Process Optimization for Ultra-Precision Machining of HUD Freeform Surface Mold Cores Based on Slow Tool Servo

Area of Science:

• Optical Engineering
• Manufacturing Technology
• Precision Engineering

Background:

• Head-Up Display (HUD) technology relies on optical freeform mirrors for compact systems and high imaging quality.
• The complex shapes of these freeform mirrors present significant ultra-precision manufacturing challenges.
• Developing efficient manufacturing processes is critical for advancing HUD technology.

Purpose of the Study:

• To present a systematic optimization framework for the ultra-precision machining of HUD optical freeform mold cores.
• To address challenges in manufacturing complex, large-aperture freeform optical components for HUDs.
• To provide a feasible process solution for high-quality HUD optical element manufacturing.

Main Methods:

• Designed an off-axis three-mirror HUD system using an XY polynomial freeform surface model.
• Developed a hybrid trajectory planning method (equidistant projection and cubic spline interpolation) for Single-Point Diamond Turning (SPDT) Slow Tool Servo (STS).
• Integrated surface design, tool path planning, vibration analysis, and process parameter optimization.

Main Results:

• Clarified selection criteria for tool parameters like tool nose radius and effective cutting angle.
• Quantitatively revealed the impact of Z-axis vibration on surface roughness and waviness.
• Successfully fabricated a high-precision freeform surface mold core through ultra-precision turning experiments and on-machine measurement.

Conclusions:

• The proposed systematic optimization framework is effective and feasible for ultra-precision machining of HUD optical freeform mold cores.
• The developed process solution provides essential technical support for the high-quality manufacturing of HUD optical elements.
• This research contributes to overcoming manufacturing challenges in advanced optical components for automotive HUDs.