Injection molding machine for implementing foam molding and control method of injection molding machine

Abstract

An injection molding machine (1) includes a heated cylinder (17) provided with a gas injection port (26), a screw (18), a gas cylinder (30), a pressure reducing valve that reduces a primary pressure of gas from the gas cylinder (30) to a secondary pressure, a gas supply portion (43) that supplies the secondary pressure gas to the gas injection port (26), a secondary pressure detecting mechanism that detects the secondary pressure, and a control mechanism. Also, the control mechanism detects an abnormality by comparing a set pressure set in advance in the injection molding machine (1) with the secondary pressure.

Description

Technical Field

[0001] This invention relates to an injection molding machine for injecting inactive gas into injection material to form foamed articles, and a method for controlling such an injection molding machine. Background Technology

[0002] An injection molding machine that uses a physical foaming agent, i.e., an inert gas, to obtain foamed molded articles generally has the following structure. Specifically, the injection molding machine for foam molding consists of a heating cylinder and a screw. The heating cylinder is divided into multiple sections corresponding to the shape of the screw, including a first compression / metering section, a starvation section, and a second compression / metering section from upstream to downstream. The heating cylinder has an injection section for the inert gas corresponding to the starvation section. The inert gas is supplied from a gas supply source such as a gas cylinder. The primary pressure of the gas supplied from the gas supply source is reduced to a secondary pressure by a pressure reducing valve. This secondary pressure inert gas is connected to the injection section.

[0003] The injection material is conveyed and melted from upstream to downstream by a screw in a heated cylinder, and then mixed in the first compression / metering zone. Next, in the starvation zone, the pressure of the injection material is reduced, and a secondary pressurized inert gas is injected. The injection material injected with the inert gas is mixed / compressed and metered in the second compression / metering zone, and then injected into a mold to obtain a foamed molded product.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-200937 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In injection molding machines used for foaming, the injected material may be pushed up in the inactive gas injection section, causing blockage and resulting in a so-called "bent up". Patent Document 1 describes an injection molding machine for foaming that has a bent up detection mechanism in the injection section. If bent up occurs, it is mechanically detected and the injected material is pushed back into the heating cylinder.

[0009] In injection molding machines used for foam molding, several problems occur besides material overflow. These include backflow of inert gases and poor supply of inert gases. The secondary pressure of the inert gases is appropriately controlled by a pressure reducing valve, and the pressure is visually confirmed to reach the desired level using a pressure gauge. Additionally, the injection material is also controlled to ensure an appropriate supply. However, it is impossible to completely prevent these problems, and there is a risk that problems may go unnoticed, resulting in a large number of defective products.

[0010] Other topics and new features can be found in the description and figures in this specification.

[0011] Methods for solving problems

[0012] This disclosure relates to an injection molding machine having the following configuration: The injection molding machine includes: a heating cylinder having a gas injection port; a screw; a gas storage tank; a pressure regulating mechanism that regulates the primary pressure of gas from the gas storage tank to a secondary pressure; a gas injection port that supplies the secondary-pressure gas to the heating cylinder; a secondary pressure detection mechanism that detects the secondary pressure; and a control mechanism. Furthermore, the control mechanism compares a preset pressure in the injection molding machine with the secondary pressure to detect abnormalities.

[0013] Invention Effects

[0014] According to this disclosure, early signs of material overflow, gas backflow, or poor gas supply can be quickly detected to prevent the production of defective products. Attached Figure Description

[0015] Figure 1 This is a front view showing the injection molding machine of this embodiment.

[0016] Figure 2 This is a front sectional view showing the injection device of this embodiment.

[0017] Figure 3 This is a flowchart illustrating the control method implemented in the injection molding machine according to this embodiment.

[0018] Figure 4 This is a flowchart illustrating the control method implemented in the injection molding machine according to this embodiment.

[0019] Figure 5 This is a flowchart illustrating the control method implemented in the injection molding machine according to this embodiment.

[0020] Figure 6 This is a flowchart illustrating the control method implemented in the injection molding machine according to this embodiment.

[0021] Figure 7 This is a flowchart illustrating the control method implemented in the injection molding machine according to this embodiment.

[0022] Figure 8 This is a diagram illustrating the control method of the injection molding machine according to this embodiment, implemented in response to the secondary pressure of the gas. Detailed Implementation

[0023] Hereinafter, specific embodiments will be described in detail with reference to the accompanying drawings. However, the description is not limited to these embodiments. To make the explanation clear, the following description and drawings have been appropriately simplified. In each drawing, the same reference numerals are used to refer to the same elements, and repeated descriptions are omitted as needed. In addition, some sections have been omitted to avoid cluttering the drawings.

[0024] This implementation method will be described.

[0025] <Injection Molding Machine>

[0026] like Figure 1 As shown, the injection molding machine 1 of this embodiment generally consists of a mold clamping device 2 and an injection device 3 mounted on a base B, and is controlled by a controller 4, which serves as a control mechanism. The mold clamping device 2 can also be a direct-pressure type, but in this embodiment it is a toggle type. That is, the mold clamping device 2 consists of a fixed plate 7, a movable plate 8, a mold clamping housing 9, connecting rods 10, 10, ... connecting the mold clamping housing 9 to the fixed plate 7, and a toggle mechanism 11. In the mold clamping device 2, molds 13 and 14 are mounted on the fixed plate 7 and the movable plate 8. If the toggle mechanism 11 is driven, molds 13 and 14 close.

[0027] <Injection Device>

[0028] like Figure 2 As shown, the injection apparatus 3 of this embodiment is an injection apparatus for foam molding using a physical foaming agent, i.e., gas. The injection apparatus 3 consists of a heating cylinder 17 and a screw 18 installed in the heating cylinder 17. The screw 18 is divided into multiple sections within the heating cylinder 17, and the groove depth of the thread changes from the upstream side to the downstream side. That is, the heating cylinder 17 is divided from the upstream side into a supply section 20 where the injection material is supplied and melted, a first compression / metering section 21 where the molten injection material is compressed, a starvation section 22 where the pressure of the injection material decreases, and a second compression / metering section 23. The heating cylinder 17 has a gas injection port 26 in the starvation section 22 to inject gas into the injection material. In the second compression / metering section 23, the injection material and gas are mixed.

[0029] <Gas Supply Device>

[0030] The gas injection port 26 is connected to the gas supply device 28 of this embodiment. The gas supply device 28 is configured to include: two gas cylinders 30, 30 serving as a gas supply source; gas cylinder opening and closing valves 31, 31; a primary gas pipe 33, which supplies gas from the gas cylinders 30, 30 via the gas cylinder opening and closing valves 31, 31; a pressure reducing valve 34 serving as a pressure regulating mechanism, which regulates the gas pressure in the primary gas pipe 33, i.e., the primary pressure; a secondary gas pipe 36, which supplies gas that has been reduced to a secondary pressure by the pressure reducing valve 34; a check valve 38, which is provided on the secondary gas pipe 36; and an opening and closing valve 39 serving as an opening and closing mechanism, which is also provided on the secondary gas pipe 36. A primary pressure gauge 41, which serves as a primary pressure detection mechanism, is provided on the primary gas pipe 33, and a secondary pressure gauge 42, which serves as a secondary pressure detection mechanism, is provided on the secondary gas pipe 36. The front end of the secondary gas pipe 36 becomes a gas supply section 43 and is connected to the gas injection port 26.

[0031] The primary pressure gauge 41 and secondary pressure gauge 42 of the devices constituting the gas supply device 28 are connected to the controller 4, and the primary and secondary pressures are input to the controller 4. In addition, the gas cylinder opening and closing valves 31, 31, pressure reducing valve 34, and opening and closing valve 39 are connected to the controller 4, and the gas cylinder opening and closing valves 31, 31, pressure reducing valve 34, and opening and closing valve 39 are controlled by the controller 4.

[0032] The gas supply device 28 of this embodiment is configured as described above, but the present invention can be implemented with one or more gas storage cylinders 30. The gas supply device 28 may also include, for example, gas storage cylinders 30 and 30 and a pressure boosting device, or a nitrogen generating device and a pressure boosting device. The supplied gas is typically nitrogen, carbon dioxide, or other inert gases, but the type is not limited; it can be air, hydrocarbon gases, argon, helium, hydrogen, or other gases dissolved in resin. Furthermore, the on / off valve 39 can be located midway in the gas pipe supplying secondary pressurized gas to the gas injection port, or it can be an on / off mechanism such as a needle valve operating with compressed air provided at the gas injection section. In this embodiment, the gas storage cylinder on / off valves 31 and 31 are gas supply source switching mechanisms that select which of the gas storage cylinders 30 and 30 will be used as the gas supply source. By opening and closing the gas storage cylinder on / off valves 31 and 31, the gas storage cylinder 30 and 30 to be used can be switched.

[0033] In the gas supply device 28, the gas cylinder opening / closing valve 31, primary pressure gauge 41, check valve 38, and opening / closing valve 39 are not strictly necessary, but their inclusion allows for various responses to abnormal gas supply. Furthermore, while the controller 4 is connected to multiple devices, even with only the secondary pressure gauge 42 connected, it can handle most situations with minimal intervention. Online monitoring of the secondary pressure enables rapid anomaly detection.

[0034] <Feeder>

[0035] In this embodiment, a feeder 44 is installed on the heating cylinder 17 of the injection apparatus 3. The feeder 44 is also connected to and controlled by a controller 4 to control the amount of injection material supplied from the hopper 45 to the heating cylinder 17. The feeder 44 is equipped with an injection material detection sensor 46, which serves as an injection material detection mechanism and is also connected to the controller 4. The controller 4 can determine whether injection material is being supplied appropriately from the feeder 44 based on the signal from the injection material detection sensor 46. It should be noted that the injection material detection sensor 46 can be installed on the feeder 44, or on the injection material supply port of the heating cylinder 17, or on the hopper 45. Alternatively, it can be installed on a material handling device or the like that automatically supplies injection material to the feeder 44 or the hopper 45. When the injection material detection sensor 46 is installed on the hopper 45, the material handling device, or the like, it is sufficient to detect whether there is any remaining injection material supplied to the feeder 44.

[0036] <Controller>

[0037] As detailed below, the injection molding machine 1 of this embodiment can detect various anomalies by monitoring the secondary pressure of the gas in the controller 4. Furthermore, when an anomaly is detected, the controller 4 takes various responses depending on the nature of the anomaly. To detect anomalies and take measures against them, the controller 4 is equipped with various setpoints and programs. The setpoints include a setpoint for the secondary pressure of the gas (i.e., a set pressure), thresholds 1 to 5 used for judging an anomaly, and stabilization times 1 to 4. The controller 4 includes programs for implementing alarm output, pressure reduction control, pressure increase control, supply quantity reduction control, supply quantity increase control, and gas supply source switching control.

[0038] In the injection molding machine 1 of this embodiment, the amount of gas dissolved in the injection material is controlled by the gas pressure supplied to the heating cylinder 17. Because the screw 18, located in the starvation zone 22, has deep grooves and a large volume between the threads, the resin flowing in from the upstream first compression / metering zone 21 is depressurized, and the injection material pressure becomes approximately zero. Therefore, even lower-pressure gases that can be supplied from gas cylinders or the like can be stably supplied. The gas supplied to the heating cylinder 17 fills the starvation zone 22 of the heating cylinder 17. Since the gas acts isotropically as fluid pressure, the injection material pressure in the starvation zone 22 is approximately the same as the secondary pressure. The gas contacts the molten resin in the starvation zone 22, dissolving an amount corresponding to the gas pressure. That is, the amount of gas dissolved in the molten resin increases proportionally to the secondary pressure.

[0039] On the other hand, if the resin in the starvation zone 22 increases and the injection material pressure rises for some reason, resin may overflow through the gas injection port 26, preventing gas from being supplied to the heating cylinder 17. In this case, the resin blocking the gas injection port 26 compresses the gas in the secondary gas pipe 36, increasing the secondary pressure. By detecting this situation, poor gas supply caused by overflow can be detected.

[0040] Furthermore, if the primary pressure of the gas supplied from the gas supply source is not sufficiently high relative to the secondary pressure, the amount of gas supplied to the heating cylinder 17 decreases due to the reduced secondary pressure. Consequently, the gas pressure in the starvation zone 22 within the heating cylinder 17 decreases, and the amount of gas dissolved in the molten resin decreases. In this case, by detecting the decrease in either the primary or secondary pressure, defects caused by insufficient gas supply from the gas supply source can be detected.

[0041] On the other hand, in this embodiment, the feeder 44 is used to reduce the amount of resin material supplied. Normally, the gas supplied to the heating cylinder 17 is sealed by molten resin between the starvation zone 22 and the first compression / metering zone 21. However, in cases where the resin supply from the feeder 44 is insufficient or there is no material (e.g., the feeder 44 is not used), the seal may temporarily or continuously break, causing gas to flow back to the primary side. In this case, the gas backflow can be detected by detecting a sharp change in the secondary pressure.

[0042] If issues such as material overflow, reduced gas pressure, or gas backflow occur, molding defects will frequently occur. Therefore, in the injection molding machine 1 of this embodiment, the management of secondary pressure and the detection of abnormalities become important.

[0043] <Control method of injection molding machine according to this embodiment>

[0044] The control method of the injection molding machine according to this embodiment will be described below. In the control method of the injection molding machine according to this embodiment, the secondary pressure of the gas detected by the secondary pressure gauge 42 is input to the controller 4. The controller 4 determines whether the pressure is normal or abnormal and takes necessary measures. The controller 4 uses thresholds 1 to 5 as the basis for determining whether the secondary pressure is normal or abnormal, and as the basis for deciding on the measures to be taken. Figure 8 The summary outlines the normal / abnormal secondary pressure assessment based on thresholds 1 through 5 and the corresponding measures taken. The following diagram illustrates the processing of controller 4.

[0045] <Controller Processing>

[0046] like Figure 3As shown, controller 4 transitions from the start to step S1, determining whether the secondary pressure is greater than the set value plus the first threshold. If the secondary pressure is lower than the set value plus the first threshold, controller 4 transitions to step S2. In step S2, controller 4 determines whether the secondary pressure of the gas is less than the set value minus the second threshold. If the secondary pressure is greater than the set value minus the second threshold, controller 4 determines it to be normal. That is, based on the set value, the range greater than the lower second threshold and lower than the upper first threshold is defined as the normal pressure range. If the secondary pressure is within the normal pressure range, controller 4 determines it to be normal and returns to the start.

[0047] If, in step S1, it is determined that the secondary pressure is greater than the set value and the difference is greater than the first threshold, then controller 4 proceeds to step S3. In step S3, controller 4 checks whether the secondary pressure is greater than the set value and whether the difference is less than the third threshold. If it becomes greater than the third threshold, the possibility of material overflow is high. At this time, controller 4 implements stop processing SS.

[0048] like Figure 5 As shown, in step S21, the stop procedure SS checks whether the opening and closing mechanism, i.e., the opening and closing valve 39, is controllable. If the opening and closing valve 39 is present, the controller 4 executes step S22 to close the opening and closing valve 39 and stop the gas supply. Next, regardless of whether the opening and closing valve 39 is present, the controller 4 executes step S23, waiting for the currently executing molding cycle to complete, thus stopping the molding cycle. It should be noted that the stop procedure SS can be executed immediately based on its cause, urgency, and whether the operation is manned or unmanned, or it can be executed after a certain time or a certain period of delay. In addition, in order to notify the operator of the abnormality, the controller 4 can also execute the alarm procedure SB, which will be described later, at the same time as or before the stop procedure SS.

[0049] In step S3, controller 4 proceeds to step S4 when it determines that the difference between the secondary pressure and the set value is lower than the third threshold. In step S4, it determines whether the pressure reducing valve 34 can be operated by controller 4, i.e., whether there is a pressure control mechanism. If there is no pressure control mechanism, controller 4 proceeds to step S7. It should be noted that, alternatively, if controller 4 determines that the difference between the secondary pressure and the set value is lower than the third threshold in step S3, then regardless of the determination in step S4, i.e., regardless of whether there is a pressure control mechanism, alarm processing SA is implemented. In alarm processing SA, controller 4 outputs an alarm indicating a risk of material leakage at gas injection port 26. The alarm can be displayed on a monitor attached to controller 4, or an alarm sound can be output from a speaker. Alternatively, it can be sent to the manager via email, etc.

[0050] In step S4, if a pressure control mechanism is detected, controller 4 proceeds to step S5 to implement pressure reduction control. In this pressure reduction control, pressure reducing valve 34 is controlled to lower the secondary pressure to the normal pressure range. Even when pressure reducing valve 34 lowers the secondary pressure, the pressure in the downstream secondary pressure gauge 42, compared to check valve 38, does not immediately decrease. This is because, if gas inlet 26 is not blocked by resin, gas in the piping is supplied to heating cylinder 17 and dissolves in the molten resin, thus gradually reducing the pressure.

[0051] If controller 4 implements pressure reduction control, the process is observed in step S6. That is, controller 4 monitors the secondary pressure and checks whether it returns to the normal pressure range within the first stabilization time. If it returns to the normal pressure range within the first stabilization time, controller 4 determines it is normal. That is, controller 4 returns the process to the beginning. However, if the secondary pressure does not return to the normal pressure range within the first stabilization time and the difference between the secondary pressure and the set pressure is lower than the third threshold, controller 4 proceeds to step S7.

[0052] Step S7 is a process that is either directly transferred from step S4 or transferred from step S6 and executed. In step S7, controller 4 checks whether a feeder control mechanism exists. That is, controller 4 has a feeder 44 and checks whether it can be controlled by controller 4. If there is no feeder control mechanism, controller 4 implements the described stop process SS. If there is a feeder control mechanism, controller 4 implements the supply reduction control of step S8. That is, controller 4 controls feeder 44 to reduce the supply of injection material. This is because if the supply of injection material is reduced, the injection material is difficult to bulge at the gas injection port.

[0053] If controller 4 implements supply reduction control, the process is observed through step S9. That is, controller 4 monitors the secondary pressure and checks whether the secondary pressure returns to the normal pressure range within the second stabilization time. If it returns to the normal pressure range within the second stabilization time, controller 4 determines it is normal. That is, controller 4 returns the process to the beginning. However, if the secondary pressure does not return to the normal pressure range within the second stabilization time, controller 4 implements the described stop process SS.

[0054] If, in step S2, the controller 4 determines that the secondary pressure of the gas is more than a second threshold lower than the set value, it will proceed to process A. For example... Figure 4 As shown, controller 4 proceeds to step S11. In step S11, controller 4 checks whether the secondary pressure of the gas is lower than the set pressure and whether the difference between the secondary pressure and the set pressure is greater than or equal to the 5th threshold. If it becomes greater than or equal to the 5th threshold, controller 4 determines that a gas supply abnormality has occurred and implements the described stop procedure SS. On the other hand, if the difference between the secondary pressure and the set pressure is lower than the 5th threshold, controller 4 proceeds to step S12.

[0055] In step S12, the controller 4 confirms the rate of decrease of the secondary pressure of the gas. That is, regarding the secondary pressure of the gas, the controller 4 calculates the percentage decrease per unit time, i.e., the rate of decrease, and checks whether this rate of decrease is above the fourth threshold. When the rate of decrease is above the fourth threshold, there is a high probability that the gas will momentarily backflow within the heating cylinder 17. In this case, the controller 4 proceeds to step S16.

[0056] In step S16, controller 4 checks whether a feeder control mechanism exists. That is, controller 4 checks whether injection molding machine 1 has a feeder 44 and whether it can be controlled by controller 4. If no feeder control mechanism exists, controller 4 performs the described stop procedure SS. If a feeder control mechanism exists, controller 4 performs the supply increase control in step S17. That is, controller 4 controls feeder 44 to increase the supply of injection material. This is because if the supply of injection material increases, the resin in the sealing section increases, which can liquid-tightly prevent gas backflow.

[0057] If controller 4 implements supply increase control, the process is observed in step S18. During a reference molding cycle number, for example, 5 molding cycles, if the rate of decrease in secondary pressure is lower than the 4th threshold, it can be judged as normal. Similarly, during a reference 4th stabilization time, if the rate of decrease in secondary pressure is lower than the 4th threshold, it can be judged as normal. Since several injections are required before the effect of supply increase control is manifested, a delay time during the reference number of cycles or reference time can be set to avoid observation. If the rate of decrease in secondary pressure becomes higher than the 4th threshold even after implementing supply increase control, controller 4 implements the described stop process SS.

[0058] In step S12, if the controller 4 determines that the rate of decrease of the secondary pressure of the gas is lower than the fourth threshold, it determines that the supply pressure from the gas supply source, i.e., the primary pressure, is likely to decrease, and proceeds to step S13.

[0059] In step S13, controller 4 checks for the presence of a pressure control mechanism. If no pressure control mechanism is present, controller 4 proceeds to process B. Process B is shown in... Figure 6 The controller 4 first executes step S31. That is, the controller 4 checks whether there is a gas supply source switching mechanism. In this embodiment, the gas supply source switching mechanism is the gas cylinder opening and closing valves 31 and 31, which switch the gas cylinders 30 and 30 that serve as gas supply sources. If it is determined that there is a gas supply source switching mechanism, the controller 4 executes step S32, operates the gas cylinder opening and closing valves 31 and 31, and implements the gas supply source switching control to switch the currently used gas cylinder 30 to another gas cylinder 30.

[0060] In the absence of a gas supply source switching mechanism, or if the secondary pressure fails to return to normal even after gas supply source switching control is executed, controller 4 implements alarm processing SB, issuing an alarm urging the replacement of gas cylinder 30. The alarm can be output as a message to the monitor, as an alarm sound to the speaker, or as an email to the administrator. Alternatively, a stop process can be executed simultaneously with alarm processing SB.

[0061] In step S13, if it is determined that there is a pressure control mechanism, the controller 4 proceeds to step S14.

[0062] In step S14, controller 4 implements pressure increase control. That is, it controls pressure reducing valve 34 to bring the secondary pressure back to the normal pressure range.

[0063] If pressure increase control is implemented, controller 4 observes the process through step S15. That is, controller 4 monitors the secondary pressure and checks whether the secondary pressure returns to the normal pressure range within the third stabilization time. If it returns to the normal pressure range within the third stabilization time, controller 4 determines it is normal. That is, controller 4 returns the process to the beginning. However, if the secondary pressure does not return to the normal pressure range within the third stabilization time and the difference between the secondary pressure and the set pressure is lower than the fifth threshold, controller 4 executes the described process B.

[0064] In the injection molding machine 1 of this embodiment, the controller 4 also checks whether the supply of injection material is normal. That is, as... Figure 7 As shown, controller 4 performs step S41. The injection material detection sensor 46 checks at predetermined intervals whether the injection material has fallen into the heating cylinder 17. If the injection material supply is abnormal, there is a possibility of seal rupture and gas backflow to the feeder side due to the depletion of injection material; therefore, the described stop procedure SS is performed.

[0065] It should be noted that in S13 and S15 of this embodiment, the controller 4 uses the first, second, fourth, and fifth thresholds, and the presence or absence of a pressure control mechanism, as the judgment criteria for executing process B, i.e., gas supply source switching control. However, the controller 4 may also more directly use the difference between the set pressure or secondary pressure and the primary pressure as the judgment criteria. In this case, the controller 4 may also use the sixth threshold as the judgment criteria for the difference between the primary pressure and the set pressure or secondary pressure. If the difference between the primary pressure and the set pressure or secondary pressure is lower than the sixth threshold, process B is executed. The sixth threshold can be appropriately determined according to the gas usage, for example, 1 MPa can be used as a reference.

[0066] The above describes the control method for the injection molding machine according to this embodiment, explaining the use of first and second threshold values ​​for setting pressure to determine whether the secondary pressure is normal or abnormal. While this is related to the size of the molding machine and the configuration of the gas supply device, even within the normal operating range of the molding machine, the secondary pressure may vary by approximately 0 to 0.5 MPa in a standard-sized molding machine and by approximately 0.5 to 1.0 MPa in a large molding machine due to the dissolution of gas into the injection material. Therefore, it is preferable to set the first and second threshold values ​​in the range of 0.1 to 1.5 MPa, and more preferably in the range of 0.2 to 1.0 MPa. The third and fifth threshold values ​​need to be larger than the above ranges; for example, they can be appropriately determined based on the variation range of the gas pressure within the range of 0.5 to 3.0 MPa.

[0067] However, proportions can also be used in such judgments. For example, the secondary pressure can be set to the normal range from 95% to 110% of the set pressure. Even if a proportion is used for judgment in this way, it is essentially the same as using the first and second thresholds for judgment. That is, this is because it is the same as setting the first threshold to 10% of the set pressure and the second threshold to 5% of the set pressure.

[0068] Alternatively, upper and lower limits of the normal range can be used. For example, if the gas pressure setting is 10 MPa, the normal range can be set from 10.5 MPa to 9.5 MPa. However, in this case, the normal range value needs to be changed whenever the gas pressure setting is changed. Therefore, using the first or second threshold or ratio for judgment can save users trouble and is preferred.

[0069] The use of a secondary pressure gauge 42 in this embodiment has been described, but a pressure switch can also be used instead. In this case, the pressure switch can be set with an upper or lower limit value corresponding to the first, second, third, and fifth threshold values ​​within a normal range. When the secondary pressure exceeds the normal range, the controller 4 receives a signal from the pressure switch. The pressure switch can be set manually or through communication with the controller 4. However, in the case of manual setting, the pressure switch setting needs to be changed whenever the gas pressure setting value is changed. Therefore, setting the pressure switch through communication with the controller 4 and in conjunction with the setting value is preferred as it saves the user trouble.

[0070] Alternatively, the detection of the pressure drop rate at the fourth threshold can also be performed without detecting the pressure drop rate of the secondary pressure gauge 42, instead using a flow meter or differential pressure gauge to detect the backflow of gas within the heating cylinder based on the gas flow rate. This is because the secondary pressure drop caused by backflow is the same as the increase in gas flow rate. When using a flow meter or differential pressure gauge, the flow rate of the gas used within the normal operating range can be predetermined, and the range exceeding that flow rate can be used as a substitute indicator for the fourth threshold.

[0071] Furthermore, the control method for the injection molding machine in this embodiment has multiple gas pressure setpoints, and can also be applied when controlling the pressure to vary in segments. In this case, the first and second thresholds can be set in a manner that includes the maximum and minimum values ​​of the multiple gas pressure setpoints, or a setpoint equivalent to the first and second thresholds can be set for each gas pressure setpoint.

[0072] The invention proposed by the inventors of this application has been specifically described above based on the embodiments, but the invention is not limited to the described embodiments. For example, the order of each step can be changed, or alarm processing SA or stop processing SS can be implemented whenever the secondary pressure exceeds the normal range, and various modifications can be made without departing from its essence. In addition, the measures can be changed depending on whether the machine is operated or not. For example, when the machine is operated, the policy of changing the molding conditions can be displayed in a guiding manner instead of the feeder 44's supply increase control and supply decrease control. In cases of low urgency, stop processing SS can be omitted and the alarm processing can be left to the operator. The various examples described above can also be appropriately combined and implemented.

[0073] Here, the features of the embodiments of the injection molding machine and the control method of the injection molding machine for foaming of the present invention are briefly summarized and listed below [1] to

[28] .

[0074] [1] An injection molding machine (1), comprising:

[0075] Heating cylinder (17) is provided with a gas injection port (26);

[0076] A screw (18) configured to be driven within the heating cylinder (17); a gas supply device (28) supplying gas to the gas inlet (26); and

[0077] Control mechanism,

[0078] In the injection molding machine (1),

[0079] The gas supply device (28) includes:

[0080] A gas supply source that supplies gas;

[0081] A pressure regulating mechanism that adjusts the primary pressure of the gas from the gas supply source to a secondary pressure; and

[0082] The secondary pressure testing mechanism measures the secondary pressure.

[0083] The gas supply device (28) supplies the secondary pressure gas to the gas injection port (26).

[0084] The control mechanism compares the set pressure with the secondary pressure to detect anomalies.

[0085] [2] According to the injection molding machine (1) of [1], the control mechanism makes the normal pressure range of the secondary pressure greater than the value obtained by subtracting the second threshold from the set pressure and lower than the value obtained by adding the first threshold to the set pressure, and detects the abnormality of the secondary pressure based on the normal pressure range.

[0086] [3] According to the injection molding machine (1) of [2], when the secondary pressure is greater than the normal pressure range and the secondary pressure is lower than the value obtained by adding the third threshold to the set pressure, the control mechanism issues a danger alarm for material leakage at the gas injection port (26).

[0087] [4] According to the injection molding machine (1) of [2], when the secondary pressure is greater than or equal to the value obtained by adding the third threshold to the set pressure, the control mechanism stops the molding cycle after the molding cycle is completed.

[0088] [5] According to the injection molding machine (1) described in [2], the gas supply device (28) has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port (26).

[0089] When the secondary pressure is greater than or equal to the value obtained by adding the third threshold to the set pressure, the control mechanism closes the opening and closing mechanism and stops the molding cycle after it is completed.

[0090] [6] According to the injection molding machine (1) of [2], the control mechanism includes a pressure control mechanism for controlling the pressure adjustment mechanism. When the secondary pressure is greater than the normal pressure range and the secondary pressure is lower than the value obtained by adding the third threshold to the set pressure, the pressure control mechanism implements pressure reduction control so that the secondary pressure becomes the normal pressure range.

[0091] [7] According to the injection molding machine (1) of [6], during the first stabilization time from the start of the pressure reduction control, if the secondary pressure is continuously higher than the normal pressure range, the control mechanism stops the molding cycle after the molding cycle is completed.

[0092] [8] According to the injection molding machine (1) described in [6], the gas supply device (28) has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port (26).

[0093] During the first stabilization period following the start of the pressure reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism closes the opening and closing mechanism and stops the molding cycle upon completion of the ongoing molding cycle.

[0094] [9] According to the injection molding machine (1) described in [6], wherein the heating cylinder (17) is equipped with a feeder (44) for adjusting the supply amount of injection material.

[0095] During the first stabilization period from the start of the pressure reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism implements a supply reduction control to control the feeder (44) to reduce the supply of injection material.

[0096]

[10] According to the injection molding machine (1) described in [2], wherein the heating cylinder (17) is equipped with a feeder (44) for adjusting the supply amount of injection material.

[0097] When the secondary pressure is greater than the normal pressure range and the secondary pressure is lower than the value obtained by adding the third threshold to the set pressure, the control mechanism implements a supply reduction control to control the feeder (44) to reduce the supply of injection material.

[0098]

[11] According to the injection molding machine (1) of [9] or

[10] , wherein, during the second stabilization time from the start of the supply reduction control, if the secondary pressure is continuously higher than the normal pressure range, the control mechanism stops the molding cycle after the molding cycle is completed.

[0099]

[12] According to the injection molding machine (1) described in [9] or

[10] , wherein the gas supply device (28) has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port (26).

[0100] During the second stabilization period following the start of the supply reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism closes the opening and closing mechanism and stops the molding cycle upon completion of the ongoing molding cycle.

[0101]

[13] According to the injection molding machine (1) of [2], when the secondary pressure is less than the normal pressure range and the rate of decrease of the secondary pressure becomes above the fourth threshold, the control mechanism stops the molding cycle after the molding cycle is completed.

[0102]

[14] According to the injection molding machine (1) described in [2], the gas supply device (28) has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port (26).

[0103] When the secondary pressure is less than the normal pressure range and the rate of decrease of the secondary pressure becomes above the fourth threshold, the control mechanism closes the opening and closing mechanism and stops the molding cycle after it is completed.

[0104]

[15] According to the injection molding machine (1) described in [2], wherein the heating cylinder (17) is equipped with a feeder (44) for adjusting the supply amount of injection material.

[0105] When the secondary pressure is greater than the value obtained by subtracting the fifth threshold from the set pressure, and the rate of decrease of the secondary pressure becomes greater than the fourth threshold, the control mechanism implements a supply increase control to control the feeder (44) to increase the supply of injection material.

[0106]

[16] According to the injection molding machine (1) of

[15] , wherein, during a predetermined period from the start of the supply increase control or during the fourth stabilization period from the start of the supply increase control, if the rate of decrease of the secondary pressure is temporarily higher than the fourth threshold, the control mechanism stops the molding cycle after the molding cycle is completed.

[0107]

[17] According to the injection molding machine (1) described in

[15] , the gas supply device (28) has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port (26).

[0108] During a predetermined period from the start of the supply increase control or during the fourth stabilization period from the start of the supply increase control, if the rate of decrease of the secondary pressure is temporarily higher than the fourth threshold, the control mechanism closes the opening and closing mechanism and stops the molding cycle after the ongoing molding cycle is completed.

[0109]

[18] According to the injection molding machine (1) of [2], wherein when the secondary pressure is below the value obtained by subtracting the fifth threshold from the set pressure, the control mechanism stops the molding cycle after the molding cycle is completed.

[0110]

[19] According to the injection molding machine (1) of [2], wherein the gas supply device (28) has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port (26).

[0111] When the secondary pressure is below the value obtained by subtracting the fifth threshold from the set pressure, the control mechanism closes the opening and closing mechanism and stops the molding cycle after the molding cycle is completed.

[0112]

[20] According to the injection molding machine (1) of [2], when the secondary pressure is lower than the normal pressure range but greater than the value obtained by subtracting the fifth threshold from the set pressure, and the rate of decrease of the secondary pressure is lower than the fourth threshold, the control mechanism issues an alarm urging the replacement of the gas supply source.

[0113]

[21] According to the injection molding machine (1) described in [2], the gas supply device (28) includes a plurality of gas supply sources and a gas supply source switching mechanism, which switches between the plurality of gas supply sources to select one gas supply source as the object to be used.

[0114] When the secondary pressure is lower than the normal pressure range but greater than the value obtained by subtracting the fifth threshold from the set pressure, and the rate of decrease of the secondary pressure is lower than the fourth threshold, the control mechanism uses the gas supply source switching mechanism to switch the currently used gas supply source to another gas supply source.

[0115]

[22] According to the injection molding machine (1) described in [2], the control mechanism includes a pressure control mechanism for controlling the pressure regulating mechanism.

[0116] When the secondary pressure is lower than the normal pressure range but greater than the value obtained by subtracting the fifth threshold from the set pressure, and the rate of decrease of the secondary pressure is lower than the fourth threshold, the pressure control mechanism is used to implement pressure increase control so that the secondary pressure becomes the normal pressure range.

[0117]

[23] According to the injection molding machine (1) of

[22] , during the third stabilization time from the start of the pressure increase control, if the secondary pressure is lower than the normal pressure range and remains at a value greater than the value obtained by subtracting the fifth threshold from the set pressure, the control mechanism issues an alarm urging the replacement of the gas supply source.

[0118]

[24] According to the injection molding machine (1) of

[22] , the gas supply device (28) includes a plurality of gas supply sources and a gas supply source switching mechanism, which switches between the plurality of gas supply sources to select one gas supply source as the object to be used.

[0119] During the third stabilization period from the start of the pressure increase control, if the secondary pressure is lower than the normal pressure range and remains at a value greater than the value obtained by subtracting the fifth threshold from the set pressure, the control mechanism uses the gas supply source switching mechanism to switch the currently used gas supply source to another gas supply source.

[0120]

[25] The injection molding machine (1) according to any one of [1] to

[24] , wherein the gas supply device (28) comprises: a plurality of gas supply sources; a gas supply source switching mechanism that selects and switches from the plurality of gas supply sources to one gas supply source for use; and a primary pressure detection mechanism that detects the primary pressure of the gas from the gas supply source.

[0121] The control mechanism compares the primary pressure with the difference between the set pressure or the secondary pressure, detects a decrease in the pressure of the gas supply source, and, upon detecting a decrease in the pressure of the gas supply source, uses the gas supply source switching mechanism to switch the currently used gas supply source to another gas supply source.

[0122]

[26] According to the injection molding machine (1) described in [2], wherein the injection molding machine (1) is equipped with an injection material detection mechanism for confirming the supply of injection material to the heating cylinder (17),

[0123] When the injection material detection mechanism detects that the injection material has been used up due to an interruption in the injection process, it stops the molding cycle after the ongoing molding cycle is completed.

[0124]

[27] According to the injection molding machine (1) described in [2], the injection molding machine (1) is equipped with an injection material detection mechanism for confirming the supply of injection material to the heating cylinder (17).

[0125] The gas supply device (28) has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port (26).

[0126] When the injection material detection mechanism detects that the injection material has been used up due to an interruption in the injection process, it closes the opening and closing mechanism and stops the molding cycle after the ongoing molding cycle is completed.

[0127]

[28] A control method for an injection molding machine, wherein the injection molding machine comprises:

[0128] Heating cylinder (17) is provided with a gas injection port (26);

[0129] The screw (18) is configured to be actuated within the heating cylinder (17); and

[0130] Gas supply device (28) supplies gas to the gas injection port (26),

[0131] The gas supply device (28) includes:

[0132] A gas supply source that supplies gas;

[0133] A pressure regulating mechanism that adjusts the primary pressure of the gas from the gas supply source to a secondary pressure; and

[0134] The secondary pressure testing mechanism measures the secondary pressure.

[0135] The gas supply device (28) supplies the secondary pressure gas to the gas injection port (26).

[0136] In the control method of the injection molding machine,

[0137] Anomalies are detected by comparing the set pressure with the secondary pressure.

[0138] This application is based on Japanese Patent Application No. 2020-204664, filed on December 10, 2020, the contents of which are incorporated herein by reference.

[0139] Industrial availability

[0140] According to the present invention, it is possible to quickly detect early signs such as material overflow, gas backflow, and poor gas supply, thus preventing the production of defective products. This invention, possessing this effect, is useful for injection molding machines used in foam molding and for control methods of injection molding machines.

[0141] Explanation of reference numerals in the attached figures

[0142] 1 Injection molding machine 2 Mold clamping device

[0143] 3. Injection device 4. Controller

[0144] 17 Heating cylinder 18 Screw

[0145] 20 Supply Interval 21 First Compression / Metering Interval

[0146] 22 Hunger Zone 23 Second Compression / Measurement Zone

[0147] 26 Gas injection port 28 Gas supply device

[0148] 30 Gas cylinder 31 Gas cylinder opening / closing valve

[0149] 33 Primary gas line 34 Pressure reducing valve

[0150] 36 Secondary gas pipe; 38 Check valve

[0151] 39 On / off valve 41 Primary pressure gauge

[0152] 42 Secondary pressure gauge 44 Feeder

[0153] 45 Hopper 46 Injection Material Detection Sensor

Claims

1. An injection molding machine, characterized in that, include: A heating cylinder, which is equipped with a gas injection port; A screw, configured to be driven within the heating cylinder; A gas supply device that supplies gas to the gas injection port; and Control mechanism, The heating cylinder is divided into multiple zones based on the shape variation of the screw thread. From upstream to downstream, these zones include at least a first compression / metering zone where molten injection material is compressed, a starvation zone where the pressure of the injection material decreases, and a second compression / metering zone where the injection material is compressed again. The gas injection port is located in the starvation zone. The gas supply device includes: A gas supply source that supplies gas; A pressure regulating mechanism that adjusts the primary pressure of the gas from the gas supply source to a secondary pressure; A check valve, which is located downstream of the pressure regulating mechanism; and A secondary pressure detection mechanism detects the secondary pressure downstream of the check valve. The gas injection port is connected downstream of the check valve, and the secondary pressurized gas is supplied to the gas injection port. The control mechanism includes a set pressure for the gas under secondary pressure, a first threshold value of 0.1 MPa to 1.5 MPa, and a second threshold value of 0.1 MPa to 1.5 MPa. The normal pressure range of the secondary pressure is greater than the value obtained by subtracting the second threshold from the set pressure and lower than the value obtained by adding the first threshold to the set pressure. When the secondary pressure deviates from the normal pressure range, it is judged as abnormal.

2. The injection molding machine according to claim 1, characterized in that, The control mechanism has a third threshold greater than the first threshold. When the secondary pressure is greater than the normal pressure range and the secondary pressure is lower than the value obtained by adding the third threshold to the set pressure, the control mechanism issues a danger alarm for material leakage at the gas injection port.

3. The injection molding machine according to claim 1, characterized in that, The control mechanism has a third threshold greater than the first threshold. When the secondary pressure is greater than or equal to the value obtained by adding the third threshold to the set pressure, the control mechanism stops the molding cycle after the molding cycle is completed.

4. The injection molding machine according to claim 1, characterized in that, The gas supply device has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port. The control mechanism has a third threshold greater than the first threshold. When the secondary pressure is greater than or equal to the value obtained by adding the third threshold to the set pressure, the control mechanism closes the opening and closing mechanism and stops the molding cycle after it is completed.

5. The injection molding machine according to claim 1, characterized in that, The control mechanism includes a pressure control mechanism for controlling the pressure regulating mechanism and a third threshold greater than the first threshold. When the secondary pressure is greater than the normal pressure range and the secondary pressure is lower than the value obtained by adding the third threshold to the set pressure, the pressure control mechanism implements pressure reduction control so that the secondary pressure becomes the normal pressure range.

6. The injection molding machine according to claim 5, characterized in that, During the first stabilization time from the start of the pressure reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism stops the molding cycle upon completion of the ongoing molding cycle.

7. The injection molding machine according to claim 5, characterized in that, The gas supply device has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port. During the first stabilization period following the start of the pressure reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism closes the opening and closing mechanism and stops the molding cycle upon completion of the ongoing molding cycle.

8. The injection molding machine according to claim 5, characterized in that, The heating cylinder is equipped with a feeder that adjusts the supply amount of the injection material. During the first stabilization period following the commencement of the pressure reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism implements a supply reduction control to control the feeder and reduce the supply of injection material.

9. The injection molding machine according to claim 1, characterized in that, The heating cylinder is equipped with a feeder that adjusts the supply amount of the injection material. The control mechanism has a third threshold greater than the first threshold. When the secondary pressure is greater than the normal pressure range and the secondary pressure is lower than the value obtained by adding the third threshold to the set pressure, the control mechanism implements a supply reduction control to control the feeder to reduce the supply of injection material.

10. The injection molding machine according to claim 8, characterized in that, During the second stabilization period following the start of the supply reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism stops the molding cycle upon completion of the ongoing molding cycle.

11. The injection molding machine according to claim 9, characterized in that, During the second stabilization period following the start of the supply reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism stops the molding cycle upon completion of the ongoing molding cycle.

12. The injection molding machine according to claim 8, characterized in that, The gas supply device has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port. During the second stabilization period following the start of the supply reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism closes the opening and closing mechanism and stops the molding cycle upon completion of the ongoing molding cycle.

13. The injection molding machine according to claim 9, characterized in that, The gas supply device has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port. During the second stabilization period following the start of the supply reduction control, if the secondary pressure remains above the normal pressure range, the control mechanism closes the opening and closing mechanism and stops the molding cycle upon completion of the ongoing molding cycle.

14. The injection molding machine according to claim 1, characterized in that, When the secondary pressure is less than the normal pressure range and the rate of decrease of the secondary pressure becomes above the fourth threshold, the control mechanism stops the molding cycle after the molding cycle is completed.

15. The injection molding machine according to claim 1, characterized in that, The gas supply device has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port. When the secondary pressure is less than the normal pressure range and the rate of decrease of the secondary pressure becomes above the fourth threshold, the control mechanism closes the opening and closing mechanism and stops the molding cycle after it is completed.

16. The injection molding machine according to claim 1, characterized in that, The heating cylinder is equipped with a feeder that adjusts the supply amount of the injection material. The control mechanism has a fourth threshold and a fifth threshold greater than the second threshold. When the secondary pressure is greater than the value obtained by subtracting the fifth threshold from the set pressure and the rate of decrease of the secondary pressure becomes greater than the fourth threshold, the control mechanism implements a supply increase control to control the feeder to increase the supply of injection material.

17. The injection molding machine according to claim 16, characterized in that, During a predetermined period from the start of the supply increase control or during the fourth stabilization time from the start of the supply increase control, if the rate of decrease of the secondary pressure is temporarily higher than the fourth threshold, the control mechanism stops the molding cycle after the ongoing molding cycle is completed.

18. The injection molding machine according to claim 16, characterized in that, The gas supply device has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port. During a predetermined period from the start of the supply increase control or during the fourth stabilization period from the start of the supply increase control, if the rate of decrease of the secondary pressure is temporarily higher than the fourth threshold, the control mechanism closes the opening and closing mechanism and stops the molding cycle after the ongoing molding cycle is completed.

19. The injection molding machine according to claim 1, characterized in that, The control mechanism has a fifth threshold greater than the second threshold. When the secondary pressure is below the value obtained by subtracting the fifth threshold from the set pressure, the control mechanism stops the molding cycle after the molding cycle is completed.

20. The injection molding machine according to claim 1, characterized in that, The gas supply device has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port. The control mechanism has a fifth threshold greater than the second threshold. When the secondary pressure is below the value obtained by subtracting the fifth threshold from the set pressure, the control mechanism closes the opening and closing mechanism and stops the molding cycle after it is completed.

21. The injection molding machine according to claim 1, characterized in that, The control mechanism has a fourth threshold and a fifth threshold greater than the second threshold. When the secondary pressure is lower than the normal pressure range but greater than the value obtained by subtracting the fifth threshold from the set pressure, and the rate of decrease of the secondary pressure is lower than the fourth threshold, the control mechanism issues an alarm urging the replacement of the gas supply source.

22. The injection molding machine according to claim 1, characterized in that, The gas supply device includes multiple gas supply sources and a gas supply source switching mechanism, which selects and switches from the multiple gas supply sources to use as the gas supply source for the application. The control mechanism has a fourth threshold and a fifth threshold greater than the second threshold. When the secondary pressure is lower than the normal pressure range but greater than the value obtained by subtracting the fifth threshold from the set pressure, and the rate of decrease of the secondary pressure is lower than the fourth threshold, the control mechanism uses the gas supply source switching mechanism to switch the currently used gas supply source to another gas supply source.

23. The injection molding machine according to claim 1, characterized in that, The control mechanism includes a pressure control mechanism for controlling the pressure regulating mechanism, a fourth threshold, and a fifth threshold greater than the second threshold. When the secondary pressure is lower than the normal pressure range but greater than the value obtained by subtracting the fifth threshold from the set pressure, and the rate of decrease of the secondary pressure is lower than the fourth threshold, the pressure control mechanism is used to implement pressure increase control so that the secondary pressure becomes the normal pressure range.

24. The injection molding machine according to claim 23, characterized in that, During the third stabilization period following the start of the pressure increase control, if the secondary pressure is lower than the normal pressure range and remains at a value greater than the value obtained by subtracting the fifth threshold from the set pressure, the control mechanism issues an alarm urging the replacement of the gas supply source.

25. The injection molding machine according to claim 23, characterized in that, The gas supply device includes multiple gas supply sources and a gas supply source switching mechanism, which selects and switches from the multiple gas supply sources to use as the gas supply source for the application. During the third stabilization period from the start of the pressure increase control, if the secondary pressure is lower than the normal pressure range and remains at a value greater than the value obtained by subtracting the fifth threshold from the set pressure, the control mechanism uses the gas supply source switching mechanism to switch the currently used gas supply source to another gas supply source.

26. The injection molding machine according to any one of claims 1 to 25, characterized in that, The gas supply device includes: a plurality of gas supply sources; a gas supply source switching mechanism that selects and switches from the plurality of gas supply sources to one gas supply source as the object to be used; and a primary pressure detection mechanism that detects the primary pressure of the gas from the gas supply sources. The control mechanism detects a decrease in the pressure of the gas supply source by comparing the difference between the primary pressure and the set pressure or the secondary pressure. When a decrease in the pressure of the gas supply source is detected, the gas supply source switching mechanism switches the currently used gas supply source to another gas supply source.

27. The injection molding machine according to claim 1, characterized in that, The injection molding machine is equipped with an injection material detection mechanism to confirm the supply of injection material to the heating cylinder. When the injection material detection mechanism detects that the injection material has been used up due to an interruption in the injection process, it stops the molding cycle after the ongoing molding cycle is completed.

28. The injection molding machine according to claim 1, characterized in that, The injection molding machine is equipped with an injection material detection mechanism to confirm the supply of injection material to the heating cylinder. The gas supply device has an opening and closing mechanism in the gas pipe or gas injection section that supplies the secondary pressure gas to the gas injection port. When the injection material detection mechanism detects that the injection material has been used up due to an interruption in the injection process, it closes the opening and closing mechanism and stops the molding cycle after the ongoing molding cycle is completed.

29. A control method for an injection molding machine, wherein, The injection molding machine includes: A heating cylinder, which is equipped with a gas injection port; A screw, configured to be driven within the heating cylinder; and A gas supply device supplies gas to the gas injection port. The heating cylinder is divided into multiple zones based on the shape variation of the screw thread. From upstream to downstream, these zones include at least a first compression / metering zone where molten injection material is compressed, a starvation zone where the pressure of the injection material decreases, and a second compression / metering zone where the injection material is compressed again. The gas injection port is located in the starvation zone. The gas supply device includes: A gas supply source that supplies gas; A pressure regulating mechanism that adjusts the primary pressure of the gas from the gas supply source to a secondary pressure; A check valve, which is located downstream of the pressure regulating mechanism; and A secondary pressure detection mechanism detects the secondary pressure downstream of the check valve. The gas injection port is connected downstream of the check valve, and the secondary pressurized gas is supplied to the gas injection port. The control method for the injection molding machine is characterized by the following: A first threshold value of 0.1 MPa to 1.5 MPa and a second threshold value of 0.1 MPa to 1.5 MPa are set for the gas under the secondary pressure. The pressure range that is greater than the value obtained by subtracting the second threshold from the set pressure and lower than the value obtained by adding the first threshold to the set pressure is defined as the normal pressure range. When the secondary pressure deviates from the normal pressure range, it is judged as abnormal.

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