JP2009039912A - Injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding method capable of reducing the dispersion of the quality of moldings and preventing the damage of a mold. <P>SOLUTION: The injection molding method has a clamping process (S10), a nozzle touch process (S20), a valve gate opening process (S30), an injection process (S40), a cooling process (S50), a process (S60) of melting and metering a resin material, a mold opening process (S70) and a molding ejecting process (S80). In the valve gate opening process (S30), an item of control of opening two or more valve gates 17 is executed. A controller 7 starts injection of a molten resin into the cavity of the mold, when an opening check proximity sensor 19 detects that all of the valve gates 17 have become opened and the controller receives signals of the detection from the sensor (S32 to S35). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection molding method in which a molten resin is caused to flow into a mold cavity using a plurality of valve gates.

As a conventional injection molding method, a screw for transferring the molten resin toward the mold, a plurality of valve gates for controlling the flow of the molten resin, a linear position sensor for detecting the position of the reciprocating screw, In an injection molding system equipped with a computer, a method is known in which a computer controls the opening and closing of a valve gate based on the position of a screw detected by a linear position sensor, and performs injection control of molten resin into a mold (for example, , See Patent Document 1).
Special Table 2000-515450

  However, the response of the driving means for driving the valve gate usually varies. For example, when a pneumatic or hydraulic pressure is used as a drive source, fluid pressure variation and flow rate variation are the cause, and sliding resistance of the drive mechanical parts of the valve gate is also a cause. In the conventional injection molding method, molten resin flows in sequentially from the gate to which the control signal to be opened is sent out of the plurality of valve gates. There will be a difference in the timing at which the molten resin actually flows after the control signal is transmitted.

  If the molten resin inflow timing is shifted in this way, the molten resin injected from each gate into the mold in the mold material filling process does not reach a predetermined amount, resulting in a defective molded product, or the mold. There is a problem that the pressure distribution in the inside becomes abnormal and the mold is damaged.

  Accordingly, an object of the present invention has been made in view of the above problems, and is to provide an injection molding method effective in reducing variation in quality of a molded product and preventing damage to a mold.

In order to achieve the above object, the following technical means are adopted. That is, the first invention related to the injection molding method is an injection molding method in which a molten resin used for an injection molded product is injected into a cavity in a mold (6) having a plurality of valve gates (17). ,
After confirming that all of the plurality of valve gates (17) are opened by the plurality of sensors (19) that detect that each of the plurality of valve gates (17) is open, The injection of the molten resin into the cavity of the mold (6) is started.

  According to the present invention, it is possible to confirm that a plurality of valve gates are in an open state and then start injection of molten resin into the cavity. It is possible to start the molten resin from the gate at the same time. Therefore, it is possible to obtain an injection molding method that is effective in reducing variations in the quality of the molded product and preventing damage to the mold.

  Further, as the plurality of sensors (19), it is preferable to use a proximity sensor (19) that detects that an object to be detected has approached without contact. According to the present invention, by using a non-contact type sensor instead of a mechanical switch, the detection object and the sensor are less deteriorated over time, and the service life can be extended.

  Moreover, it is preferable to employ | adopt as a proximity sensor (19) the system which is equipped with the coil which generate | occur | produces a high frequency magnetic field, and utilizes electromagnetic induction. According to the present invention, since the sensor response speed is fast and reliable detection can be expected even under adverse conditions such as oil scattering, the open state of the valve gate can be detected quickly and reliably.

  The mold (6) is a mold having a plurality of cavities and capable of taking a plurality of the same molded product, and at least one valve gate (17) is provided for each cavity of the mold (6). It is what has been. According to the present invention, it is possible to inject the plurality of molded products under the same conditions with respect to the cavities so that the influence does not occur even if a deviation occurs in the timing at which each valve gate starts to open. Providing stable quality molded products that can reduce the variation in quality due to the size of sink marks, weight differences, etc. for multiple molded products produced by one molding and molded products produced by each molding. Can do.

  The plurality of valve gates (17) are preferably driven by air pressure. According to the present invention, it is possible to provide an injection molding method that can sufficiently absorb the deviation of the opening timing of the valve gate due to pressure fluctuations caused by a pneumatic drive source. In particular, when driving air that is also used for other equipment in the factory, air pressure fluctuations and flow fluctuations are more likely to occur depending on the usage conditions of other equipment, and the fluctuation range may increase. A remarkable effect is obtained.

  In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means of embodiment mentioned later.

(First embodiment)
Below, 1st Embodiment is described using FIGS. 1-7. First, FIG. 1 is a front view partially showing a configuration of an injection molding system for carrying out the injection molding method of the present embodiment. FIG. 2 is a block diagram showing a configuration for controlling a plurality of valve gate opening / closing devices 8, 9, 10, and 11 used in the injection molding method of the present embodiment.

  As shown in FIGS. 1 and 2, the injection molding method shown in the present embodiment includes an injection molding apparatus 1, a valve gate type mold apparatus 6 attached to the injection molding apparatus 1, and a mold apparatus 6. And a control device 7 that controls the opening and closing of the valve gate opening and closing devices 8, 9, 10, and 11. The control device 7 may also be used as a device for controlling the operation of the injection molding device 1.

  The injection molding apparatus 1 is an apparatus that supplies resin in an injection molding system that performs the injection molding method of the present embodiment, and includes a hopper 3 that contains various resin materials used in injection molded products in a non-molten state. The hopper 3 and the heating cylinder 4 connected to the inside, the screw 5 provided in the heating cylinder 4, and the motor 2 that rotates the screw 5 are provided.

  The resin material is supplied to the hopper 3 as solid pellets and sent from the hopper 3 to the heating cylinder 4. The heating cylinder 4 has a function of plasticizing the resin material. A heating heater or the like is wound around the outside of the heating cylinder 4, and the resin material is heated so as to be in a molten state from the outside. The resin material is also heated by frictional heat generated from the shearing force generated by the rotation of the screw 5.

  The screw 5 reciprocates in the axial direction, and the pressure and flow rate set values of the hydraulic oil supplied to the injection cylinder are controlled by the control device 7 to advance when the injection conditions described later are satisfied. The injection of the molten resin into the cavity (cavity part) is started. The inside of the heating cylinder 4 provided with the screw 5 is connected to a cavity of a mold to which molten resin is supplied. When injection is started, the molten material is pushed from the inside of the heating cylinder 4 into a manifold in which a plurality of passages are formed by the movement of the screw 5, and passes through a plurality of valve gates provided in the mold apparatus 6. Flows into the cavity.

  The mold apparatus 6 includes a fixed mold that is used while being fixed to a fixed mold plate, and a movable mold that is used while being fixed to a movable mold plate. A plurality of cavities are provided on the opposing surfaces of the fixed mold and the movable mold. In the present embodiment, a method for simultaneously molding four injection-molded products by one mold clamping and mold opening will be described. In addition, this mold apparatus may be capable of taking four identical injection-molded products, or may be capable of simultaneously molding four types of injection-molded products.

  The fixed mold is provided with a main runner communicating from the outlet of the heating cylinder 4 of the injection molding device 1 to each cavity, and further, a first runner connecting the main runner and each cavity, Two runners, a third runner, and a fourth runner are provided.

  A first valve gate facing the cavity is provided at the tip of the first runner, and the first valve gate is opened and closed by a first valve gate opening / closing device 8. A second valve gate facing the cavity is provided at the tip of the second runner, and the second valve gate is opened and closed by a second valve gate opening / closing device 9. A third valve gate facing the cavity is provided at the tip of the third runner, and the third valve gate is opened and closed by the third valve gate opening / closing device 10. A fourth valve gate facing the cavity is provided at the tip of the fourth runner, and the fourth valve gate is opened and closed by the fourth valve gate opening / closing device 11.

  Each valve gate opening / closing device 8, 9, 10, 11 is a system in which the driving valve 14 is driven by air pressure or hydraulic pressure, and the control device 7 is supplied to each valve gate opening / closing device 8-11 by a hose 12. The timing of opening and closing and the opening area are controlled by controlling the air pressure or hydraulic pressure. The valve gate opening / closing devices 8, 9, 10, and 11 may be driven by an electric motor.

  The position of the drive valve 14 is different between when the valve gate is closed and when the valve gate is opened, and the open position and the closed position can be detected by sensors. FIG. 3A is a schematic diagram showing a state in which the valve gate is closed, and FIG. 3B is a schematic diagram showing a state in which the valve gate is open.

  As shown in FIG. 3A, when the valve gate 17 is closed, the pin 15 that reciprocates in the axial direction of the nozzle 16 integrally with the drive valve 14 is a passage formed at the tip of the nozzle 16. It is in a position to block. The position of the drive valve 14 at this time is detected by the close confirmation proximity sensor 18, and the information is input to the control device 7 through the communication line 13.

  On the other hand, when the valve gate 17 is open, the pin 15 is located away from the tip of the nozzle 16 so as to open the passage formed at the tip of the nozzle 16. The position of the drive valve 14 at this time is detected by the proximity sensor 19 for opening confirmation, and the information is input to the control device 7 via the communication line 13. Note that communication between both proximity sensors and the control device 7 may be performed wirelessly. Both proximity sensors 18 and 19 are provided outside the device in order to detect the position of the drive valve 14 for each of the valve gate opening / closing devices 8 to 11.

  In this injection molding system, it is detected that the valve gate 17 is in the open state and the closed state, respectively, and is input to the control device 7, and this information is utilized in the execution of the injection molding process. In particular, it is necessary to ensure the accuracy of the detection because the detection that the valve gate 17 is in an open state is utilized at the timing of injecting the molten resin into the cavity.

  For this reason, in this embodiment, a proximity sensor that can detect without contact that the object to be detected has approached is used. As a result, compared with a mechanical switch using a limit switch, a micro switch or the like, the sensing object (driving valve 14) does not come into contact with the sensing object (driving valve 14) or sensor, and the deterioration over time of the sensing object (driving valve 14) or sensor is slow. There is an advantage that it will last a lifetime.

  As this non-contact proximity sensor, a high frequency oscillation method using electromagnetic induction, a magnetic method using a magnet, a capacitance method using a change in capacitance, or the like can be adopted. In the present embodiment, among these, a detection coil that generates a high-frequency magnetic field is used to employ electromagnetic induction.

  This high-frequency oscillation method utilizes the fact that a detection coil generates a high-frequency magnetic field, and when a drive valve 14 that is a detection object approaches this magnetic field, an induced current flows through the detection object (drive valve 14) by electromagnetic induction. When the impedance of the detection coil changes due to the induced current and the oscillation stops, information that the detection object is recognized as being in the open position or the closed position is input to the control device 7. With this method, the response speed of the sensor is fast, and rapid and highly accurate detection can be performed even under adverse conditions such as oil scattering. Further, since the sensor head portion can be made small, it has excellent mountability and is useful when a plurality of sensors are installed.

  Next, an injection molding process using the present injection molding system will be described with reference to FIGS. FIG. 4 is a flowchart showing the flow of the injection molding process of this embodiment. FIG. 5 is a flowchart showing the procedure of the valve gate opening step (S30) in FIG.

  As shown in FIG. 4, the injection molding process is performed in the order of the mold clamping process (S10), nozzle touch process (S20), valve gate opening process (S30), injection process (S40), cooling process (S50), Resin material melting and metering step (S60), mold opening step (S70), and molded product protruding step (S80). The process returns to S10 again and is repeated automatically and continuously in cooperation with each other. A large amount of molded products can be manufactured.

  First, in the mold clamping process of S10, the fixed mold and the moving mold are closed with a strong force by a toggle device or the like, and the female mold and the male mold are closed, and a mold that can withstand high pressure during injection molding. Perform closing. Next, in the nozzle touch step of S20, the step of bringing the outlet of the heating cylinder 4 into contact with the nozzle touch portion which is the resin injection port of the mold in order to inject the molten resin into the clamped mold. To implement. This nozzle touch process may be performed once at the start of the molding operation, and this process is skipped during the subsequent continuous automatic molding.

  In the valve gate opening step (S30), which is one of the features of the next embodiment, the valve gate opening / closing devices 8 to 11 are driven so that the valve gates provided in the cavities are opened, and the mold This is a step of confirming that all valve gates of the device 6 are opened. The procedure of step S30 will be described with reference to FIG.

  When the valve gate opening process of S30 is started, a command to open each valve gate is issued from the control device 7 (S31). Specifically, air of a predetermined air pressure is sent from the control device 7 to the valve gate opening / closing devices 8 to 11 through the hose 12 so that the drive valve 14 is in the open position, and the drive valve 14 is shown in FIG. Move to the open position shown. As the drive valve 14 moves, the pin 15 moves away from the tip of the nozzle 16 so that the passage of the nozzle 16 at the tip is opened and the valve gate 17 is opened.

  However, each of the valve gate opening / closing devices 8 to 11 does not have the same condition for the supplied air for all the hoses 12. For example, the air pressure does not become the same pressure in all the hoses, or the flow rate fluctuation or the pressure fluctuation occurs. Sometimes. Due to such a phenomenon, the opening start timing of all the valve gates is shifted or the opening completion timing is shifted. That is, even if an opening command is issued simultaneously from the control device 7, the opening timing of the valve gate and the opening end timing are different for each valve gate and are not the same. Also, these timings differ from shot to shot and are not necessarily in a certain order.

  In this case, if pressure is applied to the heating cylinder 4 by the advance of the screw 5 and the molten resin is sent to the tip of the nozzle 16 before the step of S30, the valve gate that has begun to open first is used as a starting point. The molten resin flows in and injection is started, and the molten resin flows into the valve gate that is opened thereafter. In such a situation, a large amount of resin flows into the cavity from the previously opened valve gate, and a large amount of resin does not flow into the cavity from the valve gate that starts to open slowly.

  And in the metal mold | die which takes many same molded articles, the product with a weight difference arises or the product from which the condition of sink marks differs arises. Further, even in a mold for molding different types of molded products at a time, the opening timing of the valve gate is not always the same for each shot, resulting in products with variations in quality from shot to shot.

  In addition, even in a mold having a plurality of valve gates for one cavity, the amount and flow of the resin flowing into each valve gate is not constant, and the resin does not flow constantly from shot to shot. The sink mark may exceed the predicted range, or products may vary from shot to shot.

  When the resin material is insufficiently filled as described above, the resin material is cooled and solidified without being filled with a necessary resin in the mold, and a phenomenon that the surface of the molded product is rough or part thereof is lost occurs. Further, when the above phenomenon becomes significant, a resin single flow phenomenon occurs in the mold, and the mold may be damaged in some cases.

  Therefore, in the process of S30, the process of not starting the injection process of S40 is performed until the open state of all the valve gates is detected after the step of S31. In this process, the control device 7 determines reception of an open signal until it receives an open state detection signal (open signal) from the open confirmation proximity sensor 19 for each valve gate (S32, S33, S34, S35). Is repeatedly executed.

  When the control device 7 determines that the open signals have been received from all the open confirmation proximity sensors 19 (S35), the process of S30 is terminated and the screw 5 is moved to the mold side in order to start the injection process of S40. Control to advance is performed (S40). The molten resin maintained at a constant temperature in the heating cylinder 4 is injected into the main runner as the screw 5 advances, and flows into the first runner, the second runner, the third runner, and the fourth runner. It flows into the cavity through the one valve gate, the second valve gate, the third valve gate, and the fourth valve gate.

  In this injection process, in order to ensure the quality of the molded product, the injection operation is not stopped when the injection is completed, and the injection pressure is continuously applied until the molten resin in the mold has a certain hardness. Apply pressure.

  Next, in order to close each valve gate, the control device 7 sends air of a predetermined air pressure through the hose 12 so that the drive valves 14 are closed to all the valve gate opening / closing devices 8 to 11. 14 is moved to the closed position shown in FIG. When the close proximity proximity sensor 18 detects that the drive valve 14 is in the closed position, it sends a signal to the control device 7.

  When reception of the close signals from all close confirmation proximity sensors 18 is confirmed, a cooling process is performed in which the molten resin filled in the cavity is then cooled and solidified by cooling water passing through the mold. (S50). Then, the resin material is melted and measured so as to be parallel to the cooling step (S60). In S <b> 60, the resin material in the hopper 3 is introduced into the heating cylinder 4 by rotating the screw 5, and is melted by the frictional heat generated by the rotation of the heater wound around the heating cylinder 4 and the screw 5.

  The molten resin accumulates at the tip of the heating cylinder 4, while the screw 5 begins to retract due to the pushing force generated in the resin by its rotation. The metering of the resin material is determined by limiting the retreat distance of the screw 5. When the retreat distance is controlled to a predetermined value, the amount of resin injected in the next shot is stored in the heating cylinder 4.

  Next, a mold opening process for opening the fixed mold (female mold) and the moving mold (male mold) is performed (S70). The mold opening process is the reverse of the mold clamping process of S10, and the molded product is opened in a state of being fixed to the male mold.

  And the molded product protrusion process which removes the molded product fixed to the male mold is carried out (S80). In this step, the molded product is automatically dropped using the hydraulic pressure and the protruding structure of the mold device 6. When the series of steps S10 to S80 is completed as described above, a molded product for one shot is produced, and automatically returns to S10 to start production of the next shot, and the subsequent steps are continuously performed. carry out. A series of steps S10 to S80 is repeated for the number of shots.

  The plurality of hoses 12 are preferably the same length. The air pressure is controlled to 0.5 to 0.9 MPa, more preferably about 0.8 MPa. With such a configuration, variation in opening timing between the valve gates can be further reduced, and the time required for one shot can be reduced to increase productivity.

  The injection molding method of the present embodiment includes the steps S10 to S80. In the valve gate opening process of S30, control for driving the drive valve 14 of the bubble gate opening / closing devices 8 to 11 to the open position is executed. When the controller 7 detects that all of the plurality of valve gates 17 are in the open state by the proximity sensor 19 for confirmation of opening, the controller 7 starts injection of molten resin toward the mold cavity. To do.

  Even if there is a lag in the actual opening time of the valve gate 17 due to various factors after the control for opening the valve gate 17 is performed, all the valve gates 17 are completely opened according to this injection molding method. By starting the injection of the molten resin into the cavity after reaching the state, it is possible to start the molten resin from all the valve gates 17 at the same time, which is useful for reducing the variation in the quality of the molded product and preventing the breakage of the mold. .

It is the front view which showed the structure of the injection molding system for enforcing the injection molding method of 1st Embodiment in the partial cross section. It is the block diagram which showed the structure which controls the some valve gate opening / closing apparatus used with the injection molding method of 1st Embodiment. (A) is the schematic diagram which showed the state in which the valve gate is closed, (b) is the schematic diagram which showed the state in which the valve gate is open. It is the flowchart which showed the flow of the process of the injection molding of 1st Embodiment. It is the flowchart which showed the procedure of the valve gate opening process (S30) in FIG.

Explanation of symbols

6 ... Mold device (mold)
7. Control device 8. First valve gate opening / closing device (valve gate opening / closing device)
9. Second valve gate opening / closing device (valve gate opening / closing device)
10 ... Third valve gate opening / closing device (valve gate opening / closing device)
11 ... Fourth valve gate opening / closing device (valve gate opening / closing device)
17 ... Valve gate 19 ... Opening proximity sensor (sensor, proximity sensor)

Claims (5)

An injection molding method for injecting a molten resin used for an injection molded product into a cavity in a mold (6) having a plurality of valve gates (17),
After confirming that all of the plurality of valve gates (17) are in an open state by a plurality of sensors (19) detecting that each of the plurality of valve gates (17) is in an open state, An injection molding method characterized by starting injection of the molten resin into a cavity of a mold (6).   2. The injection molding method according to claim 1, wherein a proximity sensor (19) that detects, in a non-contact manner, that an object to be detected has approached is used as the plurality of sensors (19).   The injection molding method according to claim 2, wherein the proximity sensor (19) employs a method of using electromagnetic induction with a coil for generating a high-frequency magnetic field.   The mold (6) is a mold having a plurality of cavities and capable of taking a plurality of the same molded products, and at least one valve gate (17) is provided for each cavity of the mold (6). The injection molding method according to any one of claims 1 to 3, wherein the injection molding method is performed.   The injection molding method according to any one of claims 1 to 4, wherein the plurality of valve gates (17) are driven by air pressure.

Images