How to avoid microcracks in the processing of optical blank glass?

The core of avoiding microcracks in optical blank glass processing is to control stress concentration, ensure processing uniformity and accurately control it from three aspects: operation, parameters and protection.

Key control measures

Optimization of machining parameters: diamond cutter is used when cutting, and the feed speed is controlled evenly (it is recommended to be ≤5mm/s) to avoid excessive instantaneous pressure. In the grinding stage, the abrasive particle size is gradually reduced from coarse grinding to fine grinding, and the machining allowance of each working procedure is less than 0.1mm, thus reducing the surface stress.

Reduce mechanical impact: handle glass with care when taking and placing it, to avoid hard contact with fixture and workbench. Soft clean gasket can be laid on the contact surface. Ensure that the clamping force of the fixture is uniform during processing, and do not locally squeeze the glass.

Control environment and cleanliness: keep the processing environment dry (humidity ≤60%) to avoid stress cracking caused by water penetrating into glass micropores. Remove the abrasive chips on the glass surface in time during processing to prevent the abrasive chips from being scratched or extruded for the second time to produce microcracks.

Auxiliary safeguard means

Material pretreatment: check whether there are primary cracks in the blank glass before processing, and pre-chamfer the corners to eliminate stress concentration points.

Equipment status: Ensure that the tools and abrasives are sharp and without gaps, and regularly check the runout of the main shaft of the equipment (≤0.002mm) to avoid uneven cutting caused by vibration.

Detection and pre-judgment: use strong light irradiation or microscope inspection to find early micro-cracks in time and stop processing to avoid defect expansion.