JP4874560B2 - Mold - Google Patents

Description

The present invention relates to a molding die for a disk-shaped plastic molded product having a transfer surface such as a tooth portion, a flat surface, a convex shape, or a concave shape on an outer peripheral portion, and particularly relates to improvement of molding accuracy.

  For example, as shown in FIG. 2, when forming a gear 20 in which a cylindrical rim 22 having a tooth portion 21 on an outer peripheral surface, a web 23, and a boss 24 forming a central axis are formed, FIG. As shown in the side cross-sectional view, molten resin is injected and filled into the cavity 10 of the molding die 1 from a plurality of pin gates 11a, and solidified through a cooling process to obtain a molded product. The gate land portion 12a of the pin gate 11a for filling the cavity 10 with the molten resin is provided perpendicular to the web surface forming the cavity 10, as shown in the partial enlarged view of FIG. The molten resin thus obtained reaches the outer periphery of the cavity 10 while spreading radially around the gate land portion 12a of each pin gate 11a as shown in the plan sectional view of FIG. When the molten resin filled from the gate land portion 12a of the pin gate 11a flows in the cavity 10, the molten resin merges between the gate land portions 12a of the adjacent pin gates 11a, and a weld line W is inevitably formed in that region. appear. The weld line W greatly affects the shape of the tooth trace surface 21 a of the formed gear 20. As shown in FIG. 12, the tooth trace surface 21 a corresponding to the weld line W is radiated across the center of the cavity 10. Compared with the tooth trace surface 21a corresponding to the gate line G connecting the pin gates 11a facing each other across the center of the cavity 10 of the provided pin gate 11a, the inclination becomes larger, causing a reduction in the shape accuracy of the gear 20. Yes.

In order to reduce the influence of the weld line on the shape of the gear, as shown in Patent Document 1, a plurality of small cylinders are parallel to the axis of the gear on the radial line from the pin gate to the outer periphery of the gear in the cavity of the mold. In addition to the weld line by the pin gate, a weld line by a small cylinder is also formed to equalize the flow direction of the molten resin in the circumferential direction.
JP 10-34762 A

  However, as shown in Patent Document 1, even if the weld line is increased and the flow direction of the molten resin is equalized in the circumferential direction, the weld line is radially formed from the center of the cavity in the circumferential direction. The shape of the molded tooth trace surface is inclined, and the influence on the accuracy of the molded product is inevitable.

  In order to prevent this weld line from occurring, there is a method using a disk gate. In this method, unlike the pin gate, the gate is automatically cut when the mold is opened and closed. This requires a secondary processing step, resulting in poor productivity and a significant disadvantage.

The present invention improves such disadvantages and reduces the influence of the generated weld line on the accuracy of the molded product in the molding of a disc-shaped molded product using a pin gate, thereby producing a highly accurate molded product. An object of the present invention is to provide a mold that can be formed.

Flow molding die of the present invention, in the molding die by injection filled in the cavity for molding the disk-shaped molded article by a plurality of pin gate molten resin, in the circumferential direction with respect to the molten resin injected into key Yabiti It has a flow direction restricting portion for applying a component, and the flow direction restricting portion is formed of an inclined shape portion formed on a surface forming a cavity facing the gate land portions of a plurality of pin gates .

  The flow direction restricting portion is formed by inclining gate land portions of a plurality of pin gates at a fixed inclination angle with respect to a surface forming a cavity.

  Further, it is desirable that a plurality of pin gates are arranged at equal intervals on the same circumference centering on the center of the cavity, and the inclined gate land portions are arranged along a circumference connecting the plurality of pin gates. .

  Further, it is preferable that the pin gate and the gate land portion are formed in a nested manner so that the gate land portion can be replaced with a gate land portion having a different inclination angle.

The present invention provides a cavity for a molten resin flowing in a cavity by injecting a molten resin filled in the cavity with a flow component along the circumferential direction when the disk-shaped molded product is molded. The tangential flow is given to the outer peripheral surface of the mold, and the weld line can be formed in an arc shape oblique to the radial direction of the cavity, and the influence on the outer peripheral shape of the molded product is remarkably reduced, and high accuracy A molded product can be formed.
In addition, by providing the flow component along the circumferential direction to the molten resin by the inclined shape portion formed on the surface forming the cavity facing the gate land portion of the plurality of pin gates, the inclination angle and shape of the inclined shape portion The flow component according to the outer peripheral surface shape of the molded product to be molded with respect to the molten resin can be given, and molded products having various outer peripheral surface shapes can be accurately molded.

  In addition, by tilting the gate land portion of the pin gate with a constant inclination angle with respect to the surface forming the cavity, the flow component along the circumferential direction is given to the molten resin with a simple configuration. Thus, a flow component along the circumferential direction can be provided.

  Furthermore, a plurality of pin gates are arranged at equal intervals on the same circumference centered on the center of the cavity, and the gate land portions formed by tilting are arranged along the circumference connecting the plurality of pin gates, thereby melting. Resin can be made to flow uniformly in the cavity, and arc-shaped weld lines can be formed uniformly to form a highly accurate molded product.

  In addition, by forming the pin gate and the gate land part in a nested manner and making it interchangeable with the gate land part having a different inclination angle, a flow component corresponding to the outer peripheral surface shape of the molded product to be molded with respect to the molten resin is given. It is possible to mold various outer peripheral surface shaped products with high accuracy.

  FIG. 1 is a sectional view showing a molding die of the present invention. As shown in the cross-sectional view of FIG. 2, for example, the molding die 1 shown in the figure is integrally formed with a cylindrical rim 22 having a tooth portion 21 on the outer peripheral surface, a web 23, and a boss 24 forming a central axis. The synthetic resin gear 20 is formed, and is a split mold having a fixed mold 2 and a movable mold 3. The fixed mold 2 has a cavity insert 5 inside the cavity plate 4. The movable mold 3 has a core insert 9 having a gear piece 7 for forming the tooth portion 21 of the gear 20 and a center core pin 8 for forming the boss 24 inside the core plate 6. A cavity 10 having a predetermined volume is formed by the cavity insert 5 and the core insert 6 of the fixed mold 3. A plurality of pin gates 11 are provided radially with respect to the center of the cavity 10 with respect to the cavity insert 5 of the fixed mold 2 in order to inject and fill the cavity 10 with molten resin from the injection part of the injection molding machine.

  As shown in the partial cross-sectional view of FIG. 3B, the gate land portion 12 for injecting the molten resin into the cavity 10 of the pin gate 11 provided in the cavity insert 5 is in relation to the web surface on the inner surface of the cavity insert 5. For example, as shown in the plan view of FIG. 3A, the inclination direction is the circumference of a circle 13 connecting a plurality of pin gates 11 provided radially with respect to the center of the cavity 10. It is formed along.

  When molten resin is injected and filled from the pin gate 11 into the cavity 10, the injected molten resin has a flow component along the circumferential direction in the cavity 10, and flows almost tangentially on the outer peripheral surface of the cavity 10. For this reason, the weld line W has an arc shape oblique to the radial direction of the cavity 10 as shown in FIG. 3A, and is not a straight line but a spiral with respect to the tooth portion 21 which is the outer peripheral surface. The influence on the outer peripheral shape can be significantly reduced. Therefore, the shape of the tooth trace surface of the formed gear 20 can be prevented from being inclined, and the highly accurate gear 20 can be formed.

  In the above description, the case where the gate land portion 12 provided at a certain angle on the pin gate 11 is formed along the circumference of a circle 13 connecting a plurality of pin gates 11 provided radially with respect to the center of the cavity 10 will be described. However, as shown in the plan view of FIG. 4, even if the gate land portion 12 is formed inward from a circle 13 connecting a plurality of pin gates 11 provided radially with respect to the center of the cavity 10, the cavity 10 A flow component along the circumferential direction can be given to the molten resin injected into the arc, and the weld line W is formed in an arc shape oblique to the radial direction of the cavity 10 to reduce the influence on the shape accuracy of the outer peripheral portion. Can do.

  Further, in the above description, the case where the web 23 of the gear 20 is formed flat has been described. However, as shown in the cross-sectional view of FIG. The cavity 10 may be formed in a step shape by providing a step at a predetermined diameter position of the core insert 9. Thus, by providing a step in the cavity 10, the flow reach distance to the outer peripheral surface of the molten resin can be increased, the influence of the weld line W can be further reduced, and the gear 20 having a highly accurate shape can be obtained. Can be molded.

  Although the case where the pin gate 11 is provided in the cavity insert 5 of the fixed mold 2 has been described, the pin gate 11 may be formed in a gate insert 14 that is detachable from the cavity insert 5 as shown in FIG. good. Thus, by providing the pin gate 11 in the gate insert 14 so that it can be exchanged for the cavity insert 5, the gate insert 14 having the gate land portions 12 having different inclination angles α with respect to the web surface can be arbitrarily produced. The molten resin that flows into the cavity 10 can be selected by selecting the gate insert 14 having the gate land portion 12 having a different inclination angle α according to the influence of the weld line W on the outer peripheral surface shape of the molded product and attaching the gate insert 14 to the cavity insert 5. The flow direction can be changed as appropriate.

  In the above description, the case where the flow component along the circumferential direction is given to the molten resin flowing in the cavity 10 by inclining the gate land portion 12 of the pin gate 11 has been described, but the plan view of FIG. 7A and FIG. As shown in the partial cross-sectional view, at the position of the core insert 9 facing the gate land portion 12a of the pin gate 11a having the gate land portion 12a formed perpendicular to the web surface, the direction perpendicular to the radial direction or the direction thereof An inclined shape portion 15 having an inclined surface facing more inside may be provided. Thus, by providing the inclined shape portion 15 at a position facing the gate land portion 12a, a flow component along the circumferential direction can be given to the molten resin injected from the gate land portion 12a into the cavity 10. The inclination angle of the inclined portion 15 may be appropriately selected according to the influence of the weld line W on the outer peripheral surface shape of the molded product.

  In the above description, a flow component along the circumferential direction is given to the molten resin injected from the pin gate 11a having the gate land portion 12a formed perpendicular to the web surface of the inner surface of the cavity insert 5 by the inclined shape portion 15. Although the case has been described, as shown in FIG. 8, an inclined shape portion 15 may be provided to face the gate land 12 of the pin gate 11 having the gate land portion 12 formed to be inclined with respect to the web surface. By providing the pin gate 11 having the gate land portion 12 formed so as to be inclined with respect to the web surface and the inclined shape portion 15 in this way, the flow component along the circumferential direction is more reliably applied to the molten resin injected into the cavity 10. The molten resin is filled while flowing so as to rotate in the cavity 10, and the weld line W can be spiral instead of being aligned with the outer peripheral surface. 21 can be significantly reduced.

  In the above description, the gear 20 is formed. However, as shown in the cross-sectional view of FIG. 9, the same applies to the disk-shaped molded products 25a, 25b, and 25c whose outer peripheral portions are flat, convex, or concave. By applying, a molded product 25 having a highly accurate shape can be produced. The injection molding machine can be applied to both vertical and horizontal types.

  FIG. 10A shows the result of examining the inclination of the tooth trace surface of the produced gear 20 by molding the gear 20 with a thermoplastic resin such as polyacetal using the molding die 1 shown in FIG. . For comparison, FIG. 10B shows the result of examining the inclination of the tooth trace surface of the produced gear 20 by molding the gear 20 using the same material using a conventional molding die. As shown in FIG. 10, the inclination of the tooth trace surface of the gear 20 produced with the conventional molding die was greatly inclined at the position corresponding to the weld line, but the gear produced with the molding die 1 shown in FIG. The inclination of the tooth trace surface of 20 can be greatly reduced at both the position corresponding to the weld line and the position corresponding to the gate part line G, and the high-precision gear 20 can be manufactured.

It is sectional drawing which shows the shaping die of this invention. It is sectional drawing which shows the gearwheel shape | molded with a shaping die. It is a figure which shows the structure and arrangement | positioning of a pin gate and a gate land part. FIG. 10 is a layout diagram of another pin gate and a gate land portion. It is sectional drawing which shows the structure of another shaping die. It is sectional drawing which shows the structure of a nesting type pin gate and a gate land part. It is a figure which shows the structure and arrangement | positioning of the inclination shape part provided in the movable metal mold | die. It is a block diagram of another pin gate and an inclined shape part. It is sectional drawing which shows the structure of the other molded article to shape | mold. It is a change characteristic figure which shows the inclination of the tooth trace surface by the Example of this invention, and a prior art example. It is a block diagram of the conventional molding die. It is a schematic diagram which shows the inclination of the tooth trace surface of the gear shape | molded with the conventional metal mold | die.

Explanation of symbols

1; Mold, 2; Fixed mold, 3; Movable mold, 4; Cavity plate,
5; cavity insert, 6; core plate, 7; gear piece, 8; center core pin,
9; Core insert, 10; Cavity, 11; Pin gate, 12; Gate land part,
14; gate nesting, 15; inclined shape part, 20; gear, 21; tooth part, 22; rim,
23; Web, 24; Boss.

Claims (4)

In a molding die that molds a disk-shaped molded product by injecting and filling molten resin into the cavity with multiple pin gates,
Has a flow direction regulating portion to provide a flow component in the circumferential direction with respect to the injected molten resin key Yabiti,
The flow direction restricting portion is formed of an inclined shape portion formed on a surface forming a cavity facing a gate land portion of a plurality of pin gates .   The molding die according to claim 1, wherein the flow direction restricting portion is formed by inclining gate land portions of a plurality of pin gates at a constant inclination angle with respect to a surface forming a cavity.   The plurality of pin gates are arranged at equal intervals on the same circumference centering on the center of the cavity, and the inclined gate land portions are arranged along a circumference connecting the plurality of pin gates. Molding mold. The molding die according to claim 2 or 3, wherein the pin gate and the gate land portion are formed in a nesting manner so as to be exchangeable with gate land portions having different inclination angles .

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