Abrasive Flow Machining

Abrasive Flow Machining (AFM), also called extrude honing, is a non-traditional finishing process that forces a semi-solid, abrasive-laden viscoelastic media through or across a workpiece to deburr, polish, radius edges, and remove small amounts of hard-to-reach material from internal passages, cross-holes, and complex cavities. The media acts as a flexible cutting tool, enabling controlled edge break and surface improvement in geometries that conventional tools cannot reliably access.

In a CNC shop, AFM is typically scheduled as a post-machining finishing operation after milling, drilling, or casting when components contain internal passages, intersecting bores, or cross-holes that require controlled radiusing and consistent surface finish. The workpiece is mounted in a holding fixture, and either one-way or two-way flow is used to extrude abrasive media through the part. Removal is intentionally low, so the process conditions surface rather than removing bulk stock. Operators control media viscosity, abrasive size and concentration, pressure, flow rate, temperature, and cycle time to achieve repeatable results. AFM is particularly valuable for fuel injection nozzles, hydraulic manifolds, and other flow-critical parts where burrs and tool marks restrict flow or create stress concentrations. Although it adds a dedicated process step, it reduces scrap and rework by reaching features that are otherwise manually deburred or left with incomplete edge control.

• ⚠️Over-processing critical edges: Over-aggressive pressure, extended cycle time, or oversized abrasive can enlarge holes and over-round tight passageways, damaging calibrated features on flow-critical nozzles and leaving parts outside tolerance.
• ⚠️Inconsistent media behavior: Drifting temperature, viscosity, abrasive loading, or particle wear makes cutting uneven, leaving burr remnants in some channels and overcutting others, so part-to-part finish quality becomes unpredictable.
• ⚠️Poor fixture coverage or misalignment: Tooling that fails to isolate the target zone or locate the part consistently lets media bypass intended surfaces, producing incomplete deburring, uneven finish, or damage to sealing faces.