JP2002011559A - Injection molding method for metallic molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mold a metallic molding having thixotropic structure by melting, stirring, weighing and injecting a metallic material in a melding vessel by compositing the stirring means and the injecting means which are separately operated. SOLUTION: The injecting means 22, which is provided with a cylindrical weighing chamber 17 having a prescribed length communicated with a nozzle hole at the tip part and the stirring means 21 so as to be freely rotated in the inner part and in which the tip part is formed into an injecting plunger 39 at the center part of the stirring means 21, is inserted so as to be freely advanced/retreated, and granular metallic material is supplied into the melting vessel 11 in which the injecting plunger 30 is inserted freely slidably into the weighing chamber 17. The metallic material is heated and melted by the external heat. The molten metallic material is uniformized by the stirring means 21 and stored into the melting vessel. A part of the molten metallic material is injection-filled into a metallic mold at the temperature between than the solidus temperature or above and the liquidus temperature or below by the injecting means 22. Thus, the metallic molding having thixotropic structure can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dissolving a low-melting metal material such as zinc, magnesium or an alloy thereof and injection-molding it into a metal molded product.

[0002]

Die casting is used for casting non-ferrous metal having a low melting point. However, die casting requires a melting furnace for completely melting a metal material, and hot water is drawn from the melting furnace or a plunger is used. It is extruded for casting. Therefore, regardless of the melting furnace, similar to the case of the plastic material, the granular metal material supplied from the rear part of the heating cylinder is melted while being transferred to the front of the heating cylinder by screw rotation and melted. After accumulating and weighing in a chamber, a screw is being advanced to perform injection filling of a die from a nozzle at the tip of a heating cylinder.

[0003] Problems to be solved when such injection molding is applied to a metal material include difficulty in dissolving and transferring the metal material due to rotation of the screw, and instability of measurement. Most of the melting of the plastic material is caused by shear heat, so that the screw is formed to have a larger diameter toward the tip, and the screw groove serving as a gap for the material is formed relatively shallow. However, in the case of molten plastic, since there is a difference in the friction coefficient at the boundary surface of the inner wall of the heating cylinder, even if the flow gap is formed narrow, the transfer forward by the screw rotation is smoothly performed.

On the other hand, a metal material completely dissolved in a liquid phase state has a viscosity that is incomparably lower than that of a plastic material, so that there is almost no difference in friction coefficient between the two interfaces. Transfer force due to screw rotation unlike in the case of molten plastic hardly occurs.
In the low-viscosity liquid phase, the pressure does not increase enough to push the screw back.Therefore, it is difficult for the screw to recede due to the material pressure. Quantification involves technical difficulties.

Therefore, injection molding is performed in a semi-molten state by limiting the melting temperature to a temperature not lower than the solidus temperature and not higher than the liquidus temperature without completely melting the metal material. In the molten metal in the above temperature range, its structure is considered to be in a semi-molten state (thixotropic property). In this state, flow resistance occurs in the molten metal, and it is possible to measure by transport and retreat by screw rotation. Become. Therefore, the molding of metal molded articles by injection molding up to now has been based on the adoption of such a method.

However, the molding method simply applies the plastic material injection molding means as it is.
Also, unlike plastics, metals have good thermal conductivity and thus are easy to cool. For example, there is a difficulty in maintaining the temperature of the molten metal in the heating cylinder. Also in the molding of the metal material, the heating cylinder is heated by the outer band heater to maintain the set temperature. However, there is no heating means on the screw side, and heat is easily radiated from the rear end. For this reason, temperature unevenness is likely to occur in the molten metal in the screw groove, and to prevent this by stirring, rotating the screw is because the screw itself also serves as a transfer member of the molten metal material, It is considered impossible because of the oversupply of materials.

The present invention has been conceived in order to solve the above-mentioned problem in the case of injection molding a metal material in a semi-molten state, and aims at melting and transporting which have been indispensable so far. Without using a screw having three functions of injection, it is possible to stir the molten metal in the melting vessel by combining the separately operating stirring means and injection means, thereby setting the melting temperature of the metal material. It is an object of the present invention to provide a new injection molding method capable of molding a metal molded article having a thixotropic property while maintaining the temperature in a temperature range.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a measuring chamber having a required length communicating with a nozzle port at a distal end thereof, a rotatable stirring device provided therein, and a central portion of the stirring device. The injection means, the tip of which is formed in the injection plunger, is inserted through the injection plunger so as to be able to advance and retreat, and the metallic metal material is continuously or intermittently inserted into a cylindrical melting vessel in which the injection plunger is slidably fitted in the measuring chamber. Supply, the metal material is heated and melted to a temperature not lower than the liquidus temperature by external heat, and is homogenized by the stirring means and accumulated in the melting vessel, and a part of the molten metal material is supplied to the injection plunger. During the process from retreating to the weighing chamber and injection-filling the mold,
In other words, it is cooled to a temperature equal to or higher than the solidus temperature and equal to or lower than the liquidus temperature, injection-filled into a mold, and molded into a metal molded product having a thixotropic property.

Further, according to the present invention, a measuring chamber having a required length communicating with the nozzle port is provided at the tip end, and a stirring means is rotatably provided therein, and the tip is formed at the center of the stirring means at an injection plunger. The injection means is slidably inserted into the measuring chamber, and the granular metal material is continuously or intermittently supplied to a cylindrical melting vessel in which the injection plunger is slidably fitted in the measuring chamber. The molten metal material is heated and melted to a temperature not lower than the solidus temperature and equal to or lower than the liquidus temperature by heat. A part of the molten metal material is fed into the measuring chamber by retreating the injection plunger, and after the weighing, the injection plunger is advanced and injected into the mold while maintaining the semi-molten state to form a metal having a thixotropic property. Goods Molding, it is that.

[0010]

FIG. 1 shows an embodiment of a molding machine capable of performing an injection molding method for a metal molded product according to the present invention.

In FIG. 1, reference numeral 1 denotes an injection mechanism, 2 denotes a mold clamping mechanism, both of which are installed on the upper surface of a machine base 4; The injection mechanism 1 is installed on the gantry 5 so that the nozzle side of the injection mechanism 1 is inclined downward with respect to the mold clamping mechanism 2.

The injection mechanism 1 has a cylindrical melting tube 11 serving as a melting container for a metal material, a stirring and injection means described later in the inside thereof, and an injection mechanism provided at a rear end of the melting tube 11 at intervals. Cylinder 12 and supporting leg 1 below rear end of melting cylinder 11
3 comprises an electric motor 14 for stirring and a delivery device 15 for supplying a granular metal material into the melting cylinder. The delivery device 15 includes a horizontal cylinder 15a and an internal screw shaft 15c rotated by an electric motor 15b provided at the end of the cylinder. Although not shown in the drawing, the heater has a structure in which a heater for preheating the material can be mounted around the cylinder as necessary.

The melting tube 11 has a nozzle member 10 at its tip.
And a band heater 16 on the outer periphery. The inside of the distal end of the melting cylinder 11 communicating with the nozzle hole of the nozzle member 10 is formed in a cylindrical measuring chamber 17 having a required length reduced to a smaller diameter than the inner diameter of the melting cylinder 11. In the illustrated example, the nozzle member 10 attached to the tip of the melting tube by the tip member 18 is used.
The inside of the rear portion is reduced in diameter to be smaller than the inner diameter of the melting cylinder, and the rear portion is defined as a measuring chamber 17 communicating with the inside of the melting cylinder.
Alternatively, a structure in which a nozzle tip is attached to the tip member 18 may be used.

A supply port 19 is opened in the middle upper part of the dissolving cylinder 11 having such a measuring chamber 17 at its tip.
The delivery device 15 is connected to the supply port 19 through a pipe 20. The rear end of the dissolving cylinder 11 is in an open state, and a stirring member 21 and an injection member 22 constituting the stirring and injection means are provided therein.

The agitating member 21 comprises a rotary shaft having a plurality of agitating blades 24, 24 intermittently formed on the outer periphery of the distal end portion of a hollow shaft portion 23 having a through hole in the center. These stirring blades 24, 24 have an outer diameter substantially equal to the inner diameter of the melting cylinder 11. Around the shaft portion of the hollow shaft portion 23 behind the stirring blade 24, a partitioning flange 25 serving also as a guide and in contact with the inner peripheral surface of the melting cylinder 11 is integrally formed.

A pulley 26 is fixed to an end of the hollow shaft portion 23 projecting from an opening end of the melting cylinder 11, and extends between the pulley 26 and a pulley 27 at a drive shaft end of the electric motor 14. A timing belt 28 is hung and the electric motor 14 rotates the stirring member 21 in one direction or reciprocates in the melting cylinder so that the molten metal can be stirred by the stirring blades 24, 24. It is.

The injection member 22 is inserted into the through-hole of the hollow shaft portion 23, and is slidably provided at the center of the stirring member 21;
1 and an injection plunger 30 fitted in the measuring chamber 17. The injection plunger 30 moves forward and backward without exiting the measuring chamber by the injection rod 29. A ring 29a is formed in multiple stages around the outer periphery of the injection rod 29 above the partitioning flange 25, the ring 29a also serving as a rod guide and for preventing backflow of molten metal that has permeated the clearance.

The injection plunger 30 has an outer diameter that can be inserted into the measuring chamber 17 with a clearance for sliding, and has a seal ring 31 around its outer periphery. The seal ring 31 is made of a heat-resistant piston ring made of special steel or the like. Although the details of the seal ring 31 are omitted in the figure, the diameter of the seal ring 31 is reduced at the time of negative pressure on the measuring chamber side due to the retraction of the plunger, and the clearance is expanded to smoothly transfer the molten metal material into the measuring chamber. At the time of injection, a required gap is inserted into the annular groove around the outside of the plunger between the groove bottom and the groove wall so as to expand by the material pressure on the measuring chamber side and prevent the backflow of the molten metal from the clearance. It is.

The injection cylinder 12 has an integral support leg 32 below the front end of the cylinder, and the injection cylinder 12 is integrally connected to the melting cylinder 11 at intervals with tie bars 33 disposed on both sides. The piston 34 is connected to the rear end of the injection rod 29 projecting from the rear end of the hollow shaft portion 23, and moves the injection rod 29 forward and backward together with the injection plunger 30 at the front end.

The injection cylinder 12 and the melting cylinder 11 are connected to the supporting legs 13 projecting from both lower sides thereof.
32 are inserted through support shafts 40, 40 juxtaposed on both sides of the inclined upper surface of the gantry 5, and the nozzle member 10 is attached downward on the lower side. The injection mechanism 1 is installed.

On both sides of the injection mechanism 1, a nozzle touch device 44 is provided by a hydraulic cylinder 42 and a long rod 43.
However, while the tip end of the rod 43 is rotatably mounted on the bearing members 46 on both sides of the nozzle touch block 45 erected at the center of the tip end of the pedestal 4, the hydraulic cylinder 42 is connected to the melting cylinder rear end and the injection cylinder front end. And the rear end of the cylinder is rotatably fixed to the injection cylinder. The nozzle touch device 44 also functions as a retreat device when repairing or maintaining the injection mechanism 1.

The pedestal 5 has an upper surface formed on an inwardly inclined surface having an angle of about 45 °.
Are attached at both ends with members 41, 41. The gantry 5 is a gate-shaped seat 6 installed on the rear end of the pedestal 4.
Although not shown in the drawing, the nozzle member 47 is mounted so as to be freely rotatable, extends from the center of the receiving seat 6 to the nozzle touch block 45, and is horizontally provided with a member 52 on the front surface of the nozzle touch block 45. Nozzle touch device 48 is provided.

The hydraulic cylinder 49 of the nozzle touch device 48 is provided with a receiving member 50 at the center of the pedestal 4 installed on the machine base 3.
The rod member 51 fixed to the base member and connected to an internal piston rod (not shown) has its tip connected to the nozzle touch block 45, and the pedestal 4 moves the pedestal 5 by moving the rod member 51 forward and backward. The nozzle member 47 moves forward and backward together with the injection mechanism 1 on the upper surface so that the nozzle member 47 can perform nozzle touch on the mold 7.

The upper inside of the nozzle touch block 45 is formed on an inclined rear surface located at right angles to the axis of the nozzle member 10 of the injection mechanism 1, and a nozzle touch gate is opened on the inclined rear surface. Inside the nozzle touch block 45, a hot runner 53 that connects the nozzle member 47 and the nozzle member 10 of the injection mechanism 1 is formed to be bent, so that the injection mechanism 1 is installed at an angle to the mold clamping mechanism 2. Even if it does, the nozzle touch is performed without a gap, and leakage of the molten metal during injection filling is prevented.

In order to form a metal molded product, for example, a molded product made of magnesium (AZ91D) by the first injection molding method of the present invention using the molding apparatus having the above-described structure, first, the melting cylinder 11 must be formed on the outer peripheral band. Heating is performed by the heater 16 to a set temperature equal to or higher than the liquidus temperature (620 ° to 680 ° C), and the inside is heated to a higher temperature than the melting temperature. Further, the nozzle touch block 45 and the nozzle member 47 also have a solidus temperature (470 ° C.) or higher and a liquidus temperature (595 ° C.) or lower while the molten metal material passes through the runner and is injected and filled into the mold 7. Although not shown in the drawing, the temperature is heated by an external heater so as to reach the temperature. At this time, the space in the melting cylinder is set to an inert gas atmosphere. The supply of this inert gas is
Although not shown in the figure, for example, a supply pipe of an inert gas cylinder can be connected to the pipe 20.

Next, the hollow shaft 2 is driven by the electric motor 14.
3 is rotated at a set speed to be in a stirring state. Therefore, using the magnesium as a metal material, the delivery device 15 is used.
From the supply port 19 into the melting cylinder 11. Since the melting tube 11 is inclined downward, the metal material is immediately melted at the portions of the stirring blades 24 and 24 rotating together with the hollow shaft portion 23 to become hot water. Further, the continuously supplied metal material falls into the hot water stored therein, is dissolved by the heat of the hot water, and is mixed into the hot water by the stirring blades 24, 24. As a result, the molten metal material is melted in a very short time and the molten metal material is made uniform.

When the injection plunger 30 is at the forward position, the molten metal material is stored in the front portion of the melting cylinder 11 as it is. The storage amount is about 10 shots,
If one shot of material is supplied for each molding, continuous molding can be performed without any trouble. When a predetermined amount of the molten metal material has been stored, the injection plunger 30 is moved backward. This retreat movement is limited to a range where the seal ring 31 stays in the measuring chamber 17, and a part of the molten metal material stored by the retreat movement flows into the measuring chamber 17.

The flow of the molten metal material into the measuring chamber 17 is caused by the negative pressure generated by the backward movement of the injection plunger 30 in the measuring chamber. This is because the molten metal material of the previous injection is cooled and solidified at the nozzle opening of the nozzle member 47 and remains as a cold plug, and the nozzle side of the measuring chamber 17 is closed, so that the inflow from the nozzle opening is prevented. When a retreating force is applied to the injection plunger 30 in the forward limit in such a state, the measuring chamber 17 that expands with the retreat moves to a negative pressure.

The negative pressure reduces the diameter of the seal ring 31 of the injection plunger 30, and the suction action of the negative pressure causes the molten metal material to flow from the clearance around the seal ring into the expanding measuring chamber 17 and into the chamber. It will fill up. As a result, a large negative pressure that makes it difficult to forcibly retract the injection plunger 30 is not generated in the measuring chamber 17, and the material is measured by the smooth retreat of the injection plunger 30. Therefore, by setting the metering completion position in anticipation of the reverse flow rate due to the forward movement of the injection plunger 30 at the time of injection, and subsequently switching the process to injection filling and moving the injection plunger 30 forward to the forward limit, the set amount is always maintained. Injection filling of the molten metal material into the mold 7 becomes possible.

Since the stirring member 21 and the injection member 22 are separate from each other in the melting cylinder even during the injection and filling during the material measurement, the molten metal material is stirred by the rotation of the stirring blades 24, 24. Is continuously performed, whereby even if a new metal material is supplied to the melting cylinder 11 continuously or intermittently, the molten metal material in the melting cylinder can be made uniform.

Further, since the injection member 22 does not rotate for the purpose of melting the metal material, it is not necessary to manufacture the injection rod to have a large diameter as in the case of the conventional screw in consideration of the rotational torque. Since the member 21 also does not melt by shearing heat, a large gap can be formed between the inner wall surface of the melting cylinder and the outer surface of the hollow shaft portion, which is considered difficult when a screw is employed. It becomes easy to store the molten metal material for several shots, and the effect of maintaining the temperature of the molten metal material is further improved.

The weighed molten metal material is pressurized by the forward movement of the injection plunger 30 to repel the cold plug closing the nozzle port of the nozzle member 47, and from the nozzle touch block 45 into the nozzle member 47. After passing through the hot runner 53, the cavity of the mold 7 is injected and filled.

In the process from the measurement to the injection, the molten metal material having a temperature higher than the liquidus temperature is heated by the nozzle touch block 45 and the nozzle member 47 to a temperature higher than the solidus temperature and lower than the liquidus temperature. Therefore, it is cooled to a semi-molten state while being injected and filled in the mold 7 through the hot runner 53, and a certain degree of agitation is caused by the turbulence of the flow due to the flow resistance. The magnesium molded product thus obtained is a product having a thixotropic property in composition.

The second injection molding method according to the present invention is characterized in that the melting cylinder 11, the nozzle touch block 45, the nozzle member 4
7 is set so that the temperature of the molten metal material is equal to or higher than the solidus temperature and equal to or lower than the liquidus temperature. A thixotropic state is obtained by agitation by the member 21, and weighing by movement of the injection plunger 30 and injection filling into the mold 7 are performed while maintaining the state. Magnesium molded products formed by this,
The tissue becomes a thixotropic property product.

In both of the first and second injection molding methods, since the stirring member 21 and the injection member 22 are separate from each other inside the melting tube 11, regardless of the measuring and injection steps, Stirring of the molten metal material by the rotation of the stirring blades 24, 24 is continuously performed, whereby even if a new metal material is continuously or intermittently supplied to the melting cylinder 11, the molten metal in the melting cylinder is The material can be made uniform.

Further, since the injection member 22 does not rotate for the purpose of melting the metal material, it is not necessary to manufacture the injection rod to have a large diameter unlike the conventional screw in consideration of the rotation torque, and the agitation is not required. Since the member 21 also does not melt by shearing heat, a large gap can be formed between the inner wall surface of the melting cylinder and the outer surface of the hollow shaft portion, which is considered difficult when a screw is employed. The molten metal material for several shots can be stored easily, and the temperature unevenness of the semi-molten metal material is eliminated, and the injection molding of thixotropy-like metal molded products with higher molding accuracy than previous molding methods is facilitated. Can be done.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional side view of a molding machine which enables an injection molding method of a metal molded product according to the present invention.

[FIG. 2] FIG.

FIG. 3 is a vertical sectional side view of a distal end portion of a melting cylinder when the injection plunger is retracted.

FIG. 4 is a longitudinal sectional side view of a distal end portion of a melting cylinder when an injection plunger is advanced.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection mechanism 2 Mold clamping mechanism 10 Nozzle member 11 Melting cylinder 12 Injection cylinder 15 Metal material delivery device 17 Metering chamber 21 Stirring member 22 Injection member 23 Hollow shaft part 24 Stirrer blade 29 Injection rod 30 Injection plunger 31 Seal ring 45 Nozzle touch Block 47 Nozzle member

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Hayashi 2110 Nanjo, Najo, Hanashi-gun, Nagano Prefecture Nissei Resin Industry Co., Ltd. Resin Industries Co., Ltd. F term (reference) 4F206 AA49 AR06 JA07 JD04 JL02 JM01 JN03

Claims (2)

[Claims] 1. An injection means having a measuring chamber of a required length communicating with a nozzle port at a front end thereof, a stirring means rotatably provided therein, and a front end formed in an injection plunger at the center of the stirring means. The metal material is continuously or intermittently supplied to a cylindrical melting vessel in which the injection plunger is slidably fitted in a measuring chamber, and the metal material is supplied by external heat. While being heated and melted to a temperature equal to or higher than the phase line temperature, it is homogenized by the stirring means and accumulated in the melting vessel, and a part of the molten metal material is transferred from the injection plunger to the measuring chamber by retreating to the mold. In the process up to the injection filling, the metal is characterized by being cooled to a temperature not lower than the solidus temperature but not higher than the liquidus temperature, injection-filled into a mold, and formed into a metal molded product having a thixotropic property. Injection molding method for molded products. 2. Injection means having a measuring chamber of a required length communicating with the nozzle port at the tip end, rotatably provided with stirring means inside, and having a tip end formed in an injection plunger at the center of the stirring means. The injection plunger is slidably inserted thereinto, a granular metal material is continuously or intermittently supplied to a cylindrical melting vessel in which the injection plunger is slidably fitted in a measuring chamber, and the metal material is solidified by external heat. The molten metal material is heated and melted to a temperature not lower than the liquidus temperature and not lower than the liquidus temperature, and the molten metal material is accumulated in the melting vessel while being stirred and maintained in a semi-molten state (thixotropic form) by the stirring means. A part of the material is fed into the measuring chamber by retreating the injection plunger and injected into the mold by advancing the injection plunger while maintaining the semi-molten state even after weighing, forming a metal molded product with a thixotropic property To do Characteristic injection molding method for metal molded products.