Compare sand casting and investment casting in terms of accuracy, surface finish, and cost, and mention typical applications.

• A. Sand casting yields the finest surface finish and highest accuracy; investment casting is cheap and fast.
• B. Investment casting is cheaper and faster for simple shapes; sand casting offers superior surface finish.
• C. Sand casting is cheaper and faster with rougher surfaces and lower accuracy; investment casting yields finer surface finish and higher accuracy but costs more and is slower.
• D. Investment casting cannot be used for complex shapes.

Answer: (C)

The main idea is how the mold-making method affects accuracy, surface finish, and cost, and how that shapes typical uses. Sand casting uses a mold made from packed sand, so it’s quick to set up and relatively inexpensive. That makes it ideal for larger parts or low-volume production, but the sand mold yields a rougher surface and looser tolerances, so the accuracy is lower.

Investment casting, or lost-wax casting, builds a ceramic shell around a wax model and then melts the wax away. This process produces a very smooth surface and tight dimensional tolerances, giving higher accuracy, but it involves more steps, materials, and handling, so it is slower and more expensive, especially for larger parts or high-volume runs.

Typical applications reflect these differences: sand casting is common for large, simpler, robust parts like engine blocks, machinery housings, or piping fittings; investment casting is preferred for intricate or high-precision components such as turbine blades, dental implants, jewelry, and other detailed parts.

So the described statement matches because it states that sand casting is cheaper and faster with rougher surfaces and lower accuracy, while investment casting yields finer surface finish and higher accuracy but costs more and is slower, with appropriate applications for each method.