• 专利附录
  • 专利说明
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    • 专利摘要:

    公开号:SU1831427A3
    申请号:SU904743006
    申请日:1990-01-31
    公开日:1993-07-30
    发明作者:Yuekhara Tadaesi；Nakagava Tatsudzi；Oyamada Yasukhiko
    申请人:Aидa Иhджиhиpиhг Лtд；
    IPC主号:
    专利说明:

    The invention relates to a method for injection molding with extrusion and a device for its implementation, in particular, to a method for injection molding and a device for compression suitable for forming products that require high precision molding and uniformity when pressed such as, for example, optical lenses.
    wandering and pressure before the resin cools to a temperature at which the resin begins to cure at normal pressure. Under pressure, the glass transition temperature of the thermoplastic resin shifts to higher temperatures so that the thermoplastic resin cures with a slight decrease in temperature. The resin is cooled under pressure until the resin has the same dynamic stiffness as at normal temperature and pressure. With further cooling of the thermoplastic resin to the extraction temperature, the pressure acting on the resin is controlled so as to prevent an increase in dynamic stiffness due to cooling, and the dynamic stiffness of the thermoplastic resin during cooling is maintained at the same level as dynamic stiffness at normal temperature and pressure. A device for the implementation of the method of injection molding with extrusion. 2 s.p. f-ly, 8 ill.
    The aim of the invention is to develop an injection molding method and a device for compression molding, with which it is possible to obtain molded products with a high uniformity of internal composition without large temperature deviations at each point in the volume of the resin, even if the time required for the curing of the resin, in particular 1831427 AZ , the time required to exceed the glass transition temperature is reduced,
    Thermoplastic resins such as PMMA have the property that their dynamic stiffness increases as the resin cools, so that the resin hardens, and especially the dynamic stiffness increases sharply when the glass transition temperature is exceeded. Further, thermoplastic resins of this type have the property that their dynamic stiffness increases and the glass transition temperature shifts to higher temperatures with increasing pressure, even if the temperature of the resin remains the same.
    This means that thermoplastic resins, such as PMMA, cure at relatively high temperatures (for example, 125 ° C, at which the resin is in a melt state at normal pressure) when high pressure is applied to the thermoplastic resins.
    The present invention is made based on the use of the property that the resins cure at high temperature under pressure.
    In the present invention, molten thermoplastic resin is injected into the mold space and pressurized when it is cured, so that the resin cures almost completely in the region of slight temperature deviation and as a result, the temperature deviation at each point in the volume of the resin is reduced.
    In a general form, this invention is a combination of an injection molding method with compression, in which a predetermined amount of molten thermoplastic resin is injected into the mold volume of a metal mold, and the resin is cooled to obtain a molded article under pressure control applied to the injected metal press thermoplastic resin form.
    The device of the metal pres-form includes a stationary metal half-mold and a movable metal half-mold located opposite each other. The movable metal half-mold can move within the first position in which the movable half-mold interacts with the stationary half-mold, forming a molding volume that is almost identical to the volume of the product, within the second position, in which the movable half-mold interacts with the stationary half-mold, forming a molding volume exceeding the volume of the product, and within the third position, in which the movable half-mold is separated from the stationary half-mold.
    Before the start of the injection operation, the movable half-mold moves to the second position, forming a molding volume exceeding the product volume. Next, using the temperature control means, the temperature of the metal mold is set higher than the temperature at which the thermoplastic resin begins to cure at normal pressure.
    The molten thermoplastic resin is measured using measuring and injection devices and a predetermined quantity thereof is injected into the forming space through the gating devices. The injected resin is rapidly cooled to a predetermined mold temperature as a result of heat exchange with the mold.
    The pressure adjusting means increases the pressure applied to the thermoplastic resin in the metal mold before the injected thermoplastic resin cools to a temperature at which the resin begins to cure at normal pressure. Since the temperature of the metal mold is pre-set to a temperature exceeding the temperature at which the resin begins to cure at normal pressure, the thermoplastic resin in the mold is maintained in the molten state at the beginning of the application of pressure and, accordingly, the pressure force acts on the entire thermoplastic resin in mold evenly.
    If a pressure force is applied to the thermoplastic resin and thus the achievement of a dynamic stiffness greater than the dynamic stiffness at the glass transition temperature, under temperature conditions at the beginning of the application of pressure. then the thermoplastic resin hardens from the beginning of the application of pressure without lowering the temperature (or with a slight decrease in temperature) and its dynamic stiffness becomes greater than the dynamic stiffness at the glass transition temperature, so that the resin hardens.
    When a thermoplastic resin in the molten state cures when pressure is applied, deviations of the pressure force and temperature deviations at each point in the mass of resin in the process of curing are extremely small.
    A thermoplastic resin cured by applying pressure is cooled to a temperature at which the same dynamic stiffness is achieved as at normal temperature and pressure, while maintaining pressure.
    Since a thermoplastic resin cured by pressure has a temperature at which the resin is still in a melt state at normal pressure, its dynamic stiffness decreases and the resin softens if pressure is reduced. However, thermoplastic resins of this type have the property of increasing their dynamic stiffness when the resin is cooled.
    Accordingly, the temperature control means gradually reduces the temperature of the mold in order to cool the thermoplastic resin cured under pressure. to the extraction temperature of the product, and the means for regulating the pressure reduces the pressure force, so that the increase in dynamic stiffness due to cooling is excluded. Thus, the thermoplastic resin is molded while maintaining the same dynamic stiffness as at normal temperature and pressure.
    A device for injection molding with extrusion is illustrated by the following figures.
    Figure 1 presents a characteristic diagram showing the dependence of the dynamic stiffness of PMMA. as an example of a thermoplastic resin, from temperature at various pressures.
    Figure 2 is a cross-sectional view of a direct injection type injection molding machine according to one embodiment of the present invention;
    On Fig.3 shows a cross section of a cylinder for adjusting the margin of compression, as an example of a device for increasing the forming volume:
    Fig. 4 is a cross-sectional view showing an example of a valve mechanism for driving a compression reserve adjustment cylinder shown in Fig. 3:
    Fig. 5 is a cross-sectional view showing an example of a plasticizing device and a measuring and injection device:
    6 is a diagram of a control system of the present invention;
    Figure 7 shows a cross section of a gate device;
    On Fig presents a graph illustrating the control properties during molding.
    The following is a detailed description of one embodiment of the present invention with reference to the drawings.
    Figure 1 shows the temperature dependence of the dynamic stiffness of PMMA, as an example of a thermoplastic resin, for various pressures.
    1, curves a. b, c, d, e, and f show the dynamic stiffness versus temperature pr pressure 1,200, 400,600, 800, and 1000 bar, respectively. The temperature dependence of the dynamic stiffness curve for PMMA shifts to the region of higher temperatures by 0.025 ° С with each increase in pressure by 1 bar.
    Next, in figure 1, the points ai, bi. ci. di. ei and fi are the points at which the PMMA begins to cure at the corresponding pressure value, the points a z , b z , c z , d z , e z and f z are the points at which the PMMA cures to a state preceding the glass transition temperature at each value corresponding pressure, points a 3 , b3. sz. d3. ez and f3 are points at which the PMMA is cured to a state exceeding the pressure and points az, bd, C4, d ". e4 and f4 are points at which the PMMA is completely cured at each value of the corresponding pressure.
    Under a pressure of 1 bar, PMMA is completely in a melt state in the temperature range exceeding 130 ° C. It begins to cure at about 125 ° C upon cooling, dynamic stiffness preceding the glass transition temperature is achieved at. 120 ° C, a dynamic stiffness exceeding the glass transition temperature is achieved at 115 ° C, and the PMMA completely cures at about 100 ° C.
    On the other hand, under pressure conditions of 1000 bar, PMMA is completely in the melt state in the temperature range exceeding 155 ° C. ' it begins to cure at about 150 ° C, with cooling, dynamic stiffness preceding the glass transition temperature is reached at 145 ° C, dynamic stiffness exceeding the glass transition temperature is reached at 140 ° C, and completely PMMA cures at 125 ° C.
    It is thermoplastic resins such as PMMA. completely cured even
    Ί at a relatively high temperature, when such a resin is exposed to high pressure. Accordingly, the present invention is made using the property of thermoplastic resins such that the resin cures upon application of pressure.
    In the present invention, the temperature of the metal mold is initially set to be higher than the temperature at which the thermoplastic resin begins to cure at normal pressure and the thermoplastic resin is in a molten state until the injection operation is completed.
    After the injection is completed, pressure is applied to the thermoplastic resin to cure it at high temperature, and the resin cured under pressure is cooled. Simultaneously with cooling, the pressure applied to the thermoplastic resin is controlled in this way. that the dynamic stiffness of temoplastic resin is maintained constant during cooling. Namely, the temperature and pressure are controlled so as to cool the thermoplastic resin so as to maintain the dynamic stiffness of the resin at normal pressure and temperature.
    Figure 2 presents a cross section of a device for injection molding with extrusion according to one of the embodiments of the present invention.
    The injection molding apparatus according to the present invention is formed by a box-shaped frame 1, and the frame 1 is divided into chambers 2, 3. 4 and 5 by means of dividing walls.
    The chamber 2 is an oil tank that is filled with oil and in which the hydraulic oil pump 6 is located.
    chamber 3 is a motor 7 for driving an oil hydraulic pump
    6. which is connected to the motor 7 through an opening in the separation wall 8 between the chambers 2 and 3. The hydraulic oil pump b and motor 7 comprise an oil hydraulic unit for supplying oil to all hydraulic oil devices.
    Above the chamber 4, a locking device for the mold 9 is mounted.
    The stationary plate 10 of the press for attaching the half-mold 11 is fixedly mounted on the upper wall of the chamber 4. The plate of the press 12 for mounting the cylinder, on which the cylinder 13 of the mold clamping device is mounted, is fixedly mounted on the upper ends of the connecting bars 14, which are fixedly mounted at the four ends of the stationary plates 10 of the press for attaching the half-mold 11. The movable plate of the press 15 is connected to the piston rod 16 of the cylinder 13 of the clamping unit of the mold so that it can move up and down along the connecting plan to 14.
    Further, the stationary metal half-mold 11 is removably mounted on the stationary plate 10 of the press for fixing the form. and the movable metal half-mold 17 is also removably mounted on the movable plate 15 of the press for fastening the mold.
    Each of the connecting strips 14 is equipped with cylinders 18, to create a margin of compression, which provide a predetermined compression ratio on the contact surface between the stationary and movable half-molds before the start of the injection operation. The compression margin is determined by the gap formed previously on the contact surface of the mold in order to reduce the volume of resin that occurs during compression molding of the resin melt.
    FIG. 3 is an enlarged cross-sectional view of a cylinder 18 for adjusting a compression ratio in which the same elements as in FIG. 2 are denoted by the same numbers.
    At the lower end of the connecting strips 14 there is a bolt or thread 19, which passes through the cavity 20 formed in the stationary plate 10 of the press for fixing the form. The nut 21, which is equipped with a bolt 19, is located on the upper surface of the cylinder 18 to control the degree of compression. The bolt 19 is tightly screwed to the nut 21, so that the connecting strips 14 and the cylinder 18 are attached to the stationary plate 10 of the press for mounting the form.
    A chamber 22 is formed in the lower part of the adjusting cylinder 18, and a piston 23 is located in the chamber 22 so that the piston 23 can move vertically. The lower hole of the chamber 22 is closed by a cap 24 having a through hole through which the piston rod 23 slides. Digital 25 indicates the channel of the control cylinder.
    The lower cylindrical casing 26 includes a nut 21 located in the center of the casing 26, which is screwed to the bolt 19 at the lower end of the piston rod 27.
    The stud 28 is inserted into the guide hole 29 in the stationary press plate 10 for fastening the molds movably vertically, and the lower end of the stud 28 rests on the upper surface of the casing 26.
    A spacer ring 30 is arranged around the connecting bars 14 so that this ring can move up and down along the connecting bars 14. Accordingly, when oil is supplied through the channel 25 so that the piston 23 is lowered into the chamber 22, the piston rod 27, the casing 26. stud 28 and the spacer ring 30 rise together.
    On the other hand, the cylindrical intermediate elements 31 are fixedly mounted on the lower surface of the movable plate 15 of the mold holding press and close the outside of the connecting bars 14. Thus, when the spacer ring 30 moves upward, as described above, the movable plate 15 of the mold holding press 31 also moves up together with the intermediate elements 31 and creates a margin for compression. The length of the intermediate elements 31 is sufficient so as not to impede the opening and closing operations of the molds when the gasket ring 30 is lowered, and to create a reserve of compression when moving the gasket ring 30 up.
    The compression cylinder 18 and its associated mechanism serve to establish an exact compression margin in order to obtain a molded product of an exact size.
    In particular, the piston rod 16 is designed to minimize the margin of compression to zero. Under such a condition, when the cylinder 18 for adjusting the compression ratio moves against the direction of movement of the cylinder 13 of the mold closing assembly, a predetermined compression margin is created. After the compression margin reaches the set value, thermoplastic resin is injected into the mold. After the injection operation is completed, the pressure applied to the cylinder 18 is reduced and the piston rod 16 moves forward, as a result of which the mold is closed.
    The present embodiment of the invention is characterized in that the hydraulic oil circuit connected to the channel 25 of the cylinder 18. is completely closed when the preset value of the compression margin is reached, so that the cylinder 18 acts in much the same way as the so-called mechanical lock for precise locking stock on compression.
    In accordance with this, it is necessary that the valve mechanism, providing the action of the cylinder 18 to adjust the degree of compression, be able to regulate the flow with a low flow rate and have high speed when closing.
    Figure 4 presents a cross section of a valve mechanism that provides the operation of the cylinder 18 to control the degree of compression. The valve mechanism 32 provides a gradual release of oil depending on the pulses from the pulse oscillator 33.
    The valve mechanism 32. depicted in figure 4. includes flow channels 34 and 35. located parallel to each other between the input 36 and output 37 and intended for the passage of oil as a result of a short alternate opening of the flow channels 34 and 35 synchronously to the pulses from the pulse oscillator 33.
    In particular, the lead finger 38. made of soft magnetic iron, and connected to the axis 39, floats in a magnetic field. Each time the pulses from the oscillator 33 fall on the turns 40 and 41, wound around the lead finger 38. The polarity of the lead finger 38 changes. causing the finger to float. In the state shown in FIG. 4, the ball 42 in the control valve 43 rises up together with the pin 38 under the pressure in the control valve generated by the pressure source in the control valve 43, and the pressure of the control valve is transmitted to the compression chambers 44 and 45.
    Accordingly, since the tubular valve 46 opens the seat of the valve 47. while the tubular valve 48 closes the seat of the valve 49, the flow channel 34 is generally closed. Further, as soon as the tubular valve 50 opens the valve seat 51. and the tubular valve 52 closes the valve seat 53, the flow channel 35 is generally closed. A dose of oil does not flow from inlet 36 to outlet 37.
    In this state, when the polarity of the pulses from the pulse oscillator 33 changes, the lead finger 38 rotates clockwise in the figure, since the right and left polarities of the lead finger 38 are opposite. Accordingly, the ball 54 in the control valve 55 rises up together with the finger 56 under the pressure in this valve applied from the pressure source of the control valve 57 and the pressure of the control valve is transmitted to the chambers 58 and 59.
    Thus, under the pressure of the control valve applied to the chamber 58, the valve seat 47 closes with the tubular valve 46, and the tubular valve 52 opens the valve seat 53. whereas with increasing pressure in the chamber 59, the tubular valve 50 closes the valve seat 51 and the tubular the valve 48 opens the valve seat 49. However, since there is an opening 60 between the control valve 55 and the compression chamber 59. There is a time delay from opening the valve seat 53 to the tubular valve 52 to closing the valve seat 51 to the tubular valve Pan 50, the oil flows through the flow channel 35 from the inlet 36 to the outlet 37
    When the polarity of the pulses from the pulse oscillator 33 changes again, the pressure of the control valve is re-created in the compression chambers 44 and 45 and the valve mechanism 32 returns to the position shown in FIG. 4. However, since there is an opening 61 between the control valve 57 and the compression chamber 45, there is a delay from the beginning of the opening of the valve seat 47 to the pipe valve 46 to the closing of the valve seat 49 by the pipe valve 48. The flow channel 34 is open during this delay and, accordingly, oil flows through the flow channel 34 from the input 36 to the exit 32.
    Thus, since the valve mechanism shown in FIG. 4 ensures that the oil flows from the inlet 36 to the outlet 37 only at the time delay determined by the holes 60 and 61, each time the polarity of the pulses from the oscillator 33 changes, the flow rate it is precisely regulated as a whole in accordance with the frequency of the pulses, and the hydraulic oil circuit from the inlet 36 to the outlet 37 is completely closed by means of tubular valves due to the shutdown of the pulse oscillator 33 to satisfy the requirements yes Nogo invention.
    In figure 2, the number 62 denotes a measuring and injection device, which includes a nozzle directed upward. The numeral 63 denotes a plasticizing device that plasticizes the initial resin before feeding it into the measuring and injection device 62. The measuring and injection device 62 is located in the chamber 4, and the plasticizing device 63 is located in the chamber 5. The device 62 is connected to the plasticizing device 63.
    In this embodiment, the plasticizing device 63 is located on the platform 64.
    The plasticizing device 63 moves along with the measuring and injection device 62 along the rail 65 and rotates around the axis 66 in a vertical plane. The nozzle 67 is located in accordance with the movement of the platform 64 and is connected to the sleeve of the vertical gate 65 of the stationary press plate 10 for fastening the molds by rotation around the axis 66.
    Measuring and injection device 62. The plasticizing device 63 and the associated mechanism must ensure accurate measurement of the resin melt at the appropriate temperature and injection of the molten resin. 5 is a cross-sectional view of a valid example of the measuring and injection device 62 and the plasticizing device 63.
    In Fig. 5, those elements described above are indicated by the same numbers as in the previous figures.
    The plunger 64 is inserted into the lower opening of the injection cylinder 65 and is moved up and down by the oil hydraulic cylinder 66.
    A check valve 68 is located at the top of the injection cylinder 65.
    The inner diameter of the lower inner part 69 of the injection cylinder 65 located near the hydraulic oil cylinder 66 is larger than the inner diameter of the upper inner part 70 of the cylinder located near the nozzle 67, and a step is formed between the lower inner part 69 and the upper inner part 70 of the injection cylinder 65 The lower inner part 69 of the injection cylinder 65 and the outer part 71 of the plunger 64 seal each other. A gap is formed between the upper inner part 70 and the outer part of the plunger 64, and the plasticized resin flows through this gap into the injection cylinder 65.
    The plunger 64 is moved by the pressure difference between the resin in the injection cylinder 65 and the hydraulic oil cylinder 66.
    Numeral 72 denotes a heating element for heating the injection cylinder 65, 73 denotes a temperature sensor that detects the temperature of the resin in the injection cylinder 65, and 74 denotes a pressure sensor that detects pressure in the injection cylinder 65. Number 75 denotes a position sensor, for example, of an optical type, which determines the reciprocal of the plunger 64. The amount of resin injected during one injection cycle is determined based on the data of the temperature sensor 73. pressure sensor 74 and position sensor 75. Since the position sensor 75 can detect the reverse stroke of the plug 64, its location is not limited to that position, which is shown in Fig.5.
    The plasticizing device is designed to melt the initial resin supplied to the plasticizer cylinder 76 from the funnel 77, which is heated using the heating device 78. The screw 79 is driven by the cylinder 80, as a result of which the flow channel is opened and closed between the plasticizing cylinder 76 and the injection cylinder 65.
    The mechanism described above is controlled by the system depicted, for example, in FIG. 6,
    6, the elements described above are indicated by the same numbers as in the previous figures, and their description is omitted. Only those elements that have not been described above are considered.
    Numeral 81 denotes a valve mechanism including a known servo valve for converting electrical energy into hydraulic energy, and a pressure control valve of a known type. Valve mechanism 81 is connected to channels 82 and 83 of cylinder 13 of the mold closing assembly. The piston rod 16 is actuated by supplying oil to the channel 82 through the valve mechanism 81.
    Likewise, 86 indicates a valve mechanism including a servo valve of a known type for converting electrical energy into hydraulic energy connected to channels 87 and 88 of the injection cylinder 66. The injection operation is performed by supplying oil to the channel 87 through the valve mechanism 86.
    Numeral 89 The solenoid type directional control valve is used, which is used to supply oil to cylinder 80, which, in turn, is connected to any pressure source or manifold in accordance with the state of operation of directional control valve 89
    Numeral 90 denotes a shutoff valve to shut off the hydraulic oil circuit of cylinder 18 to create a margin of compression.
    The number 91 indicates a photo switch, which is an example of a sensor for determining the compression margin. The pulses from the photo switch 91 in accordance with the reverse movement of the movable plate 15 of the press for mounting the form are transmitted to the controller 92.
    Numeral 93 denotes a heater, which is used to create the temperature of the resin in a metal mold. The design and shape of the heater 93 is different and depends on the shape of the metal mold. The number 94 indicates the starting device of any known design. 95 is a storage device and 96 auxiliary storage device.
    TSz is a temperature sensor for detecting the temperature of the resin in the mold, PSz is a pressure sensor for detecting the pressure of the resin in the mold, and TSa 97 is a temperature sensor for detecting the temperature of the resin in the plasticizing cylinder 76.
    Next, the number 98 denotes a solenoid valve, which is designed to seal the gate in the mold 11. The configuration, close to real, is presented on an enlarged scale in Fig.7.
    The solenoid valve 98 is connected to the cylinder 99. The cylinder 98 actuates the stem 100 in response to the excitation of the circuit of the solenoid valve 98 and closes the gate, and the cylinder 99 moves the rod 100 back in response to shutting off the circuit of the solenoid valve 98 and opens the gate.
    The operation of the device is as follows in stages:
    Injection molding with compression according to this invention, the step of plasticizing the resin in the plasticizing cylinder 76: the operation of creating a reserve of compression using the cylinder 13 of the clamping unit of the mold and cylinder 18 to control the degree of compression: the injection operation using the injection cylinder 65 and the compression molding operation cylinder 13 of the clamping unit of the mold and metal half-molds 11, 17. The diagram shown in Fig. 9 will facilitate understanding of the sequence of process steps.
    Firstly, various data are stored in the starting device 94, such as, for example, the temperature of the salt before injection, the amount of resin injected per molding cycle, injection pressure, injection rate, compression margin, a series of data regarding the temperature in a metal mold, a series of data regarding the clamping force of the mold, and the like, which are stored in the storage device 95 and the auxiliary storage device 96.
    Heater 78 is set to 190 ° C — the temperature of the PMMA to be injected.
    In the initial state, the controller 92 suppresses the excitation of the control valve direction 89, so that the cylinder 80 is connected to the manifold through the control valve direction 89.
    Accordingly, the tubular valve 85 opens a channel between the plasticizing cylinder 76 and the injection cylinder 65.
    PMMA coming from funnel 77 is heated by heater 78 and melts.
    When the temperature sensor 97 determines that the temperature of the PMMA in the cylinder 76 has reached 190 ° C, the controller 92 drives the motor 84. which rotates the screw 79.
    At this point, the valve mechanism 86 provides a pressure balance between the channels 87 and 88 of the oil hydraulic cylinder 66. Accordingly, the plunger 64 can freely move up and down in the injection cylinder 65 in accordance with the magnitude of the external pressure.
    In the initial state, since the solenoid valve 98 is in the excited state and the stem 100 closes the gate, the molten PMMA flows from the plasticizing cylinder 76 into the injection cylinder 65 in response to the rotation of the screw 79. and the plunger 64 moves back.
    As soon as the injection cylinder 65 is filled with PMMA, the plunger 64 will move back, and the reciprocal amount of PMMA will be determined using the position sensor 75. When the controller 92 determines that a predetermined amount of PMMA has accumulated in the injection cylinder 65 by the fact that the output signal of the position sensor 75 Having reached the set value, the controller 92 will drive the control valve circuit direction 89.
    The cylinder 80 is connected to a pressure source in response to the excitation of the control valve of the direction valve 89 and the shutoff valve between the plasticizing cylinder 76 and the injection cylinder 65 is closed. Thus, a predetermined amount of PMMA is found in the injection cylinder 65.
    As described above, in this embodiment of the present invention, the output of the position sensor 65 determines that the injection cylinder 65 is filled with a predetermined amount of PMMA, while the volume of PMMA varies slightly depending on temperature and pressure.
    Accordingly, in this embodiment of the present invention, the conditions for opening the cylinder 80 are adjusted using the output from the pressure sensor 73 and the temperature sensor 72.
    In particular, the volume of PMMA decreases with increasing pressure applied to the PMMA. Accordingly, the controller 92 receives a signal about the necessary adjustment, so that the reference volume relative to the output signal of the position sensor 75 decreases with increasing pressure detected by the pressure sensor 73, and the reference volume relative to the output signal of the position sensor 75 increases with decreasing pressure detected by the pressure sensor 73.
    Further, the volume of PMMA decreases with decreasing temperature. Accordingly, an adjustment signal is supplied to the controller 92, so that the reference volume with respect to the output of the position sensor 75 decreases with decreasing temperature detected by the temperature sensor 72, while the reference volume with respect to the detected output of position sensor 75 increases with increasing temperature detected temperature sensor 73.
    When the injection cylinder 65 is filled with a predetermined amount of PMMA as described above, the controller 92 controls the process of creating a margin of compression.
    In this embodiment of the invention, since the compression cylinder 18 provides a margin of compression compared to the cylinder 13 of the mold closing assembly, the valve mechanisms 81 and 32 are adjusted so that the relation Pi · Ai <Pz · Az and the difference the ratio turns out to be extremely small when the inner diameter of the cylinder 13 of the mold closure assembly is At. the oil pressure in it is Pi, the internal diameter of the compression reserve adjustment cylinder is Az and the oil pressure in it is Pz.
    Further, the shut-off valve 90 is turned off and the channel 25 of the compression reserve adjustment cylinder 18 opens. Pulse oscillator 33 stops working,
    In this state, the controller 92 turns on the valve mechanism 82 and oil supply to the channel 82 begins. At this time, since the pressure in the cylinder 18 for controlling the compression ratio is reduced, the piston rod moves forward and the compression margin between the movable half-mold 17 and the stationary half-mold 11 decreases to zero, so that the force Ρι · Ai arises on the contact surface between the movable half-mold 17 and the stationary half-mold 11.
    When the margin for compression is reduced to zero, the controller 92 includes a shut-off valve 90 and a pulse oscillator 33 and receives pulses from the photo switch 91.
    When the oscillator 33 gives pulses, the valve mechanism 32 gradually releases oil in response to each series of pulses. Next, the shut-off valve 90 moves to the closed position. Accordingly, the oil passing through the valve mechanism 32. enters the channel 35 of the cylinder 18 to adjust the compression ratio.
    Between the power of Ρι · Ai. provided by the cylinder 13 of the clamping unit of the molds, and the force Ρζ'Αζ provided by the cylinder 18 to control the compression ratio, the relation Pi · Ai <<Pz * Az arises.
    Accordingly, the piston 23. shown in FIG. 3 moves back into the chamber 22. Since the casing 26 rises when the finger 28, the spacer ring 30, the intermediate member 31 and the movable plate 15 of the press are secured, the margin compression S increases.
    The photo switch 91 sends pulses in accordance with the upward movement of the movable plate 15 of the press for fastening forms. The controller 92 adds pulses from the photo switch 92 in order to achieve the current value of the compression margin S. Upon reaching the current value of the compression margin S. equal to the set value of the compression margin S. stored in the memory of the memory 95. the pulse oscillator 33 is turned off.
    As described above, when pulses from the oscillator 33 do not arrive at the valve mechanism 32, since the flow channels 33 and 34 between the inlet 36 and the outlet 37 are completely blocked by the tubular valve mechanism. And the shut-off valve 90 is also turned off, the duct for the outflow of oil supplied to the cylinder 18 to control the degree of compression, completely blocked.
    Since the cylinder 13 of the mold clamping unit creates an additional force Ρι · Αι in the cylinder 18 to control the compression ratio, the full length of the adjustment cylinder 18 is set when the relation Pi · Ai = Pz · Az is fulfilled.
    and the amount of compression margin S is also set.
    At this point, the pressure in the cylinder 18 varies from Pz to Pz 1 . while the compression ratio of the oil in the cylinder 18 is in the numerical range in which compression can be neglected in comparison with the margin of safety S.
    Thus, when the appropriate compression margin is set, the controller 92 controls the PMMA injection process.
    The temperature of the heating device 93 for the metal mold is set to 125 ° C. which is an example of the temperature to which PMMA begins to cure at normal pressure.
    The temperature of the heating device 72 for the injection cylinder 65 is set to 190 ° C., which is an example of the temperature at which the PMMA does not begin to cure at any pressure.
    Accordingly, PMMA in injection cylinder 65 is completely molten.
    The controller 92 turns off the solenoid valve 98. shown in Fig.7, in order to open the gate. After that, the controller 92 includes a valve mechanism 81 to ensure that oil is supplied to the channel 87 of the hydraulic oil cylinder 66. Accordingly, the plunger 64 is moved forward in the injection cylinder 65, so that the molten PMMA is injected into the forming cavity formed by the movable metal half-mold 17 and stationary metal half-mold
    eleven.
    The pressure in cylinder 18 is somewhat different from the injection pressure at this point. However, the pressure in the cylinder 18 is a reactive force against the force acting between the stationary press plate 10 for securing the molds and is independent of the external hydraulic oil circuit. In addition, since the injection pressure is extremely small, the compression margin S remains virtually unchanged.
    After the injection process is completed, the solenoid valve 98 is turned on and the gate closes. After this, the shut-off valve 90 is turned off and the pressure in the cylinder 18 is reduced, so that it is possible to perform compression molding of PMMA.
    The resin injected into the metal mold is rapidly cooled to 125 ° C, i.e. to the originally set temperature, due to heat exchange with a metal mold.
    The temperature detected by the TSz temperature sensor in the metal mold increases due to heating during injection of PMMA having a temperature of 190 ° C, and then the temperature detected by the TSZ sensor decreases again due to cooling of the PMMA.
    As indicated above, PMMA does not cure at a pressure of 1 bar until its temperature drops to about 125 ° C, and PMMA begins to cure at about 150 ° C at a pressure of 1000 bar.
    In this embodiment of the present invention, when the temperature sensor TSz detects the PMMA temperature at which it does not yet begin to cure under lower pressure, but begins to cure when pressure is applied to it, the valve mechanism 81 is controlled so that a sharp increase in the closing force of the cylinder is provided 13 knots of the mold, so that PMMA in a metal mold is heated under pressure to achieve a dynamic stiffness greater than its dynamic stiffness at temperature teklovaniya with a slight decrease in temperature.
    The curve shown by the thick line in Fig. 8 shows an example of a control curve of temperature and pressure during curing.
    When PMMA is injected into a metal mold, the temperature of PMMA drops to 145 ° after some time after the gate is closed. When the size of the product is large, this is the case when the temperature of the resin is gradually reduced to 145 ° C until the gate is closed, in which case the injection speed is increased or the initial temperature of the metal mold is set at a temperature above 125 ° C and adjusted so that each part of PMMA is evenly cooled to approximately 145 ° C.
    When PMMA is cooled to about 145 ° C at normal pressure, it remains completely in the melt state, and accordingly, the pressure acts uniformly on each part of the PMMA.
    In this embodiment of the invention, a PMMA with a temperature lying in the temperature range at which the PMMA remains completely in the melt state is applied with a pressure that increases sharply, while the dynamic stiffness of the PMMA sharply increases during a slight decrease in its temperature.
    When the temperature detected by the TSz sensor reaches 145 ° C (Pi points in FIG. 8), the controller 92 includes a valve mechanism 81 for increasing the pressure acting in the channel 82 of the cylinder 13 of the mold closing assembly, resulting in PMMA in a metal mold pressure is applied, for example, 600 bar.
    Thus, the dynamic stiffness of PMMA increases when pressure is applied to it, as described above, and the dynamic stiffness reaches E x 10 (dyne / cm 2 ), which characterizes the state immediately before the glass transition temperature, when the PMMA is cooled to 135 ° C (point Pz in FIG. .8), E is a coefficient depending on the type of resin.
    When the TSz temperature sensor detects that the PMMA is cooled to 135 ° C, the controller 92 turns on the valve mechanism 81 and the pressure acting in the channel 82 of the cylinder 13 of the mold closing assembly increases, so that a pressure of 1000 bar acts on the PMMA in the metal mold.
    This increase in pressure leads to a further increase in the dynamic stiffness of PMMA, and when the PMMA is cooled to 133 ° C (point Pz in Fig. 8), the dynamic stiffness completely exceeds this parameter at a glass transition temperature. When cooled to 130 ° C (point Pd in Fig. 8), PMMA is almost completely cured and at a temperature of 125 ° C (point Pb in Fig. 8), PMMA is completely solid,
    With such a control as described above, since the dynamic stiffness of PMMA exceeds this parameter at a glass transition temperature, when PMMA is cooled in a small ’temperature range of 2 ° C from 135 ° C to 133 ° C. then the total cooling time is extremely short, and the productivity of the process increases, even if the cooling rate in a small temperature range is small enough to avoid any temperature deviations in each part of the PMMA until the glass transition temperature is exceeded.
    There is no need to say that the required cooling rate to exceed the glass transition temperature is different and depends on the thermal conductivity of the resin, the shape of the product, etc. In the manufacture of a large or multi-molded molded product, the temperature of the metal mold is set to a higher value or the temperature of the metal mold is gradually reduced so that the temperature deviation in each part of the resin is small.
    PMMA is completely cured at a temperature of 125 ° C and with a pressure of 1000 bar applied to it, as described above. However, as can be seen from figures 1 and 8, the temperature of 125 ° C is the temperature at which the PMMA begins to slightly cure at normal pressure. Accordingly, when PMMA. being under the influence of pressure applied to it, returns to the conditions of normal pressure, then the PMMA again begins to soften. Therefore, in order to remove the molded product, the PMMA must be cooled to a temperature (i.e., up to 100 ° C) at which the PMMA is completely cured at normal pressure.
    Accordingly, in this embodiment of the present invention, the set temperature in the metal mold by the heater
    9.3 is gradually reduced in order to cool PMMA to 100 ° C, which is the mold extraction temperature in the closed state at which pressure applied by valve mechanism 81 is applied in the channel 82 of cylinder 13 of the mold clamping unit, while if high pressure 1000 bar continuously affects the PMMA, which is in the solid state, then plastic deformation develops in the molded product.
    As described above, when the PMMA has a certain dynamic stiffness, the temperature of the PMMA is changed to 0.025 ° C each time the applied pressure changes by 1 bar.
    Accordingly, the controller 92 controls the action of the valve mechanism 81. while the TSz temperature sensor monitors the temperature in the metal mold. Thus, every time the temperature of PMMA decreases by 1 ° C, the pressure acting on PMMA decreases by 40 bar, so that the molded product is obtained under conditions of maintaining uniform dynamic stiffness of PMMA.
    As indicated above, temperature and pressure are controlled by a known setpoint.
    As indicated above, in the case when the pressure decreases by 40 bar each time the temperature decreases by 1 ° C, the pressure decreases to 800 bar at 120 ° C, to 600 bar at 115 ° C, to 400 bar at 110 ° C . up to 200 bar at 105 ° C and normal pressure at 100 ° C.
    When the molding operation is completed as described above, the controller 92 includes a valve mechanism 81 for supplying oil to the channel 82 of the cylinder 13 of the mold closing assembly, as a result of which the movable metal half-mold 17 is lowered and the molded product is removed using an ejector mechanism of a known type, in the diagram not shown.
    The essence of this invention lies in the fact that the resin, which is in a state of melt at normal pressure, but heated to a temperature at which it begins to cure when pressure is applied to it, is subjected to pressure and cured to above the glass transition temperature with a slight decrease in temperature. However, there is no need to say that the temperature of the resin before injection, the initially set temperature of the metal mold, the temperature at the beginning of the application of pressure and the applied pressure, etc. will be different depending on the type of resin, the size of the molded product, the shape of the product, etc., during the molding time will also be different depending on these conditions. For each molded product, it is necessary to determine the optimal molding conditions.
    In the above embodiment of the present invention, reference is made to a specific example regarding a measuring and injection device and a plasticizing device, although their configuration is not limited, since the temperature of the resin before injection can be precisely controlled and the amount of resin can also be accurately measured.
    Further, in the above embodiment of the present invention, reference is made to a mechanism for adjusting the compression ratio, although its configuration is also not limited, since it is possible to ensure compliance with the accuracy requirement for adjusting the compression margin.
    As described above, in the present invention, since when the injected resin is cooled to a temperature at which its state in the melt is maintained at normal pressure and curing begins when pressure is applied to it, the resin is subjected to pressure in order to cure it and achieve a dynamic stiffness greater than dynamic stiffness at the glass transition temperature, the resin exceeds the state. characteristic of the glass transition temperature, while its temperature decreases slightly.
    Accordingly, since the temperature reduction required to exceed the glass transition temperature, the molten resin is extremely small, even if the cooling rate is insignificant and temperature deviation does not occur in each part of the resin during this process, while it is necessary to exceed the glass transition temperature , few.
    According to this invention, since the initial set temperature of the metal mold is higher than the temperature at which the resin begins to cure at normal pressure, and the resin is completely in the melt state at the beginning of the application of pressure, the pressure acts uniformly on each part of the resin, both cured and molten parts do not form in the resin during molding. Accordingly, it is difficult to obtain partial plastic deformation and the lack of uniformity of the internal composition, and it is easy to manufacture a molded product that is superior in uniformity to the internal composition of the product, still produced.
    In addition, according to this invention, since the temperature of the resin and the pressure generated on the resin are controlled, so that an increase in dynamic stiffness due to a decrease in temperature and a decrease in dynamic stiffness due to a decrease in pressure are mutually exclusive until the cured resin cools to the extraction temperature, then in the process the cooling resin maintains constant dynamic stiffness, and this property of the molded product does not deteriorate upon cooling,
    权利要求:
    Claims (2)
    [1]
    Claim
    1. A method of injection molding injection molded products, in which a predetermined amount of molten thermoplastic resin is supplied under pressure into a metal mold made with a molding space, the temperature and pressure are regulated, and the thermoplastic resin injected into the mold is cooled while the pressure exerted is controlled on the resin, characterized in that, in order to increase the efficiency of the molding process, the thermoplastic resin is injected with a mass equal to the mass of the molded product into the mold, performed with a molding space in excess of the volume of the molded product, while the mold temperature is pre-set at a level higher than the temperature at which the resin begins to solidify, the pressure applied to the thermoplastic resin fed into the mold is increased until the resin cools to the solidification temperature at normal pressure, the resin is cooled in a state of pressure applied to it to a temperature at which the dynamic stiffness of the resin is leveled, it is additionally cooled to a temperature removal of the product with a decrease in pressure so that the dynamic stiffness of the resin is maintained equal to the dynamic stiffness of the resin at normal temperature and normal pressure.
    [2]
    2. A device for injection molding of articles with extrusion, containing a metal mold with half-molds located opposite one another, one of which is mounted for movement by means of a hydraulic cylinder, means for introducing material, means for measuring, locking means, characterized in that, for the purpose of increasing the efficiency of the molding process, it is equipped with a means for controlling the temperature in the molding space to a temperature exceeding the temperature at which the thermoplastic resin begins harden under normal pressure with a means for regulating the pressure on the resin until the glass transition temperature of the resin exceeds the temperature of the resin fed into the mold until the resin cools to solidification temperature under normal pressure, and the means for expanding the forming space is equipped with a fixation sensor working stroke of the cylinder.
    FIG. /
    1B31427
    FigZ (Dw.5
    7
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    同族专利:
    公开号 | 公开日
    EP0369009A1|1990-05-23|
    DE3886759D1|1994-02-10|
    JPH0550972B2|1993-07-30|
    KR960007282B1|1996-05-30|
    US5108689A|1992-04-28|
    EP0369009A4|1991-01-09|
    WO1989011960A1|1989-12-14|
    DE3886759T2|1994-05-19|
    JPS63139720A|1988-06-11|
    EP0369009B1|1993-12-29|
    KR900700254A|1990-08-11|
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    法律状态:
    优先权:
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    PCT/JP1988/000536|WO1989011960A1|1988-06-01|1988-06-01|Method and apparatus for injection compression molding|
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