High-quality freeform machining of chemically strengthened glass using spark assisted chemical engraving

• First-time application of SACE for machining of Chemically Strengthened Glass (CSG). • Thermochemical etching mitigates the stress imbalance inherent to CSG. • Optimal SACE conditions (33V, 5 µm/s, 30 wt.% KOH) minimize chipping defects. • SACE enables freeform machining of CSG with minimal surface damage. This work demonstrates the first-ever utilization of Spark Assisted Chemical Engraving (SACE) for the freeform micro-machining of Chemically Strengthened Glass (CSG), achieving cut qualities that surpass existing laser and mechanical techniques for this notoriously difficult-to-process material. Using a Response Surface Methodology, the effects of key input parameters, voltage (33-37 V), cutting speed (5-15 µm/s), and electrolyte (KOH) concentration (24-30 wt.%), were investigated on critical output quality metrics, including chipping, cut surface roughness (S a ), and cut kerf. Statistical models were developed to predict outcomes, revealing complex parameter interactions including a synergistic effect between voltage and KOH concentration where high voltage degrades surface quality (especially at higher electrolyte concentrations). Among tested parameters, best results were achieved at 33 V, 5 µm/s and 30 wt.% KOH, resulting in superior surface integrity (S a ≈ 2.41 µm, chipping size ≈ 4.1 µm). SACE is validated as a viable single-step freeform machining process for CSG, mitigating defects common in mechanical and laser-based methods, and provides a practical solution for remanufacturing high-value CSG waste within a circular economy framework.