Closed loop control of auxiliary injection unit

ES 2 804 802 T3

DESCRIPTION

Auxiliary injection unit closed-loop control

Field of the invention

The invention relates generally to co-injection molding systems having an auxiliary injection unit for co-injection or multi-material applications. More particularly, the invention relates to the closed-loop control of the auxiliary injection unit.

Background of the invention

It is known in the injection molding art to simultaneously or sequentially inject two molten streams of moldable material into a mold cavity using a single hot runner injection molding nozzle, which is commonly known as co-injection. A first injection molding machine can provide a first casting stream of a first moldable material, which may be referred to as a primary injection unit, while a second casting stream of a second moldable material can be provided by an auxiliary injection unit. The first and second melt streams are fed from their respective injection units into the respective first and second melt channels or conduits of a manifold which are also in fluid communication with the respective separate first and second melt channels from the nozzle to through which the casting streams are directed into the mold cavity.

During a coinjection molding operation, controlling the flow of each of the first and second casting streams in the mold cavity is crucial to producing consistent multi-layer parts. Conventionally, an open circuit control of the molding process has been provided whereby the primary injection unit can send a signal or such to the auxiliary injection unit, the receipt of which triggers the start of injection of the second stream of casting by the auxiliary injection unit. The drive signal can be configured to allow sequential or simultaneous injection of the first and second melt streams by the primary and auxiliary injection units. The drawback of open loop control is that it does not provide any mechanism whereby the actual molding conditions presented by the flow of the first stream of melt injected by the primary injection unit can influence start, speed and / or pressure. of the flow of the second stream of melt injected by the auxiliary injection unit. Without such real-time closed-loop control of the auxiliary injection unit, co-injected molded parts may occur having layers with inconsistent thickness and / or improper / undesirable relative positioning. Document WO 2007/140447 A1 describes a method and apparatus for a sequential injection molding process that delivers a first shot of a first material simultaneously to a plurality of cavities in the mold, independently stopping the step of delivering the first material when a material flow volume has been reached, and delivering a second shot of a second material simultaneously to the cavities after stopping the first shot to each cavity of the mold. US 5 922 255 A discloses a large part injection molding having at least two mold gates, in which a first quantity of resin is first injected into a first mold gate and a second quantity of the same resin. it is injected second into a second gate of the mold, away from the first gate of the mold.

Multi-material molding is another type of molding operation in which a primary injection unit and an auxiliary injection unit are used to supply the material required to make products, such as toothbrushes that have a handle made of a harder first material and a gripping surface of a second softer material, and automobile lenses having a first colored portion, for example a clear material, which forms the main portion of the lens having a void in which a second colored portion, for example, of an amber material, is cast. These types of multi-material molding applications can use a shrink core, called tyrannosaurs to create a vacuum into which the second material is injected. Other multi-material operations may use a mobile rotary platen with multiple mold stations that mold various features into a single product as each station engages a stationary half of the mold. Additionally, rotary stack molding in which a central block of a stacked mold rotates or rotates to engage the different faces of the central block with a stationary half of the mold to define different characteristics of the part being molded, is another way of overmolding of multiple materials. In each multi-material application, a first injection molding machine can provide a first melt stream of a first moldable material, while a second melt stream of a second moldable material can be provided by an auxiliary injection unit, in such a way that, similar to the coinjection molding operation described above, Controlling the flow of each of the first and second casting streams in the respective mold cavity is crucial to producing consistently co-injected or multi-material castings.

Accordingly, there exists a need in the art for an injection molding system that provides real-time communication of a condition of a first melt stream from a primary injection unit to provide synchronized or slave injection of a second melt stream from an auxiliary injection unit.

ES 2 804 802 T3

Brief summary of the invention

The embodiments herein relate to a method and apparatus for controlling the start of an injection of a melt stream of moldable material from an auxiliary injection unit. In one embodiment, a sensor is placed in an injection molding system to detect a condition related to the injection of a first melt stream of a first moldable material provided by a primary injection unit. The start of a second melt stream of a second moldable material from the auxiliary injection unit is initiated when the condition related to the injection of the first melt stream is detected at a preselected value, in which the detected condition may be a pressure, velocity or temperature of the first melt stream provided by a direct sensor, a force or tension in a hot runner component as provided by an indirect sensor, or the occurrence of an injection molding system function as provided by a functional sensor. In embodiments thereof, when the detected condition reaches the preselected value, a signal is sent which directly or indirectly through a time delay begins the injection of the second melt stream from the auxiliary injection unit.

Brief description of the drawings

The above and other features and advantages of the invention will be apparent from the following description of the embodiments thereof as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the relevant art to make and use the invention. Drawings are not to scale.

Figure 1 is a schematic representation of a co-injection molding system having closed-loop control of an auxiliary injection unit in accordance with one embodiment herein.

Figure 2 represents a graph showing the relationship between a pressure or speed of an injection of a first melt stream of moldable material from a primary injection unit and a pressure or speed of an injection of a second melt stream of moldable material. from an auxiliary injection unit over time that can be provided by the system of Figure 1 according to a simultaneous co-injection embodiment herein.

Figure 3 represents a graph showing the relationship between a pressure or speed of an injection of a first melt stream of moldable material from a primary injection unit and a pressure or speed of an injection of a second melt stream of moldable material. from an auxiliary injection unit over time that can be provided by the system of Figure 1 according to a sequential co-injection embodiment herein.

Figure 4 represents a graph showing the force / deformation relationship of an injection of a first melt stream of moldable material from a primary injection unit into a hot runner component, and a pressure or velocity of an injection of a second melt stream of moldable material from an auxiliary injection unit over time that can be provided by the system of Figure 1 in accordance with another embodiment of simultaneous co-injection herein.

Figure 5 represents a graph showing the relationship between a pressure or speed of an injection of a first melt stream of moldable material from a primary injection unit and a pressure or speed of an injection of a second melt stream of moldable material. from an auxiliary injection unit over time having a preset time interval feedback setting of the second mold stream that can providing the system of Figure 1 according to a simultaneous co-injection embodiment herein.

Figure 6 is a schematic representation of a multi-material injection molding system having closed-loop control of an auxiliary injection unit in accordance with another embodiment herein.

Figures 7A-7C depict exemplary preforms molded by co-injection procedures described in embodiments herein.

Figure 8 represents a graph showing the relationship between a pressure or speed of an injection of a first melt stream of moldable material from a primary injection unit and a pressure or speed of an injection of a second melt stream of moldable material. from an auxiliary injection unit over time having the injection stage feedback setting as the system of Figure 1 can provide according to a simultaneous co-injection embodiment of the present document.

Detailed description of the invention

The specific embodiments are described below with reference to the figures. The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention.

ES 2 804 802 T3

In the following description, downstream is used with reference to the direction of flow of mold material from an injection unit to a mold cavity of an injection molding system, and also to the order of components or characteristics thereof to through which the mold material flows from an injection unit to a mold cavity, while upstream is used with reference to the opposite direction. While the description of embodiments herein is in the context of co-injection and multi-material applications of a hot runner injection molding system, the invention may also be used in other molding arrangements where it is considered Useful. Likewise, there is no intention of being linked to any express or implicit theory presented in the previous technical field, in the background, brief summary or in the following detailed description.

Figure 1 is a schematic representation of an injection molding system 100. The injection molding system 100 includes a hot half 101 for directing the melt from two separate melt sources S1, S2 to one or more mold cavities 106 formed between the hot half 101 and the cold half 103. Accordingly, the injection molding system 100 is a co-injection system that includes a primary injection unit 104 for providing a first melt stream of a first moldable material S1 to a mold cavity 106 and an auxiliary injection unit 102 for providing a second melt stream of a second moldable material S2 to the mold cavity 106. In accordance with one embodiment herein, the injection molding system 100 includes closed-loop control of the auxiliary injection unit 102 as described below. In one embodiment, the primary injection unit 104 is an injection molding machine and the auxiliary injection unit 102 is an auxiliary injection unit that is coupled to the injection molding machine or a mold supported by or is arranged on a floor stand placed next to the machine. In an alternative embodiment, an injection molding system according to the present includes closed-loop control of multiple auxiliary injection units.

The primary injection unit 104 feeds the first melt stream into a first set of hot channels or melt channels 108 of the injection molding system 100 that extend between a first inlet 107 and a mold gate 109 of the cavity 106 of the mold inside half 101 hot. The auxiliary injection unit 102 feeds the second melt stream into a second set of hot runners or melt channels 110 of the injection molding system 100 that extend between a second inlet 111 and the mold gate 109 of the cavity 106 of the mold inside half 101 hot. One skilled in the art will understand that the first and second sets of hot channels 108, 110 are cast channels that may extend into or be defined by various hot channel components, such as inlet or injection nozzles 120, 120 ', one or more. plus manifolds, such as manifold 122, and a heated or valved nozzle, such as nozzle 124 with heated gate or nozzle 124 'with gate valve, and that each of the first and second melt streams flow separately through the various components of the hot runner to meet near or within the mold cavity 106. While a portion of the first or second casting channels 108, 110 is shown extending within a single manifold 122 this is by way of illustration and not limitation. One skilled in the art will also understand that the system 100 is shown with only two mold cavities 106 for simplicity and that more or fewer mold cavities 106 can be positioned to receive the first and second melt streams thus provided, depending on the type and number of molded articles being produced and that an actual injection molding system based on system 100 may have all nozzles 124 with heat gate or all nozzles 124 'with gate valve and not one or more of each as illustrated by way of illustration in Figure 1.

A sensor 114 is used within the injection molding system 100 to allow closed loop operation between the primary injection unit 104 and the auxiliary injection unit 102. In the embodiment shown in Figure 1, sensor 114 is connected near the first input 107 of the first set of channels 108. Sensor 114 is a direct melt stream sensor mounted to be in direct contact with the first melt stream flowing through channels 108 to directly monitor a condition of the melt flowing therethrough. Sensor 114 may be selected to monitor a condition of the melt stream such as the pressure, temperature, or velocity of the first melt stream as it flows through the first set of channels 108. In one embodiment, sensor 114 is one of a pressure or velocity sensor positioned within the first set of hot channels 108 to obtain a direct reading of a respective condition of the first melt stream such as the pressure or velocity of the melt. injected by the primary injection unit 104. In another embodiment, the sensor is a temperature sensor positioned within the first set of hot channels 108 to obtain a direct reading of the state of the first melt stream, such as a temperature change attributed to shear heating of the melt at as it flows through the first set of hot channels 108 as a result of injection of melt by the primary injection unit 104. In Figure 1, the location shown for sensor 114 generally corresponds to a position along a casting channel of the respective casting inlet or injection nozzle 120. In alternate embodiments herein also shown in Figure 1, sensor 114 can be arranged anywhere along the melt path of the first melt stream as it flows into the hot half 101 to be included. along a melt channel of manifold 122, as represented by sensor 114a, or a melt channel of nozzle 124 ', as represented by sensor 114b. In another embodiment, a direct melt current sensor is one of sensors 114g, 114g 'located on core plate 126 or cavity plate 128, respectively, in order to obtain a direct reading of the respective state of the melt

ES 2 804 802 T3 within mold cavity 106 during injection.

In another embodiment, an indirect sensor such as a force / strain gauge located at a point along an external surface of a hot runner component can be used in system 100 to provide closed-loop operation between drive unit 104. primary injection and auxiliary injection unit 102. Sensor 114d shown mounted on manifold 122 and sensor 114e shown mounted on nozzle 124 'are indirect sensors insofar as they are disposed on an external surface of a hot runner component such as a nozzle, manifold or Inlet extension / injection nozzle to indirectly detect a condition of the first melt stream that is displayed as a measurable movement or change in the respective hot runner component. The measurable movement of the component, which may be a minor distortion or bending of the injection molding system that occurs as a result of pressurization of the melt within the first set of channels 108, is the sensed condition perceived by the sensor 114d, 114e indirect which would indirectly indicate the condition of the first melt stream being injected by the primary injection unit 104 without having to directly detect the condition of the first melt stream.

In another embodiment, a functional sensor disposed within the injection molding system 100 that detects the occurrence of a function within the injection molding system 100 can be used to provide closed-loop operation between the primary injection unit 104 and the unit. 102 auxiliary injection. An example of a functional sensor includes a valve pin actuator position sensor 114f associated with the gate valve nozzle 124 '. Position sensor 114f is disposed within system 100 to monitor a function such as the activity of a valve pin actuator and subsequently a valve pin 130 coupled thereto as the actuator cycles between open positions. and closed to control the flow of the first casting stream provided by the primary injection unit 104 in the mold cavity 106. Accordingly, the sensed condition perceived by the functional sensor 114f may be the movement of the valve pin actuator to a preselected position, such as an open or closed position.

Another example of a functional sensor includes a force / strain gauge mounted on or between the hot runner components of the hot half 101, such as sensor 114c shown mounted on injection nozzle 120 proximate manifold 122. The sensor 144c measures or senses the force of a machine nozzle that is in contact with the injection nozzle 120. The location of sensor 114c shown in Figure 1 may be particularly beneficial in certain injection molding applications where the nozzle / machine carriage of the primary injection unit 104 retracts from the hot runner inlet 107 between every injection cycle. In another embodiment, sensor 114c may be mounted on injection nozzle 120 proximate inlet 107. Examples of these types of injection molding applications include thin-walled article molding and / or stack molding. In such applications when the mold is opened to eject parts, the machine nozzle retracts from the inlet 107 to decompress the system so that melt exiting the heat gate nozzles 124 is minimized and / or to relieve stress. shock in the hot runner system during the closing of the mold. To begin the next injection cycle, the mold is closed, in which the nozzle of the machine contacts the inlet 107 of the hot runner, which is the sensed condition perceived by the functional sensor 114c, and the cycle of injection of the primary injection unit 104.

Each of the above sensor locations represented by sensors 114, 114a-114g, 114g 'would be suitable for co-injection molding applications, such as those used to mold a plastic bottle preform (as shown in the mold cavity 106) in which there is an intermediate layer of a barrier material provided by the auxiliary injection unit 102 that is positioned between the inner layers and external surfaces of a surface material provided by the primary injection unit 104.

Typically, an injection of the first melt stream begins by the primary injection unit 104 and the condition of the melt flowing through the first set of channels 108 is monitored (directly or indirectly) as previously described by at least one of the sensors 114, 114a, 114b, 114d, 114e, 114g, 114g '. Additionally, one or more functions of the injection molding system can be monitored in place or simultaneously as described above by at least one of the sensors 114c and 114f. Continuous monitoring of the condition of the melt and / or of the functions of the injection molding system 100 by one of the sensors 114-1 Mg 'allows the auxiliary injection unit 102 to be a slave, in real time, to the actual output from primary injection unit 104. More particularly, when a preselected value for the sensed condition (direct or indirect) of the first casting stream is reached, and / or an injection molding system function occurs, a signal is sent to a controller 150 of the unit. Auxiliary Injection 102 to begin injection of the second melt stream relative to an actual time, speed, and / or pressure of the first melt stream. In an alternative embodiment in an injection molding system in accordance with the present document, when a preselected value is reached for the sensed condition (direct or indirect) of the first melt stream, and / or a function of the casting system occurs. injection molding, A signal is sent to multiple controllers 150 of the respective auxiliary injection units 102 to begin the injection of the respective melt streams relative to an actual time, speed, and / or pressure of the first melt stream.

In one embodiment, when a preselected value is reached for the sensed condition (direct or indirect) of the

ES 2 804 802 T3 first melt stream, and / or an injection molding system function occurs, a signal is sent to the controller 150 which will then start a timer 152 to delay the injection of the second melt stream by the unit 102 of auxiliary injection in a preset period of time. Reducing the start of injection of the second melt stream provided by the auxiliary injection unit 102 to the sensed conditions of the first melt stream by the primary injection unit 104 ensures that the start of the second melt stream is related with an actual time, speed and / or pressure of the first melt stream.

Figure 2 is a graph showing the relationship between a pressure P or velocity V of the first casting stream of moldable material from the primary injection unit 104 (Inj P) and a pressure P or velocity V of the second casting stream of moldable material from the auxiliary injection unit 102 (Inj A) over time T as can be provided by the system of Figure 1 according to a simultaneous co-injection embodiment herein. The features and aspects of the other embodiments can be used in accordance with the current embodiment. In this embodiment, when Inj P reaches a preselected pressure value Ps or preselected velocity value Vs as detected by one of the direct sensors 114, 114a, 114b, 114g, 114g ', a signal will be provided to the unit controller 150 102 auxiliary injection to start injection A. A delay of a period Ti of time occurs between the beginning of Inj P and the beginning of Inj A, which corresponds to the time taken by the pressure P or the velocity V of the melt in the first melt stream to reach the value Ps of preset pressure or preset velocity Vs value. Inj P and Inj A continue for an Inj T period of time. Subsequently, Inj P and Inj A are held for a period of time sufficient to allow packing of the mold cavity 106. One skilled in the art will understand that injection pressure and speed depend on the shape, size and number of parts that are molded and the resins that are used to mold the part. In addition, the total injection time is not a set time, but depends on variables such as the movement of the screw and the shape, size and number of parts that are molded.

With reference to Figures 1 and 2 in the simultaneous co-injection embodiment described above, when the preselected value of the detected condition of the first melt stream is detected by at least one of the sensors 114, 114a, 114b, 114g, 114g ' direct, the sensor sends a signal to the controller 150 that directly activates the start of the auxiliary unit 104. In another embodiment, when the preselected value of the detected condition of the first melt stream is detected by at least one of the direct sensors 114, 114a, 114b, 114g, 114g ', the sensor sends a signal to the controller 150 that activates the timer 152 which subsequently triggers the start of auxiliary unit 104 after a preset period of time has elapsed. Similarly, indirect sensors 114d, 114e can be used to indirectly sense the onset of melt flow from primary injection unit 104 by detecting a preselected force or strain in a hot runner system component at which time it would be shipped. a signal to the controller 150 that the melt flow would start from the auxiliary injection unit 104 at one time, velocity and pressure relative to the first melt stream, either immediately or after the timer 152 period expires.

Figure 3 represents a graph showing the relationship between a pressure P or velocity V of a first melt stream of moldable material from the primary injection unit 104 during a first and second injection cycles, represented by the profiles (1), (1 ') of the injection cycle, and a pressure P or velocity V of a second melt stream of moldable material from the auxiliary injection unit 102 during an auxiliary injection cycle, represented by the injection cycle profile (2), over time T as can be provided by the system 100 of Figure 1 according to a sequential co-injection embodiment. The features and aspects of the other embodiments can be used in accordance with the current embodiment. The depicted sequential injection cycle profiles (1), (1 ') and (2) shown in Figure 3 are suitable for forming a molded article, such as, for example, a preform, having inner and outer layers of a first material provided by primary injection unit 104 and an intermediate or barrier layer of a second material provided by auxiliary injection unit 102. In this embodiment, when a first shot of the first material from the primary injection unit 104 reaches a preselected pressure value Ps or preselected velocity value Vs detected by at least one of the sensors 114, 114a, 114b, 114g, 114g 'direct, and as indicated in the profile (1) of the injection cycle that represents the first injection of an internal or external layer of the molded article, a signal will be provided that activates the timer 152. After passing a preset period Ti of time which, in the current non-limiting embodiment, ends just before the completion of the first injection, an injection of the second material begins from the auxiliary injection unit 102, which is represented by the cycle profile of the injection (2), to provide the intermediate layer or barrier of the molded article. In turn, after the stage of a second time period T2 that ends just before completing the injection of the second material, the second injection of the first material is started from the primary injection unit 104, which is represented by the profile ( 1 ') of the injection cycle, to provide an outer or inner layer of the molded article.

Figure 4 represents a graph showing the relationship between the force / strain profile (Force / Strain, F / S) experienced by a hot runner component in the injection molding system 100 due to an injection of the unit 104 of primary injection, which is represented by the profile (1) of the injection cycle and a pressure or velocity profile of a second melt stream of moldable material from the auxiliary injection unit 102, represented by the profile (2) of the injection cycle, over time T as can be provided by the system of Figure 1 according to a simultaneous co-injection embodiment. The simultaneous co-injection profiles depicted in Figure 4 are suitable for forming a molded article, such as, for example, a preform,

ES 2 804 802 T3 having an inner and outer layer of a first material provided by the primary injection unit 104 and an intermediate or barrier layer of a second material provided by the auxiliary injection unit 102.

In the embodiment of Figure 4, an injection of the first material from the primary injection unit 104 produces a measurable amount of force / deformation in the injection molding system 100 that is exhibited as bending or distortion in one or more of the component 120. inlet, manifold 122 and nozzle 124. When an indirect sensor, such as a strain gauge, arranged on its respective surface detects a preselected amount of force Fs or strain Ss as indicated in the injection cycle force / strain profile (1), which corresponds to the injection of a first melt stream of a first material that will form an inner and outer layer of the molded article, a signal will be provided to controller 150 that activates timer 152. After the passage of a preset period Ti of time, an injection of a second melt stream of a second material begins from the auxiliary injection unit 102, which is represented by the pressure / speed profile (2) of the injection cycle, to provide the intermediate layer or barrier of the molded article.

In the embodiments of Figures 2-4 generally, the signal is sent to the controller 150 of the auxiliary injection unit 102 as the monitored condition of the first melt stream (pressure, velocity, temperature, force, or strain) rises. at a preset value suitable to begin injection of the second melt stream from the auxiliary injection unit 102. One skilled in the art will also understand that the preset value at which a signal is sent to the controller 150 can occur at any point during the injection cycle, such as when the monitored condition of the first melt stream (pressure, speed, temperature, force or deformation) rises to a preset value, falls to a preset value, or reaches a maximum or minimum preset value.

In another embodiment, the pressure P or velocity V of the first melt stream provided by the primary injection unit 104 may be measured after the passage of various time intervals during the primary injection cycle to provide active injection adjustment. auxiliary in response to each pressure P or velocity V detected. Figure 5 represents a graph showing the relationship between the pressure P or the velocity V of the first melt stream of moldable material from the primary injection unit 104 represented by the profile (1) of the injection cycle and a pressure P or velocity V of the second casting stream of moldable material from auxiliary injection unit 102, represented by the injection cycle profile (2) over time T having an active setting after each of the preset time intervals Ti as can be provided by the system of Figure 1 according to a simultaneous co-injection embodiment of this document. Such an embodiment provides feedback of the preset time interval of a sensed condition of the first melt stream to the auxiliary injection unit 102 upon which the injection adjustment of the second melt stream can be based as it would affect a pressure P or velocity V of the second melt stream. The features and aspects of the other embodiments can be used in accordance with the current embodiment.

Once the injection of the first material from the primary injection unit 104 reaches a preselected pressure value Ps or preselected velocity value Vs detected by at least one of the direct sensors 114, 114a, 114b, 114g, 114g ', it will be provided a signal to the controller 150 of the auxiliary injection unit 102 to begin injection of the second melt stream. A delay of a period Ti of time occurs between the beginning of the injection by the primary injection unit 104 and the beginning of the injection by the auxiliary injection unit 102 which corresponds to the time it takes for the pressure P or the speed V of the melt in the first melt stream to reach the preselected pressure value Ps or the preselected velocity value Vs. Instead of sending a single signal to the auxiliary injection unit 102 regarding when to begin injection of the second melt stream, the controller 150 actively monitors the pressure P or velocity V measurements provided by one of the sensors 114, 114a. , 114b, 114g, 114g 'direct after each interval Tj of specified time, for example, after a time interval of 0.1 seconds, from the time Ti that corresponds to the beginning of the auxiliary injection as represented in Figure 5. From the start of injection by the auxiliary injection unit 102, the controller 150 takes a direct reading from one of the direct sensors 114, 114a, 114b, 114g, 114g 'at 0.1 second intervals, for example, and instructs the auxiliary injection unit 102 to actively adjust the pressure P or the velocity V of the second melt stream as shown in the injection cycle profile (2) in response to the sensed condition of the melt in the first melt stream in each interval as represented by the profile (2) of the injection cycle. Although the second melt stream represented by the profile (2) of the injection cycle is shown as proportionally adjusted relative to the first melt stream represented by the profile (1) of the injection cycle this is by way of illustration and not as limitation.

Figure 6 is a schematic representation of an injection molding system 600. The injection molding system 600 includes a hot half 601 for directing the casting from two sources S1, S2 into one or more mold cavities 606a, 606b formed between the hot half 601 and the cold half 603. The injection molding system 600 is a multi-material injection molding system that includes a primary injection unit 604 for providing a first melt stream of a first moldable material S1 to a mold cavity 606a and an injection unit 602. assist in providing a second melt stream of a second moldable material S2 to a mold cavity 606b, in accordance with one embodiment herein. The features and aspects of the other embodiments can be used in accordance with the current embodiment. The 600 molding system

ES 2 804 802 T3 by injection includes closed loop control of the auxiliary injection unit 602 as described below. In one embodiment, the primary injection unit 604 is an injection molding machine and the auxiliary injection unit 602 is an auxiliary injection unit that is coupled to the injection molding machine or a mold supported by or is arranged on a floor stand placed next to the machine.

The primary injection unit 604 feeds the first melt stream into a first set of hot channels or melt channels 608 of the injection molding system 600 that extends between a first inlet 607 and a gate 609a of the mold cavity 606a of the mold inside hot 601 half. After rearranging the mold, such as by retracting, rotating, or rotating the core plate 626 to provide the mold cavity 606b, the auxiliary injection unit 602 feeds the second melt stream into a second set of hot runners or melt runners 610. of the injection molding system 600 extending between a second inlet 611 and the mold gate 609b of the mold cavity 606b within the hot half 601. One skilled in the art will understand that the first and second sets of hot channels 608, 610 are cast channels that can extend into or be defined by various hot channel components, such as an inlet or injection nozzles 620, 620 ', one or more. plus manifolds, such as manifold 622, 622 ', and a gate valve or heated nozzle, such as nozzles 624a, 624b with heated gate or 624a' nozzle, 624b 'with gate valve and that each of the first and second melt streams flow separately through the various components of the hot runner to the respective mold cavity 606a, 606b. Although a portion of the first and second casting channels 608, 610 is shown extending into separate manifolds 622, 622 'this is by way of illustration and not limitation. In another embodiment, a portion of the first and second casting channels 608, 610 extends separately within a single manifold as in the embodiment of Figure 1. One skilled in the art will also understand that the system 600 is shown with only two mold cavities 606a, 606b to form only two multi-material parts for simplification and that more or fewer mold cavities 606a, 606b (not shown) can be positioned. to receive the first and second melt streams thus provided, depending on the type and number of molded articles that are produced. Furthermore, one of ordinary skill in the art will understand that an actual injection molding system based on system 600 may have all nozzles 624a, 624b with heat gate or all nozzles 624a ', 624b' with gate valve and not one or more of each as illustrated by way of illustration in Figure 6.

A sensor 614 is used within the injection molding system 600 to allow closed loop operation between the primary injection unit 604 and the auxiliary injection unit 602. In the embodiment shown in Figure 6, sensor 614 is connected near the first input 607 of the first set of channels 608. Sensor 614 is a direct sensor mounted to be in direct contact with the first stream of melt flowing through channels 608 to directly monitor a condition of the melt flowing therethrough. Sensor 614 may be selected to monitor a condition of the melt stream such as the pressure, temperature, or velocity of the first melt stream as it flows through the first set of channels 608. In one embodiment, Sensor 614 is one of a pressure or velocity sensor positioned within the first set of hot runners 608 to obtain a direct reading of the respective condition of the first melt stream, such as a change in pressure or velocity. attributed to injection of the melt by the primary injection unit 604. In another embodiment, sensor 614 is a temperature sensor positioned within first set of hot channels 608 to obtain a direct reading of the respective state of the first melt stream, such as a change in temperature attributed to shear heating of the dough. melt as it flows through the first set of hot channels 608 as a result of the injection of the first melt stream by the primary injection unit 604. In Figure 6, the location shown for sensor 614 generally corresponds to a position along a casting channel of the respective casting inlet or injection nozzle 620. In alternate embodiments herein also shown in Figure 6, the direct melt stream sensor can be arranged anywhere along the melt path of the first melt stream as it flows into the middle. 601 hot to be included along a manifold melt channel 622, as represented by sensor 614a, or a nozzle melt channel 624a ', as represented by sensor 614b.

In another embodiment, the direct melt current sensor is one of the sensors 614g, 614g 'located on the core plate 626 or cavity plate 628, respectively, to obtain a direct reading of the respective state of the melt. within mold cavity 606a, 606b during injection.

In another embodiment, the sensor may be an indirect sensor such as a force / strain gauge located at a point along an external surface of a hot runner component, such as sensor 614d shown mounted on manifold 122. and sensor 614e shown mounted on nozzle 624a '. Sensors 614d, 614e are indirect sensors insofar as they are arranged on an external surface of a hot runner component, such as a nozzle, manifold, or inlet / injection nozzle extension to indirectly detect a first melt stream condition displayed as a measurable movement or change in the respective hot runner component. The measurable movement of the component, which may be a minor distortion or bending of the injection molding system that occurs as a result of the pressurization of the melt within the first set of channels 608, is the sensed condition perceived by the sensor 614d, 614e indirectly that would indirectly indicate the condition of the first melt stream being injected by the primary injection unit 604 without having to directly detect the condition of the first melt stream.

ES 2 804 802 T3

In another embodiment, the sensor may be a functional sensor disposed within the injection molding system 600 to detect the appearance of a function within the injection molding system 600. An example of a functional sensor includes a valve pin actuator position sensor 614f associated with the gate valve nozzle 624a 'positioned to monitor a function such as valve pin actuator activity and simultaneously a valve pin 630. valve coupled thereto as the actuator cycles between open and closed positions to control melt flow provided by injection unit 604 primary in mold cavity 606a. Accordingly, the sensed condition sensed by functional sensor 614f may be movement of the valve pin actuator to a preselected position, such as an open or closed position.

Another example of a functional sensor includes a force / strain gauge mounted on the hot runner components of the hot half 601, such as the sensor 614c shown mounted on the injection nozzle 620 proximate the manifold 622 such that the Force of a machine nozzle contacting injection nozzle 620 will be measured by sensor 614c. The location of the sensor 614c can be particularly beneficial in certain injection molding applications where the nozzle / machine carriage of the primary injection unit 604 retracts from the hot runner inlet 607 between each injection cycle. In another embodiment, sensor 614c may be mounted on injection nozzle 620 near inlet 607. Examples of these types of injection molding applications include thin-walled article molding and / or stack molding. In such applications when the mold is opened to eject parts, the machine nozzle retracts from inlet 607 to decompress the system so as to minimize melt exiting heat gate nozzle 624a and / or to relieve pressure. shock in the hot runner system during the closing of the mold. To begin the next injection cycle, the mold is closed, in which the nozzle of the machine contacts the inlet 607 of the hot runner, which is the sensed condition perceived by the functional sensor 614c, so that the injection cycle of primary injection unit 604. Each of the above sensor locations represented by sensors 614, 614a-614g, and 614g 'would be suitable for a multi-material molding application such as those used in automotive lens molding, for example.

A multi-material injection molding application in accordance with the embodiment herein may utilize the functional sensor 614f to trigger the injection from the auxiliary injection unit 102. More particularly, the functional sensor 614f is positioned to monitor the activity of an actuator and simultaneously the valve pin 630 coupled thereto as the actuator cycles between the open and closed positions to control the flow of melt provided by the primary injection unit 604 in the mold cavity 606a. In one embodiment, the functional sensor 614f is configured to detect the open position of the actuator associated with the first melt stream provided by the primary injection unit 604. Upon sensing that the actuator changes to an open position, a signal is sent to controller 650 to start timer 652 to begin a preset period of time including a period of time that begins upon completion of the primary injection cycle associated with unit 604 primary injection and during which the mold is altered to create mold cavities 606b, such as by retracting the core or rotating / flipping the mold to align another part of the mold. After the preset period of time has elapsed, the secondary injection cycle begins from the auxiliary injection unit 602 to inject the second stream of melt into the mold cavities 606b through the second set of hot channels 610.

In general for the embodiments described herein, one of the sensors 114, 114a-114g and 114g 'of the embodiment of Figure 1 and one of the sensors 614, 614a-614g and 614g' of the embodiment of Figure 6 , such as a pressure sensor 114, 614 positioned to directly detect a condition of the first melt stream injected by the respective primary injection unit 104, 604, transmits an analog signal (current or voltage, 0-10v) to a controller 150, 650 Programmable Logic Controller (PLC) of the respective auxiliary injection unit 102, 602. The PLC 150, 650 has an analog input card to convert the analog signal to a digital signal that will activate the auxiliary injection unit 102, 602 to start an auxiliary injection, as described above, or start the timer 152, 652 which It will delay the auxiliary injection for a preset period of time.

In many cases, due to the lack of a machine language standard in the injection molding industry, whenever an auxiliary injection unit is incorporated into an existing injection molding machine, there is some customization of the controller of the injection molding machine that is necessary to enable communication between the injection molding machine and the auxiliary injection unit. In other cases, the auxiliary injection unit is activated by a EUROMAP signal or an SPI signal provided by the injection molding machine. In any case, an amount of customization, which is often time consuming, is involved each time an auxiliary injection unit is connected to an injection molding machine so that the auxiliary injection unit receives an output signal from the unit. primary injection unit telling the auxiliary injection unit when to start. Although, in ideal circumstances, the start time of an injection cycle by the auxiliary injection unit relative to the start of the injection cycle by the primary injection unit should generally be constant, if the auxiliary injection unit relies on a signal from the machine to start the injection, Any variation in the actual injection profile of the primary injection unit relative to the programmed or desired injection profile can cause the auxiliary injection unit to start too early or too late, which can cause inconsistent thicknesses and / or relative positioning. wrong / undesirable of the two materials within the mold cavity.

ES 2 804 802 T3

An advantage of using the sensors 114, 114a-114g or 114g 'or the sensors 614, 614a-614g and 614g' as described in the previous embodiments, the auxiliary controller 150, 650 of the injection unit 102, 602 Auxiliary does not need to be connected to the machine controller of the primary injection unit 104, which saves time and eliminates the need for customization, thus making such systems according to embodiments herein easily adaptable to many injection molding applications.

In one embodiment, a safety feedback sensor that can confirm that an injection of the first melt stream has occurred by the primary injection unit 104, 604 as a live injection may be useful in embodiments herein, such as in cases where the controller 150, 650 would like to ensure that a live injection cycle had occurred prior to triggering of the injection by the auxiliary injection unit 102, 602. Such a safety feedback sensor would ensure that the auxiliary injection unit 102, 602 would not start an injection of the second material when it is not desirable to do so. For example, while embodiments herein contemplate one of sensors 114, 114a-114g or 114g 'or sensors 614, 614a-614g and 614g' that are used to provide closed loop control between unit 104, 604 of primary injection and auxiliary injection unit 102, 602, two sensors can be used in conjunction with each other, and the second sensor serves as a safety feedback sensor. In a non-limiting example, a functional sensor, such as valve pin actuator sensor 114f, 614f, which is used to determine the open and closed positions of an actuator, provides a signal to controller 150, 650 which is then used to providing closed-loop control of the auxiliary injection unit 102, 602. Since the valve pins can be actuated between the open and closed positions at times when the primary injection unit 104, 604 does not inject the melt, such as during the configuration of the injection molding system 100, 600 a pressure sensor safety feedback such as indirect sensor 114e, 614e can be used to control the force / strain on nozzle 124, 624 such that unit 102, 602 The auxiliary injection system cannot inject unless the deformation in the nozzle 124, 624 meets or exceeds a preset value indicative of a live injection of the primary injection unit 104. In such a case, the indirect sensor 114e, 614e acts as a safety feedback sensor by confirming that an injection has started.

Figures 7A-7C depict molded portions 770a, 770b, 770c formed by an exemplary simultaneous coinjection molding application provided by injection molding system 100 in accordance with embodiments herein. The features and aspects of the other embodiments can be used in accordance with the current embodiment. During the setup of the injection molding system 100 within an injection molding machine (not shown), an operator enters information associated with the manufacture of a specific part into a user interface of an associated machine controller (not shown). with the primary injection unit 104 and a controller user interface 150 associated with the auxiliary injection unit 102. Figures 7A-7C depict the formation of 20 gram preforms 770a, 770b, 770c for subsequent blow molding into a beverage container or the like, having an inner and outer layer of polyethylene terephthalate (PET) comprising 90 % of the total weight of the part supplied by the primary injection unit 104, as well as a barrier layer of ethyl and vinyl alcohol (EVOH) that comprises the remaining 10% of the total weight of the part supplied by the auxiliary injection unit 102. In one embodiment, the preforms 770a, 770b, 770c are molded in a mold having 32 cavities (not shown) and as such, the operator will provide information to the injection molding machine controller that controls the primary injection unit 104 to inject an injection volume of 576 grams (18 g x32). The operator will then enter controller 150 to inject a 64 gram (2g x32) shot volume.

With the hot half 101 and the cold half 103 of the injection molding system 100 joined between the fixed and moving platen of an injection molding machine, as one skilled in the art would understand, a first shot of melt is delivered to the mold cavities 106 from the primary injection unit 104 through the first set of channels 108. As described in the previous embodiments, at least one sensor 114, 114a, 114b, 114g, and 114g 'direct in communication with the controller 150 is positioned to directly detect a melt condition related to the injection of the first stream of casting by the primary injection unit 104. Once at least one direct sensor 114, 114a, 114b, 114g, and 114g 'detects a preselected value of the condition of the first melt stream, controller 150 sends a signal to auxiliary injection unit 102 to begin injection. Alternatively, upon receiving the signal that the preset value has been reached, controller 150 will start timer 152 which, after a programmed delay, will send a signal to auxiliary injection unit 102 to begin injection. Once the primary and auxiliary injection units 104, 102 have delivered their required shots of molding material to the mold cavity 106, the newly molded articles are cooled within the mold 106 until they have sufficiently solidified. The hot half 101 and the cold half 103 are separated by the separation of the moving and fixed platen of the injection molding machine, and the newly molded articles are ejected from the mold. The machine operator will inspect one or more of the newly molded articles to assess the position of the barrier layer within the inner and outer layers.

In an exemplary embodiment, the preselected value to begin injection of the second melt stream by the auxiliary injection unit 102 is the detection of a pressure of 15,000 PSI by a direct sensor that corresponds to the beginning of the first melt stream flow from primary injection unit 104. The preset can be adjusted after inspection of the molded preform, either gradually changing the preset to activate auxiliary injection, for example, +/- 1000 PSI or by setting timer 152 for 0.10 second increments to delay the auxiliary injection and thus control the distribution of the

ES 2 804 802 T3 barrier within the preform. In an alternative embodiment, a pressure of 10,000 PSI is a preset value to start the timer 152 which is set to 0.50 seconds, for example, and after inspection of the molded preform, the timer can be set, for example, +/- 0.1 second increments to control the distribution of the barrier layer within the preform.

If the auxiliary injection unit 102 begins melt injection too early, there will be an uneven distribution of the barrier material as shown by the preform 770a in Figure 7A, in which the position Pa of the barrier material extends beyond from a preform body and into a threaded region where it is not needed. By viewing this scenario, the operator can provide input to controller 150 to begin injection from auxiliary injection unit 102 when sensor 114 detects a higher preset value. Alternatively, the operator may choose to activate the injection delay timer 152 of the controller 150 so that when the sensor 114 reaches the preset value, the timer 152 will delay the injection of the second melt stream by the auxiliary injection unit 102. . On the contrary, if the injection of the auxiliary injection material begins to lag, there will be an uneven distribution in the gate and in the region of the body of the preform as shown in Pb of preform 770b in Figure 7B. In this scenario, the operator can lower the preset value at which the sensor 114 signals the auxiliary injection unit 102 to begin injection. Alternatively, if the timer 152 has been used to delay the injection after reaching the preset value, the operator can then reduce the amount of time elapsed before a signal is sent to start the injection by the auxiliary injection unit 102. . The result of such adjustability is that the operator receives control over the start of the injection by the auxiliary injection unit 102 in relation to the beginning of the injection by the primary injection unit 104, so that the distribution of the material The barrier within the inner and outer layer material can be easily adjusted until a desired preform product is produced as shown in Pc of preform 770c in Figure 7C. Once the preset value, and if used, the time delay is optimized, the distribution of the barrier material within the inner and outer material will generally remain consistent throughout subsequent molding cycles.

Figure 8 represents a graph showing the relationship between a pressure P of the first casting stream of moldable material from the primary injection unit 104 represented by the profile (1) of the injection cycle and a pressure P of the second stream of casting of moldable material from the auxiliary injection unit 102, represented by the profile (2) of the injection cycle, with time T having a preselected injection stage feedback setting as can be provided by the system of Figure 1 in accordance with a simultaneous co-injection embodiment herein. The features and aspects of the other embodiments can be used in accordance with the current embodiment. In this embodiment, the injection of the second moldable material melt stream provided by the auxiliary injection unit 102 varies such that it affects a pressure P thereof in response to a detected condition of the first melt stream that correlates with various stages of the injection cycle of the primary injection unit 104. For example, the injection of the second melt stream can be adjusted when it is detected that the first melt stream has reached one or more than a preselected maximum injection pressure value Pmax, a pressure hold value P, and a value P decompression pressure decompression are reached.

In an embodiment herein, once the injection of the first melt stream from the primary injection unit 104 reaches a preselected pressure value Ps detected by one of the direct sensors 114, 114a, 114b, 114g, 114g ', A signal will be provided to the controller 150 of the auxiliary injection unit 102 to begin injection of the secondary melt stream. A delay of a period Ti of time occurs between the beginning of the injection by the primary injection unit 104 and the beginning of the injection by the auxiliary injection unit 102 which corresponds to the time that the melt pressure P takes in the first stream. casting pressure to reach the preset pressure Ps value. Instead of sending a single signal to the auxiliary injection unit 102 regarding when to begin injection of the second melt stream, as described in some of the previous embodiments, the controller 150 according to this embodiment continuously monitors the detected condition of the first melt stream as provided by one of the sensors 114, 114a, 114b, 114g, 114g 'direct so that the injection cycle of the auxiliary injection unit 102 can be continuously varied or adjusted in real time in response thereto at different stages of the injection cycle of the primary injection unit 104. In the embodiment shown, once the pressure of the first melt stream as shown in the profile (1) of the injection cycle reaches a preselected maximum injection pressure value Pmax, the controller 150 sends a signal to the auxiliary injection unit 102 to adjust the injection in order to reduce the pressure of the second melt stream as represented by the profile (2) of the injection cycle proportionally with respect to that of the first foundry stream. In addition or alternatively, once the direct sensor of the primary injection unit 104 detects that the pressure of the first melt stream is at a preset value of holding pressure or packing Pmaintenance, controller 150 instructs auxiliary injection unit 102 to adjust injection to increase the pressure of the second melt stream to a value greater than that of the first melt stream and maintain that pressure until the unit's direct sensor 104 primary injection detects that the pressure of the first melt stream is reduced to a preselected decompression pressure value P decompression, such as during system decompression, at that point, the controller 150 may again instruct the auxiliary injection unit 102 to adjust the injection to reduce the pressure of the second melt stream accordingly.

ES 2 804 802 T3

One skilled in the art will understand that, in light of the disclosure herein, the injection cycle profiles depicted in Figures 2-5 and 8 are intended to be exemplary and not a limitation as to the injection cycles contemplated by the present invention. Additionally, a person skilled in the art will understand that, in view of the disclosure of this document, the preselected value for the signaling of the beginning of the auxiliary injection unit 5 102 could be measured and correlated at any point of the injection cycle of the injection. primary 104 and not only during the injection pressure increase shown in the injection cycle profile (1) in Figures 2-5 and 8. For example with reference to Figure 2, the pressure P or the velocity V of the primary injection can be measured after reaching the maximum pressure anywhere along the portion of the profile (1) of the injection cycle where pressure and speed are decreasing.

While various embodiments have been described above, it should be understood that they have been presented only as illustrations and examples of the present invention, and not by way of limitation. Although only one auxiliary injection unit is shown, more than one auxiliary injection unit could be used with an injection molding system if the specific molding application requires more than one auxiliary material. Furthermore, it should be noted that although each of the embodiments describes an auxiliary injection unit used in conjunction with a molding machine with a primary injection unit, this is also by way of illustration and not limitation.