Stable Adaptive Hydraulic System Pressure in Injection Molding Systems

Abstract

In one aspect, an injection molding system configured to operate in multiple cycles is provided. The system includes, among other things, a controller configured to perform a comparison of a variable pressure set point with a target pressure value. The controller is configured to, when the target pressure value is less than the variable pressure set point by at least a predetermined lower limit, (i) reduce the variable pressure set point to a reduced variable pressure set point, and (ii) not further reduce the variable pressure set point from the reduced variable pressure set point until the pump assembly operates at the reduced variable pressure set point for multiple stable cycles.

Description

Technical Field

[0001] The present invention relates to the field of injection molding, and more particularly, to stable adaptive hydraulic system pressure in an injection molding system. Background Art

[0002] It is desirable to minimize energy consumption in hydraulic systems, including, for example, injection molding systems. The energy consumed in such hydraulic systems is a function of various characteristics of the system, such that changing one or more of these characteristics will change the energy consumed.

[0003] Specifically, it is well known that the power required by a hydraulic system can be defined as the hydraulic fluid pressure multiplied by its volume flow rate. The volume flow rate can in turn be defined as the hydraulic fluid flow cross-sectional area multiplied by the flow rate.

[0004] In an injection molding system, the flow inputs of flow cross-sectional area and flow rate (in other words, size and speed) correspond to those characteristics of the actuator. Therefore, the hydraulic power of an injection molding system can be defined as the system pressure times the actuator cross-sectional area times the actuator speed. In order to reduce energy consumption, one or more of these three parameters - system pressure, actuator area, and actuator speed - must be reduced.

[0005] Because the injection molding system has a fixed actuator size, it is not feasible to reduce the size of the injection molding system during operation. Although the actuator speed can be reduced, this is undesirable because the actuator speed and system output are directly related, so reducing the speed will reduce the output.

[0006] Therefore, in order to reduce energy consumption while maintaining output, the most viable option is to reduce system pressure. Figure 1 is a graph generally illustrating the relationship between system pressure, energy and output in an injection molding system. When the system pressure is reduced in an injection molding system, the specific energy consumed at a given amount of output is also reduced.

[0007] The hydraulic system can be designed to operate on multiple processing cycles, and various functions can occur during each cycle. In the injection molding system, these functions can be related to the clamping of the mold, the injection of plastic material, the cooling of the injection plastic and the ejection of the molded parts at a high level. More specifically, these functions may include, for example, mold closing, clamping, injection filling, injection holding, loosening, mold opening, forward demoulding, backward demoulding, transfer, packaging and transportation. These functions have different pressure requirements, so the pressure required to perform these functions can have a large fluctuation value within the injection molding system cycle. For a given function, the required pressure can also change at different parts of the injection molding system, for example, the pressure at the pump (one or more), accumulator (one or more), fixture supplier and injection supplier can have different values. In order for the injection molding system to operate, its system pressure must have a value at least as large as the maximum required value of the component pressure in the cycle. However, to the extent that the system pressure is greater than the maximum required value of the component pressure, the margin represents unnecessary consumption of excess energy. Figures 2A and 2B are graphs illustrating this margin of the system pressure of the injection supply in the injection molding system. In this example, the system pressure is reduced from 220 bar in FIG. 2A to 190 bar in FIG. 2B , thereby reducing the excess system pressure above the peak component pressure and thereby reducing the energy consumed by the system.

[0008] The known US2015 / 0037448A1 is disclosed in WO 2010 / 144993 and US2015 / 0037448A1, including additional references disclosed therein. Summary of the invention

[0009] In one aspect of the present invention, an injection molding system configured to operate in multiple cycles is provided. The system includes a pump assembly, a proportional pump control valve operably connected to the pump assembly, a sensor, and a controller. The proportional pump control valve is configured to provide a variable pressure set point of the injection molding system that is equal to the pressure of the hydraulic fluid in the proportional pump control valve. The sensor is configured to detect the magnitude of the pressure hydraulic fluid in the proportional pump control valve and send a signal representing the variable pressure set point to the controller. The controller is configured to control the flow rate of the hydraulic fluid flowing out of the proportional pump control valve. The variable pressure set point is configured to change based on the flow rate of the hydraulic fluid flowing out of the proportional pump control valve. The controller is configured to perform a comparison of the variable pressure set point with a target pressure value. When performing a comparison of the variable pressure set point with the target pressure value, the controller is configured to, when the target pressure value is less than the variable pressure set point by at least a predetermined lower limit, (i) reduce the variable pressure set point to a reduced variable pressure set point, and (ii) not further reduce the variable pressure set point from the reduced variable pressure set point until the pump assembly operates at the reduced variable pressure set point for a plurality of stable cycles.

[0010] Further aspects and features of the invention are defined in the claims.

[0011] Other aspects and features of the non-limiting embodiments will become apparent to those skilled in the art by reading the following detailed description of the non-limiting embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A more complete understanding of the non-limiting embodiments may be obtained by reference to the following detailed description of the non-limiting embodiments when taken in conjunction with the accompanying drawings, in which:

[0013] FIG1 depicts a graph showing specific energy as a function of system pressure and output;

[0014] FIG2A depicts a graph showing injection pressure and system pressure versus time;

[0015] FIG2B depicts a graph showing injection pressure and lower system pressure as a function of time;

[0016] Figure 3 An example of an injection molding system is depicted;

[0017] Figure 4 A first example of a hydraulic circuit is depicted;

[0018] Figure 5 A second example of a hydraulic circuit is depicted;

[0019] Figure 6 a flow chart depicting an exemplary process of the controller on the hydraulic system; and

[0020] Figure 7 A graph showing variable pressure set point values ​​over the number of completed cycles is depicted.

[0021] The drawings are not necessarily drawn to scale and may be illustrated by phantom lines, diagrammatic representations, and fragmentary views. In certain instances, details that are not necessary for understanding the embodiments (and / or that render other details obscure) may have been omitted. DETAILED DESCRIPTION

[0022] The present invention relates to a hydraulic system. In the specific embodiments of the present invention described below, the hydraulic system is used as part of an injection molding system. However, those skilled in the art will recognize that the hydraulic system can be used in systems other than injection molding systems.

[0023] Reference now Figure 3 , shows an example of an injection molding system 900. The molding system 900 is configured to support and use the hydraulic circuit of the present invention, including Figure 4and Figure 5 Other aspects and components of the injection molding system 900 may be known and may include those disclosed in WO 2010 / 144993 and US 2015 / 0037448 A1, including the references disclosed therein. For example, US 2015 / 0037448 A1 describes Figure 3 Aspects of the injection molding system 900 described in. Figure 3 , the injection molding system 900 includes (and is not limited to) an extruder assembly, a fixture assembly, a runner system and / or a mold assembly 918. For example, the extruder assembly 902 is configured to prepare a heated flowable resin in use, and is also configured to inject or move the resin from the extruder assembly 902 toward the runner system 916. Other names for the extruder assembly 902 may include "injection unit", "melt preparation assembly", etc. As an example, the fixture assembly 904 includes (and is not limited to): a fixed platen 906, a movable platen 908, a rod assembly 910, a clamping assembly 912 and / or a locking assembly 914. The fixed platen 906 does not move; that is, the fixed platen 906 can be fixedly positioned relative to the ground or floor. The movable platen 908 is configured to be movable relative to the fixed platen 906. A platen moving mechanism (not depicted but known) is connected to the movable platen 908, and the platen moving mechanism is configured to move the movable platen 908 in use. The rod assembly 910 extends between the movable platen 908 and the fixed platen 906. For example, the rod assembly 910 may have four rod structures positioned at the corners of the corresponding fixed platen 906 and the movable platen 908. The rod assembly 910 is configured to link the movable platen 908 to the fixed platen 906. The clamping assembly 912 is connected to the rod assembly 910. The fixed platen 906 is configured to support (or is configured to locate) the position of the clamping assembly 912. The locking assembly 914 is connected to the rod assembly 910, or alternatively to the movable platen 908. The locking assembly 914 is configured to selectively lock and unlock the rod assembly 910 relative to the movable platen 908. For example, the runner system 916 is attached to the fixed platen 906 or supported by the fixed platen 906. The runner system 916 is configured to receive resin from the extruder assembly 902. For example, mold assembly 918 includes (and is not limited to): mold cavity assembly 920 and mold cavity assembly 922 movable relative to mold cavity assembly 920. Mold cavity assembly 922 is attached to or supported by movable platen 908. Mold cavity assembly 920 is attached to or supported by runner system 916 so that mold cavity assembly 922 faces mold cavity assembly 920. Runner system 916 is configured to distribute resin from extruder assembly 902 to mold assembly 918.

[0024] In operation, the movable platen 908 is moved toward the fixed platen 906 so that the mold cavity assembly 920 is closed against the mold cavity assembly 922 so that the mold assembly 918 can define a mold cavity configured to receive resin from the runner system 916. The locking assembly 914 is engaged to lock the position of the movable platen 908 so that the movable platen 908 can no longer move relative to the fixed platen 906. The clamping assembly 912 is then engaged to apply a clamping pressure to the rod assembly 910 in use so that the clamping pressure can then be transferred to the mold assembly 918. The extruder assembly 902, in use, pushes or injects resin into the runner system 916, which then distributes the resin to the mold cavity structure defined by the mold assembly 918. Once the resin in mold assembly 918 cures, clamp assembly 912 is deactivated to remove the clamping force from mold assembly 918 , and then locking assembly 914 is deactivated to allow movable platen 908 to move away from fixed platen 906 , and the molded article can then be removed from mold assembly 918 .

[0025] It should be understood that the injection molding system 900 may include more than two platens. According to one example, the injection molding system 900 includes (and is not limited to) a third platen (not depicted), also referred to as a "clamping platen", which is known in the art and is therefore not described in more detail herein.

[0026] Reference now Figure 4 , a schematic diagram of a hydraulic circuit is shown at 100. The hydraulic circuit 100 is configured to actuate one or more functions of the injection molding system 900, such as mold closing, clamping, injection filling. Figure 4 In the example of , the hydraulic circuit 100 includes a pump assembly 110, a motor assembly 112, a pump actuator assembly 116, a hydraulic fluid filter 115, an accumulator check valve 117, one or more accumulator assemblies 118, a pump compensator valve assembly 120, a proportional pump control valve 150, a reservoir 160 and a controller 170.

[0027] The pump assembly 110 is configured to pump hydraulic fluid from the reservoir 160 to other components of the hydraulic circuit 100. In the embodiment currently shown, the pump assembly 110 is a variable displacement piston pump, but as known to those skilled in the art, the pump assembly 110 is not particularly limited and may include a fixed displacement pump and a variable displacement pump. The pump assembly 110 is operably connected to the motor assembly 112, the reservoir 160, and one or more accumulator assemblies 118. The pump assembly 110 is also operably connected to the valve and configured to be controlled by the valve. For example, the control valve 150 is configured to control the pump assembly 110 by changing the displacement of the pump assembly 110. Alternatively, if so equipped, the pump can be controlled with a variable speed motor, the RPM can be controlled, or the RPM and displacement can be controlled.

[0028] The motor assembly 112 is configured to drive the movement of the pump assembly 110. In the embodiment currently shown, the motor assembly 112 is a fixed RPM motor, although it is not particularly limited and may include a variable RPM motor or a servomotor. The motor assembly 112 is operably connected to a drive and configured to be controlled by the drive. For example, a servo drive or a variable frequency drive is configured to control the motor assembly 120 by changing its RPM or torque limit.

[0029] The one or more accumulator assemblies 118 are configured to store hydraulic fluid under pressure generated by the pump assembly 110. The one or more accumulator assemblies 118 are operably connected to the pump assembly 110 via an accumulator check valve 117 and a hydraulic fluid filter 115. The accumulator check valve 117 is configured to prevent the one or more accumulator assemblies 118 from draining through the hydraulic fluid filter 115 and the pump assembly 110 when the motor assembly 112 is not operating. The hydraulic fluid filter 115 is configured to filter the hydraulic fluid flowing to the one or more accumulator assemblies 118.

[0030] The pump compensator valve assembly 120 is configured to control the flow of hydraulic fluid to the actuator assembly 116 and to the proportional pump control valve 150 while the hydraulic fluid pressure has a value outside of a preset set point. The pump compensator valve assembly 120 is operably connected to the pump assembly 110, the actuator assembly 116, and the proportional pump control valve 150. The pump compensator valve assembly 120 includes a maximum pump compensator valve 130 and a minimum pump compensator valve 140. The maximum pump compensator valve 130 is configured to provide a preset maximum pressure set point for the injection molding system 900, and the minimum pump compensator valve 140 is configured to provide a preset minimum pressure set point for the injection molding system 900. In an exemplary embodiment, the preset maximum pressure set point is 230 bar and the preset minimum pressure set point is 20 bar. In an exemplary embodiment, each of the maximum pump compensator valve 130 and the minimum pump compensator valve 140 includes a set screw that is configured to be adjusted prior to operation of the injection molding system 900; adjustment of the set screw changes the value of the spring force applied by the corresponding pump compensator valve and thus changes its preset pressure set point. The pump assembly 110 is configured to reduce the stroke when the hydraulic fluid pressure reaches a preset maximum pressure set point, thereby maintaining the pressure value. In particular, when the system pressure (i) is below a minimum value, the valve 140 directs the fluid to flow through the control valve 150 to the reservoir 160, thereby causing the pump to reach maximum displacement, (ii) crosses a minimum threshold, (iii) crosses a maximum threshold, and (iv) is above a maximum value, the valve 130 blocks the fluid from flowing to the reservoir 160 and through the control valve 150, thereby causing the pump to reach minimum displacement.

[0031] The actuator assembly 116 is configured to apply a force to a swash plate inside the pump. The force is used, for example, to change the displacement of the pump assembly 110.

[0032] The proportional pump control valve 150 is configured to provide a variable pressure set point of the injection molding system 900 within the end limits of the valves 130 and 140, and thereby control the system pressure of the injection molding system 900. The proportional pump control valve 150 is operably connected to the reservoir 160. In the embodiment currently shown, the proportional pump control valve 150 is operably connected to the reservoir 160 via a supply line 154. The proportional pump control valve 150 is operably connected to a sensor 180. The sensor 180 is configured to detect the pressure within the proportional pump control valve 150 and send a signal representing the pressure detected by the sensor 180 to the controller 170. In the embodiment currently shown, the sensor 180 is a transducer. The proportional pump control valve 150 is operably connected to the controller 170 and is configured to be controlled by the controller 170. For example, the controller 170 is configured to send a voltage signal to the proportional pump control valve 150. The proportional pump control valve 150 is configured to allow hydraulic fluid to flow to the reservoir 160 upon receiving a voltage signal, thereby providing a variable pressure set point that is lower than a preset maximum pressure set point. In an exemplary embodiment, the proportional pump control valve 150 is a variable displacement valve, whereby a voltage signal sent by the controller 170 governs the position of a spool within the proportional pump control valve 150, thereby causing the orifice of the proportional pump control valve 150 to change size according to the voltage signal, so that hydraulic fluid flows to the reservoir 160 along the supply line 154 at a varying flow rate or not at all. In this way, a change in the orifice size of the proportional pump control valve 150 changes the pressure of the hydraulic fluid flowing through the proportional pump control valve 150, thereby changing the variable pressure set point and ultimately changing the system pressure. The reservoir 160 is configured as a hydraulic fluid source and a hydraulic fluid container.

[0033] The hydraulic circuit 100 is therefore configured to perform the following operations. When the motor assembly 112 operates to actuate the movement of the pump assembly 110, the pump assembly 110 pumps hydraulic fluid from the reservoir 160 to the pump compensator valve assembly 120, and in turn to the actuator assembly 116 and the proportional pump control valve 150. The pump assembly 110 also pumps hydraulic fluid to one or more accumulator assemblies 118. In the presence of a voltage signal from the controller 170 to the proportional pump control valve 150, the hydraulic fluid is restricted or not allowed to flow from the proportional pump control valve 150 to the reservoir 160, and thus to the actuator assembly 116. If there is no voltage signal, the valve 150 will not restrict the oil flow, and the "orifice" will be at the maximum size. The pressure in the pump control circuit will decrease. If the minimum pressure setting of the control valve 140 is reached, the control valve 140 will close or restrict the oil flow into the hose 142, diverting the flow to the actuator 116 in an attempt to increase the displacement and increase the pump pressure above the minimum set point. As the pump assembly 110 continues to pump hydraulic fluid within the hydraulic circuit 100, the pressure of the hydraulic fluid corresponding to the system pressure of the injection molding system 900 will continue to increase. In the event of a failure of the proportional pump control valve 150 or the controller 170, the maximum pressure compensator valve 130 takes control, and the system pressure will increase until it equals the preset maximum pressure set point. In normal operation, the proportional pump control valve 150 takes control, and the system pressure will increase until it equals the variable pressure set point, as determined based on the voltage signal sent by the controller 170. Depending on one or more system parameters, the voltage signal will change during operation, resulting in a corresponding change in the variable pressure set point, and thus achieving an adaptive system pressure.

[0034] Reference now Figure 5 A schematic diagram of a hydraulic circuit according to another embodiment is shown at 200. The hydraulic circuit 200 is configured to actuate one or more functions of the injection molding system 900. Figure 5 In the example of, the hydraulic circuit 200 includes a first pump assembly 110, a first actuator assembly 116, a first pump compensator valve assembly 120, a second pump assembly 210, a second actuator assembly 216, a second pump compensator valve assembly 220, a motor assembly 112, a hydraulic fluid filter 115, an accumulator check valve 117, one or more accumulator assemblies 118, a proportional pump control valve 150, a reservoir 160 and a controller 170.

[0035] It should be appreciated that, in accordance with the teachings herein, the injection molding system 900 may also be adapted to utilize three pump assemblies working in conjunction with the proportional pump control valve 150. In accordance with the teachings herein, the injection molding system 900 may also be adapted to utilize an even greater number of pump assemblies by increasing the size / output / capacity of the proportional pump control valve 150 or the amount of proportional pump control valves to ensure that sufficient hydraulic fluid can flow to the reservoir 160.

[0036] View now Figure 6 , a flow chart of an example process of the controller 170 on the molding system 900 is shown at 1000 .

[0037] At step 1010, the controller 170 checks whether the injection molding system 900 is in a production cycle. The production cycle is different from other cycle modes (such as a dry cycle when the injection unit is not engaged and no parts are made even if the mold is closed and opened in each cycle. The dry cycle is sometimes called an empty cycle. The production cycle is sometimes called a normal cycle. For example, if the injection molding system 900 is in any of the following modes, it can be considered that it is not in a production cycle: idle, calibration, mold setup, manual, dry cycle, factory test, SEMI, ejector booster active, and mold exhaust cleaning cycle. If yes, the process 1000 moves to step 1020. If no, the process 1000 moves to step 1025.

[0038] At step 1020, the controller 170 checks whether a predetermined number of baseline cycles have been completed. The first cycle after an autostart is counted as 1, and any subsequent cycles increase the count by 1. "Autostart" refers to the start of a production cycle mode. If the predefined number is 10, then the predefined number of cycles is completed when the count reaches 10. As discussed further below, a baseline cycle can be performed in conjunction with the start of process 1000 and further iterations of process 1000 when pressure adaptation is restarted. If yes, then process 1000 moves to step 1030. If no, then process 1000 moves to step 1025.

[0039] At step 1025, the pump assembly 110 is run for a predetermined number of baseline cycles at a predetermined standard pressure value. Such predetermined standard pressure is set by the controller 170 and needs to be within a range between a minimum limit set by the valve 140 and a maximum limit set by the valve 130. In a separate exemplary embodiment, the predetermined number of baseline cycles is 10 cycles and 20 cycles, although a different predetermined number of baseline cycles may be selected in accordance with the present invention. The process 1000 may then move to step 1026.

[0040] At step 1026, the controller 170 determines and records a baseline performance of the injection molding system 900. Baseline performance refers to one or more functions of the injection molding system 900 and may include the duration of the following functions, among other functions: mold close, mold open, clamp, unclamp, and / or eject-forward. The baseline performance is determined based on measurements from one or more sensors (e.g., transducers) associated with the functions. The baseline performance in the current implementation is specifically about motion time, although it can be extended to any other criteria. The process 1000 can then move to step 1120.

[0041] At step 1030, the controller 170 determines and sets a target pressure value. The target pressure value is less than a predetermined standard pressure value, but not small enough to cause a deviation from the baseline performance determined at step 1026. In an exemplary embodiment, the controller 170 sets the target pressure value to the highest value in the lower limit of the pressure values ​​applied by one or more functions of the injection molding system 900. These functions may include, for example, functions measured during step 1026. In an exemplary embodiment, the lower limit of the pressure value is determined using measurements and mathematical models. That is, for any given function, the lower limit of the pressure value of the function can be determined based on the measurement of its mechanical properties, the mathematical model of its mechanical properties, or both, where the lower limit is the larger value of the pressure value determined by the measurement or model. The mechanical properties of the function that can be measured include force, pressure, acceleration, and velocity, and the physical properties associated with the function (including mass and area) can be used together with the mechanical properties of the function to determine its lower pressure limit. Mathematical models can be used, for example, for sufficiently fast or dynamic functions to limit the accuracy of the measurement for estimating the minimum pressure required to deliver the performance of those functions. Process 1000 can then move to step 1040.

[0042] At step 1040, the controller 170 checks whether the pressure of the one or more accumulator assemblies 118 is below a predetermined accumulator pressure limit. In a separate exemplary embodiment, the predetermined accumulator pressure limits are 170 bar and 174 bar, although different predetermined accumulator pressure limits may be selected in accordance with the present invention. If yes, the process 1000 moves to step 1045. If no, the process 1000 moves to step 1050.

[0043] In step 1045 , the controller 170 increases the variable pressure set point by an amount equal to the difference between the pressure of the one or more accumulator assemblies 118 and the predetermined accumulator pressure limit. Process 1000 may then move to step 1050 .

[0044] At step 1050, the controller 170 checks whether the cycle / function duration is longer than the corresponding baseline duration determined at step 1026. If yes, the process 1000 moves to step 1055. If no, the process 1000 moves to step 1060.

[0045] At step 1055 , the controller 170 increases the target pressure value to the set point value before the most recent decrease at step 1075 . Then, the process moves to step 1060 .

[0046] At step 1060, the controller 170 checks whether the target pressure value is greater than the variable pressure set point of the injection molding system 900. If yes, the process 1000 moves to step 1065. If no, the process moves to step 1070.

[0047] At step 1065 , controller 170 increases the variable pressure set point to the target pressure value. In the exemplary embodiment, controller 170 does this by causing proportional pump control valve 150 to reduce the flow rate of hydraulic fluid to reservoir 160 . The process then moves to step 1080 .

[0048] At step 1070, the controller 170 checks whether a predetermined number of stabilization cycles have been completed since the most recent decrease in the variable pressure set point. For purposes of step 1070, the predetermined number of stabilization cycles are considered to have been completed since the most recent decrease in the target pressure in a cycle after the predetermined number of baseline cycles have been completed. Since the number of baseline cycles is selected to be greater than the number of stabilization cycles, the number of stabilization cycles need not be repeated immediately after the baseline cycle. In the exemplary embodiment, the predetermined number of stabilization cycles is 5 cycles, although a different predetermined number of stabilization cycles may be selected in accordance with the present invention. If yes, then the process 1000 moves to step 1075. If no, then the process 1000 moves to step 1080.

[0049] At step 1075, the controller 170 reduces the variable pressure set point to a value close to the target pressure value. In an exemplary embodiment, the controller 170 achieves this by causing the proportional pump control valve 150 to increase the flow rate of the hydraulic fluid to the reservoir 160. In an exemplary embodiment, the reduction of the variable pressure set point is equal to or approximately equal to a predetermined percentage of the difference between the variable pressure set point and the target pressure value. In an exemplary embodiment, the reduction of the variable pressure set point is also limited so that it is within or approximately within a predetermined limit of the pressure value. For example, the predetermined percentage may be 61.8%, and the predetermined limit may be 1 bar to 10 bar, including 1 bar and 10 bar, although different predetermined percentages and / or predetermined limits of pressure values ​​may be selected according to the present invention. In this example, if the reduction of the variable pressure set point will be greater than the upper limit, it is limited to the upper limit, and if the reduction of the variable pressure set point will be less than the lower limit, it does not occur, and instead there is no change in the variable pressure set point. The process 1000 may then move to step 1080.

[0050] At step 1080 , controller 170 sets an updated value for the variable pressure set point, when applicable. Process 1000 may then move to step 1090 .

[0051] At step 1090, the controller 170 checks whether the relevant set point has been changed. As a non-limiting example, the relevant set point can be changed by the operator of the injection molding system 900, and includes but is not limited to the following set points: If yes, the process 1000 moves to step 1095. If no, the process 1000 then moves to step 1100.

[0052] At step 1095 , the controller 170 causes the injection molding system 900 to restart pressure adaptation and reestablish baseline performance. For example, this is done by processing a predetermined number of baseline cycles that have not been completed. The process 1000 can then move to step 1020 .

[0053] At step 1100, the controller 170 checks if the hold / cool down time has been reduced. If so, the process 1000 moves to step 1105. If not, the process 1000 moves to step 1110. The hold time and cool down time are user set points on the HMI, and if they are changed by the user, the controller keeps track. The controller records the event, amount, and direction (increase or decrease) of the change.

[0054] In step 1105, the controller 170 increases the variable pressure set point to compensate for the reduction in accumulator boost duration. Accumulator boost typically occurs during injection holding and injection cooling functions, where fuel consumption is minimal. If the accumulator charge duration is reduced, the pressure of one or more accumulator assemblies 118 will decrease and may not be able to support the remaining functions of the current cycle, such as loosening and mold opening. In an exemplary embodiment, compensation for the reduction in accumulator boost duration is performed using an accumulator boost rate calibrated under a minimum fuel consumption state. For example, a state of minimum fuel consumption may include clamping and injection holding functions, but not conveying and packaging functions. In an exemplary embodiment, the controller 170 increases the variable pressure set point by causing the proportional pump control valve 150 to reduce the flow rate of hydraulic fluid to the reservoir 160. The process 1000 can then move to step 1110.

[0055] At step 1110, pump assembly 110 is operated at reduced pressure. Process 1000 can then move to step 1120. At step 1110, pump assembly 110 runs all cycles except those cycles or modes that are subject to the conditions in 1025.

[0056] At step 1120 , process 1000 continues and moves to step 1010 .

[0057] As illustrated in the exemplary process 1000 , the injection molding system 900 is operable to adapt a system pressure of the injection molding system 900 based on one or more inputs to the system.

[0058] Reference now Figure 7 , shows a graph of variable pressure set points within a cycle in an example operation of an injection molding system 900. In the graph, the y-axis is the variable pressure set point measured in bars and the x-axis is the number of cycles completed.

[0059] Prior to cycle 1, the variable pressure set point is approximately 220.0 bar. In the exemplary embodiment of the process 1000, this represents a predetermined standard pressure value. At the predetermined standard pressure value, the variable pressure set point is below the preset maximum pressure set point, which in this example is 230 bar.

[0060] From cycle 1 to cycle 10, pump assembly 110 operates at a variable pressure set point of approximately 220.0 bar for 10 cycles. In the example embodiment of executing process 1000, this means that process 1000 repeats through step 1025 for a predetermined number of baseline cycles - here, 10 cycles.

[0061] During cycle 11, the variable pressure set point is reduced to approximately 210.0 bar. In the exemplary embodiment of the execution of process 1000, this means that process 1000 now proceeds to step 1030 and step 1075 within a single iteration. More specifically, at step 1030, the target pressure value is set to a value less than the predetermined standard pressure value. At step 1070, controller 170 determines that a predetermined number of baseline cycles have been completed with cycle 10, so at step 1075, it reduces the variable pressure set point to a value close to the target pressure value - here, approximately 210.0 bar.

[0062] From cycle 11 to cycle 15, the pump assembly 110 is operated at a variable pressure set point of approximately 210.0 bar for 5 cycles. In the exemplary embodiment of the implementation of process 1000, this means that process 1000 proceeds from step 1075 as described above to step 1110, and then proceeds directly to step 1070 and step 1080 instead of step 1075 for another 4 cycles, for a total of a predetermined number of stable cycles, here 5 cycles.

[0063] During cycle 16, the variable pressure set point is reduced to approximately 200.0 bar. In the exemplary embodiment of the implementation of process 1000, this means that process 1000 again performs steps 1030 and 1075 within a single iteration. In step 1070, controller 170 determines that a predetermined number of stable cycles are completed with cycle 15, so in step 1075, it reduces the variable pressure set point to a value close to the target pressure value - here, approximately 200.0 bar.

[0064] From cycle 16 to cycle 20, the pump assembly 110 is operated at a variable pressure set point of approximately 200.0 bar for 5 cycles. In the exemplary embodiment of the implementation of process 1000, this means that process 1000 again proceeds from step 1075 as described above to step 1110, and then proceeds directly to step 1070 and step 1080 instead of step 1075 for another 4 cycles, for a total of a predetermined number of stable cycles.

[0065] During cycle 21, the variable pressure set point is reduced to approximately 193.8 bar. In the exemplary embodiment of the implementation of process 1000, this means that process 1000 again performs steps 1030 and 1075 within a single iteration. In step 1070, controller 170 determines that a predetermined number of stable cycles are completed with cycle 20, so in step 1075, it reduces the variable pressure set point to a value close to the target pressure value - here, approximately 193.8 bar.

[0066] During cycle 22, the variable pressure set point increases to approximately 200.0 bar, representing an increase equal to the decrease that occurred during cycle 21. In an exemplary embodiment of performing process 1000, this means that process 1000 performs either or both of steps 1045 and 1055 within a single iteration, and then performs step 1065. As a more specific example, this means that process 1000 proceeds to step 1050, where the controller 170 determines that the most recently measured ejector forward duration is greater than the ejector forward duration determined during baseline performance. Therefore, process 1000 proceeds directly to step 1055 and increases the target pressure value by an amount equal to the previous decrease. In the same iteration, process 1000 then proceeds to step 1060, where the controller 170 determines that the target pressure value is greater than the variable pressure set point, and then proceeds directly to step 1065, where the controller 170 increases the variable pressure set point to the target pressure value - here, approximately 200.0 bar. The target pressure is 190 bar in cycle 20 and remains at 190 bar in cycle 21. At the end of cycle 21 and before starting cycle 22, the controller detects an increase in cycle time or function step time, and it rolls the pressure back to 200 bar by canceling the previous pressure drop. At the same time, the controller also changes the target pressure to be the same as the pressure set point, in this case 200 bar. From cycles 22 to 26, the algorithm does not pass step 1055 because the cycle time is not affected by a pressure (200 bar) higher than the pressure used in cycle 21 (193.8 bar). The target pressure determined by the model in step 1030 remains at 190 bar (not corrected to be higher). Due to another criterion that occurs when step 1055 is triggered by the condition in 1050, the pressure drop described in step 1075 is limited by a small value of 1 bar. Note that in cycle 37, the cycle time is again affected and the algorithm triggers step 1055 a second time. In this case, the target pressure stabilizes at 198 bar.

[0067] From cycle 22 to cycle 42, the injection molding system 900 operates with behavior similar to that discussed above for cycles 10 to 22. In the exemplary embodiment of the implementation of process 1000, this means that process 1000 performs iterations of stabilization cycles, a one-cycle decrease in the variable pressure set point, and a one-cycle increase in the variable pressure set point that offsets the previous decrease.

[0068] The variable pressure set point has substantially converged to the target pressure value during cycle 42. In an exemplary embodiment of performing process 1000, this means that process 1000 proceeds through step 1075, where the variable pressure set point is equal to or sufficiently close to the target pressure value, or it does not decrease at step 1075. In an exemplary embodiment, where the minimum decrease in the target pressure value must be approximately 1 bar, the variable pressure set point may be within 1 bar above the target pressure value.

[0069] After cycle 42, pump assembly 110 operates for an indefinite number of cycles at a stable variable pressure set point (here, approximately 198.0 bar). In the exemplary embodiment of process 1000, this will continue until an event causes a change in the target pressure.

[0070] Thus, in one aspect of the invention, the graph illustrates how the variable pressure set point is gradually and steadily reduced to an optimal value.

[0071] It should be understood that the present invention is not limited to the exemplary embodiments disclosed above. The present invention is intended to cover various modifications and equivalent arrangements, such as those included within the scope of the claims. It is understood that the above-mentioned embodiments, systems, components and other items can be connected to each other as needed to perform the desired functions and tasks, which are within the scope of such combinations and permutations made by ordinary technicians in the field without having to describe each of them in explicit terms.

Claims

1. An injection molding system configured to operate in multiple cycles, the system comprising: Pump components; a proportional pump control valve operably connected to the pump assembly; sensor; as well as Controller, wherein the proportional pump control valve is configured to provide a variable pressure set point for the injection molding system, the variable pressure set point being equal to a magnitude of a pressure of a hydraulic fluid within the proportional pump control valve; wherein the sensor is configured to detect an amount of pressurized hydraulic fluid within the proportional pump control valve and to send a signal to the controller indicative of the variable pressure set point, wherein the controller is configured to control the flow rate of the hydraulic fluid out of the proportional pump control valve, wherein the variable pressure set point is configured to vary based on a flow rate of hydraulic fluid out of the proportional pump control valve, wherein the controller is configured to perform a comparison of the variable pressure set point with a target pressure value, The controller determines and records a baseline performance of the injection molding system, the baseline performance referring to one or more functions of the injection molding system and the baseline performance is determined based on measurements from one or more sensors associated with the functions; The controller determines and sets the target pressure value, the target pressure value being less than a predetermined standard pressure value but not small enough to cause a deviation from the baseline performance; Wherein, when performing the comparison between the variable pressure set point and the target pressure value, the controller is configured to, when the target pressure value is less than the variable pressure set point by at least a predetermined lower limit, (i) reduce the variable pressure set point to a reduced variable pressure set point, and (ii) not further reduce the variable pressure set point from the reduced variable pressure set point until the pump assembly operates at the reduced variable pressure set point for a plurality of stable cycles.

2. The injection molding system according to claim 1, wherein: When performing the comparison of the variable pressure set point and the target pressure value, the controller is configured to increase the variable pressure set point to the target pressure value when the target pressure value is greater than the variable pressure set point.

3. The injection molding system according to claim 1 or 2, in, The pump assembly is configured to operate at the standard pressure value for a plurality of baseline cycles, wherein the controller is configured to receive and record measurements of one or more functions of the injection molding system during the baseline period, Wherein, the target pressure value is less than the standard pressure value, and Wherein the target pressure value is high enough not to cause a deviation in the performance of the one or more functions performed during the baseline period.

4. The injection molding system according to claim 1, wherein: When performing the comparison of the variable pressure set point with the target pressure value, the controller is configured to reduce the variable pressure set point to a reduced variable pressure set point when the target pressure value is less than the variable pressure set point by at least the predetermined lower limit, and the amount of the reduced variable pressure set point is proportional to the difference between the target pressure value and the variable pressure set point.

5. The injection molding system according to claim 1, wherein: There is a predetermined number of stabilization periods.

6. The injection molding system according to claim 3, wherein: There is a predetermined number of baseline periods.

7. The injection molding system according to claim 4, wherein: The amount by which the variable pressure set point is reduced is a predetermined percentage of a difference between the target pressure value and the variable pressure set point.

8. The injection molding system of claim 3, comprising one or more accumulator assemblies, in, The controller is configured to perform a comparison of a measurement of pressure within the one or more accumulator assemblies with a predetermined accumulator pressure limit, Wherein, when comparing the measured value of the pressure within the one or more accumulator assemblies with the predetermined accumulator pressure limit, the controller is configured to increase the target pressure value by an amount equal to the difference between the measured value of the pressure within the one or more accumulator assemblies and the predetermined accumulator pressure limit when the measured value of the pressure within the one or more accumulator assemblies is lower than the predetermined accumulator pressure limit.

9. The injection molding system according to claim 3, wherein: The controller sets the target pressure value to a highest value among lower limits of pressure values ​​applied by a plurality of functions of the injection molding system.

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