JPS62101346A - Vacuum mold molding method - Google Patents

Abstract

PURPOSE:To solve problems including the short life of a wooden pattern, the harmfulness and difficulty in coating, of a resin liquid and the danger of ignition by using a UV-curing resin to constitute a film constituting the surface of a casting mold. CONSTITUTION:The liquid of the UV-curing resin is coated atop a pattern board and thereafter UV rays are irradiated to the liquid of the UV-curing resin to cure the resin liquid. A molding flask is imposed on such pattern board and sand is packed into the molding flask. A shielding member is put atop the molding flask and the inside of the molding flask is evacuated to solidify the sand. The molding flask holding the solidified sand is separated from the above-mentioned pattern board while the above-mentioned UV-curing resin is held attracted to the heat resistant granular material side. Heating is not required at all in the stage of curing the resin liquid according to the above- mentioned method and therefore, the shortage of the life of the wooden pattern, as with the conventional practice is obviated. The UV-curing resin is a harmless material, is not high in viscosity, permits easy coating onto the pattern board and is a non-inflammable material.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a casting flask that contains heat-resistant particulate matter such as sand (hereinafter referred to as sand) and is sealed with a resin film. This section deals with the so-called vacuum molding method, which involves solidifying sand and creating molds.

(Prior art) In general, the vacuum mold manufacturing method involves adsorbing a sheet-like resin film onto the upper surface of a model plate, placing a casting flask on the model plate, and filling the flask with sand. The same (sheet-shaped resin film) is placed on the top of the casting flask, the pressure inside the flask is reduced and the sand is solidified by atmospheric pressure, and then the adsorption state of the resin film to the model board is released and the mold is cut out. However, if the height of the model on the model board is too high (or if it is difficult to completely adsorb the resin film to the top surface of the model board, apply resin liquid to the top surface of the model board. A method has been proposed in which a resin film as described above is formed by curing. Conventionally, there are the following methods for forming this resin film.The first method is to cure resin powder. This is a method in which a dispersion obtained by mixing an organic solvent or an organic solvent and water is applied to the upper surface of a model plate coated with a release agent in advance, and then heated to form a film. The third method is to heat a thermoplastic resin to a liquid state, apply it to the top surface of the model board, and then harden it to form a film.The third method uses paraffin, which has a relatively low melting point of 60 to 120"C. This is a method in which a mixture of wax and thermoplastic resin is applied to the top of the model board and then heated to form a film.However, in both of these conventional methods, the model board is heated, so the model board is not made of wood. In the case of molds, the life of the model board is shortened due to early cracking, and in addition, organic solvents are harmful in the first method, and organic solvents are harmful in the second method.
In method 1, the resin liquefied by heating has a high viscosity, so it is not easy to apply, and in method 3, there are problems such as the possibility of causing a fire if the heating temperature is incorrectly adjusted. there were.

(Object of the Invention) The present invention has been made with the aim of solving the above problems.

(Means for solving the problem) The vacuum mold manufacturing method of this company applies an ultraviolet curable resin liquid to the upper surface of the model plate, and then irradiates the ultraviolet curable resin liquid with ultraviolet rays to make the ultraviolet curable resin. The resin liquid is reacted and cured, and a casting flask is placed on a model plate coated with the cured ultraviolet curable resin, and the flask is filled with sand, and a shield is placed on the top surface of the sand-filled flask. Covering the mold with a member, the inside of the flask is depressurized to solidify the sand, and then the mold holding the solidified sand is separated from the model plate while adsorbing the ultraviolet curable resin to the heat-resistant particulate material side. It is characterized by: To explain in more detail, first, an ultraviolet curable resin liquid is applied to the upper surface of the model plate to a thickness of 50 to 200 μm by spray or brush. Here, the ultraviolet curable resin refers to a resin that undergoes a curing reaction upon irradiation with ultraviolet rays, and includes unsaturated polyester, epoxy, urethane, polyester, alkyd, silicon, spiroacetal, and the like. Note that the speed of curing of the resin can be adjusted by increasing or decreasing the amount of the sensitizer and additives added. Next, the ultraviolet curable resin liquid applied to the model board is irradiated with ultraviolet rays for several seconds from a position a predetermined distance away from an ultraviolet lamp to react and cure the ultraviolet curable resin liquid to form a film.

Next, a casting flask equipped with a suction-like structure is placed on the model plate to which the film-formed ultraviolet curable resin is adhered, and the flask is filled with sand. The upper opening of the flask is closed by covering the upper surface with an air-impermeable and flexible closing member. Next, the inside of the flask is depressurized by suction, and atmospheric pressure is applied from the outside of the shielding member to solidify the sand in the flask.Then, the flask holding the solidified sand is raised to expose a film of ultraviolet rays. While adsorbing the hardening resin to the sand side,
Separate from the model plate. A predetermined mold is thereby obtained.

Note that if the coating thickness of the ultraviolet curable resin is less than 50 μm, it will easily break when peeled from the wooden mold, and if it exceeds 200 μm, defects will often occur inside the film-formed resin.

〔Example〕

The wooden mold shown in the figure is used as a model board, wax is applied as a mold release agent to the upper surface of the wooden mold, and then diarylidene pentaerythritol in the spiroacetal system is used as an ultraviolet curable resin liquid as the main raw material. Spray UV curable resin to a thickness of about 100μ. Next, a high-pressure mercury lamp of 2 kW (8Q w /l) was used as an ultraviolet lamp.
yn), while rotating the wooden mold coated with UV-curable resin horizontally, irradiate UV rays for 3 seconds from a position of 15 crn above the wooden mold and a position of 13 cn1 diagonally above the wooden mold to react the UV-curable resin. Let it harden. Then, U
A flask is placed on a wooden mold in which the V-cured resin has been cured, and after filling the flask with sand, the upper opening of the flask is closed with a resin film, and then the inside of the flask is depressurized by suction. The sand is solidified, and then the flask is separated from the wooden mold and lifted up. At this time, the cured UV cured resin film was adsorbed to the sand side and separated from the wooden mold. The casting obtained by pouring the metal into the mold thus produced had the desired properties.

(Effects of the Invention) As is clear from the above description, the present invention uses an ultraviolet curable resin for the film constituting the mold surface in the vacuum mold making method. is completely unnecessary, and therefore the life of the wooden mold will not be shortened as in the conventional method. In addition, the ultraviolet curable resin liquid is a harmless substance and does not have a high viscosity and can be adjusted to an appropriate viscosity by diluting it, so it can be easily applied to a model board. Moreover, since the ultraviolet curable resin is a non-flammable material, it is easy to store and there is no risk of fire.

In addition, the curing time of the ultraviolet curable resin liquid is 2 hours after irradiation with ultraviolet rays.
, 3 seconds, which has excellent effects such as greatly shortening the molding time.

[Brief explanation of drawings]

The drawing shows a wooden mold used when implementing the present invention.

Claims (1)

[Claims] After applying an ultraviolet curable resin liquid to the upper surface of the model board, the ultraviolet curable resin liquid is irradiated with ultraviolet rays to react and cure the ultraviolet curable resin liquid, and the model plate coated with the cured ultraviolet curable resin is A flask is placed on top of the flask, the flask is filled with heat-resistant particulate matter, a shielding member is placed over the top of the flask filled with the heat-resistant particulate matter, and the inside of the flask is depressurized. The method is characterized by solidifying the heat-resistant particulate matter, and then separating the casting flask holding the solidified heat-resistant particulate matter from the model plate while adsorbing the ultraviolet curable resin to the heat-resistant particulate matter side. A vacuum mold manufacturing method.