JPH05169492A - Combined injection molding method - Google Patents

Abstract

PURPOSE:To offer a combined infection molding method by which on infection- molded part with a high market value can be produced without a hesitation mark on a skin layer of the molded part. CONSTITUTION:In a combined injection molding method wherein a core molding material (J2) is injected after a skin layer material (J1) is injected, the skin layer material (J1) is continuously injected during the whole injection process (t0 I8) and the core molding material (J2) is infected parallel for a specified period (t3 t6) on the course of the whole process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite injection molding method of filling a skin layer forming material and then a core layer forming material.

[0002]

2. Description of the Related Art In a composite injection molding method, a molding material for forming a skin layer is first filled in a mold, then a material for forming a core layer is filled, and finally, a small amount of a material for forming a skin layer is filled. A sandwich molding process has been used. This method is specifically carried out using an injection molding machine schematically shown in FIG. This injection molding machine (H) includes an extrusion device (Ts) for the skin layer forming material (S) and an extrusion device (Tk) for the core layer forming material (K), and each nozzle of these extrusion devices ( It has a switching part (E) for switching and connecting Ns) (Nk) to the mold (M).

In order to perform the above-mentioned sandwich molding process using such an injection molding machine (H), it is usually operated as shown in FIGS. 5 to 7 according to the filling program shown in FIG. That is, in the above program, in the unit cycle time (t ₀ → tc), the skin layer forming material (S) is filled in a predetermined amount for the first fixed time (t ₀ → ta) (FIG. 5), and then the extruder ( Stop the operation of (Ts) and use the switching section (E) to make the nozzle (Nk)
After switching and connecting to the mold, a certain amount of core layer forming material (K) was charged from the extruder (Tk) for the next fixed time (ta → tb) (Fig. 6), and again by the switching unit (E). The nozzle (Ns) is switched and connected to the mold, and the skin layer forming material (S) is extruded by the extruder (Ts) for a certain period of time (tb → tc) and a small amount is filled in the gate part (Fig. 7), and the injection unit cycle Has been activated to complete.

However, in the above operation program, the first skin layer forming material filling operation at time t ₀ → ta and the second skin layer forming material filling operation at time tb → tc are continuously performed. No, also skin layer forming material
There is a time lag between the (S) filling process and the core layer forming material (K) filling process, and as a result, hesitation marks are generated in the outer skin layer of the injection-molded product obtained, which leads to a commercial value. There is a problem of going down.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite injection molding method capable of producing an injection-molded article having a high commercial value without producing hesitation marks on the skin layer surface of the molded article. ..

[0006]

Thus, according to the invention of "Claim 1" of the present application, "composite injection molding for performing injection filling of" skin layer forming material (J1) after injection filling of core layer forming material (J2) " In the method, the injection and filling of the skin layer forming material (J1) is continuously performed throughout the entire injection filling process (t ₀ → t ₈ ), and the core layer is formed at a certain time (t ₃ → t ₆ ) in the middle of the entire filling process. Forming material
A composite injection molding method, characterized in that injection filling of (J2) is performed in parallel.

According to the method of the present invention, there is no intermediate stop in the filling operation of the skin layer forming material (J1), and the skin layer forming material (J1)
There is no time lag between the filling of the core layer forming material (J2) and the filling of the core layer forming material (J2), and the skin layer molding material (J1) is first filled in a mold to form the first skin layer, and then the core layer is formed. Fill the specified amount of forming material (J2), and finally, skin layer forming material
It can be suitably used for a so-called conventional sandwich molding process in which a small amount of (J2) is filled to form the second skin layer.

In the method of the present invention, the injection filling amount is preferably adjusted to a constant amount during the entire injection filling process. Therefore, when the filling operation of the skin layer forming material (J1) and the filling operation of the core layer forming material (J2) are performed in parallel, the filling amount of the skin layer forming material (J1) is necessarily decreased and both The sum of the filling amounts is adjusted to be the total filling amount. In this case, as shown in "Claim 2", "core layer forming material (J2)"
The injection filling amount of the skin layer forming material (J1) decreases at the same time when the injection filling of the skin layer forming material (J1) is started, and the injection filling amount of the core layer forming material (J2) is larger than the injection filling amount of the skin layer forming material (J1) after a predetermined time. Therefore, it is preferable that the injection filling of the core layer forming material (J2) is completed and the injection filling amount of the skin layer forming material (J1) is restored after a certain time has elapsed.

To achieve the method of the present invention, the skin layer forming material (J1) filling device and the core layer forming material (J2) filling device are connected to a mold independently of each other, or these fillings are performed. It is preferable to use an injection molding apparatus having a configuration in which the apparatus is connected to a mold through one confluence section, the extrusion amount in each filling apparatus is set, and the mixture is extruded and then supplied from the confluence section.

[0010]

According to the invention of "Claim 1" of the present application, the filling operation of the skin layer forming material (J1) is continued throughout the entire injection filling process (t ₀ → t ₈ ). Since it is formed by the skin layer which is fluidized and filled without any intermediate stop, hesitation marks and the like do not occur on the surface of the molded product.

Further, according to the invention of "Claim 2" of the present application, when the injection filling of the core layer forming material (J2) is performed in parallel, the filling amount of the core layer forming material (J2) becomes the main, but during this period, Since the filling operation of the skin layer forming material (J1) continues,
The surface of the molded product is formed by the skin layer which is filled with an intended amount of the core layer forming material (J2) and is fluidized through the entire process of injection filling (t ₀ → t ₈ ).

[0012]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Example 1 FIG. 1 is a plan view of an example of a compound injection molding machine for carrying out the method of the present invention. The compound injection molding machine (A) in the figure has a resin injection device (B) installed in the center, and a first heating cylinder (C) and a second heating cylinder (D) installed in parallel on both sides of the resin injection device. Cage,
The first and second heating cylinders (C) and (D) are connected to the resin injection device (B) by first and second connection cylinders (28) and (29) provided at the tips thereof. The structures of the first and second heating cylinders (C) and (D) are known structures, and the resin pellets supplied from the first and second hoppers (15) and (16) are the internal kneading screws (17). It is heated and kneaded by the rotation of (18) and gradually pushed forward.

The resin injection device (B) is fixed on a support base (not shown), and the support base is slidably supported by guide rails (not shown). Support base is center axis (21)
Is connected to the main drive cylinder (22) via the main drive cylinder (22) and the resin injection device (B) and both heating cylinders (C)
The whole of (D) moves back and forth, and the outer cylinder of the resin injection device (B)
The tip of (1) comes into contact with and separates from the sprue bush (23) of the mold (4). (24) is a fixed fulcrum that fixes the rear part of the main drive cylinder.

The first and second heating cylinders (C) and (D) are provided with a center shaft (21).
It is adapted to slide together with the resin injection device (B) along side shafts (25) arranged in parallel on both sides of the.
(26) is a slider provided on the main body portion (C1) (D1) of the first and second heating cylinders (C) (D) connected to the first and second heating cylinders (C) (D), (27) is a support side stand that supports the side shaft (25). (15) and (16) are hoppers for supplying the raw material pellets, and the main body portion (C1) (D) connected to the first and second heating cylinders (C) (D)
Each is provided in 1). (C2) and (D2) are motors for rotating the kneading screws (17) and (18).

FIG. 2 is a resin injection device with a built-in cylinder portion.
It is a schematic sectional drawing of (B). Main structure is outer cylinder (1), inner cylinder
(2) and needle (3), inner cylinder drive cylinder (B1) that moves the inner cylinder (2) forward and backward, and needle that moves together with the inner cylinder (2) and moves the needle (3) forward and backward Drive cylinder
(B2), position detecting device (40a) for detecting the position of the needle (3), position detecting device (40b) for detecting the position of the inner cylinder body (2), CPU (41), for the inner cylinder The inner cylinder proportional valve (42) controls the drive cylinder (B1), and the needle proportional valve (43) controls the needle drive cylinder (B2). It goes without saying that the proportional valves (42) (43) may be servo valves.

The first half of the outer cylinder (1) is the kneaded first resin (J
It is a first resin filling injection part for filling 1), and the latter half is an operating part and is an outer cylinder part (8).
The first resin passage (6), which is the first resin filling / injecting portion, is composed of the inner circumference of the outer cylinder (1) and the outer circumference of the inner cylinder (2).
Further, an outer cylinder nozzle hole (5) connected to the mold (4) is bored at the tip of the outer cylinder (1), and the forward inner cylinder ( The outer peripheral surface of the front end of 2) is in contact with the first
A first resin seal portion (7) for closing the resin passage (6) is formed. The first connecting tube (28) connected to the outer tube body (1) is
The tip portion of the first heating cylinder (C) is connected so as to communicate with the first resin passage (6).

The first half of the inner cylinder (2) is a kneaded second resin.
It is a second resin filling injection part for filling (J2), the latter half is the operating part, and the inner cylinder cylinder part (11) is on the inner periphery thereof.
Is formed, and the outer circumference is a piston part (10) for the outer cylinder, and is slidably arranged in the outer cylinder part (8). The second resin passage (1
2) is composed of the inner circumference of the inner cylinder (2) and the outer circumference of the needle (3). Furthermore, the outer cylinder nozzle hole (5) is provided at the tip of the inner cylinder (2).
The inner cylinder nozzle hole (9) is bored correspondingly to the front end outer peripheral surface of the advanced needle (3), and the second resin passage (12) is closed. A second resin seal part (13) is formed. The second connecting tube (29) connected to the outer tube body (1) has the tip of the second heating tube (D) connected to the second tube.
It is connected so as to communicate with the resin passage (12).

The first half portion of the needle (3) is a small-diameter resin-filled injection portion, and the second half portion is an operating portion, which serves as an inner cylinder piston portion (14) and serves as an inner cylinder body (2). Cylindrical cylinder part (1
It is slidably stored in 1). The tip of the first half of the needle (3) is the inner cylinder when the needle (3) advances.
The mold is inserted into the second resin seal portion (13) formed on the inner circumference of the tip of (2) to close the second resin passage (12) and at the same time the mold.
(4) It is possible to apply a holding pressure to the resin inside. That is, as shown in FIG. 3, there is a space (pf → p>) between the entrance portion of the second resin seal portion (13) and the tip insertion portion (30) of the needle (3).
The second resin seal part (13) is closed at the point where both of them coincide with each other by advancing from the state where only pe) is opened, and by further advancing by (pe → pd), the die (4) is inserted by the insertion allowance. It is possible to apply a strong holding pressure at a position close to the resin.

The position detecting device (40a) is mounted on the exposed rear end of the needle (3) and moves together with the needle (3) and is used for detecting the position of the needle (3). , Potentiometers and encoders are used. Similarly, the position detecting device (40b) is mounted on the exposed rear end portion of the inner cylindrical body (2), moves with the inner cylindrical body (2), and is used for detecting the position of the inner cylindrical body (2).

The CPU (41) receives a signal from the position detecting devices (40a) (40b) and controls the inner cylinder cylinder part (B1) and the needle cylinder part (B2). (43) or feedback control of the servo valve. Now C
The PU (41) controls the positions of the inner cylinder (2) and the needle (3) in the unit cycle time (t ₀ → t ₈ ) as shown in FIG. Fig. 4 shows the injection speed (V ₁ ) and the injection speed (V ₂ ) of the second resin.
It is set to control according to the program shown in. That is, the relationship between the position (P) of the tip of the inner cylinder (2) with respect to the outer cylinder (1) at each time (t) is t ₀ = Pa, t ₀ → t ₂
= Pa → Pc, t ₂ → t ₃ = Pc → Pb, t ₃ → t ₆ = Pb, t ₆ → t ₇ = Pb →
Pc, t ₇ → t ₈ = Pc, while the relationship between the position (p) of the tip of the needle (3) with respect to the inner cylinder (2) at each time (t) is t ₀ → t ₂ = pe, t ₂ → t ₄ = pe → pf, t ₄ → t ₅ = pf, t ₅ → t ₆
= Pf → pe, t ₆ → t ₈ = pe.

With the above configuration and settings, the first resin (J
1) will be described as a skin layer forming resin pellet, and the second resin (J2) as a core layer forming resin pellet. First, the resin pellets of the first and second resins (J1) and (J2) are put into the first and second hoppers (15).
Put into (16), operate the motors (C2) (D2) to rotate the kneading screws (17) (18) and at the same time, the first and second heating cylinders (C)
The resin pellets (J1) and (J2) are kneaded while being heated and melted by the heaters (H1) and (H2) wound around the outer periphery of (D), and sequentially fed forward.

The first and second resins (J1) and (J2) sufficiently kneaded in the first and second heating cylinders (C) and (D) are the first and second connecting cylinders (28) and (2).
9) through the first and second resin passages (6) of the resin injection device (B)
They are sent to (12) respectively.

Before the start of molding, the inner cylinder piston portion (1
4) is operated to move the needle (3) forward so that the tip of the needle (3) is located at the predetermined position (pe) of the inner cylindrical body (2) and the second resin seal portion (1
3) is closed so that the second resin (J2) does not leak from the inner cylinder nozzle hole (9) at the tip of the inner cylinder (2). On the other hand, the tip of the inner tubular body (2) is retracted to a predetermined position (Pc) of the outer tubular body (1) to open the first resin seal portion (7). The first heating cylinder in this state
When the screw (17) of (C) is operated, the first resin (J1) that has been kneaded gradually accumulates at the tip portion, and the screw (17) retracts in accordance with this. A predetermined amount of the first resin (J1) is accumulated by this operation, and the inner cylinder (2) is advanced to the predetermined position (Pa) again to close the outer cylinder (1). Next, the tip of the needle (3) is moved to the rear position (pf) to open the space between the tip insertion portion (30) of the needle (3) and the second resin sealing portion (13), and in this state, 2 Heating barrel (D) screw
(18) is activated and a predetermined amount of the second resin (J2) is stored in the tip portion in the same manner, and then the needle (3) is moved to the front position.
The second resin seal portion (13) is closed by advancing to (pe).

At the start of molding (time t ₀ ), the inner cylindrical body
When the tip of (2) is moved backward toward the open position (Pc) of the outer cylinder (1) and the screw (17) is moved forward, the kneading first resin (J1) stored at the tip is pushed out. .. The extruded kneading first resin (J1) enters the first resin passage (6) through the first connecting cylinder (28), and passes through the open first resin seal portion (7) to form the outer cylinder body. From the outer cylinder nozzle hole (5) at the tip of (1) to the mold (4)
Injection is started inside. The injection speed of the first resin becomes the maximum injection speed (V ₁ c) at the time (t ₁ ) when the tip of the inner cylindrical body (2) reaches the open position (Pc), and the maximum injection speed is the time (t ₂ ) Is maintained.

At time (t ₂ ), the inner cylindrical body (2) is moved forward, the needle (3) is moved backward, and at the same time, the screw (18) is moved forward, and the second kneading resin (J
2) Push out. By the above operation, the injection amount of the first resin (J1) is reduced and at the same time the injection speed (V ₁ ) is also reduced.
Time at which the tip of the inner cylinder (2) reaches the middle position (Pb) of the outer cylinder (1)
At (t ₃ ), the forward movement of the inner cylinder (2) is stopped, at which time the injection speed becomes low (V ₁ b), and this injection speed (V ₁ b) is maintained until time (t ₅ ). On the other hand, the second resin (J2) passes through the opened second resin seal portion (13) and the inner cylinder nozzle hole (9) of the inner cylinder (2),
Injection is started into the mold (4) through the outer cylinder nozzle hole (5) at the tip of the outer cylinder (1). The injection speed (V ₂ ) of this second resin becomes maximum (V ₂ f) at the time (t ₄ ) when the tip of the needle (3) retracts to the rear position (pf) of the inner cylindrical body (2), and the time Since the tip of the needle (3) is held at this position (pf) until (t ₅ ), the maximum injection speed (V ₂ f) is maintained until time (t ₅ ). Time (t ₅ )
At the same time, the needle (3) is advanced and the injection amount of the second resin (J2) is reduced, and at the same time, its injection speed (V ₂ ) is also reduced, and the tip of the needle (3) is ) Forward position (pe)
The inner cylinder (2) is closed at the time (t ₆ ) when the second resin (J2)
Injection is stopped.

At time (t ₆ ), the inner cylinder (2) is replaced by the outer cylinder (1).
To the rear position (Pc), the injection amount of the first resin increased, the injection speed (V ₁ ) also increased, and the tip of the inner cylindrical body (2) stopped at the rear position (Pc). It becomes maximum (V ₁ c) at time (t ₇ ). This maximum injection speed (V ₁ c) is maintained until time (t ₈ ). At the above time (t ₈ ), the injection unit cycle ends.

By the above operation, the injection of the first resin (J1) forming the skin layer is continued from the start of injection (t ₀ ) to the end of injection (t ₈ ). Since the second resin (J2) is injection-filled by being surrounded by the constantly flowing first resin (J1), the injection filling of the second resin (J2) does not affect the surface layer of the molded product. Therefore, the properties of the surface layer of the molded product will be determined by the filling speed of the first resin (J1), but this first resin (J1) will continue to be filled throughout the unit cycle. No hesitation marks or the like will be generated on the surface layer of.

After the above time (t ₈ ), the inner cylindrical body (2) is moved forward so that its tip is located at the forward position (Pa) to close the first resin seal portion (7) and (3) is advanced so that its tip is located at the front position (pe), and the second resin seal portion (1
If the needle (3) is further advanced and the tip is located at the inward position (pd) while the 3) is closed, a strong pressure will be applied to the filling resin in the mold (holding process). .. As a result, it is a skin-core type molded product in which the second resin (J2) is surrounded by the first resin (J1) on the outer periphery, and the molded product has sufficiently high density and contracts and is taken out during cooling. There is almost no post-shrinkage, and a molded product having a shape extremely faithful to the cavity shape can be obtained.

[0029]

According to the present invention, since the injection of the skin layer forming material is continuously continued throughout the unit cycle of injection molding, even if the injection of the core layer forming material is intermittently introduced during that period, the influence thereof is exerted. A hesitation mark or the like does not occur on the surface of the molded product due to the skin layer that does not receive and flows without retention. This makes it possible to manufacture an injection-molded article having high commercial value.

[Brief description of drawings]

FIG. 1 is a plan view of an example of a compound injection molding machine that carries out the method of the present invention.

2 is a schematic cross-sectional outline view of a resin injection device with a built-in cylinder portion of the molding machine of FIG.

FIG. 3 is an enlarged view of a main part for explaining a positional relationship between an outer cylinder body, an inner cylinder body and a needle of the injection device of FIG.

FIG. 4 is a program diagram of an example of injection control in a unit cycle.

FIG. 5 is a schematic diagram illustrating an injection operation by a conventional injection molding machine.

FIG. 6 is a schematic diagram illustrating an injection operation by a conventional injection molding machine.

FIG. 7 is a schematic diagram illustrating an injection operation by a conventional injection molding machine.

FIG. 8 is a program diagram of an example of injection control in a unit cycle of a conventional injection molding machine.

[Explanation of symbols]

(1) ... Outer cylinder (2) ... Inner cylinder (3) ... Needle (4) ... Mold (5) ... Outer cylinder nozzle hole (6) ... First resin passage (7) ... First resin seal Part (9) ... Inner cylinder nozzle hole (12) ... Second resin passage (13) ... Second resin seal part (40a) ... Needle position detection device (40b) ... Inner cylinder position detection device (41) ... CPU (42)… Proportional valve for inner cylinder (43)… Proportional valve for needle (A)… Composite injection molding machine (B)… Resin injection device (C)… First heating cylinder (D)… Second heating cylinder

Claims (2)

[Claims] 1. A composite injection molding method comprising injection-filling a core-layer forming material after injection-filling a skin-layer forming material, wherein injection-filling of the skin-layer forming material is continuously performed throughout the entire injection-filling process. A composite injection molding method characterized in that injection filling of a core layer forming material is performed in parallel during a certain time during the process. 2. The injection filling amount of the skin layer forming material decreases simultaneously with the start of the injection filling of the core layer forming material, and the injection filling amount of the core layer forming material is larger than the injection filling amount of the skin layer forming material after a predetermined time. 2. The composite injection molding method according to claim 1, wherein the injection filling of the core layer forming material is completed and the injection filling amount of the skin layer forming material is restored after the elapse of a certain time.