JPH01181958A - Mold for differential pressure casting and method for molding thereof - Google Patents

Abstract

PURPOSE:To restrain the development of casting blow hole and to produce high quality casting by making permeability of a molding material at least in the neighborhood of cavity larger than that at the other part. CONSTITUTION:The mold 4 having a sprue 41, runner 42 and casting cavity 43 under mutually communicating condition is set in a casting chamber for differential pressure casting apparatus. Then, the casting material 13 melted with the are generating device is poured into the sprue 41 in the mold 4 from a crucible and immediately, by operating an inert gas supplying means and sucking means, the difference between inner pressures of a melting chamber and the casting chamber is formed. By this different pressure, the molten casting material in the sprue 41 is flowed into the casting cavity 43 through the runner 42, to serve as a feeder. Then, as the permeability C1 at least in the neighborhood of the casting cavity 43 is made to large than the permeability C2 at the other part, the pressure Pa in the casting cavity 43 is rapidly balanced almost with the inner pressure in the casting chamber and the pressure Pb becomes smaller than the pressure Pa near the sprue 41 and the difference P1 of both pressure is equalized to setting inner pressure difference between the melting chamber and the casting chamber. Therefore, the molten material 13 is quickly cast into the casting cavity 43 and the casting having closely high quality without casting blow hole is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a new differential pressure casting mold for precision casting of dental prostheses, Imblanc I, decorative accessories, etc., and an effective molding method thereof. It is something.

(Prior Art) For example, a differential pressure casting apparatus is used as one of the methods for molding the above-mentioned precision cast product. The outline of the differential pressure casting apparatus will be explained with reference to FIG. 5, which is an embodiment of the present invention. In the figure, 1 is a melting chamber, 2 is a casting chamber, and both chambers 1.2 are connected to a partition wall 3.
A through hole 31 is formed approximately in the center of the partition wall 3. The melting chamber 1 is equipped with an arc generator 11, a melting crucible 12, etc., and a mold 4 made of a breathable material is placed on a mold holding table 40 in the casting chamber 2. The upper sprue 41 is placed so as to match the through hole 31. Furthermore, an inert gas supply means 5 is connected to the melting chamber 1, and a suction means 6 is connected to the casting chamber 2, respectively.

In order to perform casting with such a casting device, the first crucible 12 is
The casting material 13 contained therein is heated and melted by the arc generating device 11, and the molten casting material 13 is poured into the sprue 41 of the mold 4 by tilting the crucible 12 or the like. Next, the inert gas supply means 5 and the suction means 6 are operated to increase the internal pressure of the melting chamber 1 in order to create a difference between the internal pressures of the melting chamber 1 and the casting chamber 2), and by utilizing this internal pressure difference. Molten casting material 1 in sprue 41
The molten casting material is poured into the casting cavity 43 through the runner 42. The application of the above differential pressure is
The internal pressure of melting chamber 1 is above atmospheric pressure and the internal pressure of casting chamber 2 is atmospheric pressure, the internal pressure of melting chamber 1 is above atmospheric pressure and the internal pressure of casting chamber 2 is below atmospheric pressure, or the internal pressure of melting chamber 1 is atmospheric pressure. This is done by appropriately operating the inert gas supply means 5 and the suction means 6 so that the internal pressure of the casting chamber 2 is in one of three modes: and below the atmospheric pressure.

(Problem to be Solved by the Invention) By the way, in precision differential pressure casting as described above, the molten casting material is effectively fed by the differential pressure machine and cast into the casting cavity as quickly as possible. It is important to do this to suppress the occurrence of casting cavities and obtain high quality cast products.

Therefore, the pressure difference between the melting chamber 1 and the casting chamber 2 is set to be as large as possible. However, even if this pressure difference is increased, since the mold 4 is interposed between both chambers 1.2, the pressure difference P1 between the pressure Pa of the sprue 41 and the pressure Pb of the casting cavity 43 will not necessarily match, It is extremely difficult to consistently obtain high-quality castings simply by adjusting the differential pressure. That is, mold 4
Since the mold is generally made of the same quality of mold material, the permeability of all parts is approximately equal. Therefore, when the mold is made of a mold material with high permeability, the pressure Pa of the sprue 41 quickly decreases and the casting cavity The pressure difference P1 from the pressure pb of 43 becomes small immediately. In addition, if the mold material is made of a mold material with low air permeability, it takes time for the pressure PB in the casting cavity 43 to decrease (to balance with the internal pressure in the casting chamber 2), and as a result, a predetermined pressure difference PB is achieved. You won't be able to get it. In this way, the pressure difference P
Despite the fact that the process is an important factor in determining the quality of cast products, the reality is that it cannot be set arbitrarily, and there has been a strong desire for measures to address this issue.

The present invention has been made in view of the above, and it is an object of the present invention to provide a new mold and an effective molding method thereof, which suppress the occurrence of casting cavities and make it possible to manufacture high-quality cast products.

(Means for Solving the Problems) The structure of the present invention for achieving the above object will be explained based on the attached embodiment diagrams. 1 to 3 are longitudinal cross-sectional views showing various aspects of the mold of the present invention, FIG. 4 is a vertical cross-sectional view showing an example of the mold manufacturing method of the present invention, and FIG. 5 is a vertical cross-sectional view showing various aspects of the mold of the present invention. It is a vertical cross-sectional explanatory view showing an example of a pressure casting device. That is, in the differential pressure casting mold according to claim 1 of the present invention, in the differential pressure casting mold 4 having a sprue 41, a runner 42, and a casting cavity 43 that are in communication with each other, at least the cavity 43
It is characterized in that the air permeability C1 of the surrounding mold material is higher than the air permeability C2 of other parts, and also claim 2
The method for forming a mold for differential pressure casting according to the above is a method for forming a mold for differential pressure casting 4 having a sprue 41, a runner 42, and a casting cavity 43 that are in communication with each other = 4- method, and the method includes: At least the above-mentioned cavity is formed by one or more means selected from the following: selection of heat-burnable kneaded material or heat-foamed material in advance, formation of cracks by thermal shock, application of vibration or pressure, combination of use of dense materials, etc. The mold 4 is shaped so that the air permeability C1 of the mold material around the mold material 43 is higher than the air permeability C2 of other parts.

As for the configuration of the air permeability C1 and C2, if only the air permeability C around the casting cavity 43 is made larger than the air permeability C2 of other parts as shown in FIG. In the case where the air permeability c1 around part or all of the casting cavity 43 and the runner 42 is made larger than 02, and furthermore, a part of the sprue 41 is included as a part corresponding to C1 although it is not shown in the figure, can be mentioned.

As a specific means to give the above-mentioned magnitude relationship between the air permeability C1 and C2, the average particle size of the mold material (investment material in the case of the lost wax method) of the part corresponding to 01 in Figs. 1 and 2 is set to C.
Make the particle size of the mold material larger than the average particle size of the same mold material in the part corresponding to 2, and make the particle shape of the mold material used for the same C work more complicated than that of 02 (for example, make the former polygonal and the latter spherical) (e.g.), the particles of the mold material used for C1 should be porous, and the mold material used for C1 should be pre-filled with heat-burnable cross-wire material (e.g., water, resin, carbon, wood chips, etc.) or foam material. C
Applying thermal shock to the part corresponding to □ to form microcracks in this part, applying vibration or pressure to the part corresponding to 02 when filling the mold material to tightly fill this part, and Fig. 3 For example, attaching a dense member around the sprue 41 as shown in FIG.

(Function) The mold 4 having the above configuration is installed in the casting chamber 2 of the differential pressure casting apparatus as shown in FIG. 5, as described above.

Then, the casting material 13 melted by the arc generator 11 is poured into the sprue 41 of the mold 4 from the crucible 12, and the inert gas supply means 5 and the suction means 6 are immediately operated to fill the melting chamber 1 and the casting chamber 2. A difference is formed in the internal pressure of the Due to this pressure difference, the molten casting material in the sprue 41 is forced into the casting cavity 43 through the runner 42, but as mentioned above, the air permeability C at least around the casting cavity 43 is lower than that in other parts. Since the air permeability is higher than C2, the pressure Pa in the casting cavity 43 quickly becomes almost balanced with the internal pressure in the casting chamber 2, and as a result, the pressure Pb becomes smaller than the pressure Pa near the sprue 41, and the rain The pressure difference P, (Pa-Pb) is approximately equal to the set internal pressure difference between the melting chamber 1 and the casting chamber 2. Therefore, by simply operating the inert gas supply means 5 and the suction means 6, an appropriate pressure difference P1 can be quickly and accurately set, and this pressure difference P□ causes the molten casting material 13 in the sprue 41 to quickly flow into the casting cavity. It will be cast in 43. The resulting cast product is dense and of high quality, with no casting cavities.

(Example) Next, examples will be described.

(Example-1) FIG. 1 shows an example of a differential pressure casting mold for casting a dental prosthesis, in which a wax pattern was formed on a fireproof model 45 and this was placed in a mold case 44. This is obtained by the so-called lost wax method in which external investment material 46 is filled and sintered, and a sprue 41, a runner 42, and a casting cavity 43 that communicate with each other are formed by the burned-out cavity of the wax pattern. In this case, the mold 4 is formed by selecting one of the above methods so that the fireproof model 45 has an air permeability of C□ and the external investment material 46 has an air permeability of C2.

(Example-2) FIG. 2 shows a differential pressure casting mold 4 by the lost wax method using the refractory model 45 as described above, but the part having the above-mentioned air permeability C□ partially extends to the external investment material 46. There is. In this case, when filling the mold case 44 with the external investment material as described above, fill it with an investment material of the same quality (particle size, shape, etc.) as the fireproof model 45, and then fill it with a different investment material to perform the C process. and C2
In addition, the filling method (for example, vibration or application of pressure) may be different depending on the rain area, and as mentioned above, heat-burnable cross-wire material may be added in advance or cracks may be formed due to thermal shock. Accordingly, the air permeability C□, C as shown in the figure
2 is formed.

(Example 3) FIG. 3 shows an example in which a dense member 47 is attached around the sprue 41. Such a mold 4 is obtained by attaching a non-thermal burnout material around the part corresponding to the sprue of the wax pattern, and then filling it with investment material and losing wax. Although an example using the fireproof model 45 is shown in the rotation, the case where this is not used is not excluded. Furthermore, when the fireproof model 45 is used, it is possible to have the fireproof model 45 and the external burial material 46 have approximately the same air permeability, or to have a relationship as shown in Example 1.2. In any case, since the sprue 41 is surrounded by the dense member 47, if the internal pressure difference between the melting chamber 1 and the casting chamber 2 is set to a predetermined value as described above, an appropriate pressure difference P1 can be quickly established. can get.

(Example 4) FIG. 4 shows an example of molding a differential pressure casting mold 4 without using a refractory model. As shown in Figure 4 (a), there is a raised part 4 in the center.
The mold case 44 is attached to a rubber base 48 having a diameter of 81, a wax pattern 49 formed by taking an impression from a patient's tooth, for example, is planted on the raised portion 481, and two types of investment materials are filled one after the other. , these are integrally sintered to obtain a mold 4 as shown in FIG. 4(b). Examples of two types of investment materials in this case are shown below.

■ Investment material to be filled first; Particle size distribution, 100 to 200 mesh 30% (weight) 325 mesh pass 70 It mixed liquid, a little ■ Investment material to be filled later; Particle size distribution, SO to 100 mesh 50% (weight) 100 ~20
0 mesh 30n 200 mesh pass 20 When the mixed liquid and the investment materials of ■ and ■ are filled as above and sintered,
The air permeability C2 of the part corresponding to (2) is determined by the fact that the average particle size of the investment material used for this is small and the liquid content is small, so the interparticle pores are small and there are few burnt-out cavities. □Becomes smaller.

These two types of investment materials are not limited to the above examples; for example, even if they are the same type of investment material, vibration or pressure may be applied to the investment material that is filled first, or the investment material that is filled later is Adding heat-burning mixed wire material or thermal foaming material in advance, or using investment material with particles of shape (polygonal or porous), or applying thermal shock to the part filled later after sintering to prevent cracks. By forming 01
, C2 can also be positioned as two types of investment materials.

In the above embodiment, a differential pressure casting mold for casting a dental prosthesis or an implant was used as an example, but it is obvious that similar effects can be obtained when casting other decorative accessories. be. It goes without saying that other effective means can be employed without departing from the scope of the present invention.

(Effects of the Invention) As described above, the differential pressure casting mold according to claim 1 of the present invention has a higher air permeability at least around the casting cavity than other parts, so it is easy to use this mold. When performing differential pressure casting of dental prostheses, implants, decorative accessories, etc., the pressure inside the casting cavity can be reduced by setting the internal pressure difference between the melting chamber and the casting chamber appropriately after pouring the molten casting material into the sprue. quickly becomes approximately equal to the internal pressure of the casting chamber, and as a result, the pressure difference between the sprue and the casting cavity becomes a dog, and due to the riser effect, the casting material is quickly poured into the casting cavity, and the casting process starts from the sprue side. Entry of pressurized gas into the cavity is reduced.

The occurrence of casting cavities is significantly reduced and a cast product of extremely high quality can be obtained.

In addition, in the shaping method of the present invention according to claim 2, the means for imparting the difference in air permeability include selection of the particle size or shape of the mold material, pre-addition of heat-burnable kneading material or heat-foaming material, and heating. Since simple means are employed, such as forming cracks by impact, applying vibration or pressure, or using a dense member, it can be easily carried out using existing equipment at the casting site.

[Brief explanation of the drawing]

1 to 3 are longitudinal cross-sectional views showing various aspects of the mold of the present invention, FIG. 4 is a vertical cross-sectional view showing an example of the mold manufacturing method of the present invention, and FIG. 5 is a vertical cross-sectional view showing various aspects of the mold of the present invention. It is a vertical cross-sectional explanatory view showing an example of a pressure casting device. (Explanation of symbols) 1... Melting chamber, 2... Casting chamber, 3... Partition wall,
4... Mold, 41... Sprue, 42... Runway, 43... Casting cavity. one or more one

Claims (1)

[Claims] 1. In a differential pressure casting mold having a sprue, a runner, and a casting cavity that are in communication with each other, the air permeability of the mold material at least around the cavity is higher than the air permeability of other parts. A mold for differential pressure casting, which is characterized by: 2. A method for forming a differential pressure casting mold having a sprue, a runner, and a casting cavity that are in communication with each other, which includes selecting the particle size and shape of the mold material, pre-adding a heat-burnable kneading material or a heat-foaming material, and heating. At least the air permeability of the mold material around the above-mentioned cavity is made higher than the air permeability of other parts by one or more means selected from the formation of cracks due to impact, the application of vibration or pressure, or the combination of using dense materials. 1. A method for forming a mold for differential pressure casting, characterized by forming a mold so that the mold is formed.