JPH10225758A - Method for casting low melting point alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten cooling time and to improve productivity. SOLUTION: In this low m.p. casting method, dies 1 in a die device freely openable/closable by a die clamping device are clamed and the molten low m.p. alloy stored in a holding furnace is injected and pressurized with an injecting device by abutting a gate valve 50 freely communicating/shutting-out the molten metal and revercible of molten metal to the holding furnace on a runner part in a die cavity 2 and jointing them, cooled and solidified, then a cast product is taken out. Then, in the casting work process consisting of the die clamping process, gate valve jointing process, injecting process, pressure holding process, cooling process, gate shutting-off process, gate valve releasing process, die opening process and product taking-out process, a non-solidified molten metal recovering process for recovering the non-solidified molten metal remained in the die cavity 1 by working a back flow sucking action of the molten metal with the injecting device, is added between the cooling process and the gate shutting-off process followed to the cooling process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-melting point alloy casting method for molding a low-melting point metal core or the like used for injection molding of a resin. The present invention relates to a low-melting point alloy casting method in which an unsolidified molten metal in a mold cavity is sucked by an injection pump of an injection device after the completion to add a non-solidified molten metal collecting step, thereby shortening a cooling step time.

[0002]

2. Description of the Related Art Conventionally, for example, when an intake manifold for injecting gasoline into an automobile engine is injection-molded with a resin material, a core for the intake manifold is required. In order to melt the core, it was necessary to manufacture the core from a low melting point alloy, for example, a low melting point alloy such as a Sn-Bi alloy. In this case, the molten metal of these low-melting point alloys is transferred, for example, through a molten metal pipeline held by a melting furnace or a holding furnace, and injected into a mold cavity of a molding apparatus such as a die casting machine. It was cast and manufactured as a molded product. In this case, the casting process involves a mold closing process, a gate valve / docking process, an injection process, a pressure holding process, a cooling process, a gate shutoff process, a gate valve / release process, a mold opening process, and a product removal process. Was. That is, the gate valve connected to the holding furnace by the molten metal pipe and capable of communicating and shutting off the molten metal is brought into contact with the runner portion of the mold cavity of the closed mold to be docked, and the molten metal stored in the holding furnace is discharged. After injection into the mold cavity, the pressure was maintained (pressurized), the cooling time was held for a certain period of time, the gate valve was shut off, the gate valve was separated from the runner part and retracted, and the product was taken out after opening the mold. .

[0003]

However, in the above working process, it is necessary to open the mold and take out the cast product until the molten metal injected into the mold cavity and held under pressure is completely solidified. For this reason, there is a problem that a long time is required for the cooling step, a work time for one shot is increased, and productivity is low.

[0004]

In order to solve the above-mentioned problems, a low melting point alloy casting method according to the present invention is characterized in that a mold of a mold apparatus which can be opened and closed by a mold clamping apparatus is clamped and stored in a holding furnace. A gate valve that allows free flow and backflow of the molten metal of the low melting point alloy that can flow back and forth into the holding furnace contacts the runner part of the mold cavity, docks it, injects it with an injection device, pressurizes it, and cools it. A low-melting alloy casting method in which a mold is opened and a molded product is taken out after solidification. In the casting process consisting of the mold opening process and the product removal process, between the cooling process and the subsequent gate shut-off process, the unsolidification remaining in the mold cavity by using the backflow suction action of the molten metal by the injection device by the injection device. Adding the non-solidified metal recovery step of sucking the hot water into the injection pump.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The low melting point alloy casting method of the present invention comprises:
Mold closing process, gate valve / docking process, injection process,
Packing process, cooling process, gate shut-off process, gate valve
In the casting process consisting of the release process, mold opening process and product removal process, the injection device acts on the backflow suction of the molten metal by the injection device between the cooling process and the subsequent gate shutoff process to remain in the mold cavity. Since the unsolidified molten metal recovery step of recovering the unsolidified molten metal to be added is added, the process moves to the next unsolidified molten metal recovery step of the next step without waiting for a long time for all the molten metal in the mold cavity to completely cool and solidify, and the cooling time is, for example, , Halving, etc. As a result, a hollow product is obtained in which the unsolidified molten metal is extracted from the center and the cavity is hollowed out, leaving the vicinity of the mold surface where cooling and solidification is relatively fast, but this product is used as a core for resin injection molding and injection After molding, it is only melted by heating, so that a certain strength is sufficient and there is no problem.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 4 relate to an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a low melting point alloy casting apparatus, FIG. 2 is an overall configuration diagram of the low melting point alloy casting apparatus, and FIG. 3 is a hydraulic circuit of a gate valve. FIG. 4 and FIG. 4 are explanatory diagrams of the operation of the gate valve.

As shown in FIGS. 1 and 2, a low melting point alloy casting apparatus 300 includes a holding furnace 10 for storing and holding a molten metal M.
And an injection device (injection pump 20) immersed in the holding furnace 10.
A and a pump switching valve 30, a communication shutoff valve 70, etc.) 20, and a gate valve 50 and a gate valve 50 for controlling communication and shutoff of the molten metal M and a molten metal pipe 40 serving as a supply line of the molten metal M in the holding furnace 10. A return line 60 for returning the molten metal M from the furnace to the holding furnace 10, a mold device 100, and a mold clamping device (not shown) for opening and closing the mold device and for clamping the mold device. The temperature control device 80 for keeping the temperature of the pipe 60 and the holding furnace 10 and the pipe 40 described above,
Temperature control unit 80A for keeping 60 warm and injection device 2
0 and a control device 200 that controls the operation of the gate valve 50.

The holding furnace 10 stores a molten metal M in a metal container, covers the upper opening, and heats and heats the surroundings with a heat medium. 20A, the injection device 20 including the pump switching valve 30 and one communication cutoff valve 70 is housed. The injection pump (hot water supply pump) 20A of the injection device 20 is immersed in the molten metal M in the holding furnace 10, and is disposed. The piston 20b is servo-operated in a cylindrical cylinder 20a that is open at the top and sealed at the lower end. The motor 20 and a ball screw 22a are provided so as to be slidable in the vertical direction via a ball screw 22a. A through hole 20c formed in the lower end surface of the cylinder 20a is connected to the pump switching valve 30. The pump switching valve 30 includes a port connected to the holding furnace 10, a port connected to the through hole 20 c, and the molten metal pipe 4.
The valve body 36 at the lower end of the valve rod 34 which rises and falls in the vertical direction by the operation of the fluid pressure cylinder 32 is moved up and down inside the body 30a having a port communicating with the port 0 to communicate with each of these ports. Things.

The molten metal pipe 40 connected to one of the ports of the body 30a of the pump switching valve 30 has a gate valve 5 via a fixed pipe and a flexible pipe connected thereto.
Contact 0.

As shown in FIGS. 2 and 3, the gate valve 50 has a pressure plunger 50a connected to a piston rod of a pressure cylinder 50b fitted in a through hole inside a cylindrical valve body 51. A docking cylinder 5 slidably formed in the axial direction and connected to the valve body 51.
2, the gate valve 50 is configured so as to be able to move forward (upward) or retreat (downward). As shown in FIG. 3, two openings are provided in the upper side surface of the valve body 51, and each of the two openings is provided.
0 and connected to the return line 60.

The gate valve 50 is connected to a distal end of a piston rod of a docking cylinder 52 which is detachably fixed to a lower end surface of a fixed mold 110A via a base block (not shown). The entire valve main body 51 is arranged to be able to move up and down in accordance with the forward and backward movements. Further, a pressurizing cylinder 50b for vertically moving the pressurizing plunger (also referred to as a plunger) 50a with respect to the valve body 51 is provided. In this way,
The gate valve 50 is capable of docking and detaching the mold 1 to and from the runner portion 3 and is capable of moving up and down the pressurizing plunger 50a, and is provided with a molten metal passage provided in the valve body 51 at right angles to the axial direction. Communication with and disconnection from the runner unit 3 becomes possible.

On the other hand, a return pipe 60 for the molten metal M, which is composed of a flexible pipe and a fixed pipe connected to the flexible pipe, is connected to another opening of the gate valve 50, and the communication pipe is immersed in the holding furnace 10. Holding furnace 1 via shut-off valve 70
It communicates with the molten metal in 0. The gate valve 50 is provided with a temperature control pipe 80a through which the heat medium supplied by the temperature control unit 80A passes. Gate valve 50
Is controlled by a hydraulic circuit shown in FIG.

In the vicinity of the uppermost part and the lowermost part of the molten metal pipe 40,
It is desirable to provide a stop valve or a plug that can communicate with and shut off the atmosphere. The reason is,
This is for discharging the molten metal in the molten metal pipe 40 to the outside during a long-term outage.

The communication cutoff valve 70 is, similarly to the above-described pump switching valve 30, a body 70a fixed to the body 30a.
A port connected to the return line 60 and a port communicating with the molten metal in the holding furnace are formed therein, and a valve body at the lower end of a valve rod 74 that moves up and down by the operation of the fluid pressure cylinder 72 on the way. The port is lifted up and down to shut off communication with this port. In addition, the melt pipe 40 and the return pipe 60
The fixed pipe is a double pipe through which the molten metal passes through the inside and the heat medium passes through the outside. The flexible pipe which is difficult to make a double pipe is a single pipe, and the outside is heated and kept warm by the flexible heater 80b. . The hydraulic cylinder 32 and the hydraulic cylinder 72 usually use pneumatic cylinders rather than hydraulic cylinders.

On the other hand, as shown in FIG. 2, the controller 200 includes a controller 210 formed of a personal computer, a converter 220a, a counter board 220b, and a PIO board 220c connected between the controller 210 and the servomotor 21. And servo amplifier 2
20, an AD converter 230 disposed between the controller 210 and the gate valve 50 and between the controller 210 and the temperature controller 80, and a plurality of transmitters 2
30a, a thermocouple 240 and a servomotor 21
And oscillates an operation command to the gate valve 50 to control the temperature of the molten metal M.

FIG. 3 is a hydraulic system diagram for driving and operating the gate valve 50. Flow control is performed on both the pressure cylinder 50b for operating the pressure plunger 50a and the docking cylinder 52 for raising and lowering the entire gate valve 50. Valve 5
4a, 54b, solenoid valves 56a, 56b, pressure reducing valve 58a,
The oil pressure source 59 and the oil tank 59a are connected by an oil pressure pipe via 58b.

The operation of the low-melting point alloy casting apparatus 300 of the present invention thus configured will be described with reference to FIG.
The description will be given in order below. First, the valve element 36 in the pump switching valve 30 is lowered to the lower limit, the port of the supply line 40 is closed, and the inside of the holding furnace and the through hole 20c are closed.
Is opened, and the servo motor 21 is driven to raise the piston 20b of the injection pump (hot water supply pump) 20A through the ball screw mechanism 22 to thereby raise the cylinder 20.
A prescribed amount of molten metal M is sucked and taken into a. At this time, the communication shut-off valve 70 also lowers the valve body 76 to the lower limit, and cuts off the communication between the return line 60 and the holding furnace 10.

Next, the gate valve 50 is advanced in the direction of the mold, and the tip (upper end) of the gate valve 50 is pressed against the runner of the mold cavity 110a so that the gate valve 50 is brought into close contact with the mold 110 (this step). This is the docking step of FIG. 4). The pressurizing plunger 50a of the gate valve 50 is retracted. The valve body 36 of the pump switching valve 30 is raised to the upper limit, the piston 20b of the hot water supply pump 20A is lowered, and the cylinder 20a
Of molten metal M in the supply line 40 and the gate valve 5
The mold is filled into the mold cavity via the nozzle 0 (injection step in FIG. 4). After the filling is completed, the torque of the servomotor 21 is controlled for a certain period of time to control the pressing force of the molten metal (pressure keeping step in FIG. 4).

Next, a cooling process for a predetermined time is started. This cooling time is a time greatly shortened from the conventional cooling time, and when the molten metal near the surface of the mold cavity is solidified, and the center portion is in a semi-flow state that has not yet completely solidified. is there. At this point, the process immediately shifts to the next unsolidified molten metal recovery step. The method of collecting the unsolidified metal in the mold cavity and the runner in this step is as follows: the communication shutoff valve 70 is closed, the valve body 36 of the pump switching valve 30 is raised, and the supply pipe 40 and the hot water supply pump 20 are communicated. Then, the pressurizing plunger 50a is lowered, the piston 20b is raised, and a suction force is applied to the molten metal pipe 40 to suck the molten metal into the injection pump 20A of the injection device 20 through the molten metal pipe 40 (unsolidified metal collecting step in FIG. 4). .

After the unsolidified metal recovery step has timed out, the pressurizing plunger 50a of the gate valve 50 is raised to the forward limit, and the molten metal M in the molten metal pipe 40 and the return pipe 60 leaks from the gate valve 50. It is prevented from coming out (gate shut-off step in FIG. 4). When one shot is completed and the mold is opened and the product is taken out, or when the molten metal M is to be circulated during the waiting time such as the application of the release agent for the next shot, the gate valve 50 is moved from the mold. After retracting, pressurizing plunger 5
0a is held in the forward position, and the molten metal M is
It flows into the holding furnace 10 in order of → the gate valve 50 → the return line 60. Incidentally, in the above, when the piston 20b reaches the lower limit and the transporting ability is lost, the piston 20b is raised to take the molten metal M into the cylinder 20a by the same procedure as temporarily stopping the circulation of the molten metal M. . Thereafter, the gate valve 50 that has been docked to the runner unit 3 is retracted (downward) so as to be detached from the runner unit 3 and the mold is opened to take out the product.

As described above, in the low melting point alloy casting apparatus 300 of the present invention, the gate valve 50 is docked to the runner section 3 of the mold cavity 2, the injection pump 20A is controlled to perform injection, and injection is performed. After the pressure-holding step, the cooling step was rounded up and the unsolidified molten metal recovery step was immediately performed, thereby greatly shortening the conventional cooling time. Also, unlike the prior art, the molten metal does not leak from the tip of the gate valve when the gate valve 50 is detached, even if the height position of the runner portion is not higher than the liquid level of the molten metal in the holding furnace 10. Therefore, there is no restriction on the height position, and dies having different heights can be freely changed. And the gate valve 5
0 is mounted on the lower end surface of the fixed mold 1A so as to be able to move up and down, so that the space around the gate valve can be saved.

[0022]

As described above, in the method for casting a low melting point alloy according to the present invention, the injection device performs the backflow suction action of the molten metal between the cooling step and the subsequent gate shut-off step. The addition of an unsolidified molten metal recovery step to recover the unsolidified molten metal remaining in the cavity can greatly reduce the time of the cooling step, and as a result, the time required for one cycle (casting cycle time) is shortened. The performance is greatly improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a low melting point alloy casting apparatus according to an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a low melting point alloy casting apparatus according to an embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram of the gate valve according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of an operation of the gate valve according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 mold 2 mold cavity 3 runner section 10 holding furnace 10a crucible 20 injection device pump 20A injection pump (hot water supply pump) 20a cylinder 20b piston 20c through hole 21 servo motor 22 ball screw mechanism 22a ball screw 22b ball nut 30 pump switching valve 30a Body 32 Fluid pressure cylinder 34 Valve rod 36 Valve element 40 Molten pipeline 50 Gate valve 50a Pressurizing plunger (plunger) 50b Pressurizing cylinder 51 Valve body 52 Docking cylinder 54a, 54b Flow control valve 56a, 56b Solenoid valve 58a, 58b Decompression Valve 59 Hydraulic source 59a Oil tank 60 Return line 70 Communication cutoff valve 72 Fluid pressure cylinder 74 Valve rod 76 Valve element 80 Temperature control device 80A Temperature control unit 80a Temperature control pipe 80b Flexible heater 100 Gold Molding device 200 Control device 300 Low melting point alloy casting device M Molten metal (Molten metal)

Claims (1)

[Claims] 1. A molten metal of a low melting point alloy stored in a holding furnace by clamping a mold of a mold device which can be opened and closed by a mold clamping device,
A gate valve that can freely flow and shut off the molten metal and that can flow back to the holding furnace contacts the runner part of the mold cavity, docks it, injects it with an injection device, pressurizes it, cools and solidifies, then opens the mold and molds A low-melting alloy casting method for extracting products, comprising a mold closing step, a gate valve docking step, an injection step,
Packing process, cooling process, gate shut-off process, gate valve
In the casting process consisting of the release process, mold opening process and product removal process, the injection device acts on the backflow suction of the molten metal by the injection device between the cooling process and the subsequent gate shutoff process to remain in the mold cavity. A method for casting a low-melting alloy, characterized by adding an unsolidified molten metal recovery step of recovering unsolidified molten metal.