JP2004034564A - Manufacturing method for mold for foam molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a term of works for manufacturing a mold for molding a foamed molded product such as a seat cushion pad or the like for a vehicle. <P>SOLUTION: A manufacturing method for a mold for foam molding includes a process for forming the model 24 of a foamed molded product 10, a process being a process for manufacturing sand molds 34, 36 and 42 as casting molds from the obtained model 24 and adapting flexible sheets 26a and 26d to at least a shape transfer surface to solidify sand 32 by vacuum suction to form sand molds and a process for casting a mold 12 for foam molding using the obtained sand molds 36 and 42. <P>COPYRIGHT: (C)2004,JPO

Description

【００２５】
表１に示すように、本実施形態によれば、従来方法に比して、金型作製のための工期を大幅に短縮することができ、開発工数の短縮化、試作品の短納期化を図ることができる。
【００２６】
【発明の効果】
本発明によれば、砂型を作製する際に形状転写面に可撓性シートを用いることによりモデルが直接砂に接するのを回避することができ、そのため、モデルの表面処理工数を削減することができる。また、砂を真空吸引により所定の形状に保持するものであるため、砂の硬化時間を待たずに次工程に進むことができる。以上より、金型の作製工期を従来よりも格段に短縮することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態において成形対象とするシートクッションパッドの斜視図である。
【図２】同実施形態において作製する金型の発泡成形時における断面図である。
【図３】同実施形態に係る金型製造方法の工程を示すフローチャートである。
【図４】同実施形態において下型用鋳型を作製する工程のフローチャートである。
【図５】（ａ）〜（ｄ）は捨て型の作製工程における断面図である。
【図６】（ａ）〜（ｅ）は製品面側砂型の作製工程における断面図である。
【図７】（ａ）〜（ｄ）は裏面側砂型の作製工程における断面図である。
【図８】下型の鋳造するための鋳型の断面図である。
【図９】従来の金型製造方法の工程を示すフローチャートである。
【符号の説明】
１０……シートクッションパッド
１２……金型
２４……モデル
２６ａ〜ｅ……可撓性シート
３０……吸引口
３２……砂
３４……捨て型（第１砂型）
３６……製品面側砂型（第２砂型）
３８……表層
４２……裏面側砂型（第３砂型）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a mold for molding a foam molded article such as a vehicle seat cushion pad.
[0002]
Problems to be solved by the prior art and the invention
A foaming mold for molding a foamed article of synthetic resin such as a cushion pad used for a seat of a vehicle such as an automobile is formed by foaming from a two-dimensional design drawing and data of the foamed article and three-dimensional CAD data. An article model is produced, a mold for metal casting is produced with a sand mold or the like based on the model, and the mold is produced by casting using the mold.
[0003]
At this time, in order to prepare a sand mold as a mold, a resin is previously mixed with the sand, a model is buried in the sand, and the sand is hardened by the resin to obtain a mold having a predetermined shape. As described above, in the conventional sand mold production, since the model is directly buried in the sand, a surface treatment for protecting the model surface is necessary, and the model production process takes much time. In addition, it takes a considerable amount of time to cure the sand mold with the resin, and it is not possible to proceed to the next step until the curing is completed.
[0004]
Conventionally, there is a case where sand is solidified by vacuum suction to produce a sand mold as a mold. In this case, conventionally, as shown in FIG. Is prepared, and a sand mold as a mold is produced from the resin mold by vacuum suction. In this case, although it is not necessary to wait for the curing time by the resin as described above when preparing the sand mold, it takes a considerable amount of time to produce the resin mold, and the fact is that the production period of the mold has not been shortened at all. .
[0005]
Recently, there has been an increasing demand from automakers for shorter development man-hours and shorter delivery times of prototypes. It is extremely important in shortening the lead time.
[0006]
The present invention has been made in view of such a point, and an object of the present invention is to shorten a manufacturing period of a foaming mold.
[0007]
[Means for Solving the Problems]
The method for producing a mold for foam molding according to the present invention includes a step of producing a model of a foam molded article, and a step of producing a sand mold as a mold from the obtained model. And a step of hardening the sand by vacuum suction to produce a sand mold, and a step of casting a mold for foam molding using the obtained sand mold.
[0008]
The sand mold making step is a step of making a first sand mold having an inverted shape of one surface from the model, and interposing a flexible sheet between the sand for the first sand mold and the model. And solidifying the sand by vacuum suction, and producing a second sand mold having the same shape as the one surface of the model from the first sand mold, wherein the sand for the second sand mold is vacuum-sucked. Setting a surface layer having a thickness corresponding to the thickness of the mold on the one surface of the model, and producing a third sand mold having an inverted shape of the surface layer from the model having the surface layer. And a step of interposing a flexible sheet between the sand for the third sand mold and the surface layer to solidify the sand by vacuum suction.
[0009]
ADVANTAGE OF THE INVENTION According to the manufacturing method of this invention, since a flexible sheet will be interposed between a model surface and sand at the time of producing a sand mold, a model does not directly contact sand. Therefore, man-hours for surface treatment of the model can be reduced. Further, since the sand is solidified by vacuum suction and held in a predetermined shape, the process can proceed to the next step without waiting for a long curing time as in the case of curing with a resin.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method for manufacturing a mold for foam molding according to an embodiment of the present invention will be described with reference to the drawings.
[0011]
The present embodiment relates to a method for manufacturing a mold 12 shown in FIG. 2 for molding the seat cushion pad 10 for automobiles made of the flexible polyurethane foam shown in FIG. 1 as a foam molded product. The mold 12 includes a lower mold 14 that opens upward, and an upper mold 16 that opens and closes an upper surface opening of the lower mold 14. Specifically, the lower mold 14 is a mold for molding the upper surface (front surface) side of the pad, and has a concave portion corresponding thereto. The upper die 16 is a die for molding the lower surface (back surface) side of the pad. By closing the concave portion, the upper die 16 corresponds to the pad shape between the lower die 14 and the inside of the contact surface (PL portion) 18. A cavity, which is a foaming space, is formed.
[0012]
The outline of the procedure for manufacturing the mold 12 is as shown in FIG.
[0013]
(1) First, a model of a foam molded article is prepared. The model can be created from a two-dimensional design drawing or data, but it is preferable to create NC processing data from three-dimensional CAD data of a foam molded product, and to manufacture the model based on the NC processing data. At this time, the model is made of a solid standard material for processing such as a metal material such as aluminum, wood, or a synthetic resin material. The NC machining is not limited to machining by various NC machine tools that perform cutting, but also includes electric discharge machining based on NC data. Preferably, an NC processing machine incorporating "msg (Machining Strategist)" (registered trademark of NC Graphics (Cambridge), UK) as software for converting CAD data to NC processing data, and a high-precision contour control device Is to produce a model by high-speed NC processing using
[0014]
(2) Next, a sand mold as a mold is produced from the produced model. The sand mold is manufactured by sandwiching sand with a flexible sheet such as a polyethylene sheet, solidifying the sand by vacuum suction, and holding the sand in a predetermined shape.
[0015]
In detail, as shown in FIG. 4, the sand mold for casting the lower mold 14 includes (2-1) a discard mold making step, (2-2) a product side sand mold making step, and (2-3). ) A sand mold for casting the upper mold 16 is produced in the same manner as the sand mold for producing the upper mold 16.
[0016]
(2-1) The disposal mold manufacturing process is as shown in FIG. 5. First, a stand 22 for securing the inlay surface 20 is placed on the mold 12, the model 24 is placed thereon, and further thereon. A flexible sheet 26a is placed so as to cover the pad surface of the model 24, and a frame 28a is placed on the flexible sheet 26a so as to surround the table 22 (see FIG. 5A). The frame 28a is provided with a suction port 30, and the suction port 30 is connected to a vacuum pump (not shown). Next, sand 32 is put in the frame 28a (see FIG. 5B), and the flexible sheet 26b is put thereon (see FIG. 5C). Then, by operating the vacuum pump, air is sucked from the sand 32 filled in the frame 28a and sandwiched between the upper and lower flexible sheets 26a and 26b, and the sand 32 is solidified into the shape, that is, the sand 32 is hardened to the shape. Hold it as it is. After that, by removing the model 24 and the platform 22, as shown in FIG. 5D, a throwaway mold 34 having an inverted shape of the pad upper surface is obtained. The discarding mold 34 is a mold for producing a product-side sand mold 36 described below and is not used for casting the mold 12. Can be reused.
[0017]
(2-2) The product-surface-side sand mold making process is as shown in FIG. 6. First, the disposal mold 34 is turned over (see FIG. 6A), and the frame 28 b is placed thereon (FIG. 6 ( b)). Next, sand 32 is put in the frame 28b (see FIG. 6C), and the flexible sheet 26c is put thereon (see FIG. 6D). Then, air is sucked from the sand 32 filled in the frame 28b and sandwiched between the upper and lower flexible sheets 26a, 26c to solidify the sand 32 into the shape. Thereafter, the discarding mold 34 is dismantled by returning the inside from the vacuum state to the atmospheric pressure, and as shown in FIG. 6E, the product surface side sand mold 36 whose shape is maintained between the upper and lower flexible sheets 26a and 26c. Is obtained. The product side sand mold 36 has a shape obtained by inverting the concave portion of the disposal mold 34, that is, the same shape as the pad upper surface.
[0018]
(2-3) The back side sand mold production process is as shown in FIG. In this step, first, a sheet wax is attached to the upper surface of the pad of the model 24 and the side surface of the base 22 connected thereto to provide a surface layer 38 having a thickness corresponding to the thickness of the lower mold 14. Then, as shown in FIG. 7A, the flexible sheet 26d is placed on the model 24 having the surface layer 38, and the frame 28c is further placed thereon. In addition, one or a plurality of pouring ports 40 for pouring a molten metal material at the time of casting the lower mold 14 are provided. Next, sand 32 is put in the frame 28c (see FIG. 7B), and the flexible sheet 26e is put thereon (see FIG. 7C). Then, air is sucked from the sand 32 filled in the frame 28c and sandwiched between the upper and lower flexible sheets 26d and 26e to solidify the sand 32 into the shape. Thereafter, by removing the model 24 and the platform 22, a back side sand mold 42 having an inverted shape of the surface of the surface layer 38 is obtained as shown in FIG. 7D.
[0019]
The flexible sheets 26a to 26e, particularly the flexible sheets 26a and 26d used for the shape transfer surface, are made of a thermoplastic resin so as to adhere well to the complicated surface shape of the model 24 and the surface layer 38. It is preferable to use a thin sheet and cover it with the model 24 or the like after heating it.
[0020]
(3) The mold 12 is cast using the sand mold prepared as described above. In detail, as shown in FIG. 8, the product surface side sand mold 36 and the back side sand mold 42 are combined by inserting the convex part of the former 36 into the concave part of the latter 42, and the molten metal such as aluminum is melted. Is poured into the mold from the pouring port 40 and solidified. Thereby, the lower mold 14 is cast. Although not shown, the upper mold 16 is similarly manufactured by casting using a product-side sand mold and a back-side sand mold. The flexible sheets 26a and 26d are melted and disappear by the heat of the metal material at the portion where the molten metal flows.
[0021]
(4) Next, the cast lower mold 14 and the upper mold 16 are subjected to finishing treatment, (5) the contact surface 18 is subjected to electric discharge machining, and (6) further processing is performed to form the lower mold 14 and the upper mold 16. By assembling, the mold 12 is obtained.
[0022]
According to the method of manufacturing the mold according to the present embodiment, the flexible sheet 26a is formed between the surface of the model 24 and the sand 32 when a sand mold, specifically, a discard mold and a back sand mold are manufactured. , 26d do not directly contact the sand 32. Therefore, the number of surface treatment steps of the model 24 can be reduced. Further, since the sand 32 is solidified by vacuum suction and held in a predetermined shape, the process can proceed to the next step without waiting for a long curing time as in the case of curing with a resin. Further, since the sand mold is directly produced from the model 24, the man-hour for producing the resin mold can be reduced.
[0023]
As an example, a method according to the above-described embodiment (Example) and a method of curing a conventional sand mold with a resin (Comparative Example 1) in the case of manufacturing a foam molding die for an automobile seat cushion pad. And the conventional method of producing a vacuum suction sand mold shown in FIG. 9 (Comparative Example 2) to compare the construction period. The production flow of each method and the time (days) required for each step are shown in Table 1 below. In the example, the model NC processing was performed by the above-described high-speed NC processing, and in the comparative examples 1 and 2, normal NC processing was performed.
[0024]
[Table 1]

[0025]
As shown in Table 1, according to the present embodiment, it is possible to significantly reduce the time required for manufacturing a mold, shorten the number of development steps, and shorten the delivery time of a prototype, as compared with the conventional method. Can be planned.
[0026]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it can avoid that a model contacts a sand directly by using a flexible sheet for a shape transfer surface at the time of producing a sand type | mold, Therefore, the surface treatment man-hour of a model can be reduced. it can. Further, since the sand is held in a predetermined shape by vacuum suction, it is possible to proceed to the next step without waiting for the hardening time of the sand. As described above, the manufacturing period of the mold can be remarkably shortened as compared with the related art.
[Brief description of the drawings]
FIG. 1 is a perspective view of a seat cushion pad to be molded in one embodiment of the present invention.
FIG. 2 is a cross-sectional view at the time of foam molding of a mold manufactured in the same embodiment.
FIG. 3 is a flowchart showing steps of a mold manufacturing method according to the embodiment.
FIG. 4 is a flowchart of a process for producing a lower mold in the same embodiment.
5 (a) to 5 (d) are cross-sectional views in a process of manufacturing a disposal mold.
6 (a) to 6 (e) are cross-sectional views in a production step of a product side sand mold.
FIGS. 7A to 7D are cross-sectional views in a process of manufacturing a back side sand mold.
FIG. 8 is a sectional view of a casting mold for casting a lower mold.
FIG. 9 is a flowchart showing steps of a conventional mold manufacturing method.
[Explanation of symbols]
10 Seat cushion pad 12 Mold 24 Model 26a-e Flexible sheet 30 Suction port 32 Sand 34 Discard mold (first sand mold)
36: Sand type on product side (second sand type)
38: Surface layer 42: Back side sand mold (third sand mold)

Claims (2)

A step of producing a model of the foam molded article;
A step of preparing a sand mold as a mold from the obtained model, using a flexible sheet at least on the shape transfer surface, and hardening the sand by vacuum suction to produce a sand mold,
Casting a mold for foam molding using the obtained sand mold,
A method for producing a foaming mold including: The step of preparing the sand mold,
Producing a first sand mold having an inverted shape of one surface thereof from the model, wherein a sand is formed by vacuum suction with a flexible sheet interposed between the sand for the first sand mold and the model. Hardening process,
Producing a second sand mold having the same shape as the one surface of the model from the first sand mold, and hardening sand for the second sand mold by vacuum suction;
Providing a surface layer having a thickness corresponding to the thickness of the mold on the one surface of the model, and producing a third sand mold having an inverted shape of the surface layer from the model having the surface layer, (3) a step of interposing a flexible sheet between the sand for the sand mold and the surface layer to solidify the sand by vacuum suction;
The method for producing a mold for foam molding according to claim 1, comprising:

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