Model-Based Feedforward Control of Part Height in Directed Energy Deposition

Area of Science:

• Materials Science and Engineering
• Manufacturing and Industrial Engineering
• Control Systems Engineering

Background:

• Geometric accuracy is crucial for Directed Energy Deposition (DED) in repairing and fabricating complex metal components.
• Existing methods often struggle to maintain consistent part height due to process dynamics.
• Precise control over melt-pool geometry is essential for achieving targeted deposition accuracy.

Purpose of the Study:

• To develop and evaluate a model-based feedforward control strategy for laser power in DED.
• To achieve targeted part height accuracy by dynamically regulating melt-pool geometry.
• To reduce geometric errors in metal additive manufacturing processes.

Main Methods:

• A nonlinear inverse-dynamics controller was derived based on a dynamic model of melt-pool geometry.
• The controller modulates laser power in a hatch-by-hatch, layer-by-layer manner.
• The derived laser power trajectory was implemented as a feedforward control on an Optomec LENS MR-7 system for Ti-6AL-4V deposition.

Main Results:

• The model-based feedforward control demonstrated a 24-42% reduction in average build height error compared to constant or trial-and-error laser power strategies.
• Experimental validation confirmed the controller's effectiveness in achieving targeted build heights for L-shaped structures.
• The proposed control method significantly improved geometric accuracy over conventional approaches.

Conclusions:

• Model-based feedforward control of laser power is effective for enhancing geometric accuracy in DED.
• The developed controller offers a significant improvement in part height control for metal additive manufacturing.
• This approach provides a robust solution for fabricating complex components with high fidelity.