Diameter in general a relatively large diameter sprue is recommended because this improves the flow of molten metal into the mold. Investment casting is an industrial process based on lost wax casting one of the oldest known metal forming techniques.
Efficient local exhaust ventilation to minimise exposure to fume vapour from the molten product is strongly recommended especially in wax melting and pattern assembly areas.
Sprue wax composition. Investment lost wax casting is a widely used casting technique in which a pattern usually made of wax is formed by introducing a molten wax composition into a mold having the shape of the finished part and by cooling it until solidification in the ceramic shell method the pattern or a cluster of such patterns isare gated to a wax sprue. The product should only be used in well ventilated areas. Paraffin wax fume 2 mgm3 twa 2 mgm3 8002 74 2 engineering control measures.
The results of this study imply that soybean which is an environmentally non hazardous material with a low cost price is a novel and superior alternative to the conventional additives in investment casting pattern wax compositions. Investment casting has been used in various forms for the last 5000 years. For high density alloys like gold the recommended sprue design includes the use of wider larger diameter sprues of shorter length and have a flared point of attachment to the wax pattern for better results.
The remainder of this chapter deals with refractory investments and casting methods used for the fabrication of small dental crown and bridge prostheses either by casting metal or by hot pressing ceramic. Us5518537a us08404305 us40430595a us5518537a us 5518537 a us5518537 a us 5518537a us 40430595 a us40430595 a us 40430595a us 5518537 a us5518537 a us 5518537a authority us united states prior art keywords wax investment casting weight composition weight percent prior art date 1995 03 14 legal status the legal status is an assumption and is not a legal conclusion. The molten metal is cast into this space.
Requirement of sprue. Provide exhaust ventilation or other engineering controls to keep the airborne concentrations of mists andor vapors below the recommended exposure limits see below. Figure 10 2 wax pattern of a crown restoration attached to a sprue and ready for investing.
Describe the composition and use of inlay wax casting wax and baseplate wax. Sprue design is a key and controversial variable that can affect the properties of metal alloy castings. Sprue wax page 3 of 4 section 8 exposure controlspersonal protection.
An eye wash station and safety shower should be located near the work station. Molar around 25 mm 10 gauge premolar 2 mm 12 gauge 9. Once the wax is burned out a space remains where the sprue and wax pattern were.
The term lost wax casting can also refer to modern investment casting processes. Is a small amount of additional wax added to sprue former 1 mm below wax pattern. The molten metal is then forced through the sprue or ingate created by the sprue former base into the mold cavity left by the wax.