KR101771120B1

KR101771120B1 - Screw for Thixomolding

Info

Publication number: KR101771120B1
Application number: KR1020150042397A
Authority: KR
Inventors: 이장희
Original assignee: 이장희
Priority date: 2015-03-26
Filing date: 2015-03-26
Publication date: 2017-08-24
Also published as: KR20160115199A

Abstract

The present invention reduces the volume of a flight's bore as it goes to a compression unit and a metering unit where a material into which a chip-like material is introduced in a hopper is melted and converted into a resin in the hopper, so that bubbles do not remain in the molten resin, The semi-molten molding screw according to the present invention is installed in a barrel into which a chip-shaped material is introduced by means of a driver and rotates from a rear side to a front side A screw shaft having a shape increasing in diameter; And a flight formed on the outer surface of the screw shaft so as to be spirally formed along the axial direction to transfer the material introduced through the rear portion of the barrel to a mold provided in front of the barrel, wherein the flight increases in thickness from the rear to the front .

Description

Screw for Thixomolding [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a screw for a molding apparatus, and more particularly to a semi-molten molding screw which rotates in a cylinder of a semi-molten molding machine and feeds a material to a cavity of a mold.

Thixomolding is a molding process that has emerged as a next-generation technology to replace conventional die casting and plastic injection molding. Conventional plastic injection molding has a disadvantage in that it is insufficient in rigidity to form a very precise NET Shape, and EMI (Electro Magnetic Interference) shielding must be separately provided. In addition, die casting has a disadvantage in that it is difficult to process, has a long process time, has a large infiltration of impurities, and has a defective structure inside the molded product.

Semi-melt molding is not a method in which ingot, which is a form of large metal, is melted in a die casting machine and melted in a liquid state, but a chip-type material having anti-oxidation coating treatment is put into a molding machine, Since it is formed in the intermediate thixotropic state, the molding speed is fast, the internal structure is dense, the impurities are less and the performance is superior to die casting.

Such a semi-molten molding has a drawback in that it is required to periodically replace the nozzle, the screw, and the cylinder due to the abrasion of the nozzle, the screw and the cylinder because the screw in the cylinder rotates while the chip is transferred at a high temperature.

A screw used in a semi-molten molding machine usually has a supply part for supplying a material to be introduced from the hopper, a compression part for transferring the material transferred from the supply part by the heat of the front end and the heater row, a molten resin transferred from the compression part, And a metering section for injecting the gas into the barrel head.

However, in the conventional injection screw, the flight efficiency of the material is lowered due to the constant width of the flight, the volume of the molten resin is reduced, and bubbles are generated, causing defective molding products. That is, since the chip-shaped material is injected into the supply portion of the screw, the volume of the flight's bone must be large, and the volume of the flight is reduced after the material is melted and converted into resin. Since the volume of the flight bone is almost constant, the boss remains in the crest of the flight in the compression section and the metering section, resulting in product failure.

In addition, since the conventional injection screw is provided with a heater only for the barrel to melt the material, a temperature difference occurs between the surface of the barrel and the surface of the screw, and a portion close to the barrel is melted. The phase change that is achieved is different in each part. That is, since the temperature between the barrel and the screw is not uniform, uneven phase change of the resin material as described above is caused.

Also, since the amount of heat applied from the rear portion of the barrel to the head portion is the same, the supply portion and the compression portion, which require a relatively large amount of heat, fail to supply sufficient heat.

Registration No. 10-0550232 (2006.02.01.) Registration No. 10-0827251 (2008.04.28.) Published Patent No. 10-2009-0094341 (September 4, 2009)

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to reduce the volume of a flight's bore to a compression part and a metering part in which a material into which a chip- And that the bubbles do not remain in the resin, and the density of the product can be improved.

Another object of the present invention is to provide a semi-molten molding screw capable of uniformly melting a material by making the temperature distribution between the barrel and the screw uniform by making the amount of heat generated in each section of the screw different.

According to an aspect of the present invention, there is provided a semi-molten molding screw, which is installed inside a barrel into which a chip-shaped material is introduced by a driver, and has a diameter increasing from the rear toward the front A screw shaft having an increased shape; And a flight formed on the outer surface of the screw shaft so as to be spirally formed along the axial direction to transfer the material introduced through the rear portion of the barrel to a mold provided in front of the barrel, wherein the flight increases in thickness from the rear to the front .

According to another aspect of the present invention, the semi-molten molding screw of the present invention is characterized in that a plurality of rod-shaped electrothermal heaters having various lengths are provided in the screw shaft so as to extend along the axial direction.

According to the present invention, the diameter of the screw shaft gradually increases from the rear to the front, and the thickness of the flight gradually increases from the rear to the front. Thus, the volume of the flight's channel And gradually decreases from the rear toward the front. Therefore, the volume of the flight of the flight is large at the supply portion where the chip-shaped material is supplied, the volume of the flight at the compression portion and the metering portion to which the molten resin is transferred is small and a sufficient amount of material can be received at the supply portion , The bubble can be surely discharged and removed from the metering section.

In addition, a plurality of electrothermal heaters having different lengths in the screw shaft are provided in the axial direction to minimize the temperature deviation between the barrel and the screw, and to provide sufficient heat required for melting the material.

1 is a front view of a screw according to an embodiment of the present invention.
2 is an enlarged view of a portion A in Fig.
3 is an enlarged view of a portion B in Fig.
4 is a cross-sectional view of the screw shown in Fig.
FIG. 5 is a cross-sectional view showing a principal part of a screw according to another embodiment of the present invention. FIG.
6 is a cross-sectional view showing a main portion of a screw according to another embodiment of the present invention.
FIG. 7 is a cross-sectional view showing a main part of a screw according to another embodiment of the present invention. FIG.

Hereinafter, preferred embodiments of the semi-molten molding screw according to the present invention will be described in detail with reference to the accompanying drawings.

1 to 4, a semi-molten molding screw according to an embodiment of the present invention includes a screw shaft 10 rotatably installed in a cylindrical barrel, And a flight 20 which is formed on the outer surface of the barrel so as to be spirally formed so as to feed the material fed through the rear portion of the barrel to the mold provided in front of the barrel. By means of a driver (not shown) And performs a function of feeding the material, which is put into the rear part of the barrel while rotating, toward the front of the barrel.

The barrel is heated and melted by a heater provided on the outer surface of the barrel when a chip-shaped material (for example, magnesium material) is put into the barrel as a constituent part of the semi-molten molding apparatus and is converted into a liquid resin. Although not shown in the drawing, a hopper to which a chip-shaped material is fed is connected to a rear portion of the barrel, and a mold having a cavity in which a semi-molten product is formed is connected to a front portion of the barrel.

The screw of the present invention has a supply portion P1 for supplying a material from the rear end of the screw shaft 10 to approximately one half of the entire length, (P2) for transferring the material fed from the feeder (P1) to the front end and the front end by melting and compressing the material fed from the feeder (P1) to the front end and the front end from the compression part (P2) And a metering section (P3) for feeding the molten resin transferred to the front side head of the barrel by a predetermined amount.

The screw shaft 10 has an elongated circular bar shape extending in the axial direction of the barrel, and has a shape in which the diameters D1 and D2 gradually increase from the rear toward the front.

The flight 20 is formed on the outer surface of the screw shaft 10 in a spiral shape along the axial direction to perform a function of forwarding the material introduced through the rear portion of the barrel. The flight (20) has a shape in which the thickness (t) gradually increases from the rear to the front.

Since the screw shaft 10 and the flight 20 act to transfer a chip-shaped material, the surfaces of the screw shaft 10 and the flight 20 are preferably nitrided to improve abrasion resistance and hardness.

The depth of the valley (C) of the flight (20) decreases from the rear end to the front end of the screw shaft (10).

The diameter of the screw shaft 10 gradually increases from the rear to the front as described above and the thickness t of the flight 20 gradually increases from the rear to the front The volume of the valleys C of the flights 20 and the flights 20 gradually decreases from the rear toward the front. Therefore, the volume of the valley C of the flight 20 in the supply part P1 to which the chip-shaped material is supplied is large, and the compression part P2 and the metering part P3, to which the molten resin is fed, The volume of the trough C of the trough portion C becomes small and a sufficient amount of material can be received in the supplying portion P1 and the bubble can be surely discharged and removed in the metering portion P3.

Further, since the depth of the valley (C) of the flight (20) decreases from the rear to the front of the screw, the bubbles of the molten resin can be smoothly discharged and removed.

The flight 20 includes a leading flight 21 as a forward facing surface and a trailing flight 22 as a rearward facing surface and a leading flight 21 and a trailing flight 22 between the leading flight 21 and the trailing flight 22 (23).

The leading flight 21 acts to push out the chip-shaped material and the molten resin. In this embodiment, the leading flight 21 is substantially perpendicular to the plane of the screw shaft 10, that is, Angle.

However, as shown in another embodiment in Fig. 5, the leading flight 21 may be formed to be inclined forward at an angle? Of 80 to 85 degrees with respect to the surface of the screw shaft 10.

When the angle formed between the leading flight 21 and the surface of the screw shaft 10 is formed to be slightly tilted forward at an angle of 80 to 85 ° as described above, the screw shaft 10 rotates and the leading flight 21 The movement of the material over the surface of the leading flight 21 can be suppressed when the material is pushed and transported by the transporting means. When the angle between the leading flight 21 and the surface of the screw shaft 10 is less than 80 °, the material is caught in the lower edge of the leading flight 21 or the frictional force is increased, And when the angle formed by the leading flight 21 and the surface of the screw shaft 10 is 85 ° or more, there is no effect of improving the feed efficiency of the material as compared with the case where the angle is a right angle (90 °).

6, in order to prevent the molten resin from being pushed into the space between the inner circumferential surface of the barrel and the flight 20 in the compression section P2 and the metering section P3, the front end of the screw shaft 10 The anti-jamming protrusions 24 can be formed at the apexes of the flights 20 formed up to the trenches. The protruding protrusions 24 need not be formed over the whole of the flight 20. The protrusions 24 of the screw shaft 10 may be formed to prevent the molten resin from being pushed by the compressing portion P2 and the metering portion P3. And is formed at the apex of the flight 20 which is formed from the half of the entire length to the front end.

It is preferable that the anti-jamming protrusions 24 have a ratchet tooth shape, that is, a saw tooth shape of a substantially right triangle as in this embodiment.

7, the flight 20 includes a leading flight 21 that is a forward facing surface and a trailing flight surface 22 that is a backward facing surface. It is preferable that a plurality of grooves 25 are formed to prevent scattering of the chip-shaped material.

The grooves 25 prevent the material from being scattered while being pushed backward when the chip-shaped material is pushed forward by the flight 20 when the screw shaft 10 is rotated.

Meanwhile, the screw of the present invention performs a function of transferring a material in a barrel heated to a high temperature, in which a temperature deviation occurs between the barrel and the screw. In order to reduce the temperature deviation between the barrel and the screw and to transmit uniform heat to the material, a plurality of rod-shaped electrothermal heaters (30) having various lengths are installed in the screw shaft (10) do.

Here, it is preferable that the number of the electrothermal heaters 30 is reduced from the front end portion to the rear end portion of the screw shaft 10. That is, it is preferable that the number of the electrothermal heaters 30 in the portion corresponding to the supply portion P1 of the screw is larger than the number of the electrothermal heaters 30 in the compression portion P2 of the screw and the metering portion P3 .

This is because the temperature of the material to be introduced when the chip material is inserted into the rear part of the barrel is low and the heater is not installed in the rear part of the barrel connected with the hopper, A large temperature deviation occurs. When sufficient heat is supplied to the workpiece in the supply part P1 to heat the workpiece, a sufficient amount of phase change can be induced to a desired degree even if a relatively small quantity of heat is supplied in the compressing part P2 and the metering part P3. Therefore, it is desirable to arrange a larger number of heat transfer heaters 30 in the supply part P1 that requires a relatively large initial amount of heat.

In order to increase the number of the heat transfer heaters 30 in the supply portion P1 to be larger than the number of the heat transfer heaters 30 in the compression portion P2 and the metering portion P3, do.

A disk heater support member 40 having a plurality of heater insertion holes 41 through which the electrothermal heater 30 is inserted and supported is inserted into the screw shaft 10, Relative to the inner circumferential surface.

Therefore, even when the screw shaft 10 is rotated by a driver (not shown), the electrothermal heater 30 and the heater support member 40 are kept in a fixed state without rotating.

As described above, the screw of the present invention has a shape in which the diameter of the screw shaft 10 gradually increases from the rear to the front, and the thickness of the flight 20 gradually increases from the rear to the front So that the volume of the valleys C of the flights 20 and the flights 20 gradually decreases from the rear to the front. Therefore, the volume of the valley C of the flight 20 in the supply part P1 to which the chip-shaped material is supplied is large, and the compression part P2 and the metering part P3, to which the molten resin is fed, The volume of the valley C of the weighing part P3 becomes small and a sufficient amount of material can be received in the supplying part P1 and the bubble can be surely discharged and removed from the weighing part P3.

In addition, a plurality of electrothermal heaters (30) having different lengths in the screw shaft (10) are provided in the axial direction to minimize the temperature deviation between the barrel and the screw, and to provide sufficient heat for melting the material.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention as defined by the appended claims. And it is to be understood that such modified embodiments belong to the scope of protection of the present invention defined by the appended claims.

10: screw shaft 20: flight
21: leading flight 22: trailing flight
23: Vertex 24: Anti-jamming roughness
25: groove 30: electric heater
40: heater supporting member 41: heater inserting hole
C: Flight's channel t: Flight thickness
P1: supply part P2: compression part
P3:

Claims

A screw shaft 10 installed inside the barrel into which chips are inserted and rotated by a driver and having a diameter increasing from the rear to the front;
And a flight (20) formed on the outer surface of the screw shaft (10) so as to be spirally formed along the axial direction to transfer the material, which has been introduced through the rear portion of the barrel, to the mold provided in front of the barrel,
The thickness t of the flight 20 increases from the rear toward the front,
A plurality of rod-shaped electrothermal heaters 30 having various lengths are provided in the screw shaft 10 so as to extend along the axial direction. The electrothermal heater 30 is fixed to the screw shaft 10 from the front end of the screw shaft 10 to the rear end Shaped heater support member 40 having a plurality of heater insertion holes 41 through which the electrothermal heater 30 is inserted and supported is inserted into the screw shaft 10, A bearing is provided between the outer circumferential surface of the heater support member 40 and the inner circumferential surface of the screw shaft 10 so that the screw shaft 10 can rotate relative to the heater support member 40,
The flight 20 includes a leading flight 21 as a forward facing surface and a trailing flight 22 as a rearward facing surface and the leading flight 21 includes a screw shaft 10, Is inclined forward at an angle of 80 to 85 with respect to the plane of the leading flight 21 and the trailing flight 22, A plurality of grooves 25 in a 'f' shape are formed,
Wherein the anti-skid protrusions (24) in the form of a ratchet tooth of a right-angled triangle are formed at the apex of the flight (20) formed from the half of the entire length of the screw shaft (10) Screw for melt molding.

2. The screw for semi-molten molding according to claim 1, wherein a depth of a valley (C) of the flight (20) decreases from a rear end to a front end of the screw shaft (10).

delete

The screw for semi-molten molding according to claim 1, wherein the surfaces of the screw shaft (10) and the flight (20) are nitrided.