Speaker
Description
Metal additive manufacturing enables the production of complex near net shape geometries but remains limited in achieving the dimensional tolerances required for functional assembly features. Consequently, post process CNC machining is commonly employed within hybrid AM-CNC workflows to manufacture precision features. A potential advantage of this approach is the direct use of additively manufactured support structures as machining fixtures, reducing tooling cost and lead time. However, the suitability of support structures for machining high tolerance features remains insufficiently understood. This study investigates the root causes of dimensional deviations when AM support structures are used as fixtures during CNC machining of a tight tolerance O ring groove requiring ±20 µm accuracy. Impact hammer (tap) testing was performed on the cutting tool assembly and workpiece system to determine natural frequencies, while in-process acoustic monitoring was used to detect chatter and machining instabilities. Results show that the support structure based fixturing strategy produced greater dimensional deviation and groove ovality, causing the feature to exceed tolerance limits by 19 µm. Acoustic measurements and modal analysis revealed overlap between the natural frequencies of the workpiece fixture system and machining excitation frequencies, identifying resonance induced vibration as the primary source of dimensional inaccuracy. The dominant tooth passing excitation frequency was approximately 286 Hz. The findings demonstrate that support structures are only suitable as machining fixtures when their dynamic stiffness prevents resonance and associated chatter.
| Speaker Country | United Kingdom |
|---|---|
| Would you like to publish your paper in the special issue of BHM "Berg- und Hüttenmännische Monatshefte" | Yes |