The present disclosure relates to controlling a heater for heating a molding system, and more particularly to methods and controllers for maintaining constant an amount of power delivered to a heater for heating a molding system.

BACKGROUND

Injection molding machines generally include a hopper for receiving resin, a barrel connected to the hopper and a screw that moves within the barrel to impart a force onto the resin to melt and move the resin along the barrel. The melted resin (an example of molding material) is injected from the barrel into a melt passage apparatus that defines one or more melt passage. The melt passage apparatus can also be identified as a molding material distributor. The melted resin passes through the melt passage(s) to one or more nozzle. The melted resin is then expelled into a mold cavity through a gate defined in the nozzle. The mold cavity can be formed by clamping two mold plates together.

An injection molding machine is an example of a molding system. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic representation of an embodiment of a molding system.

FIG. 2 depicts a schematic representation of an embodiment of a molding system controller.

FIG. 3 depicts a schematic representation of an embodiment of a molding system controller.

The drawings are not necessarily to scale and may be illustrated by phantom lines, diagrammatic representations and fragmentary views. In certain instances, details that are not necessary for an understanding of the embodiments or that render other details difficult to perceive may have been omitted. Like reference numerals are used in the drawings to identify like elements and features.

DETAILED DESCRIPTION

Reference will now be made in detail to various non-limiting embodiment(s) of a method and controller for controlling a heater for heating molding system. It should be understood that other non- limiting embodiment(s), modifications and equivalents will be evident to one of ordinary skill in the art in view of the non-limiting embodiment(s) disclosed herein and that these variants should be considered to be within scope of the appended claims. Furthermore, it will be recognized by one of ordinary skill in the art that certain structural and operational details of the non-limiting embodiment(s) discussed hereafter may be modified or omitted (i.e. non-essential) altogether. In other instances, well known methods, procedures, and components have not been described in detail. Generally disclosed is a controller that continuously monitors the incoming voltage as well as the current supplied to one or more heater to be able to provide constant power to the heater independent of heater resistance variation and incoming voltage variation.

By maintaining constant the amount of power being delivered to the heater 950, a drop balance of the molding material distributor 916 may be improved. Exemplary Molding System

FIG. 1 depicts an example of a molding system 900 and a molding system controller 100. The molding system 900 can be any suitable molding system such as, for example, an injection molding system or a compression molding system. In accordance with an embodiment, the molding system 900 includes an injection unit 902, a clamp assembly 904, a molding material distributor 916, and a mold as sembly 918.

The injection unit 902 can be any suitable injection unit such as, for example, a reciprocating screw type injection unit or a two stage type injection unit. The injection unit 902 is configured to inject molding material in the molding material distributor 916. The injection unit 902 can be connected to a hopper (not depicted) which receives solidified resin or solid particles of molding material. In a reciprocating screw type injection unit, the hopper is connected to a barrel portion of the injection unit 902 into which the solid particles of molding material flow. The reciprocating screw moves within the barrel to impart a force onto the solid particles of molding material to melt and move the molding material along the barrel towards an outlet. There can also be a heating unit or one or more heaters attached to the injection unit 902 in order to melt or assist with melting the molding material. A force is then imparted to the melted molding material to push it out of the injection unit 902 (e.g. through an outlet of the injection unit 902). This force can be provided by a movement of the screw along a longitudinal axis of the barrel or by another mechanism not shown.

The clamp assembly 904 includes a stationary platen 906, a movable platen 908, tie bars 910, a clamp 912, and a lock 914. In the depicted embodiment, there are four tie bars 910 that extend in parallel through areas near respective corners of the stationary platen 906 and movable platen 908. In other embodiments, there may be more or fewer tie bars 910. The tie bars 910 are generally used to align or maintain a position of the stationary platen 906 and movable platen 908. The tie bars 910 maintain the positions of the movable platen 908 and stationary platen 906 such that they are in parallel to each other and facing each other on respective surfaces. The movable platen 908 can be moved along a length of the tie bars 901 either towards or away from the stationary platen 906.

The lock 914 can be configured to lock the movable platen 908 in position (e.g. along the tie bars 910) relative to the stationary platen 906. For example, there may be a lock 914 associated with or coupled to or attached to the movable platen 908 for each tie bar 910 so that each lock 914 restricts movement of the movable platen 908 at the respective tie bar 910. In other examples, there may be only one lock 914 acting on a particular location of the movable platen 908 (e.g. where one of the tie bars 910 interacts with the movable platen 908) such that the one lock restricts movement of the entire movable platen 908. In other examples, there may be a different number of locks 914 or tie bars 910.

The clamp 912 is connected to the stationary platen 906. Alternatively, the clamp 912 is connected to a tie bar 910 near where the tie bar 910 interacts with the stationary platen 906. There can be one clamp 912 or there can be more than one clamp 912. For example, there can be clamps 912 attached to the stationary platen 906 at each location where the tie bars 910 interact with the stationary platen 906. The clamp 912 (or the multiple clamps 912 as the case may be) is configured to be able to apply a clamping force or pressure across the movable platen 908 and stationary platen 906. For example, when activated, the clamp 912 forces or presses the movable platen 908 and stationary platen 906 together. When deactivated, the clamp 912 releases the force or pressure across the movable platen 908 and stationary platen 906.

The mold assembly 918 includes a movable mold portion 922 and a stationary mold portion 920. The movable mold portion 922 and the stationary mold portion 920 can cooperate to define a mold cavity (not separately numbered). For example, the movable mold portion 922 can be connected to the movable platen 908 and the stationary mold portion 920 can be connected to the stationary platen 906. The movable mold portion 922 and stationary mold portion can be positioned or arranged such that they face each other inside of the area defined within the stationary platen 906 and movable platen 908. Following the same example, when the movable platen 908 is moved towards the stationary platen 906 the movable mold portion 922 is correspondingly moved towards the stationary mold portion 920. Thus, when the movable platen 908 is moved as far as it can go towards the stationary platen 906 then the movable mold portion 922 is moved as far as it can go towards the stationary mold portion 920. In such a state the mold cavity is defined between the movable mold portion 922 and stationary mold portion 920.

The molding material distributor 916 is configured and designed to receive the molding material injected by the injection unit 902 and to redirect or direct the received molding material to the mold cavity. The molding material distributor 916 defines a flow channel (not separately numbered) in fluid communication with the injection unit 902 and the mold cavity. The molding material injected by the injection unit 902 is received into the flow channel (e.g. through an inlet, which is not specifically identified in the Figures) which in turn distributes the molding material into the mold cavity. The molding material distributor 916 can also include a sprue (not depicted) configured to receive the molding material from the injection unit 902 before the molding material enters the flow channel. For example the sprue can be connected or disposed between an inlet of the flow channel and an outlet of the injection unit 902. The molding material distributor 916 can also include a nozzle (not depicted) configured to transfer the molding material from the flow channel to the mold cavity. For example, the nozzle can be connected or disposed near an outlet of the flow channel so as to receive the molding material from the flow channel and direct it to the mold cavity. As such, the nozzle can define a nozzle flow channel that is fluidly connected to the flow channel of the molding material distributor 916. The molding system 900 further includes a heater 950 for heating the molding system 900. In accordance with FIG. 1, the heater 950 is connected to the molding material distributor 916 and can be configured to heat the molding material distributor 916. There may be more or fewer heaters attached to certain components of the molding system 900, such as the molding material distributor 916 or the nozzle.

In reference to the exemplary embodiment shown in FIG. 1, a molding system controller 100 is connected to the heater 950. The molding system controller 100 can control the operation of the heater 950 through the connection.

The molding system controller 100 is also connected to a power supply 800. The power supply 800 can also be connected to the heater 950 for supplying power to the heater 950. In one or more embodiments, the molding system controller 100 can include a battery for providing power.

The molding system 900 further includes a human machine interface ("HMI") 170 connected to the molding system controller 100. The HMI 170 can include an input device such as a touchscreen display, a mouse or a keyboard, for example, and one or more output devices, such as a display or speaker. The HMI 170 includes a memory and a processor (or is otherwise associated with a memory and processor). The memory stores instructions for execution by the processor. The memory can also store data that can be accessed or manipulated through the HMI 170. For example, data and instructions can be received through the input device of the HMI 170 which can then be stored or altered, as the case may be, in memory.

In operation, the movable platen 908 moves toward the stationary platen 906 so that the mold assembly 918 defines the mold cavity. The lock 914 is engaged to lock the position of the movable platen 908 so that the movable platen 908 no longer moves relative to the stationary platen 906. The clamp 912 is then engaged to apply a camping pressure across the movable platen 908 and the stationary platen 906. The injection unit 902 injects, in use, the molding material to the molding material distributor 916. The molding material distributor 916 distributes the molding material to the mold cavity or allows the molding material to pass therethrough to arrive at the mold cavity. Once the molding material in the mold cavity has solidified, the clamp 912 deactivates to remove the clamping force from the mold assembly 918. The lock 914 then deactivates to permit movement of the movable platen 908 away from the stationary platen 906.

Molding System Controller

FIG. 2 depicts a schematic representation of an embodiment of the molding system controller 100. The molding system controller 100 includes a power controller 102. The power controller 102 is configured to controllably couple to the heater 950 and maintain constant an amount of power (wattage) being delivered to the heater 950. "Controllably couple" can mean that the power controller 102 is associated with the heater 950 in such a way that it can control the operation of the heater 950. For example, the power controller can be connected to the heater 950 by a wire through which the power is delivered to the heater 950.

The power controller 102 includes the HMI 170, a power calculation module 108, a duty cycle module 128, a power supply controller 122, a power source 800 connected to the power supply controller 122, a power meter 124, a power alarm 160, a temperature monitor 130, a temperature feedback selector 140, and a temperature alarm 150. Each of these components will be described in turn.

The power controller 102 includes a memory and a processor. For example, the memory can be a memory accessible by the power controller 102 to store, retrieve, delete or modify data and instructions. The processor can execute instructions stored on the memory in order to carry out calculations or affect physical consequences (e.g. through the transmission of electrical signals). There can be multiple processors one or more of which are dedicated to specific tasks. Similarly, there can be multiple memories accessible by one more of the processors.

The power calculation module 108 is configured to determine an amount of power that the heater 950 is to receive in order to maintain constant the amount of power consumed by the heater 950. The power calculation module 108 can be any suitable device, such as an electrical circuit or a software coded algorithm. For example, the power calculation module 108 can include instructions stored on the memory associated with the power controller 102 which can be executed by the processor. The instructions can include the determination of the amount of power that the heater 950 is to receive in order to maintain constant the amount of power consumed by the heater 950. Determining the amount of power that the heater 950 is to receive in order to maintain constant the amount of power consumed by the heater 950 can include determining an amount of power that the heater 950 is to receive in order to maintain the amount of power consumed by the heater 950 within a predetermined tolerance bandwidth. The power calculation module 108 is configured to receive a desired temperature signal and a temperature feedback signal. For example, a temperature sensor or thermometer can be positioned near the heater 950 or near another component in order to measure the temperature at such locations. The temperature sensor can then communicate the sensed temperature to the power calculation module 108 or to the power controller 102. The sensed temperature can be communicated through wires or through a wireless communication system. The sensed temperature is an example of a temperature feedback signal. By way of further example, the temperature feedback signal can include any suitable feedback information or feedback data such as a measured temperature, a calculated offset from a desired temperature set-point (error), or a statistical analysis of a measured temperature.

In one or more embodiments the power calculation module 108 receives the temperature feedback signal from a temperature feedback selector 140 with which it can communicate. The temperature feedback selector 140 can include the temperature sensors or thermocouples, for example.

The desired temperature signal includes information related to a desired temperature set-point as determined by an operator. For example, the power calculation module 108 receives the desired temperature signal from the HMI 170. The HMI 170 receives input data specifying the desired temperature set-point (e.g. from an operator). For example, the input data can specify the numerical desired temperature set-point. The input data can also identify the specific thermometer or thermometers to which the desired temperature set-point applies.

The power calculation module 108 generates a computed power signal based on the desired temperature signal and the temperature feedback signal. In an embodiment, the computed power signal can be representative of an amount of power that the heater 950 is to receive in order to maintain constant the amount of power consumed by the heater 950.

The power calculation module 108 includes a first combining device 112 and a power-calculator 104. The first combining device 112 can include one or more switches or can be a microprocessor, for example. The first combining device 112 is configured to receive the desired temperature signal and the temperature feedback signal and generate a temperature set-point signal. The first combining device 112 generates the temperature set-point signal by combining the desired temperature signal and the temperature feedback signal. For example, the desired temperature signal is received from the HMI 170. The power-calculator 104 can include or be associated with a microprocessor or memory. The power- calculator 104 is configured to receive the temperature set-point signal from the first combining device 112, and generate the computed power signal based on the temperature set-point signal. For example, the received temperature set-point signal can be stored as data in the memory associated with the power-calculator 104. The computed power signal includes information related to an amount of power that the heater 950 is to receive. For example, the computed power signal includes information related to at least one of: (i) an amount of current that the heater 950 is to receive, and (ii) a voltage level that is to be applied across the heater 950. The power-calculator 104 generates the computed power signal from the temperature set-point signal using any suitable algorithm such as, for example, a proportional (P) algorithm, a proportional integral (PI) algorithm, a proportional integral derivative (PID) algorithm, etc. By way of further clarification, according to an exemplary embodiment the power-calculator 104 generates the computed power signal using an aforementioned algorithm by executing instructions stored on the associated memory with data stored on the associated memory. The power controller 102 further includes a switch 110 such as a circuit switch or electronic switch. The switch can be designed and constructed to (i) receive the computed power signal from the power calculator 104 and a desired power signal (e.g. from the HMI 170), and (ii) output a switch output signal. The switch output signal selectively includes one of the computed power signal and the desired power signal. The switch 110 receives the computed power signal from the power-calculator 104. The desired power signal includes information related to a desired power set-point as determined by an operator for example. The switch 110 receives the desired power signal from the HMI 170. By way of example, the desired set-point can be received as input to the HMI 170 (e.g. from an operator providing input) and the desired power signal can be data representative of the desired set-point that is transmitted from the HMI 170 to the switch 110. Alternatively, the desired power set-point can be received from a remote computer device over a wireless network.

The duty cycle module 128 is generally configured to determine a ratio of on- time during when the heater 950 is to receive power within a given control cycle. The duty cycle module 128 can include any suitable device, including, but not limited to, an electrical circuit or a processor capable of executing software coded instructions stored on memory (e.g. an algorithm). The duty cycle module 128 is connected to the switch 110 and the power meter 124. The duty cycle module 128 can receive the switch output signal from the switch 110 and a power feedback signal from the power meter 124. The power feedback signal is data or includes information related to the amount of power being delivered to the heater 950. The duty cycle module 128 generates a duty cycle signal based on the switch output signal and the power feedback signal. The duty cycle module 128 includes a second combining device 113 and a duty cycle calculator 120. The second combining device 113 can include one or more switches or can be a microprocessor, for example. The second combining device 113 is configured to receive the signal output of switch 110 and the power feedback signal and generate a power adjustment signal. The second combining device 113 generates the power adjustment signal by combining the switch output signal and the power feedback signal.

The duty cycle calculator 120 can include or be associated with a processor and a memory. For example, the processor can execute instructions stored on memory. The memory can also store data which may be added, removed or altered by the processor. The duty cycle calculator 120 is configured to receive the power adjustment signal from the second combining device 113, and generate the duty cycle signal based on the power adjustment signal. For example, the power adjustment signal can be stored in the memory associated with the duty cycle calculator 120. The duty cycle calculator 120 generates the duty cycle signal from the power adjustment signal using any suitable algorithm such as, for example, a P algorithm, a PI algorithm, a PID algorithm. The algorithm can be carried out by the processor executing instructions stored on the memory associated with the duty cycle calculator 120.

The power supply controller 122 is connected to the power supply 800 and the heater 950. The power supply controller 122 can include any suitable switching device including, but not limited to, a solid- state relay (SSR), a semiconductor controlled rectifier (SCR), a triode for alternating current (TRIAC), a power transistor. The power supply controller 122 can also include or be associated with a memory and a microprocessor. The power supply controller 122 receives the duty cycle signal from the duty cycle calculator 120 and controls a duty cycle of the power supply 800 based on the duty cycle signal. For example, the duty cycle signal can consist of instructions to increase the duty cycle of the power supply 800. The power meter 124 is configured to measure the amount of power being delivered to the heater 950. The power meter 124 is also configured to generate the power feedback signal and to transmit the power feedback signal to the duty cycle module 128 (or to the second combining device 113). The measurement, generation and transmission can occur automatically at predetermined intervals. Alternatively (or additionally), the measurement, generation and transmission can occur on the receipt of instructions to initiate measurement from another component. The power meter 124 can include any suitable measuring device, including, but not limited to, a wattmeter, a voltage and current transducer, a current shunt.

The temperature monitor 130 receives an analogue temperature measurement (e.g. in the form of transmitted data or a signal) from a temperature sensor 952 and in response generates a corresponding digital temperature measurement. The temperature sensor 952 is configured to sense a temperature of the molding system 900 and generate an analogue temperature signal proportional to the temperature of the molding system 900. The temperature sensor 952 can include any suitable sensor such as a thermocouple, a resistance temperature detector (RTD) or a thermistor. In the embodiment depicted in FIG 1 the heater 950 and the temperature sensor 952 are both associated with the molding material distributor 916.

The temperature feedback selector 140 receives the digital temperature measurement from the temperature monitor 130 and generates the temperature feedback signal. The temperature feedback selector 140 can then transmit the temperature feedback signal to the power calculation module 108. The temperature feedback selector 140 can use any suitable algorithm to generate the temperature feedback signal such as an averaging algorithm, a min value algorithm, a max value algorithm, a statistical process control algorithm. In an alternative embodiment, the temperature monitor 130 directly transmits the digital temperature measurement to the power calculation module 108. In such an embodiment, the power calculation module 108 can be configured to receive the digital temperature measurement as if it was the temperature feedback signal.

The temperature alarm 150 receives the digital temperature measurement, and compares the digital temperature measurement to a predetermined temperature range. The temperature alarm 150 generates an alarm if the digital temperature measurement falls outside the selected temperature range. The digital temperature measurement may have been transmitted in the form of a signal, in which case the temperature alarm compares the temperature value associated with the signal to the predetermined temperature range. An operator can select or adjust the predetermined temperature range via the HMI 170 or remotely via a network. In an alternative embodiment, the temperature alarm 150 is not present in the power controller 102.

The power alarm 160 receives the power feedback signal, and compares a power value (e.g. the wattage) associated with the power feedback signal to a selected power range. The power alarm 160 generates an alarm if the power value associated with the power feedback signal falls outside the selected power range. An operator may set the selected power range via the HMI 170. In an alternative embodiment, the power alarm 160 is not present in the power controller 102.

According to another embodiment, the power controller 102 includes a combination alarm. The combination alarm receives the digital temperature measurement and the power feedback signal, and compares a ratio of the digital temperature measurement and a power value associated with the power feedback signal to a predetermined ratio range. The combination alarm generates an alarm if the ratio of the temperature measurement and the power value falls outside the predetermined ratio range. The predetermined ratio range can be set or adjusted via the HMI 170 or remotely via a network, for example,

The alarm of one or more of the power alarm 160, temperature alarm 150 and combination alarm can be audible (e.g. a bell), visual (e.g. a flashing light), tactile (e.g. vibration), or may result in an alarm message transmitted (e.g. over a network) to a remote location or the HMI 170, for example.

FIG. 3 depicts an example of another embodiment of a molding system controller 100 in which the power controller 102 is designed and arranged to controllably couple to a plurality of heaters 950 and maintain constant an amount of power being delivered to each heater of the plurality of heaters 950. For example, the power controller can be connected through a wired connection to the plurality of heaters 950 so as to individually control the amount of power being delivered to each heater.

Each heater of the plurality of heaters 950 is configured to heat the molding system 900. In an embodiment one or more heaters 950 are connected to a manifold so as to heat the manifold. In another embodiment, on or more heaters 950 are connected to a nozzle so as to provide heat to the nozzle.

The power controller 102, as depicted, includes (and is not limited to): a plurality of duty cycle calculators 120, a plurality of power supply controllers 122, a plurality of power meters 124, and a plurality of temperature sensors 952. The power controller 102 depicted in FIG 3 further includes a third combining device 213 that generates and applies a power adjustment signal to an input (not separately numbered) of the duty cycle calculator 220. The third combining device 213 generates the power adjustment signal by combining one of a computed power signal and a desired power signal, and a power feedback signal generated by one of the power meters 124. Each of the temperature monitor 130, the temperature feedback selector 140, the temperature alarm 150, and the power alarm 160 is configured to receive a plurality of signals with each signal representative of one of the heaters 950.

Operation of the Molding System Controller

Generally a constant power is provided to each heater by monitoring incoming voltage and current supplied to each heater.

In operation, referring to the embodiment depicted in FIG. 2, molding system controller 100 can operate according to at least one of (i) a hybrid-control strategy and (ii) an alarming strategy.

According to an embodiment of the hybrid-control strategy, the power consumed by the heater 950 is monitored and controlled, and the temperature sensor 952 is monitored and controlled. The power consumed by the heater 950 can be monitored and controlled so that it remains constant (e.g. at a preset power level) or within a predetermined threshold range. The predetermined threshold range and the preset power level can be set through the HMI 170 for example. The temperature sensor 952 senses or measures the temperature at or around the heater 950 at the time when the power level is set or first determined. The power level and the predetermined threshold range can be altered or added or deleted during operation (for example, through the HMI 170). The change or difference in the monitored temperature relative to the temperature as measured when the power level was set or altered (or when the predetermined threshold range was set or altered) can be determined (e.g. with a processor executing instructions on a memory) and (optionally) displayed on the HMI 170. In a further embodiment, using the power controller 102 described in reference to FIG. 3 there are a plurality of heaters 950, each with a corresponding temperature sensor 952. In such an embodiment, the change or difference in the monitored temperature relative to the temperature as measured when the power level was set or altered (or when the predetermined threshold range was set or altered) for each of the plurality of heaters 950 can be determined and (optionally) displayed on the HMI 170. In a further embodiment, after determining the change or difference in the monitored temperature relative to the temperature as measured when the power level was set or altered in respect of a specific heater 950, the heat provided to that heater 950 can be adjusted so that the heat from the heater 950 is such that the change or difference will become smaller.

The power levels or predetermined threshold range can be set for specific heaters 950 separately. For example, input received at the HMI 170 can alter the preset power level for a specifically identified heater 950.

According to an embodiment, the alarming strategy includes at least one of temperature-sensor control and constant-power control.

According to temperature-sensor control, an alarm can be configured to indicate when the power required to maintain the temperature around a temperature sensor 952 at a predetermined temperature level or range changes. The predetermined temperature levels or ranges can be set or altered or deleted through the HMI 170, for example.

According to constant-power control, an alarm can be configured to indicate when a temperature of a heater 950 (as determined by a temperature sensor 952) changes more than a predetermined amount over a predetermined period of time when the heater 950 is maintained at a given power level. The predetermined amount of change and the predetermined period of time can be set, altered or deleted through the HMI 170. It is noted that the foregoing has outlined some of the more pertinent non-limiting embodiments. It will be clear to those skilled in the art that modifications to the disclosed non-embodiment(s) can be effected without departing from the spirit and scope thereof. As such, the described non-limiting embodiment(s) ought to be considered to be merely illustrative of some of the more prominent features and applications. Other beneficial results can be realized by applying the non-limiting embodiments in a different manner or modifying them in ways known to those familiar with the art. This includes the mixing and matching of features, elements and/or functions between various non- limiting embodiment(s) is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as skill in the art would appreciate from this disclosure that features, elements and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise, above. Although the description is made for particular arrangements and methods, the intent and concept thereof may be suitable and applicable to other arrangements and applications.