JPS63202418A - Hot runner type injection molding method and apparatus - Google Patents

Abstract

PURPOSE:To reduce the mold cost by a method wherein a hot runner type injection molding method consists of a process to injection mold a product with an injection molding equipment, to which a hot runner device is attached, a process to detach a fixed mold under the state that the hot runner device is being attached to the injection molding equipment and a process to attach another fixed mold to the injection molding equipment, on which the hot runner device is left undetached. CONSTITUTION:In the case of injection molding, a mounting block 62 is located in a recess 76 provided on a fixed platen 10. Resin is injected from an injection cylinder 50 through nozzles 64, each of which is fitted to a nozzle hole 78 which is formed passing through the fixed platen 10, a locating ring 14 and a fixed mold 12. The exchange of mold is done by opening the mold through the retreating motion of a movable platen 16 together with a movable mod 20 and, after that, under the condition that the nozzles 64 are drawn out of the nozzle holes 78 by retreating the injection cylinder 50. In case that the hot runner device 60 is left on the injection molding equipment side and, that after the detachment of the fixed mold 12 only, the nozzles 64 are still in the state fixed to the nozzle holes 78, a new fixed mold 12 is fitted to the nozzles 64 and fixed to the fixed platen 10.

Description

Detailed Description of the Invention Technical Field The present invention involves heating a synthetic resin (hereinafter simply referred to as resin) injected from an injection cylinder of an injection molding device into a mold cavity by heating the resin in a runner to bring it to a molten state. The present invention relates to a hot runner injection molding method for molding products while maintaining the same temperature, and a hot runner injection molding apparatus suitable for carrying out the method.

Conventional technology Injection molding equipment injects fluid resin into a mold cavity to mold a product into a predetermined shape, and is suitable for molding not only thermoplastic resin products but also thermosetting resin products. is also used. This injection molding machine generally consists of (a)
(b) a fixed plate that is provided in a fixed position and to which a fixed mold is attached; and (b) a movable mold that is provided so as to be able to approach and move away from the fixed plate and forms a cavity in cooperation with the fixed mold. It is configured to include a movable platen and (C) an injection cylinder that is provided on the opposite side of the fixed platen to which the fixed mold is fixed and supplies resin in a fluid state to the cavity. A runner is installed in the fixed mold to guide the resin injected from the injection cylinder into the cavity. With the injection cylinder connected to the opening on the fixed plate side of the runner, the resin is injected and fills the cavity. be done. After filling is completed, if the resin is a thermoplastic resin, the resin filled in the cavity is cooled and solidified to obtain a product in a predetermined shape. However, the resin in the passages solidifies during cooling and is taken out together with the product, making the removal process troublesome and inevitably lowering the material yield. Further, when the resin is a thermosetting resin, it is desirable to preheat the resin in the passage to a temperature that does not solidify the resin in order to shorten the heating time after filling.

A hot runner injection molding method has been proposed to solve these problems, and the injection molding method described in Japanese Patent Publication No. 61-59219 is one example thereof. In this injection molding method, a heating device is installed in the fixed mold to heat the runner installed inside the mold, so that even if the resin filled in the cavity solidifies, the resin in the runner does not solidify. Thus, the above problem is solved. Also, if you use the hot runner injection molding method when injection molding thermosetting resin,
Since the resin can be preheated, the heating time required to reach the curing temperature after filling the cavity with the resin can be shortened.

Problems to be Solved by the Invention However, if the runner and the heating device are provided in the fixed mold as described above, it is necessary to provide them for each mold, resulting in a problem that the cost of the mold increases.

Means for Solving the Problems The hot runner molding method according to the present invention solves the above problems by: (a) connecting a cavity formed by a fixed mold and a movable mold to an injection cylinder; A process of injection molding a product by attaching a hot runner device equipped with a runner that heats the resin in the runner and a heating device that heats the resin in the runner to an injection molding device between a fixed mold and an injection cylinder; The process of removing the fixed mold from the injection molding machine while leaving the runner device on the injection molding machine side;
C) attaching another stationary mold to the injection molding apparatus in which the hot runner apparatus remains.

Further, the hot runner injection molding apparatus according to the present invention includes, in addition to the above +8) fixed plate, (b) movable plate and (C1 injection cylinder), (d) a base connected to the injection cylinder;
A nozzle part is provided integrally with the base part and is fitted into a nozzle hole provided through the fixed platen and the fixed mold. It has a runner that leads to the cavity and a heating device that heats the synthetic resin within the runner, and is configured to include a hot runner device that is fixed to the fixed plate from the side opposite to the side on which the fixed mold is fixed.

Effects and Effects According to the hot runner injection molding method according to the present invention, the hot runner device provided on the injection molding apparatus side can be shared for heating a plurality of fixed molds, and the runner and heating device can be used for each fixed mold. There is no need to provide a device, and the cost of the mold can be reduced.

Moreover, there is no need to connect and disconnect the electric cord of the heating device every time the fixed mold is replaced, and the mold replacement work can be performed easily and efficiently.

Moreover, according to the apparatus according to the present invention, it is possible to carry out the hot runner injection molding method of the present invention, and by fixing the hot runner apparatus from the fixed platen side, it is easy to attach and detach the fixed mold to the fixed platen. Along with this, the thickness of the mold increases due to the limited spacing between the fixed plate and the movable plate.
This has the effect of widening the range of usable molds.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram showing the main parts of a hot runner type injection molding apparatus which is an embodiment of the present invention. This injection molding apparatus is for injection molding thermoplastic resin, and in the figure, reference numeral 10 is a stationary plate provided at a fixed position. This stationary platen 10 has a thick plate shape, and a stationary mold 12 is positioned on one plate surface by a plurality of locate rings 14 and fixed with bolts 15. A movable platen 16 is moved between the fixed platen 10 and the fixed platen 10 by a moving device (not shown).
It is installed so that it can be approached and separated from the target.

The movable platen 16 also has a thick plate shape, and a movable mold 20 that forms a cavity 18 together with the fixed mold 12 is fixed to the end face of the movable platen 16 on the side facing the fixed platen 10 together with a product extrusion device 22. Ru. These fixed molds12. The movable mold 20 is a multi-cavity mold that molds multiple products at once.
Two of the plurality of cavities 18 are shown in the figure. The locate rings 14 are provided in the same number as the cavities 18 and are fixed at positions corresponding to the cavities 18 of the stationary platen 10. Note that the number of locate rings 14 does not have to be the same as the number of cavities 18, and they may be provided at positions different from the positions corresponding to the cavities 18.

The movable mold 20 is slidably fitted to a guide pin 26 provided upright on the fixed mold 12, and is positioned relative to the fixed mold 12 and guided in its movement. and is attached to a mounting plate 24 fixed to the movable platen 16 via a plurality of spacer blocks 28.

The product extrusion device 22 includes an extrusion plate 32.

The extrusion plate 32 is slidably fitted to a plurality of guide pins 34 whose ends are supported by the mounting plate 24 and the movable mold 20, and the extrusion plate 32 includes extrusion pins for extruding the product. 38 and 40 are provided in each cavity 18. The shape of the tips of these push-out pins 38 and 40 is matched to the shape of the part of the product to be pushed, and the bottle 38 is attached to the push-out plate 32 so as not to be relatively rotatable, and always pushes the product in a constant phase. Being able to do that.

Further, the extrusion plate 32 is biased away from the movable mold 20 by a plurality of compression coil springs 44 disposed between the extrusion plate 32 and the movable mold 20.
It is regulated by a stopper 46 fixed to. Although FIG. 1 is drawn asymmetrically with respect to the center line of the mold in order to show the guide pins 26 and 34 and the compression coil spring 44, in reality these pins 26 and 34 are drawn asymmetrically with respect to the center line of the mold.
34, the spring 44 is provided at a position closer to the center line than the illustrated position.

Movable plate 16. The push rod 4 passes through the center of the mounting plate 24.
8 are arranged. This push rod 48 is always attached to the mounting plate 2.
However, when the movable platen 16 is moved a certain distance away from the fixed platen 10, it comes into contact with the push-out plate 32, and as the movable plate 16 is further retreated from that state, the push-out plate 32 is moved toward the movable mold 20 against the biasing force of the spring 44. As a result, the ejector pin 3
8.40 will extrude the molded product into the cavity 18. After extruding the product, when the movable platen 16 is moved forward, the extrusion plate 32 is urged by the spring 44 and returns to its original position. Note that the extrusion rod 48 may be movably provided and moved toward the movable mold 20 to move the extrusion plate 32 and extrude the product.

An injection cylinder 50 is disposed on the opposite side of the fixed platen 10 to the side on which the fixed mold 12 is fixed. The injection cylinder 50 includes a housing 52 equipped with a heating device and a screw 54 that is movably provided in the housing 52 in the axial direction. is heated and melted and sent to the tip of the cylinder by the screw 54. This injection cylinder 50 is movable relative to the fixed platen 10 for cleaning the screw 54 or the like.

A large-diameter mounting portion 56 is provided at the tip of the housing 52, and a hot runner device 60 is fixed thereto. The hot runner device 60 includes a mounting block 62 as a base and the same number of nozzles 64 as the cavities 18, and is fixed to the mounting portion 56 at the mounting block 62,
A nozzle 64 is fixed to the mounting block 62 in correspondence with each cavity 18. A resin supply port 6J communicating with an injection hole 66 formed in the mounting portion 56 and a branch passage 70 branched from the resin supply port 68 are provided in the mounting block 62. A plurality of tips communicate with passageways 72 within each nozzle 64. A runner 73 is formed by the resin supply chamber 681, the branch passage 70, and the passage 72.

During injection molding, the mounting block 62 is positioned within the recess 76 provided in the fixed platen 10, and the nozzle 64 is inserted into the fixed platen 10.
Locate ring 14. Resin is injected from the injection cylinder 50 while being fitted into a nozzle hole 78 formed through the fixed mold 12 .

The injected resin is supplied to the cavity 18 through the injection hole 66 and the runner 73, and the branch passage 7
A heating device (not shown) heats the branch passage 70 by generating heat from the resin in the conductor 74 by the electric current supplied through the conductor 74.
heated by.

The nozzle 64 has the same structure as the nozzle described in JP-A-61-3720-9I4, and will be briefly explained based on FIG. 2. The nozzle 64 includes a large-diameter portion 80 fixed to the mounting block 62 and a nozzle portion 82 extending from the large-diameter portion 80. The nozzle 64 is provided with a mounting member at two locations separated in the diameter direction of the large-diameter portion 80. 83 to the mounting block 62 (see FIG. 1). This nozzle 64 is made of a conductive metal having electrical resistance, and has flange portions 84 provided at two diametrically apart portions of the large-diameter portion 80 that are fixed to the attachment pro-touch 2. A conductive wire 85 is fixed via a terminal 86.

Furthermore, two slits 88 extending in the axial direction are formed in the peripheral wall of the nozzle 64 at positions separated from each other in the diametrical direction, leaving the tip of the nozzle portion 82 intact. The nozzle 64 is connected to the terminal 86
The part where the nozzle part 82 is fixed and the openings at both ends of the passage 72 are covered with a ceramic film 90, and the outside of the part of the film 90 that covers the nozzle part 82 is further covered with a ceramic protection tube 92. There is. The inner diameter of the nozzle hole 78 is larger than the nozzle portion 82 covered with the protective tube 92 except for the portion where the tip of the nozzle portion 82 is fitted, and the nozzle portion 82 is fitted into the nozzle hole 78. When this happens, a gap is formed between the nozzle hole 78 and the nozzle hole 78. Note that 94 is a temperature sensor for detecting the temperature of the nozzle 64, and the amount of current supplied to the conducting wire 85 is controlled based on the output signal of this sensor 94.
The nozzle 64 is heated to an appropriate temperature.

During injection molding, a current is passed through the conductive wire 85, which generates heat mainly at the tip of the nozzle part 82, causing the cavity 1 to heat up.
The flow of the resin into the passage 72 is maintained well, and the resin in the passage 72 is kept in a fluid state. Nozzle 64 inner body and conducting wire 85
etc. constitute the heating device, and the structure of the heating device is simple, and the thermal decomposition of the resin due to excessive heating, the resulting retention of the resin in the passage 72, and the resulting color change during color change. Mixing is prevented and the amount of current required for heating is small.

After the filling is completed, if the resin filled in the cavity 18 is cooled and solidified, the supply of current to the conducting wire 85 is cut off. As a result, the temperature at the tip of the nozzle portion 82 decreases rapidly compared to other portions, and the temperature at the tip of the large diameter portion 80. Nozzle part 82
While the resin inside is kept in a molten state, the resin inside the tip of the nozzle part 82 is semi-solidified, which prevents the resin from flowing backward when the screw 54 retreats and from leaking from the nozzle part 82 when taking out the product. . The resin inside the nozzle tip does not completely solidify, so it is not removed from the molded product.

In the injection molding apparatus configured as described above, the mold is replaced by retracting the movable platen 16 together with the movable mold 20 to open the mold, and then retracting the injection cylinder 50 and removing the nozzle 64 from the nozzle hole 78. The nozzle 64
desirable to prevent damage to However, it is also possible to carry out the process without retracting the injection cylinder 50 and with the nozzle 64 still inserted into the nozzle hole 78. In either case, the fixed mold 12 is removed from the fixed platen 10 by loosening the bolts 15, but the hot runner device 60 including the nozzle 64 remains on the injection molding machine side, and only the fixed mold 12 is removed. .

After removal, if the nozzle 64 remains fitted in the nozzle hole 78, a new fixed mold 12 is fitted to the nozzle 64 and then fixed to the fixed platen 10. In addition, if the nozzle 64 has been pulled out from the nozzle hole 78, the nozzle 64 is fitted into the nozzle hole 78 after fixing the stationary mold 12 to the stationary platen 10, or the nozzle 64 is fitted into the nozzle hole 78 before fixing. 10.
After inserting into the part formed by the locate ring 14, the fixed mold 12 is fixed.

In the above embodiment, the product extrusion device 22 was provided between the movable platen 16 and the movable mold 20, but as in the product extrusion device 100 shown in FIG.
It may be provided between the fixed mold 104 and the fixed mold 104. The fixed mold 104 is fixed to a mounting plate 106 fixed to the fixed platen 102 with bolts 110 via a plurality of spacer blocks 10B, and a space is provided for arranging the extrusion device 100.

The configuration of the extrusion device 100 is almost the same as the extrusion device 22 described above, except that the extrusion plate 112 is moved by a chain 114.

The chain 114 is stretched between the extrusion plate 112 and the mounting plate 118 fixed to the movable platen 116, but it is in a relaxed state when the mold is closed, and is movable when the product is taken out. As the platen 116 is separated from the fixed platen 102, it becomes in a tensioned state, and as the movable platen 116 is further retreated from this state, the extrusion plate 11
2 to the fixed mold 104 against the biasing force of the spring 120.
, and the ejector pins 122 and 123 extrude the product.

Further, the nozzle 126 of the hot runner device 124 is attached to a mounting block 128 via a sprue bush 130. The sprue bush 130 is the fixed plate 102
．． Mounting plate 106. Penetrating the extrusion plate 112, the nozzle 126
has a length necessary to fit into the nozzle hole 132, and therein is a passage 138 that communicates a branch passage 134 formed in the mounting block 128 with a passage 136 in the nozzle 126. It is formed. On the outside of this sprue bushing 130 is a heating wire 14 for heating the sprue bushing.
0 is wound, and a conducting wire 142 for heating the nozzle part is inside the part where the heating wire 140 is wound.
is buried. This conducting wire 142 is connected to a nozzle 126, and the nozzle 126 generates heat in the same manner as in the previous embodiment to heat the resin within the passage 136.

The other functions and effects of the configuration 9 are the same as those of the previous embodiment, and corresponding parts are given the same reference numerals and detailed explanations are omitted.

Note that in each of the above embodiments, the hot runner device 60
．． 124 is fixed to the injection cylinder 50, but it may be fixed to the fixed platen 10.102. In that case, in each of the above embodiments, the hot runner device 60.1
24 to the injection cylinder 50, the fixing plate 10
．． It may be fixed to 102. In addition, a recess 7 is provided in the fixed plate 10.
6, the nozzle part of the hot runner device should be long enough to pass through the fixed plate and fit into the nozzle hole, and the base should be the end face of the fixed plate on the opposite side from the side where the fixed mold is fixed. It may be fixed to .

When implementing the 7) runner injection molding method according to the present invention, the hot runner device may be fixed from the movable platen side. In that case, a recess is formed in the surface of the fixed platen that faces the movable platen, and the mounting block 128 is placed in the recess.
It is also possible to arrange something similar to the above, or to fix it on the surface of the fixed plate facing the movable plate without forming a recess.

In the former case, the stationary mold may be attached to a stationary platen.

In the latter case, a hot runner device is interposed between the fixed mold and the fixed platen, but the fixed mold is attached to the fixed platen via the hot runner device, or A spacer may be provided in the spacer, and the stationary mold may be fixed to the stationary platen via the spacer.

When installing in a recess or fixing to the end face of a fixed plate, the end face of the base of the hot runner device on the fixed mold side must be in the same plane as the end face of the fixed plate or the end face of the spacer. Once positioned, the stationary mold can be supported over its entirety in one plane.

Further, the heating device for the nozzle part is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-3720.
The resin in the runner may be heated by providing a heater in a portion of the nozzle part that forms the runner or by providing a heater in the runner.

Furthermore, although the above embodiments are examples of injection molding using a multi-cavity mold, the present invention can also be applied when injection molding is performed using a mold that molds products one by one. It is possible to apply.

Furthermore, the present invention can be applied not only to injection molding of thermoplastic resins but also to injection molding of thermosetting resins.

Although not illustrated in detail, the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing the main parts of an injection molding apparatus according to an embodiment of the present invention. FIG. 2 is a front sectional view showing the nozzle portion of the hot runner device in the injection molding apparatus. FIG. 3 is a front sectional view showing the main parts of an injection molding apparatus according to another embodiment of the present invention. 10: Fixed plate 12: Fixed mold 16: Movable plate
18: Cavity 20: Movable mold 60
: Hot runner device 62: Mounting block 64: Nozzle 68: Resin supply port 70: Branch passage 72: Passage
73; Runner 78: Nozzle hole 85: Conductor 102: Fixed plate 104: Fixed mold 116: Movable plate 124: Hot runner device 126: Nozzle
128: Mounting block 134: Branch passage 13
6. t3a: Passage 142: Conductor

Claims (3)

[Claims] (1) A hot runner device comprising a runner that connects the injection cylinder to the cavity formed by the fixed mold and the movable mold, and a heating device that heats the synthetic resin in the runner is attached to the fixed mold. and the injection cylinder to injection mold a product; a step of removing the fixed mold from the injection molding apparatus while leaving the hot runner device on the injection molding apparatus side; A hot runner injection molding method comprising the step of attaching another fixed mold to an injection molding apparatus in which the runner device remains. (2) A fixed plate that is installed in a fixed position and to which a fixed mold is attached, and a movable mold that is installed so that it can approach and move away from the fixed plate and forms a cavity together with the fixed mold. a movable platen, an injection cylinder provided on the opposite side of the stationary platen to the side to which the fixed mold is fixed, and supplies synthetic resin in a fluid state to the cavity; a base connected to the injection cylinder; A nozzle part is provided integrally with the base part and is fitted into a nozzle hole provided through the fixed platen and the fixed mold; It has a runner that guides the resin into the cavity and a heating device that heats the synthetic resin in the runner,
A hot runner type injection molding apparatus comprising: a hot runner apparatus fixed to the fixed plate from a side opposite to the side to which the fixed mold is fixed. (3) The hot runner type injection molding apparatus according to claim 2, wherein the hot runner device is fixed to the injection cylinder at the base.