TABLE OF CONTENTS Estimating process costs accurately at the precision needed for competitive contract bidding, for example is a specialized job. It is commonly based on interpolation or extrapolation of known costs for similar, previous jobs, appropriately scaled. Our interest here is not in estimating cost for this purpose; it is to compare approximate costs of alternative process routes. This can be useful even when imprecise. We illustrate the method with a cost model for one of the most common choices: that of a batch shaping process. It requires certain user-specified inputs, such as local labor costs, as well as values for cost-related attributes of each process.
The manufacture of a component consumes resources (Figure 18.15), each of which has an associated cost. The final cost is the sum of those of the resources it consumes. They are defined in Table 18.4. Thus, the cost of producing a component of mass m entails the cost C m ($/kg) of the materials and consumable feed-stocks from which it is made. It involves the cost of dedicated tooling, C t ($), and that of the capital equipment, C c ( $), in which the tooling will be used. It requires time, chargeable at an overhead rate ? oh (thus with units of $/h), in which we include the cost of labor, administration and general plant costs. It requires energy, which is sometimes charged against a process step if it...
