JPH0613221Y2 - Sprue structure for lost wax casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a structure of a sprue part for connecting a pattern part and a molten metal residue when casting glass or ceramics by the lost wax method.

[Conventional technology]

The lost wax method is used for casting metals, especially dental metals such as crowns. The wax pattern of the lost wax is composed of a pattern portion, a hot water remaining portion, and a sprue portion connecting both of them. Recently, it has been attempted to apply the lost wax method to glass and ceramics. In the case of metal casting, the sprue part was linear and had a small diameter. However, when applying the lost wax method to glass or ceramics, casting is performed in a state where the melt has a higher viscosity than metal.
Therefore, the sprue part is thicker than that of metal.

[Problems to be solved by the device]

As shown in FIG. 4, when a molten glass or ceramics is cast by the lost wax method, the sprue portion (2) is thick when the molten metal residue (1) undergoes solidification shrinkage, so the pattern portion (3) There is a drawback that tensile stress is applied to the cast, and cracks occur in the cast, particularly in the cast near the connection with the sprue. In the case of metal, ductility and strength are large, so such defects are not recognized. Since glass and ceramics are inferior in strength, ductility and thermal shock resistance to metals, cracks are likely to occur even with a small stress during casting.

[Means for Solving the Problems]

In the case of glass and ceramics, in addition to the above causes, when casting thin materials such as dental crowns and laminated veneers, the difference in the coefficient of thermal expansion between the investment material and the casting, and the glass etc. exceeds the transition point. There are many causes of stress such as rapid expansion. Therefore, it is very difficult to completely suppress the occurrence of cracks. The present inventors have paid attention to the generation of this crack at the sprue portion. When the sprue part is made thin, cracks occur in the sprue part without entering the casting. However, it was discovered that if the sprue part is made thin, insufficient casting occurs and sufficient casting cannot be performed. Therefore, it was found that even if the sprue part is thickened, if there are defects, stress concentrates there and causes cracking. Therefore, the present invention was completed by studying a method of artificially causing a defect in the sprue part. That is,
The present invention is characterized in that a sprue for connecting a pattern portion and a molten metal residual portion when casting glass or ceramics by the lost wax method has a notch or a bent portion or both of them. It is a sprue structure for lost wax casting.

[Constitution of device]

In the case of the notch of the present invention, the notch shown by (5) is introduced into a part of the linear sprue portion of FIG. 1 (2). The cross-sectional shape of the sprue is usually circular, but may be any shape such as angular or elliptical. The notch may have a wedge shape or a bowl shape as shown in FIG. The position of the notch may be provided at any position of the sprue portion, but a position closer to the pattern portion (3) is more preferable because the pattern portion is cut off after completion of casting.

In the present invention, as a method of causing cracks in addition to the notches, the sprue portion may have a bent structure instead of the straight shape as shown in FIG. The bent structure may be a semi-circular shape shown in FIG. 2 or a crank type or a bend. further,
As shown in FIG. 3, it is more effective to use the notch (5) together with the bending structure (2).

[Effect of device]

According to the method of the present invention, when the glass or ceramics is cast by the lost wax method like the conventional metal, the sprue portion is forced to be cracked to prevent the generation of cracks in the pattern portion. be able to. The sprue structure of the present invention is particularly effective when used for casting dental materials, and exerts its power in casting calcium phosphate-based materials, which has recently attracted attention.

[Brief description of drawings]

FIG. 1 shows one embodiment of the present invention, which is an example having a wedge-shaped notch in the sprue part, FIG. 2 is an example having a semi-circular sprue part, and FIG. 3 is a semi-circular sprue. This is an example in which a part and a wedge type notch are used together. FIG. 4 shows an example having a conventional linear sprue portion. (1) Remaining hot water (2) Sprue (3) Pattern (cast) (4) Investment (mold) (5) Notch

Claims (1)

[Scope of utility model registration request] 1. A sprue for connecting a pattern portion and a molten metal residual portion when casting glass or ceramics by the lost wax method has a notch, a bent portion, or both. Sprue structure for lost wax casting.