Support Strategies for Internal Channels and Sacrificial Geometries in Industrial Additive Manufacturing

Internal channels are frequently presented as a geometric advantage of additive manufacturing. In production, however, an enclosed channel is acceptable only when supports, uncured liquid, loose powder, sacrificial material, gas and cleaning residues can be recovered and when the resulting feature can be verified. This review compares self-supporting orientation, removable solid supports, soluble sacrificial supports, powder-bed self-support, support-bath or embedded printing, and indirect tooling routes. It separates the printed state from the washed, cured, debound, sintered and conditioned states; identifies non-compensatory access and safety gates; and proposes measurable recovery endpoints, worst-case witness geometries and state-specific acceptance records. The central conclusion is that channel design is a recovery and qualification problem as much as a geometric one. A route that prints a channel but cannot prove its cleanliness, continuity, dimensional state or service compatibility has not demonstrated a manufacturable channel.