JPH0579415B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for easily manufacturing a mold using a low melting point alloy.

(Prior art) Conventionally, a simple manufacturing method is the dual-form method in which a punched sheet metal model is immersed in a molten low melting point alloy in a melting tank and solidified as it is to obtain a punch and die at the same time. ("Machines and Tools" June 1975, P21-25, Japanese Patent Publication No. 48-7576, etc.) Alternatively, as a modification of the dual form method, a sheet metal model without perforations is used, and the inner and outer surfaces of the sheet metal model are A method of simultaneously obtaining a punch and a die of different alloys by bringing them into contact with a molten metal of a low melting point alloy and solidifying the same (Japanese Patent Publication No. 15969/1983, No. 55733/1983, No. 95930/1983) Public notices, etc.) have already been established. According to these methods, it is possible to obtain the punch and die at the same time using a sheet metal model, compared to conventional general-purpose methods in which plaster and sand molds are sequentially transferred from the mother mold, manufactured, and cast into the sand mold. , productivity will improve significantly.

However, according to these methods, a high-precision sheet metal model must be prepared in order to guarantee the mold shape accuracy, and its production is extremely troublesome.
The problem was that it could not easily respond to complex design changes and lacked versatility.

Recently, efforts have been made to develop a method for easily manufacturing molds using a matrix made of a wooden mold, a resin model, etc., and a heat-resistant rubber sheet made of silicone rubber, fluorocarbon rubber, etc. −273544 publication,
This is disclosed in Japanese Patent Application Laid-open No. 18535/1983.
Here, this method will be explained with reference to FIGS. 3 and 4, which are taken from Japanese Patent Application Laid-Open No. 18535/1983. 2, first place the mother mold 8 in the punch casting frame 2, assemble both casting frames 1 and 2 together with the heat-resistant rubber sheet 7 in between, and then open the pouring port on the punch casting frame 2 side. 6 is connected to a vacuum pump (not shown), negative pressure is introduced into the punch casting frame 2, air is removed using the air vent hole 9 provided in the matrix 8, and the rubber sheet 7 is forcibly removed. is brought into close contact with the matrix 8 (Fig. 3). Then, while maintaining the state in which the rubber sheet 7 is in close contact with the matrix 8, the low melting point alloy molten metal M is poured into the die casting frame 1 through the pouring port 5, and then cooled and solidified to form the die D. Cast (1st
process).

Next, the substrate 3 on the punch casting frame 2 side is removed, the mother mold 8 inside is taken out, and the substrate 3 is reinstalled (FIG. 4). During this work, the pouring port 5 on the die casting frame 1 side
A vacuum pump (not shown) is used to apply a negative pressure to remove air from between the rubber sheet 7 and the die D to bring the rubber sheet 7 into close contact with the die D. Then, from the pouring port 6 The low melting point alloy molten metal M is poured into the punch casting frame 2, and is then cooled and solidified to cast the punch P (second step).

According to this method, the mold clearance can be easily secured by adjusting the thickness of the rubber sheet 7, and the problems in the above-mentioned dual form method using a sheet metal model and its modification method can be solved. Become.

(Problems to be Solved by the Invention) However, according to the simple manufacturing method using the rubber sheet 7, the thickness of the rubber sheet 7 tends to vary depending on the shape of the matrix 8.
There was a problem that it became difficult to guarantee mold clearance. To explain this using the model shown _in FIG _. , the strain ε on the left and right sides of the microsection S
It is proportional to the difference Δε. On the other hand, this strain difference Δε is expressed by μ, the coefficient of friction between the rubber sheet 7 and the matrix 5, E, the Young's modulus of the rubber sheet 7, Pv, the negative pressure suction force from the air vent hole 9, Assuming that the thickness is t and the sum of strains acting perpendicularly to the bottom surface of the minute cross section S is {Σεi(a)+Σεj(b)}, it is given by the following formula.

Δε=μ・Pv・ΔI/E・t +μ{Σεi(a)+Σεj(b)} In other words, the difference in strain Δε is the difference between the rubber sheet 7 and the matrix 8.
Therefore, in order to make the thickness of the rubber sheet 7 uniform, it is necessary to reduce this friction coefficient μ. However, conventionally, no measures have been taken to proactively reduce this friction coefficient μ, especially when it comes to the matrix 8.
If the mold has a complicated shape, or if the mother mold 8 is made of a wooden mold, it becomes difficult to guarantee mold clearance, and there is a risk that the mold may become unusable.

The present invention was made to solve the above problem, and it is possible to eliminate variations in the thickness of the rubber sheet that is brought into close contact with the mother mold, and to stably obtain a mold with excellent precision. The purpose is to provide a simple manufacturing method that can be used.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention brings a heat-resistant rubber sheet into close contact with a mother mold, and brings the mother mold into contact with a molten low-melting alloy in a casting frame. First, one of the paired molds is cooled and cast, and then, using one of the molds as a new mother mold, it is brought into contact with the molten low melting point alloy in the other casting frame, and then cooled as it is. In the simple mold manufacturing method of casting the other of a pair of molds, a substance having a low coefficient of friction is applied in advance to at least one of the surface of the mother mold and the surface of the rubber sheet that are in close contact with each other. It is characterized by having been configured.

In the present invention, the substance having a low coefficient of friction is the melting temperature of a low melting point alloy (50 to 300°C).
There are no particular limitations on the type of material as long as it does not change in quality, and for example, molybdenum disulfide (MoS ₂ ), boron nitride (BN), graphite (C), etc. can be selected. Further, the method of applying the substance having a low coefficient of friction is also arbitrary, and various methods such as brushing, spraying, dipping, etc. can be employed.

Further, in the invention, the substance having a low coefficient of friction may be applied directly to the surface of the matrix, but when a wooden mold is used as the matrix, the surface of the wooden mold may be coated with heat resistance in advance. It is desirable to reduce the surface roughness of the matrix by coating or impregnating it with a paint, such as silicone resin or fluorine resin.

(Function) In the simple manufacturing method configured as described above, a substance with a low coefficient of friction is applied to the surface of the mother mold or the rubber sheet, so that when the rubber sheet is brought into close contact with the mother mold, the rubber sheet expands and contracts. becomes smooth and sticks to the matrix with a nearly constant thickness.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings. Note that this example is based on the above-mentioned figures 3 and 4.
Since the basic process is the same as the simple manufacturing method explained based on the figures, only the main parts are shown here, and the same parts as shown in Figs. 3 and 4 are given the same reference numerals. , and duplicate explanations will be omitted.

1 and 2 show the first step according to the present invention to obtain a die (D). In this first step, a wooden mold is used as the mother mold 8, silicone resin is applied to the product shape surface by spraying in advance, and the silicone resin is sufficiently permeated to coat the surface layer of the mother mold 8 with silicone resin. An impregnated layer 11 is formed. Next, molybdenum disulfide (MoS ₂ ) is sprayed onto the product-shaped surface of the matrix 8 to form a molybdenum disulfide film 12 on the product-shaped surface.
At this time, it is desirable to rub the coating 12 slightly after applying the molybdenum disulfide to improve slippage.

Next, the mother mold 8 prepared as described above is set in the punch casting frame 2, a heat-resistant rubber sheet (silicon rubber) 7 is set on top of it, and the die casting frame 2 is set.
After integrating, negative pressure is supplied to the punch casting frame 2. By supplying this negative pressure, the air between the product-shaped surface of the mother mold 8 and the rubber sheet 7 is discharged to the outside through the air vent hole 9, and the rubber sheet 7 is brought into close contact with the mother mold 8. At this time, the molybdenum disulfide film 12
Since the frictional resistance between the rubber sheet 7 and the matrix 8 is reduced due to the presence of It will stick to the top with a constant thickness that corresponds to the thickness of the pressed product. By the way,
The coefficient of friction μ between the rubber sheet 7 and the matrix 8 is 0.2 when a film 12 of molybdenum disulfide is formed as in this embodiment, whereas it is 0.2 when no film is formed as in the conventional case. In this case, it is 0.9, and such a large difference in the friction coefficient μ contributes to eliminating the strain difference (Δε). Furthermore, in this example, since the silicone resin impregnated layer 11 was formed under the molybdenum disulfide film 12, the mother mold 8
The surface roughness of the rubber sheet 7 is reduced as much as possible.
will expand and contract more smoothly, and its thickness will become more uniform.

Therefore, if the low melting point alloy molten metal M is then poured into the die casting frame 1 and brought into contact with the mother mold 8, and then cooled and solidified, a die D with good precision can be obtained, and then the die Negative pressure is supplied into the casting frame 1 to remove the mother die 8 while keeping the rubber sheet 7 stuck to the die D, and then punch the low melting point alloy molten metal M in the manner described in FIG. 4 above. Pour the metal into the casting frame 2,
By casting a punch, a mold with excellent mold clearance can be obtained. However, the matrix 8
When demolding, the presence of the molybdenum disulfide film 12 allows the matrix 8 to be easily separated from the rubber sheet 7, thereby preventing damage to the rubber sheet 7 and making it possible to use it repeatedly.

It should be noted that the present invention is of course not limited to the embodiments described above, and for example,
It can also be applied to a method of producing a simple mold by placing a mother mold in a pair of upper and lower casting frames, as shown in Japanese Patent No. 273544.

(Effects of the Invention) As explained above in detail, according to the mold manufacturing method according to the present invention, the presence of a substance having a low coefficient of friction allows the rubber sheet to expand and contract smoothly,
It sticks almost uniformly to the mother mold and has the effect of ensuring mold clearance. Further, by reducing the friction between the mother mold and the rubber sheet, the mother mold can be easily removed from the mold after casting, and this has the effect of preventing damage to the rubber sheet during demolding.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of manufacturing a simple type according to the present invention, Fig. 2 is an enlarged sectional view of section A in Fig. 1, and Figs. 3 and 4 are a sectional view of a conventional simple type. FIGS. 5a and 5b are cross-sectional views showing an example of the manufacture of the rubber sheet. FIGS. 1...Die molding frame, 2...Punch casting frame, 7...
... Rubber sheet, 8 ... Matrix, 11 ... Impregnated layer, 1
2...Low friction material film, M...Low melting point alloy molten metal.

Claims (1)

[Claims] 1. A heat-resistant rubber sheet is closely attached to the mother mold, and the mother mold is brought into contact with the molten low-melting point alloy in the casting frame, cooled as it is, and one of the paired molds is cast. With one as a new mother type,
In a simple mold manufacturing method in which the mold is brought into contact with a low melting point alloy molten metal in another casting frame and cooled as it is to cast the other mold of the pair, the surfaces of the mother mold and the mold that are in close contact with each other are A simple manufacturing method characterized in that a substance having a low coefficient of friction is applied in advance to at least one surface of a rubber sheet.