JPS61150744A - Vacuum molding method - Google Patents

Abstract

PURPOSE:To prevent the mold collapsion arising from the decrease in the degree of vacuum by setting a pattern attracted with a film to a flask, packing molding sand into the flask, covering the top surface with a film and evacuating the inside of the flask then removing the film from the top surface in the projecting part of the pattern, providing a sleeve and building up additionally the molding sand into the flask thereby forming a casting mold. CONSTITUTION:The molding sand 4 is packed into the flask set with the pattern 1 having the projecting part 3 and having the film attracted thereto until the sand arrives at the top surface 3a in the projecting part 3 of the pattern 1. The top surface of the molding sand 4 and the top surface 3a in the projecting part 3 of the pattern 1 are coated with the film and the inside of the hermetic space formed of the molding flask and the film is evacuated. The film on the top surface 3a of the projecting part 3 of the pattern 1 is then partially removed and the sleeve 5 is provided so as to enclose the surface 3a. The sand 7 is added and built up so as to embed the sleeve 5 while an aperture 6 of the sleeve 5 is held open. The casting mold is thus formed.

Description

【発明の詳細な説明】 産業上の利用分野 この発明は、鋳枠とフィルムとにより鋳物砂を密閉し、
その密閉部内を減圧することによって鋳型を形成する減
圧造型法に関するものである。[Detailed description of the invention] Industrial field of application This invention seals molding sand with a casting flask and a film,
The present invention relates to a vacuum molding method in which a mold is formed by reducing the pressure inside the sealed portion.

従来の技術 従来から、粘結剤を含まない乾燥ケイ砂を用い、鋳枠お
よびプラスチックフィルムで密閉され、かつ内部が減圧
された鋳型を用いる減圧造型鋳造法が行なわれている。BACKGROUND OF THE INVENTION Conventionally, vacuum mold casting has been carried out using dry silica sand containing no binder, using a flask and a mold sealed with a plastic film and having a reduced pressure inside.

鋳型内の減圧された乾燥ケイ砂には、ブスチックフィル
ムを介して大気圧が加えられ、その差圧によって鋳型は
成形され保持される。Atmospheric pressure is applied to the depressurized dry silica sand in the mold through a plastic film, and the mold is shaped and held by the differential pressure.

発明が解決しようとする問題点 しかし、以上の従来の減圧造型法には次のような問題が
あった。Problems to be Solved by the Invention However, the conventional vacuum molding method described above has the following problems.

以上の減圧造型法によって得られた鋳型に注涌すると、
溶湯の熱でフィルムが焼失する。。そのため、鋳込みの
過程で鋳型自体の減圧度が低下してしまい、型の保持が
困難になる場合がある。特に、例えば鍋のように凹部を
有する形状のものでは、その凹部の内側を型取る部分の
鋳型の減圧は、外側を型取る部分の鋳型との間の狭い径
路を介して行なわれ、そのため外側に比較し内側部分の
減圧を効率良く行なうのが困難であり、前述したように
注湯時にフィルムが焼失した場合に型くずれが生じてし
まうという問題があった。When poured into the mold obtained by the above vacuum molding method,
The film is burned away by the heat of the molten metal. . Therefore, the degree of vacuum in the mold itself decreases during the casting process, which may make it difficult to hold the mold. In particular, for objects with a recessed part, such as a pot, the depressurization of the mold in the part that molds the inside of the recess is carried out through a narrow path between it and the mold in the part that molds the outside. Compared to this, it is difficult to efficiently reduce the pressure in the inner part, and as mentioned above, there is a problem in that if the film is burnt out during pouring, the shape will collapse.

そこで、減圧度が低下しても型くずれがしないようにす
るために、粘結性の砂を用いる手段も考えられる。しか
しその場合、通常の鋳物砂に異質の砂を混入させること
になって、鋳物砂の特性が全体として劣化するという問
題があった。Therefore, in order to prevent the mold from losing its shape even if the degree of vacuum decreases, it is also possible to use cohesive sand. However, in that case, there is a problem in that the characteristics of the foundry sand as a whole are deteriorated because a different type of sand is mixed into the normal foundry sand.

この発明は、以上の従来の事情に鑑みてなされたもので
あって、鋳型内に注湯してフィルムが焼失しても、減圧
度の低下に起因する型くずれが生じるようなことのない
減圧造型法を提供することを目的とする。This invention has been made in view of the above-mentioned conventional circumstances, and is a vacuum molding method that does not cause mold deformation due to a decrease in the degree of vacuum even if the film is burnt out after pouring into the mold. The purpose is to provide law.

問題点を解決するための手段 すなわちこの発明の減圧造型法は、フィルムを模型面に
吸着させてフィルム成形し、そのフィルムを吸着した模
型に枠をセットし、そ。後枠内。A means for solving the problem, that is, the vacuum molding method of the present invention, is to form a film by adsorbing a film onto a model surface, and setting a frame on the model to which the film is adsorbed. Inside the rear frame.

鋳物砂を入れてその鋳物砂上面をフィルムによって被覆
して鋳枠とフィルムとによって鋳物砂を密閉し、その密
閉部内を減圧することによって鋳型を形成する減圧造型
法において、フィルムを吸着した模型にセットされた枠
内に模型の凸部上面に達する位置まで鋳物砂を充填し、
その鋳物砂上面および模型の凸部上面をフィルムで被覆
して鋳枠とフィルムとにより形成された密閉部内を減圧
し、次に模型の凸部上面を被覆するフィルムを部分的に
除去し、そのフィルムを除去した模型上面を取り囲むよ
うにしてスリーブを設け、そのスリーブの開口部を開放
した状態でそのスリーブを埋設するようにさらに鋳物砂
を追加して嵩上げして鋳型を形成することを特徴とする
ものである。In the vacuum molding method, a mold is formed by filling molding sand, covering the upper surface of the molding sand with a film, sealing the molding sand between the molding flask and the film, and reducing the pressure inside the sealed part. Fill the set frame with molding sand until it reaches the top of the convex part of the model,
The upper surface of the molding sand and the upper surface of the convex part of the model are covered with a film to reduce the pressure in the sealed area formed by the flask and the film, and then the film covering the upper surface of the convex part of the model is partially removed. A sleeve is provided to surround the top surface of the model from which the film has been removed, and molding sand is further added to bury the sleeve in an open state to form a mold. It is something to do.

発明の詳細な説明 次にこの発明を第１図〜第３図を参照して更に具体的に
説明する。DETAILED DESCRIPTION OF THE INVENTION Next, the present invention will be described in more detail with reference to FIGS. 1 to 3.

第１図に示す模型１は、主型２上面に凸部３を有してな
る。この発明では先ず、そのように凸部３を有する模型
１にフィルムを吸着させてセットした枠内に第２図およ
び第３図に示すように模型１の凸部３上面３ａに達する
位置まで鋳物砂４を充填する。A model 1 shown in FIG. 1 has a convex portion 3 on the upper surface of a main mold 2. In this invention, first, a film is adsorbed onto the model 1 having the convex portion 3, and the casting is placed within the set frame to a position reaching the upper surface 3a of the convex portion 3 of the model 1, as shown in FIGS. 2 and 3. Fill with sand 4.

次にこの発明では、枠内に充填された鋳物砂４上面およ
び模型１の凸部３上面３ａをフィルムで被覆して鋳枠と
フィルムとにより形成された密閉部内を減圧する。その
ようにすることによって、鋳枠とフィルムとにより形成
された密閉部内の鋳物砂４は、模型１を形成る一定の形
態に保持される。Next, in this invention, the upper surface of the molding sand 4 filled in the flask and the upper surface 3a of the convex part 3 of the model 1 are covered with a film, and the pressure inside the sealed part formed by the flask and the film is reduced. By doing so, the molding sand 4 within the seal formed by the flask and the film is held in a constant form forming the model 1.

次いでこの発明では、図に示すように模型１の凸部３上
面３ａを被覆するフィルムを部分的に除去し、そのフィ
ルムを除去した模型１凸部３上面３ａを取り囲むように
してスリーブ５を設ける。Next, in this invention, as shown in the figure, the film covering the upper surface 3a of the convex part 3 of the model 1 is partially removed, and the sleeve 5 is provided so as to surround the upper surface 3a of the convex part 3 of the model 1 from which the film has been removed. .

模型１の凸部３上面３ａを被覆するフィルムの部分的除
去は鋳物砂４の密閉状態を妨げないＬｌ様で、模型１の
凸部３上面３ａに限って行なう。また、スリーブ５とし
ては薄肉耐火性スリーブや耐火性パイプ等を用いること
ができる。Partial removal of the film covering the upper surface 3a of the convex portion 3 of the model 1 is carried out only on the upper surface 3a of the convex portion 3 of the model 1 in a way that does not disturb the sealed state of the molding sand 4. Further, as the sleeve 5, a thin fireproof sleeve, a fireproof pipe, or the like can be used.

次にこの発明では、以上のようにして設けたスリーブ５
の開口部６を開放した状態でそのスリーブ５を埋設する
ようにさらに鋳物砂７を追加して嵩上げして鋳型を形成
する。それによってスリーブ５が固定され、スリーブ５
は鋳型内外間の通気孔として機能する。Next, in this invention, the sleeve 5 provided as described above
With the opening 6 of the sleeve 5 open, molding sand 7 is further added to bury the sleeve 5 and raise the volume to form a mold. The sleeve 5 is thereby fixed, and the sleeve 5
functions as a ventilation hole between the inside and outside of the mold.

したがって、以上のこの発明の減圧造型法によって得ら
れた鋳型によれば、次のようにして鋳造が行なわれる。Therefore, according to the mold obtained by the above-mentioned vacuum molding method of the present invention, casting is performed in the following manner.

すなわち、模型１を取り外して得られた上型８に下型９
を組み合わせて得られた鋳型に、湯口１０から溶湯を注
入すると、溶湯は上型８の下側より徐々に押し上げられ
、その溶湯の熱により鋳型のフィルムは焼失してしまう
。したがって、仮にスリーブ５が存在せず、通気孔がな
い場合は、フィルムの焼失によって鋳物砂４の部分と＃
Ｉ型内部との差圧はなくなり、鋳物砂４の部分の減圧状
態が悪化し、凸部３周辺の鋳物砂が保持できなくなり、
型くずれが生じてしまう。しかし、この発明の方法によ
って得られた鋳型の場合、スリーブ５が存在するためフ
ィルムの有無にかかわらず、鋳型内部は大気圧に保たれ
、一方鋳物砂４の部分は絶えず減圧されているため、フ
ィルム焼失後も鋳物砂４の部分と鋳型内側との圧力差は
ある程度保たれる。その結果、少なくとも溶湯注入の過
程では型くずれが生じるようなことはなく、当初予定さ
れた鋳造品を得ることができる。That is, the lower mold 9 is attached to the upper mold 8 obtained by removing the model 1.
When molten metal is injected from the sprue 10 into the mold obtained by combining the above, the molten metal is gradually pushed up from the lower side of the upper mold 8, and the film of the mold is burned away by the heat of the molten metal. Therefore, if the sleeve 5 does not exist and there is no ventilation hole, the part of the molding sand 4 and #
The differential pressure with the inside of the mold I disappears, the depressurized state of the molding sand 4 part worsens, and the molding sand around the convex part 3 cannot be held.
This will cause the product to lose its shape. However, in the case of the mold obtained by the method of the present invention, the interior of the mold is maintained at atmospheric pressure regardless of the presence or absence of the film due to the presence of the sleeve 5, while the pressure in the molding sand 4 area is constantly reduced. Even after the film is burned out, the pressure difference between the molding sand 4 and the inside of the mold is maintained to some extent. As a result, mold deformation does not occur at least during the process of pouring the molten metal, and the originally planned cast product can be obtained.

実施例 以下にこの発明の実施例を記す。Example Examples of this invention are described below.

実施例 第３図に示す形状の模型１で、寸法が内径８５φ、肉厚
１０ｍｇ＋、外径１０５φ、高さ８５Ｉｆｆｉの凹状の
主型２に１２０Ｘ１２０ｘ１０ｍｍの７ランジが付き、
かつ主型２の上面の２カ所に肉１１１１０ｍｍ。Example A model 1 having the shape shown in FIG. 3 has a concave main mold 2 with dimensions of an inner diameter of 85 φ, a wall thickness of 10 mg +, an outer diameter of 105 φ, and a height of 85 Iffi, with 7 lunges of 120 x 120 x 10 mm,
And 11110mm of meat in two places on the top surface of main mold 2.

幅４０１１高ざ２０ｍｇ＋の凸部３が突き出た形状の模
型１を用い、全体゛をフィルムで被覆した。その模型１
を用いて上型、下型を減圧造型し、鋳型を一体に型合せ
した後、凸部３上面３ａのフィルムを凸部３の肉厚形状
に沿って除去した。そのフィルムを除去した部分の上に
、高さ４０■−の嵩上げ用薄肉耐火性スリーブを載置し
た。嵩上げ用薄肉耐火性スリーブはＶ−７硅砂に水ガラ
スを７％混合したＣＯ２プロセスによって鋳造して得た
。次にスリーブの高さまで鋳物砂（Ｖ−７硅砂）で嵩上
げ造型した。その後、鋳型内に１５５０℃の溶湯を注入
した。− その結果得られた鋳造品を調べたところ、型くずれ等の
欠陥は全く見られず、寸法精度も良く、鋳肌の良い鋳造
品であった。A model 1 having a protruding convex portion 3 with a width of 401 mm and a height of 20 mg+ was used, and the entire body was covered with a film. The model 1
The upper mold and the lower mold were molded under reduced pressure using a mold, and after the molds were molded together, the film on the upper surface 3a of the protrusion 3 was removed along the thick shape of the protrusion 3. A thin-walled fireproof sleeve with a height of 40 cm was placed on the part from which the film had been removed. A thin-walled refractory sleeve for bulking was obtained by casting by a CO2 process using a mixture of V-7 silica sand and 7% water glass. Next, the sleeve was raised to the height of the sleeve using molding sand (V-7 silica sand). Thereafter, molten metal at 1550°C was poured into the mold. - When the resulting cast product was examined, no defects such as deformation were observed, and the cast product had good dimensional accuracy and a good casting surface.

比較例 周知の減圧造型法によって、実施例と同一形状のものを
鋳造した。その結果得られた鋳造品を第４図に示す。図
に示すように、凸部が形成されるべき部分に型くずれが
発生している。これは鋳型内の溶湯上昇時におけるフィ
ルムの燃焼によって減圧状態が悪化し、鋳型の凸部周辺
の形状保持が困難になったものと考えられる。Comparative Example A product having the same shape as the example was cast by a well-known vacuum molding method. The resulting cast product is shown in FIG. As shown in the figure, deformation occurs in the portion where the convex portion should be formed. This is thought to be because the reduced pressure condition deteriorated due to burning of the film as the molten metal rose in the mold, making it difficult to maintain the shape around the convex portions of the mold.

発明の効果 以上のようにこの発明の減圧造型法によれば、フィルム
を吸着して枠内にセットされた模型の凸部上面および鋳
物砂上面をフィルムで被覆して形成された密閉部内を減
圧し、模型の凸部上面を被覆するフィルムを除去した部
分にスリーブを設けてそのスリーブを外部に開放した状
態でそのスリーブを埋設するようにさらに鋳物砂を追加
高上げして鋳型を形成するようにしたことによって、凹
凸のある？！雑な形状の鋳型を造型し鋳造する場合でも
、型くずれがなく、寸法精度が良く、鋳肌の美麗な鋳造
品を得・ることかできる。しかも、そのために鋳物砂に
粘結剤を混入させる必要はなく、鋳物砂の特性を劣化さ
せることなく維持することができること、および製品の
不良率が低下することもあわせて、大幅なコスト低減を
図ることができるという優れた効果が奏される。Effects of the Invention As described above, according to the vacuum molding method of the present invention, the pressure is reduced in the sealed area formed by adsorbing the film and covering the upper surface of the convex part of the model set in the frame and the upper surface of the molding sand with the film. Then, a sleeve is provided in the part where the film covering the upper surface of the convex part of the model has been removed, and with the sleeve open to the outside, molding sand is added and raised to form a mold so as to bury the sleeve. Are there any bumps caused by it? ! Even when molding and casting a mold with a rough shape, it is possible to obtain a cast product that does not lose its shape, has good dimensional accuracy, and has a beautiful casting surface. Moreover, there is no need to mix a binder into the foundry sand, and the properties of the foundry sand can be maintained without deterioration, and the defect rate of products is reduced, resulting in significant cost reductions. The excellent effect of being able to achieve this is achieved.

【図面の簡単な説明】[Brief explanation of drawings]

第１図はこの発明の減圧造型法の実施に供する模型の一
例を示す斜視図、第２図は第１図の模型を所定の枠内に
セットして鋳物砂を充填した状態を示す部分断面図、第
３図は第２図■−■断面図、第４図は第１図の模型を用
いて従来の減圧造型鋳造法を行なった場合に得られる鋳
造品の斜視図である。 １・・・模型、　２・・・主型、　３・・・凸部、　４
．７・・・鋳物砂、　５・・・スリーブ。Fig. 1 is a perspective view showing an example of a model used for carrying out the reduced pressure molding method of the present invention, and Fig. 2 is a partial cross section showing the model shown in Fig. 1 set in a predetermined frame and filled with molding sand. Figures 3 and 3 are sectional views taken along line 2--2 in Figure 2, and Figure 4 is a perspective view of a cast product obtained when the conventional vacuum mold casting method is carried out using the model shown in Figure 1. 1... Model, 2... Main mold, 3... Convex part, 4
．． 7... Foundry sand, 5... Sleeve.

Claims (1)

【特許請求の範囲】[Claims] フィルムを模型面に吸着させてフィルム成形し、そのフ
ィルムを吸着した模型に枠をセットし、その後枠内に鋳
物砂を入れてその鋳物砂上面をフィルムによって被覆し
て鋳枠とフィルムとによって鋳物砂を密閉し、その密閉
部内を減圧することによって鋳型を形成する減圧造型法
において、フィルムを吸着した模型にセットされた枠内
に模型の凸部上面に達する位置まで鋳物砂を充填し、そ
の鋳物砂上面および模型の凸部上面をフィルムで被覆し
て鋳枠とフィルムとにより形成された密閉部内を減圧し
、次に模型の凸部上面を被覆するフィルムを部分的に除
去し、そのフィルムを除去した模型上面を取り囲むよう
にしてスリーブを設け、そのスリーブの開口部を開放し
た状態でそのスリーブを埋設するようにさらに鋳物砂を
追加して嵩上げして鋳型を形成することを特徴とする減
圧造型法。A film is adsorbed onto the model surface to form a film, a frame is set on the model to which the film is adsorbed, and then molding sand is placed in the frame and the upper surface of the molding sand is covered with the film, and the mold is formed using the flask and film. In the vacuum molding method, which forms a mold by sealing sand and reducing the pressure inside the sealed part, molding sand is filled into a frame set on a model with a film adsorbed to the top of the convex part of the model. The upper surface of the molding sand and the upper surface of the convex part of the model are covered with a film, the pressure inside the sealed area formed by the casting flask and the film is reduced, and then the film covering the upper surface of the convex part of the model is partially removed. A sleeve is provided to surround the upper surface of the model from which the mold has been removed, and molding sand is further added to bury the sleeve in an open state to form a mold. Decompression molding method.