JP2022067731A - Manufacturing method for molded products - Google Patents

Abstract

To provide a method for manufacturing molded products with improved dimensional accuracy.SOLUTION: A method of producing a molded product includes the following steps of: placing a molten resin sheet 2 between a first mold 4 and a second mold 5; compressing an excess thick-walled portion 221 of the molten resin sheet 2 by the first mold 4 and the second mold 5 through mold clamping; and applying at least one of negative pressure from the first mold 4 side and positive pressure from the second mold 5 side to shape the molten resin sheet 2 against the first mold 4 side.SELECTED DRAWING: Figure 5

Description

The present invention relates to a method for producing a molded product.

Conventionally, a technique for forming a molded body by shaping a molten resin sheet into a mold has been proposed. For example, in Patent Document 1, one sheet of molten thermoplastic resin material is arranged between a pair of split molds, and the sheet is sucked from the cavity side of one mold to form the other mold. A molding method is disclosed in which a sheet is pressed from the cavity side and the sheet is pressed against one of the molds to form a shape.

Patent No. 5440093

In a molding method such as Patent Document 1 in which one surface side of a molten resin sheet is shaped into a mold and molded, the cooling rate differs between the surface on the side in contact with the mold and the surface on the opposite side. Further, the molten resin sheet extruded from the extruder may not have a uniform sheet thickness, and the cooling rate of the thick portion having a thick sheet may be slower than that of other portions having a thin sheet thickness. If such a difference in cooling speed becomes large, the molded body may be warped and the dimensional accuracy may be lowered.

An object of the present invention is to provide a method for manufacturing a molded product with improved dimensional accuracy.

The method for producing a molded product of the present invention includes a step of arranging a molten resin sheet between the first mold and the second mold, and the excess thick portion of the molten resin sheet by mold clamping to the first mold and the first mold. The molten resin sheet is placed on the first mold side by applying at least one of the step of compressing by the second mold and the negative pressure from the first mold side and the positive pressure from the second mold side. It is characterized by including a step of shaping.

According to the present invention, it is possible to provide a method for manufacturing a molded product with improved dimensional accuracy.

It is a perspective view of the molded body which concerns on embodiment of this invention. It is a schematic diagram which shows the molding apparatus of the molded body which concerns on embodiment of this invention, and shows the state which arranged the molten resin sheet and the skin member between the 1st mold and the 2nd mold. It is a figure which shows the state in the process of molding the 1st mold and the 2nd mold in the manufacturing process of the molded body which concerns on embodiment of this invention. In the manufacturing process of the molded product according to the embodiment of the present invention, a state is shown in which the first mold and the second mold are molded and the surplus pressure-walled portion is in contact with the first mold and the second mold. It is a figure which shows the state which the 1st mold and the 2nd mold were molded, and the molten resin sheet and the skin member were shaped to the 1st mold side in the manufacturing process of the molded body which concerns on embodiment of this invention. be.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of the molded body 1 of the present embodiment. The molded body 1 has a recessed portion 1a on the center side. A flange portion 1b is formed around the outer peripheral edge of the recessed portion 1a. The molded body 1 is formed by a resin member 11 formed by deforming a sheet-shaped thermoplastic resin material described later, and a skin member 12 attached to one side of the resin member 11. The skin member 12 can be made of a breathable sheet-like non-woven fabric such as PET (polyethylene terephthalate) fiber, nylon fiber, cellulose fiber, and aramid fiber.

The molded body 1 can be configured as, for example, an inner trim of an automobile door or the like. The skin member 12 side of the molded body 1 is formed as a design surface on the living space side of the automobile. Various functional portions can be provided in the recessed portion 1a of the molded body 1. The flange portion 1b may be provided with a screw hole portion or the like that can be connected to another structure (for example, a member inside the door member). The molded body 1 is not limited to the inner trim, but may be other structural members.

FIG. 2 is a diagram showing the resin molding apparatus 60 of the present embodiment. The resin molding device 60 molds the molten resin sheet 2, which is a sheet-shaped resin material, by the resin supply device 61. The molten resin sheet 2 is formed of a non-foamable resin material. As the resin material of the molten resin sheet 2, for example, a thermoplastic resin such as polyolefin can be used, and as the polyolefin, low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, and ethylene-propylene co-weight. Examples thereof include coalescence and a mixture thereof. Below the resin supply device 61, a first mold 4 and a second mold 5, which are split dies, are arranged.

The resin supply device 61 includes a hopper 65, which is a supply port for the resin material, an extruder 66, which melts and kneads the material supplied from the hopper 65 by a screw connected to the hydraulic motor 68 and arranged inside. Has. The extruder 66 is connected to an accumulator 70 including a plunger 72. The melted and kneaded resin material is sent to the accumulator 70 by the extruder 66. The resin material is subjected to high pressure by the accumulator 70 and sent to the T die 71. Then, the die slit of the T die 71 is opened at an appropriate timing, and the molten resin sheet 2 sent out by the roller 79 is formed.

The first mold 4 and the second mold 5 are arranged so as to face each other. In this embodiment, the case where the first mold 4 is a convex mold and the second mold 5 is a concave mold is shown. The molding surface 4a inside the pinch-off portion 4b of the first mold 4 includes the core portion 41. A plurality of intake holes 4a1 are provided on the molded surface 4a. The molding surface 4a side of the first mold 4 can be sucked in by a vacuum pump (not shown) through the intake hole 4a1 to reduce the pressure.

Further, the molding surface 5a inside the pinch-off portion 5b of the second mold 5 includes the cavity portion 51 corresponding to the core portion 41. The set width T3 (clearance) between the molding surface 4a and the molding surface 5a when the first mold 4 and the second mold 5 are molded is formed substantially constant in the molding region of the molten resin sheet 2. (See also Figure 5). A plurality of exhaust holes 5a1 are provided on the molded surface 5a. The molded surface 5a side of the second mold 5 can be pressurized by introducing compressed air through a compressor (not shown) through the exhaust hole 5a1.

Next, the details of each step of the manufacturing method of the molded body 1 will be described. The molded body 1 manufactured in this embodiment is molded by the resin molding apparatus 60 shown in FIG. 2 and the like. First, in the material supply step, the resin supply device 61 extrudes the molten resin sheet 2 and arranges it between the first mold 4 and the second mold 5. Further, between the molten resin sheet 2 and the first mold 4, a skin member 3 (skin member 12) that covers the design surface side (recessed portion 1a side) of the molded body 1 shown in FIG. 1 is arranged. .. The molten resin sheet 2 and the skin member 3 are supported by a robot hand or the like (not shown).

In the mold clamping step, as shown in FIGS. 3 to 5, the first mold 4 and the second mold 5 are molded, and the molten resin sheet 2 and the skin member 3 are shaped to the first mold 4 side. .. First, as shown in FIG. 3, the first mold 4 and the second mold 5 are relatively close to each other. The molten resin sheet 2 and the skin member 3 located between the first mold 4 and the second mold 5 are also relatively close to each other.

When the first mold 4 and the second mold 5 are brought closer to each other, as shown in FIG. 4, the molten resin sheet 2 and the skin member 3 have the molding surface 4a of the first mold 4 and the second mold 5. It is deformed to follow the uneven shape of 5a. FIG. 4 shows a state immediately before the first mold 4 and the second mold 5 are molded and closed.

At the position shown in the enlarged view of the P portion, the sheet thickness T1 including the molten resin sheet 2 and the skin member 3 is formed to have substantially the same thickness as the preset sheet thickness T2. The molten resin sheet 2 supplied from the resin supply device 61 may have a variation in resin thickness T0 due to various factors such as swell, drawdown, and neck-in. As shown in the enlarged view of the Q portion, a surplus thick portion 221 having a relatively thick resin thickness T0 is formed on a part of the molten resin sheet 2 of the present embodiment. In FIG. 4, in the surplus thick portion 221, the surface 21 on one side of the molten resin sheet 2 comes into contact with the molding surface 4a of the first mold 4 with the skin member 3 in between, and the surface 22 on the other side is the second. The state in which the mold 5 is in contact with the molding surface 5a is shown.

On the other hand, in the thin portion 222 (including other regions thinner than the set sheet thickness T2) shown in the enlarged view of the P portion and the enlarged view of the R portion thinner than the surplus thick portion 221, the first mold 4 and the second mold are used. When the mold 5 is molded, spaces S1 and S2 (gap) are formed on one or both sides between the molten resin sheet 2 and the skin member 3 in the thin portion 222 and the first mold 4 and the second mold 5. Is formed.

Further, the molten resin sheet 2 is shaped along the core portion 41. Therefore, the molten resin sheet 2 arranged on the side peripheral portion of the core portion 41 (for example, the periphery of the inside corner portion 4a2 shown in the enlarged view of the R portion) is stretched to have a relatively thin sheet thickness T1. Spaces S1 and S2 are also formed around the inside corner portion 4a2 on one side or both sides between the molten resin sheet 2 and the skin member 3 and the first mold 4 and the second mold 5.

When the opposite pinch-off portions 4b and 5b of the first mold 4 and the second mold 5 come into contact with the molten resin sheet 2 and the skin member 3, the molding surfaces 4a and 5a of the first mold 4 and the second mold 5 A closed space is formed inside the side.

The first mold 4 takes in air from the intake holes 4a1 and depressurizes the space S1 on the molding surface 4a side of the molten resin sheet 2 and the skin member 3. Since the skin member 3 has air permeability, the molten resin sheet 2 is sucked toward the molding surface 4a by reducing the pressure. The first mold 4 can start depressurization before or after the pinch-off portions 4b and 5b come into contact with the molten resin sheet 2 and the skin member 3. Further, the second mold 5 introduces compressed air from the exhaust hole 5a1 to pressurize the space S2 between the surface 22 of the molten resin sheet 2 and the molding surface 5a. The molten resin sheet 2 is urged toward the molding surface 4a even by pressurization.

FIG. 5 shows a state in which the first mold 4 and the second mold 5 are completely closed, and the molten resin sheet 2 and the skin member 3 are shaped toward the first mold 4. As shown in the enlarged view of the P'part and the enlarged view of the R'part in FIG. 5, the skin member 3 is pushed to the molded surface 4a side by the molten resin sheet 2 that moves by decompression and pressurization to the molding surface 4a side. Be urged. Therefore, the molten resin sheet 2 and the skin member 3 are surface-contacted so as to overlap each other and are formed on the molded surface 4a. The skin member 3 is welded to the molten resin sheet 2.

Both the negative pressure from the first mold 4 side and the positive pressure from the second mold 5 side are applied to the molten resin sheet 2 and the skin member 3 of the present embodiment. Therefore, the surface 21 on the side of the first mold 4 can be molded together with the skin member 3 with high dimensional accuracy. The negative pressure on the first mold 4 side can be applied at a timing earlier than the positive pressure on the second mold 5 side. For example, the depressurization on the molding surface 4a side of the first mold 4 is performed while moving one or both of the first mold 4 and the second mold 5 and compacting the mold. Further, the depressurization can be started from the timing before the molten resin sheet 2 and the skin member 3 come into contact with the first mold 4. The molten resin sheet 2 and the skin member 3 are relatively easily placed at the tip contact portion such as the core portion 41 shown in FIG. 3 even before the first mold 4 and the second mold 5 are completely closed due to negative pressure. It is formed on the 4 side of one mold. In the vicinity of the recesses such as the inner corner portion 4a2, the molten resin sheet 2 and the skin member 3 are pushed into the convex portion of the molding surface 5a of the second mold 5 and deformed to imitate the molding surface 4a. The molten resin sheet 2 and the skin member 3 that are close to the molding surface 4a up to a predetermined distance are shaped toward the molding surface 4a by negative pressure. Then, after the first mold 4 and the second mold 5 are completely closed (see FIG. 5), pressurization is performed from the molding surface 5a side of the second mold 5.

As a result, the molten resin sheet 2 and the skin member 3 are preliminarily shaped in the first mold 4, and the positive pressure from the second mold 5 side ensures higher pressure to the first mold 4 side. Can be shaped into. Further, when a positive pressure is applied, it is possible to apply a pressure higher than the atmospheric pressure as compared with the case where a negative pressure is applied. Therefore, when the molten resin sheet 2 and the skin member 3 are shaped toward the first mold 4 by applying a positive pressure as in the present embodiment, the vicinity of the corner portion 4a2 shown in the enlarged view of the R'part in FIG. Also, the molten resin sheet 2 and the skin member 3 can be molded along the molding surface 4a with high dimensional accuracy.

Further, the set width T3 between the molding surface 4a and the molding surface 5a when the mold is fastened is equal to or more than the set sheet thickness T2 of the molten resin sheet 2 and equal to or less than the sheet thickness T4 (see FIG. 4) in the surplus thick portion 221. Is set to. For example, the setting sheet thickness T2 of the present embodiment is set to about 2 mm, and the set width T3 is set to about 3 mm. The skin member 3 can be set to less than 1 mm. Therefore, in the portion where the sheet thickness T1 is formed to be equal to or less than the set sheet thickness T2 (for example, the portion shown in the P'part enlarged view and the Q'part enlarged view), the space S2 is formed even in the mold clamping state. On the other hand, in the surplus thick portion 221, the molten resin sheet 2 and the skin member 3 are sandwiched by the first mold 4 and the second mold 5, and the surplus thickness of the molten resin sheet 2 is moved to the surrounding space S2 side. It is compressed while flowing. Therefore, the excess thick portion 221 of the molten resin sheet 2 is thinned to the preset width T3 (see the enlarged view of the Q'part).

In the present embodiment, since the surface 22 of the surplus thick portion 221 having the sheet thickness T4 thicker than the set width T3 abuts on the molding surface 5a of the second mold 5, heat can be dissipated from the second mold 5. can. Therefore, the difference in the cooling rate in the molten resin sheet 2 can be reduced, and the occurrence of deformation such as warpage of the molded body 1 can be reduced.

In the taking-out step, the first mold 4 and the second mold 5 are opened, and the molded body 1 made of the molten resin sheet 2 and the skin member 3 is taken out. When the burr portion 13 is connected to the removed molded body 1, the burr portion 13 is manually or automatically removed to create the molded body 1 shown in FIG. In the molded body 1 of FIG. 1, the resin member 11 is a layer formed by the molten resin sheet 2, and the skin member 12 is a layer formed by the skin member 3.

When shaping the molten resin sheet 2 and the skin member 3, one of a negative pressure from the first mold 4 side and a positive pressure from the second mold 5 side may be applied. This makes it possible to simplify the configuration and manufacturing process of the first mold 4 or the second mold 5.

In the method for manufacturing the molded body 1 of the present embodiment, the step of arranging the molten resin sheet 2 between the first mold 4 and the second mold 5 and the surplus thick portion 221 of the molten resin sheet 2 are formed by mold clamping. The molten resin sheet 2 is subjected to at least one of a step of compressing by the first mold 4 and the second mold 5 and a negative pressure from the first mold 4 side and a positive pressure from the second mold 5 side. The process of shaping on the 4 side of one mold and the configuration including the process have been described. As a result, it is possible to construct a manufacturing method of the molded body 1 in which the variation in the cooling rate in the molten resin sheet 2 is reduced, the occurrence of warpage of the molded body 1 is reduced, and the dimensional accuracy is improved.

Although the embodiment of the present invention has been described above, the present invention is not limited to the present embodiment and can be implemented with various modifications. For example, in the present embodiment, the first mold 4 is a convex mold and the second mold 5 is a concave mold, but the first mold 4 is a concave mold and the second mold 5 is a convex mold. May be good. Alternatively, the first mold 4 and the second mold 5 may be provided with a plurality of corresponding convex surfaces and concave surfaces, respectively, and may be formed in parallel so that the distance between the facing surfaces (set width T3) is substantially constant. good.

Further, the molten resin sheet 2 may be formed of a foamable resin material which is a thermoplastic resin produced by mixing a foaming agent with a base resin. When the molten resin sheet 2 is formed of a foamable resin material, it is possible to form a molded body 1 that is lightweight and has improved heat insulating properties. On the other hand, when the molten resin sheet 2 is formed of a non-foamable resin material, the molded body 1 can be inexpensively formed by a simple step by omitting the step of mixing the foaming agent and the like.

Further, in the present embodiment, the molded body 1 in which the molten resin sheet 2 and the skin member 3 are stacked is shown, but the skin member 3 may be omitted and the molten resin sheet 2 may be used as the molded body 1. In this case, the sheet thickness T1 shown in FIG. 4 is set to be the same as the resin thickness T0.

Further, the set width T3 (clearance) between the molding surface 4a and the molding surface 5a when the first mold 4 and the second mold 5 are molded covers the entire molding region of the molten resin sheet 2. It may be formed to be constant, or it may be formed to be constant in a part of the molding region.

Further, in the present embodiment, the one-piece mold capable of molding one molded body 1 by the first mold 4 and the second mold 5 has been described, but the first mold 4 and the second mold 5 have been described. May be configured as a multi-cavity mold capable of molding a plurality of molded bodies.

1 Molded body 1a Recessed part 1b Collar part 2 Molten resin sheet 3 Skin member 4 First mold 4a Molded surface 4a1 Intake hole 4a2 Inner corner part 4b Pinch-off part 5 Second mold 5a Molded surface 5a1 Exhaust hole 5b Pinch-off part 11 Resin Member 12 Skin member 13 Burr part 21 Face 22 Face 41 Core part 51 Cavity part 60 Resin molding device 61 Resin supply device 65 Hopper 66 Extruder 68 Hydraulic motor 70 Accumulator 71 T Die 72 Plunger 79 Roller 221 Extra thick part 222 Thin part S1, S2 Space S2 Space T0 Resin thickness T1 Sheet thickness T2 Setting sheet thickness T3 Setting width T4 Sheet thickness

Claims (7)

The process of arranging the molten resin sheet between the first mold and the second mold,
A step of compressing the excess thick portion of the molten resin sheet by the first mold and the second mold by mold clamping.
A step of forming the molten resin sheet on the first mold side by applying at least one of a negative pressure from the first mold side and a positive pressure from the second mold side.
A method for producing a molded product, which comprises. The first aspect of claim 1, wherein the molten resin sheet is shaped to the first mold side by applying both a negative pressure from the first mold side and a positive pressure from the second mold side. The method for manufacturing a molded product according to the description. 1 or claim 1, wherein a skin member is arranged between the molten resin sheet and the first mold, and the molten resin sheet and the skin member are shaped to the first mold side. Item 2. The method for manufacturing a molded product according to Item 2. The set width between the molded surface of the first mold and the molding surface of the second mold when the mold is fastened is set to be equal to or greater than the set sheet thickness of the molten resin sheet and equal to or less than the sheet thickness of the excess thick portion. The method for producing a molded product according to any one of claims 1 to 3, wherein the molded product is characterized by the above. The method for manufacturing a molded product according to claim 4, wherein the set width is constant in the molding region of the molten resin sheet. Any of claims 1 to 5, wherein a gap is formed between the thin portion in the molding region of the molten resin sheet and the molding surface of the second mold in the mold clamping. A method for manufacturing a molded product according to the product. The method for producing a molded body according to any one of claims 1 to 6, wherein the molten resin sheet is formed of a non-foamable resin material.

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