JP3192301B2 - Metal injection molding equipment - 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 apparatus for a metal material by, for example, an in-line screw type injection molding machine.

[0002]

2. Description of the Related Art Conventionally, a molding technique for molding a metal material such as a magnesium alloy by an in-line screw type injection molding machine has been disclosed in Japanese Patent Publication No. Hei 3-504830. In this device, a pellet-shaped metal material is supplied from an hopper into an injection cylinder by the same process as injection molding of resin, and agitated with a screw while heating to form a semi-solid slurry. It is to be ejected one by one.

[0003] With this method, since all the steps are performed in one injection cylinder, material deterioration is suppressed, and the injection amount can be measured relatively accurately. The step of dissolving the magnesium alloy can be omitted. In addition, due to the difference in viscosity between the semi-solid slurry and the molten metal, defects such as entrainment of gas during filling are reduced as compared with ordinary die casting, and there is a possibility that molding with less gas defects can be performed.

[0004]

However, in the case of the above technique, unlike the injection molding of the resin, the screw does not retract due to the reaction of the pushing force of the resin itself, but the screw is forcibly retracted in accordance with the material supply speed. Therefore, there is a problem that voids such as air or gas are actually generated in the semi-solidified slurry and gas defects are likely to occur.

That is, as will be described later, the properties of the molten resin and the metal slurry in the injection cylinder in the in-line injection molding machine are different. In the case of a metal slurry, an internal pressure sufficient to push down the screw is not generated in the slurry itself. In addition, it is necessary to forcibly retract the screw in accordance with the slurry accumulation speed while limiting the material supply speed while leaving room for the material to enter the injection cylinder. However, matching between the material supply speed and the slurry retreat speed is difficult due to the state of the material (solid phase, liquid phase, etc.), the bulk density of the material, the variation in shape, and the variation in the material supply feeder. Is included.

[0006]

Means for Solving the Problems The present invention therein, the injection Shi
Metal material is supplied to the cylinder and converted into semi-solid slurry for injection molding.
In the injection molding apparatus designed to be molded,
Heating means for heating the cylinder, and a screw in the injection cylinder
Rotating means for rotating the shaft and screw shaft
Drive source for forward and backward drive and reaction force generated on screw shaft
Alternatively, a detecting means for detecting the retreat force and the detecting means
Move the screw shaft backward according to the signal
And control means for controlling the drive source.
Sign.

[0007]

[Function] Prevents voids in the slurry and provides high quality
Solidify the metal material in the injection cylinder to form
Screw while heating between the liquidus temperature and the liquidus temperature
And push the semi-solid slurry to the front of the injection cylinder.
And the pushing force is generated on the screw shaft.
The reaction force or retreat force is detected by the detecting means, and the reaction force
Retracts the screw shaft to keep the retraction force at the specified value.
I tried to make it. A change in the reaction force or the retreating force of the screw shaft after the introduction of the material means that the slurry has reached the head end. Then, after the reaction force or the retraction force reaches a predetermined value, if the screw shaft is retracted by applying feedback so as to maintain the predetermined value, the slurry can be filled with no gap from the head end.

[0008]

EXAMPLES Based on the accompanying drawings for an embodiment of the injection molding KatachiSo location of a metal of the present invention will be described. Figure 1 shows the injection molding equipment
Configuration Example view of location, FIG. 2 is a structural illustration of the control means.

The injection molding apparatus of the present invention is applied as an injection apparatus for molding a metal, such as a magnesium alloy or an aluminum alloy, for which it is desired to avoid contact with oxygen in the air by in-line injection molding. , For example, as shown in FIG.

That is, this apparatus comprises an injection machine 2 supported by a unit body 1, a mold 3 connected to the tip side of the injection machine 2, and a metal material supply chamber 4 for supplying a metal material to the injection machine 2. The ingot-shaped metal material is finely cut by a chopper 4a and supplied into an injection cylinder 6 to be semi-solid slurry and injected into the cavity 5 of the mold 3.

The injection machine 2 includes an injection cylinder 6 mounted on the unit body 1, a screw 7 provided in the cylinder 6, and a metering mechanism as a rotating means provided on the rear side of the screw 7. Unit 8, a pressure detecting unit 10 as a detecting unit connected to the end of the screw 7, a driving cylinder unit 11 as a driving unit for driving the screw 7 forward and backward, and a control unit 12 for driving and controlling the driving cylinder unit 11 ( 2).

A heater 13 is provided on the outer periphery of the injection cylinder 6 so that the metal heater can be heated to a predetermined temperature between the solidus temperature and the liquidus temperature of the metal material. ing. Incidentally, the predetermined temperature is, for example, 500 ° C. for a general magnesium alloy.
Set to ~ 600 ° C.

A shut valve 15 is provided at the tip of the injection cylinder 6 so that the nozzle hole of the injection cylinder 6 can be opened and closed by a drive cylinder unit 14.

Next, the screw 7 is provided with a screw thread portion 7a, a shaft portion 7b connected thereto and a spline portion 7c connected thereto in this order from the front end side.
Is provided with a check valve 9 at its tip.

The material supply port of the material supply chamber 4 faces near the base end of the screw portion 7a.

The weighing mechanism 8 includes a drive gear 17 attached to an output shaft of a drive motor 16 and a drive gear 1.
The driven gear 18 is meshed with the driven gear 7, and the spline portion of the driven gear 18 has a spline portion 7 c of the screw 7.
Is spline-fitted. Then, the screw 7 rotates around the axis by the operation of the drive motor 16.

As shown in FIG. 2, the pressure detecting section 10 includes a slide base 20 slidably engaged with a guide bar 1a of the unit main body 1, and a slide base 20 provided on the slide base 20 and provided with the screw 7. Radial bearings 21 and thrust bearings 22 that support the extending end and support radial and axial loads, and a detent that engages the end of the screw 7 and prevents rotation of the screw 7 as it moves in the axial direction. The pressure sensor 24 includes a member 23 and a pressure sensor 24 such as a load cell that detects the pressure of the screw 7 in the backward direction. The control unit 12 is connected to the pressure sensor 24.

The control means 12 controls the pressure detector 1
The drive cylinder unit 11 is also connected to the rear of the slide table 20. The piston rod 11a of the drive cylinder unit 11 is connected to the rear surface of the slide table 20.

Therefore, when the drive cylinder unit 11 is operated, the slide table 20 moves forward and backward along the guide bar 1a, and at the same time, the screw 7 moves forward and backward.

Next, the control means 12 will be described with reference to FIG.

The control means 12 comprises a computer 25 which receives an electric signal from the pressure sensor 24 via a transducer 26.
And a hydraulic circuit 27 for receiving an electric signal from the computer 25 via the converter 26.
Is connected to a port A on one side of the drive cylinder unit 11, and the other end is connected to a port B on the other side.

That is, on the circuit side connected to the port A,
A flow control valve 28 and a switching valve 29 operated by a signal from the computer 25 are provided. A pressure control valve 31 and an electromagnetic switching valve 32 are provided on a circuit side connected to the port B.

A circuit connected to both circuits is provided with a port electromagnetic switching valve 33. When the screw 7 is metered and retracted by such a control means, the pressure is reduced while adjusting the pressure on the port A side. The hydraulic pressure on the A side is rapidly increased. That is, the screw 7 is retracted while the pressure sensor 24 maintains a constant pressure, and the screw 7 is ejected when a predetermined slurry is measured.

The reason why the screw 7 is retracted in this way will be described.

First, the most basic screw specification used for resin injection molding is that the length of the screw thread portion 7a is about 20 times the screw pitch. The screw screw portion 7a generally has a supply area of about 1/2 from the material supply chamber 4 toward the front, and the remaining about 1/2 is a compression area and a measurement area. The depth of the groove becomes shallower toward the front in the compression region which is the middle portion, and almost the entire region is a shallow groove in the frontmost measurement region.

When the finely cut pellet-shaped resin material is supplied to the screw 7, the material which has advanced into the compression zone is pushed by the new pellet material sent from the rear, and at the same time, strong agitation and mixing action by the compression action. As a result, it changes to a solid state in the supply area, a rubber state in the compression area, and a liquid state in the metering area. During this time, the screw 7 is automatically retracted by the reaction of the strong extrusion pressure (for example, about several hundred kg / cm ² ) of the material itself.

By the way, such a process may be followed when forming a semi-solid slurry of a metal. However, the transformation of a metal material does not involve a rubber-like state such as a resin, and almost suddenly changes from a solid to a liquid. The extrusion pressure of the slurry material itself is very small, for example, about 10 kg / cm 2, because the transition takes place in a simple form.

Therefore, in the case of metal, the internal pressure cannot be increased even if the liquid phase having a low viscosity is stirred.

Even if the compression zone is provided, the metal pellets are not elastically deformed like resin but plastically deformed to hinder the advance of the material, and the mixed air is not eliminated as in the case of resin, but rather the temperature is reduced. Material contamination such as oxidation and diffusion proceeds in contact with the raised material. In other words, the effect of the compression area is small and the fault is rather large.

For this reason, for example, the ratio of the solid pellet existing portion to the length of the screw thread portion 7a is increased by the heating pattern of the injection cylinder 6, and the flow of the solid pellet is regarded as a flow of a substance having a high viscosity. Need to occur.

However, when the area of the solid pellets is lengthened in this way, the frictional resistance between the material and the inner wall of the cylinder increases, resulting in intense squeal noise, insufficient running torque, excessive thrust load, and heat generation. Things are possible.

[0032] These phenomena are expected to cause a problem that the material temperature cannot be controlled or the device is damaged.

As a countermeasure, semi-solid material may be supplied in advance instead of finely cut pellets, but the entire screw is clogged with a soft material, so that the extrusion pressure is also small.

For the above reasons, in the case of metal, the screw 7 is forcibly retracted without expecting to increase the internal pressure.

A molding method using the injection molding apparatus configured as described above will be described.

The heating heater 13 of the injection cylinder 6 is operated to supply the metal material pellets from the material supply chamber 4 in a state where the metal material is heated between the solidus temperature and the liquidus temperature of the metal material. Start weighing by rotating. At this time, the shut-off valve 15 in front of the injection cylinder 6 is
To close the nozzle hole.

Then, the solid-state dendrite of the metal material is divided by the stirring action and the heating action of the screw 7, and becomes a semi-solid slurry while being granulated, and is carried forward while being pushed by the subsequent slurry. When the screw 7 is conveyed to the shut-off valve 15 through the check valve 9, a reaction force is generated in the screw 7, and the pressure sensor 24 operates.

When the pressure sensor 24 reaches a predetermined value, the screw 7 is retracted by the control means 12. This retreat is controlled while giving feedback so that the value of the pressure sensor 24 retreats while maintaining a predetermined value.

By controlling as described above, it is possible to accumulate in the semi-solid slurry without generating voids.

When a predetermined amount of the slurry is measured by the measuring mechanism 8, the shut-off valve 15
Are opened, and the electromagnetic switching valves 29, 32, 3 of the control means 12 are opened.
By switching 3 etc., the screw 7 is advanced rapidly,
It is injected into the cavity 5 of the mold 3.

[0041]

As described above, according to the present invention, the injection serial
Injection molding by supplying metal material into a semi-solid slurry
In an injection molding machine designed to
Heating means for heating and the screw shuffle in the injection cylinder
Rotating means for rotating the screw and screw shaft
The drive source that moves and the reaction force or
Detecting means for detecting the retreating force, and detecting by the detecting means
Drive the screw shaft backward in response to a signal.
Since such a control means for controlling Dogen, the screw shaft is retracted by the reaction force or retraction force the screw shaft receives, not generated voids in the semi-solid slurry, it accumulates a stable slurry Can be done. Therefore, a high quality molded product can be obtained. Further, a large thrust load is not applied to the screw rotation drive system, and there is no problem such as damage to the device.

[Brief description of the drawings]

FIG. 1 is a configuration example diagram of the present apparatus.

FIG. 2 is a configuration example diagram of a control unit.

[Explanation of symbols]

Reference Signs List 6 : injection cylinder , 7 : screw , 8 : metering mechanism , 10 : pressure detector , 11 : cylinder unit as drive source , 12 : control means , 13: heating means,
16 ... rotating means, 24 ... pressure sensor .

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-258452 (JP, A) JP-A-4-270625 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 17/00 B22D 17/32

Claims (1)

(57) [Claims] 1. A supply metal material in the injection cylinder injection molding apparatus adapted to injection molding in the semi-solid slurry, a heating means for heating the pre-Symbol injection cylinder, rotates the screw shaft in the injection cylinder Rotating means, a driving source for driving the screw shaft forward and backward, detecting means for detecting a reaction force or a backward force generated on the screw shaft, and the driving source for moving the screw shaft backward in response to a signal detected by the detecting means. A metal injection molding apparatus, comprising: control means for controlling the temperature.