ABSTRACT
Production processes can be characterized by the simple fact that something is produced as a result of a number of deliberate actions. The product may be an item such as a glass bottle, a brake drum, a tennis ball, or a block of cheese. Alternatively, it may be a polymer produced in a batch chemical process or a shipment of a mineral ore blended from stockpiles that are being continuously replenished. Whatever the case, there will usually be several measurable quality characteristics of the product for which specifi cations exist. These are often a pair of limits between which the appropriate measurement is required to lie. Sometimes a specification is a one-sided limit such as an upper limit on the amount of an impurity in the product of a chemical reaction.
