JP2865248B2 - Injection compression molding method by partial compression - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injection-compression molding of a synthetic resin, and more particularly, to a method for molding a large-sized injection-molded article such as a suitcase into a thin wall by the injection compression molding method, and a mold therefor. About.

[0002]

2. Description of the Related Art There are various methods for molding a synthetic resin. One of typical molding methods is an injection molding method. In the case of injection molding, when a resin is injected into a mold, the flow distance of the resin is closely related to the gap between the molds. In the case of large molded products, thin resin products can be obtained by injecting resin from multiple gates, but in this case, weld lines stand out where the resin injected from each gate meets, and emphasis is placed on appearance. The product has disadvantages. Therefore, it is desirable to inject the resin from one point of the gate. However, due to the fluidity of the resin, if the resin is made thin, the resin cannot reach the terminal and does not become a product. Therefore, the thickness becomes more than necessary, and the weight of the product also increases.

On the other hand, there is an injection compression molding method as a molding method for solving the above problem. In this injection compression molding method, a fixed amount of resin suitable for the molded product is injected and injected into the place where the mold gap is larger than the final molded product by the compression allowance, and when the injection is completed and the gate seal is completed, Immediately, the mold is clamped to apply pressure to the resin so that the resin flows and the resin is filled up to the end of the mold. In this method, the resin is injected while the mold is slightly opened as compared with a general injection molding method. Therefore, a mold structure for preventing the resin from leaking from the parting surface is required. Conventionally, as a mechanism for preventing the resin from leaking from the parting surface, as shown in FIG. 8, the cavity side mold 1 and the core side mold 2 are completely fitted in an in-row manner so that the resin from the parting face a An outer sealing method in which a sealing block 101 urged by a spring 100 is provided on the outer periphery as shown in FIG. 9 so that the sealing block 101 always seals the parting surface a. The block method is often adopted.

[0004]

However, in the above-mentioned in-row system and outer peripheral seal block system, when a molded product having a simple end surface is easy to mold, the molded product is large in size and moreover. When the end face becomes curved or becomes complicated, the molding becomes complicated and expensive, and the mold is squeezed during the molding, so that there is a problem in the life of the mold. Fig. 7
In the case where the side surface has an undercut as shown in (1), there is a problem that molding cannot be performed.

[0005] The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object a large-
Molding is easy and inexpensive even for products with complicated shapes on the end surface, making it difficult for molds to stick during molding and molding molded products with undercuts on the side. An object of the present invention is to provide a novel injection compression molding method and a mold for use in the method.

[0006]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the injection compression molding method of the present invention is directed to a method of injection compression molding of a synthetic resin, the method comprising: The mold is divided into a ceiling inner surface forming die and a side wall inner surface forming die, and the side wall inner surface forming die is slidable up and down on the peripheral surface of the ceiling inner surface forming die, and an inclined surface is formed on a lower surface of the side wall inner surface forming die. By providing a wedge member for press-fitting under the inclined surface of the lever, the wedge member is advanced to lift the side wall inner surface forming die, and the die is placed in a state where the die is positioned above the inner surface molding die by a compression allowance. Tighten, so that only the ceiling part has a mold gap larger than the thickness of the final molded product,
Injecting the resin into the part, finishing the injection of the resin and completing the gate seal, the compression step, and in the side wall inner surface mold part, the relationship between the cavity side mold and the core side mold before the compression step While maintaining the mold-clamped state, only the ceiling portion is partially compressed to cause the resin to flow under pressure and to fill the end of the mold.

According to the injection compression molding method, since the compression is performed at the ceiling portion, the parting surfaces for clamping the mold on the cavity side and the core side have the same structure as that of the conventional injection mold, and the injection compression molding is performed. No complicated structure is required. Therefore, even if the product to be molded is large and has a complicated end face, the mold can be easily formed at low cost. In addition, the mold is less likely to be squeezed during molding, and it is possible to mold a molded article having an undercut portion on the side surface and to perform a lateral hole processing by a pin penetration method.

The mold used in this injection compression molding method comprises a mold on the cavity side for molding the outer surface of the three-dimensional molded article, and a mold on the core side for molding the inner surface of the molded article. The core-side mold is divided into (a) a ceiling inner surface forming die and a side wall inner surface forming die. (B) The side wall inner surface forming die is vertically slidable on the peripheral surface of the ceiling inner surface forming die. The lower portion has a portion that forms a parting surface by being engaged with the lower end surface of the cavity-side mold.
Has an inclined surface on the lower surface, and having (d) is force applying means is actuated to advance or retreat by sliding on the inclined surface, the wedge member can be press-fitted into the bottom of the inner surface of the side wall mold.

If the injection compression molding method is performed using the mold having such a configuration, the wedge member is advanced to raise the side wall inner surface forming die so that the side wall inner surface forming die becomes higher between the inner wall surface and the ceiling. Since a step can be provided, a mold gap which is larger than the thickness of the final product by an amount corresponding to the compression allowance can be provided in the ceiling portion in a state where the parting surface is sealed by mold clamping. Therefore, if the resin is injected into the ceiling portion in this state, the resin can be easily injected and retained in this portion without applying excessive pressure. If the mold is advanced while increasing the mold clamping pressure and retracting the wedge member, the cavity-side mold descends, the gap in the ceiling decreases, and the resin remaining in the mold gap in the ceiling is compressed. Then, it flows into the mold gap in the side wall portion and is filled with uniform pressure to the end of the mold. As a result, the distortion of the internal stress of the molded product can be reduced, and a product without warpage or deformation can be produced. Since the outer parting surfaces on the core side and the cavity side of the mold are increased from the required mold clamping pressure at the time of resin injection to the maximum mold clamping pressure required at the time of final filling, resin leakage does not occur.

In the case of a small molded product, a method of directly supporting the inner mold of the side wall with a spring or a hydraulic cylinder without using a wedge mechanism is conceivable, but in the case of a spring, it is possible only with a very small molded product due to the supporting force. In the case of a hydraulic cylinder, a large-sized molded product requires a large-diameter hydraulic cylinder, which causes problems such as a problem of an installation place, a stroke adjusting mechanism, and a separate pump in the same manner as a hydraulic pump. According to the present invention, as will be described later, the hydraulic cylinder supporting the wedge may be small in diameter, has a small amount of oil, can be operated by a hydraulic pump incorporated in a normal injection molding machine, and the mold can be thin and compact.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 5 illustrate the injection compression molding method of the present invention according to the steps. In the drawings, a substantially flat and rectangular ceiling or bottom (hereinafter, referred to as a ceiling) and a square of the ceiling are described. The figure shows the case of molding a molded article, such as a suitcase shell, having a continuous side wall at the periphery via a suitable curved shoulder.

First, a mold used for carrying out the injection compression molding method of the present invention will be described. A mold A includes a cavity-side mold 1 for molding the outer surface of a molded product (product) B, and a mold A inside the molded product B. A cavity-side mold 1 is attached to an upper mold plate 11, and a core-side mold 2 is attached to a lower mold plate 21, respectively. In this embodiment, the upper die plate 11 is a movable die plate, and the lower die plate 21
Is a fixed mold board. In addition, a normal injection molding machine is a horizontal type, and a mold plate is opened and closed in the left and right directions.

The cavity-side mold 1 has substantially the same structure as the cavity-side mold of ordinary injection molding, and has a molding recess 12 having a shape corresponding to the entire shape of the outer surface of the molded product B.
And is attached to the upper mold plate 11 such that the molding concave portion 12 opens downward.

On the other hand, the core side mold 2 is a base 4 having a ceiling inner surface forming die 3 for forming the inner surface of the ceiling portion of the molded product B.
And a side wall inner surface forming die 5 formed separately from the base 4 and assembled to the base 4 to form an inner surface from a shoulder portion of the molded product B to a lower end of the side wall portion.
The base 4 has a central portion protruding in an upright shape.
41, the ceiling inner surface forming mold 3 is formed at the upper end portion,
A step portion 42 is provided on four sides of the base portion.

The side wall inner surface forming mold 5 is provided in a frame shape surrounding the protrusion 41 so as to be able to slide up and down around the ceiling inner surface forming mold 3 formed on the base body 4, and the lower end thereof is provided with the protrusion part. In the state of being mounted and locked on the step portion 42 of 41, the molding surfaces of both the side wall inner surface forming die 5 and the ceiling inner surface forming die 3 have the shape of the inner surface of the final molded product. At the lower end of the side wall inner surface forming die 5, there is a horizontal portion 51 projecting outward in a flange shape. When the die A is clamped, the upper surface of the horizontal portion 51 and the lower end surface 13 of the cavity side die 1 are formed. The parting surface a is formed by palming together, and the lower surface of the horizontal portion 51 is formed on a flat surface corresponding to the step portion 42 of the base portion of the base 41. With an appropriate width left, an inclined surface 53 inclined downward toward the flat portion 52 side is provided. Between the inclined surface 53 and the upper surface of the base body portion 43 around the step portion 42, the upper surface is on the tip side. Member 6 inclined downward toward
Is inserted, and the lower end of the side wall inner surface forming die 5 rides on the wedge member 6.

The wedge members 6 are respectively provided on four sides of the upper surface of the base 4 so as to correspond to the respective sides of the side wall inner surface forming die 5 and communicate with hydraulic cylinders 61 provided on the periphery of the base 4, respectively. By the operation of the cylinder 61, the side wall inner surface forming die 5 is formed.
With respect to the inclined surface 53 of the side wall inner surface forming die 5.
And the base portion 43 of the base 4 can be pressed forward. The wedge member 6 may be provided on two opposing sides depending on the size and shape of the molded product. By press-fitting the wedge member 6, the side wall inner surface forming die 5 can be lifted and its upper surface can be located above the upper surface of the ceiling inner surface forming die 3, but the rear portion of the wedge member 6 has a horizontal portion of the side wall inner surface forming die 5. 51, the wedge member 6
A stopper 62 is provided for restricting the forward movement of the side wall inner surface forming die 5 in a state where the stopper 62 abuts against the flange-shaped horizontal portion 51 of the side wall inner surface forming die 5 and stops moving. 3 is higher than the upper surface by the compression allowance. Reference numeral 7 denotes a gate with a shut-off valve 71 for injecting resin into the core-side mold, which is provided with an opening at the center of the ceiling inner surface molding die 3.

Next, the injection compression molding method of the present invention carried out using the mold A will be described. First, the hydraulic cylinder 61 provided on the core side mold 2 is operated, and the wedge member 6 is advanced until the stopper 62 abuts on the outer periphery of the horizontal portion 51 of the side wall inner surface forming die 5, and the side wall inner surface forming die 5 is moved upward. The upper surface is pushed up (see FIG. 3), and the upper surface thereof is positioned above the upper surface of the ceiling inner surface forming mold 3 by an amount corresponding to the compression allowance.

Subsequently, as shown in FIG. 4, the movable mold plate 11 is operated to be constituted by the lower end surface 13 of the cavity side mold 1 and the upper surface of the horizontal portion 51 of the side wall inner surface forming mold 5 of the core side mold 2. The cavity side mold 1 is lowered until the parting surface a comes into contact, and is held at the initial mold clamping pressure.

Here, the mold clamping pressure will be described. When the cavity-side mold 1 is lowered until the parting surface a comes into contact, the upper surface of the side wall inner surface forming die 5 is located above the upper surface of the ceiling inner surface forming die 3 by an amount corresponding to the compression allowance. (Mold gap) b at the ceiling is larger than the size of the molded product. It is assumed that the gap b for injecting the resin is several mm larger than the product size at the ceiling. In addition, the molding pressure of the injection compression of the resin used is 20
If it is 0 kg / cm ² , the final clamping pressure required from the size of the molded product is 800 tons. Even if the resin required for molding is injected, the volume inside the mold is larger than that of the molded product, so that the resin does not fill up to the end of the mold gap b, and the injection pressure is not fully applied. Internal pressure of resin is 100kg
/ Cm ² . Therefore, the initial required clamping force is 400
Tons. Assuming that the ceiling portion of the projected area of the product is 2/3, the pressing force applied to the side wall inner surface forming die 5 is 130 tons. Since this force is received by the wedge member 6, the wedge member 6
Is reduced to 1/3 using the inclination of the tapered surface of
The wedge member 6 at the location can be held by eight hydraulic cylinders having an output of 5.5 tons. Therefore, if the mold plate 11 is clamped with 400 tons, the entire mold is clamped with 400 tons.

The molten resin c corresponding to the product weight is injected from the gate 7 into the mold gap b of the mold A for which the initial mold clamping has been completed. First, the resin c is filled in the ceiling b1 in which the volume of the mold gap b is increased, and flows into the side wall b2 sequentially. When the fixed amount injection of the resin c is completed, as shown in FIG. 5, the shutoff valve 71 of the gate 7 is closed so that the resin c does not flow backward. At this time, at this time, the relief valve (not shown) of the cylinder is opened, and the oil in the cylinder is discharged in synchronization with the increase in the mold clamping pressure. At this time, by adjusting the oil discharge amount, the wedge member 6 retreats, the side wall inner surface forming die 5 descends while the tightening pressure of the parting surface a increases, and the flat portion 52 on the inner peripheral side at the lower end thereof. Contacts the step 42 of the base 4. At this time, the mold clamping force is the best 80
Reach 0 tons.

As the mold gap b1 at the ceiling decreases due to the lowering of the mold 5 for molding the inner surface of the side wall, the resin c in the mold A flows under pressure and fills up to the end of the mold. The tightening pressure on the parting surface a is gradually increased from 400 tons to 80 at the final molding.
Since it is 0 tons, no resin leakage occurs. Also,
The advantage of injection compression molding can be realized without warping or distortion of the molded product due to excessive injection of resin in ordinary injection molding.

In the above-described embodiment, the case where the appearance of the molded article is emphasized has been described. However, when the inner surface of the molded article is emphasized, the mold structure is reversed to the above description, and the ceiling surface of the cavity is formed. May be compressed. Further, in the above description, the resin is injected from the single point gate on the inner surface of the ceiling, but a method of injecting the resin from the side gate to the ceiling surface may be optionally employed.

Next, an embodiment shown in FIG. 6 shows an embodiment of a mold for molding a molded product B having an undercut 9 on a side wall 8 as shown in FIG. The cavity-side mold 1 and the core-side mold 2 are provided with undercut forming portions 15 and 25, respectively, as separate members.

The core-side undercut forming portion 25 has an undercut concave portion 26 at a required position on its surface, and extends from an upper end to a horizontal portion 51 for forming a parting surface a at a required portion of the side wall inner surface forming die 5. In the normal state, the lower end is engaged with the horizontal portion 51 and the upper end is the upper end of the side wall inner surface forming die 5. It is aligned with.
The front surface of the mounting portion 55 of the side wall inner surface forming die 5 and the rear surface of the undercut forming portion 25 in contact with this surface are tapered surfaces inclined downward and outward, respectively.

On the other hand, the undercut molded portion 15 on the cavity side is fitted into the concave portion 26 of the undercut molded portion 25 on the core side with the center portions thereof aligned with each other and the inner surface of the concave portion 26 is filled with the meat of the product B. It is formed in a block shape capable of forming a gap corresponding to the thickness, and is removably fitted into a mounting hole 16 formed in the cavity-side mold 1 and protrudes from the inner surface of the mold 1. ing. The mounting hole 16 is provided at a position corresponding to the concave portion 26 of the undercut molding portion 26 on the core side when the mold A is clamped.

Undercut 9 using a mold having such a structure
The injection compression molding of the product B having the above is basically the same as that of the embodiment described above, and thus is omitted to avoid duplication of the description. Until the parting surface a formed by the lower end surface 13 of the side mold 1 and the upper surface of the side wall inner surface forming mold horizontal portion 51 of the core side mold 2 is held together and held at the initial mold clamping pressure,
The undercut molding part 15 is removed from the cavity side mold 1, and after the mold clamping is completed, the undercut molding part 15 is attached before injecting the resin, and the undercut molding part 15 is attached to the core side mold 2. 25 so as to fit into the recess 26. And this undercut forming part 15
When the mold B is opened after molding and the product B is released, the product B is removed from the cavity side mold 1 before opening the mold.

On the other hand, since the undercut forming portion 25 on the core side is engaged with the undercut 9 on the inner surface side of the product B, the undercut forming portion 25 is removed together with the product B from the side wall inner surface forming die 5 of the core side mold 2. Then, it is removed from the product B.

By using such a mold, the mold can be clamped, opened, and the product can be released without any support. At the time of molding, in the side wall portion where the undercut of the outer peripheral portion is formed, the core side, The state in which the cavity side is firmly clamped is maintained, and there is no relative movement, so that an undercut can be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold used in an injection compression molding method by partial compression according to the present invention, showing a state immediately before mold clamping.

FIG. 2 is a sectional view taken along the line (2)-(2) of FIG.

FIG. 3 is an enlarged cross-sectional view of one half of a mold, showing a state where a side wall inner surface forming mold of a core-side mold is lifted by a compression allowance.

FIG. 4 shows a state in which mold clamping is completed and resin is injected in the enlarged sectional view.

FIG. 5 shows a state in which a compression step is performed in the enlarged sectional view.

FIG. 6 is a cross-sectional view showing a mold for molding a product having an undercut.

FIGS. 7A and 7B show a product having an undercut formed by using the above mold, wherein FIG. 7A is a plan view and FIG. 7B is a side view.

FIG. 8 is a sectional view of a main part showing a resin leakage prevention mechanism of an in-row system using a mold of a conventional injection compression molding method, and (a).
Shows the state at the time of resin injection, and (b) shows the state at the time of the compression step.

FIG. 9 is a cross-sectional view of a main part showing a resin leakage prevention mechanism of an outer peripheral seal block method using a mold according to a conventional injection compression molding method, (a) showing a state at the time of resin injection, and (b) showing a state during a compression step. Respectively are shown.

[Explanation of symbols]

A: Mold B: Molded product (product) 1: Cavity mold 2: Core mold 3: Ceiling inner mold 5: Side wall inner mold 6: Wedge member 51: Part forming parting surface (horizontal) Part) 53: Inclined surface 61: Force applying means (hydraulic cylinder) a: Parting surface b: Mold gap c: Resin

Continuation of front page (56) References JP-A-6-106589 (JP, A) JP-A-7-241890 (JP, A) JP-A-6-106590 (JP, A) JP-A-8-323816 (JP, A) JP-A-3-173623 (JP, A) JP-A-3-119,000 (JP, A) JP-A-1-119326 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB Name) B29C 45/00-45/84

Claims (2)

(57) [Claims] In a method for injection-compression molding of a synthetic resin, a core-side mold for molding the inner surface of a three-dimensional molded product is divided into a ceiling inner surface forming die and a side wall inner surface forming die, and the side wall inner surface forming die is mounted on the ceiling side. The wedge member is made to slide forward and downward by forming a slope on the lower surface of the side wall inner surface forming die and providing a wedge member which is press-fitted below the inclined surface. The mold is lifted, and the mold is tightened in a state where the mold is positioned above the inner mold of the ceiling by a compression allowance, so that only the ceiling part has a mold gap larger than the thickness of the final molded product, Injecting the resin into the part, finishing the injection of the resin and completing the gate sealing, the compression process after the gate molding is completed, and the relationship between the cavity side mold and the core side mold in the side wall inner surface mold part is the mold before the compression step. While maintaining the tightened state, only the ceiling part is partially Injection compression molding method, characterized in that condensation to the resin is pressurized flows, is filled up to the end of the mold. 2. A mold on the cavity side for molding the outer surface of a three-dimensional molded article, and a mold on the core side for molding the inner surface of the molded article, wherein the core-side mold comprises: a. It is divided into a ceiling inner mold and a side wall inner mold. b. The side wall inner surface forming die is slidable up and down on the peripheral surface of the ceiling inner surface forming die, and has a portion on its side surface which forms a parting surface with the lower end surface of the cavity side die. c. The side wall has an inclined surface on the lower surface of the inner surface forming die. d. It has a wedge member which is actuated by the force applying means, slides on the inclined surface to advance and retreat, and is press-fitted below the side wall inner surface forming die. A mold for injection compression molding, characterized in that: