WO2014025674A1

WO2014025674A1 - Injection molding apparatus and method for monitoring mold halves movement

Info

Publication number: WO2014025674A1
Application number: PCT/US2013/053591
Authority: WO
Inventors: Lin Yang; Zhuang Rui TAN
Original assignee: Synventive Molding Solutions, Inc.,; Galati, Vito
Priority date: 2012-08-06
Filing date: 2013-08-05
Publication date: 2014-02-13

Abstract

An injection molding apparatus comprised of an injection molding machine, a fluid distribution system that includes a heated manifold, one or more actuators and associated valve pins controlling flow through one or more gates leading to a cavity formed by first and second mold members, a magnet mounted to one of the first and second mold members, a sensor mounted to the other of the first and second mold members, the degree or quality of the magnetic field sensed by the sensor varying with position of the mold members relative to each other, the sensor generating signals indicative of the position of the mold members relative to each other based on a sensed variation in the magnetic field generated by the magnet, and, a controller adapted to receive and store one or more signals generated by the sensor.

Description

INJECTION MOLDING APPARATUS AND METHOD

FOR MONITORING MOLD HALVES MOVEMENT

RELATED APPLICATIONS

[001 ] This application claims the benefit of priority to U.S. Provisional Application Serial No. 61/680,041 filed August 6, 2012.

[002] The disclosures of all of the following are incorporated by reference in their entirety as if fully set forth herein: U.S. Patent No. 5,894,025, U.S. Patent No. 6,062,840, U.S.

Patent No. 6,294,122, U.S. Patent No. 6,309,208, U.S. Patent No. 6,287,107, U.S. Patent No. 6,343,921 , U.S. Patent No. 6,343,922, U.S. Patent No. 6,254,377, U.S. Patent No.

6,261 ,075, U.S. Patent No. 6,361 ,300 (7006), U.S. Patent No. 6,419,870, U.S. Patent No. 6,464,909 (7031), U.S. Patent No. 6,599,116, U.S. Patent No. 6,824,379, U.S. Patent No. 7,234,929 (7075US1 ), U.S. Patent No. 7,419,625 (7075US2), U.S. Patent No. 7,569,169 (7075US3), U.S. Patent Application Serial No. 10/214,1 18, filed August 8, 2002 (7006), U.S. Patent No. 7,029,268 (7077US1 ), U.S. Patent No. 7,270,537 (7077US2), U.S. Patent No. 7,597,828 (7077US3), U.S. Patent Application Serial No. 09/699,856 filed October 30, 2000 (7056), U.S. Patent No. 6,005,013, U.S. Patent No. 6,051 ,174, U.S. Patent application publication no. 20020147244, U.S. Patent Application Serial No. 10/269,927 filed October 11 , 2002 (7031 ), U.S. Application Serial No. 09/503,832 filed February, 15, 2000 (7053), U.S. Application Serial No. 09/656,846 filed September 7, 2000 (7060), U.S. Application Serial No. 10/006,504 filed December 3, 2001 , (7068) and U.S. Application Serial No.

10/101 ,278 filed March, 19, 2002 (7070) and U.S. Application Serial No. 13/484,336 filed May 31 , 2012 (7100US1 ) and U.S. Application Serial No. 13/484,408 filed May 31 , 2012 (7100US3).

BACKGROUND OF THE INVENTION

[003] Systems for counting the number of times that two mold halves open and close have been developed using mechanical devices interconnected by hard wires to detect and count the occurrence of mold halves engaging and disengaging from each other such as shown in U.S. Patent No. 7,311 ,136. SUMMARY OF THE INVENTION

[004] In accordance with the invention there is provided an injection molding apparatus comprising an injection molding machine, a fluid distribution system that includes a heated manifold, one or more actuators that control movement of one or more associated valve pins to control flow of fluid through one or more gates that lead to a cavity formed by first and second mold members,

one or the other or both of the first and second mold members being controllably movable to a plurality of positions of variable distances relative to each other including a closed position and an open position,

the apparatus further comprising:

a magnet mounted to one of the first and second mold members, the magnet generating a magnetic field,

a sensor mounted to the other of the first and second mold members such that the sensor can sense a degree or quality in the magnetic field generated by the magnet,

the degree or quality of the magnetic field sensed by the sensor varying with position of the mold members relative to each other,

the sensor generating signals indicative of the position of the mold members relative to each other based on a sensed variation in the magnetic field generated by the magnet, and,

a controller adapted to receive and store one or more signals generated by the sensor,

the controller including instructions that determine the position of the mold members relative to each other based on the received signals and memory that stores data indicative of the position of the mold members as determined by the instructions.

[005] The controller typically includes a counter, the counter being adapted to at least record signals received from the sensor that are indicative of the mold members being disposed in the open and closed positions and the times when the mold members are disposed in the open and closed positions.

[006] The controller can includes an algorithm that instructs one or more of the actuators to control movement of the valve pins based on the received signals. [007] The first mold member is preferably mounted on the machine in an assembly that includes the fluid distribution system, the magnet being mounted to the first mold member, the assembly being stationarily mounted to the machine.

[008] The second mold member is preferably mounted on the machine for slidable back and forth movement relative to the first mold member, the sensor being mounted to the second mold member.

[009] The sensor is typically housed in or mounted to a housing having a wall disposed between the sensor and the magnet, the wall comprising a non-magnetic or magnetically permeable material.

[010] The counter preferably counts and records occurrences of the first and second mold members movement between the open and closed positions including time and number of said occurrences, the controller including an algorithm that instructs one or more of the actuators to move their associated valve pins to positions during the course of an injection that depends on the counted and recorded occurrences of the mold members movement.

[011] Most preferably the counter counts and records occurrences of the first and second mold members movement between the open and closed positions including time and number of said occurrences, the controller including an algorithm that correlates said counted and recorded occurrences to a set of data representing quality of one or more parts produced in an injection cycle between said occurrences of movement.

[012] In another aspect of the invention there is provided in an injection molding apparatus comprising an injection molding machine, a fluid distribution system that includes a heated manifold, one or more actuators that control movement of one or more associated valve pins to control flow of fluid through one or more gates that lead to a cavity formed by first and second mold members,

a method of producing a part in the mold members comprising:

mounting a magnet to one of the first and second mold members, the magnet generating a magnetic field, mounting a sensor to the other of the first and second mold members wherein the sensor can sense a degree or quality in the magnetic field generated by the magnet,

receiving and storing one or more signals generated by the sensor,

determining the position of the mold members relative to each other based on the received signals and,

storing data indicative of the determined position of the mold members.

Such a method typically further comprises:

recording signals received from the sensor that are indicative of the mold members being disposed in the open and closed positions and the times when the mold members are disposed in the open and closed positions, and,

counting and storing the recorded signals.

[013] Such a method can further comprise instructing one or more of the actuators to control movement of the valve pins based on the received signals.

[014] Such a method can further comprise mounting the first mold member on the machine in an assembly that includes the fluid distribution system, the magnet being mounted to the first mold member, the assembly being stationarily mounted to the machine. Such a method can further comprise mounting the second mold member on the machine for slidable back and forth movement relative to the first mold member, the sensor being mounted to the second mold member.

Brief Description of the Drawings

[015] The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings in which: [016] Fig. 1 is a side sectional view of an injection molding apparatus according to the invention showing a Hall Effect sensor mounted to a cold half of a mold assembly and a magnet mounted to a hot half of the mold assembly.

[017] Fig. 2 is a cross-sectional detailed view of one of the nozzle stacks of the Fig. 1 apparatus.

[018] Fig. 3A is a schematic block diagram of one embodiment of a hall effect circuit including a hall effect sensor for detecting the magnetic field, and additional circuit components for amplifying the signal and converting the signal to an output current signal.

[019] Fig. 3B is a schematic diagram of one embodiment of a hall effect sensor circuit.

[020] Fig. 4 is a schematic diagram of the magnetic field lines generated by an ideal cylindrical magnetic member.

[021 ] Figs. 5A-5F are schematic illustrations of a magnetic member mounted on one half of a mold being moved relative to a hall effect sensor (HES) mounted in field detection proximity on another half of the mold, the magnet being arranged in various orientations, wherein the flux density changes as the position of the magnetic member changes.

DETAILED DESCRIPTION

[022] FIG. 1 shows one embodiment of the injection molding system according to the present invention having mold halves 25, 27 mounted as shown. The present invention can be implemented in many other embodiments and arrangements having a pair of mold halves mounted to an injection molding machine, the embodiment described herein being described for ease and clarity of description.

[023] The injection molding system 1 shown in Fig. 1 is a multi-gate single cavity system in which melt material 3 is injected into a cavity 5 from gates 7and 9. Melt material 3 is injected from an injection molding machine 11 through an extended inlet 13 and into a manifold 15. Manifold 15 distributes the melt through channels 17 and 19. Although a hot runner system is shown in which plastic melt is injected, the invention is applicable to other types of injection systems in which it is useful to control the rate at which a material (e.g., metallic or composite materials) is delivered to a cavity.

[024] Melt is distributed by the manifold through channels 17 and 19 and into bores 18 and 20 of nozzles 21 and 23, respectively. Melt is injected out of nozzles 21 and 23 and into cavity 5 (where the part is formed) which is formed by mold plates 25 and 27. Although a multi-gate single-cavity system is shown, the invention is not limited to this type of system, and is also applicable to, for example, multi-cavity systems, as discussed in greater detail below.

[025] The injection nozzles 21 and 23 are received in respective wells 28 and 29 formed in the mold plate 27. The nozzles 21 and 23 are each seated in support rings 31 and 33. The support rings serve to align the nozzles with the gates 7 and 9 and insulate the nozzles from the mold. The manifold 15 sits atop the rear end of the nozzles and maintains sealing contact with the nozzles via compression forces exerted on the assembly by clamps (not shown) of the injection molding machine. An O-ring 36 is provided to prevent melt leakage between the nozzles and the manifold. A dowel 73 centers the manifold on the mold plate 27. Dowels 32 and 34 prevent the nozzle 23 and support ring 33, respectively, from rotating with respect to the mold27.

[026] The nozzles also include a heater 35 (FIG.2). Although an electric band heater is shown, other heaters may be used. Furthermore, heat pipes (for example those disclosed in U.S. Pat. No. 4,389,002) may be disposed in each nozzle and used alone or in conjunction with heater 35. The heater is used to maintain the melt material at its processing

temperature up to the gates 7 and 9. The nozzles 21 and 23 also include an insert 37and a tip 39. The insert can be made of a material (for example beryllium copper) having high thermal conductivity in order to maintain the melt at its processing temperature up to the gate by imparting heat to the melt from the heater 35. The tip 39 is used to form a seal with the mold plate 27 and is preferably a material (for example titanium alloy or stainless steel) having low thermal conductivity so as to reduce heat transfer from the nozzle to the mold.

[027] A valve pin 41 having a head 43 is used to control the rate of flow of the melt material to the respective gates 7 and 9. The valve pin reciprocates through the manifold. A valve pin bushing 44 is provided to prevent melt from leaking along stem 102 of the valve pin. The valve pin bushing is held in place by a threadably mounted cap 46. The valve pin is opened at the beginning of the injection cycle and closed at the end of the cycle. During the cycle, the valve pin can assume intermediate positions between the fully open and closed positions, in order to decrease or increase the rate of flow of the melt. The head includes a tapered portion 45 that forms a gap 81 with a surface 47 of the bore 19 of the manifold. Increasing or decreasing the size of the gap by displacing the valve pin correspondingly increases or decreases the flow of melt material to the gate. When the valve pin is closed the tapered portion 45 of the valve pin head contacts and seals with the surface 47 of the bore of the manifold.

[028] FIG. 2 shows the head of the valve pin in a phantom dashed line in the closed position and a solid line in the fully opened position in which the melt is permitted to flow at a maximum rate. To reduce the flow of melt, the pin is retracted away from the gate by an actuator 49, to thereby decrease the width of the gap 81 between the valve pin and the bore 19 of the manifold.

[029] The actuator 49 (for example, the type disclosed in application Ser. No. 08/874,962) is mounted in a clamp plate 51 which covers the injection molding system 1. The actuator 49 is a hydraulic actuator, however, pneumatic or electronic actuators can be used. The actuator 49 includes a hydraulic circuit that includes a movable piston53in which the valve pin41 is threadably mounted at 55. Thus, as the piston 53 moves, the valve pin 41 moves with it. The actuator 49 includes hydraulic lines 57 and 59 which are controlled by servo valves 1 and 2. Hydraulic line 57 is energized to move the valve pin 41 toward the gate to the open position, and hydraulic line 59 is energized to retract the valve pin away from the gate toward the close position. An actuator cap 61 limits longitudinal movement in the vertical direction of the piston 53. O-rings 63 provide respective seals to prevent hydraulic fluid from leaking out of the actuator. The actuator body 65 is mounted to the manifold via screws 67.

[030] In some embodiments, a pressure transducer 69 can used to sense the pressure in the manifold bore 19 downstream of the valve pin head 43. In one embodiment where electronic control of the movement of the valve pins is desired, the conditions sensed by the pressure transducer 69 associated with each nozzle are fed back to a control system that includes controllers PID 1 and PID 2 and a CPU shown schematically in FIG.1. The CPU executes a PID (proportional, integral, derivative) algorithm which compares the sensed pressure (at a given time) from the pressure transducer to a programmed target pressure (for the given time). The CPU instructs the PID controller to adjust the valve pin using the actuator 49 in order to mirror the target pressure for that given time. In this way a programmed target pressure profile for an injection cycle for a particular part for each gate 7 and 9 can be followed.

[031] Although in the disclosed embodiment the sensed condition is pressure, other sensed conditions can be used which relate to melt flow rate. For example, the position of the valve pin or the load on the valve pin could be the sensed condition. If so, a position sensor or load sensor, respectively, could be used to feed back the sensed condition to the PID controller. In the same manner as explained above, the CPU would use a PID algorithm to compare the sensed condition to a programmed target position profile or load profile for the particular gate to the mold cavity, and adjust the valve pin accordingly.

[032] In the Fig. 1 embodiment a mold comprising first and second halves 25, 27 is shown, the mold halves 25, 27 forming a cavity 5 for forming a finished part when the mold halves 25, 27 are in a closed position as shown in Fig. 1. The apparatus comprises a fluid distribution or hotrunner system comprised of a hot half 1600. What is sometimes referred to as a cold half 1500, is mounted to a stationary platen (not shown) of the injection molding machine 1700 for controllable movement of the movable half 25 into and out of mold closed and mold open positions relative to mold half 27. Fig. 1 shows the mold halves 25, 27 in a closed position.

[033] As shown in Fig. 1 , a magnet 42 is preferably mounted to the mold half 27 associated with the hot half 1600 of the apparatus. The hot half comprises components 27, 51 , 15 and all of their associated components as shown in Fig. 1 , such components typically being assembled together as a subassembly, the manifold component 15 being heated to very highly elevated temperatures for purposes of maintaining the fluid in a molten state while travelling through the distribution channels of the manifold and the nozzles 21 , 23. The hot half 1600 is typically mounted in a stationary manner to and on a stationary platen of the injection molding machine 1700, the tip end of the barrel 11 of which is shown in Fig. 1. Alternatively, the magnet 42 can be mounted on the mold half 25.

[034] As shown in Fig. 1 , a Hall Effect sensor 52 is preferably mounted to the mold half 25 that is associated with the cold half 1500 of the system. The cold half 1500 of the mold is typically mounted to a movable platen 1300 of the machine 1700 such that the cold half 1500 including the mold half 25 is controllably movable back and forth 1600 along a predetermined path 1600 relative to the stationarily mounted first half 27 of the mold. Alternatively the sensor 52 can be mounted on the mold half 27 with the magnet 42 being mounted to the mold 25.

[035] The magnet and the Hall Effect sensor 52 are mounted on or to the mold halves 25, 27 in spatial positions that are selected so that the sensor 52 can sense and detect the strength and quality of the magnetic field generated by the magnet at all open and closed positions along the back and forth 1600 path of travel that the mold half 25 is normally enabled to travel by operation of the movable platen of the machine 1300. The mold halves are spatially separated from each other and the cavity 5 is typically opened when the mold halves 25, 27 are moved from the closed position shown in Fig. 1 to any position along the normal sliding or movable machine platen 1300 path of travel 1610 away from each other. The Hall Effect sensor 52 can detect the strength, degree or quality of the magnetic field generated by the magnet 42. The strength, degree or quality of the magnetic field generated the magnetic that is detected by the sensor 52 varies depending on the precise spatial positioning the magnet 42 relative to the sensor 52. Therefore when the mold halves 25, 27 spatially move in position relative to each other, the sensor 52 detects a magnetic field having a strength, degree or quality that is peculiar to the precise position of the magnet 42 relative to the sensor 52. Such variation in the detected strength, degree or quality of the magnetic field generated by the magnet 42 can thus be correlated or calibrated to correspond to the spatial positions of the mold halves 25, 27 relative to each other. Thus, the Hall Effect sensor 52 is used as a wireless sensor of and for the relative positions of the mold halves 25, 27 and, a fortiori, can be used to detect when the mold halves are closed or open.

[036] When the mold halves are closed the magnet 42 and the sensor 52 are spaced a distance D1 away from each other. When the mold halves are opened, the magnet 42 and sensor 52 are spaced a distance D2 away from each other. When the mold halves are closed, the magnet 42 and the field generated by the magnet are disposed in one alignment relative to the sensor 52 and spaced apart a distance D1 . When the mold halves are opened such that the magnet and sensor are spaced D2 apart, the magnetic field lines (see Fig. 4) from the magnet 42 to the sensor 52 changes the flux density that the sensor detects. Such movement of the mold halves thus changes the flux density measured by the sensor 52 outputing a voltage signal which is indicative of the position of the mold halves relative to each other such as open versus closed. The sensor voltage output can then be processed, e.g., amplified and/or converted to a current signal, and used in selected algorithms as data indicative of the number of times the mold halves are opened and closed whereby such data can be further processed by the controller 70 to control the actuators and the valve pins.

[037] The Hall Effect sensor 52 is typically housed or mounted within a housing (not shown) comprised of metal walls, the metal walls of the housing physically and spatially separating and being disposed between the electronic magnetic field sensor 52 and the magnet 42 as well as the magnetic field generated by the magnet 42. Where the Hall Effect sensor 52 is housed within a metal housing or otherwise separated from the magnet by a metal wall, the material of which the metal housing or walls is comprised are non-magnetic or are permeable to magnetic fields such that the sensor 52 is capable of sensing and detecting the magnetic field generated by the magnet 42.

[038] The Hall Effect sensor 52 and magnet 42 preferably function and are comprised in structure, components and electronic arrangement in a conventional manner. The sensor 52 can be but is not necessarily housed in a housing having metal walls. A magnetic member, here a permanent magnet 42, is mounted on one of a pair of mold halves, preferably the hot half 1600. As shown in Fig. 1 , the sensor 52 is mounted on one of a pair of mold halves, preferably the cold half 1500. The sensor 52 may be part of a hall effect circuit 56 mounted on the exterior surface of the mold half. The circuit has input/output channels for transmitting a power input signal 58 from the controller or CPU 70, and a hall output signal 60 sent to the controller 70. As shown in Fig. 3A, the hall effect circuit 56 includes a power regulator component 62 that receives power input signal 58. The regulator adjusts the power level as necessary and sends a power signal on channel 63 to the hall effect sensor 52. The output of the hall effect sensor is a hall voltage which is transmitted on channel 64 to a signal amplifier component 65. The amplified output signal is then sent on channel 66 to a current conversion and signal driver component 67 which converts the hall voltage to a hall current and outputs the hall current 60 to the control system 70. The communication channels between the various electronic components in the hall effect circuit and other between/among other components of the disclosed embodiment, can be any known communication media, including wired or wireless media. [039] As shown in Fig. 4, an ideal cylindrical magnet generates an ideal field having an axis of symmetry inside the image plane. The magnetic field at any given point is specified by both direction and magnitude (or strength), and thus comprises a vector field. A higher density of nearby field lines indicates a stronger magnetic field. The magnetic field points towards a magnet's south pole S and away from its north pole N. Permanent magnets are objects that produce their own persistent magnetic fields. They are made of ferromagnetic materials, such as iron and nickel, that have been magnetized, and they have both a north pole and a south pole.

[040] Figs. 5A-5F show six different examples of alternative orientations of a hall effect sensor (HES) 52 with respect to a magnet 42. The magnet 42 can be moved relative to the hall effect sensor 52 in various orientations, as long as the flux density changes as the magnet position changes. The orientation of the magnet 42 relative to the sensor 52 that is selected for a particular application would take into account the physical space, ease of output usage, and sensitivity to change desired for a particular application. In Figs. 5A-5C, the north-south axis of the magnet is transverse to the direction of movement D3 of the magnet, the latter being aligned with the axis A of the bore 14 of the actuator housing. The sensor can be disposed adjacent either end of the magnet 42, near the north pole or south pole. In contrast, on the right hand side of Figs. 5D-5F, the north-south axis of the magnet is aligned parallel with the direction D4 of movement of the magnet. Here, the hall effect sensor 52 can be mounted either at one end of the one or more magnets, offset from one end of the magnets, and/or the magnets can be disposed with either pole closer to the sensor. These and other orientations will be apparent to the skilled person.

Signals generated by the sensor 52 in response to detection of the magnetic field generated by the magnet 42 can be used in a program contained within controller or CPU 70 to perform a variety of monitoring or control functions. One function or algorithm included within CPU 70 can be a program or algorithm that counts and records the occurrence and times of occurrences of the open and closed positions of mold halves 25, 27. Such detected and recorded data can be then be correlated via a program contained in CPU 70 to the times when specific injection cycles occurred and in turn correlated to specific physical parts that are or were produced in the mold cavity 5 during the times when the mold halves were in a closed position and parts were being produced in closed cavity 5. See appendix C regarding additional controller functionalities that work in conjunction with mold halves 25, 27.

Claims

Claims:

1. An injection molding apparatus comprising an injection molding machine, a fluid distribution system that includes a heated manifold, one or more actuators that control movement of one or more associated valve pins to control flow of fluid through one or more gates that lead to a cavity formed by first and second mold members,

the apparatus further comprising:

2. The apparatus of claim 1 wherein the controller includes a counter, the counter being adapted to at least record signals received from the sensor that are indicative of the mold members being disposed in the open and closed positions and the times when the mold members are disposed in the open and closed positions.

3. The apparatus of claim 1 wherein the controller includes an algorithm that instructs one or more of the actuators to control movement of the valve pins based on the received signals.

4. The apparatus of claim 1 wherein the first mold member is mounted on the machine in an assembly that includes the fluid distribution system, the magnet being mounted to the first mold member, the assembly being stationarily mounted to the machine.

5. The apparatus of claim 4 wherein the second mold member is mounted on the machine for slidable back and forth movement relative to the first mold member, the sensor being mounted to the second mold member.

6. The apparatus of claim 1 wherein the sensor is housed in or mounted to a housing having a wall disposed between the sensor and the magnet, the wall comprising a non-magnetic or magnetically permeable material.

7. The apparatus of claim 2 wherein the counter counts and records occurrences of the first and second mold members movement between the open and closed positions including time and number of said occurrences, the controller including an algorithm that instructs one or more of the actuators to move their associated valve pins to positions during the course of an injection that depends on the counted and recorded occurrences of the mold members movement.

8. The apparatus of claim 2 wherein the counter counts and records occurrences of the first and second mold members movement between the open and closed positions including time and number of said occurrences, the controller including an algorithm that correlates said counted and recorded occurrences to a set of data representing quality of one or more parts produced in an injection cycle between said occurrences of movement.

9. In an injection molding apparatus comprising an injection molding machine, a fluid distribution system that includes a heated manifold, one or more actuators that control movement of one or more associated valve pins to control flow of fluid through one or more gates that lead to a cavity formed by first and second mold members,

a method of producing a part in the mold members comprising:

receiving and storing one or more signals generated by the sensor,

storing data indicative of the determined position of the mold members.

10. The method of claim 9 further comprising:

counting and storing the recorded signals.

11. The method of claim 9 further comprising instructing one or more of the actuators to control movement of the valve pins based on the received signals.

12. The method of claim 9 further comprising mounting the first mold member on the machine in an assembly that includes the fluid distribution system, the magnet being mounted to the first mold member, the assembly being stationarily mounted to the machine. The method of claim 12 further comprising mounting the second mold member on the machine for slidable back and forth movement relative to the first mold member, the sensor being mounted to the second mold member.