The investment casting process starts before wax reaches a die. The drawing must explain what the component does, which surfaces locate it in an assembly and what condition the customer expects at delivery. Those decisions influence pattern design, machining stock and inspection, so a successful order connects engineering review to every later operation.

Two foundries can quote the same drawing through different casting routes and arrive at very different prices. Investment casting vs sand casting is therefore a comparison of finished-part requirements, not simply the purchase price of a rough casting. A small valve component with several inaccessible features presents a different decision from a large housing whose working faces will be machined anyway.