KR20100026824A - Press forming method for case of electronic products - Google Patents

Abstract

PURPOSE: A press molding method for a case of an electronic product is provided to reduce defects caused by breaking of a magnesium alloy plate. CONSTITUTION: A press molding method for a case of an electronic product is as follows. A molding device is prepared(S1). The molding device comprises a mold and a punch. A magnesium alloy plate is arranged on the top of the mold to cover a molding space of the mold(S2). The magnesium alloy plate is pressed in a case shape(S3). The punch and the mold are heated by heaters to soften the magnesium alloy plate. The punch is first descended to the Mg alloy plate(S31), and then the punch is second descended slower than the first descending(S33). And the punch is third descended(S35).

Description

PRESS FORMING METHOD FOR CASE OF ELECTRONIC PRODUCTS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press molding method of an electronics case, and more particularly, an electronics case, in particular, a case of a laptop computer or a mobile phone case, using a magnesium alloy plate as a material. It relates to a molding method using the method.

With the development of the electronics industry, many kinds of electronic products (eg, telecommunications, home appliances) have emerged. Such electronics include, for example, notebook computers, mobile phones, MP3 players (or similar players), mobile electronics such as IC recorders and other consumer electronics. Consumers demand many excellent characteristics, performance or advantages for such electronics, in particular mobile electronics. Among them, the lightness of the product is known to be an important performance or characteristic of the electronic product which the consumer demands from the producer and the producer pursues accordingly.

In recent years, the use of magnesium alloys (i.e., Mg alloys), which are light, yet have sufficient strength and excellent vibration damping properties, are increasingly used as electronic case materials. The electronics case includes, among other geometric features, thin thicknesses and edges that are approximately vertically curved. As a molding method using a magnesium alloy for obtaining the above-described characteristic shape, a method of melting and casting a magnesium alloy, in particular, a die casting method is known.

However, fabricating the case by the die casting method has a problem that complicated and time-consuming post-processes are required, such as a process of removing gates and burrs. In addition, the case produced as described above, the surface is rough, the appearance is bad, there is a problem that the light weight is also poor. Furthermore, the die casting process requires expensive equipment and poor working environment.

On the other hand, a technique of forming an electronics case by using a magnesium alloy plate as a material and punching once at a high temperature and relatively high speed has been proposed in the related art, but such a technique has a high product defect rate. There is a problem that is high.

Accordingly, one technical problem of the present invention is to use warm press molding, which adds a high speed press action of contacting (or prepressing) a punch to the magnesium alloy plate before the actual press action on the magnesium alloy plate, The low defect rate and high economy provide a way to obtain a lightweight, clean surface electronics case.

Another technical problem of the present invention is to provide a method for sufficiently preheating the magnesium alloy plate through contact between the heated punch and the magnesium alloy plate with the punch stopped, before the actual press action on the magnesium alloy plate. .

According to an aspect of the present invention, there is provided a molding apparatus including a lower mold having a molding space formed thereon and an upper punch corresponding to the molding space, and an Mg alloy plate on the upper surface of the mold to cover the molding space. And a pressing step of forming the Mg alloy plate into a bent case by the interaction between the punching material and the molding space. During the pressing step, the punch and the mold are heated to a temperature for softening the Mg alloy plate by self-built heaters, and the pressing step causes the punch to be brought into contact with the Mg alloy plate in a first position. A first lowering step of lowering the speed, a second lowering step of lowering the punch further at a second speed slower than the first speed, and a third order of lowering the punch at a third speed slower than the second speed A descent step.

According to a preferred embodiment, the pressing step comprises the punch contacting the Mg alloy plate between the first lowering step and the second lowering step and between the second lowering step and the third lowering step. The method may further include a falling pause step of keeping the stationary state for a predetermined time.

According to a preferred embodiment, the forming space may be provided with a supporting block that is elastically lowered by the force of the punch, the supporting block, the pressing block, the elastic support of the Mg alloy plate during the pressing step. have.

The thickness of the Mg alloy plate is preferably 0.3 to 0.9 mm, more preferably 0.6 mm, and the stop time of the descent pause step is preferably 1 second to 3 seconds, more preferably, 1.5 to 2.5 seconds. When the Mg alloy sheet has a thickness of less than 0.3 mm, there is a high risk of rupture during or after molding, and when the thickness exceeds 1.5 mm, the Mg alloy plate not only has poor moldability but also causes coarsening of the case parts. Done. Within the above thickness range, if the punch stop time of the descent pause step is less than 1 second, the effect of preheating the Mg alloy plate before the actual press action is not substantially exhibited, and if the heating is about 1 to 3 seconds, the actual press Since the effect of preheating the entire case part is sufficiently obtained, a time exceeding 3 seconds only causes a waste of time without improving moldability.

According to one preferred embodiment, the temperature for softening the Mg alloy plate is set to 200 ~ 350 ℃, if less than 200 ℃, may cause a failure of the edge of the Mg alloy plate fracture during press molding, 350 ℃ If exceeded, excessive softening of the Mg alloy plate and thereby stickiness may occur, which may further lower the formability of the case.

During the press step, the punch and the mold can be heated to the same temperature, more preferably, the temperature of the punch is set lower than the temperature of the mold. Further, before the material disposing step, further comprising the step of conveying the Mg alloy plate in the vicinity of the molding apparatus using a transfer mechanism, in the carrying step, the Mg alloy plate is preheated by a heater installed in the transfer mechanism Can be.

According to embodiments of the present invention, there is an advantage in that an electronic case made of Mg alloy material having a clean and light surface can be economically manufactured at a low defect rate.

 According to embodiments of the present invention, the Mg alloy plate is formed into a bent case by the interaction of a mold having a molding space and a punch corresponding to the molding space, and the punch and the mold are self-built heaters. By heating, the Mg alloy plate can be softened in the state which is easy to shape | mold by this.

The punch descends in two steps at a relatively low speed from the position in contact with the Mg alloy plate, so that a reliable and stable press action is possible, whereby the failure due to rupture of the Mg alloy plate is reduced.

In addition, since the punch descends at a relatively high speed to the position in contact with the Mg alloy plate, it is possible to greatly reduce the problem of delay in processing time due to the actual long press. In addition, since the punch is held in a stationary state for a predetermined time after the Mg alloy plate is in contact with the punch, the Mg alloy plate can be sufficiently preheated by heat conduction. This further contributes to increasing the formability of the case described above. In the case of mass production systems, a transport mechanism, for example a conveyor belt, may be required to transport the Mg alloy plates to or near the molding apparatus. In addition, by making the temperature of the punch lower than the temperature of the mold, it is possible to prevent local softening of the Mg alloy plate and localized texture degradation and shape deterioration caused by the softening thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples to ensure that the spirit of the present invention can be fully conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

1 is a block flow chart illustrating a press molding method of an electronic case according to an embodiment of the present invention, Figures 2a, 2b, 2c and 2d is a molding for implementing the press molding method shown in FIG. Sections for explaining the apparatus and its operation.

Referring to Figure 1, the press molding method of the present embodiment, the step of preparing the molding apparatus (S1), the step of placing the material, that is, Mg alloy plate on the mold upper surface of the molding apparatus (S2), and the molding apparatus And a press step (S3) of press molding the Mg alloy plate.

The molding method uses a molding apparatus as shown in FIGS. 2A-2D and described in detail below. In the present specification, the preparing step of the molding apparatus includes setting the molding apparatus in an operable state. Herein, the setting includes keeping the mold and the punch to be described below mounted on the molding apparatus, and further, checking and / or preparing to perform the operations of the molding apparatus such as a power supply. Includes putting on.

As shown in FIGS. 2A to 2D, the molding apparatus 100 of the present embodiment includes a lower mold 110 and an upper punch 120. The mold 110 includes a flat upper surface and, for example, a rectangular molding cavity 112 formed concave from the upper surface. In addition, the punch 120 has a size and shape corresponding to that of the forming space 112, and is, for example, hydraulically driven so as to be inserted into the forming space 112 together with a part of the Mg alloy plate during the press operation. It can descend by.

 In the present embodiment, the forming space 112, for example, is provided with a support block 114 that is elastically supported by an elastic means 113, such as a spring. The lower end of the elastic means 113 is supported on the bottom surface of the molding space 112, the upper end of the elastic means 113 supports the support block 114. Accordingly, the support block 114 may descend in the forming space 112 while opposing the descending punch 120 and ascend again with the punch 120 to restore the original position. . The backing block 114 has a flat top surface, and the top surface of the backing block 114 may be coplanar with the top surface of the mold body.

The first heater 115 and the second heater 125 are embedded in the mold 110 and the punch 120, respectively. The first heater 115 may be installed on each of the main body and the support block 114 of the mold 110, and may be installed on any one of the main body and the support block of the mold. In addition, a jig means 117 (see Fig. 2a) is installed on the upper surface of the mold 110, the jig means 117 is to move the Mg alloy plate 2 in an undesired direction during the press molding process Prevent it.

In this embodiment, in the material disposing step S2, as shown in FIG. 2A, the Mg alloy plate 2 is disposed on the upper surface of the mold 110 of the molding apparatus 100. In the present embodiment, the disposed Mg alloy plate 2 is supported by most of the region except the edge portion by the support block 114, the edge region of the Mg alloy plate 2 is the upper portion of the mold body Across the surface. In the present embodiment, the Mg alloy plate 2 is positioned on the mold upper surface by the above-described jig means 117.

In an alternative embodiment, if the support block 114 is positioned at a height lower than the upper surface of the mold body, or if the support block is omitted, only the edge area of the Mg alloy plate 2 is the mold body. It is supported over the top surface of and the central region of the Mg alloy plate 2 may be maintained without contacting the mold 110 above the forming space.

The Mg alloy plate is warm press-molded according to an embodiment of the present invention to produce an electronic case. The reason for the warm forming is that the Mg alloy is a material having a very small elongation at room temperature. As is known, Mg alloys have a hexagonal packed structure (HCP) and do not have sufficient slip system at room temperature. Magnesium alloy is not easy to operate because the critical decomposition shear stress of the non-base slip at room temperature is very large compared to the bottom slip.

For the arbitrary deformation of the Mg alloy, five independent slip systems have to be operated under Von Mises conditions. Press molding the Mg alloy plate with a warm press molding of approximately 200 to 350 ° C., and most preferably about 300 ° C., allows the five or more slip systems described above to operate, thus bending the edges without breaking the Mg alloy plate. It can be molded into a genuine electronics case.

In this embodiment, the Mg alloy plate is obtained from Mg alloy consisting of Al 1-7 wt%, Zn 0-2.5%, Mn 0-0.6%, residual Mg and unavoidable impurities. Al is added for the purpose of improving strength, corrosion resistance and the like. When Al exceeds 7 wt%, the plastic deformation of the magnesium alloy is inferior, which is not appropriate. Zn contributes to an increase in strength, but excessive amounts may cause corrosion resistance. Mn may be added for the purpose of reducing the corrosion resistance caused by the above added material. Zn and Mn may be omitted or replaced with other additive metals.

Returning to the figure, it is preferable that the thickness of the Mg alloy plate 2 is 0.3-0.9 mm. In view of such a thickness, the press molding temperature of 200-350 degreeC, and the composition range of the above-mentioned Mg alloy plate 2, the case of the intended high quality electronics can be shape-molded without defect. In particular, as will be described below, the press forming method of the present embodiment includes a falling pause step S2 in which the punch 120 is in contact with the Mg alloy plate 2 for 1 second to 3 seconds in a stationary state. When the thickness exceeds 0.9 mm, the press molding is performed in a state in which heat transfer from the punch 120 to the Mg alloy plate 2 is not sufficiently performed, that is, in a state of less preheating.

Referring back to FIG. 1, in the electronic case forming method of the present embodiment, as shown in FIGS. 2A to 2D, the interaction between the punch 120 and the forming space 112 of the mold 110 is performed. And a press step S3 for drawing-molding the Mg alloy plate 2. In this embodiment, the press step (S3), the first falling step (S31) of the punch, the first falling pause step (S32), the second falling step (S33) of the punch, the second falling pause step (S34) And, the third falling step (S35) of the punch.

During the press step S3, the mold 110 and the punch 120 have a temperature of softening the Mg alloy plate 2 by the first and second heaters 115 and 125 embedded therein. Heated to The operation of the first and second heaters 115 and 125 may be performed during or before the above-described material disposing step S2 of disposing the Mg alloy plate 2 on the mold 110.

 In practice, since press molding for the production of multiple electronics cases is performed continuously, the first and second heaters 110, 120 can continue to operate during their successive press forming processes.

In addition, the temperatures of the mold 110 and the punch 120 may be equal to each other. Alternatively, the temperature of the punch 120 may be lower than the temperature of the mold 110. When the temperature of the punch 120 is lower than the temperature of the mold 110, it is possible to prevent the initial softening of the Mg alloy plate and to prevent the deterioration of the local shape and the deterioration of the texture resulting from the initial softening.

In the first lowering step (S31) of the initial press step, the punch 120 is lowered at a first speed, and in the second lowering step (S33) of the middle of the press step, the punch (120) is first speed Lowering the second slower speed, the third lower step (S35) of the late stage of the press step to fully lower the punch 120 at a third speed slower than the second speed. The first speed is preferably as fast as possible within the range to shorten the molding time and thereby increase productivity. In addition, since the second speed and the third speed are the descending speeds of the punches 120 for the actual press forming, it is required that the Mg alloy plate 2 is slow enough not to break in the pressing process.

By the first punch lowering step S1, the punch 120 descends to a position in contact with the Mg alloy plate 2 supported by the mold 110 and its supporting block 114. Immediately following the first punch lowering step S1, a first lowering pause step S32 in which the lowering of the punch 120 is stopped is performed.

In the first descending pause step (S32), the punch 120 is in a stationary state, in contact with the center region, which is a rectangle of the Mg alloy plate 2, excluding the edge. Thereby, the Mg alloy plate 2 is preheated to a temperature at which the next practical press molding becomes easy. At this time, it is preferable that the punch 120 stop temperature of the falling pause step (S32) is 1 second to 3 seconds. And this time range is especially suitable when the thickness of the Mg alloy plate 2 is 0.3 to 0.9 mm.

 Next, by the second lowering step (S33), the punch 120 is further lowered while pressing the Mg alloy plate (2), whereby the support block 114 is lowered while widening the forming space 112 further down do. The Mg alloy plate 2 enters into the forming space 112 together with the supporting block 114, so that the edge of the Mg alloy plate 2 which does not cover the forming space 112 has an angle of less than 90 degrees. Make bending deformations. The support block 114 continues to support the bottom surface of the Mg alloy plate 2 while being lowered. As a result, the Mg alloy plate 2 is primarily bent. At this time, the punch lowering speed of the second lowering step S33 is slower than the punch lowering speed of the first lowering step.

In the second lowering pause step S34, the punch 120 further adds the first bent Mg alloy plate 2 to the next Mg alloy plate 2 for reliable processing in the next third lowering step. Heat. As a result, the Mg alloy plate 2 is further softened. In this case, it is preferable that the stop temperature of the punch 120 of the falling rest step S32 is 1 second to 3 seconds.

Next, in practice, the third descending step S35 is performed in which the molded case is completed. Next, in the third lowering step S35, the punch 120 descends completely while pressing the Mg alloy plate 2, and the support block 114 descends to fully expand the forming space 112. Accordingly, the edge of the Mg alloy plate 2 which does not cover the forming space 112 is deformed to be completely bent vertically, and the supporting block 114 is descending the bottom surface of the Mg alloy plate 2. By this, the Mg alloy plate 2 has a flange of a vertically curved edge, wherein the punch lowering speed of the third lowering step S35 is slower than the punch lowering speed of the second lowering step. .

Referring to FIG. 2A, the temperature of the mold and punch is measured by thermocouples 119 and 129 mounted on each of them. Based on the temperature measured by the thermocouple, the controller 130 controls the temperature of the mold 110 and the punch 120. Further, punch lowering speeds of the above-described primary, secondary and tertiary punch lowering steps S31, S33, and S35, and punch stop positions in the primary and secondary lowering rest steps S32 and S34, respectively. It may also be controlled by the controller 130. In addition, to control the punch stop position, the controller 130 may utilize information obtained from a sensor or a limit switch.

3 is a view for explaining a further embodiment of the present invention, referring to FIG. 3, a conveyor belt type transfer mechanism 200 for continuously transporting the Mg alloy plate 2 near the forming apparatus 100. And, you can see the work shelf 300 to stack the transferred Mg alloy plate (2) before the press work. In this case, heaters 210 and 310 may be installed in the transfer mechanism 200 and the work shelf 300, respectively. At this time, the temperature heated by the heaters (210, 310), about 50 ℃ or so, do not need to be significantly high, it is enough to prevent the impact due to sudden heat on the Mg alloy plate (2) during the actual press process.

The electronic product case obtained through the press molding according to the above embodiments may be manufactured through a surface treatment step including at least a step of degreasing, chemical treatment, washing, and the like followed by a painting step.

1 is a block diagram illustrating a press molding method of an electronic case according to an embodiment of the present invention.

2A to 2D are cross-sectional views illustrating a molding apparatus for implementing the press molding method illustrated in FIG. 1 and an operation thereof.

3 is a view for explaining another embodiment of the present invention.

Claims (9)

Preparing a molding apparatus including a lower mold in which a molding space is formed and an upper punch corresponding to the molding space; A material disposing step of disposing an Mg alloy plate on the mold upper surface to cover the molding space; And By the interaction of the punch and the molding space, the pressing step of forming the Mg alloy plate into a bent case, During the press step, the punch and the mold are heated to a temperature for softening the Mg alloy plate by self-built heaters, The pressing step may include a first lowering step of lowering the punch at a first speed to a position contacting the Mg alloy plate, a second lowering step of further lowering the punch at a speed slower than the first speed, And a third lowering step of the punch subsequent to the second lowering step. The method of claim 1, wherein the pressing step, between the first lowering step and the second lowering step, and between the second lowering step and the third lowering step, the punch in contact with the Mg alloy plate The method of press forming of an electronics case, further comprising falling rest steps for maintaining a stationary state for a predetermined time. The method of claim 1, wherein the forming space is provided with a supporting block which is elastically lowered by the force of the punch, the supporting block, the electronic member, characterized in that the elastically supporting the Mg alloy plate during the pressing step Press molding method of product case. The method according to claim 2, wherein the thickness of the Mg alloy plate is 0.3 ~ 0.9mm, the stop time of the falling pause step is 1 second to 3 seconds, the press molding method of the electronics case. The press molding method of an electronics case according to claim 1, wherein the softening temperature is set at 200 to 350 ° C. The method of claim 1, wherein during the pressing step, the punch and the mold are heated to the same temperature. The press forming method of an electronics case according to claim 1, wherein, during the pressing step, a temperature of the punch is lower than a temperature of the mold within a range of the softening temperature. The method according to claim 1, further comprising the step of conveying the Mg alloy plate in the vicinity of the molding apparatus using a transfer mechanism before the material placement step, in the carrying step, the Mg by a heater installed in the transfer mechanism Press molding method of an electronics case, characterized in that the alloy plate is preheated. The method according to claim 1, further comprising, before the material placing step, preheating the Mg alloy plate on the work shelf for the work stand with a heater installed on the work shelf.

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