JP3310271B1 - Injection molding method - Google Patents

Abstract

The present invention provides an injection molding method that reduces a mold clamping force from both the projected area of a molded article and an injection pressure, and also contributes to energy saving and reduction in equipment cost and manufacturing cost. A first gate (21) for injecting a first molten resin (101) ahead of one end (a filling start side) in a longitudinal direction of a cavity (13) formed in an injection molding die (5), and the like. On the end side (filling completed side), a second gate 22 for subsequently injecting the second molten resin 102 is arranged. Then, the second molten resin 102 is newly injected from the second gate 22 before the flow leading portion of the first molten resin 101 injected from the first gate 21 reaches the position of the second gate 22. Further, by the time the second molten resin 102 reaches the end of the cavity 13 on the filling completion side, the first molten resin 101 is substantially in a cooled and solidified state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method suitable for a long molded article, such as a resin part for automobiles.

[0002]

2. Description of the Related Art For example, an elongated resin product such as a protector for a wiring harness of an automobile is generally manufactured by an injection molding machine. An injection molding machine has an injection device that melts and injects a resin material and a mold clamping device that clamps a mold at high pressure, and its capability is often indicated by “mold clamping force”. The “clamping force” is represented by the product of “the projected area of the molded product on a plane perpendicular to the mold moving direction” and “average resin pressure in the mold”. The larger the value of (representation), the larger the device, and the higher the equipment cost. For example, even a long resin product having a length of about several tens of cm requires a mold clamping force of about 200 tons, and therefore, there is a demand for downsizing of equipment by reducing the mold clamping force.

[0003] Conventionally, in order to reduce the mold clamping force, a method of mainly reducing the injection pressure (and, consequently, the average resin pressure in the mold has been reduced) has been adopted. As such a low-pressure molding method, a method of injecting a molten resin into a cavity of a mold in a half-open state and clamping the mold before solidifying, or injecting a predetermined amount of the molten resin into a cavity, and There is known a method in which a molten resin filled in another sub-chamber (resin reservoir) is pushed into a cavity and clamped before solidification.

[0004]

However, even in these low-pressure molding methods, the necessity of distributing the molten resin to every corner in the cavity does not change, so that the injection pressure (and, consequently, the average resin pressure in the mold) is sufficiently increased. And there is a limit in reducing the mold clamping force.

An object of the present invention is to provide an injection molding method which reduces the mold clamping force from both the projected area of the molded product and the injection pressure, and also contributes to energy saving and reduced equipment and manufacturing costs. It is in.

[0006]

Means for Solving the Problems and Effects of the Invention In order to solve the above-mentioned problems, an injection molding method according to the present invention comprises filling a cavity formed in an injection mold with one end in a longitudinal direction of a molten resin. initiator, and set the other end to the completion of filling side, wherein the second gate of the first gate and the filling completion side of the filling starting side disposed, or not a first gate for injecting the molten resin into the cavity Inject resin into the cavity from, then inject resin into the cavity from the second gate,
By the time the molten resin injected from the second gate reaches the cavity end on the filling completion side, the molten resin injected from the first gate is substantially cooled and solidified .
A time difference is provided between the injection timings of the first gate and the second gate, and the flow leading portion of the preceding molten resin injected from the first gate does not reach the position of the second gate, and from the first gate. The projected area of the injected resin is made larger than the projected area of the resin injected from the second gate, and the cavity portion not filled with the resin injected from the first gate is the projected area of the resin from the first gate. When Ru is filled with a resin from the second gate of the smaller projected area than the
In both cases, the projected area of the injection resin from the second gate is
The injection resin of the first and second gates is provided with a projection area difference so as to be about one third or less of the total projection area of the entire tee , and finally the entire cavity is filled with the resin. I do.

[0007]

From this, the substantial projected area to be filled with the molten resin injected from the second gate on the filling completion side is considerably smaller than the total projected area of the cavity (the cooling area has already been cooled and solidified). The projected area of the part decreases). on the other hand,
The area to be filled by the molten resin injected from the second gate is reduced only by the already cooled and solidified part in the cavity, so that it is not necessary to spread the molten resin to every corner of the cavity. Thus, the injection pressure (and, consequently, the average resin pressure in the mold) can be reduced. Therefore, at the time of injection from the second gate that determines the maximum mold clamping force, it is possible to reduce the substantial projected area of the molded product,
In addition, since the injection pressure can be reduced, the mold clamping force can be reduced from both the projected area of the molded product and the injection pressure.

Furthermore, the injection molding method according to the present invention, morphism <br/> out mold is divided into the fixed mold and the movable mold, the core part is formed in the protruding shape in the central portion in the movable mold In the fixed mold, a longitudinal cavity is formed corresponding to the core portion, and the core portion is fitted into the cavity to be in a mold-clamped state, and thereafter there is a time lag from the first gate and the second gate. And the molten resin can be injected.

In this case, the substantial projected area to be filled by the second molten resin injected from the second gate is the projection area of the portion where the first molten resin injected from the first gate has already cooled and solidified in the cavity. The area can be reduced, for example, to about 1/3 of the total projected area of the cavity. On the other hand, the range in which the second molten resin is to be filled can be reduced only in the portion where the first molten resin has already been cooled and solidified in the cavity as described above, and the injection pressure can be correspondingly reduced. As described above, the mold clamping force can be significantly reduced from both the projected area of the molded product and the injection pressure.

[0011]

Embodiments of the present invention will now be described with reference to the embodiments shown in the drawings. FIG. 1 is a sectional view showing one embodiment of an injection molding machine used in the present invention. The injection molding machine 1 uses an injection mold 5 (hereinafter simply referred to as a mold) to mold a molded article such as a resin part for an automobile (for example, a long part such as a protector for a wiring harness of an automobile). An injection device 3 for manufacturing and melting a molding material such as a synthetic resin and injecting it into a mold 5, and a mold clamping device (not shown) for opening and closing the mold 5 and fixing it with high pressure. Have.

The mold 5 is divided into a fixed mold 7 located on the upper side in the figure and a movable mold 9 located on the lower side. Movable type 9
Has a core portion 11 (male type) formed at the center thereof in a protruding shape, while the fixed die 7 has a cavity 13 (female type) which is a space filled with the molten resin corresponding to the core portion 11. ) Is formed. The fixed mold 7 is attached to a fixed die plate 15 located further above, and the movable mold 9 is attached to a movable die plate 17 located further below. The movable die plate 17 is vertically movable toward and away from the fixed die plate 15, and is connected to a mold clamping device (not shown) that allows the mold 5 to be opened and closed.

In FIG. 1, the cavity 13 is elongated in the left-right direction.
A first gate 21 opening at one end in the longitudinal direction (left-right direction) and opening on the filling start side, and a second gate 22 opening on the other end and opening on the filling completion side. Is formed. Further, the first gate 21 is fixed 7
Sprue 1 penetrating vertically through the inside of the
The first nozzle 23 at the tip of the first injection device 3 is connected to the second nozzle 24 at the tip of the second injection device 4 via the sprue 20. .

The first injection device 3 and the second injection device 4
Are hoppers 25 for storing molding materials such as resin, respectively.
And a cylinder 27 for storing a molten resin obtained by heating and melting the molding material 150, and a screw 29 for feeding the molten resin to the cavity 13 in the cylinder 27.

Next, an injection molding method using the injection molding machine 1 and the mold 5 will be described with reference to FIGS. First, as a preparation stage of the injection molding process, the movable die plate 17 is brought close to the fixed die plate 15,
A mold clamping step for closing the core 11 (male type) and the cavity 13 (female type) of the mold 5, and the nozzles 23 and 24 of the injection devices 3 and 4 are moved and fixed to the nozzle receiving portions of the fixed die plate 15. A nozzle touch process and the like are performed (FIG. 1
reference).

In such a state, the first injection device 3
A first injection step of injecting a molten resin at a predetermined temperature heated and melted in the cylinder 27 from the first nozzle 23 through the first gate 21 into the cavity 13 of the mold 5 by advancement of the screw 29 is performed. You. As shown in FIG. 2A, the flow leading portion of the first molten resin 101 (preceding molten resin) injected from the first gate 21 is also located at the longitudinal start end (left side in the figure) in the cavity 13. It also gradually flows to the terminal side (right side in the figure). Then, the flow leading portion of the first molten resin 101 first reaches the longitudinal start end in the cavity 13 to complete the filling to the filling start side, and expands the filling region to the end side. Note that no injection is performed from the second gate 22 in the first injection step.

Next, when the leading portion of the flow of the first molten resin 101 reaches a position slightly closer to the longitudinal end (closer to the first gate 21) than the position of the second gate 22, the injection from the first gate 21 is performed. Is stopped, and a second injection step of newly injecting the second molten resin 102 (subsequent molten resin) from the second gate 22 into the cavity 13 is performed (FIG. 2).
(B)). Since the second molten resin 102 can be injected without closing the second gate 22 by the flow leading portion of the first molten resin 101, the injection pressure of the second molten resin 102 (substantially the injection pressure of the entire injection molding machine 1) ) Can be reduced.

The leading portion of the second molten resin 102 flows toward the longitudinal start end in the cavity 13 and comes into contact with the leading portion of the first molten resin 101. At this time, since the flow head of the first molten resin 101 and the flow head of the second molten resin 102 are both in a molten state, both flow heads are in such a degree that the resin materials do not cause a problem in strength. (FIG. 3A).

On the other hand, the flow leading portion of the second molten resin 102 also flows to the terminal end in the longitudinal direction in the cavity 13, and when reaching the filling end, filling of the cavity 13 from the second gate 22 is completed. (FIG. 3B). However, the flow head of the second molten resin 102 is the cavity 1
By the time it reaches the end on the filling completion side in 3, the first molten resin 101 is in a substantially cooled and solidified state. Therefore, the substantial projected area filled with the second molten resin 102 is reduced by the projected area of the portion where the first molten resin 101 has already been cooled and solidified in the cavity 13, and the injection pressure is correspondingly reduced. I get stuck.

The molded product injection-molded in the cavity 13 as described above is further cooled by the cooling water flowing through the mold 5, and the operation of the mold clamping device in the direction opposite to the above-described mold clamping process. The mold 5 is removed from the mold 5 through a mold opening step in which the mold 5 is separated by a pressing mechanism, a projecting step in which the mold is ejected by an ejecting mechanism (not shown), and the like.

In the second injection step, when the leading portion of the flow of the first molten resin 101 reaches a predetermined position, the injection from the first gate 21 after a predetermined time has elapsed from the start of injection from the second gate 22. May be stopped to shorten the injection molding time. In this case, the injection flow from the first gate 21 may be gradually reduced simultaneously with the start of the injection from the second gate 22, and the injection may be stopped after a predetermined time has elapsed.

In the second injection step, the injection start timing from the second gate 22 (the position of the leading edge of the flow of the first molten resin 101 at the start of injection), the cooling / solidification timing of the first molten resin 101 Can be determined by trial, but may be automatically adjusted using, for example, a position sensor at the head of the flow.

In the present invention, the first molten resin 10
The first and second molten resins 102 are the same in color, material, etc.
In addition to the ones, for example, those with different colors and / or materials
There may be. It is also suitable when there are three or more gates.
Used.

[0024]

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an injection molding machine used in the present invention.

FIG. 2A illustrates an injection molding process according to the present invention.
-A sectional drawing.

FIG. 3 is an explanatory view following FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 injection molding machine 5 mold (mold for injection molding) 13 cavity 21 first gate (preceding gate) 22 second gate (subsequent gate) 101 first molten resin (preceding molten resin) 102 second molten resin (subsequent melting) resin)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-156033 (JP, A) JP-A-2000-94491 (JP, A) JP-A-6-344398 (JP, A) JP-A-3-288609 (JP, A) JP-A-2001-179786 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (3)

(57) [Claims] 1. A longitudinal cavity formed in an injection mold is set at one end in a longitudinal direction of a molten resin filling side, and the other end is set at a filling completed side, and the molten resin is filled in the cavity. and a second gate of the first gate and the filling completion side of the filling initiator injection place, the resin is injected from the first gate into the cavity not a Well, then the resin is injected into the cavity from the second gate, by the time the molten resin injected from the second gate reaches the cavity end of the filling completion side, as molten resin injected from the first gate is in a state of being substantially cooled and solidified, the first gate
And a time difference is provided in the injection timing of the second gate , and further, the leading flow of the preceding molten resin injected from the first gate does not reach the position of the second gate,
And, the projected area of the resin injected from the first gate is larger than the projected area of the resin injected from the second gate,
Cavity portion not filled with resin injected from the first gate, Ru is filled with a resin from the second gate of the smaller projected area than the projected area of the resin from the first gate
The projected area of the injection resin from the second gate
A projection area difference is provided in the injection resin of the first and second gates so as to be about one third or less of the total projection area of the whole bitty .
Finally, the whole cavity is filled with resin. 2. The injection mold according to claim 1, wherein said mold is a fixed mold or a movable mold.
Divided, the movable mold has a core part protruding in the center
The fixed mold has a longitudinal shape corresponding to its core.
A cavity is formed, and the core is
And fixed and movable mold surfaces
To close the mold.
To inject molten resin with a time lag from the
The injection molding method according to claim 1. 3. The first injection device is connected to the first gate.
The second injection device is independently connected to the two gates.
The first injection device creates a tree from the first gate into the cavity.
Grease, and then the second injection device allows keying from the second gate.
The injection according to claim 1 or 2, wherein the resin is injected into the cavity.
Out molding method.