JP3010250B2 - Molding method of thermoplastic resin sheet - 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 forming a thermoplastic resin sheet having a design on the upper surface.

[0002]

2. Description of the Related Art Various molding methods are known for vacuum molding of a thermoplastic resin sheet depending on the purpose and the form of a molded article. For example, a so-called plug assist, in which a heat-softened sheet s fixed on a female mold a is pushed into the female mold a by a plug p, and vacuum suction is performed from the female mold a side to form the sheet s in close contact with the inner surface of the mold. Forming (FIG. 4 ), a female mold a is provided in the chamber c, and the heated softened sheet s fixed on the chamber c is pushed up by pressurized air to perform pre-stretching. So-called air-slip molding (Fig. 5 ) in which the vacuum is suctioned from the female mold a side and the sheet is closely adhered to the inner surface of the mold to perform molding.
Sandwiching the heat-softened sheet s between the lower female die a and the upper die b,
After pre-stretching the sheet s by sending pressurized air from the upper mold b, vacuum suction is performed from the female mold a side, and the sheet is closely adhered to the inner surface of the mold to form the sheet s.
FIG. 6 ).

[0003]

By the way, when a design pattern is shown on one surface of a thermoplastic resin sheet,
Forming the sheet by the above-described conventional forming method has the following disadvantages. That is, in the method of (1), the design portion is damaged by the plug because the design surface is pressed by the plug. In addition, when molding is performed by blowing out pressurized air from the plug, the air lowers the sheet temperature, thereby limiting the elongation of the sheet. In the above method, the degree of pre-stretching of the sheet is substantially determined by the chamber structure. Therefore, in order to increase the degree of elongation, the internal pressure of the chamber must be increased to a normal 200 mmH2.
It is necessary to set it higher than O, and to make the structure of the chamber and the seat clamp better, and to maintain the internal pressure and the temperature control of the pressurized air. It has the disadvantage of being expensive. In the method of (2), the sheet is sandwiched between the female mold and the upper mold, so that a sheet that is one size larger than the size of the product to be formed must be used, and the yield of the sheet material deteriorates. Under such circumstances, development of a new forming method suitable for forming the sheet has been demanded.

Accordingly, an object of the present invention is to form a thermoplastic resin sheet having a design pattern on one surface into a deep drawn shape of good quality so as not to damage the design portion, and The present invention proposes a molding method that has a simple structure and reduces equipment costs.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a thermoplastic resin sheet having a design applied to an upper surface is heated and softened, and the lower surface of the thermoplastic resin sheet is heated and softened. After performing pre-stretching by pushing up with a plug,
At the molding station, the female mold is raised and brought into contact with the thermoplastic resin sheet, and then the thermoplastic resin sheet is sucked from the vacuum suction hole of the female mold, thereby bringing the thermoplastic resin sheet into close contact with the inner surface of the female mold. It is characterized by being molded.

In order to achieve the same object, the invention according to claim 2 is provided with a step of heating and softening a thermoplastic resin sheet having a design on its upper surface, so that a plug split mold and another split split mold are provided. And a female mold formed from the mold, and the split mold for the plug and the split mold are respectively provided so as to be vertically movable, and the lower surface of the heat-softened thermoplastic resin sheet is formed at the molding station by the split mold for the plug. After pushing up and performing pre-stretching, the split mold for plug is lowered to the molding position, and then the split mold is raised to the molding position to be integrated with the split mold for plug. The method is characterized in that the thermoplastic resin sheet is formed in close contact with the inner surface of the female mold by sucking the sheet.

The invention according to claim 3 is provided with a step of heating and softening a thermoplastic resin sheet having a design provided on an upper surface,
A female mold formed from a plug split mold and another split split mold, and the plug split mold and the split mold are provided so as to be vertically movable, and the plug split mold is heated at a molding station. After rising to the softened thermoplastic resin sheet surface and adsorbing the thermoplastic resin sheet, it is lowered to the molding position in this state and pre-stretched, and then the split mold is raised to the molding position to split the plug. It is characterized in that the thermoplastic resin sheet is made to adhere to the inner surface of the female mold by sucking the thermoplastic resin sheet from the vacuum suction holes of the split mold for the plug and the split mold. .

[0008]

[Action] In the invention described in this claim 1-3 which is configured so as to apply the pretension by pulling from the lower surface (back surface) direction of the thermoplastic resin sheet after suction by pushing up or plug in a plug So
The plug is not in contact with the upper surface (surface) representing the design pattern by printing or the like. Therefore, since the design portion of the thermoplastic resin sheet is not damaged at all, a molded product of good quality can be obtained. In the forming method of these inventions, since the preliminary stretching step is provided, particularly, a thick sheet or a strong sheet such as a bathtub or a basin ball having a design on the inner surface is deep drawn. Most suitable for molding into a form. Further, since the thermoplastic resin sheet can be adjusted to an arbitrary thickness by controlling the plug shape, the female mold structure, the stretching speed, and the like, the thermoplastic resin sheet can be applied to a wide variety of female molds. it can.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a model diagram illustrating a first embodiment of the method for forming a thermoplastic resin sheet of the present invention, FIG. 2 is a model diagram illustrating a second embodiment of the method for forming a thermoplastic resin sheet, and FIG.
FIG. 4 is a model diagram for explaining a third embodiment of a method for forming the same thermoplastic resin sheet.

(First Embodiment) In FIG. 1, reference numeral 1 denotes a thermoplastic resin sheet (hereinafter abbreviated as a sheet) having a thickness of about 0.8 to 6 mm and made of polyethylene, polypropylene, acrylic, polycarbonate or the like. On one upper surface (front surface) 1a, a design pattern is represented by printing or the like, and the lower surface (back surface) 1b of the sheet 1 is blank. As shown in FIG. 1 (i), when the heat-softened sheet 1 is transported to the pre-stretching station with both side edges clamped by the clamp frame 2, the plug 3 waiting below the sheet 1 rises. The lower surface 1b of the sheet 1 is pushed up, and the preliminary stretching shown in (ii) is performed. When the plug 3 is lowered after pre-stretching, the sheet 1 is transferred to the molding station and set on the cavity side of the female mold 4. When the female mold 4 rises and comes into contact with the lower surface 1b of the sheet 1 and stops, the air in the cavity is sucked from the vacuum suction hole 5 of the female mold 4 and discharged to the outside as shown in (iii). Thereby, the sheet 1 is shaped along the inner surface shape in close contact with the inner surface 6 of the female mold 4 and molding is performed. Then, when the vacuum suction is stopped and the female mold 4 is lowered to the original standby position, the sheet 1 after molding is transferred to the next trimming step and trimmed as usual.

(Second Embodiment) In FIG. 2, a female mold 10 is formed of a central split mold 11 for a plug and other split molds 12, and the split mold for a plug 11 and the split mold 12 are formed. Are provided so as to be vertically movable. As shown in FIG. 2 (i), when the heat-softened sheet 1 is set on the cavity side of the female mold 10, only the plug split mold 11 waiting below the sheet 1 rises, and The lower surface 1b is pushed up, and the preliminary extension shown in (ii) is performed. After the pre-stretching is performed, the plug split mold 11 is lowered to the molding position. Then, the split mold 12 is raised to the molding position to be integrated with the plug split mold 11 so as to conform to the shape of the molded product. Then, as shown in FIG. Is sucked and discharged to the outside. As a result, the sheet 1 is formed in close contact with the inner surface 13 of the female mold 10 along the inner surface shape. Then, the vacuum suction is stopped, and the plug split mold 11 and split mold 12 of the female mold 10 are simultaneously lowered to the original standby position. Thereafter, the sheet 1 is transferred to a trimming step and trimmed as in the first embodiment.

(Third Embodiment) In this embodiment , when the female mold 30 composed of the central plug mold 31 and the other divided molds 32 is at the standby position, first, the plug mold is used. Only the split mold 31 is raised and lowered to the forming position with the lower surface 1b of the sheet 1 being sucked, and the pre-stretching shown in FIG. 3 (ii) is performed. Then, after it allowed to conform to the molded article shape integral with the plug split mold 31 to raise the split die 32 to a molding position, shown in (iii)
So that the vacuum suction holes 31 of the split molds 31 and 32
The air in the cavity is sucked from a and 32a and discharged to the outside. As a result, the sheet 1 is formed in close contact with the inner surface 33 of the female mold 30 along the inner surface shape. Then true
The idle suction is stopped and the plug split molds 31 and 32 are
Sometimes it descends to its original standby position. After that, sheet 1
Is transferred to the trimming process and trimmed
You.

[0013]

The molding method of the present invention has the above-described structure and operation, and is suitable for forming a thermoplastic resin sheet having a design pattern or a clear layer on one surface without damaging the design portion. It can be formed into a deep drawn shape of high quality. Furthermore, since the molding device used in this device has a simple structure, there is an advantage that equipment costs can be reduced.

[Brief description of the drawings]

FIG. 1 shows a first method of forming a thermoplastic resin sheet according to the present invention.
Model diagram for explaining the embodiment

FIG. 2 is a model diagram illustrating a second embodiment of the method for forming the thermoplastic resin sheet.

FIG. 3 is a model diagram for explaining a third embodiment of the method for forming the thermoplastic resin sheet.

FIG. 4 is a model diagram for explaining conventional plug assist molding.

FIG. 5 is a model diagram for explaining conventional air slip molding.

FIG. 6 is a model diagram illustrating conventional straight forming.

[Explanation of symbols]

1 → thermoplastic resin sheet 1 a → upper surface 1 b → lower surface 2
→ Clamp frame 3 → Plug 4 → Female 5 → Vacuum suction hole 6 → Inner surface 1
0 → female mold 11 → split mold for plug 12 → split mold 12a → vacuum suction hole 13 → inside 30 → female 31 → split mold for plug 31a → vacuum suction hole 32 → split mold 32a → vacuum suction hole 33 → inside a → female type b → upper type c → chamber p → plug s
→ Sheet

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 51/00-51/46

Claims (3)

(57) [Claims] 1. A thermoplastic resin sheet having a design applied to its upper surface is softened by heating, and the lower surface of the thermoplastic resin sheet is pushed up by a plug to perform pre-stretching. The thermoplastic resin sheet is brought into contact with the thermoplastic resin sheet and then suctioned from the vacuum suction hole of the female mold to form the thermoplastic resin sheet in close contact with the inner surface of the female mold. A method for forming a resin sheet. 2. A step of heating and softening a thermoplastic resin sheet having a design applied to an upper surface thereof, comprising a female mold formed of a split mold for a plug and another split split mold. A split mold and a split mold are provided so as to be vertically movable, and the lower surface of the heat-softened thermoplastic resin sheet is pushed up by the plug split mold at the forming station and pre-stretched, and then the plug split mold is formed. Position, and then raise the split mold to the molding position to integrate it with the split mold for the plug, and suck the thermoplastic resin sheet from the vacuum suction holes of the split mold, thereby forming the thermoplastic resin on the inner surface of the female mold. A method for forming a thermoplastic resin sheet, comprising forming a resin sheet in close contact with the resin sheet. 3. A step of heating and softening a thermoplastic resin sheet having a design applied to an upper surface thereof, comprising a female mold formed from a split mold for a plug and other split molds. A split mold and a split mold are provided so as to be movable up and down, and the plug split mold is raised to a heated and softened thermoplastic resin sheet surface at a molding station to adsorb the thermoplastic resin sheet, and the molding position is set in that state. After performing pre-stretching by lowering the mold to the molding position, the split mold is raised to be integrated with the split mold for the plug, and then the thermoplastic resin sheet is sucked from the vacuum suction holes of the split mold for the plug and the split mold. A method for forming a thermoplastic resin sheet, wherein the thermoplastic resin sheet is formed in close contact with the inner surface of a female mold.