Investment casting costs

These super-alloys are remarkable materials. They resist creep so well that they can be used at 850°C - and since they melt at 1280°C, this is 0.72 of their (absolute) melting point. They are so hard that they cannot be machined easily by normal methods, and must be precision-cast to their final shape. This is done by investment casting a precise wax model of the blade is embedded in an alumina paste which is then fired the wax bums out leaving an accurate mould from which one blade can be made by pouring liquid super-alloy into it (Fig. 20.4). Because the blades have to be made by this one-off method, they are expensive. One blade costs about UK 250 or US 375, of which only UK 20 (US 30) is materials the total cost of a rotor of 102 blades is UK 25,000 or US 38,000. 

The primary attractions of SMGs are one handed use, large magazine capacity and simplicity of design which allows for low cost production in small home workshops, without the need to resort to investment castings, milling machines, and other exotic manufacturing techniques and equipment. 

Can be combined with investment casting to produce parts with increased complexity with reduced cost. 

Space Velocity = 20,000 h-1 N 2O conversion = 90% No Retrofit Factor Includes the costs of LPG as reducing agent at 0.35 EUR/kg, which includes transportation casts. All cost and investment estimates are based on 2001 casts. 

Due to its batch character, the rotary furnace provides an equal flexibility as the coreless induction furnace in the cast iron foundry. The investment costs however are lower. A 5 tonne furnace costs EUR 500000 - 600000, of which 30 % are for the exhaust system and dedusting. The rotary furnace is also a good alternative for the small-scale cold blast cupola, due to its higher flexibility and lower environmental costs. Rotary furnaces are used for melting volumes of 2 to 20 tonnes, with production capacities of 1 to 6 tonnes per hour. 

This process is of interest because of its very low environmental impact. However, as its process cycle involves many steps, the moulding rate is low and the gap between starting times for each new different casting is lengthy. Moreover investment costs are very high. As a consequence, this process has found only limited application. 

Slip casting is low-cost production process. No large initial investment is needed. Complex shapes such as gas turbine rotors can be obtained. The slip can penetrate any intricate regions of a complex mold. Large articles such as wash basins are made using this method. 

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