Method for determining misalignment of a tip in a sleeve of a molten metal injection device in a die casting system

Abstract

To confirm an off-centered state of a tip 20 with respect to a sleeve 10 of an injection device for molten metal in a die 2 of a die casting system 1.SOLUTION: A method of confirming a misalignment state of a tip supported by a rod 21 and reciprocating inside a sleeve communicating with a cavity of an injection device for injecting molten metal into a cavity 2a of a die for molding a casting by injecting the molten metal Lm in a die casting system includes a process of acquiring detection values of acceleration sensors 30a, 30b, 30c provided in the injection device while the tip moves inside the sleeve, a process of calculating an index value indicating variation of the detection values of the acceleration sensors acquired while the tip moves inside the sleeve, and a process of determining misalignment of the center of the tip with respect to the center of the sleeve based on the index value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a die-casting system, and more particularly to a method for checking the misalignment of a tip relative to a sleeve of an injection device that injects molten metal into a cavity of a mold in a die-casting system. [Background technology]

[0002] In a die-casting system for casting complex-shaped metal (e.g., aluminum) molded products, an injection device injects molten metal into a cavity defined by a mold. The injection device includes a cylindrical sleeve connected to the cavity and a cylindrical tip (plunger) supported by a rod within the sleeve and reciprocating within the sleeve. During the casting process, the tip retracts away from the cavity, drawing the molten metal into the sleeve, and then advances toward the cavity to extrude (inject) the molten metal into the cavity. This cycle is repeated. Regarding this injection device, Patent Document 1 proposes attaching an acceleration sensor to the sleeve, tip, or rod, and detecting "galling" of the tip against the sleeve from the vibration waveform detected by the acceleration sensor. Here, "galling" refers to wear that occurs between the tip and the sleeve. When molten metal enters the worn area and solidifies, a mass of metal is trapped between the tip and the sleeve, causing vibrations when the tip advances or retreats. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2020-138209 Summary of the Invention [Problem to be solved by the invention]

[0004] In the injection device for the molten metal of the die of the die casting system described above, it is preferable that the tip reciprocates smoothly within the sleeve with as little sliding resistance as possible. To achieve this, it is preferable that the center of the cylindrical tip is as closely aligned as possible with the center of the cylindrical sleeve, i.e., be centered. Therefore, it is advantageous to be able to constantly check the tip's misalignment (the degree of misalignment of the tip from the center of the sleeve). In this regard, the inventors of the present invention have found that the greater the misalignment of the tip, the greater the variation in the detection values ​​detected by an acceleration sensor attached to the sleeve, tip, or rod during tip movement. This is thought to be because as the tip misalignment increases, the surface pressure between the tip and the sleeve changes, causing a change in sliding resistance during tip movement. In other words, by referring to any index value representing the variation in the detection values ​​of the acceleration sensor during tip movement, the misalignment of the tip can be confirmed. This finding is utilized in the present invention.

[0005] SUMMARY OF THE INVENTION Accordingly, a primary object of the present invention is to provide a novel method capable of checking the misalignment of a tip relative to a sleeve of an injection device for molten metal in a die of a die casting system. [Means for solving the problem]

[0006] According to one aspect of the present invention, the above-mentioned problem is solved by a method for checking the misalignment state of a tip supported by a rod inside a sleeve communicating with a cavity of an injection device that injects molten metal into a cavity of a mold into which the molten metal is poured to form a casting, the method comprising: acquiring a detection value of an acceleration sensor provided in the injection device while the tip moves within the sleeve; calculating an index value representing a variation in the detection values ​​of the acceleration sensor acquired while the tip moves within the sleeve; determining a deviation of the center of the tip relative to the center of the sleeve based on the index value; This is achieved by a method comprising:

[0007] In the above configuration, the "die-casting system" may be a casting system that forms a casting by a conventional die-casting method. A cavity into which molten metal is poured to form a casting is defined by a mold. The molten metal is poured (injected) into the cavity by an injection device that includes a typically cylindrical sleeve connected to the cavity and a tip (plunger) that is supported by a rod and reciprocates inside the sleeve and has a shape complementary to the shape of the inside of the sleeve. The tip retracts within the sleeve away from the cavity to draw the molten metal into the sleeve, and then advances toward the cavity to push the molten metal into the cavity. In this system, castings are typically mass-produced by repeating a cycle of injecting the molten metal into the cavity, forming a mold (hardening the molten metal), removing the molded product, and forming a cavity. The injection of the molten metal into the sleeve is achieved through an injection port that opens on the upper surface of the sleeve with the tip retracted within the sleeve in a direction away from the cavity. When the tip moves forward from its retracted position within the sleeve to extrude the molten metal into the cavity, the tip typically accelerates from a stopped state to an appropriately set constant speed, moves at that constant speed, and then accelerates again just before the extrusion is completed, after which it is stopped.

[0008] The acceleration sensor provided in the injection device may be any acceleration sensor capable of detecting vibrations during tip movement. The acceleration sensor may be provided on at least one of the tip, rod, and sleeve, preferably on the tip or rod, and more preferably on the tip or rod and sleeve. The acceleration sensor may be arranged to detect at least one of vibrations in the up-down (vertical), lateral, and travel direction of the tip, preferably on the up-down vibration, more preferably on the up-down and lateral vibrations, and even more preferably on the up-down, lateral, and travel direction vibrations. The degree of tip misalignment in the up-down direction is reflected in the up-down vibration, and the degree of lateral misalignment is reflected in the lateral vibration. Furthermore, the up-down and lateral misalignment of the tip are also reflected in the travel direction vibration.

[0009] The detection of vibrations by the acceleration sensor may be performed continuously during the molding process, and the index value representing the variation in the detected values ​​of the acceleration sensor may be calculated using the detected values ​​acquired while the tip is moving, particularly while moving at a constant speed. The index value representing the variation in the detected values ​​may be any statistical value representing the variation in the detected values, and may be appropriately selected from the standard deviation, variance, root mean square, maximum amplitude, and average amplitude of the amplitude.

[0010] In the method of the present invention, the sliding resistance between the tip and the sleeve changes depending on the misalignment of the tip during its movement, and as a result, an index value representing the variation in the detected values ​​of the acceleration sensor provided in the injection device, i.e., the degree of vibration of the tip, is determined based on this index value. With this configuration, it is possible to check the misalignment of the tip center with the center of the sleeve when moving the tip into the sleeve before the casting process or during the casting process, and depending on the state, it is possible to perform centering to align the tip center with the center of the sleeve at an appropriate time.

[0011] In the above configuration, the greater the deviation of the center of the tip from the center of the sleeve, the greater the vibration of the tip during movement, so in one embodiment, the greater the variation represented by the index value, the greater the deviation of the center of the tip from the center of the sleeve, which makes it possible to grasp the degree of tip misalignment.

[0012] In another embodiment, when the variation in the detected index value reaches a predetermined threshold, it may be determined that the center of the tip is misaligned with the center of the sleeve to such an extent that centering of the tip within the sleeve is necessary. This makes it easy to determine whether or not the tip needs to be realigned. The predetermined threshold can be determined by experiment, etc.

[0013] In the above configuration, as already described, the degree of misalignment of the chip in the up-down direction is reflected in the up-down vibration, the degree of misalignment in the lateral direction is reflected in the lateral vibration, and the misalignment in the up-down and lateral directions of the chip is also reflected in the vibration in the direction of travel. Therefore, the larger the index value of the chip in the up-down direction, the larger the misalignment in the up-down direction of the chip; the larger the index value of the chip in the lateral direction, the larger the misalignment in the lateral direction of the chip; and the larger the index value of the chip in the direction of travel of the chip, the larger the misalignment in the up-down or lateral direction of the chip. Similarly, if the index value of the chip in the up-down direction exceeds a predetermined threshold, it may be determined that readjustment of the chip's centering in the up-down direction is necessary; if the index value of the chip in the lateral direction exceeds a predetermined threshold, it may be determined that readjustment of the chip's centering in the lateral direction is necessary; and if the index value of the chip in the direction of travel exceeds a predetermined threshold, it may be determined that readjustment of the chip's centering in the up-down direction, the lateral direction, or both. [Effects of the Invention]

[0014] Thus, according to the present invention, it is possible to timely check the misalignment of the tip relative to the sleeve of the molten metal injection device of the mold of a die-casting system. Misalignment of the injection device tip has a significant impact on the smooth operation of the tip and the life of the operating parts, and as a result, has a significant impact on the quality of the molded product. However, according to the present invention, it is possible to check the misalignment of the tip relative to the sleeve, and it is also easy to determine whether centering readjustment is necessary, which is expected to improve the efficiency of molding work and the quality of molded products.

[0015] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief explanation of the drawings]

[0016] [Figure 1] 1(A) to (C) are schematic diagrams of the process of injecting molten metal into a die cavity in a die casting system. (A) shows the process of injecting molten metal into a sleeve, (B) shows the state where the tip advances inside the sleeve and begins to extrude the molten metal, and (C) shows the state where the molten metal inside the sleeve has finished being ejected. [Figure 2] FIG. 2 is a schematic diagram of an injection device of a mold in the die casting system according to this embodiment. [Figure 3] 3A and 3B are diagrams each showing a schematic representation of the forward movement speed V of a tip in a sleeve of an injection device of a mold in a die casting system according to this embodiment, and the change over time in the detected value A of an acceleration sensor. [Figure 4] FIG. 4 is a flowchart showing the process of centering the tip in the sleeve of the injection unit of the mold in the die casting system according to this embodiment. [Explanation of symbols]

[0017] 1... Die-casting system, 2... Mold, 2a... Cavity (mold), 10... Sleeve (injection device), 11... Molten metal inlet, 20... Tip (injection device), 21... Rod (injection device), 30a, 30b, 30c... Acceleration sensor, 50... Calculation device (computer device), Lm... Molten metal BEST MODE FOR CARRYING OUT THE INVENTION

[0018] Die-casting system configuration The method of this embodiment is applied to checking the misalignment state of the tip 20 in the sleeve 10 in the injection device of the mold 2 of a conventional die-casting system 1 as shown in Fig. 1. Briefly stated, when injecting molten metal Lm into the cavity 2a of the mold 2 in the die-casting system 1, first, as shown in Fig. 1(A), the tip 20 supported by the rod 21 in the sleeve 10 communicating with the closed cavity 2a is in a retracted position away from the cavity 2a, and the molten metal Lm is poured into the sleeve 10 in any manner through the melt pouring port 11. Next, as shown in Figs. 1(B) and 1(C), the rod 21 in the sleeve 10 is driven by an actuator (not shown), moving the tip 20 in a direction approaching the cavity 2a, thereby pushing the molten metal Lm from the sleeve 10 into the cavity 2a. Thereafter, the molten metal Lm is hardened in the cavity 2a, the cavity 2a is opened, the hardened and molded casting is removed from the molten metal Lm (demolding), the cavity 2a is closed again, and the next molding cycle is carried out.

[0019] In the above-described mold injection device, the tip 20 reciprocates powerfully within the sleeve 10 at a relatively high speed, so it is desirable for the sliding resistance to be as small as possible and for the tip 20 to move smoothly. To achieve this, it is preferable that the center of the sleeve 10 and the center of the tip 20 coincide as closely as possible in a plane perpendicular to the direction of tip 20 movement. If the deviation (misalignment) of the center of the tip 20 from the center of the sleeve 10 becomes large to a certain extent, the sliding resistance during tip 20 movement increases, which may affect the life of operating parts such as the actuators that drive the tip 20, sleeve 10, and rod 21, or may even affect the quality of the molded product. In relation to this point, research by the inventors of the present invention has found that the deviation of the center of the tip 20 from the center of the sleeve 10 affects the variation in the detected value (i.e., vibration amplitude) detected by acceleration sensors installed on the tip 20, sleeve 10, rod 21, etc. during the tip 20's movement within the sleeve 10. More specifically, it was found that the greater the deviation of the center of the tip 20 from the center of the sleeve 10, the greater the variation in the amplitude of vibration detected by the acceleration sensor. Therefore, in this embodiment, as will be described in detail below, the vibration (acceleration) of the tip 20 while it is moving within the sleeve 10 is successively detected by the acceleration sensor, an index value representing the degree of variation in the detected values ​​is calculated, and the degree of misalignment of the tip 20 is determined based on the index value.

[0020] Vibration detection configuration using an acceleration sensor As shown in FIG. 2 , when performing the method for checking the misalignment state of the tip 20 according to this embodiment, at least one acceleration sensor 30a, 30b, or 30c is installed at any location of the injection device, which is composed of the sleeve 10, tip 20, and rod 21. The acceleration sensor may be installed on one or two of the sleeve 10, tip 20, or rod 21, or on all of them. The acceleration sensors may be installed to detect the acceleration of the tip in the up-down direction u-d, the lateral direction LR, and the front-back direction (movement direction) fb. In this regard, the acceleration in the up-down direction u-d strongly reflects the degree of misalignment of the tip 20 in the up-down direction u-d. The acceleration in the lateral direction LR strongly reflects the degree of misalignment of the tip 20 in the lateral direction LR. The acceleration in the front-back direction fb reflects the degree of misalignment of the tip 20 in the up-down direction u-d and the lateral direction LR. Therefore, the detection direction of the acceleration to be detected may be selected depending on the direction of misalignment to be detected, and preferably, acceleration sensors may be installed corresponding to each direction so that acceleration in all directions can be detected.

[0021] The detection values ​​of the acceleration sensors 30a, 30b, and 30c are transmitted in any manner to the calculation device 50, which may be a computer device, and an index value representing the degree of variation in the detection values ​​of the acceleration sensors is calculated in the calculation device 50, as described above. In this regard, the calculation of the index value typically uses detection values ​​acquired while the tip 20 advances toward the cavity 2a at a constant speed within the sleeve 10. More specifically, when the tip 20 moves within the sleeve 10 from a retracted position (FIG. 1A) away from the cavity 2a to an end position (FIG. 1C) approaching the cavity 2a, as shown in FIG. 3A, the tip 20 accelerates from a stopped state to a certain speed (section a), continues to advance while maintaining that speed (section b), and further accelerates as it approaches the end position (section c) before stopping. 3(B), the detection value A of the acceleration sensor fluctuates greatly in sections a and c, but the fluctuation becomes steady in section b where the chip 20 moves at a constant speed. In this case, the index value representing the degree of variation in the detection value in section b varies depending on the misalignment state of the chip 20, so in the method of this embodiment, the detection values ​​of the acceleration sensor detected in section b where the chip 20 moves at a constant speed are collected, and an index value representing the degree of variation may be calculated.

[0022] The index value representing the degree of variation in the detection values ​​of the acceleration sensors may be any such value, and preferably may be any of the standard deviation, variance, maximum amplitude, root mean square value, and amplitude mean value of the detection values ​​in section b. When acceleration sensors are installed at multiple locations and in multiple directions, an index value representing the degree of variation in the detection values ​​of each acceleration sensor may be calculated.

[0023] The evaluation of the misalignment state of the tip 20 based on the index value representing the degree of variation in the detected values ​​of the acceleration sensor may be performed in any manner. Since the greater the degree of variation represented by the index value, the greater the deviation of the tip center from the center of the sleeve, in one embodiment, the magnitude of the misalignment of the tip may be determined with reference to the magnitude of the index value. Alternatively, in another embodiment, if the magnitude of the index value exceeds a predetermined threshold value that is appropriately set, it may be determined that readjustment of the tip centering is necessary. The magnitude of the misalignment of the tip center may be evaluated for each direction corresponding to the direction of the detected acceleration value.

[0024] Treatment process The process of checking the misalignment of the tip using the configuration of FIG. 2 may be performed during the tip centering adjustment process in the die-casting process cycle. More specifically, as shown in FIG. 4, when the tip centering adjustment, i.e., the adjustment to align the center of the tip with the center of the slip, is performed in any manner (S1: step 1), the detected values ​​of the acceleration sensor during the tip movement (during the above-mentioned section b) are collected, and an index value sd representing the degree of variation, such as the standard deviation, is calculated (S2: step 2). The index value sd is then compared with a threshold value Th (step 3). The threshold value Th may be a value that indicates that the misalignment of the tip has become so large that readjustment of the tip centering is necessary when the index value sd exceeds the threshold value Th, and may be determined through experiments, etc. Here, if the index value sd is greater than or equal to the threshold value Th, it is determined that the misalignment is large (step 4), and the tip centering adjustment (step 1) is performed again. On the other hand, when the index value sd is less than the threshold value Th, it is determined that the casting is in a centered state (the misalignment is within the acceptable range) (step 5), and while the casting process continues (N in step 6), the detection values ​​of the acceleration sensor during the tip movement are collected (step 2), and the index value sd is determined (step 3), and the misalignment state is monitored.

[0025] Thus, according to the configuration of this embodiment, it is possible to check the misalignment state of the tip relative to the sleeve of the molten metal injection device of the mold of the die-casting system while the tip is in operation, while the system is in operation, or during the casting process.

[0026] The above description has been made in relation to the embodiments of the present invention, but it will be apparent that many modifications and changes will be readily apparent to those skilled in the art, and the present invention is not limited to the above-described exemplary embodiments, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. A method for checking the misalignment of a tip supported by a rod inside a sleeve of an injection device that injects molten metal into a cavity of a die into which the molten metal is poured to form a casting, the method comprising: acquiring a detection value of an acceleration sensor provided in the injection device while the tip moves within the sleeve; calculating an index value representing a variation in the detection values ​​of the acceleration sensor acquired while the tip moves within the sleeve; determining a deviation of the center of the tip relative to the center of the sleeve based on the index value; A method comprising:

2. 2. The method according to claim 1, wherein it is determined that the greater the variation in the detected values ​​representing the index values, the greater the deviation of the center of the tip from the center of the sleeve.

3. 2. The method of claim 1, wherein when the variation in the detection value representing the index value reaches a predetermined threshold, it is determined that the center of the tip is misaligned with the center of the sleeve to such an extent that centering processing of the tip within the sleeve is necessary.

4. 2. The method of claim 1, wherein the index value is a standard deviation or variance of the amplitude of the detection values ​​of the acceleration sensor obtained while the tip moves within the sleeve.

5. 2. The method of claim 1, wherein the acceleration sensor is mounted on at least one of the tip, the rod, and the sleeve.

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