Die casting machine

Abstract

To provide a die casting machine capable of further accurately acquiring the amount of molten metal.SOLUTION: A die casting machine 10 includes: a robot 34 having a plurality of electrically controllable joints and a plurality of links connected by the plurality of joints; a ladle 32 attached to the robot 34; a sleeve 14 for receiving molten metal; and a controller 60. The controller 60 drives the robot 34 so that the position and the posture of the ladle 32 are three-dimensionally changed, conveys the molten metal to the sleeve 14 by the ladle 32, and calculates the amount of molten metal in the ladle 32 based on the load of at least one of the plurality of joints.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This specification discloses a die casting machine that uses a robot to move the ladle. [Background technology]

[0002] Conventionally, die casting machines equipped with a molten metal supply system that transports molten metal using a ladle have been known. In this case, the molten metal is pumped up from a melting furnace by the ladle and supplied to a sleeve attached to the main body of the die casting machine. In order to maintain high quality of die cast products, it is necessary to accurately detect the amount of molten metal supplied to the sleeve.

[0003] Therefore, techniques for measuring the amount of molten metal drawn up by a ladle have been proposed. For example, Patent Document 1 discloses a die-casting machine in which a ladle is moved by a ladle moving mechanism. Patent Document 1 discloses that the amount of molten metal in the ladle is calculated based on the level of the molten metal detected by an electrical sensor, the height of the molten metal level detected by a displacement sensor, or an image of the molten metal in the ladle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-192918 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 1 calculates the amount of molten metal based on the height and shape of the molten metal surface. However, the molten metal surface varies greatly depending on the position of the ladle. For example, the height and shape of the molten metal surface in the ladle vary greatly between when the ladle is facing straight up and when the ladle is tilted. Therefore, the technology of Patent Document 1 is prone to errors due to the position of the ladle, making it difficult to accurately calculate the amount of molten metal.

[0006] Therefore, this specification discloses a die-casting machine that can obtain the amount of molten metal more accurately. [Means for solving the problem]

[0007] The die-casting machine disclosed in this specification comprises a robot having a plurality of electrically controllable joints and a plurality of links connected by the plurality of joints, a ladle attached to the robot, a sleeve for receiving molten metal, and a controller, wherein the controller is configured to drive the robot so that the position and posture of the ladle change three-dimensionally, transport the molten metal to the sleeve with the ladle, and calculate the amount of molten metal in the ladle based on the load of at least one of the plurality of joints.

[0008] In this case, the robot has a plurality of motors provided at the plurality of joints, each motor moving the corresponding joint, and the controller is configured to calculate the amount of molten metal based on a change in the load when the robot changes from a first posture to a second posture, and the load may be an output torque or a current value of the motor.

[0009] Furthermore, both the first posture and the second posture may be postures in which the robot is temporarily stationary during the process of transporting molten metal from the molten metal furnace to the sleeve.

[0010] The first position may be a metering position in which excess molten metal is returned to the melt furnace, and the second position may be a pouring standby position in which the molten metal waits near the sleeve until it becomes possible to pour the molten metal.

[0011] The controller may also be configured to adjust an injection operation of extruding the molten metal from the sleeve into the mold based on the calculated amount of molten metal.

[0012] Another die-casting machine disclosed in this specification comprises a ladle that draws up molten metal and pours it into a sleeve, an output data collection unit that collects the trajectory of the ladle, an input data collection unit that collects the pouring quality and pouring conditions, and a controller, wherein the controller functions as an AI that has learned at least based on the trajectory collected by the output data collection unit and the pouring quality and pouring conditions collected by the input data collection unit so as to output a trajectory corresponding to a target pouring quality, and is configured to control the drive of the robot so that the trajectory of the robot or the ladle matches the trajectory output by the AI. [Effects of the Invention]

[0013] According to the die-casting machine disclosed in this specification, the amount of molten metal can be measured more accurately. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of a die-casting machine. [Figure 2] FIG. 10 is a schematic diagram showing an injection operation. [Figure 3] FIG. 10 is a diagram showing an example of calculation of the amount of molten metal. [Figure 4] FIG. 10 is a diagram showing an example of a movement profile of a plunger. [Figure 5] FIG. 1 is a diagram of a general neural network model. DETAILED DESCRIPTION OF THE INVENTION

[0015] The configuration of the die-casting machine 10 will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the die-casting machine 10. This die-casting machine 10 is a device that performs die-casting. For example, the die-casting machine 10 is a device that integrally molds large parts used in vehicles or aircraft, and is a device known as a mega-casting machine or giga-casting machine.

[0016] The die-casting machine 10 includes a machine body 12, a molten metal furnace 24, a melt supply device 30, and a controller 60. As shown in FIG. 2, the machine body 12 includes a mold 20 that forms a cavity space 22, and a sleeve 14 that communicates with the mold 20. After molten metal is injected into the cavity space 22 through the sleeve 14, the molten metal is cooled and solidified to produce a die-cast product. A detailed description of the configuration of the machine body 12 will be omitted.

[0017] The melting furnace 24 heats and melts the material metal (e.g., aluminum) of the product. The melted material metal, i.e., molten metal, is stored in the melting furnace 24. The melting furnace 24 is located at a position separated from the machine main body 12.

[0018] The melt supply device 30 supplies molten metal stored in the melt furnace 24 to the sleeve 14 of the machine body 12. The melt supply device 30 has a ladle 32 that stacks the molten metal and a robot 34 that transports the ladle 32. The robot 34 is an articulated robot having multiple links 36 connected via joints. Each of the multiple joints is provided with a motor as a power source, and the movement of each of the multiple joints is electrically controlled by the motor. Each motor is provided with a sensor (e.g., an encoder) for detecting the amount of drive. Then, as the posture of the robot 34 changes with the movement of the joints, the position and posture of the ladle 32 attached to the robot 34 are changed.

[0019] 1, the robot 34 has a base joint 40 that can rotate around a vertical axis, and four joints 42, 44, and 46 that can rotate around axes that are parallel to one another. Hereinafter, of the four joints 42, 44, and 46, the joint closest to the base end will be referred to as the "root joint 42," the joint closest to the tip end will be referred to as the "wrist joint 46," and the joint provided between the root joint 42 and the wrist joint 46 will be referred to as the "intermediate joint 44." The ladle 32 is attached to the tip end of the robot 34 via the wrist joint 46.

[0020] A controller 60, which will be described later, calculates the posture of the robot 34, and therefore the position of the ladle 32, based on the drive amounts of each of the multiple joints. The controller 60 also acquires the load amounts of each of the multiple joints. For example, the controller 60 may acquire the current value or motor output torque of a motor provided in the joint as the load amount of the joint. Alternatively, a torque sensor may be provided to detect the torque acting on the joint, and the detected value of the torque sensor may be acquired as the load amount of the joint. The controller 60 calculates the amount of molten metal pumped by the ladle 32 based on the load amounts of the joints, which will be described later.

[0021] The robot 34 uses the ladle 32 to draw up the molten metal from the melt furnace 24. The robot 34 then transports the ladle 32 to the vicinity of the pouring spout 16 of the sleeve 14 and causes the ladle 32 to pour the molten metal into the pouring spout 16. An optical camera 50 and a thermal camera 52 are provided near the sleeve 14 to capture images of the area around the sleeve 14. The controller 60 evaluates the pouring quality based on the images captured by the optical camera 50 and the thermal camera 52, which will be described later.

[0022] The molten metal poured into the sleeve 14 is injected by a plunger 18 (see FIG. 2) into a cavity space 22. The forward and backward movement of the plunger 18 is controlled by, for example, a hydraulic circuit (not shown).

[0023] The controller 60 controls the operation of the die-casting machine 10. The controller 60 is physically a computer having a processor 62 and a memory 64. Although the controller 60 is illustrated as a single computer in FIG. 1, the controller 60 may be configured by combining multiple computers that are physically separated from each other.

[0024] The controller 60 controls the operation of each part of the die-casting machine 10 based on instructions from an operator and detection values ​​from sensors provided at various locations on the die-casting machine 10. For example, the controller 60 controls the movement of the movable parts of the die-casting machine 10 (e.g., the mold 20, plunger 18, and robot 34) and the temperatures of the melting furnace 24 and the mold 20. The controller 60 in this example also calculates the amount of molten metal pumped up by the ladle 32 based on the load on the joints of the robot 34. The calculation of this amount of molten metal will be described below.

[0025] First, the reason for calculating the amount of molten metal will be explained. As shown in Fig. 2, the molten metal supplied to the sleeve 14 is injected into the cavity space 22 by the plunger 18. Here, when pouring the molten metal, the plunger 18 is retracted to the base end side of the sleeve 14. At this time, the volume Vc of the space surrounded by the sleeve 14 and the plunger 18 (hereinafter referred to as the "variable chamber 15") is larger than the volume Vm of the poured molten metal. Therefore, immediately after pouring, air is present above the surface of the molten metal, as shown in the ellipse in Fig. 2.

[0026] Thereafter, as the plunger 18 advances, the variable chamber 15 gradually becomes smaller. When the volume Vc of the variable chamber 15 becomes approximately equal to the volume Vm of the molten metal, the variable chamber 15 is filled with the molten metal. As the plunger 18 advances further, the molten metal is forced out of the variable chamber 15 into the cavity space 22. The pressure acting on the molten metal is relatively small until the molten metal fills most of the cavity space 22. After the molten metal fills most of the cavity space 22, the plunger 18 advances further, which applies pressure to the molten metal inside the cavity space 22, causing the molten metal to spread all the way to the edges of the cavity space 22. Note that the pressure inside the cavity space 22 may be reduced prior to injection in order to ensure that the molten metal reaches every detail.

[0027] That is, the section where the plunger 18 advances can be roughly divided into a first section K1 where the volume Vc of the variable chamber 15 is larger than the molten metal volume Vm, a second section K2 where Vc < Vm and the molten metal is extruded into the cavity space 22, and a third section K3 where a large pressure is required to extrude the molten metal. In the first section K1, in order to prevent the molten metal from surging and thus prevent the entrainment of air in the molten metal, the plunger 18 is required to move at a low speed. By preventing the entrainment of air, the generation of casting defects is reduced. Also, in the second section K2, in order to vigorously extrude the molten metal, the plunger 18 is required to move at a high speed. By moving the plunger 18 at a high speed and filling the molten metal in a short time, the variation in the solidification time of the molten metal is reduced. Furthermore, in the third section K3, in order to apply pressure, the plunger 18 is required to gradually decelerate.

[0028] That is, in order to obtain high-quality die-cast products, it is required to switch the moving speed of the plunger 18 at the boundary position between sections. However, the boundary positions of the three sections K1, K2, and K3 change depending on the amount of molten metal supplied from the ladle 32. Therefore, in order to switch the moving speed of the plunger 18 at an appropriate timing, it is necessary to accurately grasp the amount of molten metal supplied to the sleeve 14.

[0029] Therefore, in this example, when the ladle 32 is transported, the load on the joints of the robot 34 is acquired, and based on this load, the amount of molten metal is measured. That is, the load applied to the joints of the robot 34 changes depending on the weight of the ladle 32 held by the robot 34. However, the load applied to the joints does not change in proportion to the weight of the ladle 32, but also changes depending on the posture of the robot 34 and the like.

[0030] Therefore, in this example, a specified position is determined in advance, and the weight of the ladle 32 and the molten metal stored in the ladle 32 is calculated based on the load generated in the specified position. More specifically, the controller 60 calculates the amount of molten metal based on the change in the load on the joint when the ladle 32 is changed from the specified first position P1 to the second position P2. The procedure used for this calculation is not particularly limited. Figure 3 is a diagram illustrating an example of calculating the amount of molten metal.

[0031] 3 shows the robot 34 in a predetermined first position P1, and the lower part shows the robot 34 in a second position P2. For ease of explanation, the height of the center of gravity of the ladle 32 in the second position P2 is set to be the same as the height of the center of gravity of the ladle 32 in the first position P1.

[0032] First, consider the case when the robot 34 takes the first posture P1. When an object (i.e., the ladle 32 scooping up molten metal) is attached to the robot 34 in the first posture P1, the torque acting on the root joint 42 is defined as T1. Furthermore, when no object is attached to the end of the robot 34 in the first posture P1, the torque acting on the root joint 42 is defined as M1. Furthermore, the horizontal distance from the center of gravity G of the object to the root joint 42 is defined as D1. In this case, the weight W of the object can be expressed by the following equation (1).

[0033] T1=M1+W×D1 (1)

[0034] Similarly, when the robot 34 is in the second posture P2, the torque of the root joint 42 when there is no object is defined as M2, the torque of the root joint 42 when there is an object is defined as T2, and the horizontal distance from the center of gravity G of the object to the root joint 42 is defined as D2. In this case, the weight W of the object can be expressed by the following equation (2). T2=M2+W×D2 (2)

[0035] From these equations (1) and (2), the following equations (3) and (4) are further obtained. T2-T1=M2-M1+W×(D2-D1) (3) W=((T2-M2)-(T1-M1)) / (D2-D1) (4)

[0036] Here, M1 and M2 are obtained in advance by experiment or the like. D1 and D2 are also measured in advance. T1 and T2 can be obtained by actually measuring the output torque or applied current of the motor of the base joint 42 during the process of moving the robot 34 from the first position P1 to the second position P2 after the ladle 32 has actually pumped up the molten metal. Then, by substituting these values ​​into equation (4), the weight of the ladle 32, and therefore the weight of the molten metal in the ladle 32, can be obtained.

[0037] This calculation procedure is merely an example and may, of course, be modified as appropriate. For example, the first position P1 and the second position P2 may be modified as appropriate. Therefore, both the first position P1 and the second position P2 may be positions that the robot 34 can assume during the die-casting process. Furthermore, to reduce calculation errors in the amount of molten metal, both the first position P1 and the second position P2 may be positions in which the robot 34 temporarily stops during the process of transporting the molten metal from the melt furnace 24 to the sleeve 14. For example, after pumping the molten metal with the ladle 32, the robot 34 typically stops temporarily in a measuring position with the ladle 32 tilted to return the excess molten metal in the ladle 32 to the melt furnace 24. This measuring position may be referred to as the first position P1. Furthermore, the robot 34 typically assumes a waiting position near the sleeve 14 until the molten metal can be poured. This waiting position may be referred to as the second position P2. With this configuration, it is not necessary to have the robot 34 assume a dedicated position for calculating the amount of molten metal, and this prevents an increase in the cycle time in the die-casting process. In this case, the height of the center of gravity of the ladle 32 in the second position P2 may differ from the height of the center of gravity of the ladle 32 in the first position P1. In that case, the above formula (4) is modified to absorb the difference in the height of the center of gravity.

[0038] Furthermore, in the above description, only the torque of the base joint 42 is used, but the weight may also be calculated using the torque of other joints. Furthermore, in the above description, the amount of molten metal is calculated only once based on the difference in load between two postures. However, more postures may be used, or the amount of molten metal may be calculated multiple times. By calculating the amount of molten metal multiple times and then performing statistical processing (e.g., median, average, excluding outliers, etc.) on these multiple calculated values, the calculation accuracy of the amount of molten metal can be further improved.

[0039] Next, we will explain how to adjust the injection operation based on the amount of molten metal thus obtained. As described above, to obtain a high-quality die-cast product, it is necessary to switch the speed of the plunger 18 at the boundaries between the first section K1, the second section K2, and the third section K3. The boundary positions of these sections change depending on the amount of molten metal. Therefore, the controller 60 changes the movement profile of the plunger 18 according to the calculated amount of molten metal.

[0040] Fig. 4 is a diagram showing an example of a movement profile of plunger 18. In Fig. 4, the horizontal axis represents the position of plunger 18, and the vertical axis represents the speed of plunger 18. Solid line L1 represents the movement profile for a first amount of molten metal W1, and dashed line L2 represents the movement profile for a second amount of molten metal W2 that is greater than the first amount of molten metal W1. Note that in Fig. 4, line L2 is offset slightly upward from line L1 to prevent the lines from overlapping; in reality, line L1 and line L2 have the same waveform, just differing in the timing of the speed change.

[0041] As is clear from Figure 4, in this example, when the amount of molten metal is large, the timing of switching the speed is made earlier than when it is small. On the other hand, even if the amount of molten metal differs, the shape of the speed waveform of the plunger 18 itself is not changed. This is because, even if the amount of molten metal changes, the distances of the second section K2 and the third section K3 do not change as long as the mold 20 (and therefore the cavity space 22) does not change.

[0042] To achieve this control of the movement profile, the controller 60 stores in advance the speed waveform of the plunger 18 for each mold 20. The controller 60 also stores switching information linking the speed switching timing with the amount of molten metal. With each injection operation, the controller 60 compares the calculated amount of molten metal with the switching information to identify the corresponding speed switching timing. The controller 60 then controls the movement of the plunger 18 so that the movement speed switches at the identified timing. This allows the quality of die-cast products to be maintained at a high level.

[0043] Next, we will explain how to control the trajectory of the ladle 32 when pouring molten metal. Even if the amount of molten metal drawn up by the ladle 32 can be accurately detected, a large amount of molten metal may spill during the process of pouring from the ladle 32 into the sleeve 14. In this case, the amount of molten metal supplied to the sleeve 14 will naturally deviate from what was expected, making it difficult to switch the speed of the plunger 18 at the appropriate time. Furthermore, if part of the molten metal jumps up significantly during the pouring process, the amount of air entrained in the molten metal increases. Therefore, the quality of the pouring of the molten metal into the sleeve 14 is also important in order to maintain the quality of the die-cast product.

[0044] In this example, in order to maintain high pouring quality, the movement trajectory of the ladle 32 is generated by the controller 60. The controller 60 functions as a pre-trained AI so as to output a trajectory according to the target pouring quality. That is, a program relating to a trained model is stored in the memory 64 of the controller 60, and the processor 62 inputs the target pouring quality and pouring conditions into the trained model and outputs a target trajectory that will achieve the target pouring quality.

[0045] Here, the trained model may be constructed using, for example, a convolutional neural network. This trained model is trained in advance based on collected pouring quality, pouring conditions, and the trajectory of the ladle 32. The trajectory of the ladle 32 may be calculated, for example, from the movement amounts of multiple joints of the robot 34. As another embodiment, the die-casting machine 10 may be provided with one or more optical cameras 50 that capture images of the ladle 32 or the robot 34, and the trajectory of the ladle 32 may be calculated based on images captured by the one or more optical cameras 50. In this case, the sensors that measure the movement amounts of the joints and the optical cameras 50 function as an output data collection unit that collects trajectory data.

[0046] The pouring quality includes, for example, at least one of the amount of molten metal splashed around the sleeve 14, the time until pouring is completed, and the temperature distribution around the ladle 32. The amount of molten metal splashed may be calculated based on, for example, an image captured by the optical camera 50. As another embodiment, a pan 54 for receiving splashed molten metal and a weight sensor 56 for measuring the weight of the pan 54 may be provided below the sleeve 14. The amount of splashed molten metal may then be obtained based on changes in the detected value of the weight sensor 56. The temperature distribution around the ladle 32 can be obtained by, for example, analyzing a thermographic image captured by the thermal camera 52. The time until pouring is completed can be measured by a timer 66 provided in the controller 60. The pouring conditions include, for example, the amount of molten metal poured by the ladle 32. As described above, the amount of molten metal can be determined from the load on the joints of the robot 34. The timer 66, optical camera 50, thermal camera 52, weight sensor 56, etc. that collect this information function as an input data collection unit that collects pouring quality and pouring conditions.

[0047] FIG. 5 illustrates a typical neural network model 70. As shown in FIG. 5, the neural network model 70 includes an input layer 72, a middle layer 74, and an output layer 76. The number of middle layers 74 is not limited to one, but may be multiple. Each of the layers 72, 74, and 76 includes one or more nodes 78, 80, and 82, respectively. The nodes in different layers are connected by edges 84. While FIG. 5 illustrates only some of the edges 84, in reality, multiple edges 84 extend from a single node 78 or 80. Each edge 84 is assigned a weighting coefficient Wi. Furthermore, a bias b is assigned to the node 80 in the middle layer 74. In the neural network, the process of weighting and adding the values ​​of the nodes 78 and 80 and adding the bias b to the resulting value is repeated for each layer, and the final value obtained is output. This example also uses a neural network like the one shown in FIG. 5. In the pre-learning, the pouring quality and pouring conditions are set in the input node 78, and the bias b and weighting coefficient Wi are adjusted so that the final output approaches the trajectory of the ladle 32 when the pouring quality is obtained. The controller 60 repeatedly adjusts the bias b and weighting coefficient Wi, i.e., learns, for multiple cases.

[0048] When performing die-casting, the controller 60 inputs the target pouring quality and pouring conditions into the trained model 70 and acquires the trajectory of the ladle 32 that will achieve the target pouring quality. The controller 60 then controls the drive of the robot 34 so that the ladle 32 moves along this acquired trajectory. By calculating the trajectory of the ladle 32 using the trained model 70 in this manner, the pouring quality can be further improved, and the quality of the die-cast product can be further improved. Furthermore, during this die-casting process, the trajectory of the ladle 32, the pouring quality, and the pouring conditions can be collected, and the trained model 70 can be further trained based on the acquired data. This allows the appropriate trajectory to be calculated with higher accuracy.

[0049] It should be noted that the configurations described so far are merely examples, and other configurations may be changed as appropriate as long as the configuration of claim 1 is included. For example, in the description so far, the controller 60 calculates the amount of molten metal and the trajectory of the ladle 32. However, as long as the controller 60 calculates the amount of molten metal, it is not necessary to calculate the trajectory of the ladle 32. Furthermore, as long as the amount of molten metal is calculated based on the load on at least one of the multiple joints of the robot 34, the calculation format is not particularly limited. [Explanation of symbols]

[0050] 10 die-casting machine, 12 machine body, 14 sleeve, 15 variable chamber, 16 pouring spout, 18 plunger, 20 mold, 22 cavity space, 24 melting furnace, 30 melting device, 32 ladle, 34 robot, 36 link, 40 base joint, 42 root joint, 44 intermediate joint, 46 wrist joint, 50 optical camera, 52 thermal camera, 54 pan, 56 weight sensor, 60 controller, 62 processor, 64 memory, 66 timer, 70 model, 72 input layer, 74 hidden layer, 76 output layer, 78, 80, 82 nodes, 84 edges, K1 first section, K2 second section, K3 third section.

Claims

1. A die-casting machine, a robot having a plurality of electrically controllable joints and a plurality of links connected by the plurality of joints; a ladle attached to the robot; a sleeve for receiving molten metal; A controller; wherein the controller Driving the robot so that the position and posture of the ladle change three-dimensionally to transport the molten metal to the sleeve with the ladle; calculating the amount of molten metal in the ladle based on the load of at least one of the plurality of joints; The die-casting machine is characterized by being configured as follows.

2. 2. The die casting machine according to claim 1, the robot has a plurality of motors provided in the plurality of joints, each of which moves the corresponding joint; the controller is configured to calculate the amount of molten metal based on a change in the load when the robot changes from a first posture to a second posture, The load is an output torque or a current value of the motor. A die-casting machine characterized by:

3. 3. The die casting machine according to claim 2, The first posture and the second posture are both postures in which the robot temporarily rests during the process of transporting the molten metal from the molten metal furnace to the sleeve. A die-casting machine characterized by:

4. 4. The die casting machine according to claim 3, the first position is a measuring position in which excess molten metal among the pumped molten metal is returned to the molten metal furnace, The second position is a waiting position for pouring molten metal in the vicinity of the sleeve until the molten metal can be poured. A die-casting machine characterized by:

5. 2. The die casting machine according to claim 1, The controller is configured to adjust an injection operation of extruding the molten metal from the sleeve into the mold based on the calculated amount of molten metal. A die-casting machine characterized by:

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