JPH0430329B2 - - Google Patents

Description

[Detailed description of the invention] Technical field The present invention relates to an injection molding method and apparatus.

Prior Art Conventionally, when a molded product having concave portions such as holes or grooves due to the structure of the molded product is molded by an injection molding method, the molded product is placed in an injection mold used in the molding method. A convex member, such as a core pin, having a shape corresponding to the concave portion is attached, and the concave member such as the core pin is used to form a concave portion such as a hole in the molded product to be molded in the cavity of the mold. A method of injection molding of pre-molded products is adopted.

One example of recently disclosed technology is the invention described in Japanese Patent Application Laid-open No. 73958/1983.

That is, as described in the Detailed Description of the Invention column of the same publication, the invention relates to improvements in injection molds, particularly in molds for injection molding molded products having the same shape as the molded products. , the conventional technology required two types of molds depending on the shape of the molded product, depending on whether there are holes or not, but in order to provide a mold that can mold both molded products without holes and with holes using one mold. It was developed.

Incidentally, as described in the description of the specific embodiments and the claims section, the mold according to the invention accommodates the core pin and the spring in the hole formed in the movable side mold plate. A bolt that pushes up the core pin against the spring is screwed into the receiving plate below the plate, and by turning the bolt, the core pin is made to protrude from the movable template plate and come into close contact with the cavity surface, Alternatively, the movable mold plate is retracted to the same level as the upper surface of the molded product to obtain molded products with holes and without holes.

When a desired molded product is to be injection molded using a mold having such a configuration, that is, when a perforated molded product is to be molded, the bolts provided in the mold are rotated. After setting the core pin with its tip protruding from the movable mold plate against the elasticity of the spring, the required molten resin is injected into the cavity of the mold with the same configuration through the flow path of the mold. At the same time, by pressurizing and compressing this, an injection molded product with holes formed by the core pin can be molded.

However, when the molten resin is injected into the cavity of the mold, the flow of the molten resin is obstructed by the core pin protruding from the movable mold plate (the molten resin branches and flows by the core pin), and the flow direction At the back of the core pin, the separated resins merge again and fuse, so the convergence,
At the fusion position, a so-called weld line, which can be seen on the exterior of the molded product, occurs.

In the part where the weld line is formed in this injection molded product, the molecular orientation of the resin and the orientation of the glass fibers, carbon fibers, etc. contained in the resin are different from other parts, so the molten resin solidifies. Due to the difference in the amount of shrinkage and the difference in the coefficient of linear expansion, the accuracy of the shape, roundness, and flatness of the molded product after solidification is extremely reduced.

In addition, the mechanical strength, chemical resistance, and solvent resistance of injection molded products become weaker, as well as their resistance to changes over time, which increases the risk of cracking along the weld line. , is fatal for injection molding of precision molded products, and is fatal for injection molding.
Injection molding methods that do not have any means to prevent the occurrence of weld lines other than changing the design of the molded product have a narrow scope of application not only to precision molded products but also to other injection molded products. This is the current situation.

In addition, the Japanese Patent Application Laid-open No. 1983-1999 cited as the prior art
Regarding the composition of the mold described in Publication No. 73958,
Since specific illustrations are omitted, please refer to the publication for details.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-mentioned drawbacks in the current injection molding technology and to provide an injection molded product that has concave parts such as holes and grooves and does not have weld lines. In particular, with
For injection molding processing that has concave parts such as holes and grooves in precision molding processing that requires precision such as shape accuracy, roundness and flatness, we also provide injection molding that does not have concave parts such as holes and grooves. The object of the present invention is to provide an injection molding method and an injection molding apparatus that can be applied with the same precision as molded products.

Summary of the Invention The present invention relates to injection molding of molded products having concave parts such as holes and grooves, and involves melting resin into convex members such as core pins and rods for forming the concave parts such as holes and grooves in the molded product. By protruding after injection and filling into the cavity, it is possible to eliminate branching during resin inflow and merging and fusion after the branching, making it possible to provide injection molded products without so-called weld lines. .

EMBODIMENTS The injection molding method of the present invention will be described in detail below along with an injection molding die which is an embodiment of an injection molding apparatus directly used for carrying out the method as shown in the accompanying drawings.

Fig. 1 is a longitudinal cross-sectional view of an injection mold for molding the injection molded product shown in Fig. 3, and Fig. 2 a and b are partial cross-sectional views showing the operating state of the punching pin in the same mold. be.

Further, FIG. 3 is a perspective view showing an example of an injection molded product molded by the injection molding method of the present invention, and the injection molded product 30 includes a flange portion 32 provided at the upper opening of a cylindrical main body 31, and This flange portion 32 is made of a hollow cylindrical body with three holes 33 provided at equal intervals.

Therefore, the injection molded product 30 having such a shape
The injection mold shown in the first figure is a pinpoint injection mold having a three-plate structure, including a fixed side mold plate forming a cavity 5 sufficient for molding the injection molded product 30; 4
The fixed side template 4 is attached to a runner strip by a movable side template 7 arranged opposite thereto, and a fixed side mounting plate 1 provided with a sprue portion 21 that communicates with the sprue runner 2 provided on the fixed side template 4. The par plate 3 is interposed and held, and the movable side template 7
is held by a movable mounting plate 10 with a receiving plate 8 and a spacer block 9 interposed therebetween.

Further, 6 is a core provided on the movable mold plate 7, and 11 is an ejector pin held movably up and down by ejector plates 22 and 23, which penetrates the movable mold plate 7 to the upper surface of the mold. The ejector pin 11 is inserted into the through hole 7a to be opened and the through hole 8a which is opened through the receiving plate 8 which communicates with the through hole 7a. It is paired with a plurality of ejector pins with other ejector pins arranged according to the configuration.

Furthermore, the fixed side template 4 has a cavity 5.
The injection molded product 30 is located at a position corresponding to each hole 33 of the injection molded product 30, and a drilling cylinder 13 is disposed and opened therein. A cylinder ram 24 provided integrally connected to a drilling pin 17 having a shape corresponding to the shape of each hole 33 of 30 is always biased in the retracting direction (upward direction in the drawing) with a spring 15 interposed therebetween. Each cylinder 13 has a lid 14 that can be freely moved forward and backward (up and down in the drawings), and is screwed onto the upper opening 19 of each cylinder 13 and has an upper stopper 18 .

A bottom stopper 16 with an inner diameter corresponding to the outer diameter of the cylinder ram 24 and a drilling pin fitting hole 20 with an inner diameter corresponding to the outer diameter of each of the drilling pins 17 are provided at the lower part of each cylinder 13, Each drilling pin 17 is configured to be able to protrude into the cavity by lowering the cylinder ram 24 of each drilling pin 17 against the elasticity of the spring 15 as shown in the drawing.

In addition, the cylinder 13 is provided with each hole punching pin 1.
The air flow path 12 connected to the air flow path 26 of the operating section 25 of No. 7 is opened.

An operating section 25 connected to each cylinder 13 via the air flow path 12 and air flow path 26 operates the cylinder ram 24 in each cylinder 13 to move downward in the cylinder 13 against the elasticity of the spring 15. An air pressure source 27 , a solenoid valve 28 for turning on and off the air pressure source 27 interposed between the air pressure source 27 and the air flow path 26 , and this solenoid valve 28 and the air pressure source 27
It consists of an air tank 29 provided in between.

The operation of each drilling pin 17 by the operating section 25 will be described later with reference to FIGS. 2a and 2b, but the solenoid valve 28 of the operating section 25 is
ON due to the injection signal of the molten resin in the injection mold and the release operation signal after injection molding, etc.
Performs OFF operation.

Now, when injection molding the desired injection molded product 30 using the injection mold having the above configuration, the movable side mold plate 7 is set in the state shown in the first figure with respect to the fixed side mold plate 4. After that, the required molten resin 34 is injected into the cavity 5 through the sprue section 21 and the sprue runner 2 from a molten resin injection machine (not shown).
Inject and fill inside.

When injecting and filling this molten resin 34 into the cavity 5, the steps shown in FIG. 1 and, more specifically, in FIG.
As shown in FIG.
4 is held at the top dead center by the elasticity of the spring 15, with its upper side being locked by the top stopper 18, and each drilling pin 17 at the tip of each cylinder ram 24 is fitted into the fitting hole 20. The tip 17a is held flush with the inner surface 4a of the stationary mold plate 4.

Therefore, the molten resin 34 injected and filled into the cavity 5 flows through each fitting hole 20 into each cylinder 1.
3 will not be filled.

Now, in the above description, the molten resin 34 is injected and filled into the cavity 5 with each hole pin 1.
7, and the merging and merging after the branching.

However, when the speed step in the injection molding process approaches the end and the resin pressure in the injection mold reaches a certain value and switches to the pressure holding step, in synchronization with this, that is, the injection molding A synchronizing signal related to the pressure holding process in the mold is transmitted to the solenoid valve 28 of the operating section 25.
By inputting the input into the air and turning on the solenoid valve 28, predetermined compressed air flows from the air tank 29 of the air pressure source 27 into each cylinder 13 via the air passages 12 and 26, and each cylinder ram 24 moves downward against the elasticity of spring 15, and cylinder ram 2
4 is held at the bottom dead center where it is locked by the bottom stopper 16. Therefore, at this time, each hole punching pin 17 is held protruding into the cavity 5 filled with the molten resin 34, as shown in FIG. open it.

Thereafter, the process moves to a high-pressure holding process, and while each of the drilling pins 17 is held in the protruding state shown in FIG. hole 3
3 is opened, the molded product 30 is injection molded, and in the mold release process, for example, a synchronization signal that synchronizes with the mold release operation of the injection mold is inputted to the solenoid valve 28 of the operating section 25, and this is performed. By turning it off, each hole pin 17 on the stationary template 4 can be returned to the state shown in FIGS. 1 and 2a.

Furthermore, the injection molded product 30 after being released from the mold is molded into the shape shown in FIG. Molded products with shape accuracy and durability can be molded.

In addition, the operation unit 2 is synchronized with the operation of the injection molding machine.
The method of synchronizing the electromagnetic valves 28 in step 5 can be carried out by conventionally known means, and the specific means will be omitted, and the timing of the protruding operation of each hole pin 17 will be explained below. The injection filling of No. 34 can be carried out within a range that can prevent the occurrence of merging and fusion after branching of the resin, which causes weld lines, and is not limited to the above-mentioned embodiments.

Further, in the construction of the injection mold, the construction of each hole pin 17 and its operating portion 25 itself is not limited to the construction shown in the drawings, but may be of any other design that can exhibit the same effect. This can be implemented by changing the configuration, and an example is shown in which the same configuration is provided on the fixed side template 4, but on the contrary, it can be provided on the movable side template 7, or it can be implemented without molding. It can be provided at a required position required for the shape of the injection molded product, for example, on both the fixed side mold plate 4 and the movable side mold plate 7, or not only on the upper and lower surfaces of both mold plates 4 and 7, but also opposite to the side surface of the cavity 5. In addition, in addition to the configuration in which the cylinder 13 is provided in both mold plates 4 and 7, the hole-drilling pin 17 that protrudes into the cavity 5 is guided outside the mold. This can be carried out using a cylinder provided outside the mold and its operating section.

Further, although the illustrated injection molded product 30 and the injection mold for molding the same are for molding in which a hole 33 is provided, the same can naturally be applied to injection molded products having other concave portions such as grooves. It can be carried out with great effect, and the number and shape of the holes 33, punching pins 17, fitting holes 20, etc. are not limited to the illustrated embodiment.

Effects of the Invention As is clear from the above explanation, the present invention can obtain the following effects.

(1) The resin that has flowed into the mold for convex parts such as drilling pins required for machining holes and grooves required for the product has finished flowing and is in a molten state. The method of providing concave parts such as holes that protrude into the cavity in between does not impede the flow of the resin, so it does not disrupt the molecular orientation of the resin or the orientation of glass fibers, carbon fibers, etc. contained in the resin. Therefore, precision molded products with high shape accuracy such as roundness and flatness can be formed.

(2) When creating holes or grooves in areas where the resin flow path is narrow and the plate thickness is thin due to product shape constraints, the required convex member must be placed after the resin has flowed in, which prevents the resin from flowing in the conventional way. It is possible to mold things that were previously impossible, and the range of applications for molding processing is expanded.

(3) For convex members such as pins in the flow path, the so-called weld line does not occur because the boundary layer around the outer periphery of the convex members such as pins, which conventionally always occur due to the flow of resin, is completely eliminated. . Therefore, the appearance is extremely effective and the risk of cracking from the weld line is eliminated.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the injection molding apparatus of the present invention, FIGS. 2 a and b are partial cross-sectional views showing the operating state of each drilling pin in the same apparatus, and FIG. 3 is a longitudinal cross-sectional view showing an embodiment of the injection molding apparatus of the present invention. FIG. 1 is a perspective view showing an example of an injection molded product produced by an injection molding method. 1... Fixed side mounting plate, 2... Sprue runner, 3
...Runner stripper plate, 4...Fixed side template, 5...Cavity, 6...Core, 7...
Movable side template, 8... Receiving plate, 9... Spacer block, 10... Movable side mounting plate, 11... Ejector pin, 12, 26... Air flow path, 13... Cylinder, 14... Lid , 15... Spring, 16...
...Bottom stopper, 17...Drilling pin, 18
...Atsupa stoppa, 19...Opening, 20
...Drilling pin fitting hole, 21...Sprue part, 2
2, 23...Ejector plate, 24...Cylinder ram, 25...Operation unit, 27...Air pressure source, 28...Solenoid valve, 29...Air tank, 30
... Injection molded product, 31 ... Main body, 32 ... Flange portion, 33 ... Hole, 34 ... Molten resin.

Claims (1)

[Scope of Claims] 1. In an injection molding method for a molded product having a concave portion such as a hole or groove, after a resin is injected into a cavity of an injection mold, a method corresponding to the concave portion required for the molded product is provided. An injection molding method characterized in that a convex member is formed by protruding into the cavity. 2. The projecting operation of the convex member is performed during the molding process in the cavity in conjunction with a pressure holding process after a speed process of flowing resin into the cavity. Injection molding method described. 3. In an injection molding apparatus for molded products having concave portions such as holes and grooves, a convex member for molding the concave portions such as holes and grooves of the molded product is provided in a molding cavity of the molded product so as to be freely retractable. and an operating section that projects and holds the convex member into the molding cavity after resin has flowed into the molding cavity. 4. The injection molding apparatus according to claim 3, wherein the convex member is a pin, rod, or other rod-like member. 5. Claim 3, wherein the convex member is composed of one or more convex members.
The injection molding apparatus according to item 1 or 4. 6. The injection molding apparatus according to claim 3, 4, or 5, characterized in that the convex member is provided on a stationary mold plate constituting the molding cavity. 7. The injection molding apparatus according to claim 3, 4, or 5, wherein the convex member is provided on a movable template forming the molding cavity. 8. Claims 3, 4, or 5, characterized in that the convex member is provided on both fixed and movable mold plates constituting the molding cavity. injection molding equipment. 9. Claims 3 and 4, characterized in that the convex member is always biased in a non-acting direction opposite to the direction in which it projects into the molding cavity. The injection molding apparatus according to item 5, 6, 7, or 8. 10 The operation section of the convex member is configured by an air pressure, oil pressure, or other pressure source connected via an operation valve to a cylinder housing a cylinder ram connected to the convex member so as to be movable forward and backward. An injection molding apparatus according to claim 3. 11 The operating portion of the convex member operates to hold the convex member protruding into the molding cavity in connection with the pressure holding process after the resin has flowed into the molding cavity, and also operates to hold the convex member protruding into the molding cavity. Claim 3 is characterized in that the projecting state of the convex member into the molding cavity can be released in connection with the mold release process of the injection molded product. Injection molding equipment.