JPH0464292B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a vent-type injection control method in which volatile matter and moisture contained in molten resin are removed before injection.

If the resin itself contains volatile matter or moisture during the injection process, these gaseous substances will be trapped between the resin surface and the cavity surface while filling the cavity with molten resin, causing molding defects such as silver streaks and gas discoloration. It was causing it to happen. Therefore, one method is to perform preliminary drying outside the injection molding machine, but this is expensive, and therefore a vent type injection molding machine has been proposed to remove these gaseous substances inside the injection molding machine.

[Prior Art] An example of a conventional vent type injection molding machine will be described with reference to FIG. A screw 12 that can move forward and backward and rotate is inserted into the heating cylinder 11, and a vent port 13 is provided in the middle of the screw 12, from which volatile matter and moisture are released into the atmosphere or sucked in by a vacuum pump (not shown). Was. In this case vent port 1
If the resin pressure in step 3 is not sufficiently lowered, the resin will overflow here and close the vent port 13, making it impossible to function. Therefore, as shown in FIG. It was divided into 2 parts: 12B and 12B. It was also 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 overall length of the screw 12 has to be long, which increases the cost and places great restrictions on the screw design. Because of the screw diameter that maintains the vent port 13 at a low pressure as described above, the resin tends to stay in the vent port 13, causing residual burns and failure to replace the resin when replacing the resin. Further, it is necessary to provide a feeder (not shown) to regulate the amount of resin supplied to the heating cylinder 11, which limits the plasticizing ability and increases cost.

[Purpose of the Invention] The present invention eliminates these drawbacks, and its purpose is to provide a vent port in the nozzle of a conventional non-vent type injection molding machine, thereby reducing the amount of molten resin in the raw material at a low cost. An object of the present invention is to provide a vent type injection control method that makes it possible to suck volatile matter and moisture to the outside.

[Summary of the Invention] In the vent-type injection control method of the present invention, a nozzle having a vent port that can be opened and closed is arranged at the tip of a heating cylinder that is controlled to an arbitrary temperature, and can rotate and move back and forth inside the heating cylinder. In an in-line screw type injection molding machine with a screw inserted, the vent port is opened to the atmosphere and the screw is retracted without rotating at an arbitrarily determined operation timing after measuring the resin. ing.

[Embodiment of the Invention] Hereinafter, FIG. 1 showing an embodiment of the present invention will be described. A screw 32 that rotates and moves back and forth is inserted into the heating cylinder 31, which is controlled to a desired temperature by a heater (not shown).On the right side of the heating cylinder 31 is a hopper 14 (not shown) (see FIG. 3). ) is attached, but the intermediate vent port 13 is not provided. An A nozzle 33 is fixed to the tip (left end) of the heating tube 31 by screwing, and a housing 34 is screwed to the outer periphery of the A nozzle 33 so as to be fixed directly to the heating tube 31. Good too. Inside the housing 34, a B nozzle 36, which is constantly pressed forward by a spring 35, is slidably inserted coaxially with the A nozzle 33. The vent port 37 provided in the housing 34 is designed so that most of it does not come into contact with the B nozzle 36 when it is in the forward position as shown, that is, by the gap between the open mating surfaces of the A nozzle 33 and the B nozzle 36. It is arranged so as to communicate with the inside of the heating cylinder 31. Note that 38 is a fixed mold, 39 is a movable mold, and 40 is a cavity.

Next, the operation of the embodiment described above will be explained. 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. By rotating the screw 32 in this state, the measuring process begins and both molds 38, 39 and the molded product (not shown) are cooled. When the measurement is completed, the screw 32 stops rotating and retreats without rotating over a distance larger than normal back-back, but just before that, the heating cylinder 31 is moved so that the B nozzle 36 does not leave the fixed mold 38 and the AB nozzles 33, 36 Move back until it is far enough away. Note that the screw 32 and the heating cylinder 31 may be retracted at the same time.

In this manner, after the screw 32 reaches the retraction limit without rotating, the heating cylinder 31 is further retracted, so that the B nozzle 36 is completely separated from the fixed mold 38. At this time, the vent port 37 is open to the atmosphere, and after the screw 32 non-rotates and retreats, the air from the vent port 37 flows into the A nozzle 3.
Since the molten resin flows to the left side of the heating cylinder 31 through the small diameter flow path No. 3, the molten resin is drawn to the right and reaches the position shown as A in FIG. As a result, no molten resin remains in the small diameter channel of the A nozzle 33, and a space communicating with the vent port 37 is formed on the left side of the molten resin A.

At this point, both molds 38, 39, etc. have finished cooling, so after moving the movable mold 39 backward, a molded product (not shown) is taken out, and then the movable mold 39 is moved forward. After the molds 38 and 39 are clamped, the heating cylinder 31 is moved forward to touch the B nozzle 36 to the fixed mold 38, and from this moment the vent port 37 is connected to a vacuum source (not shown), thereby causing the above-mentioned melting. Moisture and volatile matter that have separated from the molten resin and become gaseous, floating in the space formed to the left of the resin A, are evacuated. At this time, the vent port 37 may be opened to the atmosphere without being connected to a vacuum source, although the effect is reduced.

After the evacuation is completed, the heating cylinder 31 is further advanced to bring both nozzles 33 and 36 into close contact with each other, and an injection process begins. During this injection process, the space inside the heating cylinder 31 is in a vacuum state, so it does not become an obstacle to molding, and good molding is possible without any discoloration due to adiabatic compression during filling with the molten resin.

In the above explanation, both molds 38 and 3 are evacuated.
After the mold clamping in step 9, the B nozzle 36 was touched to the fixed mold 38, but after the measurement was completed, the screw 3
2 is moved back without rotating and the B nozzle 36 is fixed to the mold 3.
This may be done within the time it takes to release the nozzle from 8 and touch the nozzle again. In this case, evacuation may be performed using a timer (not shown) or may be performed in accordance with the operation timing.

FIG. 2 shows the main part of another embodiment of the present invention, and this embodiment differs from the first embodiment in FIG. 1 only in the approach and separation of the B nozzle. A housing 51 is screwed onto the A nozzle 33 fixed to the tip of the heating cylinder 31, but it may be fixed directly to the heating cylinder 31. A B nozzle 52 is slidably inserted into the small diameter portion of the housing 51.
2 is the same as the first embodiment in that when the heating cylinder 31 moves forward, it touches a fixed mold (not shown). Arm 52A extending vertically in the diagram of B nozzle 52
is fixed to the piston rod 54 of a pair of cylinders 53 fixed to the tips of the heating cylinder 31, so that the B nozzle 52 can be moved to the forward position shown in the figure and the switching valve 56 that controls the pressure fluid of the pressure source 55 to the cylinder 53. It has two positions: a retracted position when switching to the right ventricle. Further, a vent port 37 is provided in the large diameter portion of the housing 51, and its function and effect are the same as in the first embodiment.

The operation of this embodiment differs from the first embodiment only in that the switching valve 56 is in the right ventricle when the nozzles 33, 52 are in close contact with each other in the backward movement, whereas it is in the left ventricle in the forward movement when the nozzles 33, 52 are separated. Therefore, detailed explanation will be omitted.

[Effects of the Invention] As explained above, the vent-type injection control method of the present invention is capable of molding highly hygroscopic resin with a standard non-vent injection molding machine without pre-drying by providing a vent port in the nozzle part. become. Furthermore, since the screw can be short, it has the advantage that a low-cost vent type injection molding machine can be constructed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, FIG. 2 is a sectional view of a main part of another embodiment, and FIG. 3 is a sectional view of a conventional example. 31... Heating tube, 32... Screw, 33... A nozzle, 34, 51... Housing, 36, 52... B
Nozzle, 37...vent port, 38, 39...mold.

Claims (1)

[Claims] 1. An in-line screwdriver in which a nozzle with an open and a closable vent port is arranged at the tip of a heating cylinder that is controlled to an arbitrary temperature, and a screw that can rotate and move forward and backward is inserted into the inside of the heating cylinder. A vent-type injection control method in a U-type injection molding machine, in which the vent port is opened to the atmosphere at an arbitrarily determined operation timing after resin is measured, and the screw is retreated without rotating. 2. The vent-type injection control method according to claim 1, wherein the vent port is closed at least during injection. 3. The vent-type injection control method according to claim 1, wherein opening and closing of the vent port is operated by pressure fluid. 4. Claim 1, characterized in that the vent port is opened by elastic force and closed by pressing the nozzle against the mold with a desired force.
Vent-type injection control method described in section. 5. Claim 1, characterized in that the vent port is open to the atmosphere in an open state.
The vent type injection control method according to items 1 to 4. 6. Claim 1, wherein the vent port is connected to a vacuum source in the open state.
The vent type injection control method according to items 1 to 4. 7. Connect the vent port to the vacuum source at the same time as touching the nozzle to the mold, or after completing measurement, retract the screw without rotating and separate the nozzle from the mold, otherwise connect the vent port to the atmosphere. A vent type injection control method according to any one of claims 1 to 6, characterized in that the vent is open. 8. After measurement is completed, the screw is retracted without rotating, the nozzle is separated from the mold, and then the vent port is connected to a vacuum source according to an arbitrarily determined operation timing, and the rest is open to the atmosphere. A vent type injection control method according to any one of claims 1 to 6, characterized in that: