JP2008062400A - Mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold which stabilizes the flow viscosity of a molten resin injected and charged in a cavity 30a and forms a plastic sheet component enhanced in dimensional precision. <P>SOLUTION: The cross-sectional shape of the secondary runner in the vicinity of the branch part of a primary runner and the secondary runner both of which allows a resin to flow is made larger than that of the primary runner while the cross-sectional shape in the thickness direction of the secondary runner is formed so as to be continuously retracted up to the vicinity of the gate of the cavity from the vicinity of the branch part of the primary runner and the secondary runner. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a molding die for forming a thin plate-like plastic part.

  Many metal parts used in industrial products have been changed to injection molded plastic parts due to demands for weight reduction and cost reduction. In the industrial products, plate-like plastic parts are used for many purposes such as container lids, partition plates, and windshields. The plate-like plastic parts are not only used in the form of a plate, but also are often used with irregularities, holes, inscriptions, etc. formed for combination with other parts. Such plate-like plastic parts are usually manufactured by injection molding using a molding die.

  An outline of such a conventional molding die will be described based on the drawings. FIG. 6 is a perspective view of a principal part showing a flow path of a molten resin at the time of molding using a conventional molding die, FIG. 7 is a longitudinal sectional view of the principal part, and FIG. 8 is an injection molding using the conventional molding die. The perspective view of the plate-shaped plastic component blank which carried out is shown. 6 and 7, 31 is a primary runner groove, 31a is a tip of the primary runner groove, 32 is a secondary runner groove, 30 is a mold, 30a is a cavity, 30b is a gate groove, and 40 is a primary runner groove. 31 and a lower mold plate in which the secondary runner groove 32 is formed and the mold 30 is incorporated, and 41 is an upper mold plate in which the primary runner groove 31 and the secondary runner groove 32 are formed.

  In FIG. 8, 50 is a molding die, 51 is a sprue, 52 is a primary runner branched from the sprue 51, and 52 a is a tip portion of the primary runner 52. 53 is a secondary runner branched from the primary runner 52, 54 is a gate, 55 is a plate-like plastic part, A is a gate side thickness of the plate-like plastic part, and B is an anti-gate side thickness. C is the width of the plate-like plastic part on the gate side, and D is the width on the opposite gate side.

  Next, the molding operation of the molding die 50 will be described. FIG. 8 shows a state in which the molten plastic is injected and filled into the cavity 30a of the conventional molding die 50 attached to the injection molding machine and clamped by the mold clamping mechanism of the injection molding machine, and the plate-like plastic part 55 is molded. It shows. The molten resin injected from the nozzle of the injection molding machine flows with the sprue 51, the primary runner 52, and the secondary runner 53, reaches the gate groove 30b, and further melts at the tip 52a (primary runner groove tip 31a) of the primary runner 52. Simultaneously with the arrival of the resin, the maximum filling pressure set in advance is reached, and the molten resin fills the cavity 30a at once from the gate groove 30b to form the plate-like plastic part 55.

  In order to form a plate-like plastic part 55 having a thickness thinner than that of a normal molded product, the molding conditions of the injection molding machine are high resin with appropriate resin weighing so that the injected molten resin is completely filled in the cavity 30a. Temperature, higher injection speed, and higher injection pressure are set. The flowing molten resin is cooled and solidified from the portion in contact with the inner surface of the runner groove, the resin viscosity is increased from the outer peripheral portion and the viscosity is increased, so that the flow rate is lowered. The molten resin flows while the low-viscosity portion at the center expands. In many cases, the cross-sectional shape of the secondary runner 53 is reduced more than the cross-sectional shape of the primary runner 52 in order to increase the flow rate.

  However, in the conventional molding die 50, the melted resin low viscosity portion of the secondary runner 53 in the vicinity of the gate groove 30b is small, and the molten resin reaching the maximum injection pressure passes through the gate groove 30b and is injected into the cavity 30a. The Even if the high-flowing low-viscosity molten resin reaches the opposite gate side of the cavity 30a and the cooling and solidification proceeds, the molten resin is not filled in the cavity 30a, and subsequently filled with the high-viscosity molten resin. The maximum filling pressure is generated. Since the cooling and solidification of the non-gate side is progressing, the effect of the maximum filling pressure is generated on the gate side, the resin density on the gate side is increased, and the molding shrinkage on the gate side is small while the molding shrinkage on the gate side is small. Further, the dimensional accuracy has been a problem, for example, the gate side thickness A of the plastic part 55 is larger than the anti-gate side thickness B, and the gate side width C is wider than the anti-gate side thickness width D.

  An object of the present invention is to solve such a conventional problem, and is a thin plate-like plastic having a thick wall thickness in which the flow viscosity of the molten resin injected and filled in the cavity 30a is stabilized and the dimensional accuracy is improved. It is to provide a molding die for forming a part.

  The configuration of the present invention for achieving the above object is that the resin injected from the nozzle of the injection molding machine flows with the sprue, the primary runner, and the secondary runner, and then the resin is supplied from the gate provided on one end face of the cavity. In a molding die that forms a thin plate-shaped plastic part by pouring, the cross-sectional shape of the secondary runner in the vicinity of the branch point between the primary runner and the secondary runner is larger than the cross-sectional shape of the primary runner. To do.

  Moreover, the cross-sectional shape of the secondary runner in the vicinity of the branch point is enlarged in the width direction from the cross-sectional shape of the primary runner.

  Moreover, the cross-sectional shape of the secondary runner in the vicinity of the branch point is enlarged in the thickness direction from the cross-sectional shape of the primary runner.

  Moreover, the cross-sectional shape of the secondary runner in the vicinity of the branch point is formed to be enlarged in the width direction and the thickness direction from the cross-sectional shape of the primary runner.

  FIG. 6 is a cross-sectional view in the thickness direction of the secondary runner. FIG. 7 is a perspective view of a main part showing a flow path of a molten resin at the time of molding using a conventional molding die, FIG. It is characterized in that the shape of a perspective view of a plastic sheet blank made by injection molding using a conventional molding die is continuously reduced from the vicinity of the branch point between the primary runner and the secondary runner to the vicinity of the gate of the cavity. .

  As described above, the molding die for forming a thin plate-like plastic part according to the present invention expands the secondary runner cross-sectional shape in the vicinity of the branch point between the primary runner and the secondary runner through which the resin flows more than the primary runner cross-sectional shape. In addition, the molten runner is injected into the cavity through the gate by continuously reducing the cross-sectional shape of the secondary runner in the thickness direction from the vicinity of the branch point between the primary runner and the secondary runner to the vicinity of the gate of the cavity. It is possible to form a thin plate-like plastic part with a stable flow viscosity and improved dimensional accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1A is a plan view of the main part, and FIG. 1B is a longitudinal sectional view of the main part. 1 (a) and 1 (b), 100 is a molding die, 20a is a cavity for forming a thin plate-like plastic part, 20 is a die in which a cavity 20a is formed, and 10 is a mold in which the die 20 is incorporated. A template, 11 is an upper mold, and 21 is an upper mold. E is an ejector for releasing the runner after molding, 22 is a sprue hole, 25 is a primary runner groove, 25a is a primary runner groove tip, 26 is an air vent, 27 is an air escape groove, and 15 is a secondary runner groove. , 15a and 20b are gate grooves. H1 is the groove width of the primary runner, H2 is the groove width of the secondary runner, T3 is the groove thickness of the primary runner, and T4 is the groove thickness of the secondary runner.

  Next, the operation of the molding die 100 of the present invention will be described. The molten resin injected from the nozzle of the injection molding machine flows from the sprue hole 22 to the primary runner groove 25 and reaches the branch point between the secondary runner groove 15. The groove width H2 of the secondary runner groove 15 is increased with respect to the groove width H1 of the primary runner groove 25, the cross-sectional shape is enlarged, and the flow rate of the molten resin flowing from the primary runner groove 25 to the secondary runner groove is reduced. The secondary runner groove 15 is filled and reaches the gate grooves 15a and 20b.

  At the same time, air in the secondary runner groove 15 and the primary runner groove 25 is discharged from the air vent 26 and the air escape groove 27 provided in the primary runner groove tip 25a, and the molten resin reaches the primary runner groove tip 25a. To do. The molten resin flowing at that time reaches the maximum pressure, passes through the gate grooves 15 a and 20 b, and is injected into the cavity 20 a formed in the mold 20. The low viscosity and high flow molten resin flows through the gate grooves 15a and 20b at high speed and fills the cavity 20a.

  Next, a second embodiment of the present invention will be described. FIG. 2 is a longitudinal sectional view of a main part according to the second embodiment. In FIG. 2, 20a is a cavity for forming a thin plate-shaped plastic part, 20 is a mold in which a cavity 20a is formed, 10 is a lower mold plate for incorporating the mold 20, 11 is an upper mold plate, and 21 is an upper mold. It is a type. 25 is a primary runner groove, 15 is a secondary runner groove, and 15a and 20b are gate grooves. T3 is the groove thickness of the primary runner, and T4 is the groove thickness of the secondary runner. The configuration is the same as that of the first embodiment except for the groove thickness T4 of the secondary runner.

  In the second embodiment of the present invention, the groove thickness T4 of the secondary runner is significantly larger than the groove thickness T3 of the primary runner, so that melting at the branch point between the primary runner groove 25 and the secondary runner groove 15 is achieved. Since the cross-sectional area of the resin is greatly enlarged, the amount of the low-viscosity and high-flowing molten resin flowing in the center of the molten resin is greatly increased, and secondary runner grooves from the vicinity of the branch points to the gate grooves 15a and 20b. By continuously reducing the thickness cross section of 15, the resin flow rate is increased, and a low viscosity high flow molten resin sufficient to be injected and filled into the cavity 20a can be obtained.

  Next, a third embodiment of the present invention will be described. FIG. 3 is a perspective view of a plate-shaped plastic part blank which is injection-molded using the molding die of the present invention. In FIG. 3, 80 is a molding die, 81 is a sprue, 82 is a primary runner branched from the sprue 81, and 82 a is a tip of the primary runner 82. 83 is a secondary runner branched from the primary runner 82, 84 is a gate, 55 is a plate-like plastic part, A is a gate side thickness of the plate-like plastic part, and B is an anti-gate side thickness. C is the width of the plate-like plastic part on the gate side, and D is the width on the opposite gate side.

FIG. 4 is a vertical plan view of the main part of the molding die 80, and FIG. 5 is a cross-sectional view of the main part. 4 and 5, reference numeral 80 denotes a molding die, 20a denotes a cavity for forming a thin plate-shaped plastic part, 20 denotes a die in which a cavity 20a is formed, 10 denotes a lower die plate in which the die 20 is incorporated, 11 Is an upper mold plate, and 21 is an upper mold. E is an ejector for releasing the runner after molding, 22 is a sprue hole, 25 is a primary runner groove, 25a is a primary runner groove tip, 26 is an air vent, 27 is an air escape groove, and 15 is a secondary runner groove. , 15a and 20b are gate grooves. H1 is the width of the groove 25 of the primary runner, H2 is the width of the secondary runner groove 15, T1 is the groove thickness of the primary runner 25, and T2 is the groove thickness of the secondary runner.

  Next, the molding operation of the molding die 80 of the present invention will be described. The width H2 and the thickness T2 of the secondary runner groove 15 are greatly enlarged with respect to the width H1 and the thickness T1 of the groove 25 of the primary runner. Since the flow rate of the molten resin flowing from the primary runner groove 25 to the secondary runner groove 15 decreases, the molten resin that has contacted the inner surface of the runner groove and solidified and increased in viscosity is pressed against the inner surface of the runner groove. The next runner groove 15 is filled with a low viscosity molten resin. Subsequently, the injection pressure is increased, and the low-viscosity molten resin is injected and filled from the gate grooves 15a and 20b into the cavity 20a to complete the molding operation. Since other operations are the same as those in the first and second embodiments, the description thereof is omitted.

  Further, in the embodiment of the present invention, the secondary runner cross-sectional shape in the vicinity of the branch point between the primary runner and the secondary runner of the molding die forming the plate-like plastic part is expanded from the primary runner cross-sectional shape. Enlarging the cross-sectional shape in the middle of the secondary runner after the branch of the secondary runner has the same effect and is included in the structure of the molding die of the present invention.

It is the principal part top view and principal part longitudinal cross-sectional view of the molding die which are 1st embodiment of this invention. It is a principal part longitudinal cross-sectional view of the molding die which is 2nd embodiment of this invention. It is a principal part perspective view of the shaping die which is 3rd embodiment of this invention. It is a principal part top view of the shaping die which is 3rd embodiment of this invention. It is a longitudinal cross-sectional view of the molding die which is 3rd embodiment of this invention. It is a principal part perspective view of the conventional molding die. It is a principal part longitudinal cross-sectional view of the conventional molding die. It is a principal part perspective view of the conventional molding die.

Explanation of symbols

20a, 30a Cavity 50, 80, 100 Mold 20 Mold 21 Upper mold 10, 40 Lower mold plate 11, 41 Upper mold plate 51, 81 Sprue 52, 82 Primary runner 53, 83 Secondary runner 55 Plate plastic Parts 25a, 52a, primary runner groove tip

Claims (5)

  The resin injected from the nozzle of the injection molding machine flows through the sprue, primary runner, and secondary runner, and then injects the resin from the gate provided on one end face of the cavity to form a thin plate-like plastic part. In a molding die, a molding die characterized in that the cross-sectional shape of the secondary runner in the vicinity of the branch point between the primary runner and the secondary runner is formed larger than the cross-sectional shape of the primary runner.   2. The molding die according to claim 1, wherein the cross-sectional shape of the secondary runner in the vicinity of the branch point is formed to be expanded in the width direction from the cross-sectional shape of the primary runner.   2. The molding die according to claim 1, wherein a cross-sectional shape of the secondary runner in the vicinity of the branch point is formed to be larger in a thickness direction than a cross-sectional shape of the primary runner.   2. The molding die according to claim 1, wherein the cross-sectional shape of the secondary runner in the vicinity of the branch point is formed to be expanded in the width direction and the thickness direction from the cross-sectional shape of the primary runner. 4. The molding according to claim 2, wherein the cross-sectional shape in the thickness direction of the secondary runner is continuously reduced from the vicinity of the branch point between the primary runner and the secondary runner to the vicinity of the gate of the cavity. Mold.

Images