Patent Description:
Specifically, it is well known that the power required by a hydraulic system can be defined as the hydraulic fluid pressure times its volumetric flow rate. The volumetric flow rate, in turn, can be defined as the hydraulic fluid flow cross-sectional area times the flow velocity.

In an injection molding system, the flow rate inputs of flow cross-sectional area and flow velocity (in other words, size and speed) correspond to those properties of the actuator. Thus, an injection molding system's hydraulic power can be defined as the system pressure times the actuator cross-sectional area times the actuator speed. In order to reduce the consumption of energy, one or more of these three parameters-system pressure, actuator area, and actuator speed-must be reduced. Because an injection molding system has fixed actuator sizes, it is not feasible to reduce their size during operation of the injection molding system. And while the actuator speed can be reduced, this is not desirable because actuator speed and system output are directly correlated, so reducing speed would reduce output.

Thus, to reduce energy consumption while maintaining output, the most feasible option is to reduce system pressure. <FIG> is a graph that illustrates the relationship between system pressure, energy, and output in injection molding systems generally. As system pressure is reduced in an injection molding system, the specific energy consumed at a given quantity of output is also reduced.

A hydraulic system may be designed to operate over a number of process cycles, and various functions may take place during each cycle. In an injection molding system, these functions may relate to, at a high level, clamping of the mold, injection of plastic material, cooling of the injected plastic, and ejection of the molded part. More specifically, such functions may include, for example, and among others, mold closing, clamp-up, injection fill, injection hold, unclamp, mold opening, ejector-forward, ejector-back, transfer, packing, and carriage. These functions have different pressure requirements, so within an injection molding system cycle, the pressure necessary to perform these functions may have largely fluctuating values. For a given function, the required pressure may also vary at different components of the injection molding system-for example, the pressures at the pump(s), accumulator(s), clamp supply, and injection supply may have different values. In order for the injection molding system to operate, its system pressure must have a value at least as great as the greatest required value of component pressure in a cycle. However, to the extent the system pressure is greater than the greatest required value of component pressure, this surplus represents excess energy that was unnecessarily consumed. <FIG> are graphs that illustrate this surplus in system pressure for injection supply in an injection molding system. The system pressure is reduced in this example from <NUM> bar in <FIG>to <NUM> bar in <FIG>, reducing the surplus system pressure over the peak component pressure, and thereby reducing the energy consumed by the system.

Examples of known injection molding systems and components thereof are disclosed in <CIT> and <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>, including via additional references disclosed therein.

In one aspect of the present invention, there is provided an injection molding system configured to operate in a plurality of cycles. The system comprises a pump assembly, a proportional pump control valve operatively connected to the pump assembly, a sensor and a controller. The proportional pump control valve is configured to provide a variable pressure setpoint of the injection molding system equal to a magnitude of pressure of hydraulic fluid within the proportional pump control valve. The sensor is configured to detect the magnitude of pressure hydraulic fluid within the proportional pump control valve and to send a signal to the controller representative of the variable pressure setpoint. The controller is configured to control a flowrate of hydraulic fluid flowing out of the proportional pump control valve. The variable pressure setpoint is configured to change based on the flowrate of hydraulic fluid flowing out of the proportional pump control valve. The controller is configured to perform a comparison of the variable pressure setpoint with a target pressure value. Upon performing the comparison of the variable pressure setpoint with the target pressure value, the controller is configured to, when the target pressure value is less than the variable pressure setpoint by at least a predetermined lower bound, (i) decrease the variable pressure setpoint to a reduced variable pressure setpoint and (ii) not further decrease the variable pressure setpoint from the reduced variable pressure setpoint until the pump assembly operates for a plurality of stabilizing cycles at the reduced variable pressure setpoint.

Other aspects and features of the present invention are identified in the claims.

Other aspects and features of the non-limiting embodiments may now become apparent to those skilled in the art upon review of the following detailed description of the non-limiting embodiments with the accompanying drawings.

The non-limiting embodiments may be more fully appreciated by reference to the following detailed descriptions of the non-limiting embodiments, when taken in conjunction with the accompanying drawings, in which:.

The drawings are not necessarily to scale and may be illustrated by phantom lines, diagrammatic representations and fragmentary views. In certain instances, details not necessary for an understanding of the embodiments (and/or details that render other details difficult to perceive) may have been omitted.

The present invention is related to a hydraulic system. In specific embodiments of the 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 could be used in systems other than an injection molding system.

Referring now to <FIG>, an example of an injection molding system <NUM> is shown. The molding system <NUM> is configured to support and to use a hydraulic circuit of the present invention, including the examples of <FIG> and <FIG>. Other aspects and components of the injection molding system <NUM> may be known and may include those disclosed in <CIT> and <CIT>, including the references disclosed therein. For example, aspects of the injection molding system <NUM> depicted in <FIG> are described in <CIT>. According to the example of <FIG>, the injection molding system <NUM> includes (and is not limited to) an extruder assembly, a clamp assembly, a runner system, and/or a mold assembly <NUM>. By way of example, the extruder assembly <NUM> is configured to prepare, in use, a heated, flowable resin, and is also configured to inject or to move the resin from the extruder assembly <NUM> toward the runner system <NUM>. Other names for the extruder assembly <NUM> may include "injection unit," "melt-preparation assembly," etc. By way of example, the clamp assembly <NUM> includes (and is not limited to): a stationary platen <NUM>, a movable platen <NUM>, a rod assembly <NUM>, a clamping assembly <NUM>, and/or a lock assembly <NUM>. The stationary platen <NUM> does not move; that is, the stationary platen <NUM> may be fixedly positioned relative to the ground or floor. The movable platen <NUM> is configured to be movable relative to the stationary platen <NUM>. A platen-moving mechanism (not depicted but known) is connected to the movable platen <NUM>, and the platen-moving mechanism is configured to move, in use, the movable platen <NUM>. The rod assembly <NUM> extends between the movable platen <NUM> and the stationary platen <NUM>. The rod assembly <NUM> may have, by way of example, four rod structures positioned at the corners of the respective stationary platen <NUM> and the movable platen <NUM>. The rod assembly <NUM> is configured to link the movable platen <NUM> to the stationary platen <NUM>. A clamping assembly <NUM> is connected to the rod assembly <NUM>. The stationary platen <NUM> is configured to support (or configured to position) the position of the clamping assembly <NUM>. The lock assembly <NUM> is connected to the rod assembly <NUM>, or may alternatively be connected to the movable platen <NUM>. The lock assembly <NUM> is configured to selectively lock and unlock the rod assembly <NUM> relative to the movable platen <NUM>. By way of example, the runner system <NUM> is attached to, or is supported by, the stationary platen <NUM>. The runner system <NUM> is configured to receive the resin from the extruder assembly <NUM>. By way of example, the mold assembly <NUM> includes (and is not limited to): a mold-cavity assembly <NUM> and a mold-core assembly <NUM> that is movable relative to the mold-cavity assembly <NUM>. The mold-core assembly <NUM> is attached to or supported by the movable platen <NUM>. The mold-cavity assembly <NUM> is attached to or supported by the runner system <NUM>, so that the mold-core assembly <NUM> faces the mold-cavity assembly <NUM>. The runner system <NUM> is configured to distribute the resin from the extruder assembly <NUM> to the mold assembly <NUM>.

In operation, the movable platen <NUM> is moved toward the stationary platen <NUM> so that the mold-cavity assembly <NUM> is closed against the mold-core assembly <NUM>, so that the mold assembly <NUM> may define a mold cavity configured to receive the resin from the runner system <NUM>. The lock assembly <NUM> is engaged so as to lock the position of the movable platen <NUM> so that the movable platen <NUM> no longer moves relative to the stationary platen <NUM>. The clamping assembly <NUM> is then engaged to apply a clamping pressure, in use, to the rod assembly <NUM>, so that the clamping pressure then may be transferred to the mold assembly <NUM>. The extruder assembly <NUM> pushes or injects, in use, the resin to the runner system <NUM>, which then the runner system <NUM> distributes the resin to the mold cavity structure defined by the mold assembly <NUM>. Once the resin in the mold assembly <NUM> is solidified, the clamping assembly <NUM> is deactivated so as to remove the clamping force from the mold assembly <NUM>, and then the lock assembly <NUM> is deactivated to permit movement of the movable platen <NUM> away from the stationary platen <NUM>, and then a molded article may be removed from the mold assembly <NUM>.

It will be appreciated that the injection molding system <NUM> may include more than two platens. According to an example, the injection molding system <NUM> includes (and is not limited to) a third platen (not depicted), which is also called a "clamping platen" that is known in the art and thus is not described here in greater detail.

Referring now to <FIG>, a schematic for a hydraulic circuit is shown at <NUM>. The hydraulic circuit <NUM> is configured to actuate one or more functions of the injection molding system <NUM>, for example, mold closing, clamp-up, injection fill. According to the example of <FIG>, the hydraulic circuit <NUM> includes a pump assembly <NUM>, a motor assembly <NUM>, a pump actuator assembly <NUM>, a hydraulic fluid filter <NUM>, an accumulator check valve <NUM>, one or more accumulator assemblies <NUM>, a pump compensator valve assembly <NUM>, a proportional pump control valve <NUM>, a reservoir <NUM>, and a controller <NUM>.

The pump assembly <NUM> is configured to pump hydraulic fluid from the reservoir <NUM> to other components of the hydraulic circuit <NUM>. In the presently illustrated embodiment, the pump assembly <NUM> is a variable displacement piston pump, although it is not particularly limited and can include both fixed and variable displacement pumps, as is known to those skilled in the art. The pump assembly <NUM> is operatively connected to motor assembly <NUM>, to the reservoir <NUM>, and to one or more accumulator assemblies <NUM>. The pump assembly <NUM> is also operatively connected to, and configured to be controlled by a valve. For example, <NUM> Control Valve is configured to control the pump assembly <NUM> by changing its displacement. Alternatively if so equipped the pump can be controlled with a variable speed motor, the RPM can be controlled, or both RPM and displacement can be controlled.

The motor assembly <NUM> is configured to actuate movement of the pump assembly <NUM>. In the presently illustrated embodiment, the motor assembly <NUM> is a fixed-RPM motor, although it is not particularly limited and can include variable RPM motors or servo motors. The motor assembly <NUM> is operatively connected to, and configured to be controlled by, the drive. For example, the servo drive or variable frequency drive is configured to control the motor assembly <NUM> by changing its rpm, or torque limits.

The one or more accumulator assemblies <NUM> are configured to store hydraulic fluid under pressure generated by the pump assembly <NUM>. The one or more accumulator assemblies <NUM> are operatively connected to the pump assembly <NUM> via the accumulator check valve <NUM> and the hydraulic fluid filter <NUM>. The accumulator check valve <NUM> is configured to prevent the one or more accumulator assemblies <NUM> from discharging through the hydraulic fluid filter <NUM> and the pump assembly <NUM> while the motor assembly <NUM> is not in operation. The hydraulic fluid filter <NUM> is configured to filter the hydraulic fluid flowing to one or more accumulator assemblies <NUM>.

The pump compensator valve assembly <NUM> is configured to control the flow of hydraulic fluid to the actuator assembly <NUM> and to the proportional pump control valve <NUM> while the hydraulic fluid pressure has a value that is outside of preset setpoints. The pump compensator valve assembly <NUM> is operatively connected to the pump assembly <NUM>, to the actuator assembly <NUM>, and to the proportional pump control valve <NUM>. The pump compensator valve assembly <NUM> includes a maximum pump compensator valve <NUM> and a minimum pump compensator valve <NUM>. The maximum pump compensator valve <NUM> is configured to provide a preset maximum pressure setpoint of the injection molding system <NUM>, and the minimum pump compensator valve <NUM> is configured to provide a preset minimum pressure setpoint of the injection molding system <NUM>. In an example embodiment, the preset maximum pressure setpoint is <NUM> bar and the preset minimum pressure setpoint is <NUM> bar. In an example embodiment, each of the maximum pump compensator valve <NUM> and the minimum pump compensator valve <NUM> includes a set screw that is configured to be adjusted prior to operation of the injection molding system <NUM>; adjustment of the set screw changes the value of the spring force applied by the corresponding pump compensator valve and thus its preset pressure setpoint. The pump assembly <NUM> is configured to destroke when the hydraulic fluid pressure reaches the preset maximum pressure setpoint, such that this pressure value is maintained. In particular, when the system pressure (i) is below the minimum the valve <NUM> directs flow to the reservoir <NUM> through control valve <NUM>, causing the pump to go to maximum displacement, (ii) crosses the minimum threshold, (iii) crosses the maximum threshold, and (iv) is above the maximum the valve <NUM> blocks flow to the reservoir <NUM> and through control valve <NUM>, causing the pump to go to minimum displacement.

The actuator assembly <NUM> is configured to impart a force to the pumps internal swashplate. The force is used, for example, to change the displacement of the pump assembly <NUM>.

The proportional pump control valve <NUM> is configured to provide a variable pressure setpoint of the injection molding system <NUM>, within the end limits of valves <NUM> and <NUM>, and thereby control the system pressure of the injection molding system <NUM>. The proportional pump control valve <NUM> is operatively connected to the reservoir <NUM>. In the presently illustrated embodiment, the proportional pump control valve <NUM> is operatively connected to the reservoir <NUM> via a supply line <NUM>. The proportional pump control valve <NUM> is operatively connected to a sensor <NUM>. The sensor <NUM> is configured to detect pressure within the proportional pump control valve <NUM> and to send a signal representative of the pressure detected by the sensor <NUM> to the controller <NUM>. In the presently illustrated embodiment, the sensor <NUM> is a transducer. The proportional pump control valve <NUM> is operatively connected to, and configured to be controlled by, the controller <NUM>. For example, the controller <NUM> is configured to send a voltage signal to the proportional pump control valve <NUM>. The proportional pump control valve <NUM> is configured to, upon receipt of the voltage signal, permit flow of hydraulic fluid to the reservoir <NUM>, and thereby provide a variable pressure setpoint that is lower than the preset maximum pressure setpoint. In an example embodiment, the proportional pump control valve <NUM> is a variable displacement valve, whereby the voltage signal sent by the controller <NUM> governs the position of a spool within the proportional pump control valve <NUM>, thereby causing the orifice of the proportional pump control valve <NUM> to change in size depending on the voltage signal, such that hydraulic fluid flows at changing flowrates-or not at all-along the supply line <NUM> to the reservoir <NUM>. In this manner, changes in the size of the orifice of the proportional pump control valve <NUM> change pressure of the hydraulic fluid flowing through the proportional pump control valve <NUM>, thus changing the variable pressure setpoint and ultimately changing the system pressure. The reservoir <NUM> is configured to be a source of and receptacle for hydraulic fluid.

The hydraulic circuit <NUM> is thus configured to perform the following operation. When the motor assembly <NUM> operates to actuate movement of the pump assembly <NUM>, the pump assembly <NUM> pumps hydraulic fluid from the reservoir <NUM> to the pump compensator valve assembly <NUM> and in turn to the actuator assembly <NUM> and the proportional pump control valve <NUM>. The pump assembly <NUM> also pumps hydraulic fluid to the one or more accumulator assemblies <NUM>. With the presence of the voltage signal from the controller <NUM> to the proportional pump control valve <NUM>, the hydraulic fluid is restricted or not permitted to flow from the proportional pump control valve <NUM> to the reservoir <NUM>, and thus flows to the actuator assembly <NUM>. If there is no voltage signal the valve <NUM> will not restrict the oil flow and the "orifice" will be at maximum size. The pressure in the pump control circuit will decrease. If the minimum pressure setting of control valve <NUM> is reached, control valve <NUM> will close or restrict the oil flow into hose <NUM> diverting flow to actuator <NUM> in attempt to increase the displacement and increase the pump pressure above the minimum setpoint. As the pump assembly <NUM> continues to pump hydraulic fluid within the hydraulic circuit <NUM>, the pressure of the hydraulic fluid-corresponding to the system pressure of the injection molding system <NUM>-will continue to increase. In the event of a failure of the proportional pump control valve <NUM> or the controller <NUM>, the maximum pressure compensator valve <NUM> governs, and the system pressure will rise until it equals the preset maximum pressure setpoint. In normal operation, the proportional pump control valve <NUM> governs, and the system pressure will rise until it equals the variable pressure setpoint, as determined based on the voltage signal sent by the controller <NUM>. Depending on one or more system parameters, the voltage signal will change during operation, resulting in corresponding changes to the variable pressure setpoint and hence achieving adaptive system pressure.

Referring now to <FIG>, a schematic for a hydraulic circuit according to another embodiment is shown at <NUM>. The hydraulic circuit <NUM> is configured to actuate one or more functions of the injection molding system <NUM>. According to the example of <FIG>, the hydraulic circuit <NUM> includes a first pump assembly <NUM>, a first actuator assembly <NUM>, a first pump compensator valve assembly <NUM>, a second pump assembly <NUM>, a second actuator assembly <NUM>, a second pump compensator valve assembly <NUM>, a motor assembly <NUM>, a hydraulic fluid filter <NUM>, an accumulator check valve <NUM>, one or more accumulator assemblies <NUM>, a proportional pump control valve <NUM>, a reservoir <NUM>, and a controller <NUM>.

It will be appreciated that, in accordance with the teachings herein, the injection molding system <NUM> may also be adapted to utilize three pump assemblies working with the proportional pump control valve <NUM>. In accordance with the teachings herein, the injection molding system <NUM> 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 <NUM> or quantity of proportional pump control valves, to ensure enough hydraulic fluid can flow to the reservoir <NUM>.

Referring now to <FIG>, a flowchart of an example process of the controller <NUM> on the molding system <NUM> is shown at <NUM>.

At step <NUM>, the controller <NUM> checks whether the injection molding system <NUM> is in production cycles. Production cycles are in contrast to other cycle modes such as dry cycle when the injection unit is not engaged and no parts are made even though mold are being closed and opened in each cycle. Dry cycle is sometimes called empty cycle. Production cycles are sometimes called normal cycles. For example, the injection molding system <NUM> may be deemed not in production cycles if it is in any of the following modes: idle, calibration, mold set, manual, dry cycle, factory test, semi, ejector boosters active, and mold vent cleaning cycles. If yes, the process <NUM> moves to step <NUM>. If no, the process <NUM> moves to step <NUM>.

At step <NUM>, the controller <NUM> checks whether a predetermined number of baseline cycles have been completed. The first cycle after auto start is counted as <NUM>, any subsequent cycle will increase the count by one. "Auto Start" means the start of production cycle mode. If the predefined number is <NUM>, the predefined number of cycles are completed when the count reaches <NUM>. As further discussed below, the baseline cycles may be performed both in connection with startup of the process <NUM> and in further iterations of the process <NUM> when restarting pressure adaptation. If yes, the process <NUM> moves to step <NUM>. If no, the process <NUM> moves to step <NUM>.

At step <NUM>, the pump assembly <NUM> operates for the predetermined number of baseline cycles at a predetermined standard pressure value. The so predetermined standard pressure is set by the controller <NUM> and needs to be in the range between the minimum limit set by valve <NUM> and maximum limit set by valve <NUM>. In separate example embodiments, the predetermined number of baseline cycles is <NUM> cycles and <NUM> cycles, although a different predetermined number of baseline cycles may be selected in accordance with the present invention. The process <NUM> then moves to step <NUM>.

At step <NUM>, the controller <NUM> determines and logs the baseline performance of the injection molding system <NUM>. The baseline performance refers to one or more functions of the injection molding system <NUM>, and can include the time durations of the following functions, among others: mold closing, mold opening, clamp-up, unclamp, and/or ejector-forward. The baseline performance is determined based on measurements from one or more sensors associated with the functions, such as transducers. Baseline performance in the current implementation is regarding motion time specifically, although it can expand to any other criteria. The process <NUM> then moves to step <NUM>.

At step <NUM>, the controller <NUM> determines and sets a target pressure value. The target pressure value is less than the predetermined standard pressure value but not small enough to result in a deviation from the baseline performance determined at step <NUM>. In an example embodiment, the controller <NUM> sets the target pressure value to the highest value among the lower limits of pressure value imposed by one or more functions of the injection molding system <NUM>. These functions may include, for example, the functions measured during step <NUM>. In an example embodiment, the lower limits of pressure value are determined using measurement and mathematical modeling. That is, for any given function, the lower limit of pressure value for that function can be determined based on measurement of its mechanical characteristics, mathematical modeling of its mechanical characteristics, or both, where the lower limit is the greater of the pressure value determined from the measurements or model. The mechanical characteristics of a function that can be measured include force, pressure, acceleration, and velocity, and physical characteristics associated with the function, including mass and area, can be used with the function's mechanical characteristics to determine its lower limit of pressure. Mathematical models can be used, for example, for functions that are sufficiently fast or dynamic so as to limit the accuracy of measurements, for the purpose of estimate the minimum pressure required to deliver performance of those functions. The process <NUM> then moves to step <NUM>.

At step <NUM>, the controller <NUM> checks whether the pressure of the one or more accumulator assemblies <NUM> is lower than a predetermined accumulator pressure limit. In separate example embodiments, the predetermined accumulator pressure limit is <NUM> bar and <NUM> bar, although a different predetermined accumulator pressure limit may be selected in accordance with the present invention. If yes, the process <NUM> moves to step <NUM>. If no, the process <NUM> moves to step <NUM>.

At step <NUM>, the controller <NUM> increases the variable pressure setpoint by an amount equal to the difference between the pressure of the one or more accumulator assemblies <NUM> and the predetermined accumulator pressure limit. The process <NUM> then moves to step <NUM>.

At step <NUM>, the controller <NUM> checks whether the cycle/function time duration is longer than the corresponding baseline time duration determined at step <NUM>. If yes, the process <NUM> moves to step <NUM>. If no, the process <NUM> moves to step <NUM>.

At step <NUM>, the controller <NUM> increases the target pressure value to the value of the setpoint before the most recent drop in step <NUM>. The process then moves to step <NUM>.

At step <NUM>, the controller <NUM> checks whether the target pressure value is greater than the variable pressure setpoint of the injection molding system <NUM>. If yes, the process <NUM> moves to step <NUM>. If no, the process moves to step <NUM>.

At step <NUM>, the controller <NUM> increases the variable pressure setpoint to the target pressure value. In an example embodiment, the controller <NUM> does so by causing the proportional pump control valve <NUM> to decrease the flowrate of hydraulic fluid to the reservoir <NUM>. The process then moves to step <NUM>.

At step <NUM>, the controller <NUM> checks whether a predetermined number of stabilizing cycles have been completed since the most recent decrease in the variable pressure setpoint. For the purposes of step <NUM>, in the cycle immediately after the predetermined number of baseline cycles have been completed, the predetermined number of stabilizing cycles are deemed to have been completed since the most recent decrease in target pressure. Since the number of base line cycles is chosen to be larger than the number of stabilizing cycles, there is no need to repeat the number of stabilizing cycles immediately after the baseline cycles. In an example embodiment, the predetermined number of stabilizing cycles is <NUM> cycles, although a different predetermined number of stabilizing cycles may be selected in accordance with the present invention. If yes, the process <NUM> moves to step <NUM>. If no, the process <NUM> moves to step <NUM>.

At step <NUM>, the controller <NUM> decreases the variable pressure setpoint to a value approaching the target pressure value. In an example embodiment, the controller <NUM> does so by causing the proportional pump control valve <NUM> to increase the flowrate of hydraulic fluid to the reservoir <NUM>. In an example embodiment, the decrease in the variable pressure setpoint is equal, or approximately equal, to a predetermined percentage of the difference between the variable pressure setpoint and the target pressure value. In an example embodiment, the decrease in the variable pressure setpoint is also limited such that it is within, or approximately within, a predetermined bound of pressure values. For example, the predetermined percentage may be <NUM>%, and the predetermined bound may be <NUM> bar to <NUM> bar, inclusive, although a different predetermined percentage and/or predetermined bound of pressure values may be selected in accordance with the present invention. In this example, if the decrease in the variable pressure setpoint would be greater than the upper bound, it is limited to the upper bound, while if the decrease in the variable pressure setpoint would be less than the lower bound, it does not take place, and instead there is no change in the variable pressure setpoint. The process <NUM> then moves to step <NUM>.

At step <NUM>, the controller <NUM> sets an updated value of the variable pressure setpoint, when applicable. The process <NUM> then moves to step <NUM>.

At step <NUM>, the controller <NUM> checks whether relevant setpoints have been changed. As non-limiting examples, the relevant setpoints may be changeable by an operator of the injection molding system <NUM> and include but not limited the following setpoints: mold open position, mold closing speed, clamp tonnage, injection fill rate, etc. If yes, the process <NUM> then moves to step <NUM>. If no, the process <NUM> then moves to step <NUM>.

At step <NUM>, the controller <NUM> causes the injection molding system <NUM> to restart pressure adaptation and reestablish baseline performance. For example, it does so by treating the predetermined number of baseline cycles not to have been completed. The process <NUM> then moves to step <NUM>.

At step <NUM>, the controller <NUM> checks whether the hold/cooling time has decreased. If yes, the process <NUM> moves to step <NUM>. If no, the process <NUM> moves to step <NUM>. Hold time and cooling time are user setpoints on HMI and the controller keeps tracking if they are changed by the user. The controller records the event, amount, and the direction (increase or decrease) of the change.

At step <NUM>, the controller <NUM> increases the variable pressure setpoint to compensate for the decrease in accumulator pressure charging time duration. Accumulator pressure charging typically occurs during the injection-hold and injection-cooling functions, in which oil consumption is at a minimum. If the accumulator charging time duration decreases, then the pressure of the one or more accumulator assemblies <NUM> will decrease and may be unable to support remaining functions of the current cycle, such as unclamp and mold-opening. In an example embodiment, the compensation for the decrease in accumulator charging time duration is performed using the accumulator pressure charging rate that is calibrated in a state of minimum oil consumption. For example, the state of minimum oil consumption can include the clamp-up and injection hold functions and exclude the transfer and packing functions. In an example embodiment, the controller <NUM> increases the variable pressure setpoint by causing the proportional pump control valve <NUM> to decrease the flowrate of hydraulic fluid to the reservoir <NUM>. The process <NUM> then moves to step <NUM>.

At step <NUM>, the pump assembly <NUM> operates at the reduced pressure. The process <NUM> then moves to step <NUM>. At step <NUM>, the pump assembly <NUM> operates for all cycles except for those cycles or modes that are subject to conditions in <NUM>.

At step <NUM>, the process <NUM> continues and moves to step <NUM>.

As exemplified by example process <NUM>, the injection molding system <NUM> can operate to adapt the system pressure of the injection molding system <NUM> based on one or more inputs of the system.

Referring now to <FIG>, a graph of variable pressure setpoint over cycles in an example operation of the injection molding system <NUM> is shown at <NUM>. In the graph <NUM>, the y-axis is the variable pressure setpoint, measured in bar, and the x-axis is the number of completed cycles. Prior to cycle <NUM>, the variable pressure setpoint is approximately <NUM> bar. In an example embodiment performing the process <NUM>, this represents the predetermined standard pressure value. At the predetermined standard pressure value, the variable pressure setpoint is lower than the preset maximum pressure setpoint, which is <NUM> bar in the example.

From cycle <NUM> to cycle <NUM>, the pump assembly <NUM> operates for <NUM> cycles at a variable pressure setpoint of approximately <NUM> bar. In an example embodiment performing the process <NUM>, this represents the process <NUM> iterating through step <NUM> for the predetermined number of baseline cycles-here, <NUM> cycles.

During cycle <NUM>, the variable pressure setpoint is decreased to approximately <NUM> bar. In an example embodiment performing the process <NUM>, this represents the process <NUM> now proceeding through step <NUM> and step <NUM> within a single iteration. More specifically, at step <NUM>, the target pressure value is set to a value that is less than the predetermined standard pressure value. At step <NUM>, the controller <NUM> determines that the predetermined number of baseline cycles was completed with cycle <NUM>, so at step <NUM>, it decreases the variable pressure setpoint to a value-here, approximately <NUM> bar-approaching the target pressure value.

From cycle <NUM> to cycle <NUM>, the pump assembly <NUM> operates for <NUM> cycles at the variable pressure setpoint of approximately <NUM> bar. In an example embodiment performing the process <NUM>, this represents the process <NUM> proceeding from step <NUM> as discussed above through step <NUM>, then iterating for <NUM> more cycles proceeding directly through step <NUM> and step <NUM> and not step <NUM>, for a total that is the predetermined number of stabilizing cycles-here, <NUM> cycles.

During cycle <NUM>, the variable pressure setpoint is decreased to approximately <NUM> bar. In an example embodiment performing the process <NUM>, this represents the process <NUM> again proceeding through step <NUM> and step <NUM> within a single iteration. At step <NUM>, the controller <NUM> determines that the predetermined number of stabilizing cycles was completed with cycle <NUM>, so at step <NUM>, it decreases the variable pressure setpoint to a value-here, approximately <NUM> bar-approaching the target pressure value.

From cycle <NUM> to cycle <NUM>, the pump assembly <NUM> operates for <NUM> cycles at the variable pressure setpoint of approximately <NUM> bar. In an example embodiment performing the process <NUM>, this represents the process <NUM> again proceeding from step <NUM> as discussed above through step <NUM>, then iterating for <NUM> more cycles proceeding directly through step <NUM> and step <NUM> and not step <NUM>, for a total that is the predetermined number of stabilizing cycles.

During cycle <NUM>, the variable pressure setpoint is increased to approximately <NUM> bar, representing an increase equal to the decrease that took place during cycle <NUM>. In an example embodiment performing the process <NUM>, this represents the process <NUM> proceeding through either or both of step <NUM> and step <NUM>, and then through step <NUM>, within a single iteration. As a more specific example, this represents the process <NUM> proceeding through step <NUM>, at which the controller <NUM> determines that the most recently measured ejector-forward time duration is greater than the ejector-forward time duration that was determined during baseline performance. Accordingly, the process <NUM> proceeds directly through step <NUM> and increases the target pressure value by an amount equal to the previous decrease. Within the same iteration, the process <NUM> then proceeds through step <NUM>, where the controller <NUM> determines that the target pressure value is greater than the variable pressure setpoint, and then directly through step <NUM>, where the controller <NUM> increases the variable pressure setpoint to the target pressure value-here, approximately <NUM> bar. The target pressure is <NUM> bar in cycle <NUM>, remains at <NUM> bar in cycle <NUM>. At the end of cycle <NUM> and before starting cycle <NUM>, the control detected an increase of cycle time or function step time, it rolled the pressure back to <NUM> bar by undoing the previous pressure drop. At the same time, the control also changes the target pressure to be the same as the pressure setpoint, <NUM> bar in this case. From cycle <NUM> to <NUM>, since the cycle time is not affected due to higher pressure (<NUM> bar) than the pressure used in cycle <NUM> (<NUM> bar), the algorithm doesn't go through step <NUM>. The target pressure that is determined in step <NUM> by the model remains at <NUM> bar (not revised higher). Due to another criteria that kicks in when step <NUM> is triggered by the condition in <NUM>, the pressure drop described in step <NUM> is limited by a small value of <NUM> bar. Note that in cycle <NUM>, the cycle time is impacted again and the algorithm trigged step <NUM> the second time. It is in this instance that the target pressure settles at <NUM> bar. From cycle <NUM> to cycle <NUM>, the injection molding system <NUM> operates with similar behavior to that of cycle <NUM> to cycle <NUM> discussed above. In an example embodiment performing the process <NUM>, this represents the process <NUM> proceeding through iterations of stabilizing cycles, one-cycle decreases in variable pressure setpoint, and a one-cycle increase in variable pressure setpoint offsetting the previous decrease.

During cycle <NUM>, the variable pressure setpoint has essentially converged to the target pressure value. In an example embodiment performing the process <NUM>, this represents the process <NUM> proceeding through step <NUM>, where the variable pressure setpoint is either equal or close enough to the target pressure value or that it does not decrease at step <NUM>. In an example embodiment where the minimum decrease in target pressure value must be approximately <NUM> bar, the variable pressure setpoint can be within <NUM> bar above the target pressure value.

After cycle <NUM>, the pump assembly <NUM> operates for an indefinite number of cycles at the stabilized variable pressure setpoint-here, approximately <NUM> bar. In an example embodiment performing the process <NUM>, this will continue until an event causes a change in target pressure.

The graph <NUM> thus demonstrates how, in one aspect of the present invention, decreases in the variable pressure setpoint gradually stabilize to an optimal value.

Claim 1:
An injection molding system (<NUM>) configured to operate in a plurality of cycles, the system comprising:
a pump assembly (<NUM>, <NUM>);
a proportional pump control valve (<NUM>) operatively connected to the pump assembly (<NUM>, <NUM>);
a sensor (<NUM>); and
a controller (<NUM>),
wherein the proportional pump control valve (<NUM>) is configured to provide a variable pressure setpoint of the injection molding system (<NUM>) equal to a magnitude of pressure of hydraulic fluid within the proportional pump control valve (<NUM>);
wherein the sensor (<NUM>) is configured to detect the magnitude of pressure hydraulic fluid within the proportional pump control valve (<NUM>) and to send a signal to the controller (<NUM>) representative of the variable pressure setpoint,
wherein the controller (<NUM>) is configured to control a flowrate of hydraulic fluid flowing out of the proportional pump control valve (<NUM>),
wherein the variable pressure setpoint is configured to change based on the flowrate of hydraulic fluid flowing out of the proportional pump control valve (<NUM>),
characterised in that
the controller (<NUM>) is configured to perform a comparison of the variable pressure setpoint with a target pressure value,
wherein, upon performing the comparison of the variable pressure setpoint with the target pressure value, the controller (<NUM>) is configured to, when the target pressure value is less than the variable pressure setpoint by at least a predetermined lower bound, (i) decrease the variable pressure setpoint to a reduced variable pressure setpoint and (ii) not further decrease the variable pressure setpoint from the reduced variable pressure setpoint until the pump assembly (<NUM>, <NUM>) operates for a plurality of stabilizing cycles at the reduced variable pressure setpoint.