Die casting machine and die casting method based on die casting machine

Abstract

The invention provides a die-casting machine and a die-casting method based on the die-casting machine. The pressure maintaining effect can be obtained even after the pouring gate is solidified and closed, and therefore the internal quality of a casting can be improved. A die casting machine (10) is provided with: a die (28) including a fixed die (30) and a movable die (32); a cavity (34) formed inside the mold (28); an injection plunger (44) that injects a filling melt into the cavity (34); and a mold closing device (12) for opening, closing and closing the movable mold (32) with respect to the fixed mold (30). Furthermore, the injection pressure (P) is set such that the opening force (Y) of the molten metal injected into the cavity (34) on the movable mold (32) is equal to or less than the set value of the clamping force (X) of the movable mold (32), the molten metal having the same volume as the cavity (34) is injected and filled by the injection plunger (44), and then the injection pressure (P) is set such that the opening force (Y) is greater than the clamping force (X), and the injection pressure (P) is set such that the opening force (Y) is greater than the clamping force (X). The melt is injected in an amount exceeding the volume of the cavity (34).

Description

Technical Field

[0001] The present invention relates to a die casting machine for injecting molten metal into a mold to cast a casting, and a die casting method using the die casting machine. Background Art

[0002] In conventional die-casting machines, a ladle measures and draws up molten aluminum alloy or other molten metal in a melting furnace for each shot, supplies the drawn-up molten metal to a molten metal supply port of an injection sleeve, and then advances an injection plunger, which is retractable within the injection sleeve, to inject and fill the mold cavity with the molten metal, thereby casting a casting.

[0003] Typically, in die casting using a die casting machine, when the injection plunger pressurizes the molten metal filling the mold cavity, a force acts in the direction of opening the mold (mold opening force) based on Pascal's principle. This mold opening can cause burrs and flash on the casting, so the force holding the mold (mold clamping force) is typically set to be greater than the mold opening force.

[0004] Among the known casting defects caused by die casting using a die casting machine are shrinkage cavities (solidification shrinkage holes) caused by the volumetric contraction of the molten metal filling the mold cavity as it cools and solidifies. Castings with such defects have poor mechanical properties. Therefore, a common method is to reduce defects by replenishing the volumetric contraction of the molten metal due to the pressurization of the injection plunger after filling (a holding pressure effect) (see Patent Document 1, for example).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-065062 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, in conventional die-casting methods using die-casting machines, the molten metal is injected into the mold cavity at high speed. Consequently, the gate, which serves as the inflow point into the mold cavity, is quite narrow and thin, causing it to solidify immediately after filling. Consequently, the molten metal is prevented from replenishing the volumetric contraction caused by the pressure applied by the injection plunger, preventing a sufficient pressure-holding effect.

[0010] The present invention has been made in view of such problems, and its object is to provide a die casting machine and a die casting method using the die casting machine, which can obtain a pressure holding effect even after solidification progresses and the gate is closed, thereby improving the internal quality of the casting.

[0011] Means for solving problems

[0012] According to one embodiment of the present invention, a die-casting machine is provided, which comprises: a mold, which is composed of a fixed mold and a movable mold; a cavity, which is formed inside the mold; an injection plunger, which injects and fills molten metal into the cavity; and a clamping device, which opens, closes and clamps the movable mold relative to the fixed mold, the injection plunger sets the injection pressure in such a way that the opening force of the movable mold exerted by the molten metal injected into the cavity is equal to or less than the set value of the clamping force of the clamping device, and injects and fills the molten metal in an amount equal to the volume of the cavity, and then sets the injection pressure in such a way that the opening force is greater than the clamping force, and injects and fills the molten metal in an amount exceeding the volume of the cavity.

[0013] Preferably, after the injection plunger injects and fills the molten metal in an amount equal to the volume of the cavity, while a cold hard layer of the molten metal is formed on the surface of the cavity, the injection pressure is increased to inject and fill the molten metal in an amount exceeding the volume of the cavity.

[0014] According to another embodiment of the present invention, a die-casting method based on a die-casting machine is provided, wherein the die-casting machine comprises: a mold including a fixed mold and a movable mold; a cavity formed inside the mold; an injection plunger for injecting and filling molten metal into the cavity; and a clamping device for opening, closing and clamping the movable mold relative to the fixed mold, wherein the injection pressure is set in such a manner that the opening force of the movable mold exerted by the molten metal injected into the cavity is equal to or less than a set value of the clamping force of the clamping device, and the molten metal is injected and filled in an amount equal to the volume of the cavity by the injection plunger, and then the injection pressure is set in such a manner that the opening force is greater than the clamping force, and the molten metal is injected and filled in an amount exceeding the volume of the cavity.

[0015] Preferably, after injecting and filling the molten metal in an amount equal to the volume of the cavity, while a cold hard layer of the molten metal is formed on the surface of the cavity, the injection pressure is increased to inject and fill the molten metal in an amount exceeding the volume of the cavity.

[0016] Effects of the Invention

[0017] According to the die casting machine and the die casting method using the die casting machine of the present invention, a pressure holding effect can be obtained even after solidification progresses and the gate is closed, thereby improving the internal quality of the casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a diagram showing an example of a die casting machine 10 according to the embodiment.

[0019] Figure 2 Graphs showing changes in the mold clamping force X (X′) and the injection pressure P (P′) during a casting process using the die casting machine 10 .

[0020] Figure 3 This is a diagram showing the state of the mold 28 and the molten metal in the casting process using the die casting machine 10 , and shows the state where the molten metal is injected and filled into the cavity.

[0021] Figure 4 This figure shows the state of the mold 28 and the molten metal in the casting process using the die casting machine 10 , and shows a state in which the movable mold 32 is separated from the fixed mold 30 .

[0022] Figure 5 The figure shows the state of the mold 28 and the molten metal in the casting process using the die casting machine 10 , and shows a state in which the movable mold 32 is separated from the fixed mold 30 and the gate is closed.

[0023] Figure 6 The figure shows the state of the mold 28 and the molten metal in the casting process using the die casting machine 10 , showing a state where the gap between the movable mold 32 and the fixed mold 30 has changed and the solidification of the molten metal has been completed. DETAILED DESCRIPTION

[0024] (Structure of Die Casting Machine 10)

[0025] like Figure 1 As shown, the die casting machine 10 of this embodiment generally includes a mold clamping device 12 , an injection device 14 , and a control device 15 .

[0026] The mold clamping device 12 includes a machine table 16 , a fixed platen 18 , a movable platen 20 , a tailstock 22 , a tie rod 24 , and a toggle mechanism 26 .

[0027] The machine table 16 is a component that constitutes other components of the mold clamping device 12 and serves as a base for the injection device 14 .

[0028] The fixed plate 18 is fixed to the machine table 16 and has a fixed mold 30 constituting the mold 28 mounted thereon.

[0029] The movable platen 20 is a member that slides on the machine table 16 so as to approach and separate from the fixed platen 18, and is mounted with a movable mold 32 constituting the mold 28. The movable mold 32 is in contact with the fixed mold 30, forming a cavity 34 filled with molten metal.

[0030] The tailstock 22 is a component placed on the machine table 16 on the side opposite to the fixed platen 18 when viewed from the movable platen 20 .

[0031] The tie rod 24 is a round rod-shaped member with one end fixed to the fixed platen 18 and the other end fixed to the tailstock 22. Furthermore, the tie rod 24 is inserted through a tie rod insertion hole 36 formed in the movable platen 20, which is positioned between the fixed platen 18 and the tailstock 22. This allows the movable platen 20 to slide along the tie rod 24 on the machine table 16 in the left-right direction in the figure. Furthermore, multiple tie rods 24 (e.g., four) are used.

[0032] The toggle mechanism 26 is a mechanism for moving the movable platen 20 toward, away from, and holding the fixed platen 18 . The mold clamping drive mechanism 31 is attached to the tailstock 22 .

[0033] The driving force of the mold clamping drive mechanism 31 is transmitted via the toggle mechanism 26, causing the movable platen 20 to move along the tie rods 24 (left and right in the figure). If the movable platen 20 moves to the left, the fixed mold 30 and movable mold 32 separate. On the other hand, if the movable platen 20 moves to the right, the fixed mold 30 and movable mold 32 come into contact, forming a cavity (internal space) 34 within the mold 28. Furthermore, if pressure is further applied in a direction that moves the movable platen 20 to the right, the fixed mold 30 and movable mold 32 are clamped.

[0034] At this point, the toggle mechanism 26 gradually extends from its bent state. When the movable mold 32 contacts the fixed mold 30, the tie rod 24 begins to extend, generating strain proportional to the tensile stress. The tension in the tie rod 24 acts as a clamping force on the fixed mold 30 and movable mold 32. When the toggle mechanism 26 reaches its maximum extension, the tie rod 24 also extends to its maximum. When the movable mold 32 reaches the clamped position, the specified clamping force is applied to the fixed mold 30 and movable mold 32.

[0035] The injection device 14 generally includes an injection mechanism 38 and a hydraulic actuation mechanism 40 .

[0036] The injection mechanism 38 includes an injection sleeve 42 , an injection plunger 44 , an injection piston 46 , and an injection cylinder 48 .

[0037] The injection sleeve 42 is provided integrally with the fixed platen 18 and is a cylindrical member. A melt supply port 50 for supplying melt is formed at an upper portion thereof.

[0038] The injection plunger 44 is a substantially rod-shaped member provided in the injection sleeve 42 so as to be movable forward and backward.

[0039] The injection piston 46 is formed on the rear end side (the end opposite to the end in contact with the melt) of the injection plunger 44 and is a portion pressed by the hydraulic oil O.

[0040] The injection cylinder 48 is a cylindrical member that allows the injection piston 46 to move forward and backward, and is filled with hydraulic oil O.

[0041] The hydraulic actuator 40 is a mechanism for supplying hydraulic oil O used in the injection process of the injection plunger 44 to the injection cylinder 48, thereby causing the hydraulic oil to act on the injection piston 46. In addition, by supplying pressurized oil to the injection cylinder 48, a force (injection pressure P) in the forward direction to the left in the figure is applied to the injection plunger 44.

[0042] The control device 15 detects position information of the injection piston 46 and actuates the hydraulic actuator 40 during the injection process and the return process of the injection plunger 44 , and also performs all necessary control for the die casting machine 10 .

[0043] (Casting Process of the Die Casting Machine 10 of the Present Embodiment)

[0044] Next, use Figures 2 to 6 The procedure for casting a molded body using the die casting machine 10 of this embodiment will be described. Figure 2 This is a graph showing changes in the mold clamping force X, the injection pressure P, and the mold opening force Y during the entire casting process of the die casting machine 10 , and is therefore referred to during the entire casting process.

[0045] The control device 15 operates the mold clamping drive mechanism 31 to close the movable mold 32 relative to the fixed mold 30, and then performs mold clamping with a predetermined mold clamping force X ( Figure 2 (1)).

[0046] Then, the control device 15 advances the injection plunger 44 to inject and fill the molten metal into the cavity 34 of the mold 28 ( Figure 3 At this time, the control device 15 sets the injection pressure P so that the opening force Y of the molten metal injected into the cavity 34 on the movable mold 32 is equal to or less than the clamping force X of the movable mold 32 on the fixed mold 30, thereby injecting and filling the molten metal in an amount substantially equal to the volume of the cavity 34 ( Figure 2 (2)).

[0047] Next, the control device 15 injects and fills the cavity 34 with a volume of molten liquid that is substantially equal to the volume of the cavity 34, and then forms a chill layer ( Figure 2 (2) to (3)), and then the injection plunger 44 is moved forward by increasing the injection pressure P, and the amount of molten metal exceeding the volume of the cavity 34 is injected and filled ( Figure 2 (3)).

[0048] The chill layer (cooled solidified film layer) refers to the metal structure formed when the molten metal contacts the surface of the cavity 34 and is rapidly cooled. The chill layer formed on the surface of the casting has a fine and dense metal structure and is therefore known to be a useful material for improving the strength of die-cast castings.

[0049] When the mold opening force Y is less than the mold clamping force X (Y≤X), the injection plunger 44 cannot move forward in the direction of the cavity 34. However, if the injection pressure P is increased (the injection pressure after the increase is referred to as "injection pressure P'") and the mold opening force Y is made greater than the mold clamping force X (Y>X), the injection plunger 44 moves forward and can inject and fill an amount of molten liquid that exceeds the volume of the cavity 34.

[0050] In addition, since the mold opening force Y is greater than the mold closing force X, Figure 4 As shown, the movable mold 32 and the movable platen 20 are slightly separated from the fixed mold 30 by the mold opening force Y ( Figure 2 (3)). This separation is not caused by the bending of the toggle mechanism 26, but by the elongation caused by the elastic deformation of the tie rod 24. In addition, when the tie rod 24 is elongated, the mold clamping force X increases by the amount of elongation (the increased mold clamping force is referred to as "mold clamping force X'"). The mold opening force Y generated by the injection pressure P' of the molten metal is extended by a predetermined length, whereby the mold clamping force X' rises to be equal to the mold opening force Y. Therefore, if the mold clamping force X' is equal to the mold opening force Y (Y=X'), the separation of the movable mold 32 and the movable plate 20 stops ( Figure 2 (4)).

[0051] When the movable mold 32 separates from the fixed mold 30, forming a gap W between the two at the mold dividing surface, molten metal may flow into this gap, potentially causing burrs and flash in the casting. However, in the die-casting machine 10 of this embodiment, as described above, after a chill layer is formed on the surface of the cavity 34, the injection plunger 44 is advanced by injection pressure P'. Therefore, the chill layer on the surface of the cavity 34 serves to cover the gap W, preventing residual unsolidified molten metal from leaking out of the gap W. Specifically, at the moment when the injection plunger 44 is advanced by injection pressure P', although the molten metal on the surface of the cavity 34 has solidified, most of the molten metal inside the cavity 34 has not yet solidified.

[0052] After the separation of the movable mold 32 and the movable platen 20 from the fixed mold 30 stops, the injection plunger 44 also stops ( Figure 2 (4)~(5)). Then, as Figure 5 As shown, the melt at the gate Z is first solidified, and the gate is closed ( Figure 2 (5) to (6)). As a result, the pressurization and supply of the melt from the injection plunger 44 to the cavity 34 are cut off, and the pressure holding effect of the injection plunger 44 is interrupted.

[0053] Since the gate is blocked, even if the injection plunger 44 is pressurized, the molten metal filling the cavity 34 does not act on the mold opening force Y based on the Pascal principle. Therefore, the mold opening force Y, which was kept constant, begins to decrease rapidly ( Figure 2(5)). On the other hand, since the tie rod 24 is stretched in advance, the tie rod 24 contracts as the mold opening force Y decreases, and the movable mold 32 and the movable plate 20 want to approach the fixed mold 30. However, since the molten metal in the cavity 34 (a part of it is not molten metal but solidified, but the solidified part is still referred to as "molten metal") is sandwiched between the movable mold 32 and the fixed mold 30, the movable mold 32 and the fixed mold 30 approach each other in accordance with the volume reduction caused by the solidification shrinkage of the molten metal. Therefore, the mold clamping force X' or X (compression force) from the movable mold 32 and the fixed mold 30 is always applied to the molten metal, and pressure is generated in the molten metal according to Pascal's principle. In addition, in order to reduce the volume due to solidification shrinkage, the molten metal that is pre-filled with more than the volume of the cavity 34 is supplied. If the tie rod 24 contracts during the stage of supplying the molten metal, the mold clamping force X' or X is reduced ( Figure 2 (5)~(7)).

[0054] And, as Figure 6 As shown, at the stage where the solidification of the melt in the cavity 34 is completed, there is a gap between the fixed mold 30 and the movable mold 32. Figure 2 The gap W in (4) to (5) is narrower than the gap W'. Thus, before the solidification of the molten metal in the cavity 34 is completed, the clamping force X' or X (compression force) from the movable mold 32 and the fixed mold 30 is always applied, and pressure can be continuously generated in the molten metal, so that the pressure holding effect can be obtained even after the gate is closed. This is achieved by Figure 2 The mold clamping force at (7) to (8) is greater than the mold clamping force X at (1) when the mold clamping is completed.

[0055] Then, after the solidification of the molten metal is completed, the mold clamping drive mechanism 31 of the mold clamping device 12 is actuated to separate the movable mold 32 from the fixed mold 30 (mold opening) ( Figure 2 (8)), the casting is taken out from the cavity 34 using an ejector pin (not shown). Thus, the die casting machine 10 completes the casting of the casting.

[0056] Furthermore, in the die casting machine 10 of the present embodiment, as described above, by controlling the injection plunger 44, only the injection pressure P (P') (related to the mold opening force) of the molten metal in the cavity 34 is adjusted. This allows for free adjustment of the separation distance (gap W) of the mold 28 during the casting process, the time at which the molten metal solidifies (the time at which the molten metal solidifies) and the time at which the molten metal solidifies (the time at which the molten metal solidifies) are adjusted without controlling the mold clamping drive mechanism 31 during the casting process. Figure 2 (7)) of the clamping force X.

[0057] (Variation 1)

[0058] The fixed mold 30 and the movable mold 32 involved in the above-mentioned embodiment show an example in which the mold dividing surface is flat up to the periphery, but the present invention is not limited to this, and a shear edge structure can be adopted. The shear edge structure refers to a fitting structure formed between the fixed mold 30 and the movable mold 32, which can be inserted and removed while sliding with each other. The adoption of the shear edge structure is effective in preventing the molten metal injected into the cavity 34 from leaking out of the mold. In particular, in the present invention, the effect of preventing the molten metal from leaking out brought about by the adoption of the shear edge structure can be utilized to further expand the gap W (further extend the tie rod 24), so that the holding pressure effect can be made more significant by increasing the clamping force X applied to the molten metal and increasing the amount of molten metal supplied. The shear edge structure is also called a splitting structure or a dimple structure.

[0059] (Variation 2)

[0060] While the melt in the above-described embodiments is based on a premise of being composed solely of a liquid phase exceeding the melting point of the metal, the present invention is not limited to this. For example, a melt consisting solely of a liquid phase may be used, where the metal is cooled to a semi-solidified state, or a metal in a semi-molten state where a solid phase is heated to generate a liquid phase, where both solid and liquid coexist. In the present invention, both melts consisting solely of a liquid phase and semi-solidified metals are collectively referred to as melts.

[0061] (Variation 3)

[0062] While the injection device 14 in the above-described embodiment is hydraulically driven, the present invention is not limited thereto. For example, the injection device 14 may also be configured as an electric cylinder driven by a motor. Because this can improve plunger motion accuracy compared to a hydraulic cylinder, the present invention is preferably applied to a die-casting machine 10 that can more stably vary the injection pressure P.

[0063] (Variation 4)

[0064] Although the example in which the die casting machine 10 is configured as a horizontal type is shown, the present invention is not limited thereto. In the present invention, the die casting machine 10 may also be configured as a vertical type.

[0065] (Variant 5)

[0066] In this embodiment, Figure 2 The change process of the mold opening force Y shown in (2) to (6) is an example of two stages. Figure 2 The mold opening force Y of (3) to (5) is the minimum mold opening force level in the present invention. That is, the mold opening force can also be changed by changing the injection pressure P (P') in 3 or 4 or more levels.

[0067] (Variation 6)

[0068] Furthermore, the present invention can also be applied to multi-cavity molds (i.e., molds capable of producing multiple products in a single molding operation) with multiple cavities within a single mold. When producing multiple products in a single molding operation, the closing time of each gate varies. Relying solely on conventional injection plunger pressure application can lead to fluctuations in the pressure-holding effect, which in turn causes fluctuations in internal quality. However, as described above, in the present invention, since the clamping force X' or X (compression force) is constantly applied from the movable mold 32 and the fixed mold 30, a pressure-holding effect can be achieved even after the gates are closed. Therefore, the present invention is also applicable to such molds for producing multiple products simultaneously.

[0069] The embodiments disclosed herein are to be considered in all respects as illustrative and non-restrictive. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims and equivalents thereof.

[0070] Description of reference numerals:

[0071] 10…Die-casting machine, 12…Mold clamping device, 14…Injection unit, 15…Control unit, 16…Machine table, 18…Fixed platen, 20…Moveable platen, 22…Tailstock, 24…Tie rod, 26…Toggle mechanism, 28…Mold, 30…Fixed mold, 31…Mold clamping drive mechanism, 32…Moveable mold, 34…Cavity, 36…Tie rod insertion hole, 38…Injection mechanism, 40…Hydraulic actuator, 42…Injection sleeve, 44…Injection plunger, 46…Injection piston, 48…Injection cylinder, 50…Metal supply port, O…Hydraulic oil, P…Injection pressure, X…Mold clamping force, Y…Mold opening force, Z…Gate, W…Clearance

Claims

1. A die-casting machine comprising: A mold, comprising a fixed mold and a movable mold; a cavity formed inside the mold; an injection plunger for injecting and filling melt into the cavity; and A mold clamping device that opens, closes, and clamps the movable mold relative to the fixed mold. The injection plunger sets the injection pressure so that the opening force of the movable mold exerted by the molten metal injected into the cavity is equal to or less than the set value of the clamping force of the clamping device, and injects and fills the molten metal in an amount equal to the volume of the cavity. Then, the injection pressure is set so that the mold opening force is greater than the mold clamping force, and the molten metal is injected and filled in an amount exceeding the volume of the cavity.

2. The die casting machine according to claim 1, wherein: After the injection plunger injects and fills the molten metal in an amount equal to the volume of the cavity, the injection plunger increases the injection pressure to inject and fill the molten metal in an amount exceeding the volume of the cavity while a chilled layer of the molten metal is formed on the surface of the cavity.

3. A die-casting method using a die-casting machine, the die-casting machine comprising: A mold, comprising a fixed mold and a movable mold; a cavity formed inside the mold; an injection plunger for injecting and filling melt into the cavity; and A mold clamping device that opens, closes, and clamps the movable mold relative to the fixed mold. In the die casting method of the die casting machine, The injection pressure is set so that the mold opening force exerted by the molten metal injected into the mold cavity on the movable mold is equal to or less than the set value of the mold clamping force of the mold clamping device, and the molten metal is injected into the mold cavity in an amount equal to the volume of the mold cavity by the injection plunger. Then, the injection pressure is set so that the mold opening force is greater than the mold clamping force, and the molten metal in an amount exceeding the volume of the cavity is injected and filled by the injection plunger.

4. The die casting method based on a die casting machine according to claim 3, wherein: After the molten metal is injected into the cavity in an amount equal to the volume of the cavity, the injection pressure is increased to inject and fill the cavity with an amount of the molten metal exceeding the volume of the cavity while a chilled layer of the molten metal is formed on the surface of the cavity.

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