This Spectacle Frame Bridge Deformation Test guide is issued by the Eyewear Frame Quality Management Department of iDetail Sunglasses Manufacturers.
1. Spectacle Frame Bridge Deformation Test Aim
To check the permanent deformation (in mm) of the glasses after having subjected them, with test lenses fitted, to the mechanical stability test.
2. Eyeglasses Bridge Deformation Test Standard of reference
UNI EN ISO 12870 : 2004 Par. 4.8.1
3. Eyeglasses Bridge Deformation Test Procedure
3.1 Mount the sample on the device with the sides of the test sample extended and with the front of the test sample downwards.
3.2 Clamp the sample within a tolerance of 2mm at the boxed center of one lens.
3.3 Lower the pressure peg so that it rests on the back surface of the unclamped lens within 2mm of its boxed center, ensuring that there is no movement of the lens. Record this as the starting position.
3.4 Move the pressure peg downwards slowly and smoothly, applying a force not exceeding 5N, for a distance equal to (10 ± 1)% of the boxed center distance (equal to 6.4mm).
3.5 Retain the initial displacement for 5s and then return the pressure peg to its starting position.
3.6 After a relaxation period of 20 s, again lower the pressure peg so that it just rests on the lens.
3.7 Determine, in millimeters, the movement of the pressure peg from the starting position and calculate the percentage deformation using the following formula:
Where:
f : is the percentage deformation;
x: is the movement of the pressure peg (in mm);
c: is the boxed center distance.
4. Evaluation of the Eyeglass Frame Bridge Deformation Test Results
The frame shall not:
- Fracture or crack at any point;
- Be permanently deformed from its original configuration by more than 2% of the distance
between the boxed centers of the spectacle frame (equal to 1.28mm).
