JP2020029055A - Injection molding machine - Google Patents

Abstract

To provide an injection molding machine capable of suppressing the occurrence of overcharging of a molding material.SOLUTION: An injection molding machine according to the present embodiment is provided with: an injection device for injecting a molding material by moving a screw in a barrel; a storage part for storing a first injection starting position of the screw when starting the injection; and a control part for determining whether to allow the injection device to inject the molding material on the basis of a comparison result between the stored first injection starting position and an actual screw position.SELECTED DRAWING: Figure 6

Description

  Embodiments according to the present invention relate to an injection molding machine.

  The injection molding machine forms a resin by pouring a molten resin into a cavity between a plurality of closed molds. The resin is injected by the screw moving in the barrel of the injection molding machine. Before the molding operation, when the molding operation is temporarily interrupted, or when the resin is changed, a purge operation for replacing the old resin remaining in the barrel with a new resin is performed. In the purging operation, molding conditions such as a screw moving distance (injection stroke) during injection may be temporarily changed. For example, in order to execute the purge operation efficiently, the injection stroke during the purge operation is set to a value larger than the injection stroke during the molding operation of the product.

  However, if the user forgets to reset the injection stroke and starts the product molding operation after the purge operation, a large amount of resin is injected with an injection stroke larger than the injection stroke during the product molding operation. There are cases. In this case, the mold may be damaged by overfilling of the resin.

JP 2007-210347 A

  An injection molding machine capable of suppressing occurrence of overfilling of a molding material.

  The injection molding machine according to the present embodiment includes an injection device that injects a molding material by moving a screw in a barrel, a storage unit that stores a first injection start position of the screw at the start of injection, and a stored second storage unit. (1) A control unit that determines whether or not to inject the molding material into the injection device based on a comparison result between the injection start position and the actual screw position.

FIG. 1 is a block diagram illustrating an example of a configuration of an injection molding machine according to a first embodiment. FIG. 4 is a diagram illustrating transfer of molding condition data between a storage unit and a control unit according to the first embodiment. FIG. 5 is a view showing an example of a screen display on a display unit in the alarm function according to the first embodiment. FIG. 3 is a schematic diagram illustrating an example of a screw position in a barrel according to the first embodiment. FIG. 4 is a schematic diagram illustrating an example of a screw position in a barrel according to the first embodiment when an allowable value is set. FIG. 4 is a flowchart showing an example of the operation of the injection molding machine according to the first embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment does not limit the present invention.

  The drawings are schematic or conceptual, and the proportions and the like of each part are not always the same as actual ones. In the specification and drawings, the same reference numerals are given to the same elements as those described above with respect to the already-explained drawings, and the detailed description will be appropriately omitted.

(1st Embodiment)
FIG. 1 is a block diagram illustrating an example of a configuration of the injection molding machine 1 according to the first embodiment. The injection molding machine 1 is a machine that can repeatedly execute a series of injection molding operations. For example, an operation of molding a molded product once is repeated as a cycle operation. The time for executing a series of cycle operations is called cycle time.

  The injection molding machine 1 includes a frame 2, a fixed platen 3, a moving platen 4, a tie bar 5, a mold clamping drive mechanism 6, an injection device 7, a control section 8, a push-out mechanism 9, a human machine machine, and the like. An interface 60, a storage unit 110, an injection pressure sensor S1, a screw position sensor S2, a nozzle position sensor S3, and a mold position sensor S4 are provided.

  The frame 2 is a base of the injection molding machine 1. The fixed platen 3 is fixed on the frame 2. A fixed die 11 as a first die is attached to the fixed platen 3. One end of the tie bar 5 is fixed to the fixed platen 3, and the other end is fixed to the support plate 10. The tie bar 5 extends from the fixed board 3 through the moving board 4 to the support board 10.

  The moving board 4 is mounted on a linear guide (not shown) provided on the frame 2. The moving platen 4 is guided by a tie bar 5 or a linear guide, and can move toward or away from the fixed platen 3. A movable mold 12 as a second mold is attached to the movable board 4. The movable mold 12 is opposed to the fixed mold 11, approaches the fixed mold 11 together with the movable platen 4, and is combined with the fixed mold 11. When the movable mold 12 and the fixed mold 11 are brought into contact with each other, a space corresponding to the product shape is formed between the movable mold 12 and the fixed mold 11.

  The mold clamping drive mechanism 6 includes a toggle mechanism 13 and a toggle mechanism drive unit 14. The toggle mechanism drive section 14 includes a mold clamping servomotor 21, a ball screw 22, and a transmission mechanism 23 for driving the toggle mechanism 13. The crosshead 15 is attached to the tip of the ball screw 22. The rotation of the ball screw 22 causes the crosshead 15 to approach the moving platen 4 or move away from the moving platen 4. The transmission mechanism 23 transmits the rotation of the mold clamping servomotor 21 to the ball screw 22 to move the crosshead 15.

  When the toggle mechanism drive section 14 moves the crosshead 15, the toggle mechanism 13 operates. For example, when the crosshead 15 moves toward the movable platen 4, the movable platen 4 moves toward the fixed platen 3, and the dies 11, 12 are clamped. Conversely, when the crosshead 15 moves away from the moving platen 4, the moving platen 4 moves away from the fixed platen 3, and the dies 11, 12 are opened.

  The extrusion mechanism 9 includes an extrusion servomotor 71, a ball screw 72, a transmission mechanism 73, and an extrusion pin 74 for removing the molded product from the movable mold 12. The tip of the push pin 74 penetrates the inner surface of the movable mold 12. As the ball screw 72 rotates, the extrusion pin 74 pushes out the product adhered to the inner surface of the movable mold 12. The transmission mechanism 73 transmits the rotation of the extrusion servomotor 71 to the ball screw 72, and the ball screw 72 rotates to move the extrusion pin 74 in the left-right direction in FIG.

  The injection device 7 includes a heating barrel (band heater) 41, a screw 42, a metering drive unit 43, and an injection drive unit 44. The heating barrel 41 includes a nozzle 41a for injecting a resin in a molten state into a cavity of a clamped mold. The heating barrel 41 stores the resin from the hopper 45 while heating and melting the resin, and injects the molten resin from a nozzle. The screw 42 is provided movably while rotating or not rotating inside the heating barrel 41. In the measuring step, the screw 42 rotates, and the amount of molten resin injected from the barrel 41 is measured and determined based on the amount of rotation (movement distance) of the screw 42. In the injection step, the screw 42 moves without rotating, and injects the molten resin from the nozzle.

  The measuring drive unit 43 includes a measuring servomotor 46 and a transmission mechanism 47 that transmits rotation of the measuring servomotor 46 to the screw 42. When the measuring servomotor 46 is driven and the screw 42 is rotated in the heating barrel 41, the resin is introduced from the hopper 45 into the heating barrel 41. The introduced resin is sent to the front end side of the heating barrel 41 while being heated and kneaded. The resin is melted and stored at the tip of the heating barrel 41. The molten resin is ejected from the barrel 41 by moving the screw 42 in a direction opposite to the time of the measurement. At this time, the screw 42 moves without rotating, and pushes out the molten resin from the nozzle. In this embodiment, a molten resin is used as a molding material. However, the molding material is not limited to the molten resin, and may be a metal, glass, rubber, a carbonized compound containing carbon fiber, or the like.

  The injection drive unit 44 has an injection servomotor 51, a ball screw 52, and a transmission mechanism 53. As the ball screw 52 rotates, the screw 42 moves in the heating barrel 41 in the left-right direction in FIG. The transmission mechanism 53 transmits the rotation of the injection servomotor 51 to the ball screw 52. Thus, when the injection servomotor 51 rotates, the screw 42 moves. The screw 42 pushes out the molten resin stored at the tip of the heating barrel 41 from the nozzle 41a, so that the molten resin is injected from the nozzle 41a.

  The injection pressure sensor S1 detects a filling pressure when filling the molten resin from the barrel 41 into the mold and a holding pressure in the pressure holding step. In the injection step, the injection pressure sensor S1 detects the injection pressure of the molten resin from the barrel 41 to the mold. In the dwelling step, the injection pressure sensor S1 detects the dwell pressure of the molten resin after the dwell pressure is switched from the speed control to the pressure control.

  The screw position sensor S2 detects the position of the screw 42. Since the screw 42 moves with the rotation of the injection servomotor 51, the screw position sensor S2 may detect the position of the screw 42 from the rotation speed or the angular position of the injection servomotor 51. By detecting the position of the screw 42 at every predetermined control cycle, the speed and acceleration of the screw 42 can be known.

  The nozzle position sensor S3 detects the position of the nozzle 41a provided at the tip of the barrel 41. The nozzle 41a can move in the left-right direction in FIG. 1 together with the injection device 7 by driving the servo motor 48. Therefore, the nozzle position sensor S3 detects the position of the injection device 7 to detect the position of the nozzle 41a. The nozzle position sensor S3 is, for example, a limit sensor. In this case, the nozzle position sensor S3 detects that the injection device 7 has advanced in the direction of the molds 11 and 12 and has reached the limit position (forward limit). The nozzle 41 a is in contact with the fixed mold 11 in the forward limit of the injection device 7.

  The mold position sensor S4 detects the position of the movable mold 12.

  The human machine interface (HMI / F) 60 displays various information on the injection molding machine 1. The HMI / F 60 may include, for example, the display unit 100 and a keyboard, or may be a touch panel display. The user can input settings such as commands related to the operation of the injection molding machine 1 through the HMI / F 60. For example, in injection molding, a product is formed by an injection step of injecting a molten resin into a mold and a pressure-holding step of controlling a pressure for holding the molten resin in the mold.

  The control unit 8 monitors sensor information received from various sensors (not shown) during the injection process, and controls the injection device 7 based on the sensor information. For example, the control unit 8 outputs an injection disable signal or an injection permission signal for instructing prohibition or permission of resin injection to the injection device 7 based on an injection start determination described later. When the injection disable signal rises, the control unit 8 prohibits the injection of the resin. On the other hand, when the injection permission signal rises, the control unit 8 permits resin injection. The ejection impossible signal and the ejection permission signal are complementary digital signals, and both do not rise. Further, the control unit 8 controls the screw 42 according to the set value set through the HMI / F 60. Further, the control unit 8 causes the display unit 100 to display necessary data.

  The storage unit 110 stores a plurality of pieces of operation information of the injection molding machine 1. The operation information is information indicating the operation of the molds 11 and 12, the mold clamping drive mechanism 6, or the injection device 7. The operation information includes molding conditions described later. Therefore, the storage unit 110 stores the molding conditions. The storage unit 110 may be outside the injection molding machine 1 or inside the injection molding machine 1.

  FIG. 2 is a diagram showing transfer of molding condition data between the storage unit 110 and the control unit 8 according to the first embodiment. The storage unit 110 stores molding conditions for each die. The molding conditions include, for example, the temperature of each part of the barrel 41, the injection speed, the injection start position, the pressure holding switching position, the pressure holding pressure, the purge conditions, and the like. The injection start position is the position of the screw 42 at the start of injection. Note that the injection start position is also the position of the screw 42 when the measuring step before the injection step is completed. The pressure holding switching position is the position of the screw 42 when switching from the injection process to the pressure holding process, and is also the position of the screw 42 when the injection is completed (the injection completion position). Note that the moving distance of the screw 42 from the injection start position to the pressure holding switching position is called an injection stroke.

  For example, as shown in FIG. 2, the control unit 8 reads the molding conditions of the mold A1234 from the storage unit 110. The read molding conditions are stored in a storage area in the control unit 8 as variable values and stored values.

  The variable value of the molding condition is a value that can be changed by the user through the HMI / F 60 as an input unit. At the beginning of reading from the storage unit 110, the variable values and the stored values of the molding conditions are the conditions stored in the storage unit 110, and are the same values. However, if the variable value is changed by a user input, the variable value has priority over the stored value. Therefore, the resin is injected according to the changed variable value of the molding condition. Thus, the user can optimize the molding conditions for each mold by injecting the resin while finely adjusting the variable values of the molding conditions. For example, if the type of resin changes, it is necessary to optimize the molding conditions. In such a case, the user can change the variable value from the stored value to optimize the molding conditions.

  On the other hand, the stored value of the molding condition does not accept a change from the user. When the molding condition is read from the storage unit 110 to the control unit 8, the read molding condition is stored as a stored value of the molding condition. When the variable value of the molding condition is stored in the storage unit 110, the variable value of the molding condition is stored as a stored value of the molding condition. Therefore, the stored values of the molding conditions of the mold A1234 are the same as the molding conditions of the corresponding mold A1234 stored in the storage unit 110.

  In some cases, the user performs a purge operation using molding conditions used for a normal molding operation. The purging operation is to replace the old resin (for example, deteriorated resin) in the barrel 41 with a new resin, or with another kind of resin. The purge operation is performed before the molding operation, when the molding operation is temporarily stopped, or when the resin is changed. In the purge operation, metering and injection of a new resin are repeated. At this time, the resin is injected in a state where the nozzle 41a and the fixed die 11 are separated so that the injected resin does not enter the dies 11 and 12. In such a purge operation, a user may temporarily change a variable value of molding conditions used for a normal molding operation and use it as a condition of the purge operation.

  For example, assume that the variable values in FIG. 2 are applied to the purge operation. In this case, the user has changed the stored value of the injection start position from, for example, 50 mm to 80 mm for the purge operation. In the purge operation, the variable value of the injection start position may be changed so that the injection stroke becomes larger than in the case of molding the product. This is to perform the purging operation efficiently in a short time. After the purge operation, the variable value of the injection start position is returned to the stored value (for example, 80 mm to 50 mm), and the product is formed. If the user forgets to return to the optimized injection start position and performs molding of the product with a large injection stroke, overfilling may occur. In this case, the mold may be damaged.

  Therefore, the control unit 8 performs an injection start determination before starting the injection, and determines whether to cause the injection device 7 to inject the resin based on the determination result. Accordingly, when there is a possibility that overfilling will occur, it is possible to prevent the injection of the resin from being started and suppress occurrence of overfilling.

  Next, a method of determining the start of injection will be described.

  FIG. 3 is a diagram illustrating a screen display example of the display unit 100 in the alarm function according to the first embodiment. FIGS. 4A to 5 are diagrams illustrating the determination of the injection start position. FIG. 6 is a flowchart showing an example of the operation of the injection molding machine 1 according to the first embodiment. The method for determining the start of injection according to the present embodiment will be described with reference to the flowchart of FIG. 6 and FIGS. 3 to 5. FIGS. 3 to 6 show a method of determining whether or not to start injection when starting a normal molding operation after the purge operation of the injection molding machine is completed.

  First, the control unit 8 acquires the stored value A of the injection start position from the storage unit 110 (S10 in FIG. 6). At this time, the variable value remains the setting of the purge operation, and may be different from the acquired stored value A.

  Next, the control unit 8 determines whether or not injection is disabled (S20). The determination of the injection disable setting will be described with reference to FIG. The non-injection setting is a setting for preventing the resin from being injected when there is a possibility that overfilling will occur, and is set to be valid or invalid according to the user's selection.

  FIG. 3 is a diagram illustrating a screen display example of the display unit 100 in the alarm function according to the first embodiment. The alarm function includes determination of the injection disable setting and determination of the injection start position. The determination of the injection start position will be described later in detail with reference to FIGS.

  “Valid” displayed on the operation button 61 shown in FIG. 3 can be switched to “invalid” by the user through the HMI / F 60. The display of the operation button 61 enables or disables the injection disable setting. That is, whether or not to inject the resin when there is a possibility of overfilling is selected by the user. As shown in FIG. 6, the control unit 8 determines whether the injection disable setting is valid (S20). If the injection prohibition setting is invalid (NO in S20), the control unit 8 outputs an injection permission signal to the injection device 7 without performing the determination after step S30 (S80). On the other hand, when the injection prohibition setting is valid (YES in S20), the control unit 8 executes the determination after step S30.

  Next, the control unit 8 acquires the actual position B and the allowable value C of the screw 42 (S30). The actual position B and the allowable value C of the screw 42 are used for determining an injection start position described later. Next, the control unit 8 determines the injection start position (S40). The determination of the injection start position together with the actual position B and the allowable value C of the screw 42 will be described with reference to FIGS.

  FIGS. 4A and 4B are schematic diagrams illustrating an example of the position of the screw 42 in the barrel 41 according to the first embodiment. The horizontal axis in FIGS. 4A and 4B indicates the position of the screw 42. The reference position where the position of the screw 42 is 0 mm is, for example, the tip of the barrel 41. A shown in FIGS. 4A and 4B is a stored value of the injection start position (first injection start position). As shown in FIG. 2, the stored value A of the injection start position is set to, for example, 50 mm. B shown in FIGS. 4A and 4B is the actual position of the screw 42. The actual position B of the screw 42 is the position of the screw 42 detected by the screw position sensor S2. D shown in FIGS. 4A and 4B is a pressure-holding switching position. As shown in FIG. 2, the pressure holding switching position D is set to, for example, 10 mm. AD shown in FIGS. 4A and 4B is a second distance from the stored value A of the injection start position to the pressure holding switching position D. 4A and 4B is a first distance from the actual position B of the screw 42 to the pressure holding switching position D.

  FIG. 4A shows a case where the actual position B of the screw 42 is farther from the pressure holding switching position D than the stored value A of the injection start position. FIG. 4B shows a case where the actual position B of the screw 42 is the same as the stored value A of the injection start position.

  In the purging operation, first, the resin is injected from a state where the resin is measured. In this case, the resin is injected by moving the screw 42 to the pressure holding switching position D shown in FIG. After the injection, the resin is measured by retreating to a variable value of the injection start position while the screw 42 rotates. The screw 42 moves to the temporarily changed injection start position variable value (for example, 80 mm) shown in FIG. Therefore, as shown in FIG. 4A, the actual position B of the screw 42 at the time of completion of the measurement is, for example, 80 mm. When the resin is injected again, the resin is measured and the actual position B of the screw 42 becomes, for example, 80 mm. In this way, one cycle of the purge operation is from the start of the injection to the completion of the metering until the screw 42 is positioned at the variable value of the injection start position. This cycle of the purge operation is repeated until the resin in the barrel 41 is replaced with new resin. Here, one cycle of the purge operation is completed by moving the screw 42 to a position corresponding to the variable value of the injection start position. Therefore, at the end of the purge operation, the actual position B of the screw 42 becomes a position corresponding to the variable value of the injection start position. Therefore, the stored value A read at the start of the normal molding operation may be different from the actual position B. Further, at the end of the purge operation, since the measurement has been completed, the resin is stored at the tip of the barrel 41.

  In step S30, before the product is formed, the control unit 8 acquires the actual position B of the screw 42 from the screw position sensor S2 shown in FIG. At this time, the actual position B of the screw 42 is a position corresponding to the variable value of the injection start position, and may be different from the stored value A. For example, in the example of FIG. 2, the actual position B of the screw 42 is 80 mm at the end of the purge operation. The control unit 8 compares the stored value A (for example, 50 mm) of the injection start position with the actual position B (for example, 80 mm) of the screw 42. The control unit 8 determines, for example, whether the first distance BD is longer than the second distance AD (AD <BD) (S40).

  In the case shown in FIG. 4A, the control unit 8 determines that the first distance BD is longer than the second distance AD (YES in S40). In this case, the first distance BD is longer than the second distance AD only in the shaded region from the stored value A of the injection start position to the actual position B of the screw 42. Therefore, a large amount of resin is injected into the cavity with an injection stroke longer than the optimized injection stroke at the time of molding the product, and overfilling may occur. In this case, the control unit 8 proceeds to step S50.

  On the other hand, when the first distance BD is equal to or less than the second distance AD (NO in S40), the control unit 8 outputs the injection permission signal to the injection device 7 without performing the determination in step S50 and thereafter (S80).

  When the purge operation is completed, the measurement of the resin in the barrel 41 has been completed, and the screw 42 is located at, for example, 80 mm. In order to prevent overfilling, it is necessary to adjust the amount of resin in the barrel 41 before molding the product. When the variable value of the injection start position is returned to the stored value (for example, 50 mm) of the injection start position and the purge operation is performed again, the actual position B of the screw 42 becomes, as shown in FIG. Return to the stored value of the injection start position (for example, 50 mm). In this case, since the first distance BD is equal to or less than the second distance AD (BD ≦ AD), overfill does not occur. As described above, the purge operation is performed again to return the actual position B of the screw 42 at the time of the completion of the measurement to the stored value A after the purge operation. This suppresses the occurrence of overfilling in the molding of the product after the purging operation again. Also in this case, since the first distance BD is equal to or less than the second distance AD (NO in S40), the control unit 8 outputs the injection permission signal to the injection device 7 without performing the determination after step S50 (S80). .

  Here, the determination of the injection start position in consideration of the allowable value C (S40) will be described.

  FIG. 5 is a schematic diagram illustrating an example of the position of the screw 42 in the barrel 41 according to the first embodiment when the allowable value C is set. The allowable value C is an allowable value (upper limit) of a difference between the stored value A of the injection start position and the actual position B of the screw 42. Since it is difficult to control the position of the screw 42 with high precision, the control unit 8 determines that there is actually no difference between the stored value A and the actual position B even though there is no difference. In some cases. Therefore, the allowable value C can be set, and if the difference between the stored value A and the actual position B is less than the allowable value C, even if the actual position B is larger than the stored value A, the control unit 8 Allows injection.

  The allowable value C is displayed on the display unit 100 together with the stored value A of the injection start position, as shown in FIG. 3 is changed to an arbitrary value by the user through the HMI / F60. ACD shown in FIG. 5 is a correction distance from the correction position A + C obtained by adding the allowable value C to the storage value A of the injection start position to the pressure holding switching position D.

  As shown in FIG. 5, the actual position B of the screw 42 is, for example, 52 mm with respect to the stored value A (for example, 50 mm) of the injection start position. In this case, the first distance BD is longer than the second distance AD (AD <BD). However, even if the injection stroke is extended by the distance of the error due to the position control of the screw 42, there is a case where there is almost no effect on overfilling. Therefore, the allowable value C is set in a range where the influence on overfilling is small even if the injection stroke is extended. The allowable value C is set, for example, in a range of 0.1 to 9.99 mm.

  In step S30 of FIG. 6, before molding the product, the control unit 8 also acquires the allowable value C set through the HMI / F60. As shown in FIG. 3, for example, the stored value A of the injection start position is 50 mm, and the allowable value C is 4 mm. This indicates that the effect on overfilling is small even if the injection stroke is extended by 4 mm. The control unit 8 compares the correction position A + C (for example, 50 + 4 = 54 mm) with the actual position B of the screw 42 (for example, 52 mm). The control unit 8 determines, for example, whether the first distance BD is longer than the correction distance ACD (ACD <BD) (S40). As shown in FIG. 5, when the actual position B is equal to or less than 54 mm, the control unit 8 determines that the first distance BD is equal to or less than the correction distance ACD (BD ≦ ACD) (NO in S40). In this case, it is the same as when no overfilling occurs. Therefore, the control unit 8 outputs an injection permission signal to the injection device 7 (S80). Accordingly, it is possible to prevent the resin from being injected due to an erroneous determination based on an error in the position control of the screw 42 despite the low possibility of occurrence of overfilling. On the other hand, when the first distance BD is longer than the correction distance ACD (ACD <BD) (YES in S40), overfilling may occur. In this case, the control unit 8 executes step S50. As described above, the injection start position may be determined in consideration of the allowable value C.

  When the first distance BD is equal to or less than the second distance AD (BD ≦ AD) due to an error in the position control of the screw 42, overfilling does not occur without considering the allowable value C.

  Next, the control unit 8 determines the nozzle touch state (S50). The determination of the nozzle touch state will be described. The nozzle touch state is a state in which the nozzle 41a shown in FIG.

  In the determination of the nozzle touch state, the control unit 8 detects whether the nozzle 41a is in the nozzle touch state (S50). When the nozzle 41a is not in the nozzle touch state (NO in S50), the resin does not flow into the dies 11, 12 or the cavity, so that overfilling does not occur. In this case, the control unit 8 outputs the injection permission signal without performing the determination after step S60 (S80). On the other hand, when the nozzle 41a is in the nozzle touch state (YES in S50), the resin injected from the nozzle 41a flows into the dies 11, 12. YES is determined in step S40, and the first distance BD is longer than the second distance AD or the correction distance ACD. Therefore, a large amount of resin may be injected and overfilling may occur. In this case, the control unit 8 executes step S60.

  The nozzle position sensor S3 shown in FIG. 1 detects that the nozzle 41a is in contact with the fixed mold 11, and outputs a detection signal to the control unit 8, as described above. The controller 8 may determine whether the nozzle 41a is in contact with the fixed mold 11 based on the detection signal received from the nozzle position sensor S3.

  Next, the control unit 8 determines the mold closed state (S60). The determination of the mold closed state will be described. The mold closed state is a state in which the fixed mold 11 and the movable mold 12 are in contact with each other and the molds 11 and 12 are closed.

  The control unit 8 detects whether or not the molds 11 and 12 are in the mold closed state (S60). When the molds 11 and 12 are not in the mold closed state (NO in S60), even if the resin flows into the cavity, the resin is discharged out of the cavity. Therefore, no overfilling occurs. In this case, the control unit 8 outputs an injection permission signal to the injection device 7 (S80). On the other hand, when the molds 11 and 12 are in the mold closed state (YES in S60), the resin that has flowed into the cavity remains in the cavity without being discharged. YES is determined in step S40, and the first distance BD is longer than the second distance AD or the correction distance ACD. Therefore, a large amount of resin may be injected and overfilling may occur. In this case, the control unit 8 outputs an injection disable signal to the injection device 7 (S70).

  Note that the mold position sensor S4 shown in FIG. 1 detects the position of the movable mold 12 and outputs a detection signal to the control unit 8 as described above. The control unit 8 may determine whether or not the dies 11, 12 are in the mold closed state based on the position of the movable mold 12 received from the mold position sensor S4.

  As shown in FIG. 6, when the injection disable signal is output (S70), the control unit 8 executes steps S20 to S70 again. The loop of steps S20 to S70 is repeatedly executed until the result of any of steps S20 and S40 to S60 becomes NO, or until a predetermined time has elapsed. The determinations in steps S20, S30 to S40, S50, and S60 may be performed in an order different from the order shown in FIG. 6, or may be performed simultaneously.

  In the above four determinations, for example, when the first distance BD is longer than the correction distance ACD (ACD <BD), the nozzle 41a is in the nozzle touch state, and the dies 11, 12 are in the mold closed state. (When steps S40 to S60 are YES), a large amount of resin is not discharged out of the cavity but stays in the cavity. Therefore, overfilling occurs. In this case, if the injection impossible setting is valid (YES in S20), the control unit 8 outputs an injection impossible signal (S70). Upon receiving the injection disable signal, the injection device 7 stops the injection of the resin until receiving the injection permission signal. Thereby, it is possible to suppress occurrence of overfilling without injection of the resin.

  Further, even when the injection disable signal is output (YES in S20), after the variable value of the injection start position is changed and the purge operation is performed again, the first distance BD is equal to or less than the correction distance ACD. In this case (BD ≦ ACD) (NO in S40), when the nozzle is not in the touch state (NO in S50), and when the mold is not in the closed state (NO in S60), overfilling does not occur. Therefore, the control unit 8 outputs an injection permission signal to the injection device 7. In this case, the injection device 7 starts the injection of the resin, and the molding of the product is performed.

  When the injection disable setting is set to invalid (NO in S20), the control unit 8 outputs the injection permission signal to the injection device 7 without performing the determination in steps S40 to S60. In this case, the injection device 7 starts injection of the resin.

  Further, when the purging operation is performed, the nozzle 41a is not in the nozzle touch state (NO in S50), so that overfill does not occur. Therefore, when the purge operation is performed, an injection permission signal is output, and the resin is injected. In the purging operation, an in-mold purging operation may be performed. The in-mold purge operation is a purge operation for replacing the resin in the resin flow path in the fixed mold 11. In the in-mold purging operation, the nozzle 41a is in the nozzle touch state, and the dies 11, 12 are in the mold closed state, but the injection stroke is set short. That is, since the first distance BD is equal to or less than the correction distance ACD (BD ≦ ACD) (NO in S40), overfill does not occur. Therefore, when the in-mold purging operation is performed, the injection permission signal is output, and the resin is injected.

  In some cases, the in-mold purging operation is performed in a state where the molds 11 and 12 are not in contact with each other. In this case, since the molds 11 and 12 are open (NO in S60), overfilling does not occur. Therefore, an injection permission signal is output, and the resin is injected.

  As described above, the injection start determination flow in FIG. 6 can be applied not only to the start of the normal molding operation but also to the purge operation.

  As described above, the injection molding machine 1 according to the first embodiment can stop the injection of the resin when overfilling occurs, and at the time of molding and purging the product when overfilling does not occur. Can be injected.

  When outputting a non-ejection signal to the injection device 7, the control unit 8 may output an alarm signal to the display unit 100. In this case, when receiving the alarm signal, the display unit 100 displays that the injection device 7 has stopped the injection of the resin by the injection disable signal. The display unit 100 may emit an alarm sound. Thereby, the user can know that the injection device 7 has stopped the injection of the resin by the injection disable signal.

  As described above, the injection molding machine 1 according to the first embodiment determines whether or not to inject the resin into the injection device 7 based on the comparison result between the stored value A of the injection start position and the actual position B of the screw 42. A control unit 8 for determining is provided. Thereby, even if the user forgets to change the molding conditions before molding the product, it is possible to suppress occurrence of overfilling of the resin. As a result, damage to the molds 11 and 12 due to high pressure of the resin in the cavity can be suppressed. In addition, it is possible to suppress the occurrence of burrs due to overfilling. Burrs are molding defects that occur when the pressure of the resin in the cavity increases and the contact surfaces of the dies 11 and 12 are opened, and the resin that does not fit can leak out of the contact surfaces and solidify.

  In some molding conditions, an injection start position used for a normal molding operation and an injection start position used for a purge operation can be separately set. In this case, when the purge operation is set, the user may erroneously change the injection start position of the normal molding operation. In this case, if the process directly proceeds to the normal molding operation after the purging operation, the mold may be overfilled.

  On the other hand, in the injection molding machine 1 according to the first embodiment, even when the injection start position used for the normal molding operation and the injection start position used for the purge operation can be set separately. If the present embodiment is applied to a variable value of the injection start position used for a normal molding operation, overfilling of the mold can be suppressed.

  Further, the molding and purging operations of the product can be executed by changing the variable value of one injection start position. Therefore, the injection molding machine 1 according to the first embodiment can prevent the user from making an erroneous operation and can suppress the occurrence of overfilling.

  In determining the injection start position, the injection start position stored in the storage unit 110 may be directly used instead of the storage value A of the injection start position. This is because the stored value of the molding condition is the same as the molding condition stored in the storage unit 110 as described above. In this case, when determining the injection start position, the control unit 8 reads the molding condition file stored in the storage unit 110. The molding condition file stored in the storage unit 110 is read in association with, for example, a file name or a mold name in variable values of molding conditions. However, when the stored value A of the injection start position is used, the injection start position can be determined at higher speed.

  Further, the stored value of the molding condition is not directly changed by the user. However, in a case where the condition stored in the storage unit 110 can be updated with a variable value of the molding condition, the stored value can be indirectly changed by the variable value.

(Modification)
In the modified example of the first embodiment, the control unit 8 determines the injection start position using the variable value B (second injection start position) of the injection start position instead of the actual position B of the screw 42. . The modified example is different from the first embodiment in this point. The actual position of the screw 42 is controlled to be at the variable B of the injection start position when the purge operation is completed. Therefore, the variable value B of the injection start position can be used instead of the actual position of the screw 42.

  The control unit 8 compares the correction position A + C with the variable value B of the injection start position. For example, the control unit 8 determines whether the first distance BD from the injection start position variable value B to the pressure holding switching position D is longer than the correction distance ACD (ACD <BD).

  Other configurations and operations of the injection molding machine 1 according to the modified example are the same as the corresponding configurations and operations of the injection molding machine 1 according to the first embodiment, and thus detailed description thereof will be omitted.

  In the first embodiment, the actual position of the screw 42 is used for determining the injection start position. Therefore, before the product is formed, the purging operation is again performed to position the actual position of the screw 42 at the storage value A. However, in the variant, the actual position of the screw 42 is not taken into account. Therefore, even when the actual position of the screw 42 is located at B shown in FIG. 4A, if the variable value of the injection start position is changed to the value of the stored value, the first distance BD becomes the second distance AD or the correction distance. It becomes equal to or less than the ACD (NO in S40). In this case, if the resin is injected without performing the purge operation again, overfilling occurs. Therefore, in the modified example, as in the first embodiment, it is necessary to perform the purge operation again after the purge operation and before the molding of the product. Thus, the determination of the injection start position according to the present modification is performed in the same manner as the determination of the injection start position according to the first embodiment.

  Similar to the injection molding machine 1 according to the first embodiment, the injection molding machine 1 according to the modified example can suppress occurrence of overfilling of the resin even if the user forgets to change the molding conditions before molding the product. . Further, without using the actual position of the screw 42, the injection start position can be determined more easily by using the variable value B of the injection start position which is the set value.

  Further, in this modification, since the set values of the injection start positions are compared with each other, it is not necessary to consider an error in the position control of the screw 42. In this case, the control unit 8 compares the stored value A of the injection start position with the variable value B of the injection start position. The control unit 8 determines, for example, whether the first distance BD is longer than the second distance AD (AD <BD). This makes it possible to more easily determine the injection start position.

  Although several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and equivalents thereof.

Reference Signs List 1 injection molding machine, 7 injection device, 8 control unit, 11 fixed mold, 12 moving mold, 41 barrel, 41a nozzle, 42 screw, 60 HMI / F, 100 display unit, 110 storage unit, S2 screw position sensor, S3 Nozzle position sensor, S4 Mold position sensor, A Stored value of injection start position, B actual position, C tolerance, D holding pressure switching position, AD second distance, ACD correction distance, BD first distance

Claims (10)

An injection device for injecting a molding material by moving a screw in a barrel,
A storage unit for storing a first injection start position of the screw at the start of injection,
An injection molding machine comprising: a control unit that determines whether or not to inject the molding material into the injection device based on a comparison result between the stored first injection start position and an actual position of the screw.   The injection device may further include, when a first distance from an actual position of the screw to an injection completion position of the screw at the time of completion of injection is equal to or less than a second distance from the first injection start position to the injection completion position. The injection molding machine according to claim 1, wherein the molding material is injected, and the molding material is not injected when the first distance is longer than the second distance. An injection device for injecting a molding material by moving a screw in a barrel,
A storage unit for storing a first injection start position of the screw at the start of injection,
An input unit for inputting a second injection start position of the screw at the start of injection,
A control unit for determining whether or not to inject the molding material into the injection device based on a comparison result between the stored first injection start position and the input second injection start position. Machine.   When the first distance from the second injection start position to the injection completion position of the screw when the injection is completed is equal to or less than a second distance from the first injection start position to the injection completion position, The injection molding machine according to claim 3, wherein the molding material is injected, and the molding material is not injected when the first distance is longer than the second distance.   The injection device injects the molding material when the first distance is equal to or less than a correction distance from a correction position obtained by adding a predetermined value to the first injection start position to the injection completion position, and the first distance is smaller than the correction distance. The injection molding machine according to claim 2, wherein the molding material is not injected when the distance is longer than the correction distance. The injection device is provided at the tip of the barrel, and includes a nozzle that injects the molding material,
The injection molding machine according to any one of claims 1 to 5, wherein the injection device injects the molding material when the nozzle is not in contact with the first mold or the second mold. A nozzle position sensor for detecting a position of the nozzle,
The injection molding machine according to claim 6, wherein the control unit determines whether the nozzle is in contact with the first mold or the second mold based on a position of the nozzle.   The injection molding machine according to any one of claims 1 to 7, wherein the injection device injects the molding material when the first mold and the second mold are not in contact with each other. At least one of the first mold and the second mold is movably provided,
A mold position sensor for detecting a position of the at least one mold,
The injection molding machine according to claim 8, wherein the control unit determines whether the first mold and the second mold are in contact with each other based on a position of the at least one mold. The injection device injects the molding material when the injection disable setting that does not inject the molding material is invalid,
The injection molding machine according to any one of claims 1 to 9, wherein the injection disable setting is set to be enabled or disabled by a user.

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