Die casting quality control method using runner pressure method

Abstract

When manufacturing die-cast products by first pressurizing, then shielding the molten metal, and then applying secondary pressurization, this prevents quality degradation due to backflow of molten metal from the shielded area during secondary pressurization. [Solution] In a die-casting manufacturing method in which, in addition to a first pressurizing means for injecting molten metal into a die-casting mold, a second pressurizing means having a pin for pressurizing a passage directly connected to the cavity is provided, and an orifice is provided in the pressurizing path of the second pressurizing means, thereby shielding the molten metal, a pressurizing stroke means for the plunger pin of the first pressurizing means is provided, and the amount of plunger back by the pressurizing stroke means is detected after secondary pressurization by the second pressurizing means, and an alarm can be output if this detected value is greater than or equal to a set value.

Description

Technical Field

[0001] The present invention relates to a die-casting quality control method by a runner pressurization method, and particularly to a method for monitoring that a runner pressurization pin moves back due to backflow from a pressurization part when performing runner pressurization as secondary pressurization following primary pressurization by a plunger.

Background Art

[0002] The casting method of die-cast products is performed by filling a cavity made in a mold with molten metal such as aluminum using a plunger, and taking out a product solidified into a shape following the cavity. In addition, a pressure boosting mechanism for further boosting the plunger is provided at the rear of the plunger in order to prevent voids from forming when forming the product. The filling and pressurization action into the cavity by the plunger is performed to manufacture a product conforming to the cavity shape.

[0003] In recent years, in order to further remove voids from products pressurized by a plunger, a structure has been proposed in which a pressurization pin for pressing the product part is separately arranged in the runner part leading to the product after primary pressurization by the plunger, and the product is secondarily pressed with a high pressure. In particular, an orifice is provided at the sliding part of the pressurization pin so that the molten metal does not flow back when applying high pressure, and it is pressed with high pressure (Patent Document 1).

[0004] In the runner pressurization method, a backflow prevention groove stops the backflow of molten metal when performing runner pressurization, but there are occasional backflows. The reasons for this are (1) Deviation of the core of the pressurization pin, (2) Deterioration of the metal seal due to a change in the balance between the molten metal temperature and the mold temperature, (3) Sliding due to a mold release agent, etc. are considered. When these occur, when performing runner pressurization, the metal in the mold cannot reach the target pressure, the density of the die-cast product decreases, and the quality deteriorates.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 7090254 [Overview of the project] [Problems that the invention aims to solve]

[0006] In view of the above-mentioned problems, this invention utilizes a method for detecting the molten metal backflow phenomenon during runner pressurization. This method involves monitoring the value of the injection plunger, which retracts when molten metal backflows. Alternatively, the outflow state may be obtained from mold information. [Means for solving the problem]

[0007] To achieve the above objective, the present invention is configured as follows: In a die-casting manufacturing method in which, in addition to a first pressurizing means for injecting molten metal into a die-casting mold, a second pressurizing means having a pin for pressurizing a passage directly connected to the cavity is provided, an orifice is provided in the pressurizing path of the second pressurizing means, and the molten metal is shielded at the orifice portion, the present invention is characterized in that a stroke detection means for the plunger of the first pressurizing means is provided, the plunger back amount is detected by the stroke detection means after secondary pressurization by the second pressurizing means is started, and an alarm can be output if this detected value is greater than or equal to a set value.

[0008] Furthermore, in the absence of the plunger stroke detection means described above, the die-casting quality control method is characterized by detecting the metal pressure inside the die-casting mold and outputting an alarm when this metal pressure falls outside the allowable value. [Effects of the Invention]

[0009] We believed that monitoring only the runner pressure device was insufficient for detecting backflow, given the requirements for JIS strength certification of die-cast products. Initially, we considered installing metal pressure sensors inside the mold and managing this data, but there were issues with space and concerns about cable breakage when installing pressure sensors in each mold. In this respect, the plunger monitoring of the die-casting machine is highly accurate and can distinguish between forward and backward movement. By changing the software for this monitoring, it should be possible to perform monitoring without the runner pressure device, thus resolving the issue.

[0010] Therefore, with the above configuration, the orifice prevents backflow of molten metal by injecting molten metal into the outer circumference of the secondary pressure pin. However, if backflow of molten metal occurs due to misalignment of the pressure pin, deterioration of the metal seal due to changes in the balance between molten metal temperature and mold temperature, or slippage due to the release agent, this will manifest as a change in biscuit thickness and as the amount of plunger return movement. In the present invention, backflow of molten metal can be detected by the plunger back, and an alarm can be issued if it exceeds a certain level, thereby ensuring the quality of die-cast products produced by runner pressurization. Furthermore, some devices lack a means for detecting the stroke for the plunger's return movement. Even in such devices, if the above-mentioned backflow is excessive, the target pressure will not be reached. If this falls outside the allowable value, an alarm will be issued. This value will also be recorded. This also ensures the quality of die-cast products produced by runner pressurization. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view of the main part of the die-casting manufacturing apparatus according to the embodiment. [Figure 2] Figure 1 is a cross-sectional view of the main part of the injection section of the die-casting manufacturing apparatus. [Figure 3] This is a diagram illustrating the operation of the second pressurizing means. [Figure 4] This is a longitudinal cross-sectional view showing the stroke detection means of a die-casting manufacturing apparatus. [Figure 5] This is a partially enlarged cross-sectional view of the outer surface of a piston rod in a die-casting machine. [Figure 6] This is a characteristic diagram of this embodiment. [Figure 7] This is a diagram illustrating the configuration for obtaining metal pressure information as mold information. [Figure 8] This is a characteristic diagram of another embodiment. [Modes for carrying out the invention]

[0012] Figure 1 shows a cross-sectional view of the main part of a die-casting manufacturing apparatus according to this embodiment. The die-casting manufacturing apparatus 10 comprises a movable mold 14 attached to a movable platen 12 and a fixed mold 18 attached to a fixed platen 16. Molten metal is injected into a cavity 20 formed by bringing the two molds 14 and 18 into contact, and a product with a shape conforming to the cavity 20 is produced. The product can be removed from the cavity 20 by separating the molds 14 and 18 and operating an ejection pin 22 provided on the back of the movable mold 14.

[0013] A molten metal supply means 24 is positioned below the cavity 20 as an injection unit for supplying molten metal to the cavity 20 of such a die-casting manufacturing apparatus 10. This consists of a first pressurizing means 30 comprising an injection sleeve 26 that is mounted horizontally through the fixed platen 16 and reaches the fixed mold 18, a plunger 28 disposed inside the injection sleeve 26, and a pressurizing device located behind the plunger 28 that can push and pull the plunger 28.

[0014] A runner 32 is formed at the front end of the injection sleeve 26, which serves as a passage to the cavity 20. This runner 32 consists of a stream divider runner section 34 that extends almost horizontally from the injection sleeve 26 and a rising runner section 36 that is turned upward so as to be directly connected to the lower part of the cavity 20. The molten metal pushed out by the plunger 28 passes through the stream divider runner section 34, is turned upward by the rising runner section 36, and is injected into the cavity 20.

[0015] In such a runner 32, a second pressurizing means 38 for secondarily pressurizing the molten metal in the cavity 20 is provided in the rising runner portion 36. This second pressurizing means 38 is composed of an actuator 40 equipped at the lower part of the molds 14 and 18, and a pressurizing pin 42 attached so as to move in and out from the lower part to the upper part of the rising runner portion 36. The diameter d of the pressurizing pin 42 is made smaller than the inner diameter D of the rising runner portion 36, enabling the vertical sliding of the pressurizing pin 42 in the rising runner portion 36. Therefore, the amount of press-fitting of the pressurizing pin 42 into the rising runner portion 36 will improve the density of the product by the cavity 20.

[0016] Incidentally, in this embodiment, particularly, an orifice 44 for reducing its inner diameter is formed on the rising runner portion 36 side (portion B in FIG. 2) above the intersection (section A - B in FIG. 2) of the rising runner portion 36 and the sub - runner portion 34. This is formed by forming an annular protrusion 46 with a rectangular cross - section on the inner diameter portion of the rising runner portion 36. The height of the protrusion 46 (that is, the inner diameter dimension of the rising runner portion 36) is adjusted to match the outer diameter d of the pressurizing pin 42 as much as possible so that a metal seal can be achieved here. Specifically, although it depends on the size of the cavity 20, the gap dimension Δ is half of the difference between the inner diameter D of the rising runner portion 36 and the outer diameter d of the pressurizing pin 42. The height of the annular protrusion 46 is determined so that the gap dimension Δ becomes 1 / 2 to 1 / 3 or less. That is, half of the difference between the inner diameter of the annular protrusion 46 and the outer diameter d of the pressurizing pin 42 is the gap dimension δ of the metal seal portion, and δ = Δ×1 / 2, preferably δ = Δ×1 / 3. The lower limit value is the value when the metal seal is damaged. Also, the axial length L of the annular protrusion 46 is set to about 10 mm to ensure that the metal seal is performed reliably.

[0017] After the injection by the plunger 28 of the first pressurizing means 30 is completed, the second pressurizing means 38 configured as described above starts pressurizing from the position shown in Fig. 3(1). When the pressurizing pin 42 approaches the annular protrusion 46 (Fig. 3(2)), the molten metal at the upper part is inserted into the orifice 44 portion to form a metal seal, and a shielding function is exhibited at that portion. Therefore, due to the metal seal at the orifice 44 portion, the amount of molten metal filled into the cavity 20 increases, and by the pushing operation of the pressurizing pin 42, the stroke becomes longer and the operation is completed (Fig. 3(3)).

[0018] In addition, the first pressurizing means is provided with a plunger stroke detection means. Fig. 4 shows an example of a plunger stroke detection means of a die-casting machine. A piston rod 52 is slidably mounted on the cylinder head 50 of the injection cylinder of the die-casting machine via a guide bush and a packing. As shown in Fig. 5, on the outer peripheral surface of this piston rod 52, spiral grooves 54 with a depth d of about 0.2 mm are formed at a predetermined pitch. After chromium plating the cylinder head, a non-magnetic chromium layer 56 with a thickness t of about 0.03 mm is formed by grinding. As a result, a magnetic and non-magnetic screw-shaped pattern is formed alternately at a predetermined pitch.

[0019] On the other hand, a fixing member 58 is fixedly provided on the cylinder head 50, and an adjustment member 62 is inserted and fixed in a through hole 60 provided in this fixing member 58. The screw portion of a magnetic sensor 64 is screwed onto the adjustment member 62, and the screwing position is regulated and fixed by a lock nut to form a slight gap C between the magnetic sensor 64 and the outer peripheral surface of the piston rod 52.

[0020] At the tip of the magnetic sensor 64 facing the piston rod 52, a magnetic sensitive element such as a permanent magnet and a plurality of magnetoresistive elements are incorporated. The piston rod 52 is coupled to a plunger rod 68 by a coupling 66, and a plunger tip 28 formed at its tip is fitted into an injection sleeve 26 to extrude the molten metal flowing into the injection sleeve 26 into the mold.

[0021] When the piston rod 52 is rapidly pushed to the left by the injection cylinder, it pushes the molten metal in the injection sleeve 26 into the mold for pouring. As the piston rod 52 moves at this time, the magnetic sensor 64 receives magnetic fluctuations and generates a pulse signal. By amplifying and shaping this signal and counting its repetition frequency, the direction and amount of change in the stroke of the piston rod 52 can be determined.

[0022] The magnetic sensor used here detects the amount of movement and velocity of an object in response to magnetic changes. While there are various types of magnetic sensors, such as magnetoresistive elements, magnetic grid elements, and Hall effect elements, this embodiment uses a magnetoresistive element whose resistance changes in response to changes in magnetic flux, and which can be output as an AC signal with a changing voltage.

[0023] As described above, in this embodiment, injection into the cavity 20 is performed by the first pressurizing means 30, and the second pressurizing means 38 is activated when the runner 32 is filled with molten metal. Then, while the operating piston 42 is reaching the intersection of the splitter runner section 34 and the rising runner section 36 (Figure 2A→B), it performs a normal extrusion action. However, as soon as the splitter runner section 34 is cut and the piston reaches the rising runner section 36, the annular projection 46 reaches the section, and the molten metal solidifies in the gap δ due to the metal seal, and the pressure is cut off at this point (Figure 3(2)). Therefore, the molten runner on the cavity 20 side, which is located above the operating piston 42 and has not yet solidified, is pushed towards the cavity 20 side due to the cut-off pressure.

[0024] This allows the operating piston 42 to advance further than in the conventional stroke, and the second pressurizing means 38 enables the production of more compact products.

[0025] However, when pressurization begins by the second pressurizing means 38, if there is backflow of molten metal from the backflow prevention section, the effect of the second pressurization is halved. This backflow manifests as a change in the thickness of the biscuit portion and can be detected as plunger back of the first pressurizing means 30. Represented in a characteristic diagram, this can be seen as point S, where the injection displacement shown in the injection displacement waveform diagram of Figure 6 temporarily decreases. This can be detected by the stroke detection means as the return movement of the piston rod 52, and the direction and amount of return movement can be managed as plunger back from the detection by the magnetic sensor 64. In reality, runner pressurization starts about 0.2 seconds after injection is completed, but if there is backflow, the injection plunger will move back. In this embodiment, the position measurement of the plunger of the die-casting machine can be detected with high accuracy in units of 0.1 mm. In cases of significant backflow, for example, the piston rod 52 moves back from 440.8 to 438.3. A stroke amount of -1.0 mm or less can be considered normal. Therefore, by issuing an alarm when the stroke exceeds -1.0 mm, it is possible to maintain the quality of die-cast products.

[0026] Furthermore, some devices lack a means for detecting the stroke of the plunger's return movement. Even in such devices, if there is a large amount of backflow, the target pressure will not be reached. If this value falls outside the acceptable range, an alarm should be issued. This value should also be recorded. This, too, helps to ensure the quality of die-cast products through runner pressurization.

[0027] If the stroke detection means described above is not available, it can be detected by the metal pressure inside the cavity, as shown in Figure 7. In this case, a strain gauge is attached to the tip of the ejector pin 70 or the metal pressure is detected by a load cell 72. The metal pressure can then be directly determined, and an alarm can be issued if the target metal pressure is not reached or if it falls outside the allowable value. The relationship between runner pressure and metal pressure is shown in Figure 8. [Industrial applicability]

[0028] The present invention allows for the control of leakage of molten metal from the backflow prevention portion when a die-casting apparatus is used to extrude and mold molten metal into a cavity by the plunger pressurizing action of a first pressurizing means, and subsequently pressurizes the runner with a second pressurizing means. [Explanation of Symbols]

[0029] 10... Die-casting manufacturing equipment, 12...Moveable board, 14...Movable mold, 16……Fixed board, 18... Fixed mold, 20... Cavity, 22... Push pin, 24... means of supplying hot water, 26... Injection sleeve, 28... Plunger, 30...First pressurizing means, 32... Runner, 34... Splitter Runner Section, 36... The Standing Runners Club, 38... Second pressurizing means, 40... Actuator, 42... Pressure pin, 44... Orifice, 46... Annular projection, 48... Through hole, 50... Cylinder head, 52... Piston rod, 54……Spiral groove, 56... Chromium layer, 58... Fixing member, 60...Throat, 62... Adjustment member, 64... Magnetic sensor, 66... ​​Coupling, 68... Plunger rod, 70... Push pin, 72... Load cell.

Claims

[Claim 1] In a die-casting manufacturing method in which, in addition to a first pressurizing means for injecting molten metal into a die-casting mold, a second pressurizing means having a pin for pressurizing a passage directly connected to the cavity is provided, and an orifice is provided in the pressurizing path of the second pressurizing means, and the molten metal is shielded at the orifice portion, A die-casting quality control method using a runner pressurization method, characterized in that a stroke detection means for the plunger of the first pressurization means is provided, the plunger back amount is detected by the stroke detection means after secondary pressurization by the second pressurization means is started, and an alarm can be output if this detected value is greater than or equal to a set value.

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