JPH0741654B2 - Vent type injection control method and vent type injection molding machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vent-type injection control for removing volatile components and water contained in a molten resin, and air existing in a mold cavity before injection. A method and a vented injection molding machine.

If the resin itself contains volatile components or water during the injection process, or if air is present in the mold, these gaseous substances will be trapped between the resin surface and the cavity surface while the molten resin is being filled into the cavity. Therefore, molding defects such as silver streak and gas burn are caused. Therefore, predrying outside the injection molding machine is also a method, but it is costly. Therefore, a vent type injection molding machine for removing these gaseous substances in the injection molding machine has been proposed.

[Prior art]

An example of a conventional vent type injection molding machine will be described with reference to FIG. Inside the heating cylinder 11, a screw 12 that can be moved back and forth and rotated
The vent port 13 is provided in the middle of the chamber to release volatile components and moisture into the atmosphere or to suck them by a vacuum pump (not shown). In this case, unless the resin pressure in the vent port 13 is sufficiently low, the resin overflows here and the vent port 13 is closed and the function becomes impossible. Therefore, as shown in FIG. Divided into 12A and 2nd stage section 12B. It was necessary to design the transfer capacity of the second stage section 12B to be sufficiently higher than the transfer capacity of the first stage section 12A.

For this reason, the total length of the screw 12 is inevitably long, which raises the cost and imposes great restrictions on the screw design. As described above, due to the screw dimension keeping the vent port 13 at a low pressure, the resin is apt to stay in the vent port 13 and causes a stagnation of the resin and defective resin replacement at the time of resin replacement.

Further, since it is impossible to remove the air existing in the cavity by such a conventional vent method, a vacuum mold forming apparatus may be used in some cases. In this device, the mold is provided with a vacuum suction section having a sufficient cross-sectional area to draw air, but it is necessary that the resin does not leak from the vacuum suction section when the resin is injected. However, the mold design is restricted.

FIG. 4 shows an example of the above-mentioned vacuum mold forming apparatus. The heating cylinder 11 is in contact with the fixed mold 22 through the nozzle 21 at the time of forward movement, and is provided with a movable mold 23 that faces the fixed mold 22 and moves forward and backward. A cover surrounding a space 24 (this space 24 becomes a cavity when both molds 22 and 23 are closed) formed on the facing surface before the moving mold 23 is advanced and the two molds 22 and 23 are completely closed.
25 is provided, and the movable die 23 is provided with a hole 26 as a vacuum suction portion. The hole 26 needs to have a sufficient cross-sectional area for high-speed vacuum suction, but it is not related to the cavity formed when both molds 22 and 23 are closed so as not to receive the resin pressure at the time of injection. It is provided on the outer parting surface. As shown in the figure, from the time when the space 24 is surrounded by the cover 25, vacuum suction is performed through the hole 26 to bring the space 24 into a vacuum state. However, there is a drawback in that a vacuum suction of a volume much larger than the actual cavity volume is required, the vacuum device becomes large in size, and a time for vacuum suction is required for a certain period of time before the final mold is closed, and the molding cycle becomes long. there were.

[Object of the Invention]

The present invention eliminates such drawbacks and its purpose is to
By providing a vent port in the nozzle part of a conventional non-vent type injection molding machine, it is possible to suck volatile components and water in the molten resin of raw materials and residual air in the cavity at a low cost while venting injection. To provide a molding machine.

[Main points of the invention]

According to the vent type injection control method of the present invention, a nozzle having a vent port capable of opening and closing is arranged at the tip of a heating cylinder controlled to an arbitrary temperature, and a screw capable of rotating and advancing and retracting is inserted inside the heating cylinder. The in-line screw type injection molding machine is characterized in that after measuring the resin, the screw is retracted in a non-rotating state with the vent port and the nozzle closed.

Example of Invention

Hereinafter, FIG. 1 showing an embodiment of the present invention will be described. A screw 32 that rotates and advances and retracts is inserted in a heating cylinder 31 whose temperature is controlled by a heater (not shown). A hopper 14 (not shown) is provided on the right side of the heating cylinder 31 in the drawing.
(See FIG. 3) is attached, but the vent port 13 in the middle is not provided. An A nozzle 33 is fixed to the tip (left end) of the heating cylinder 31 by screwing.
A housing 34 is screwed to the outer periphery of the heating cylinder 31, but this may be directly fixed to the heating cylinder 31. A B nozzle 36, which is constantly pressed forward by a spring 35, is slidably inserted into the housing 34 at the same axial position as the A nozzle 33. Vent port 37 on housing 34
Is so that the B nozzle 36 is not in contact with most of it when it is in the advanced position as shown, that is, the A nozzle is opened.
It is arranged so as to communicate with the interior of the cavity 40 and the heating cylinder 31 by the gap between the mating surfaces of the 33 and the B nozzle 36.
38 is a fixed mold, 39 is a moving mold, and 40 is a cavity.

Next, the operation of the above-described embodiment will be described. When the injection process is completed, the screw 32 is not rotating, the B nozzle 36 is in contact with the fixed mold 38, and both nozzles 33 and 36 are in close contact.
In this state, the screw 32 is rotated to enter the measuring step, and the molds 38 and 39 and the molded product (not shown) are cooled. When the metering is completed, the screw 32 stops rotating, and the screw cylinder 32 is retracted by a distance larger than a normal suck back without rotating, so that the inside of the heating cylinder 31 is in a vacuum state. At this time, as shown in FIG. It is stored on the screw 32 side leaving a space at the tip (left side) of the heating cylinder 31,
Volatile components and water contained in the molten resin are vaporized and separated. In this state, by moving the heating cylinder 31 backward (moving to the right), the B nozzle 36 is separated from the fixed mold 38, and both nozzles 33 and 36 are moved.
Also leave.

Since the cooling described above has been completed at this point, the moving mold
Move the mold 39 backward (to the left) and take out the molded product, then move the mold
39 is advanced and the mold is clamped. After that, the heating cylinder 31 is moved forward so that the B nozzle touches the fixed mold 38.
33 and 36 are separated, and this state is shown in FIG. Here, the inside of the heating cylinder 31 and the cavity 40 are evacuated by leaving the vent port 37 open to the atmosphere or connecting it to a vacuum source (not shown) to perform vacuuming. Subsequently, the heating cylinder 31 is advanced to bring the nozzles 33 and 36 into close contact with each other, thereby closing the vent port 37 and stopping the vacuum port when vacuuming is performed, and then the injection process is started. Thereafter, this operation is repeated to obtain a desired number of molded products.

As for the normal resin, as described above, the screw 32 is retracted immediately after the measurement is completed without being rotated, but it is sometimes preferable to retract the screw 32 after an arbitrary time depending on the type of resin.

FIG. 2 shows the essential parts of another embodiment of the present invention, and this embodiment differs from FIG. 1 which is the first embodiment only in the contact and separation of the B nozzle. A housing 51 is screwed to the A nozzle 33 fixed to the tip of the heating cylinder 31.
It may be fixed directly to 31. The B nozzle 52 is slidably inserted into the small diameter portion of the housing 51, and the B nozzle 52 touches a fixed mold (not shown) when the heating cylinder 31 advances, as in the first embodiment. Since the arm 52A extending vertically in the drawing of the B nozzle 52 is fixed to the piston rods 54 of the pair of cylinders 53 fixed to the tip of the heating cylinder 31, the B nozzle 52 is moved to the forward position shown in the drawing and the cylinder.
The switching valve 56 for controlling the pressure fluid of the pressure source 55 with respect to 53 has two positions, that is, a retracted position when switching to the right chamber. Further, a vent port 37 is provided in the large diameter portion of the housing 51, and the function and effect thereof are the same as those of the first embodiment.

The operation of this embodiment is different from that of the first embodiment only in that the switching valve 56 is the right chamber when the nozzles 33 and 52 are in close contact with each other and is retracted, and the switching valve 56 is the left chamber when the nozzles 33 and 52 are separated from each other and is in the forward direction. Therefore, detailed description is omitted.

〔The invention's effect〕

As described above, in the vent type injection molding machine of the present invention, by providing the vent port in the nozzle portion, it becomes possible to mold a highly hygroscopic resin with a standard non-vent injection molding machine without predrying. Furthermore, since the cavity air is sucked at the same time when the volatile components and water contained in the resin are removed, the present invention has many advantages such as vacuum die molding with a normal die. In addition to this, since the screw can be short, a low cost vent type injection device can be constructed, and since the cavities are in a vacuum state, there is an advantage that burning due to adiabatic compression does not occur during filling of the molten resin.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a sectional view of an essential part of another embodiment, and FIGS. 3 and 4 are sectional views of conventional examples having different shapes. 31 …… heating cylinder, 32 …… screw, 33 …… A nozzle, 34 ・
51 …… Housing, 36 ・ 52 …… B nozzle, 37 …… Vent port, 38 ・ 39 …… Mold

Claims (7)

[Claims] 1. An in-line screw injection in which a nozzle having a vent port capable of opening and closing is arranged at the tip of a heating cylinder controlled to an arbitrary temperature, and a screw capable of rotating and advancing and retracting is inserted inside the heating cylinder. In a molding machine, a vent-type injection control method in which, after measuring the resin, the screw is retracted in a non-rotating state with the vent port and the nozzle closed. 2. The vent-type injection control method according to claim 1, wherein the vent port is closed at least during the injection process. 3. An in-line screw type injection in which a nozzle having a vent port capable of opening and closing is arranged at the tip of a heating cylinder controlled to an arbitrary temperature, and a screw capable of rotating and advancing and retracting is inserted inside the heating cylinder. In the molding machine, an A nozzle fixed to the tip of the heating cylinder, a housing fixed to the A nozzle or the tip of the heating cylinder and covering the outer periphery of the A nozzle, and a housing coaxial with the A nozzle and the housing. B nozzle slidably inserted into the inside,
A vent-type injection molding machine, characterized in that a vent port provided in the housing is opened when the nozzle B is in the forward position. 4. The vent type injection molding machine according to claim 3, wherein the opening and the closing of the vent port are operated by a pressure fluid. 5. The vent port is always opened by elastic force and is closed by pressing the nozzle against the mold with a desired force.
The vent-type injection molding machine according to the item. 6. The vent type injection molding machine according to claim 3, wherein the vent port is open to the atmosphere in an open state. 7. The vent type injection molding machine according to claim 3, wherein the vent port is connected to a vacuum source in an open state.