Part Complexity
RP: Unlimited
If a prototype can be modeled with design software, it is possible to build it with little impact on time or cost. The ability to quickly and cost-effectively produce complex parts is one of RP’s biggest benefits.

CNC: Limited
CNC machining must deal with every feature in a part, and this can add time and cost. As the complexity of the part rises, so do the number of setups and tool changes. High aspect ratio features, deep slots and holes and square corners can challenge the most expensive CNC milling machine. While a five-axis mill and some ingenuity can overcome challenging features, something as simple as an undercut can produce problems.

Feature Detail
RP: Varies
There are situations in which RP can produce features that CNC cannot. For example, RP can produce sharp inside corners and features with high aspect ratios, such as deep, narrow channels or tall, thin walls, ribs and posts.

CNC: Varies
For many features, CNC has the advantage over RP. Sharp edges, smooth blends and clean chamfers are among the details where CNC excels. This is especially true when evaluating detail in terms of accuracy and surface finish.