JP2002240113A - Method for injection molding extra-thin container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To thin a body bottom of an extra-thin container by extrapolating an unfilled part generated from a difference of a flowing speed of a resin flow by a core with an excess resin generated by a compression. SOLUTION: A mold 1 having a shallow bottom cavity 2 for molding the extra-thin container body 10 and the core 3 for molding a body inner surface in the cavity is used. A method for injection molding the extra-thin container comprises the step of movably projecting the core 3 in the cavity except a compression margin of 2 to 5 times as large as a thickness of a body bottom. A side gate 5 is provided at the cavity 2. The method further comprises the steps of injection filling the resin 6 in the cavity 2 from the side gate 5, and primarily molding a body edge 11 and a thick body bottom by the core 3. The method also comprises the step of stopping injection filling of the resin 6 when centers of the body bottom of an opposite side to the gate 5 and the body edge are disposed at flowing spaces 7, 8 in an incomplete state. The method also comprises the steps of compression molding the thick body bottom to an extra-thin thickness by the core 3, and simultaneously extruding the excess resin in the spaces 7, 8 the extrapolate the resin of an uncompleted part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injection molding a case-shaped container having a very thin main body.

[0002]

The case-shaped container used to house an IC module, a flash memory and the like is required to be extremely thin, having a thickness of 1.0 mm or less, in accordance with the miniaturization of electronic equipment. In order to secure sufficient volume, it is necessary to form the bottom surface with a small thickness.

[0003] For molding an ultra-thin container, a mold is used which comprises a shallow cavity for molding the outer surface of the main body, and a movable core for molding the inner surface of the main body protruding from the cavity while leaving a compression allowance. A method in which the resin injected and filled in the cavity is compressed by the core to make the bottom surface of the main body thinner can be adopted.

[0004] In this molding method, the influence of flow resistance and the like caused by the flow of resin due to the core during injection filling is small, and the space at the end of the cavity generated before compression is reduced due to the limitation of the amount of resin to be filled. Since the excess resin generated by the compression is filled, an ultra-thin container having a uniform bottom wall thickness can be obtained. However, all the excess resin generated by being pressed by the core is located in the downstream cavity. Since it is not extruded to the end portion but flows back to the upstream gate side, the downstream molding tends to be unstable.

In addition, as long as the core protrudes into the cavity and the resin is injected and filled from the gate toward the core,
Flow resistance and flow friction are generated by the core, causing a difference in the flow rate of the resin flow between the lower side of the core and the flow of the resin on both sides of the core. A short shot due to the filling delay under the core is inevitable. In addition, it is difficult to form an ultra-thin container having a bottom area of 2 cm ² or more into an ultra-thin wall of 0.3 mm or less by the above-mentioned conventional molding method. Defects such as warping and twisting due to twisting and gas burning occurred, and molding of good products could not be expected.

The present invention has been conceived in order to solve the above-mentioned conventional problems, and an object of the present invention is to remove an unfilled portion, which tends to occur due to a difference in the flow speed of a resin flow by a core, by using a surplus generated by compression. It is an object of the present invention to provide a new ultra-thin container injection molding method in which the bottom of the main body is formed to be extremely thin and the inside of the container can be formed deep by complementing with a resin.

[0007]

According to the present invention, there is provided a mold having a shallow cavity for molding an extremely thin container body and a core for molding an inner surface of the body in the cavity. Is movably protruded into the cavity leaving a compression allowance of 2 to 5 times the thickness of the bottom surface of the main body, forming a molding space around the core around the core and a wide side at the center of the cavity side. A gate is provided, resin is injected and filled into the cavity from the side gate,
Primary molding of the body edge and the thick body bottom with the core,
The injection filling of the resin is stopped when the bottom surface of the main body on the opposite side to the side gate and the center part of the main body edge are in an unfinished state and there is a flow space, and in that state, the thick main body bottom surface is made extremely thin by the core. At the same time as the compression molding, the surplus resin is extruded into the flow space to supplement the unfinished portion of the resin.

According to the present invention, an overflow tab is provided at a portion of the cavity facing the side gate,
The compression molding of the recess by the core is performed by setting the injection pressure to zero and refilling the resin after the compression molding. Further, in the present invention, the injection molding is performed by a pre-plastic injection molding machine.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference numeral 1 in FIG.
As shown in 1), a cavity mold made of a split mold, and an extremely thin container body 10 having a quadrilateral planar shape and a thickness of 1.0 mm or less (see FIG. 5) is formed on a parting surface of the split mold. ) Are respectively recessed.

Reference numeral 3 denotes a core for molding the inner surface of the main body.
Of a flat cross section of a size that forms the molding space 4 of the main body, leaving a compression allowance of 2 to 5 times the thickness of the bottom surface 12 of the main body,
It is movably protruded inside the cavity 2 from one split mold to the other split mold.

Reference numeral 5 denotes a gate of the cavity 2, which is provided wide at the center of the cavity side.
Resin 6 injected into cavity 2 by injection
Flows into the lower side and both sides of the core 3 and fills up to the end of the cavity opposite to the gate.

Since there is a difference in flow friction between the lower side of the core where the flow gap is small and restricted by the core 3 and both sides of the core where there is no restriction, the resin flow 6
The flow velocity a becomes slower than the resin flows 6b, 6b on both sides of the core, and as shown in FIGS. 1 (A2) and (B2), there is a difference between the tip positions (front flows) of both resin flows.

In this state, if resin filling is continued as in the prior art, the resin flows 6b, 6b on both sides of the core merge together at the end of the cavity 2 to form a weld line, or air flows downstream of the core. Then, an unfilled portion is generated, and a window hole a as shown in FIG.

Therefore, injection filling of the resin 6 is performed as shown in FIG.
As shown in (B3), the flow space 7,7 is formed between the downstream side below the core on the bottom surface of the main body, which is incompletely thickly formed by the core 3 while being incomplete, and the front end of the resin flow 6b on both sides of the core. Stop when 8 remain and both are incomplete,
Before the resin loses fluidity, the core 3 is compressed and the bottom surface 12 of the main body is compression-molded to an extremely thin wall having a bottom thickness of 0.5 mm or less.

The timing of stopping the injection filling is preferably controlled by the position of the injection screw or plunger of the injection molding machine used for molding, and the compression molding time has an accuracy of 1/10.
It is preferable to use a 00 second timer.

Preferably, the injection pressure is temporarily set to zero during compression molding, and the backflow of the resin 6 on the upstream side due to the compression force leaks from the side gate 5 to the molding machine through the runner sprue and the nozzle (see FIG. 4). In this way, it is preferable to perform depressurization to reduce the influence of residual stress, and to perform refilling after compression. Thereby, even a very thin container is unlikely to be warped or twisted.

Due to the compression of the core 3, the thickness of the main body bottom surface 12, which has been thick, becomes extremely thin (for example, 0.3 mm or less). Will be extruded around. Since the flow spaces 7, 8 remain on the downstream side, the surplus resin presses the resin 6b, 6b on both sides of the core from the inside at the same time as the compression, and pushes out the resin to the flow space 8, and at the same time, the lower side of the recessed core Of the resin 6b, 6b from both sides by filling the narrowed flow space 8 from the inside.
Complement between the tips.

As a result, the unfilled portion on the downstream side of the bottom surface of the main body formed temporarily is eliminated, and the thickness distribution of the main body bottom surface 12 falls within ± 1/100 while the thickness of the main body bottom surface 12 is extremely thin. As shown in FIGS. 1 (A4) and (B4), it is possible to obtain an ultra-thin container in which the problem of welding due to the merging of the resin flows on both sides of the core with each other is eliminated.

FIG. 2 shows that an overflow tab 9 is provided in the cavity 2 at a position facing the side gate 4, and excess resin generated by compression by the core 3 is further pushed out to the overflow tab 9 to make the flow of the excess resin smooth. This ensures that the unfinished portion is complemented and that the strength of the weld is improved, and that warpage and twisting due to residual stress are prevented.

FIG. 3 shows the thin-walled container 10 having the double edge shown in FIG.
The periphery of the mold surface on the core insertion side of the cavity 2 is defined by a ridge 2a, and an outer edge molding space 4a is formed by the cavity mold surface and the ridge outer surface, and the ridge 2a is formed. The core 3 is movably inserted into the cavity opening formed by the inner space with the inner edge forming space 4b being provided between the core 3 and the inner surface of the ridge, and the core 3 is provided in the cavity 2 together with the ridge 2a. In such a mold 1, the outer edge 11a and the inner edge 11b of the thin-walled container 10 can be formed simultaneously at the boundary of the ridge 2a, and the edge 11 of the main body can be partially formed into a double edge by the arrangement of the ridge 2a. it can.

FIG. 4 shows an example in which the injection molding method according to the present invention is carried out by employing a pre-plastic injection molding machine. The pre-pla injection molding machine includes an injection device 24 having a plunger moving device 23 at a rear portion of an injection cylinder 22 in which an injection plunger 21 is freely movable.
A plasticizing device 28 provided with a screw moving and rotating device 27 is provided at a rear portion of a plasticizing cylinder 26 in which a screw 25 for plasticizing is rotatably mounted. , Resin path 2 with open / close valve provided over the outflow path at the tip of the plasticizing cylinder
9 is a communication configuration.

The pre-plastic injection molding machine exemplified here is:
The tip of the screw 25 is formed on the opening / closing valve 30,
The screw 25 is rotatably and retractably mounted on a plasticizing cylinder 26, and the screw 25 is moved forward and backward so that the resin path 2 is formed.
9 is opened and closed, but a structure in which a rotary valve is attached to the resin path 29 to perform opening and closing operations can also be employed.

In this pre-plastic injection molding machine, the resin plasticized by the rotation of the screw is filled into the front part of the plunger of the injection cylinder 22 from the resin path 29 and measured, and after the measurement, the valve 30 is closed by advancing the screw to plasticize. When the plunger 21 moves forward after being shut off from the device side,
The metering resin at the front of the plunger dispenses sprue 3
After passing through the mold 2 and the runner 33, the cavity 2 is injected and filled from the side gate 5 of the mold 1 whose mold is closed.

In the mold, the hydraulic cylinder 34 for compression is activated almost simultaneously with the end of the injection filling, and the core 3 fixed on the pressing plate 36 is pushed out into the cavity by the ram 35, which is omitted in the figure. However, the thickness of the injection-molded thick bottom of the main body is reduced, and an ultra-thin container 10 capable of accommodating an IC module or the like is formed.

In such an injection means, since the measurement error of the resin is extremely small and there is almost no leakage of the measurement resin at the time of injection, the plasticization of the resin and the injection filling can be freely rotated and advanced into and out of the injection cylinder. Than when adopting an inline screw type injection molding machine that performs with the installed injection screw,
Since the injection filling amount at the time of stopping during injection is stable, the product also has a high wall thickness distribution and high molding accuracy.

[0026]

[Example] Material resin PC, PC + ABS alloy, PBT, etc. Molding machine FN1000 / TM3UH (manufactured by Nissei Plastic Industry Co., Ltd.) Container area 3.2 × 2.4 cm ² Thickness 1.2 mm Volume 0.6 cm ³ Bottom area 2 0.7 × 2.2cm ² Bottom wall thickness 0.15mm Cavity volume 0.3cm ³ Compression allowance 0.50mm Resin amount 0.3g Injection speed 1000mm / sec Injection pressure 1200Kgf

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an injection molding method of the present invention in the order of steps, wherein (A) is a schematic plan view of a mold, and (B) is a schematic longitudinal sectional view of the mold.

FIG. 2 is a schematic plan view (A) of a mold according to another embodiment of the present invention and a schematic longitudinal sectional view (B) of the mold.

FIG. 3 is a schematic plan view (A) of a mold and a schematic longitudinal sectional view (B) of the mold that can apply the present invention to the formation of the ultra-thin container with a double edge shown in FIG.

FIG. 4 is a longitudinal sectional view of a pre-plastic injection molding machine and a mold used for carrying out the injection molding method of the present invention.

FIG. 5 is a perspective view of an ultra-thin container to be injection-molded according to the present invention.

FIG. 6 is a perspective view of a double-edge ultrathin container to be injection-molded according to the present invention.

FIG. 7 is a perspective view of an ultra-thin container by a conventional injection molding method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Mold 2 Cavity 3 Core for molding the inner surface of main body 4 Molding space at the periphery of main body 5 Side gate 6 Resin 6a Resin flow under core 6b Resin flow on both sides of core 7 Flow space downstream of bottom of main body 8 Flow at end of cavity Space 9 Overflow tab 10 Ultra-thin container 11 Body edge 12 Body bottom 21 Plunger for injection 24 Injection device 25 Screw for plasticization 27 Plasticization device 29 Resin path

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshiteru Kadoya 2856 Shiratsuka-cho, Tsu-shi, Mie Asahi Denki Kogyo Co., Ltd. (72) Inventor Yoshinori Inagaki 2856 Shiratsuka-cho, Tsu-shi, Mie Asahi Denki Co., Ltd. (72) Inventor Koichi Kato 2856 Shiratsuka-cho, Tsu City, Mie Prefecture Inside Asahi Denki Kogyo Co., Ltd. (72) Inventor Akinobu Kawade 2856 Shiratsuka-cho, Tsu City, Mie Prefecture Asahi Denki Kogyo Co., Ltd. (72) Invention Person Masamichi Nakayama 60, Kita-Shinkai, Yokkaichi, Mie Pref.Matsushita Electric Works, Ltd., Electronic Materials Branch (72) Inventor Yoshinori Toyoda 60, Kita-Shinkai, Yokkaichi, Mie Matsushita Electric Works, Electronic Materials In-house (72) Inventor Masaaki Minamimura 21110 Nanjo, Ojo, Sakajo-cho, Hanishina-gun, Nagano Prefecture Inside Nissei Plastic Industry Co., Ltd. (72) Inventor Bunka Nagaya, Hanishina-gun, Nagano Prefecture 2110, Nanjo-cho, Nissei Jushi Kogyo Co., Ltd. CK06 CK18 CP10 4F206 AA25 AA28 AH56 AR03 AR12 AR14 JA03 JD05 JQ86 JQ90

Claims (4)

[Claims] 1. A mold comprising a shallow cavity for molding an ultra-thin container body and a core for molding the inner surface of the body in the cavity, wherein the core is 2 to 5 times the thickness of the bottom surface of the body. Movably protruding into the cavity leaving the compression allowance, forming a molding space around the core around the core, and providing a wide side gate in the center of the cavity side, and the resin from the side gate to the cavity The main body edge and the thick main body bottom are primarily molded by the core, and the resin is injected and filled with the flow space while the main body bottom and the center part of the main body edge opposite to the side gate are incomplete. It stops when there is, and in that state, at the same time as the above-mentioned core, the thick bottom surface of the main body is compression-molded to an extremely thin thickness, and at the same time, the excess resin is extruded into the above-mentioned flowing space to complement the incomplete portion of the resin. Characteristic injection molding method for ultra-thin containers. 2. The injection molding method for an ultra-thin container according to claim 1, wherein an overflow tab is provided at a portion of the cavity facing the side gate. 3. The ultra-thin container according to claim 1, wherein the compression molding of the bottom surface of the main body by the core is performed by setting an injection pressure to zero and refilling the resin after the compression molding. Injection molding method. 4. The injection molding method for an ultra-thin container according to claim 1, wherein said injection molding is performed by a pre-plastic injection molding machine.