Method and system for injection molding

Abstract

The present invention relates to a method for injection molding a hollow object with a system, comprising: (i) waiting for a cycle start signal from said press; (ii) upon receiving the cycle start signal, driving the actuator so as to regulate the flow of molten material towards the cavity by moving the shutter; (iii) after or simultaneously with a specific time, sending a fluid injection signal to the fluid injection unit to command the fluid injection unit to activate the fluid injector to inject pressurized fluid into the cavity; (iv) after, or simultaneously, driving the actuator in order to regulate the flow of molten material that the pressurized fluid is removing it from the cavity and pushing it towards the press by moving the shutter with positional continuity and / or according to a programmed dynamic profile. The invention also relates to an injection molding system.

Description

Technical Field

[0001] The present invention relates to an improved injection molding system and method, in which, for example, water injection technology (WIT) is used. Background Art

[0002] WIT is a technology in the plastic injection industry that allows obtaining objects with complex hollow geometries by injecting water under high pressure. This method is used to reduce the final weight of the part and shorten the cooling time in the molding cycle / cycle. See, for example, DE102006048788 and Figure 1 the solutions in.

[0003] The known system 100 includes a mold 10 having a cavity 12. In the mold 10, a hot runner 14 is installed, and the hot runner 14 is equipped with one or more nozzles 16 facing the cavity 12. Each nozzle 16 can be closed by a corresponding opening / closing member 18 to prevent or allow the molten material to flow towards the cavity 12, and one or more water injectors 20 are installed to inject pressurized water into the cavity 12.

[0004] Each opening / closing member 18 is pneumatically or hydraulically operated, so the corresponding nozzle 16 can only be in two states: fully open or fully closed.

[0005] A press 90 outside the mold 10 includes a mechanism 92 (such as a worm) for injecting molten material into the hot runner 14 under pressure and an electronic control unit 94 for sending a signal S. The signal S only indicates the start of the injection stage, that is, the molten material flows from the press 90 through the hot runner 14 to the mold 10.

[0006] The system 100 then includes an injection unit 74, which is outside the press 90, is independent, and implements the WIT technology. The injection unit 74 includes:

[0007] · An electronic control unit 80 for receiving the signal S and reacting to it,

[0008] · A mechanism 82 for driving the opening / closing member 18, which only allows or prevents the molten material from flowing towards the cavity 12 by fully closing or fully opening the nozzle 16, and

[0009] · A mechanism 84 for driving the water injector 20.

[0010] The electronic control unit 80 that controls the operation of the mechanisms 82, 84 is configured to wait for the signal S from the electronic control unit 94. Once the signal S is received, the electronic control unit 80 drives the opening / closing member 18 via the mechanism 82 to send the molten material with the maximum flow rate towards the cavity 12. Once the injection is completed, the electronic control unit 80 moves the opening / closing member 18 to fully close the nozzle 16.

[0011] After a certain time, the electronic control unit 80 simultaneously performs the following operations:

[0012] Drive the syringe 20 to inject pressurized water into the cavity 12, and

[0013] Return the opening and closing member 18 to the open position of the nozzle 16 (so-called push-back phase), so that the injected water removes the uncured material from the object to be molded and pushes it into the hot runner 14 and towards the press 90.

[0014] The injection screw 92 does not provide resistance, so the material removed from the inside of the object to be molded is recycled.

[0015] The electronic control unit 80 starts the syringe 20 through a timer, making it quite difficult for the operator of the system 100 during the programming of the molding process: he has to coordinate the start sequence of the opening and closing member 18 and the syringe 20 through trial and error. In practice, the process is gradually optimized by gradually increasing the amount of molten material injected into the cavity 12 and simultaneously metering the amount of water introduced via the syringe 20.

[0016] After a certain time still determined experimentally, the electronic control unit 80 must close the nozzle 16 by moving the opening and closing member 18. In fact, if water reaches the hot runner 14, it will cool the hot runner 14, thus losing energy efficiency. If water reaches the press 90, the situation will be even worse, because the water may interact with the molten material there and cause an explosion or a steam burst. If this happens, the work cycle must be interrupted and the water in the press 90 must be treated / discarded.

[0017] The electronic control unit 80 can only move the opening and closing member 18 by driving fluid-operated actuators installed in the mold 10 / cavity 12, and these actuators themselves are inaccurate and non-modular (the nozzle 16 can only be fully opened or fully closed). This results in a rough control of the position of the opening and closing member 18, making it difficult to obtain a good final product. If set incorrectly or not fully coordinated, the injection of water may start when the opening and closing member 18 is still closed, resulting in overpressure in the mold 10 / cavity 12 and thus leakage of steam and high-temperature materials.

[0018] In addition, the electronic control unit 80 cannot control the pressure of the water when it is injected into the mold 10 / cavity 12, but can only set the pressure value of the water when it leaves the unit 74. Therefore, the regulation of the water pressure even inside the cavity 12 is rough and inaccurate, also because the electronic control unit 80 can only intervene by changing the open / closed state of the nozzle 16. Therefore, during the process, the pressure of the liquid changes significantly and continuously. Summary of the Invention

[0019] The main object of the present invention is to improve the prior art.

[0020] Another object of the present invention is to improve the interaction and / or throughput of WIT technology (or equivalent technology) applied to an injection molding system.

[0021] The present invention is defined in the appended claims, where the dependent claims define advantageous variants.

[0022] One aspect of the present invention relates to a method for injection molding a hollow object via a system, the system comprising:

[0023] - a mold, the mold comprising:

[0024] · a cavity,

[0025] · a hot runner for introducing a molten (e.g., plastic) material into the mold, the hot runner being equipped with:

[0026] o a nozzle facing the cavity, and

[0027] o a nozzle opening / closing member for regulating the flow of the molten material towards the cavity,

[0028] · an actuator for moving the opening / closing member, and

[0029] · a fluid injector (liquid or gas or vapor) for injecting a pressurized fluid into the cavity and removing material from the object to be molded and creating an internal cavity (in particular a central cavity) in the object to be molded by the action of the fluid;

[0030] - a press coupled to the mold for injecting the molten material into the mold (and preferably also operating components of the mold);

[0031] - a fluid injection unit outside the press, the fluid injection unit being configured to drive the fluid injector,

[0032] The method has the following steps:

[0033] (i) Waiting for a cycle start signal from the press;

[0034] (ii) After receiving the cycle start signal, driving the actuator to regulate the flow of the molten material towards the cavity by moving the opening / closing member (e.g., linearly);

[0035] (iii) After a specific time, or simultaneously, sending a fluid injection signal to the injection unit to command the injection unit to start the fluid injector so as to inject the pressurized fluid into the cavity;

[0036] (iv) After a specific time, or simultaneously, drive the actuator to regulate the flow of the pressurized fluid that is removing it from the cavity (and from the object) and pushing it towards the press by moving the opening / closing member with position continuity and / or according to a programmed dynamic curve.

[0037] Moving the opening / closing member continuously means that the opening / closing member can be finely moved to any position between its stroke limits, unlike an opening / closing member that can only assume two opposite end-of-travel positions. Continuity is understood as position (space) continuity.

[0038] This method provides precise control of the position of the opening / closing member, thus providing precise control of the nozzle opening, and thus providing precise control of the dynamics of emptying the molded object by the injected fluid.

[0039] In an advantageous variant of this method, these steps are performed electronically (e.g., by discrete component circuits) via software and / or by an electronic control unit external to the press and the injection unit. Thus, this method can be easily applied to pre-existing systems, such as Figure 1 the systems in

[0040] Furthermore, as described below, the third electronic control unit allows useful functions to be added to the system.

[0041] In an advantageous variant of this method, during the injection of the fluid into the mold, control signals are generated and sent to the press or the injection unit according to signals received respectively from the injection unit or the press.

[0042] The cycle start signal may include:

[0043] - A signal indicating the start of the injection of the molten material into the mold; and / or

[0044] - A signal indicating the state of the mechanism in the press for injecting the molten material under pressure (e.g., the position of the injection screw); and / or

[0045] - A signal indicating the pressure of the material when it leaves the press.

[0046] In an advantageous variant of this method, during the injection of the fluid into the mold, the position of the opening / closing member is controlled according to the following detected conditions or process parameters:

[0047] - Conditions or process parameters detected in the injection unit, such as the pressure or velocity or flow rate of the fluid when it leaves the injection unit; and / or

[0048] - Conditions or process parameters detected in the press, in particular controlling the position of the opening and closing member based on signals indicating the state of the mechanism for injecting molten material under pressure in the press (e.g., the position of the injection screw) and / or signals indicating the pressure and / or temperature of the material leaving the press;

[0049] - Conditions or process parameters detected in the mold, such as the pressure of the fluid inside the cavity, the flow rate of the fluid when entering the cavity, the amount of the fluid present in the cavity, the temperature of the fluid present in the cavity.

[0050] In a convenient variant of the method:

[0051] Receiving and processing signals from the press; and

[0052] Generating a signal based on the received signal and sending it to the injection unit to regulate the flow rate of the fluid or terminate the injection of the fluid.

[0053] This avoids a large influx into the hot runner and, even worse, into the press.

[0054] In particular:

[0055] Receiving a signal from the press, such as a signal indicating the position of the injection screw; and

[0056] Processing the signal to calculate:

[0057] The percentage (%) of evacuation of the molded object currently present in the cavity due to the injected fluid; and / or

[0058] The injection volume of the fluid; and / or

[0059] The pressure of the injected fluid.

[0060] More specifically, generating a signal based on the calculated percentage and sending it to the injection unit to regulate the flow rate of the fluid or terminate the injection of the fluid.

[0061] In an advantageous variant of the method, generating a signal based on the position of the opening and closing member and sending it to the injection unit to regulate the flow rate of the fluid or terminate the injection of the fluid.

[0062] Another aspect of the present invention relates to a molding system, comprising:

[0063] - A mold, which includes:

[0064] · A cavity,

[0065] · A hot runner for introducing molten material into the mold, and the hot runner is equipped with:

[0066] o A nozzle facing the cavity, and

[0067] o A nozzle opening / closing member for adjusting the flow of the molten material towards the cavity,

[0068] · An actuator for continuously / successively / sequentially moving (linearly) the opening / closing member, and

[0069] · A fluid syringe (liquid or gas or vapor) for injecting a pressurized fluid into the cavity and removing material from the object to be molded and creating an internal cavity (especially a central cavity) in the object to be molded by the action of the fluid;

[0070] - A press, which is connected to the mold to operate the components of the mold and inject the molten material into the mold, and the press includes:

[0071] A mechanism for injecting the molten material into the hot runner under pressure, and

[0072] A first electronic control unit configured to issue a cycle start signal indicating the molten material injection process and / or the state of the press at the start of the injection cycle;

[0073] - A fluid injection unit, which includes a second electronic control unit independent of the press, and the second electronic control unit is configured to receive a fluid injection signal and thus drive the fluid syringe to inject the pressurized fluid into the cavity and remove the molten material from the cavity by means of the fluid;

[0074] - A third electronic control unit, wherein,

[0075] · The third electronic control unit is outside the press (and the injection unit),

[0076] · The third electronic control unit is different from the second electronic control unit,

[0077] · The third electronic control unit is connected to the first electronic control unit to receive the cycle start signal, and

[0078] · The third electronic control unit is configured to:

[0079] Drive the actuator in response to the cycle start signal to adjust the flow of the molten material towards the cavity by continuously moving the opening / closing member, and send a fluid injection signal to the second electronic control unit to command the second electronic control unit to start the fluid syringe.

[0080] With this architecture, the third electronic control unit can manage the actuation and / or dynamics of each opening / closing member and each fluid injector, so that the control of the entire molding process is more precise, repeatable, easy to program and safe. In particular, it is no longer necessary to program the entire molding process with the original timing provided in the second electronic control unit. And the limitations or inaccuracies caused by the poor flexibility of the second electronic control unit can be eliminated from the system (especially its original mechanism for driving the opening / closing member (which is bypassed) and its original mechanism for processing the cycle start signal (which is bypassed)).

[0081] The second electronic control unit may include a mechanism for driving the syringe and / or a receiving mechanism for receiving the cycle start signal. The third electronic control unit for driving the syringe may be connected to the mechanism for driving the syringe or to the receiving mechanism. In this case, the third electronic control unit is configured to send a fluid injection signal to the second electronic control unit.

[0082] In particular, the architecture of the third electronic control unit may be different from that of the second electronic control unit, so that functions independent of the limitations of the second electronic control unit can be added to the system.

[0083] Preferably, the third electronic control unit is configured to:[[]]

[0084] Send a fluid injection signal to the second control unit, and then

[0085] Drive the actuator to regulate the flow of the molten material from the cavity to the press by continuously moving the opening / closing member.

[0086] In this way, the limitations associated with the rough position control of the opening / closing member by the second electronic control unit are overcome, which is advantageous both during the injection of the molten material and during the extraction of the molten material when the fluid is injected into the mold. In fact, during the back-push phase, the smooth control of the opening of the opening / closing member not only allows the precise regulation of the water pressure inside the mold, thus improving the performance of the syringe, but also improves the dynamics of the object evacuation and the final quality of the object, because the water flow from the mold can be finely regulated to adapt to the characteristics of the object and / or the evacuation that one wants to perform. For example, consider the case where one needs to evacuate a cavity of an object that has a variable cross-section along the object. The on / off control of the opening / closing member cannot guarantee the best evacuation dynamics for each cross-section segment, while smooth control can.

[0087] Preferably, the opening / closing member is associated with an electric drive device capable of continuously and precisely moving the opening / closing member, and the third electronic control unit is configured to send an electric signal to the drive device to continuously change the position of the opening / closing member.

[0088] Between the third electronic control unit and the second electronic control unit, there is preferably a first data communication channel, which is preferably bidirectional.

[0089] For example, the fluid injection signal generated by the third electronic control unit propagates on the first data communication channel.

[0090] Between the third electronic control unit and the first electronic control unit, there is preferably a second data communication channel, which is preferably bidirectional.

[0091] For example, the cycle start signal sent from the first electronic control unit to the third electronic control unit propagates on the second data communication channel.

[0092] Preferably, the first and / or second data communication channel is a signal cable, a data bus or a wireless network.

[0093] With a bidirectional channel, closed-loop control can be advantageously implemented in the system.

[0094] Since the third electronic control unit is connected to the first electronic control unit and the second electronic control unit, the third electronic control unit can generate a control signal based on the signals received from the other two electronic control units and send it to one or each of the other two electronic control units. Therefore, for example, the third electronic control unit can affect the activities of the second electronic control unit according to the conditions or events detected in the first electronic control unit, or vice versa.

[0095] Therefore, for example, the start and / or stop of the fluid syringe can be carried out according to a more complex logic considering more parameters or process conditions, which is beneficial to the quality of the final molded product.

[0096] Or, for example, the position of the opening and closing member can be controlled by the third electronic control unit according to a more complex logic considering the parameters or process conditions inherent in or detected by the first and / or second electronic control units.

[0097] The signals sent on the first and / or second data communication channel are analog signals or digital signals.

[0098] For more complex control, the third electronic control unit is preferably configured to receive the signal generated by the first electronic control unit and react to it, and the signal may include:

[0099] A signal indicating the start of the injection of the molten material into the mold; and / or

[0100] A signal indicating the state of the mechanism for injecting the molten material under pressure (such as the position of the injection screw); and / or

[0101] A signal indicating the pressure of the material as it exits the press.

[0102] Advantageously, the third electronic control unit is preferably configured to:

[0103] - Read a signal indicating the position of the injection screw installed in the press for pushing the molten material into the mold; and

[0104] During the injection of the fluid, perform the following operations:

[0105] - Calculate the actual evacuation percentage (%) of the object present in the cavity due to the injected fluid and / or the amount of the injected fluid and / or the pressure of the injected fluid; and

[0106] - Send a signal to the second electronic control unit to adjust the flow rate of the fluid or terminate the injection of the fluid based on the calculated percentage or result.

[0107] Advantageously, the third electronic control unit is configured to read and process a signal indicating the position of the opening and closing member, and based on such a signal, send a signal to the second electronic control unit to adjust the flow rate of the fluid or terminate the injection of the fluid. Description of the Drawings

[0108] The advantages of the present invention will become more apparent from the following description of the preferred system, wherein:

[0109] Figure 1 A schematic diagram of a known injection molding system is shown;

[0110] Figure 2 A schematic diagram of an injection molding system according to the present invention is shown;

[0111] Figures 3 - 5 A position curve followed by one or more opening and closing members during the injection cycle is shown.

[0112] In the drawings: like reference numerals represent like components, and arrows indicate signal lines. Detailed Description

[0113] Figure 2 The system MC of Figure 1 includes a mold 10, an identical press 90, and an identical unit 74 having a similar on-board mounting structure.

[0114] Unlike Figure 1 the known system in

[0115] One or each signal line can be, for example, an electrical signal cable, a data bus or a wireless channel.

[0116] The electronic control unit 34 is configured to wait for a signal S from the press 90 and then successively generate and send signals S2, S5, S6, S8 to the actuator 98, and successively generate and send signals S3, S7 to the electronic control unit 80.

[0117] The signal S generated by the press 90 indicates, for example, the start of the injection of the molten material or the state of the mechanism 92, such as the position of the injection screw.

[0118] The electronic control unit 34 is configured to successively adjust the position of the opening and closing member 18 via signals S2, S5, S6. For this purpose, the actuator 98 is preferably electric (such as a rotary motor or a linear actuator).

[0119] The lines carrying signals S3, S7 can be connected to the control unit 80 or the mechanism 84 (see the options in the dashed lines).

[0120] The electronic control unit 34 is configured to command the electronic control unit 80 to start or stop the syringe 20 via signals S3, S7 respectively.

[0121] Basically, in the system MC, the injection cycle has the following steps:

[0122] 1): The press 90 controls and determines the start of the cycle. When the press 90 starts to inject the molten material into the mold 10, the press emits a signal S;

[0123] 2): When the electronic control unit 34 receives the signal S from the press 90, the electronic control unit generates a signal S2 to drive the actuator 98 so as to move the opening and closing member 18 to open the nozzle 16. Now the introduction of the molten material into the cavity 12 starts. The electronic control unit 34 can control the movement of the opening and closing member 18 according to programmed profiles along the stroke of the opening and closing member 18, such as the speed and / or position profiles along its stroke;

[0124] 3): After a specific time, the injection of the molten material ends. In most applications, the entire cavity 12 is occupied by the molten material. The press 90 generates a warning signal S4 that the injection has ended;

[0125] 4): The electronic control unit 34 reads the signal S4 and reacts in the following ways:

[0126] - Generate and send a signal S3 to the electronic control unit 80 to command it to start the fluid injection through the syringe 20; and

[0127] - Generate a signal S5 to drive the opening / closing member 18 so that the nozzle 16 is fully or partially opened. The opening / closing member 18 does not necessarily close completely in step 2), it can also be partially closed. In some cases, it can also be closed and reopened before step 5). The dynamic characteristics of the opening / closing member 18 allow the filling of the cavity 12 with the molten material to be managed in a desired manner;

[0128] 5): As soon as the electronic control unit 80 receives the signal S3, it activates the syringe 20. The pressurized fluid enters the cavity 12 and pushes the molten material backward into the hot runner 14 and the press 90. The material is removed by the fluid to create an internal cavity in the molded object. In this step, the mechanism 92 does not generate a thrust force, so the excess material removed from the molded object by the fluid can re-enter the press 90, and removing this excess material forms a central cavity in the object;

[0129] 6): During the fluid injection, the electronic control unit 34 can optionally adjust the position of the opening / closing member 18 with the signal S6 in order to control the fluid pressure inside the cavity 12 and / or the dynamics of the molten material re-entering the press 90. The possibility of adjusting the opening / opening state of the nozzle 16 via the position of the opening / closing member 18 allows the flow rate / velocity of the material re-entering the press 90 to be programmed and locally changed. This is very useful, for example, in those applications where multiple objects to be molded have different volumes / capacities or shapes, such that the volume / amount of material re-entering the press 90 is not the same for each hot runner 14; in this way, the material present in the mold and the hot runner acts as a brake / obstacle to the water thrust;

[0130] 7): The electronic control unit 34 continuously processes to determine the moment when the desired amount of removed material re-enters the press 90. This moment is determined by a timer, for example, or preferably calculated by detecting the state of the mechanism 92 (such as the position of the injection screw). When the screw pushed by the removed material has moved backward a specific stroke, this means that a corresponding determined volume of material has re-entered the press 90. Then, the electronic control unit 34 compares the position of the screw with a threshold value, and if the threshold value is reached, it proceeds to step 8);

[0131] 8): The electronic control unit 34 sends a signal S7 to the electronic control unit 80 to command the electronic control unit 80 to stop injecting the fluid through the syringe 20 and adjust the position of the opening / closing member 18 with the signal S8 to close the nozzle 16;

[0132] 9): Drain the fluid still present inside the molded object;

[0133] 10): The press 90 opens the mold 10 / cavity 12, removes the molded object, the press 90 closes the mold 10 / cavity 12 and the cycle starts again.

[0134] The fluid injected by the syringe 20 is a liquid such as water, or a gas such as CO2 or nitrogen, or water vapor.

[0135] In the mold 10, there may also be a plurality of hot runners 14 with associated opening and closing members 16. All of these are controlled by the electronic control unit 34, even in different ways.

[0136] The mold may also have a plurality of cavities (referred to as a series mold) with different shapes, sizes, and thicknesses. Each cavity requires different injection settings and adjustments.

[0137] In one variant, the unit 74 can be simplified by removing the mechanism 82 because they are not used.

[0138] Figures 3 - 5 Shown are some examples of position / time curves of the positions of various opening and closing members 18 during the injection cycle. The curves of different opening and closing members can be distinguished by the type of line strokes.

[0139] The end of the opening stroke of the opening and closing member 18 (the nozzle is fully open) is represented by Q, and the horizontal axis corresponds to the zero position (the nozzle is fully closed). The stage of opening the opening and closing member 18 and filling the mold 10 with molten material is the interval 210, while the stage of closing the opening and closing member 18 and packing the molten material is the interval 212.

[0140] The dynamics of the opening stage are known, in which the opening and closing member 18 can move in different ways, at different speeds, with pauses, accelerations, and decelerations. The closing and packing stage also shows different movement / motion patterns of the opening and closing member, including changes in speed, acceleration, deceleration, and pause.

[0141] The syringe 20 is activated during the retraction phase (represented by 214), and the retraction phase occurs at any time during the injection process as long as there is molten material in the cavity 12. Generally, this approximately coincides with the start of the interval 212.

[0142] Note the difference from the system 100.

[0143] In the system 100, the unit 74 can only perform the opening stage and the closing stage of the opening and closing member 18 by one movement, and thus also performs it by one movement during the retraction phase 214.

[0144] On the contrary, the system MC allows the opening and closing member to be characterized by speed changes, accelerations, decelerations, and pauses during the retraction phase. Using this management of the opening and closing member during the retraction phase allows the braking effect exerted by the molten material present in the cavity 12 and / or the hot runner 14 on the injection fluid to be advantageously utilized.

[0145] Other opening and / or closing curves that can be implemented by the actuator 98 for one or each of the opening and closing members 18 are described and shown in the following documents:

[0146] PCT / IB2019 / 053936, IT102017000037002, IT102016000080198, IT102016000055364, IT102015000008368, ITTO2014A001030, ITTO2014A001021, ITTO2014A000701, WO2012 / 074879A1, WO2012 / 087491A1 and WO2018 / 020177A1.

Claims

1. A method for injection molding a hollow object using a system, the system comprising: - A mold, comprising: Cavity, A hot runner, which is used to introduce molten material into the mold, and the hot runner is equipped with: a nozzle directed toward the cavity, and a nozzle opening and closing member for regulating the flow of molten material toward the cavity, an actuator for moving the opening and closing member, and a fluid injector for injecting a pressurized fluid into the mold cavity and removing material from the molded object by the action of the pressurized fluid to create an internal cavity in the molded object; - a press coupled to the mold for injecting molten material into the mold; - a fluid injection unit external to the press, the fluid injection unit being configured to drive the fluid injector, The method has the following steps: (i) waiting for a cycle start signal from the press; (ii) upon receiving the cycle start signal, driving the actuator to adjust the flow of molten material toward the cavity by moving the opening and closing member; (iii) after a specific time, or simultaneously, sending a fluid injection signal to the fluid injection unit to instruct the fluid injection unit to activate the fluid injector, thereby injecting the pressurized fluid into the cavity; (iv) after a certain time, or simultaneously, driving the actuator to regulate the flow of molten material being removed from the cavity and pushed toward the press by the pressurized fluid by moving the shutter in a manner that achieves position continuity and / or according to a programmed dynamic curve.

2. The method according to claim 1, wherein: The multiple steps are performed electronically via software and / or by an electronic control unit external to the press and the fluid injection unit.

3. The method according to claim 1 or 2, wherein: During the injection of the pressurized fluid into the mold, a control signal is generated according to a signal received from the fluid injection unit or from the press and the generated control signal is sent to the press or the fluid injection unit, respectively.

4. A method according to any one of the preceding claims, wherein: During injection of the pressurized fluid into the mold, the position of the shutter is controlled according to the pressure or velocity or flow rate of the pressurized fluid when it leaves the fluid injection unit.

5. A method according to any one of the preceding claims, wherein: During injection of the pressurized fluid into the mold, the position of the shutter is controlled according to a signal indicating a state of a mechanism installed in the press and configured to inject molten material under pressure into the mold.

6. The method according to claim 5, wherein: During the injection of the pressurized fluid into the mold, the position of the shutter is controlled according to a signal indicating a position of an injection screw installed in the press and configured to inject pressurized molten material into the mold.

7. A method according to any one of the preceding claims, wherein: During the injection of the pressurized fluid into the mold the following operations are performed: detecting a state of a mechanism installed in the press and configured to inject molten material under pressure into the mold; calculating a percentage of the molded object currently located in the mold cavity that is emptied due to the injected pressurized fluid based on the detected state; as well as A signal is generated according to the percentage and is sent to the fluid injection unit to adjust the flow rate of the pressurized fluid or terminate the injection of the pressurized fluid.

8. An injection molding system comprising: - A mold, comprising: Cavity, A hot runner, which is used to introduce molten material into the mold, and the hot runner is equipped with: o a nozzle directed toward the cavity, and o a nozzle opening and closing member for regulating the flow of molten material toward the cavity, an actuator for moving the shutter in such a way as to achieve positional continuity, and a fluid injector for injecting a pressurized fluid into the mold cavity and removing material from the molded object by the action of the pressurized fluid to create an internal cavity in the molded object; - a press coupled to the mold to manipulate the components of the mold and to inject molten material into the mold, the press comprising: a mechanism for injecting molten material under pressure into the hot runner, and a first electronic control unit configured to issue a cycle start signal indicating a status of a molten material injection process and / or a status of a press machine at the start of an injection cycle; a fluid injection unit comprising a second electronic control unit independent of the press, the second electronic control unit being configured for receiving a fluid injection signal and for driving the fluid injector accordingly so as to inject a pressurized fluid into the cavity and to remove molten material from the cavity by means of the pressurized fluid; - a third electronic control unit, wherein the third electronic control unit is external to the press and the fluid injection unit, the third electronic control unit is different from the second electronic control unit, the third electronic control unit is connected to the first electronic control unit to receive the cycle start signal, and The third electronic control unit is configured to: driving the actuator in response to the cycle start signal to adjust the flow of molten material toward the cavity by moving the shutter, and The fluid injection signal is sent to the second electronic control unit to command the second electronic control unit to activate the fluid injector.

9. The system according to claim 8, wherein: The opening and closing member is associated with an electric actuator capable of moving the opening and closing member in a manner that enables positional continuity, and the third electronic control unit is configured to send an electric signal to the electric actuator in order to change the position of the opening and closing member in a manner that enables positional continuity.

10. The system according to claim 9, wherein: The third electronic control unit is configured to: - reading a signal indicative of the position of an injection screw mounted in the press and used to push molten material into the mold; and - During the injection of said pressurized fluid, calculate: o the percentage of the object present in the cavity that is actually emptied due to the injected pressurized fluid, and / or o the amount of the injected pressurized fluid and / or the pressure of the injected pressurized fluid; as well as - sending a signal to the second electronic control unit to adjust the flow rate of the pressurized fluid or terminate the injection of the pressurized fluid according to the percentage or the calculation result.

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