JP5087585B2 - Injection molding method and injection molding apparatus - Google Patents

Description

  The present invention relates to mold internal pressure control when a molten resin is injection-molded into a mold cavity by advancing an injection plunger or screw of an injection molding machine, and more particularly, by heating the mold before injection of the molding resin. The present invention relates to a molding method that facilitates the control of the internal pressure by improving the flow of resin, and an injection molding apparatus that can use this molding method.

  In the conventional injection molding method shown in Patent Document 1, when injection molding is performed using an injection molding machine, the amount of change in the mold pressure and the amount of change in the injection pressure during the steady filling process based on the speed waveform pattern When the ratio deviates from the predetermined range and falls below the reference fluctuation speed ratio, and during the mold pressure control process based on the pressure waveform pattern, when the mold pressure falls below a predetermined mold pressure lower limit value, Each of them is regarded as a detection abnormality of the mold pressure sensor, and the injection unit is stopped. By using this injection molding method, it is possible to reliably prevent an abnormal rise in the mold internal pressure with a simple configuration method, and to avoid troubles such as damage to the mold.

Japanese Patent No. 4127339 (FIG. 6)

  The mold pressure waveform control of the conventional example shown in Patent Document 1 is used for the purpose of preventing burrs at high-speed injection filling and stabilizing the weight. Usually, the mold temperature is low enough for cooling (for example, Therefore, the temperature of the resin decreases during injection filling. In the case of molding with a crystalline resin, the viscosity of the resin rapidly increases due to crystallization near the crystallization temperature due to cooling. In the case of resin molding that is amorphous and has a viscosity of 1 × 10 3 Pa · S or more, the pressure loss is large due to flow. When molding such a resin, if there is a thin part locally in the shape of the molded product, the solidification of the thin part proceeds more than the solidification of the other part, the resin flow decreases, etc. The pressure distribution inside the mold becomes non-uniform due to an increase in the thickness of the mold, which may cause variations in the thickness of the molded product and defects such as flow marks, unevenness, and welds on the surface. Therefore, the area of the pressure sensor with high reproducibility and capable of stable control is very narrow. Therefore, there is a problem that it takes a long time and a great amount of labor to find an appropriate position of the pressure sensor.

  The present invention is an injection molding method based on in-mold pressure control based on a pressure waveform pattern, and it is not necessary to select the position of a pressure sensor strictly, and injection with high reproducibility and stability without changing the configuration of a conventional mold. An object is to provide a molding method and apparatus.

With respect to the above problems, the present invention aims to solve the problems by the following means.
(1) injection molding method of the first means, which has a different thin portion of the wall thickness on one part of the mold cavity, at least one mold internal pressure sensor melt pressure capable of measuring within the mold cavity A mold having at least one temperature sensor capable of measuring the temperature in the vicinity of the cavity, an injection device that fills the mold with molten resin by advancement of an injection plunger or screw, and an in-mold pressure within a predetermined cavity An input device capable of inputting a value, and an injection pressure, which is a forward pressure of the injection plunger or screw, is controlled so that the pressure value measured by the mold internal pressure sensor becomes the mold pressure value input by the input device. Injection molding machine equipped with an injection pressure control device, and a mold capable of supplying a heating medium for heating the mold and a cooling medium for cooling the mold, respectively A heat cooling device, and a valve for switching between the heating medium and the cooling medium. The heating medium and the cooling medium are switched by the valve and supplied to a common flow path to operate the injection molding machine while controlling the mold temperature. In the injection molding method for manufacturing a molded product, the temperature of the mold is increased by heating the mold by starting the supply of the heating medium before the injection device injects the molten resin into the mold, and the vicinity of the cavity. When the temperature of the mold measured by the temperature sensor provided reaches a predetermined heating target temperature, or when the timer for starting the mold from the start of heating expires, the supply of the heating medium is terminated. The injection apparatus starts filling the molten resin into the mold during or after heating the mold, and performs filling while the temperature of the mold is maintained at the resin flow start temperature or higher. , In the filling step, the injection pressure of the injection plunger or screw is controlled so that the pressure in the mold measured by the in-mold pressure sensor becomes the in-mold pressure value set by the input device, and the filling step During or after filling, the temperature of the mold is lowered by starting the supply of the cooling medium, and the temperature of the mold measured by the temperature sensor provided in the vicinity of the cavity reaches a predetermined cooling target temperature. The supply of the cooling medium is ended at the time or when the timer for starting the cooling of the mold has expired.

  By maintaining the mold temperature at the time of injection filling of the resin at a high temperature by the injection molding method of the first means, the increase in the viscosity of the resin and the cooling and solidification can be delayed even in the thin wall portion, and the filling pressure propagation is kept good. Therefore, the in-mold pressure distribution can be made simple and uniform. Also, since the resin solidification speed during filling slows down, even if pressure propagation delays in the molten resin, which is a compressible fluid, and pressure detection for in-mold pressure feedback control is delayed, pressure feedback correction The control command can be issued before the resin solidifies.

(2) injection molding method of the second means, the injection molding method of above (1), in that the die, resin flow pressure of the thin portion is a mold having a thin portion such as to reduce Features.

(3) The injection molding method of the third means is characterized in that, in the injection molding method of (2), at least the temperature of the thin portion is maintained at a temperature equal to or higher than a resin flow start temperature during filling or until filling is completed. And

(4) The injection molding method of the fourth means is an injection device in which the forward movement of the injection plunger or screw uses an electric motor as a drive source in any one of the above-described injection molding methods (1) to (3). It is characterized by that.

(5) The injection molding method of the fifth means is characterized in that, in the injection molding method of (4), regenerative electric power generated when the electric motor is decelerated is supplied to the mold heating / cooling device.

(6) The sixth means of the injection molding method is the injection molding method according to any one of the above (1) to (5), wherein the mold internal pressure profile measured by the mold internal pressure sensor and the temperature provided in the vicinity of the cavity. The temperature profile of the mold measured by the sensor is displayed on the same screen on the display device, and the timing and amount of temperature rise when the mold temperature rises due to high temperature resin flowing into the mold due to resin injection filling. The validity of the molding conditions is evaluated by comparing with the change in the pressure inside the mold.
In particular, for the comparison, the measured in-mold pressure profile and the temperature profile of the mold may be overwritten on the same graph with the shared time axis as the horizontal axis and the respective values as the vertical axis. preferable.

(7) An injection molding method according to a seventh means is characterized in that, in the injection molding method according to any one of the above (1) to (6), the resin is a crystalline resin.
The crystalline resin rapidly increases in viscosity near the crystallization temperature when cooled and solidified, and cannot maintain a fluid state, and the pressure propagation property deteriorates rapidly. For this reason, by setting the temperature of the mold to a flow start temperature that is sufficiently higher than the crystallization temperature, the resin can be kept in a fluid state, and the pressure distribution in the mold can be maintained by maintaining good pressure propagation. Therefore, there is an advantage that the control target temperature value at the time of cooling can be easily selected.

(8) injection-molding method of the eighth means may have different thin portion of the wall thickness on one part of the mold cavity, at least one mold internal pressure sensor melt pressure capable of measuring within the mold cavity A mold having at least one temperature sensor capable of measuring the temperature in the vicinity of the cavity, an injection device that fills the mold with molten resin by advancement of an injection plunger or screw, and an in-mold pressure within a predetermined cavity An input device capable of inputting a value, and an injection pressure, which is a forward pressure of the injection plunger or screw, is controlled so that the pressure value measured by the mold internal pressure sensor becomes the mold pressure value input by the input device. Injection molding machine equipped with an injection pressure control device, and a mold capable of supplying a heating medium for heating the mold and a cooling medium for cooling the mold, respectively A heat cooling device, and a valve for switching between the heating medium and the cooling medium. The heating medium and the cooling medium are switched by the valve and supplied to a common flow path to operate the injection molding machine while controlling the mold temperature. In the injection molding method for manufacturing a molded product, the temperature of the mold is increased by heating the mold by starting the supply of the heating medium before the injection device injects the molten resin into the mold, and the vicinity of the cavity. The supply of the heating medium is terminated when the temperature of the mold measured by the temperature sensor provided reaches a predetermined heating target temperature and the timer for starting the mold from the start of heating expires, The injection device starts filling molten resin into the mold during or after the heating of the mold, and performs filling while the temperature of the mold is maintained at or above the resin flow start temperature, The filling In the process, the injection pressure of the injection plunger or the screw is controlled so that the pressure in the mold measured by the in-mold pressure sensor becomes the in-mold pressure value input by the input device. During or after filling, the temperature of the mold is lowered by starting the supply of the cooling medium, the temperature of the mold measured by the temperature sensor provided in the vicinity of the cavity reaches a predetermined cooling target temperature, and The supply of the cooling medium is terminated when the timer for starting the cooling of the mold expires.

(9) The injection molding method of the ninth means is the injection molding method according to any one of the above (1) to (8) , wherein the cooling medium supply start timing is the heating medium supply end time or heating. At least one of a time-up time of a timer that starts simultaneously with the end of the medium supply, a time when the injection plunger or screw reaches a predetermined position, and a time when the pressure at a predetermined position of the cavity reaches a predetermined pressure value One of them is selected as the start timing of the supply of the cooling medium.

(10) An injection molding apparatus according to a tenth means includes a mold having at least one mold pressure sensor capable of measuring a resin pressure in a mold cavity, and a temperature sensor capable of measuring a temperature in the vicinity of the cavity; An injection device that fills the mold with molten resin by advancing the injection plunger or screw, an input device that can input an in-mold pressure value in a predetermined cavity, and a pressure value measured by the in-mold pressure sensor is the input An injection molding machine comprising an injection pressure control device for controlling an injection pressure, which is a forward pressure of the injection plunger or screw, so as to obtain an in-mold pressure value input by the device, and further heating the mold A heating medium having a mold heating and cooling device capable of supplying a heating medium for cooling and a cooling medium for cooling the mold, and a valve for switching between the heating medium and the cooling medium The cooling medium is switched by the valve also comprises a control device for controlling the temperature of the feed to mold into a common flow path, the above (1) to the control device for implementing any one of the injection molding method (9) It is characterized by having.

The inventions according to claims 1 to 3, claims 8 to 9 , and claim 10 are molding methods of the first to third and eighth to ninth means, and a molding apparatus of the tenth means, Regardless of the thickness distribution of the molded product, the resin in the mold during filling can be kept in a molten state, so that the effective resin flow path is not narrowed by the growth of the skin layer (solidified layer of the molded product surface layer) by cooling, Since the resin pressure distribution in the mold becomes simple and a highly reproducible pressure distribution is obtained, the range of the appropriate mold pressure sensor position is widened, so that it is easy to determine the mounting position of the mold pressure sensor. This is particularly effective in a mold having locally a thin portion where the flow pressure loss increases. In addition, when multiple mold temperature sensors are provided, it is possible to confirm the presence or absence of temperature irregularities in the mold, such as the presence or absence of locations where the temperature does not reach the specified temperature, and the temperature at locations that affect the pressure loss of resin flow. In the case where the temperature is low, the heating process of the mold can be controlled based on the selection and the reference.

  The invention according to claim 4 and claim 5 is a molding method of the fourth and fifth means, and at the time of deceleration of the injection operation (advance operation of the injection screw) or plasticizing operation (rotation operation of the injection screw). Regenerative power is generated during deceleration, but since high reproducibility of the resin flow state in the mold can be obtained by controlling the in-mold pressure waveform, variations in the regenerative power from shot to shot can be suppressed. By supplying this regenerative power to the power used by the heating / cooling medium supply device that consumes a large amount of energy, the energy consumed for molding can be stably reduced.

  The invention according to claim 6 is the invention of the sixth means, wherein the in-mold pressure and the mold temperature are displayed in time series of the same molding process. Effective for evaluating the control temperature setting value and the selection of the injection process (injection speed or injection pressure) and the timing of switching between the heating process and cooling process of the mold, and is resistant to disturbances and mold heating It is easy to determine the set value that can reduce the energy and pressure filling energy and the position of the mold pressure sensor.

The invention according to claim 7 is the molding method of the seventh means, wherein the resin is crystallized due to a temperature drop, the crystalline resin in which the pressure propagation property is rapidly reduced, and the high viscosity having a large flow pressure loss. This is effective for amorphous resins. Furthermore, a high cycle molding process is possible by forcibly cooling the mold during or after filling. In addition, it is possible to switch the resin pressure before the resin is solidified by controlling the internal pressure of the mold so that the pressure is sufficiently propagated to the resin in the mold, and it is easy to perform feedback control of the internal pressure of the mold.

It is a schematic diagram of an injection molding apparatus provided with a hydraulic injection unit capable of performing a molding method according to an embodiment of the present invention, and a mold heating and cooling control circuit. FIG. 2 is a block diagram showing control elements of a mold temperature and mold internal pressure control device provided in the mold heating / cooling control circuit of FIG. 1. It is process drawing which shows the shaping | molding procedure of 1st Embodiment using the metal mold | die heating / cooling circuit of FIG. It is process drawing which shows the shaping | molding procedure of 2nd Embodiment using the metal mold | die heating / cooling circuit of FIG. It is a schematic diagram of an injection molding apparatus provided with an electric injection unit capable of performing a molding method according to an embodiment of the present invention, and a mold heating and cooling control circuit. It is process drawing which shows the shaping | molding procedure of 3rd Embodiment using the metal mold | die heating / cooling circuit of FIG. FIG. 3 is an example in which a mold temperature of one cycle and an in-mold pressure at the time of injection are displayed in the same time series on the display device provided in the block diagram showing the control elements of FIG. 2. It is the schematic diagram which showed the in-mold pressure distribution by the conventional metal mold | die. It is the schematic diagram which showed the detail of the A section in FIG. It is the schematic diagram which showed the pressure distribution in a type | mold by this invention. It is the schematic diagram which showed the detail of the B section in FIG. It is the schematic diagram which showed the mold internal pressure profile which each mold internal pressure sensor arrange | positioned in the different location in the conventional metal mold | die detected. It is the schematic diagram which showed the type | mold internal pressure profile which each type | mold internal pressure sensor arrange | positioned in a different location in this invention detected.

  Heating / cooling using an injection molding machine capable of controlling the heating / cooling of the mold, and molding while controlling the mold pressure to be substantially constant during the pressure-holding process after injection filling while heating and cooling the mold. Three types of temperature control methods when the medium circuit temperature control method and the mold internal pressure control method are used together will be described. In the mold illustrated in this embodiment, illustrations of mold opening / closing and mold clamping are omitted, and the configuration and operation method of the injection unit and the heating medium circuit will be described.

(First embodiment)
A first embodiment will be described with reference to the drawings. FIG. 1 is a schematic diagram of an injection molding apparatus equipped with a hydraulic injection unit capable of performing a molding method according to an embodiment of the present invention, and a mold heating / cooling control circuit, and FIG. 2 is provided in the mold heating / cooling control circuit of FIG. FIG. 3 is a process diagram showing a molding procedure of the first embodiment using the mold heating and cooling circuit of FIG. 1, and FIG. It is a schematic diagram of an injection molding apparatus equipped with an electric injection unit capable of performing a molding method according to an embodiment of the present invention, and a mold heating and cooling control circuit.

  In FIG. 1, an injection molding apparatus 1 includes a movable mold 2 and a fixed mold 3 for obtaining a molded product having a desired shape. The movable mold 2 is fixed to a movable plate (not shown) of the mold clamping device, and the fixed mold 3 is fixed to a fixed plate (not shown) of the mold clamping device. When a resin product is manufactured using the injection molding apparatus 1, a mold clamping cylinder (not shown) is operated, and the movable platen 2 and the fixed platen 3 are clamped. Thereby, the cavity 4 is formed by the movable mold 2 and the fixed mold 3.

  As shown in FIG. 1, an injection cylinder (heating cylinder) 6 included in a so-called inline screw type injection unit 5 is connected to the fixed mold 3. A molten resin can be injected and injected from the injection unit 5 through the gate G into the cavity 4 formed by the movable mold 2 and the fixed mold 3. The injection cylinder 6 is extended from the unit main body 7, and an injection screw 8 is disposed therein. A connecting shaft 9 is connected to the injection screw 8, and this connecting shaft 9 is connected to a rotating shaft of a screw rotating motor 10 disposed on the side (right side in the drawing) of the unit body 7. The screw rotation motor 10 is slidably attached to the unit body 7.

  A piston 11 is fixed to the connecting shaft 9, and the piston 11 is located in the cylinder 7a. A supply side and a return side of the cylinder 7a are connected to a servo valve 14 and a hydraulic pump 15 via a hydraulic pipe 12, respectively. Thus, if hydraulic oil is supplied from the hydraulic pump 15 to the cylinder 7 a via the servo valve 14 and the hydraulic pipe 12, the injection screw 8 can be moved forward or backward via the piston 11. Thus, the piston 11 and the cylinder 7a function as an injection hydraulic cylinder. A relief valve 16 is disposed between the servo valve 14 and the hydraulic pump 15.

  The hydraulic pipe 12 is provided with a pressure sensor 17 that detects the oil pressure for injection. The oil pressure detected by the pressure sensor 17 is proportional to the injection pressure Ph in the injection cylinder 6. Further, the injection unit 5 is provided with a screw movement amount sensor 18 for detecting the movement amount of the injection screw 8. The screw movement amount sensor 18 detects the movement amount of the injection screw 8 from the origin position electrically, magnetically, or optically via a detection object fixed to the connecting shaft 9.

  Further, the movable mold 2 is provided with a mold internal pressure sensor 19 for detecting the mold internal pressure PM of the molten resin in the cavity 4 in the vicinity of the gate G. That is, the flow path 2b whose one end communicates with the cavity 4 is formed in the movable mold 2, and the mold internal pressure sensor 19 detects the pressure of the molten resin flowing into the flow path 2b from the vicinity of the gate G as the mold internal pressure PM. The movable mold 2 is provided with an in-mold resin temperature sensor 28 for detecting the temperature T of the wall of the cavity 4. Reference numerals 2a and 3a denote pipe manifolds.

  The above-described control of the injection unit 5 is performed by the control device 20. As shown in FIG. 2, the control device 20 includes an input device 26, an output device 27, a mold internal pressure waveform pattern storage means 22, a reference data storage means 23 such as a set pressure and a set temperature, timers t1 to t4, and a CPU 21. The CPU 21 has a storage circuit for storing a program for control / arithmetic processing and various data at the time of control / arithmetic operation. The CPU 21 is connected to the screw rotation motor 10 and the servo valve 14 of the injection unit 5 via a power line and a signal line, respectively, and controls both according to a predetermined program. Similarly, a pressure sensor 17, a screw movement amount sensor 18, an in-mold pressure sensor 19, and an in-mold resin temperature sensor 28 are connected to the CPU 21 via signal lines. Each of the sensors 17 to 19 and 28 gives a signal indicating a detection value to the CPU 21.

  Next, the structure of the heating means and the cooling means of the movable mold 2 and the fixed mold 3 will be described with reference to the schematic diagram of the mold heating and cooling control circuit in FIG. A structure using a steam generator (steam generating means) 31 as means for heating the molds 2 and 3 and a cooling device (cooling water generating means) 41 as means for cooling the molds 2 and 3 did.

  The steam generator 31 is configured to suck up the heating water stored in the water storage tank 36 with a high-pressure pump 32 and push it into the pressure vessel of the main body of the steam generator 31 to heat the heating water and generate steam. The water storage tank 36 is a heating water supply / recovery tank. 29 is a liquid level meter, and when the liquid level falls below the set height range, a switching valve (not shown) connected to the water source is opened to supply water. Moreover, although the example which collect | recovers the steam for heating in the water storage tank 36 was shown in this Embodiment, you may open | release to the air | atmosphere, without collect | recovering steam.

  In FIG. 1, the water vapor generator 31 is shown as a device that generates water vapor by heat exchange with the heating medium, but in general, the water vapor generator 31 often uses a boiler. The water vapor generated in the water vapor generator 31 is switched to the switching valve 45 connected to the delivery pipe 35 to release the water vapor to the molds 2 and 3. T1 is a water vapor temperature detection sensor. The water vapor temperature detected by the temperature detection sensor T1 is compared with the water vapor set temperature stored in the control device 20 in the control device 20, and the switching valve 46 is opened and closed so that the heating medium is passed through the heater 31a to the set temperature. Is controlling.

  In FIG. 1, the heater 31 a of the water vapor generator 31 may be a heating means such as an electric resistance heater, an induction heater using a high frequency current, or a heat pump using adiabatic compression of an inert gas.

  The cooling device 41 sucks the cooling water stored in the cooling water tank 43 with the pump 42 and pushes it into the cooling device 41. The temperature of the cooling water is set to such a low temperature that the temperature of the molded product filled in the cavity 4 of the mold becomes equal to or lower than the solidification temperature of the material of the molded product. A switching valve 49 and a temperature detection sensor T2 are installed in the cooling water pipe 39. The switching valve 47 installed in the refrigerant pipe 48 is opened and closed, and the cooling medium is controlled to pass through the cooling device 41 so that the cooling water reaches the set temperature. In this embodiment, the cooling water cooling device adjusted to a predetermined temperature is provided on the cooling water supply side. Instead, a cooling device such as a cooling tower is provided on the cooling water recovery side, and the cooling water is set to the predetermined temperature. It can be used without adjustment. Reference numerals 34 and 37 denote discharge pipes, and 51 and 52 denote switching valves.

  In the control device 20, the timer 1 (t1) for setting the timing for stopping the supply of the heating medium for switching the water vapor and controlling the mold to be heated rapidly, and the timing for stopping the supply of the cooling water are set. A timer 2 (t2), a timer 3 (t3) that delays the start of the supply of the cooling medium from the stop of the supply of the heating medium, and a timer 4 (t4) that delays the start of the supply of the heating medium from the stop of the supply of the cooling medium are provided.

  Subsequently, an injection molding apparatus 120 including an electric injection unit capable of performing the above molding method will be described with reference to FIG. The injection molding apparatus 120 has almost the same configuration as the injection molding apparatus 1 of FIG. Therefore, the description of the same components is omitted except for those requiring additional description.

  The injection unit 30 of the injection molding apparatus 120 includes an injection cylinder 57 having a pair of arms 57a and 57a extending at right angles to both sides integral with the injection cylinder having the same configuration as the injection cylinder 6 of the injection molding apparatus 1, and an injection cylinder. The screw part has the same shape as the connecting shaft 9 of the injection molding apparatus 1 described above, does not have the piston 11, and is symmetrical to the injection screw 58 directly connected to the rotary drive motor 60 and the arms extending on both sides of the housing of the rotary drive motor 60. A ball that is directly connected to the moving arm member 62 that fixes the ball screw nuts 63 and 63 and a pair of motors 61 and 61 that are attached to the arms 57 a and 57 a of the injection cylinder 57, and is screwed into the ball screw nuts 63 and 63. The screw shafts 59 and 59 are configured.

  The injection cylinder 57 is heated by a heater (not shown), and the rotational drive motor 60 is rotationally driven to plasticize and melt the resin material fed into the injection cylinder 57, and the motors 61 and 61 are rotated to mold the molten resin into the mold. The procedure of feeding to the cavity 4 is the same as that of the above-described injection molding apparatus 1 except that the electric motors 61 and 61 are used instead of the oil cylinder 7a and the hydraulic piston 11 for injection filling.

  The injection unit 30 uses a power circuit 64 for heating a mold, which includes a power storage device 70 and an electric heating means 38, to generate regenerative electric power generated when the electric motor 61 is decelerated after the injection screw 58 is advanced during injection filling with molten resin. The control device 40 can regenerate through the circulation circuit 65 or through the circulation circuit 54 to the power circuit 66 that drives the cooling device 41 including the power storage device 56 and the electric heating means 55. (For example, Japanese Examined Patent Publication No. 64-4896)

  An injection molding method for manufacturing a resin product using the injection molding apparatus 1 will be described with reference to process diagrams showing molding procedures (s1 to s14) in FIG. First, a mold clamping device (not shown) is operated to clamp the movable mold 2 and the fixed mold 3 to form the cavity 4. A predetermined resin material is supplied into the injection cylinder 6.

s1: The switching valve 45, which is a heating medium supply valve, is opened to send water vapor to the molds 2 and 3.
s2: The mold is heated.
s3: The mold temperature TM is compared with a set temperature (set mold upper limit temperature) TS on the high temperature side of the mold. When TM <TS, the mold is continuously heated. When TM = TS, the process proceeds to the next step s4. . (The high temperature side set temperature TS of the mold is a temperature at which the resin filled in the mold cavity can maintain a molten state.)
s4: The switching valve 45, which is a heating medium supply valve, is closed to stop the supply of the heating medium.

s5: The hydraulic oil is sent to the cylinder 7a, the injection screw 8 is advanced, and the molten resin is injected and filled into the mold cavity 4 while mainly controlling the injection process by speed control.
s6: The hydraulic pressure of the hydraulic oil is increased and the process proceeds to the mold internal pressure control process.
s7: The mold internal pressure (resin pressure in the cavity) PM and the set mold internal pressure PS are compared. When PM <PS, the hydraulic oil pressure is increased, and from the moment when PM = PS, the injection pressure is controlled from the injection speed control. Switching to the control, injection is performed while controlling the injection pressure so as to follow a predetermined mold pressure profile, and the process proceeds to the next step s8.
s8: Filling with molten resin.
s9: Filling with molten resin is completed while maintaining the hydraulic pressure.

s10: The switching valve 49, which is a cooling medium supply valve, is opened to replace the heat medium in the pipe manifolds 2a and 3a in the mold with the cooling medium.
s11: The mold temperature TM is compared with the low temperature side set temperature (set mold lower limit temperature) TC of the mold, and when TM> TC, the mold is continuously cooled, and when TM = TC, the process proceeds to the next step s12. (The low temperature side set temperature TC of the mold is a temperature at which the resin filled in the mold cavity is solidified.)
s12: The switching valve 49, which is a cooling medium supply valve, is closed to stop the supply of the cooling medium.
s13: Allow to cool.
s14: When the molded product cools to a temperature at which it can be taken out, the mold is opened and the molded product is taken out.

  The CPU 21 of the control device 20 is provided with a display device 50. FIG. 7 shows an example in which the mold temperature of one molding cycle, the injection pressure at the time of injection, and the pressure inside the mold are displayed in the same time series. The upper part of FIG. 7 shows the molding process, the lower part displays the injection pressure Ph (injection hydraulic pressure), the mold pressure PM, and the screw position in accordance with the timing of the molding process, and the lower part displays the mold temperature TM. ing.

  In the diagram of the injection pressure Ph (injection hydraulic pressure) and the in-mold pressure PM in the figure, the steady filling process Ka starts t0 hours after the start of resin injection, and the injection screw 8 passes through the steady filling process Ka at a constant speed. After shifting to the mold internal pressure control process K2, the mold internal pressure control process K2 is terminated.

  When the mold temperature TM reaches the set mold lower limit temperature TC, which is the predetermined cooling lower limit temperature, the replacement of the mold heat medium and the cooling medium is started, and the mold temperature reaches the set mold upper limit temperature TS. When this is confirmed, injection of the next molding cycle is started. The injection of the next molding cycle may be started at an arbitrary timing by a timer or the like even before the mold temperature reaches the set mold upper limit temperature TS.

  The effect obtained by controlling the mold temperature and the injection pressure in cooperation as described above will be described with reference to FIGS. 8 and 9 show the flow and pressure states of the cavity step portion in the conventional molding. FIG. 12 shows a profile of in-mold pressure in conventional molding. The solid line is the profile of the mold pressure at the time of low pressure injection, and the two-dot broken line is the profile of the mold pressure at the time of high pressure injection. 10 and 11 show the flow and pressure states of the cavity step portion in the present invention. FIG. 13 shows a profile of the mold internal pressure in the present invention. The solid line is the profile of the mold pressure at the time of low pressure injection, and the two-dot broken line is the profile of the mold pressure at the time of high pressure injection.

  In FIGS. 8 and 9, since the mold temperature is usually a resin solidification temperature equal to or lower than the heat distortion temperature, a skin layer is generated during filling, the resin flowable region is narrowed, and a large pressure loss occurs particularly in a thin portion. And a region where the resin pressure is locally low is generated. On the other hand, for example, the mold internal pressure value detected by the mold internal pressure sensor 19a is the mold internal pressure sensor provided in the other part, for example, the mold internal pressure sensor 19b provided in the immediate vicinity of the gate, or the mold provided in a part away from the gate. Only a very small change in the mold internal pressure value occurs with respect to the mold internal pressure change degree detected by the internal pressure sensor 19c.

  For this reason, as shown in FIG. 12, when the injection pressure is controlled by the mold internal pressure value detected by the mold internal pressure sensor 19a, the mold internal pressure value such as the mold internal pressure sensor 19a is changed even if the target mold internal pressure value is greatly changed. The pressure value generated at a small and small amount of resin filling does not change as much as expected, resulting in poor filling and insufficient filling. In addition, finding the position of the in-mold pressure sensor where there is no defective filling or insufficient filling and no defective molding is required requires many trials and errors, resulting in poor work efficiency.

  FIG. 10 and FIG. 11 show that the mold temperature during injection filling is maintained at a temperature equal to or higher than the resin flow start temperature according to the present invention, so that no skin layer is generated and the resin flowable region covers the entire cavity width of the mold. Thus, the flow pressure loss of the resin is minimized, and the difference in the mold pressure can be made gentle. Therefore, the mold internal pressure value detected by the mold internal pressure sensor 19c in the thin portion is less different from the mold internal pressure values detected by the mold internal pressure sensors 19b and 19c in the other parts.

  Therefore, as shown in FIG. 13, if the injection pressure is controlled by the mold internal pressure value detected by the mold internal pressure sensor 19b and the target mold internal pressure value is changed, the thin portion provided with the mold internal pressure sensor 19a is expected as expected. Therefore, it is easy to find the position of the mold pressure sensor where there is no filling failure and insufficient filling, and no molding failure occurs. In addition, regardless of the position where the mold pressure sensor is provided, it is possible to easily select an appropriate mold pressure value with high controllability, and therefore, the position where the mold pressure sensor is installed can be selected in a short time.

(Second Embodiment)
As a second embodiment, a process diagram (FIG. 4) showing a molding procedure using the injection molding apparatus 1 of FIG. 1 or the injection molding apparatus 120 of FIG. 5 will be described. The molding method of the second embodiment is different from the molding method of the first embodiment described above in that the mold temperature comparison control step in step s3 is similarly performed in step s15 of timer 1 (t1). In this case, the mold temperature comparison and control process in the process s11 during mold cooling is replaced with the process s16 of the timer 2 (t2), and the order of the other processes is not changed.

  The injection molding method for manufacturing the resin product of the second embodiment using the injection molding apparatus 1 will be described according to the process chart showing the molding procedure (s1 to s16) in FIG. First, a mold clamping device (not shown) is operated to clamp the movable mold 2 and the fixed mold 3 to form the cavity 4. A predetermined resin material is supplied into the injection cylinder 6.

s1: The switching valve 45, which is a heating medium supply valve, is opened to send water vapor to the molds 2 and 3.
s2: The mold is heated.
s15: Count up of timer 1 (t1) s4: The switching valve 45, which is a heating medium supply valve, is closed, and the supply of the heat medium is stopped.

s5: The hydraulic oil is sent to the cylinder 7a, and the injection screw 8 is advanced to inject and fill the mold cavity 4 with the molten resin.
s6: The hydraulic pressure of the hydraulic oil is increased and the process proceeds to the mold internal pressure holding control process.
s7: The mold internal pressure (resin pressure in the cavity) PM and the set mold internal pressure PS are compared. When PM <PS, the hydraulic oil pressure is increased. When PM = PS, the hydraulic pressure is maintained, and the next step s8 Proceed to
s8: Filling with molten resin.
s9: Filling with molten resin is completed while maintaining the hydraulic pressure.

s10: The switching valve 49, which is a cooling medium supply valve, is opened to replace the heat medium in the pipe manifolds 2a and 3a in the mold with the cooling medium.
s16: Count up of timer 2 (t2) s12: The switching valve 49, which is a cooling medium supply valve, is closed to stop the supply of the cooling medium.
s13: Allow to cool.
s14: When the molded product cools to a temperature at which it can be taken out, the mold is opened and the molded product is taken out.

  When timer 2 (t2), which started counting when mold internal pressure control process K2 is started, starts to replace mold heat medium and cooling medium, and mold temperature starts to rise. At K3, timer 1 (t1) starts counting. When t1 is counted up, injection of the next molding cycle is started.

  Both the timer 1 (t1) and timer 2 (t2) can be adjusted for the start point and time. Adjust the set early and late in consideration of overshooting of mold temperature rise and fall. The optimal start point timing and time up point can be determined.

  The heating time or cooling time of the mold hardly changes with each molding cycle if the temperature of the heat medium or the cooling medium is the same as the supply speed. If the time of (t1) or timer 2 (t2) is set and set, even if the heating medium or the cooling medium is switched, it does not deviate from the molding conditions.

(Third embodiment)
A third embodiment will be described with reference to a process diagram (FIG. 6) showing a molding procedure using the injection molding apparatus 1 of FIG. 1 or the injection molding apparatus 120 of FIG. The molding method of the third embodiment is different from the molding method of the first embodiment described above in that s17 is between the heat medium supply valve closing in step s4 and the cooling medium supply valve opening in step s10. The process of timer 3 (t3) is inserted, and the process of timer 4 (t4) of s18 is inserted between the cooling medium supply stop of process s12 and the heating medium supply start of process s1. There is no change in other processes and order.

  An injection molding method for manufacturing a resin product using the injection molding apparatus 1 will be described with reference to process diagrams showing molding procedures (s1 to s14) in FIG. First, a mold clamping device (not shown) is operated to clamp the movable mold 2 and the fixed mold 3 to form the cavity 4. A predetermined resin material is supplied into the injection cylinder 6.

s1: The switching valve 45, which is a heating medium supply valve, is opened to send water vapor to the molds 2 and 3.
s2: The mold is heated.
s3: The mold temperature TM is compared with the high temperature side set temperature (set mold upper limit temperature) TS of the mold, and when TM <TS, the mold is continuously heated, and when TM = TS, the process proceeds to the next step s4. (The high temperature side set temperature TS of the mold is a temperature at which the resin filled in the mold cavity can maintain a molten state.)
s4: The switching valve 45, which is a heating medium supply valve, is closed to stop the supply of the heating medium.
s17: Timer 3 (t3) count start. When the timer 3 (t3) counts up, the process proceeds to step s10: start of cooling medium supply.

s5: The hydraulic oil is sent to the cylinder 7a, and the injection screw 8 is advanced to inject and fill the mold cavity 4 with the molten resin.
s6: The hydraulic pressure of the hydraulic oil is increased and the process proceeds to the mold internal pressure holding control process.
s7: The mold internal pressure (resin pressure in the cavity) PM and the set mold internal pressure PS are compared. When PM <PS, the hydraulic oil pressure is increased. When PM = PS, the hydraulic pressure is maintained, and the next step s8 Proceed to
s8: Filling with molten resin.
s9: Filling with molten resin is completed while maintaining the hydraulic pressure.

s10: The switching valve 49, which is a cooling medium supply valve, is opened to replace the heat medium in the pipe manifolds 2a and 3a in the mold with the cooling medium.
s18: Timer 4 (t4) starts counting. When the timer 4 (t4) counts up, the process proceeds to the heating medium supply start in step s1.
s11: The mold temperature TM is compared with the low temperature side set temperature (set mold lower limit temperature) TC of the mold, and when TM> TC, the mold is continuously cooled, and when TM = TC, the process proceeds to the next step s12. (The low temperature side set temperature TC of the mold is a temperature at which the resin filled in the mold cavity is solidified.)
s12: The switching valve 49, which is a cooling medium supply valve, is closed to stop the supply of the cooling medium.
s13: Allow to cool.
s14: When the molded product cools to a temperature at which it can be taken out, the mold is opened and the molded product is taken out.

  When the mold temperature TM reaches a predetermined low temperature side set temperature (set mold lower limit temperature) TC, or when the timer t4 that starts counting when the mold internal pressure control step K2 starts, counts up, Switching from cooling to heating, the timer t1 of the next cycle starts counting.

  When the temperature comparison control in the initial stage of the molding operation is unstable, the switching timing of the heating medium and the cooling medium may be a timing when two conditions of temperature and timer are satisfied.

  In order to properly select the timing for switching between the heating medium and the cooling medium in the embodiment, the selection of the process switching timing is visually confirmed by visually confirming the graph of the temperature and the mold pressure displayed on the display device 50. This makes it easy to select an appropriate heating medium and cooling medium switching timing.

  In the first to third embodiments, the cooling start timing is set to the completion of filling or the timer is counted up, but the cooling is started when the pressure at a predetermined position of the cavity reaches a predetermined pressure value. May be. If the predetermined position of the cavity is selected at a location that requires high appearance and high transferability, the pressure at the location that requires high appearance and high transferability during the injection process has reached the pressure value effective for transfer. Since cooling can be started after confirmation, reliable transferability can be obtained and it is effective for shortening the molding cycle.

  Furthermore, the cooling start may be started when the injection screw 8 or 58 reaches a predetermined position set in advance. After the mold internal pressure PM reaches the set mold internal pressure PS, the injection process is carried out by pressure control. Therefore, if the preset mold internal pressure PS is insufficient for filling, the injection screw 8 or 58 will move the cavity 4 into the cavity 4. You can't move forward before it fills up and you stop. In this state, when the control devices 20 and 40 determine completion of filling and start cooling, the resin in the cavity 4 is solidified with insufficient filling, and molding defects occur. On the other hand, if the injection screw 8 or 58 has reached the screw position where the preset cavity 4 can be sufficiently filled with the resin, it is necessary to start cooling. The resin is solidified, and the occurrence of molding defects can be prevented.

  Further, the cooling start is performed when the timer counts up at the same time when the heating medium supply ends or when the heating heat medium supply ends, when the pressure at a predetermined position of the cavity 4 reaches a predetermined pressure value, and injection At least one when the screw 8 or 58 reaches a predetermined position set in advance may be selected as the start timing of the cooling medium supply. Since any one or two of the timer, the pressure in the cavity, and the screw position, or all the conditions can be selected, the setting range of the molding conditions can be increased and the moldability can be improved. As a procedure for selecting the conditions, various methods such as satisfying all the selected conditions and satisfying one of the selected conditions are possible.

  Regarding the temperature control during the injection molding cycle of the present invention, the configuration of each part of the mold heating circuit and the molding procedure are not intended to be limited to those described above, and are allowed to be changed as appropriate. In addition to this, as long as it does not deviate from the intention of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

DESCRIPTION OF SYMBOLS 1,120 Injection molding apparatus 2 Movable mold 3 Fixed mold 4 Cavity 5, 30 Injection unit 6, 57 Injection cylinder 8, 58 Injection screw 10 Screw rotation motor 60 Rotation drive motor 14 Servo valve 17 Pressure sensor 20, 40 Control apparatus 21 CPU
31 Water Vapor Generator 41 Cooling Device
50 Display device

Claims (10)

Together with different thin portion of the wall thickness on one part of the mold cavity, at least one type pressure sensor capable of measuring the resin pressure in the mold cavity, a temperature sensor temperature allows measurement of the cavity near the least A single mold, an injection device that fills the mold with molten resin by advancing an injection plunger or a screw, an input device that can input a pressure value in a mold in a predetermined cavity, and the pressure sensor in the mold An injection molding machine comprising: an injection pressure control device that controls an injection pressure that is a forward pressure of the injection plunger or the screw so that the pressure value measured by the input device becomes the in-mold pressure value input by the input device; ,
A heating medium for heating the mold and a mold heating / cooling device capable of supplying a cooling medium for cooling the mold, respectively, and a valve for switching between the heating medium and the cooling medium are provided. In an injection molding method of manufacturing a molded product by operating the injection molding machine while controlling the temperature of a mold by switching a medium by the valve and supplying a common flow path,
Before the injection device injects the molten resin into the mold, the temperature of the mold is increased by starting the supply of the heating medium, and the mold is measured by the temperature sensor provided near the cavity. When the temperature of reaches the predetermined heating target temperature, or when the timer for starting the mold starts heating up, the supply of the heating medium is terminated,
On the other hand, while the mold is being heated or after the end of the heating, the injection device starts filling the molten resin into the mold, and the filling is performed while the temperature of the mold is maintained at the resin flow start temperature or higher. In the filling step, the injection pressure of the injection plunger or screw is controlled so that the pressure in the mold measured by the in-mold pressure sensor becomes the in-mold pressure value set by the input device, During or after filling in the filling step, the temperature of the mold is lowered by starting the supply of the cooling medium, and the temperature of the mold measured by the temperature sensor provided near the cavity is a predetermined cooling target temperature. The injection molding method is characterized in that the supply of the cooling medium is terminated when the temperature reaches the point of time or when the timer for starting the cooling of the mold expires. In the injection molding method according to claim 1,
2. The injection molding method according to claim 1, wherein the mold is a mold having a thin portion where a resin flow pressure is lowered as the thin portion. In the injection molding method according to claim 2,
An injection molding method characterized in that at least the temperature of the thin-walled portion is maintained at a temperature equal to or higher than the flow start temperature of the resin during filling or until completion of filling. In the injection molding method according to any one of claims 1 to 3,
An injection molding method wherein the forward movement of the injection plunger or screw is an injection device using an electric motor as a drive source. In the injection molding method according to claim 4,
An injection molding method, characterized in that regenerative electric power generated during deceleration of the electric motor is supplied to the mold heating / cooling device. In the injection molding method according to any one of claims 1 to 5,
The mold pressure profile measured by the mold pressure sensor and the mold temperature profile measured by the temperature sensor provided in the vicinity of the cavity are displayed on the same screen on a display device to evaluate the validity of the molding conditions. A featured injection molding method. In the injection molding method according to any one of claims 1 to 6,
An injection molding method, wherein the resin is a crystalline resin. Together with different thin portion of the wall thickness on one part of the mold cavity, at least one type pressure sensor capable of measuring the resin pressure in the mold cavity, a temperature sensor temperature allows measurement of the cavity near the least A single mold, an injection device that fills the mold with molten resin by advancing an injection plunger or a screw, an input device that can input a pressure value in a mold in a predetermined cavity, and the pressure sensor in the mold An injection molding machine comprising: an injection pressure control device that controls an injection pressure that is a forward pressure of the injection plunger or the screw so that the pressure value measured by the input device becomes the in-mold pressure value input by the input device; ,
A heating medium for heating the mold and a mold heating / cooling device capable of supplying a cooling medium for cooling the mold, respectively, and a valve for switching between the heating medium and the cooling medium are provided. In an injection molding method of manufacturing a molded product by operating the injection molding machine while controlling the temperature of a mold by switching a medium by the valve and supplying a common flow path,
Before the injection device injects the molten resin into the mold, the temperature of the mold is increased by starting the supply of the heating medium, and the mold is measured by the temperature sensor provided near the cavity. When the temperature reaches the predetermined heating target temperature and the timer that starts the mold from the start of heating times up, the supply of the heating medium is terminated,
On the other hand, while the mold is being heated or after the end of the heating, the injection device starts filling the molten resin into the mold, and the filling is performed while the temperature of the mold is maintained at the resin flow start temperature or higher. In the filling step, the injection pressure of the injection plunger or screw is controlled so that the pressure in the mold measured by the in-mold pressure sensor becomes the in-mold pressure value input by the input device, During or after filling in the filling step, the temperature of the mold is lowered by starting the supply of the cooling medium, and the temperature of the mold measured by the temperature sensor provided near the cavity is a predetermined cooling target temperature. And the supply of the cooling medium is terminated when the timer for starting the cooling of the mold has timed out. In the injection molding method according to any one of claims 1 to 8 ,
The cooling medium supply is started at the end of supply of the heating medium or when the timer that starts simultaneously with the end of supply of the heating medium is reached, when the injection plunger or screw reaches a predetermined position, An injection molding method characterized in that at least one of the points in time when the pressure at the position reaches a predetermined pressure value is selected as the start timing of the cooling medium supply. A mold internal pressure sensor capable of measuring the resin pressure in the mold cavity, a mold including at least one temperature sensor capable of measuring the temperature in the vicinity of the cavity, and a molten resin by an advance of an injection plunger or a screw in the mold An injection device that fills the mold, an input device that can input an in-mold pressure value in a predetermined cavity, and a pressure value measured by the in-mold pressure sensor to be an in-mold pressure value input by the input device An injection molding apparatus comprising an injection pressure control device that controls an injection pressure that is a forward pressure of the injection plunger or screw, and further a heating medium for heating the mold and a mold for cooling the mold A mold heating / cooling device capable of supplying a cooling medium and a valve for switching between the heating medium and the cooling medium are provided, and the heating medium and the cooling medium are switched by the valve. Also comprises a control device for controlling the temperature of the flow path supplying molds of passing,
Injection molding apparatus characterized by comprising a control device for carrying out injection molding method as claimed in any one of claims 1-9.

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