In metal additive manufacturing, it’s common to aim for near-net-shape parts, but assuming that critical surfaces will meet final tolerances straight off the printer can lead to costly issues. Features such as sealing faces, bearing interfaces, or precision fits often require post-processing to achieve the necessary accuracy and surface finish.
Failing to include machining allowance on these areas removes the safety margin needed to correct minor distortions, surface irregularities, or dimensional variation inherent to the printing process. Without this buffer, parts may fall out of tolerance and require reprints or complex rework, increasing both cost and lead time.
A best practice is to intentionally add stock, typically between 0.3 mm and 1 mm depending on the process and material, on all critical surfaces. This ensures that machining operations can bring the part into final specification reliably, without compromising geometry or functionality.
Equally important is clear communication. Designers must explicitly define which surfaces require machining and include this information in technical drawings and specifications. This alignment prevents confusion downstream and ensures that manufacturing teams execute the process as intended.
Designing with post-processing in mind is essential for achieving reliable, production-ready parts. When done correctly, it transforms additive manufacturing from a prototyping tool into a robust and repeatable production solution.