JPH06143374A - Plastics molding method and mold therefor - Google Patents

Abstract

PURPOSE:To manufacture a piece formed by injection molding such as plastic optical part with a high precision by a method and a mold wherein a molten resin is injected into a cavity to fill it with the resin and external force in a direction crossing a plurality of main faces of the molded piece is added to the cavity by movable inserts so as to compress it. CONSTITUTION:Fixed side inserts 6, 6 and movable side inserts 19, 19 are respectively pressurized in directions of arrows R1, R2 and are finely displaced so as to compress a fusing resin FR in cavities 25, 25. For the duration of the pressure by the fixed side inserts 6, 6 and the movable side inserts 19, 19 in the directions of the arrows R1 and R2, dwelling is continued for a fixed time and cooled. When the fusing resin FR is cooled and solidified, a fixed side mold and a movable side mold 2 are opened by a mold clamping mechanism. Then, a molded piece W formed by injection molding is extruded from movable side cavities 24, 24 by an extruding pin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic molding method suitable for manufacturing high-precision injection-molded articles such as plastic optical parts, and a mold thereof.

[0002]

2. Description of the Related Art Recently, glass lenses are being replaced with plastic lenses for the purpose of reducing the weight and cost of optical parts. There are various methods of manufacturing this plastic lens, but from the viewpoint of mass productivity and economical efficiency,
Injection molding or injection compression molding is the mainstream.

By the way, in the injection molding method, in the case of a plastic molded product having a structure in which a pinpoint gate or a submarine gate cannot be used, the molded product, the gate, the runner, and the sprue come out of the mold as an integrated product. Therefore, after removing the plastic molding from the mold,
A post-process for separating the molded product from the gate, runner, and sprue with a cutting machine is essential. However, when the molded product is a plastic optical component, a deforming force acts on the optical surface of the plastic optical component in the cutting process to cause distortion, which deteriorates the molding accuracy. As a result, the performance of the optical component is deteriorated and the product yield is reduced.

On the other hand, the injection compression molding method is applied to molding of plastic lenses and optical disks. In order to improve the shape transferability of the mold, compression in the mold or compression of the mold clamping mechanism of the molding machine is performed. The resin filled by the method is compressed and molded. However, since the compression direction is one direction, there are few molded products that satisfy the molding accuracy, which is just another step in terms of accuracy.

[0005]

As described above, in the conventional precision plastic molding, various causes for lowering the molding accuracy are included.

The present invention has been made in consideration of the above circumstances, and solves the technical problem of the above-described conventional plastic molding method, and manufactures a highly accurate injection molded product such as a plastic optical component. An object of the present invention is to provide a plastic molding method and a mold for the plastic molding.

[0007]

According to the present invention, a movable insert is used to form at least a portion of a cavity in which an injection-molded article having a plurality of main surfaces is molded, at least a portion for molding the main surface of the injection-molded article. Further, after the molten resin is injected and filled in the cavity, the movable insert compresses by applying an external force in a direction intersecting each of the plurality of main surfaces of the injection-molded article.

[0008]

According to the present invention having the above-mentioned structure, the surface formed on the movable insert is precisely transferred to the injection-molded product with a uniform and relatively small stress, and the molding accuracy can be remarkably improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a mold used in the plastic molding method of this embodiment. That is, the mold of this embodiment is provided with a fixed-side mold part 1 attached to a fixed side of a mold clamping mechanism of an injection molding machine (not shown), and a reciprocating movable part facing the fixed-side mold part 1. The movable mold part 2 and the molded product W such as a lens, a prism, a polygon mirror, and an optical disk, which are provided in both the fixed mold part 1 and the movable mold part 2 and are injection molded, are bidirectional ( The compression mechanism 3 improves the transferability of the mold by compressing from the direction of the arrows R1 and R2). Thus, the fixed-side mold unit 1 includes a fixed-side mounting plate 4 having a rectangular plate shape, a fixed-side mold plate 5 mounted on one main surface side of the fixed-side mounting plate 4, and the fixed-side mold plate 4. 5, a pair of fixed-side inserts 6 and 6 that are fitted in the arrow R1 and R2 directions so as to be movable back and forth, a heat-insulating plate 7 that is interposed between the fixed-side mounting plate 4 and the fixed-side template 5, and fixed. A cooling pipe 8 embedded in the side mold plate 5 so as to traverse both sides of the fixed side inserts 6 and 6, and a circle penetrating and fitted in the central portions of the fixed side mounting plate 4 and the fixed side mold plate 5. The tubular side sprue 9 and the fixed side mounting plate 4 so as to coaxially surround the opening at one end of the sprue 9.
A locate ring 10 fixed to the fixed side runner 11, fixed side runners 11 and 11 forming a pair of grooves extending from the other end opening of the sprue 9 to the left and right sides at the open surface 5a of the fixed side mold plate 5,
The fixed-side runners 11 and 11 are composed of fixed-side gates 12 and 12, which are continuously provided at the end portions of the fixed-side runners 11 and 11 and form a pair of small grooves. Steps are formed on the open surface 5a and the front surfaces of the fixed inserts 6 and 6, and these steps form fixed cavities 13 and 13 for forming the molded product W. And, these fixed side cavities 13,
The fixed side gates 12 and 12 communicate with 13. on the other hand,
The movable side mold part 2 is a rectangular plate-shaped movable side mounting plate 14 attached to the movable side of a mold clamping mechanism of an injection molding machine (not shown), and the fixed side mold part 1 of the movable side mounting plate 14. A pair of block bodies 15 and 15 fixed to both side portions, a support plate 16 fixed to the movable side mounting plate 14 through the block bodies 15 and 15, and a movable plate attached to the support plate 16. Side template 17
A heat insulating plate 18 interposed between the support plate 16 and the movable side mold plate 17; and a pair of movable side inserts 19 fitted to the movable side mold plate 17 so as to move back and forth in the directions of arrows R1 and R2. 19
A cooling pipe 20 embedded in the movable-side mold plate 17 so as to traverse both sides of the movable-side mold plate 17, and one end thereof is fixed at a position coaxial with the sprue 9 of the movable-side mount plate 14. The sprue lock pin 21 having the other end penetrating the support plate 16 and the movable mold plate 17 to face the through hole 9a of the sprue 9, and the fixed runner on the open surface 17a of the movable mold plate 17. Movable side runners 22 and 22 provided so as to face 11 and 11, and movable side gates 23 and 23 provided at the opening surface 17a of the movable side template 17 so as to face the fixed side gates 12 and 12, respectively. It consists of As a result, steps are formed on the opening surface 17a and the front surfaces of the movable inserts 19, 19, and these steps are formed on the molded product W.
Movable side cavities 24, 24 for forming the. Then, these movable cavities 24, 2
The movable side gates 23, 23 communicate with 4. further,
When the fixed side mold part 1 and the movable side mold part 2 are brought into close contact with each other by the mold clamping mechanism, the fixed side cavities 13 and 13 and the movable side cavities 24 and 24 are cavities for forming the molded product W in a hurry. The tees 25, 25 are formed. Further, the fixed side runners 11 and 11 and the movable side runners 22 and 22, as well as the fixed side gates 12 and 12 and the movable side gates 23 and 23, have the fixed side mold part 1 and the movable side mold part 2, respectively. The runners 26 and 26 and the gates 27 and 27 are formed when they are brought into close contact with each other by the fastening mechanism. On the other hand, the compression mechanism 3 has pistons 6a, 6a (see FIG. 2) connected to the backs of the fixed inserts 6, 6 and fixed hydraulic cylinders 28, 2 embedded in the fixed template 5.
8, movable side hydraulic cylinders 29, 29 having pistons 19a, 19a connected to the backs of the movable side inserts 19, 19 and embedded in the movable side mold plate 17, and pressure oil internally provided in the fixed side mold plate 5. In-mold hydraulic pipes 30 and 30 for supplying PO to the fixed hydraulic cylinders 28 and 28, and in-mold hydraulic pipes 31 provided in the movable mold plate 17 for supplying pressure oil PO to the movable hydraulic cylinders 29 and 29, 31 and in-mold hydraulic pipes 30, 3 at one end
Hydraulic pipes 32a connected to the open ends of 0, 31, and 31,
32b, 33a, 33b and these hydraulic pipes 32a, 32
b, 33a and 33b are connected to the hydraulic pump 34. The fixed hydraulic cylinders 28, 28 and the movable hydraulic cylinders 29, 29 are moved in both directions (arrow R1,
Cylinders that can be driven in the R2 direction), and pistons 6a, 6a, 19a, 19a are slidably incorporated therein and these pistons 6a, 6a, 19a, 19a are included.
a is the fixed side inserts 6, 6 and the movable side insert 19,
It is integrally connected to 19. The directions of the arrows R1 and R2 are set to directions orthogonal to the main surface of the cylindrical molded product W molded by the mold of this embodiment. In addition,
Although not shown, the movable side mold part 2 has a plurality of push-out pins for pushing out the injection-molded article W from the moveable-side cavities 24, 24 after the mold is opened, and a plurality of push-out pins for driving the push-out pins. Drive means are provided. Next, a plastic molding method of this embodiment using the mold having the above-mentioned structure will be described.

First, the fixed mold part 1 and the movable mold part 2 are brought into close contact with each other by the mold clamping mechanism. At this time, the cooling pipe 20 ...
Cooling water is circulated in the tank. Next, the molten resin FR is injected and filled into the cavities 25, 25 through the sprue 9, the runners 26, 26 and the gates 27, 27 from a nozzle of an injection molding machine (not shown). Then, the molten resin F
With the R filled in the cavities 25, 25, the hydraulic pump 34 is activated to supply the pressure oil PO to the hydraulic pipes 32a, 32.
b, 33a, 33b and in-mold hydraulic pipes 30, 30, 31,
It is supplied to the fixed hydraulic cylinders 28, 28 and the movable hydraulic cylinders 29, 29 via 31. Then, the pistons 6a, 6a, 1 built in the fixed hydraulic cylinders 28, 28 and the movable hydraulic cylinders 29, 29 are included.
9a and 19a press in the directions of arrows R1 and R2, respectively. As a result, the fixed inserts 6 and 6 and the movable inserts 19 and 19 are pressed in the directions of the arrows R1 and R2, respectively, and correspond to the molten resin FR in the cavities 25 and 25 (the main surface of the molded product W). ) Is slightly displaced (see FIG. 2). Then, the holding pressure is continued and cooled for a certain period of time while the pressurization by the fixed inserts 6 and 6 and the movable inserts 19 and 19 in the directions of the arrows R1 and R2 is continued. Then, when the molten resin FR is cooled and solidified, the fixed side mold part 1 and the movable side mold part 2 are opened by the mold clamping mechanism, and further, from the movable side cavities 24, 24 by the extrusion pin. The injection molded product W is extruded.

As described above, in this embodiment, the fixed-side inserts 6 and 6 and the movable-side inserts 19 and 19 that form the optical surface of the molten resin FR filled in the cavities 25 and 25 are close to each other. Direction (Arrows R1, R2
Direction), the optical surfaces formed on the fixed-side inserts 6 and 6 and the movable-side inserts 19 and 19 are precisely transferred with uniform and relatively small stress, and the molding accuracy is improved. Remarkably improved. Therefore, when applied to the molding of optical components such as lenses, prisms, polygon mirrors, and optical discs, the quality and yield can be improved. Although the hydraulic mechanism is used as the power source of the compression mechanism in the above embodiment, other power sources such as an electric motor and air pressure may be used.

Further, in the above embodiment, the compression is performed from two directions along the optical axis direction of the molded product (two directions orthogonal to the main surface), but the optical surface is an outer peripheral surface such as a plastic polygon mirror. When it is formed in the above, the compression may be performed from a plurality of directions orthogonal to the axis.

[0014]

According to the present invention, at least a portion of the cavity for molding an injection-molded article having a plurality of main surfaces to mold the main surface of the injection-molded article is formed by a movable insert, and After the molten resin is injected and filled in the cavity, the movable insert compresses it by applying an external force in the direction intersecting each of the main surfaces of the injection molded product, so that uniform and relatively small stress is applied. Thus, the surface formed on the movable insert is precisely transferred to the injection-molded product, and the molding accuracy is significantly improved. Therefore, when the present invention is applied to the molding of optical parts such as lenses, prisms, polygon mirrors, and optical discs, the quality and the yield can be remarkably improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a mold according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a plastic molding method according to an embodiment of the present invention.

[Explanation of symbols]

1: fixed side mold part, 2: movable side mold part, 3: compression mechanism,
6: fixed side insert, 19: movable side insert.

Claims (2)

[Claims] 1. A plastic molding method for plastic-molding a molded article having a plurality of main surfaces, an injection step of injecting a molten resin into a cavity formed by a pair of molds, and the cavity is filled by this injection step. And a compression step of compressing the melted resin at least by applying an external force in a direction intersecting with each of the plurality of main surfaces of the injection-molded article. 2. A mold for molding a molded article having a plurality of main surfaces by injecting the molten resin into a cavity formed by a pair of mold parts, wherein at least the injection of the cavity is performed. A mold comprising a movable insert provided in a portion for molding a main surface of a molded product, and a compression means for pressing the movable insert in a direction of compressing the molten resin injected into the cavity. .