Once GCD extraction has been performed, the cost engine begins costing a part by expanding the process-level templates associated with the current process group. Expansion potentially produces every instantiation of the templates, that is, every possible process routing for the process group. Each routing includes some, but not all, nodes from a template.

During expansion, the cost engine visits each template node, and evaluates the node’s associated template pruning module, if there is one. If a node’s template pruning module returns false, the node is removed from the template. All the node’s descendents in the template are removed as well. This can prevent the production of a large number irrelevant routings.

A template pruning rule might, for example, eliminate all turning routings for parts that have no valid turning axis.