Understanding the factors that drive CNC machining cost is essential for accurate budget planning. The price of a machined part is not a single number but the sum of many variables, each of which can be optimized with smart design choices. Knowing what contributes to the cost helps you make informed decisions during the design phase and evaluate quotes more effectively.
Material cost is the first and most visible component. Common materials like aluminum 6061 and mild steel are relatively inexpensive and readily available from stock. Exotic materials like titanium, Inconel, and specialty plastics can cost five to ten times more per pound. The material cost also depends on the stock size required your part may need a larger block than its finished dimensions to provide adequate clamping surface for machining. Choosing a standard material in a standard stock size is the most cost effective approach.
Machining time is the largest cost component for most parts. The time required to machine a part depends on its complexity, the number of features, the material hardness, and the required surface finish. Simple parts with few features and standard tolerances may take only 15 to 30 minutes of machine time. Complex parts with tight tolerances, multiple setups, and intricate geometries can take several hours. The shops hourly machine rate typically ranges from 60 to 150 dollars depending on the equipment type, location, and overhead structure.
Setup and programming costs are incurred once per order regardless of quantity. Programming time for a simple part may be one to two hours, while complex five axis parts can require eight to sixteen hours of CAM programming. Fixturing costs range from simple vise setups that cost nothing extra to custom fixtures that may add 200 to 1000 dollars to the order. These upfront costs are spread across the total quantity, so larger orders have lower per unit setup costs. For prototype quantities of one to ten pieces, setup costs dominate the per piece price.
Secondary operations like surface finishing, heat treating, and additional inspection add cost and lead time. A simple as machined finish carries no extra cost, while anodizing adds approximately 50 to 200 dollars per batch depending on part size and color. Powder coating adds 75 to 300 dollars per batch, and electropolishing adds 50 to 150 dollars per batch. Each secondary operation also adds three to seven days to the overall lead time. Specifying finishes only on surfaces that functionally require them reduces both cost and lead time.