1. Verify geometric accuracy (squareness)
Check whether the glass is square: Compare the length difference between the two diagonals (ΔD) to determine whether the glass has undergone diamond-shaped deformation (parallelogram deviation).
Standard requirements:
Ordinary architectural glass: Diagonal deviation ≤ 1.5 mm (GB 11614-2022).
High-precision electronic glass (e.g., smartphone covers): ΔD ≤ 0.3 mm.
Significance: Ensures the glass can be installed seamlessly into frames or devices, avoiding assembly difficulties or stress concentration caused by shape deviations.
2. Evaluate edge grinding machine processing quality
Positioning accuracy inspection: Excessive diagonal errors may indicate the following issues with the edge grinding machine:
Servo motor positioning inaccuracy (requires encoder calibration).
Mechanical transmission clearance (e.g., worn guide rails, loose belts).
Uneven grinding wheel pressure or wear (causing excessive grinding on one side).
Process optimization basis: Adjust grinding parameters (e.g., feed rate, grinding head pressure) based on test data.
3. Ensuring subsequent processing and installation
Hollow/laminated glass composite: If the diagonal of a single glass sheet is out of tolerance, it may cause edge misalignment or seal failure during multi-layer composite processing.
Curtain wall installation: Glass size deviations may affect the smoothness of the building's appearance and even pose a risk of shattering.
Electronic device bonding: Touchscreen glass for smartphones, tablets, etc., must strictly match the housing; ΔD > 0.3 mm may cause bonding bubbles or touchscreen malfunction.
4. Distinguishing responsibility stages
Production end vs. transportation end: If the diagonal is qualified before shipment but exceeds the tolerance upon arrival, it may be due to transportation collisions causing edge chipping or deformation.
Equipment fault tracing: Persistent deviations can pinpoint grinding machine faults (e.g., servo motor step loss).
Summary
The ultimate purpose of diagonal testing is:
To ensure precise glass geometry to meet assembly or further processing requirements;
To monitor grinding machine stability and prevent batch processing defects;
To provide data support for process improvements and enhance product yield.