JP2001150491A - Method for dichroically molding and mold used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dichroic molding obtained by rigidly integrating a primary molding with a secondary molding in compact steps at a low cost. SOLUTION: The method for dichroically molding comprises the steps of clamping a movable common mold 20 having a secondary molding cavity 25 and a core pin 26 for forming a through hole 2 at a first fixed mold 30 having a slide core 33 for forming a primary molding cavity 35 around the pin 26, filling a first resin, primarily molding the resin, then opening the mold, moving the mold 20 in a state in which a primary molding 3 is held at the pin 26, clamping the mold 20 with a second fixed mold 40 having a secondary side mold plate 43 including a pin hole 44 to be engaged with the front end of the pin 26, thereby inserting the molding 3 into the cavity 25 along the pin 26, and filling a second resin to form the secondary molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for performing two-color molding including two-material (different-material) molding by injection molding of a synthetic resin, and a mold used therefor.

[0002]

2. Description of the Related Art In general, when a synthetic resin is injection-molded to produce a high-precision gear, a polyacetal resin (POM) is often used as a resin material in view of lubricity, strength and cost. Because of the large shrinkage of this material, it cannot be made into a thick-walled structure, and it is manufactured in such a way that the web portion is lightened or ribs are added. However, when the above-mentioned lightening is performed, the core shape of the mold becomes complicated, resulting in high cost,
In addition, when the reinforcing ribs are provided, not only the core shape becomes complicated, but also complicated deformation is caused by the difference in the flow and partial shrinkage of the resin, and it is difficult to obtain a highly accurate product.

In order to solve the problem of shrinkage, there is a method in which a gear is manufactured by two-color molding using a two-color (or two-material) molding device of a mold rotating plate type.
In conventional two-color molding, a secondary molded body having a tooth profile is integrally formed on the outer peripheral portion of a simple short cylindrical primary molded body having no undercut portion due to its ease of molding. Therefore, one or both of the primary molded product and the secondary molded product are made of adhesive (affinity) such as polyacetal resin.
When the resin is formed of a resin having a low viscosity, the two molded bodies do not adhere to each other, so that the two molded bodies are displaced or separated from each other, so that there is a problem that they cannot be put to practical use. Also, there is a method of setting a preformed primary molded part in a mold and performing insert molding.However, in this case, it is necessary to insert the primary molded part into the die manually or by a robot. However, there is a problem that the manufacturing cost is high because of poor performance and high equipment cost.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned conventional problems, and provides a two-color molded article in which a primary molded article and a secondary molded article are firmly integrated in a simple process. An object of the present invention is to provide a two-color molding method which can be obtained at a low cost and a mold used for the method.

[0005]

The two-color molding method according to the present invention is a two-color molding method for injection-molding a secondary molded body on an outer peripheral portion of a primary molded body having a through hole at a central portion, the secondary-color molding method comprising: A common movable mold having a molding cavity and the core pin for forming the through-hole is clamped to a first fixed mold having a slide core for forming a primary molding cavity around the core pin at the time of mold clamping, and the primary molding cavity is clamped. The primary molding cavity is filled with the first resin in a state in which the opening of the first movable body is closed by the slide core, and after the primary molding, the mold is opened, and the primary molded body is held by the core pin portion. Is moved to a second fixed mold having a secondary mold plate having a pin hole into which the tip of the core pin fits, and the primary molding is moved along the core pin by the mold clamping. The secondary molding body is inserted into the secondary molding cavity, the opening of the secondary molding cavity is closed by the secondary mold plate, and the secondary molding is formed by filling the secondary molding cavity with the second resin. It is characterized by obtaining a color molded product.

Further, the two-color molding die of the present invention is a two-color molding die for injection-molding a secondary molded body on an outer peripheral portion of a primary molded body having a through hole at a center portion, and comprises a split mold. It comprises a common movable mold forming one, and first and second fixed molds forming the other of the split molds and alternately clamping to the common movable mold, wherein the common movable mold has a secondary molding cavity and And a core pin for forming a through hole, wherein the first fixed type comprises:
A sliding core that forms a primary molding cavity around the core pin and closes an opening of the secondary molding cavity at the time of mold clamping in conjunction with mold clamping; and wherein the second fixed mold has a tip portion of the core pin. A secondary side mold plate that has a pin hole into which the secondary molding cavity is fitted and closes an opening of the secondary molding cavity when the mold is clamped with the common movable mold, and defines one side surface of the secondary molding cavity. And

According to the present invention, since the primary molding is performed by the first fixed die having the slide core, the primary molded body is formed into a desired shape such as an undercut shape which is effective for preventing the secondary molded body from slipping. Thereby, even with a resin having low adhesiveness, the primary molded body and the secondary molded body can be firmly integrated, and the cross-sectional shape of the secondary molded body has a shape with less shrinkage and distortion due to the secondary molding. By selecting the shape of the primary molded body so as to make it possible to obtain a two-color molded product with high molding dimensional accuracy, such as a high-precision gear. Also, since the primary molded body held by the core pin portion is inserted into the secondary molding cavity along the core pin by the secondary mold plate at the time of mold clamping with the second fixed die, the primary molded body Insertion into the next molding cavity can be performed quickly and easily without using special equipment such as humans and robots.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2, reference numeral 1 denotes a gear which is a two-color molded product obtained by the present invention, and a web is constituted by a primary molded body 3 having a through hole 2 for inserting a shaft at a center portion. A tooth profile 4a is constituted by a secondary molded body 4 integrally formed on the outer peripheral portion of the body 3. In this example, the primary molded body 3 is formed by injection molding a polyacetal resin containing glass fiber, and the secondary molded body 4 is formed by injection molding a polyacetal resin. The primary molded body 3 has an undercut shape having a large-diameter portion 3a at the center in the width direction of a short cylindrical body having the through-hole 2, and the secondary molded body 4 has both sides of the large-diameter portion 3a and It is formed in a U-shaped cross section surrounding the outer peripheral surface. 3b is a groove recessed at two places in the large-diameter portion 3a of the primary molded body 3, and together with the ridges 4b formed on the secondary molded body 4 so as to flow into the groove 3b at the time of secondary molding. It functions as a detent.

3 to 5, reference numeral 10 denotes a mold provided with a slide type movable die similar to the slide type used in the two-color molding method, and is traversed on a movable platen 11 of an injection molding machine (not shown). Common movable mold 20 freely mounted and fixed platen 1
The common movable mold 20 includes a first fixed mold 30 and a second fixed mold 40 attached to the second fixed mold 2, and the common movable mold 20 is alternately clamped (and opened) by the first fixed mold 30 and the second fixed mold 40.

The common movable mold 20 includes a movable side mounting plate 21 supported on the movable platen 11 so as to be able to traverse freely.
The receiving mold plate 23 and the movable mold plate 24 are attached to each other via the second mold cavity 24. The movable mold plate 24 is provided with a secondary molding cavity 25 having a tooth profile forming portion 25a on the outer peripheral portion, and the primary molded body described above. 3 core pin 2 for forming through hole 2
6 is fixedly provided so as to penetrate the center of the secondary molding cavity 25 and have a tip 26a projecting more than the opening 25b of the cavity. 27a and 27b are projecting plates, and 28 is a projecting pin having a base mounted on these projecting plates, for projecting a two-color molded product after secondary molding described later.

Next, the first fixed die 30 includes a primary fixed side mounting plate 31 fixed to the fixed platen 12, a primary runner plate 32, and a slide supported by the runner plate so as to be able to traverse in the direction of arrow X. The slide cores 33, 33 are driven by angular pins 34, 34 having bases fixed to the primary fixed side mounting plate 31 in directions approaching each other at the time of mold clamping. 2
6, a primary molding cavity 35 for forming the primary molded body 3 is formed. That is, the leading end portions (mutual butting portions) of the slide cores 33, 33 are provided in FIG.
As shown by a dashed line, a cavity of a die-sinking surface corresponding to a shape obtained by dividing the primary molded body 3 into two by a dividing surface 36 passing through the center thereof is provided. 37 is a primary side nozzle, and 38 is a primary side runner.

The second fixed mold 40 includes a secondary fixed-side mounting plate 41 fixed to the fixed platen 12, a secondary runner plate 42, and a secondary mold plate 43. Board 4
A pin hole 44 into which the tip 26a of the core pin 26 is fitted is formed at the center of the core pin 3, and a facing surface 43a facing the common movable mold 20 has a flat shape in this example.
45 is a secondary nozzle and 46 is a secondary runner.

Next, a description will be given of a two-color molding method using an injection molding machine provided with the above-mentioned mold 10. First, as shown in FIG. 3, the common movable mold 20 is clamped to the first fixed mold 30, and this mold clamping is performed. The slide cores 33, 33 are driven in a direction approaching each other in conjunction with each other to form a primary molding cavity 35 around the core pin 26 of the common movable mold 20, and the primary resin 39 for primary molding is supplied to the primary nozzle 37. , And is filled into the primary molding cavity 35 to form the primary molded body 3.

Next, when the molds are opened while the slide cores 33, 33 are driven in a direction of separating from each other, the primary molded body 3 is held at the distal end portion 26a of the core pin 26 of the common movable mold 20, as shown in FIG. In this state, the common movable mold 20 is moved to the secondary side position facing the second fixed mold 40 while holding the primary molded body 3, and clamped to the second fixed mold 40. .

By this clamping, the tip 26a of the core pin 26 fits into the pin hole 44 of the secondary mold plate 43 of the second fixed mold 40 as shown in FIG.
Is pressed by the opposing surface 43a of the secondary mold plate 43, and slides along the core pin 26 to move the common movable mold 2
0, and is inserted into the secondary molding cavity 25 by the secondary mold plate 43.
b is closed, and one side (the upper side in FIG. 4) of the secondary molding cavity 25 is defined by the facing surface 43a. Then, the second resin 47 for secondary molding is injected from the secondary side nozzle 45 and filled in the secondary molding cavity 25,
If the secondary molded body 4 is molded so as to surround the outer peripheral portion of the primary molded body 3, and the mold is opened and the projection is performed by the projecting pin 28, the gear 1 as a two-color molded product is obtained.

In the gear 1 obtained, a secondary formed body 4 having a U-shaped cross section is formed so as to wrap around both sides of the large diameter portion 3a of the primary formed body 3, and is provided on the large diameter portion 3a. Since the ridges 4b formed on the secondary molded body 4 are fitted into the groove 3b, the primary molded body 3 and the secondary molded body 4 are not bonded to each other by a resin (glass fiber in this example). (Polyacetal resin containing polyacetal resin and polyacetal resin), but are firmly integrated without any deviation in the axial direction and the rotational direction. In addition, the secondary molded body 4 has a U-shaped cross section, and a small difference in wall thickness of each part causes little deformation due to shrinkage, so that a highly accurate tooth profile can be formed.

FIG. 6 shows another embodiment of the present invention, in which a primary molding cavity 35 for forming a primary molding 3 is formed.
Is provided from the slide core 33 to the primary runner plate 32, and a pin hole 51 for fitting the tip of the core pin 26 is provided in the primary runner plate 32. In this manner, the primary molding cavity is formed in the primary runner plate 32. An engraving surface (may be a flat surface) for 35 or a pin hole 51 may be provided. FIG. 7 shows still another example of the embodiment of the present invention, in which a secondary mold plate 43 is provided with a concave portion 52 for fitting the primary molded body 3. Also, a concave portion for forming the secondary molding cavity 25 may be provided. 6 and 7, the same or corresponding parts as in FIGS. 1 to 5 are denoted by the same reference numerals as in FIGS. 1 to 5, and the detailed description is omitted.

The present invention is not limited to the above examples. For example, the concrete structure of each part of the mold is not limited to the above. And the first resin 3
As the second resin 9 and the second resin 47, various different materials other than those described above or synthetic resins of the same material can be used. Also, the present invention relates to products other than gears such as cams and through holes 2 having shapes other than round holes. It can also be applied to two-color molding of products having

As an internal structure for preventing the primary molded body and the secondary molded body from slipping, instead of providing the large diameter portion 3a over the entire periphery of the primary molded body 3 as in the above-described example, the internal structure is intermittently convex. A part or a concave portion may be provided to prevent the above-mentioned displacement by fitting the concave and convex with the secondary molded body 4. Further, the rotation of the primary molded body 3 and the secondary molded body 4 is stopped by using a combination of the above-mentioned grooves 3b and uneven portions having various shapes other than the ridges 4b, or by forming the primary molded body 3 into a circular section such as a polygonal shape. It may be performed by adopting a shape other than that described above, and may be omitted when the rotation stop is unnecessary.

[0020]

As described above, according to the present invention,
Since the primary molding is performed in the primary molding cavity formed by the first fixed type slide core, the shape of the primary molded body is set to a shape suitable for preventing slippage. A two-color molded product in which the molded product is firmly integrated can be obtained. Can be obtained. In addition, since the primary molded body is automatically inserted into the secondary molding cavity along the core pin when clamping with the second fixed mold, it can be performed in a simple process at low cost without using manual or special handling equipment. A two-color molded product can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a two-color molded product manufactured by the method of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a longitudinal sectional view showing an example of a two-color molded product molding die of FIG. 1 at the time of primary molding.

FIG. 4 is a longitudinal sectional view showing an example of the two-color molded article molding die of FIG. 1 when the mold is opened after primary molding.

FIG. 5 is a longitudinal sectional view showing an example of a two-color molded product molding die of FIG. 1 during secondary molding.

FIG. 6 is an enlarged sectional view of a main part showing another embodiment of the first fixed mold part in FIG. 3;

FIG. 7 is an enlarged sectional view of a main part showing another embodiment of the second fixed mold part in FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Gear (two-color molded article), 2 ... Through-hole, 3 ... Primary molded body, 4 ... Secondary molded body, 10 ... Die, 11 ... Movable plate, 12
... fixed plate, 20 ... common movable mold, 25 ... secondary molding cavity, 26 ... core pin, 30 ... first fixed mold, 33 ... slide core, 35 ... primary molding cavity, 39 ... first resin,
40 ... second fixed type, 43 ... secondary side template, 44 ... pin hole,
47 Second resin.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F202 AA23 AH12 CA11 CB01 CB22 CB28 CC04 CK19 CK43 CK54 CK81 CQ03 CQ05 4F206 AA23 AH12 JA07 JB22 JB28 JC01 JC09 JL02 JN12 JN25 JQ81

Claims (2)

[Claims] 1. A two-color molding method for injection-molding a secondary molded body on an outer peripheral portion of a primary molded body having a through hole at a center portion, comprising a secondary molded cavity and a core pin for forming the through hole. The common movable mold is clamped to a first fixed mold having a slide core forming a primary molding cavity around the core pin at the time of mold clamping, and the opening of the primary molding cavity is closed by the slide core. After filling the first resin into the primary molding cavity and performing the primary molding, the common movable mold is moved in a state where the mold is opened and the primary molded body is held on the core pin portion, and the tip of the core pin is fitted. The primary molded body is clamped to a second fixed mold having a secondary mold plate having a pin hole, and the primary molded body is inserted into the secondary molding cavity along the core pin by the mold clamping. The opening of the secondary molding cavity is closed by the secondary mold plate, and the secondary molding is formed by filling the secondary molding cavity with the second resin to obtain a two-color molded product. Two-color molding method. 2. A two-color molding die for injection-molding a secondary molded body on an outer peripheral part of a primary molded body having a through hole in a central part, wherein a common movable mold for forming one of the divided dies is provided. A first and a second fixed molds that form the other of the molds and are alternately clamped to the common movable mold, wherein the common movable mold includes a secondary molding cavity and the core pin for forming the through hole. The first fixed mold includes a slide core that forms a primary molding cavity around the core pin and closes an opening of the secondary molding cavity at the time of mold clamping in conjunction with mold clamping; The mold has a pin hole into which the tip of the core pin fits, and a secondary side for closing an opening of the secondary molding cavity and defining one side surface of the secondary molding cavity when clamping with the common movable mold. Characterized by having a template , Two-color molding die.