In metal additive manufacturing, internal channels are often used for cooling, weight reduction, or fluid transport. However, many engineers overlook how critical powder flow is during the printing and depowdering stages. Trapped powder inside narrow, sharp, or dead-end geometries can compromise part functionality, increase weight, and introduce hidden defects that are only detected during post-processing or actual use.
Proper design for powder evacuation starts with escape holes. For ceramic-filled or high-viscosity powders, escape holes under 3 mm often become ineffective. A rule of thumb is to maintain at least 2–3 mm diameter escape channels for standard metal powders, and up to 4 mm or more for specialty blends. Sharp internal corners and sudden changes in direction can further hinder powder flow and should be replaced with gradual curves or tapered transitions.
Angling features to leverage gravity during depowdering is another effective strategy. For instance, orienting channels to promote downward powder flow or using features like internal ribs to prevent powder settling in dead zones can help. Computational depowdering simulations are increasingly being used to validate these designs before printing begins.
By considering powder flow early in the design stage, manufacturers avoid costly part failures and reduce the need for manual intervention post-print. Not only does this improve the yield of functional parts, but it also boosts throughput and ensures more reliable performance in end-use scenarios.