JP2000141006A - Molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the stable production of a good-quality product by control ling the temperature of a nozzle to a value for forming an optimum plug when molten metal is injected and filled up into a die from the nozzle in molding. SOLUTION: In the molding method having a system, with which after injecting and filling up the molten metal 30 in a cylinder 16 into the die 40 from the nozzle 18, the temperature of the nozzle 18 is controlled to form the plug 32 of the solidified metal in the inner part, and at the time of following injection, the plug 32 is blown into the die 40 from the nozzle 18 with the injection pressure applied in the cylinder, the pressure data in taking off the plug 32 from the nozzle 18 in the injection pressure, are detected, and the feedback of these data is executed into the temp. control of the nozzle 18 to control the temp. of the nozzle 8 so as to become the value for forming the optimum plug.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method for molding a predetermined product by injecting a molten metal from a nozzle into a mold.

[0002]

2. Description of the Related Art Conventionally, there is thixomolding as one of such molding techniques. This is a technique for forming a high quality product by filling a mold with a semi-molten metal mixed and stirred with a liquid in a laminar flow.
This thixomolding is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-313164. As is clear from this technique, semi-molten metal is injected into a mold from a nozzle of a container. The temperature of the container and the nozzle is controlled by heating with a heater so that the molten metal inside does not solidify.

By the way, in order to prevent the molten metal filled in the mold from solidifying to a certain extent and to prevent the molten metal from leaking from the nozzle when the nozzle is separated from the mold, the temperature at the tip of the nozzle is lowered to prevent the molten metal from leaking from the nozzle. There is a technology for forming a plug of solidified metal. This plug is blown out of the nozzle by the pressure at the time of filling the molten metal into the mold at the time of the next molding, and is pulled out. However, the solidification state of the plug changes according to conditions such as the mold temperature and the outside air temperature.In general, the operator judges the solidification state from the sound of the plug coming out or the appearance of the product, and based on that, the nozzle temperature is determined. Has been adjusted.

[0004]

It is difficult to properly control the temperature by adjusting the nozzle temperature according to the operator's judgment. If the temperature of the nozzle is too high, the plug will come off at a low pressure due to the insufficient solidification of the plug. As a result, a high pressure acts in the mold, and the molten metal blows out from the mating surface of the mold, and air is drawn into the cavity. Conversely, if the temperature of the nozzle is too low, solidification of the plug proceeds excessively, and the plug does not come off unless the pressure is high. This causes a problem that the plug is poorly removed or the plug is blown off at an extremely high pressure and sticks in the mold. For these reasons, product quality and productivity are impaired.

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problem. An object of the present invention is to set the temperature of the nozzle to a value at which an optimum plug is formed when the molten metal is injected into the mold from a nozzle in molding. By controlling to
It is to enable stable production of high quality products.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and the invention according to claim 1 is characterized in that molten metal in a cylinder is injected from a nozzle into a mold and filled, and then the nozzle is filled with molten metal. A molding method of a type in which a plug of solidified metal is formed therein by controlling the temperature and the plug is blown out of a mold from a nozzle by an injection pressure applied to a cylinder at the time of the next injection. Is characterized by detecting pressure data at the time of exiting from the nozzle and feeding back this data to nozzle temperature control to control the temperature of the nozzle to a value at which an optimum plug is formed.

As described above, in molding, by controlling the temperature of the nozzle by feeding back pressure data when the plug comes out of the nozzle, a plug in an optimum solidified state is always formed. Therefore, the problem that the plug easily comes off at a low pressure or causes a draw-out failure is solved, and a high-quality product can be stably produced.

According to a second aspect of the invention, there is provided the molding method according to the first aspect, wherein the molten metal is a magnesium alloy. Magnesium has high reactivity in a molten state, and it is dangerous that the magnesium leaks from the nozzle. However, such a danger is eliminated by always forming the plug into an optimally solidified state.

[0009]

Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram showing an outline of a thixomolding device. As shown in this drawing, the high-speed shot system 10 includes a cylinder 16 having a nozzle 18 at the tip.
Are provided integrally. The screw 14 of the shot system 10 is located inside the cylinder 16, and the screw 14 is driven by the rotary drive 12 of the shot system 10.

The hopper 2 is provided inside the cylinder 16.
From 0, the material (magnesium alloy) of the injection molded product is supplied through the feeder 22. This material is heated to a predetermined temperature (approximately 58 ° C.) by controlling the temperature of a heater 24 provided on the outer peripheral portion of the cylinder 16.
0 ° C.) and is maintained in a semi-molten state in which a solid and a liquid are mixed. Such a semi-molten molten metal 3
0 is stored in the storage section 17 near the nozzle 18 inside the cylinder 16 and is injected from the nozzle 18 into the mold 40 at a predetermined injection pressure by driving the screw 14.

FIG. 2 shows the nozzle 18 of the cylinder 16 and the mold 4.
It is sectional drawing which expanded and represented the relationship with 0. As shown in this drawing, at the time of molding, the tip of the nozzle 18 is in close contact with the runner 42 of the mold 40.
The runner 42 changes its direction from the horizontal direction to the vertical direction, and communicates with the product forming cavity 48 via the throttle 46. As is well known, the throttle 46 is for preventing slag or the like mixed in the molten metal 30 from entering the cavity 48.

The nozzle 18 is connected to the heater 2
The temperature is controlled by a dedicated heater (not shown) different from the heater 4. That is, by lowering the temperature of the nozzle 18 to a predetermined value (for example, about 520 ° C.)
The molten metal 30 located inside the nozzle 18 solidifies to a certain extent to form the plug 32. This plug 3
Reference numeral 2 is for preventing the molten metal 30 in the cylinder 16 from leaking outside from the nozzle 18 when the nozzle 18 is separated from the mold 40.

Next, the molding will be described. First, by driving the screw 14 in the shot system 10, the molten metal 30 in the cylinder 16 is injected from the nozzle 18 into the mold 40 at a predetermined injection pressure. Thus, the molten metal 30 is filled into the cavity 48 through the runner 42 and the throttle 46. At this time, the molten metal 30 in the cylinder 16 is
Is heated and held until just before the mold 40,
The cavity 48 can be filled with the molten metal 30 at a lower temperature compared to a generally known die casting system.

After filling the cavity 48 with the molten metal 30, the plug 32 is formed by controlling the temperature of the nozzle 18 as described above, and the inside of the mold 40 (particularly the
When the molten metal 30 (inside 2) solidifies so as not to flow out, the cylinder 16 is separated from the mold 40. At this time,
The plug 32 prevents the molten metal 30 in the cylinder 16 from leaking out of the nozzle 18. Then, the plug 32 is blown out from the nozzle 18 by the injection pressure when the molten metal 30 is injected into another mold 40 during the next molding. Nozzle 1
The plug 32 blown off from the plug 8 is received by a plug catcher 44 formed at the back of the runner 42 as shown in FIG. 2, and care is taken not to flow toward the cavity 48.

The solidification state of the plug 32 depends on the temperature of the nozzle 18, and the pressure at which the plug 32 comes out of the nozzle 18 differs depending on the solidification state. Therefore, in the present embodiment, the molten metal 30
The pressure change in the cylinder 16 when injecting
This data is fed back to the temperature control of the nozzle 18. That is, the detection result is shown in FIG. 3, and FIG. 3A shows data when the plug 32 is formed under optimal conditions. So this figure 3
By controlling the temperature of the nozzle 18 based on the data of (A), the plug 32 in an optimally solidified state can always be formed.

3 (A) to 3 (C), P1 indicates the pressure holding in the cylinder 16, P2 indicates the injection pressure, and P3 indicates the pressure at which the plug 32 is released. FIG. 3B shows the nozzle 18.
3C shows data when the temperature of the nozzle 18 is too low, and FIG. 3C shows data when the temperature of the nozzle 18 is too high. In the case of FIG. 3B where the temperature of the nozzle 18 is too low, the solidification of the plug 32 progresses too much, so that the release pressure P3 is high and the pressure holding time is long, so that the plug 32 cannot be removed properly. Invite. Further, the holding time of the holding pressure P1 is short, so that the molten metal 30
May be insufficiently filled. On the other hand, in the case of FIG. 3C where the temperature of the nozzle 18 is too high, the solidification of the plug 32 is not sufficiently promoted, and as a result, the release pressure P3 is low. In this case, a high pressure acts in the mold 40, and the molten metal 30 blows out from the mating surface of the mold, thereby causing burrs on the product and entrapping air into the cavity 48. .

As described above, in the present embodiment, the plug 32
The pressure data at the time when the liquid exits from the nozzle 18 is
By feeding back to the temperature control of the mold 8, the mold 4
A plug in an optimally solidified state can always be formed in accordance with a change in conditions such as a temperature of 0 or an outside air temperature. Therefore, the troubles that occur in the cases of FIGS. 3B and 3C are eliminated, and a high-quality product can be stably produced. In addition, since the molten metal 30 can be prevented from leaking from the nozzle 18 by the plug 32 which is always in an optimally solidified state, even if the molten metal 30 is a material having a high reactivity in a molten state such as a magnesium alloy, the leakage is prevented. The danger caused by dispensing is eliminated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an outline of a thixomolding device.

FIG. 2 is an enlarged sectional view showing a relationship between a nozzle 8 and a mold.

FIG. 3 is a graph showing detection data of a pressure change when a molten metal is injected into a mold.

[Explanation of symbols]

 16 Cylinder 18 Nozzle 30 Molten metal 32 Plug 40 Mold

Claims (2)

[Claims] After the molten metal in a cylinder is injected into a mold from a nozzle and filled, a plug of solidified metal is formed inside the nozzle by controlling the temperature of the nozzle, and the plug is added into the cylinder at the next injection. A molding method in which a plug is blown out of a nozzle from a nozzle by an injection pressure, wherein pressure data of the injection pressure when the plug comes out of the nozzle is detected, and this data is fed back to temperature control of the nozzle to feed the nozzle. A molding method characterized by controlling the temperature to a value at which an optimum plug is formed. 2. The molding method according to claim 1, wherein the molten metal is a magnesium alloy.