KR100869670B1 - Female thread molding method using powder injection molding - Google Patents

Abstract

The present invention relates to a screw molding method using a powder injection molding, and more particularly to a female screw molding method using a powder injection molding that can be integrally molded to the molding without a separate process in the metal or ceramic powder injection molding. will be.

To this end, the present invention is to form a metal powder mixture (mixture) by mixing the metal powder or ceramic powder 75 ~ 95wt.% And the binder 5 ~ 25wt.%, To form a female screw using the metal powder or ceramic mixture Forming a green part by injecting the mold at a high pressure into a mold, extracting the injection molded product using a solvent, and using a debinding kiln at room temperature using a debinding kiln. Removing the binder at ˜1,000 ° C., obtaining a finished product having a screw formed by sintering the degreased brown part to a sintering temperature (1,200 to 1,800 ° C.) of the metal and ceramic powder. It is characterized by.

Description

Female thread molding method using powder injection molding {THE METHOD OF FORMING FEMALE SCREW USING POWDERED METAL}

1 is a perspective view of a mold for female thread molding according to the present invention

Figure 2 is a front cross-sectional view of the fixed mold plate of the female thread forming mold according to the present invention.

Figure 3 is a front view of the rotating body of the female thread forming mold according to the present invention

4a to 4c are cross-sectional views showing the operating state of the mold for female thread forming according to the present invention.

The present invention relates to a screw molding method using powder injection molding, and more particularly, to a female screw molding method using powder injection molding, which enables the female and the female thread to be integrally molded to a molding without any separate process in metal and ceramic powder injection molding. will be.

In general, Powder Injection Molding is a metal or ceramic powder mixed with a binder made of organic materials, and then molded using the injection molding method, the binder is removed, and finally sintered to obtain a metal or ceramic product. Say the latest powder molding technology to manufacture.

The metal powder used herein is Fe-based, stainless steel, low alloy steel, Fe-Ni-C, copper alloy, Fe-Ni, STS316L, 17-4PH, and alumina, zirconia, etc. are representatively used as ceramic powder. .

It is a mass production technology of hard-working materials, which allows mass production of complex three-dimensional molded parts. It is a new process combining powder metallurgy technology and injection molding technology, which is a mass production technology of precise plastic parts. The powder injection molding method may be classified into metal injection molding (MIM) and ceramic injection molding (CIM) according to materials used.

In the conventional powder metallurgy method, since the pressure is not evenly transmitted to the inside of the product during molding, there is a difference in the filling density between the surface and the inside, so that the final sintered density is not uniform, which causes a decrease in mechanical properties. For this reason, the shape of the product is limited, and thus it has been limitedly applied to the manufacture of products having the same cross-sectional shape.

In addition, in the case of forming a female screw in a molded article manufactured in three dimensions, there is a problem in that the female thread is not formed at a time and the female thread acid is produced by secondary processing (machine processing, etc.) on the product after sintering.

As a technique for forming a female screw in a metal and ceramic molding as described above, Republic of Korea Patent No. 225967 (name of the invention: a method of forming a female screw of a small bonding body) is known.

In the above technique, a mixture of metal cobalt powder and tungsten carbide powder is placed in a pressing mold, and molded at 600-100Kg / cm ² pressure to sinter firstly at around 800 ° C, and to make a female female hole in the first sintered body and into a hole. Insert the low speed tapping tool to form the female thread on the inner surface of the hole, but form a pitch that is 20-25% larger than the pitch spacing of the finished product, clean the screw groove, and put it in the sintering furnace to obtain 1,350-1,500 ℃. A female screw molding method for a small bond gold body, characterized in that the second sintering at a temperature.

However, the above technique also takes a lot of work time and unnecessary movement because the internal thread must be separately formed by using the tap tool in the hole after sintering the primary molding, which causes a problem that the defect rate of the product is greatly increased. It is difficult to process parts when manufacturing small precision parts such as parts of mobile phones or cameras, and many moldings cannot be recycled due to the tap process after the first sintering.

The present invention has been made in consideration of the above disadvantages, and an object thereof is to obtain a uniform packing density throughout the molding to improve the homogeneity and performance of precision parts and to obtain excellent surface roughness.

In addition, another object of the present invention is to form and sinter the female thread in the injection molded water state before the first sintering to the molding, which can significantly reduce the working time and integrally form the female thread capable of forming the female thread smoothly on precision parts. In providing a mold apparatus.

In addition, another object of the present invention in the conventional method of forming a female screw through a separate tap process after the first sintering, by forming a female screw in the compression molding state before sintering, significantly reducing the working time and smoothly to precision parts The present invention provides a screw molding method using powder injection molding that can mold female threads.

The present invention for achieving the above object is to form a metal powder mixture (mixture) by mixing the metal powder or ceramic powder 75 ~ 95wt% and the binder 5 ~ 25wt%, female screw using the metal powder or ceramic mixture Forming a green part by injecting the mold at a high pressure into a mold so as to mold the mold, dewaxing the injection molded molding with a solvent, and debinding the injection molded molding by debinding kiln. Removing the binder at room temperature ~ 1,000 ℃ using, step of obtaining the finished product with a screw by heating the degreasing degreasing (brown part) to the sintering temperature (1,200 ~ 1,800 ℃) of the metal and ceramic powder (sintering) Characterized in that consisting of.

The metal powder used here is Fe, stainless steel, low alloy steel, Fe-Ni-C, copper alloy, Fe-Ni, STS316L, STS304, STS440, 17-4PH, and the ceramic powder is limited to alumina, zirconia, etc. It doesn't happen.

In addition, since the firing temperature varies depending on the sintering temperature of the metal powder or ceramic powder used, the firing temperature is fired at the firing temperature of the metal powder to be used.

In addition, in the mold, the movable die has a molding groove in which a molding is formed inside the nozzle, and a nozzle into which the mixture is introduced into the molding groove is molded. The groove is formed in close contact with the movable die and has a hole formed in the inner central portion, and a female screw portion at the other side. And a fixed plate having a through hole formed up and down, a rack inserted into the through hole and assembled to a piston of a cylinder formed at an upper portion thereof, a first gear and a second gear meshed with the rack and formed on the same axis, and the second gear. It is characterized in that it is configured to include a rotating body formed with a male screw on both sides and a third gear and a bearing in the center portion.

Hereinafter, described in detail with reference to the accompanying drawings of the present invention.

1 is a perspective view of a female thread forming mold according to the present invention, Figure 2 is a front sectional view of one side of the female thread forming mold according to the present invention, Figure 3 is a front view of a shaft of the screw for forming mold according to the present invention.

As shown, the female screw molding apparatus 100 according to the female screw molding method using the powder injection molding according to the present invention is largely attached to an injection machine (not shown) and fixed to the movable mold 10 and the injection machine that move left / right. It consists of a stationary plate (20).

The movable die 10 is formed in the center of the molding groove 11 is engraved in the structure of the molding and a nozzle 12 is formed on one side of the mixture is introduced.

In addition, the movable plate 10 generally includes a rod (not shown) partially inserted into the fixed plate 20 on the outside to induce close contact with the fixed plate 20, and a pin for removing the molding. It is formed, which is a specification of a general injection mold, the detailed description thereof will be omitted in the present invention.

The stationary plate 20 has a through hole 21 penetrating the upper and lower portions and a hole 23 through which a part of the internal rotating body 22 is exposed at the front side, and the rotating means 30 is assembled therein. The space 24 is formed.

In addition, a female screw portion 25 is formed at a position opposed to the hole 23.

In addition, the cylinder 40 is fixed to the upper portion by the fixing table 26, the rack 31 is assembled to the piston 41 of the cylinder 40 is inserted into the through-hole 21.

The rack 31 is engaged with the first gear 32 of the rotating means 30 formed in the inner receiving space (24).

The first gear 32 has a second gear 33 is formed on the same axis and the second gear 33 is meshed with the third gear (22a) formed on the rotating body (22).

In addition, the thickness of the third gear (22a) is formed to be 1/2 of the thickness of the second gear 33, it is possible to move left / right by the width of the second gear 33 in the engaged state.

The rotating body 22 has male screws 22b and 22c assembled at the hole 23 and the female screw portion 25 of the fixed plate 20 at both ends thereof, and the third gear 22a and the bearing 22d at the center portion thereof. ) Is formed.

On the other hand, the outer side of the fixed die 20, the spring (not shown) and the insertion portion (not shown) to insert the rod 13 of the movable die 10 and the template to solve the impact of the close contact when the template is in close contact and Cooling water and the like are formed for controlling the temperature of the mold, which is a basic specification of a conventional injection mold, and thus, a detailed description thereof will be omitted.

Hereinafter, the operation state in the female screw molding method using the powder injection molding according to the present invention will be described in detail with reference to FIGS. 4A to 4C.

4A is a side view of the movable plate 10 and the stationary plate 20 separated from each other.

As shown in the drawing, the piston 41 of the stationary plate 20 descends, thereby lowering the rack 31 connected thereto, whereby the first, second, and third gears 32, 33, and 22a move in the forward direction. Rotating the rotating body 22 by rotating the male screw 22c on one side of the rotating body 22 in such a manner that the rotating body 22 is rotated in engagement with the formed female threaded portion 25 of the fixed plate 20. The male screw 22b of the other side of the rotating body 22 is formed in the state which protruded from the hole 23 partially.

In the state formed as described above, as shown in FIG. 4B, the movable die 10 is advanced to be in close contact with the stationary die 20, and the mixture is injected into the forming groove 11 through the nozzle 12 to form a compressed molded article. Cool to form firmly.

At this time, the diameter of the male screw (22b) is inserted smaller than the hole 23 of the fixed plate 20, the mixture is introduced into the fixed plate 20 side to form a deep female screw.

As described above, when the movable die 10 and the stationary die 20 are in close contact with each other, the rack 31 is raised when the molded article is formed therein. The second gear 33 rotates in the reverse direction, whereby the third gear 22a of the rotating body 22 engaged with the second gear 33 rotates so that the male screw 22c formed on the rear side rotates, thereby fixing the fixed template 20. The rotary body 22 is reversed by rotating in engagement with the female screw portion 25 formed at the inner side thereof.

Thus, the front male screw 22b is separated without affecting the female screw 51 of the compression molded article 50 formed on the outer side.

As described above, in the state in which the rotating body 22 is reversed and the molding 50 and the male screw 22b are separated, the movable mold 10 is moved as shown in FIG. 4C to discharge the molding.

The powder injection molding formed as described above is degreased and completely sintered at room temperature to 1,800 ° C. using a degreasing and sintering furnace to obtain a threaded finished product.

As described above, according to the present invention, by adding a flowable binder to the metal powder, it is possible to achieve a uniform pressure transfer to obtain a uniform packing density throughout the molding, thereby improving the homogeneity and performance of the precision parts and excellent surface roughness There is an effect that can be obtained.

In addition, in the conventional method of forming a female screw through a separate tap process after primary sintering, the female screw is formed and sintered in a compressed molding state before sintering, thereby significantly reducing work time and smoothly forming a female screw even on precision parts. have.

Claims (5)

75 to 95 wt% of metal powder or ceramic powder and 5 to 25 wt% of binder are mixed to form a metal powder mixture; Forming an injection molded molding by injection into a mold at a high pressure so as to mold a female screw using the fluid metal and ceramic powder mixture; Removing the binder at room temperature to 1,000 ° C. using a debinding kiln of the injection molded molding; Sintering the degreased degreasing (brown part) to the sintering temperature (1,200 ~ 1,800 ℃) of the metal and ceramic powder to obtain a finished product formed by screwing (sintering); female screw using powder injection molding, characterized in that consisting of Molding method. According to claim 1, wherein the mold is formed in the molding groove (11) formed inside the movable die 10 formed to be connected to the nozzle 12 on one side; Rotating means 30 which is in close contact with the movable plate 10 and partially exposed to the inner receiving space 24 is formed, and the rack 31 which drives the rotating means 30 is formed. Screw molding method using a powder injection molding, characterized in that made of a fixed plate (20) formed by assembling the piston 41 of the cylinder 40 formed in the upper portion through the upper and lower parts. The method of claim 2, wherein the rotating means 30 is formed on the inside of the fixed plate 20, the first gear 32 to be engaged with the rack 31, and the same axis as the first gear (32) And a third gear 22a formed at the center portion of the rotating body 22 and engaged with the second gear 33 and the second gear 33, Here, as the rack 31 moves up and down, the first gear 32 and the second gear 33 formed on the same axis rotate, and thus the third gear 22a meshed with the second gear 33. Female screw molding method using a powder injection molding, characterized in that by rotating the rotating body (22). The powder injection method of claim 3, wherein the third gear 22a is formed to have a thickness of 1/2 of the second gear 33 so that the rotor 22 can move in the engaged state. Female thread molding method using molding. delete

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