JP3477414B2 - Injection molding method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and apparatus for heating and melting a supplied raw material chip in a cylinder of an injection molding machine and injecting it into a mold for molding.

[0002]

2. Description of the Related Art Generally, as a method for injection molding a light alloy such as a magnesium alloy, there are a die casting method and a thixomolding method. The die-casting method uses a light alloy ingot such as magnesium as a molding material, and the molten metal melted in the furnace is supplied into the sleeve by an automatic water heater or by manual pumping, and the reciprocating motion provided in the sleeve By advancing a possible plunger at high speed, the molten metal is injected and filled in the mold cavity.

On the other hand, the thixomolding method uses light alloy chips obtained by cutting a light alloy ingot such as magnesium as a raw material, heats it in a cylinder of an injection molding machine, and fluidizes it without exposing it to the atmosphere. It is a semi-molten slurry (thixotropic state) that is excellent in injection and is directly injected into the mold for molding. Specifically, as shown in FIG. 7, the light alloy tip 30 having a diameter of about 3 to 5 mm is
It is supplied to the inside of the cylinder 32 through the hopper 31 and is transferred forward by rotationally driving the screw 33 that is reciprocally mounted inside the cylinder 32. The light alloy tip 30 is in a molten state by being heated by the electric heater 34 attached to the outer peripheral portion of the cylinder 32 while being transported forward in the cylinder 32 by the rotation of the screw 33. At this time, the screw 33 moves the hopper 3 at a constant speed.
When the screw 33 moves backward to the first side and reaches a predetermined backward stroke, the rotation and backward movement of the screw 33 is finished, and a predetermined amount of molten material is stored in a storage portion in front of the screw 33, and the screw 33 is moved forward to move the nozzle to the nozzle. It injects into the mold cavity 37 formed in the mold 36 via 35.

[0004]

As described above, the conventional injection molding method has the following problems. In the die casting method, when the molten metal is supplied from the furnace to the sleeve, the molten metal supply error becomes about 5% or more due to fluctuations in the liquid surface height and the molten metal temperature and variations in the water heater in the case of the automatic water heater, There is a problem in that there is variation.
Therefore, when the molten metal supply is small, molding defects such as defective filling and wrinkles occur in the molded product. On the other hand, when the molten metal supply is large, excessive burrs are generated in the molded product and There are problems such as lack of accuracy. Further, in the case of manual drawing, the accuracy of molten metal supply is lower because the measurement is performed by visual measurement.

On the other hand, in the thixomolding method, since the raw material chips are simultaneously transferred, heated and melted in a single cylinder, the transfer and melting behavior of the raw material chips in the cylinder becomes complicated. For example, in the case of magnesium alloy, the solidus temperature is about 500 ° C on the base side of the cylinder.
The liquidus temperature of the tip side is set to about 600 ° C, and the magnesium alloy chips at room temperature and the molten magnesium alloy at the forming temperature are continuously placed from the root side to the tip side in a single cylinder. Will exist.

As a result, there is a problem that excessive rotation resistance occurs when the screw rotates due to the variation of the raw material chips and the melted state, which causes defective measurement of the molten raw material.
Similar to the die-casting method, if there is a poor metering, if the molten metal supply is small, the molded product will have defective filling such as wrinkles, and if the molten metal supply is large, the molded product will be overfilled. There are problems such as occurrence of various burrs and lack of dimensional accuracy. Also, when molding large products or shortening the molding time, high melting capacity is required, but to increase the heating area of the cylinder, the screw and cylinder become large and large electric heaters are added. There is a need to.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an injection molding method and apparatus capable of preventing defective measurement and shortening the molding time.

[0008]

In order to solve the above problems, in the invention according to claim 1 of the present invention, the supplied raw material chips (1) are heated and melted in the injection cylinder (7). , In the injection molding method of injecting into the molds (11a, 11b) for molding, the raw material chips (1) are transferred in the measuring cylinder (3) while being preheated to a temperature at which the chip shape can be maintained, and the measurement is completed. After that, in the injection cylinder (7) arranged in the vertical direction, the raw material chip (1) is moved up to the heating and melting section at a low speed by the injection piston (8),
In the heating and melting section, the raw material chip (1) is rapidly heated to a temperature at which the raw material chip (1) is melted,
It is characterized in that it is moved upward at a high speed and injected into the mold (11a, 11b).

According to the second aspect of the present invention, an injection molding apparatus for heating and melting the supplied raw material chips (1) and injecting them into the molds (11a, 11b) for molding. In (2), a measuring cylinder (3) to which the raw material chip (1) is supplied from one end, and a measuring screw (4) which is disposed in the measuring cylinder (3) and carries out the quantitative transfer of the raw material chip (1). A measuring and transferring means (6) comprising a preheating means (5) for preheating the raw material chips (1) to a temperature at which the shape of the chips can be maintained; and a measuring cylinder (3) connected to the other end and arranged vertically. Installed injection cylinder (7)
And an injection piston (8) disposed in the injection cylinder (7) and reciprocating in the injection cylinder (7), and attached to the injection cylinder (7) to melt and heat the raw material chip (1) at high speed. And a mold (11a, 11b) arranged on the upper side of the injection cylinder (7), and a metering transfer means (6).
At this point, the raw material chips (1) are metered and transferred while preheating so that the chip shape can be maintained, and the melt injection means (10)
And the injection piston (8) slowly moves the raw material chips (1) after the measurement to the heating and melting section where the high-speed heating means (9) is arranged, and the raw material chips ( 1) is rapidly heated to a temperature at which it is in a molten state, and the melted raw material chips (1) are moved up at a high speed so as to be injected into the molds (11a, 11b). To do.

According to a third aspect of the invention, the raw material chip (1) is a light alloy chip such as a magnesium alloy.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a metal injection molding machine of the present invention will be described in detail with reference to the drawings. 1 is a schematic cross-sectional configuration diagram of a metal injection molding apparatus showing an embodiment of the present invention, FIG.
Is a block diagram showing the state of the weighing process, FIG. 3 is a block diagram showing the state of the heating and melting process in the apparatus of FIG. 1, and FIG.
1 is a configuration diagram showing a state of an injection pressure holding process in the apparatus of FIG. 1, FIG. 5 is a configuration diagram showing a state of a product taking-out and weighing step in the apparatus of FIG. 1, and FIG. 6 is a chart illustrating an injection molding process. It is a figure. In the metal injection molding apparatus according to the present embodiment, the raw material chip 1 is preheated in the injection molding apparatus 2 that heats and melts the supplied raw material chip 1 and injects it into the molds 11a and 11b to perform molding. Weighing and transferring means 6 for measuring and transferring, and melt injection means 1 for melting the transferred raw material chip 1 and injecting it into the molds 11a, 11b.
0, and the raw material chip 1 is preheated by the measuring and transferring means 6 and is then weighed and transferred to the melt injection means 10, and the raw material chip 1 transferred by the melt injection means 10 is melted at a high speed, It is designed to be injected into the molds 11a and 11b. The raw material chip 1 is a light alloy chip such as a magnesium alloy such as AZ91D.

The metering and transferring means 6 is arranged horizontally in the metering cylinder 3 as shown in the figure, and a metering screw 4 which is disposed in the metering cylinder 3 and which meteredly transfers the raw material chips 1 by rotational driving by a motor. It comprises a preheating means 5 for preheating. A hopper 12 for supplying the raw material chips 1 is arranged at one end of the measuring screw 4, and Ar gas is supplied together with the raw material chips 1 through a pipe for preventing oxidation. The preheating means 5 is, for example, an electric heater, and preheats the raw material chip 1 to a temperature at which the chip shape can be maintained and a solidus temperature ± 20 ° C. For example, in the case of AZ91D among magnesium alloys, since the solidus temperature is about 470 ° C., it is preheated to be in the range of 450 to 490 ° C.

The melt injection means 10 is arranged vertically and is connected vertically to the other end of the measuring cylinder 3 by an injection cylinder 7.
And an injection piston 8 disposed inside the injection cylinder 7 and capable of reciprocating up and down, and a high-speed heating means (melt heating means) mounted around the upper side surface of the injection cylinder 7 for high-speed heating of the raw material chip 1. 9 and 9. As described above, in the present embodiment, the vertical injection molding apparatus has the injection cylinder 7 in the vertical direction.

The other end of the measuring cylinder 3 is opened and communicated with the lower side surface of the injection cylinder 7 to form a raw material supply port 13, and the raw material chip 1 is supplied from the measuring and transferring means 6. The high-speed heating means 9 is, for example, an induction heating device. Further, a thermocouple 14 is provided together with the rapid heating means 9, detects the temperature of the melted raw material chip 1 in the injection cylinder 7, and controls the rapid heating means 9 so as to reach a predetermined temperature.
The injection piston 8 stands by below the raw material supply port 13 at the time of measurement, transfers the raw material chips 1 supplied from the measurement transfer means 6 upward, and moves up to the high speed heating means 9 at a low speed, When injecting into the molds 11a and 11b, it is controlled so as to rise at a high speed. After the injection, the injection piston 8 is lowered to the position below the original material supply port 13.

The high-speed heating means 9 heats the raw material chip 1 to a temperature at which the raw material chips 1 are in a molten state, that is, a liquidus temperature of ± 40 ° C., after the raw material has been supplied by the measuring and transferring means 6. For example, in the case of AZ91D among magnesium alloys, the liquidus temperature is about 5
Since it is 95 degreeC, it heats to 555-635 degreeC. An Ar gas pipe is connected to the injection cylinder 7, and Ar gas is supplied as needed to prevent oxidation. The fixed mold 1 is attached to the tip of the nozzle of the melt injection means 10.
1a is arranged, and a mold cavity 15 is formed between the movable mold 1b and the movable mold 11b. Mold cavity 1
Reference numeral 5 is connected to a pipe of a vacuum device, and the vacuum device evacuates during the measuring process to the end of the injection pressure holding process.

Next, the injection molding operation of the present embodiment will be described with reference to FIGS. As shown in FIG. 2, when the raw material chip 1 is supplied from the hopper 12 into the measuring cylinder 3 together with Ar gas, the measuring screw 4 is rotationally driven, and the supplied raw material chip 1 is supplied to the left side of the drawing. Mouth 1
It is supplied to the inside of the injection cylinder 7 via 3. At this time, the raw material chip 1 is transferred to the inside of the measuring cylinder 3 while being preheated by the preheating means 5 to the extent that the shape of the raw material chip 1 is maintained.

In the injection cylinder 7, the injection piston 8 stands by at a position lower than the raw material supply port 13, and a predetermined amount of the raw material chips 1 are deposited on the upper portion of the injection piston 8.
The supply amount of the raw material chip 1 to the injection cylinder 7 is controlled by the rotation time of the measuring screw 4 in the measuring cylinder 3. When the supply of the predetermined amount of the raw material chips 1 is completed, FIG.
As shown in FIG. 3, the rotation of the measuring screw 4 of the measuring cylinder 3 is completed, and at the same time, the injection piston 8 moves 0.1 to 0.5 m /
At a low speed of s, the temperature rises to the heating and melting section where the high speed heating means 9 is installed. The temperature of the raw material chip 1 becomes a predetermined molten state in a short time of 5 to 30 seconds, that is, the liquidus temperature ± 4.
Heat to 0 ° C. At this time, the temperature of the raw material chip 1 is indirectly measured by the thermocouple 14 attached to the injection cylinder 7, and when the temperature of the raw material chip 1 is lower than the predetermined temperature, the high-speed heating means is set to the predetermined temperature. Control 9

When the raw material chip 1 is melted, the injection piston 8 rises to the molds 11a and 11b side at a high speed of 0.5 to 5.0 m / s as shown in FIG. 4, and the molten metal is held in the mold cavity. 15 is injected and filled. After completion of injection, filling and holding pressure, and after a cooling time of about 1 to 10 seconds, the injection piston 8 immediately descends to its original position, that is, below the raw material supply port 13, and measurement of the next shot is started. It After the cooling time ends, as shown in FIG. 5, the mold is opened, the product is ejected, and the molded product is taken out. Then, the steps of metering, heating and melting, injection holding pressure, product removal, and metering shown in FIGS. 2 to 5 are repeated while the mold is closed and the vacuum is drawn again. Next, the molding cycle time will be described with reference to FIG.

When a large automobile part was molded with an injection molding apparatus having a mold clamping force of 650 tons and a maximum injection capacity of 10 kg to which the present invention was applied, the shot cycle was mold closing and weighing 10 seconds, heating and melting 18 seconds, injection holding pressure 1 Seconds, cooling 4
Second, the mold opening protrusion was 20 seconds, and the total was 53 seconds. Further, at this time, molding defects due to poor measurement did not occur.

On the other hand, the conventional mold clamping force of 650 ton
When a large automobile part was molded with the thixomolding injection molding machine, the shot cycle required 90 seconds or more due to the melting capacity of the molding machine. This is mold closing 5
Seconds, injection, holding pressure 2 seconds, metering 35 seconds, mold opening 5 seconds, protrusion 1 second, intermediate 42 seconds. This is because the thixomolding method has a low dissolving ability and takes an intermediate time for melting the raw material chips. Further, at this time, due to the unstable melting behavior, the raw material supply error was ± 2% or more, a measurement error occurred, and a filling defect, a molding defect such as a wrinkle occurred.

[0021]

According to the first and second aspects of the present invention,
The raw material chips are transferred while being preheated in the measuring cylinder to a temperature at which the chip shape can be maintained, and after the weighing is completed, the raw material chips are arranged in the vertical direction in the injection cylinder by a high-speed heating means by the injection piston. It moves up to the heating and melting section at a low speed, the material chips are heated at a high speed in the heating and melting section to a temperature at which it melts, and the melted material chips are moved up at a high speed and injected into the mold. By doing so, since it is possible to perform the weighing while maintaining the tip shape of the raw material tip, excessive rotation resistance does not occur during screw rotation, and accurate weighing can be performed. This has the effect of preventing defective measurement and improving molding quality.

Further, since the raw material chips are preheated and then melted by heating, the melting ability can be improved, so that the chips can be heated to the melting temperature in a short time and the molding time can be shortened. .

Further, it becomes possible to mold a large-sized and heavy-weight product which could not be conventionally molded without using a long injection molding machine, with a small-sized injection molding machine, and it is possible to reduce the apparatus and molding cost. . Further, by separating the preheating and the heating and melting, a high-speed heating means such as an induction heating means can be applied, so that the amount of heat required for melting can be provided in a short time with a minimum heating area.

Further, since the preheating means preheats the raw material chips in the measuring cylinder to a temperature at which the chip shape can be maintained, the screw rotation resistance does not occur during the measurement, and accurate measurement is performed. You can
Further, by preheating, there is an effect that even the melt injection means can melt and heat in a short time.

Furthermore, since the melting heating device is configured to heat the raw material chips to a temperature at which the raw material chips are in a molten state after completion of the raw material supply by the metering and transferring means, it is possible to effectively perform the melt injection in a short time.

Further, the injection piston moves at a low speed up to the high-speed heating means after the end of measurement, and moves at a high speed when the raw material chips are in a molten state and injected, so that the heating is efficiently performed. It can be melted and injected. Further, since the melting and heating means is a high-speed heating means such as an induction heating device, the raw material chips can be efficiently heated and melted, and the molding time can be shortened.

Further, since the injection molding device is a vertical injection molding device in which the injection cylinder is in the vertical direction, it is possible to prevent gas entrainment due to the ripple of the molten metal during the injection process.

According to the third aspect of the invention, in the case of a metal injection molding apparatus in which the raw material chip is a light alloy chip such as a magnesium alloy, it is particularly effective because the raw material chip needs to be heated at a high temperature. In addition, it is possible to prevent defective measurement and shorten the molding time.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional configuration diagram of a metal injection molding apparatus showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a state of a weighing process in the apparatus of FIG.

FIG. 3 is a configuration diagram showing a state of a heating and melting process in the apparatus of FIG.

FIG. 4 is a configuration diagram showing a state of an injection pressure holding step in the apparatus of FIG.

5 is a configuration diagram showing a state of a product taking-out and weighing process in the apparatus of FIG. 1. FIG.

FIG. 6 is a chart illustrating the injection molding process time.

FIG. 7 is a schematic sectional configuration diagram of a conventional metal injection molding apparatus.

[Explanation of symbols]

1 Raw material chips 2 injection molding equipment 3 measuring cylinder 4 Measuring screw 5 Preheating means 6 Measuring and transferring means 7 injection cylinder 8 injection pistons 9 High-speed heating means (melt heating means) 10 Melt injection means 11a, 11b mold 12 hoppers 13 Raw material supply port 14 thermocouple 15 Mold Cavity

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Claims (3)

(57) [Claims] 1. A mold (11a, 11b) in which a supplied raw material chip (1) is heated and melted in an injection cylinder (7).
In the injection molding method in which the raw material chips (1) are preheated in the measuring cylinder (3) to a temperature at which the chip shape can be maintained and transferred in the vertical direction after the measurement is completed. Injection cylinder (7)
Inside, the injection piston (8) moves the raw material chip (1) up to the heating and melting section at a low speed, and in the heating and melting section, the raw material chip (1) is rapidly heated to a temperature at which it is in a molten state and melted. An injection molding method in which the raw material chip (1) is moved up at a high speed and injected into the mold (11a, 11b). 2. In an injection molding apparatus (2) for heating and melting a supplied raw material chip (1) and injecting it into a mold (11a, 11b) for molding, the raw material chip (1) is The supplied measuring cylinder (3), the measuring screw (4) arranged in the measuring cylinder (3) for measuring and transferring the raw material chip (1), and the temperature at which the raw material chip (1) can maintain the chip shape. Metering transfer means (6) consisting of preheating means (5) for preheating up to, an injection cylinder (7) connected to the other end of the metering cylinder (3) and vertically arranged, and an injection cylinder (7)
An injection piston (8) which is disposed inside and reciprocates in the injection cylinder (7); and a melt heating means (9) which is attached to the injection cylinder (7) and melts and heats the raw material chip (1) at high speed. And a mold (11a, 11b) arranged above the injection cylinder (7).
The raw material chips (1) are metered and transferred by the metering and transferring means (6) while preheating so that the chip shape can be maintained, and are supplied to the melt injection means (10), and the injection piston (8) is ,
The weighed raw material chips (1) are moved at a low speed up to the heating and melting section where the high-speed heating means (9) is arranged, and the raw material chips (1) are heated at a high speed in the heating and melting section to a temperature at which they are in a molten state. An injection molding device in which a heated and melted raw material chip (1) is moved upward at a high speed and injected into a mold (11a, 11b). 3. The injection molding apparatus according to claim 2, wherein the raw material chip (1) is a light alloy chip such as a magnesium alloy.