecting cores provided so as to be able to enter and exit from the plurality of mold cavities,
The injection foam molding machine according to claim 6 or 7, further comprising a hydraulic circuit that controls the operations of the plurality of protruding cores. The hydraulic circuit for controlling the operation of the protruding core is:
Piping connected to a core cylinder chamber in which the plurality of protruding cores are housed;
A plurality of compression springs for urging each of the plurality of protruding cores toward the mold cavity;
The injection foam molding machine according to claim 9, further comprising a plurality of flow rate adjusting valves respectively interposed in the plurality of pipes.

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