This Eyeglass Frame Durability Testing guide is issued by the Eyewear Frame Quality Management Department of iDetail Sunglasses Manufacturers.
1. Eyeglass Frame Durability Testing’s Aim
To check the distance in mm of the maximum opening of the temples after the stress imparted to the metal or plastic glasses.
2. Eyeglass Frame Durability Testing’s Standard of Reference
UNI EN ISO 12870 : 2004 Par. 4.8.3
3. Eyeglass Frame Durability Testing Procedure
3.1 Before measuring the frame, it is necessary to establish the clamping points (a) and the measuring point (b). The clamping point of the temples is found at a distance from the dowel screw center equal to 70% of the overall side length ±1mm. The measuring point shall be 15mm ±1mm nearer to the dowel screw than the clamping point.
3.2 Open the temples to the full extent, without tension, and measure the distance between the temples at the pre-determined measuring points and record this distance, d1.
3.3 Mount the spectacle frame on the test device and ensure that:
- The rotating clamp is on the same plane as the fixed clamp, and it is positioned at the nearest point of its rotation toward the fixed clamp;
- The bridge of the spectacle frame is freely supported on the bridge support;
- The horizontal relationship between the clamp, and the bridge support and clamp are such that the spectacle frame may be mounted with temples fully open, but not under tension, and with the bridge
support midway between the clamps; - The height of the bridge support is adjusted so as to ensure that the temples are in line with the axis of the clamps and parallel to the base of the device;
- The sides are clamped within 1mm of the calculated clamping point;
- The lock screw is loosened to allow the fixed clamp to align with the inward angle of the drop of the side, and the re-tightened;
- The revolution counter is set to zero.
3.4 Start the test apparatus and subject the frame to a cyclical rotating movement for a total of 500 cycles (+1 cycle) at a frequency of 40 cycles per minute.
3.5 After the completion of the 500 cycles, remove the frame from the apparatus and repeat the measurement as in point 3.2. Record this new measurement as d2. Check that the difference
between d1 and d2 does not exceed 5mm.
4. Evaluation of the Eyeglass Frame Durability Testing Results
The frame shall not:
- fracture at any point;
- be permanently deformed from its original position by more than 5mm after 500 cycles.
- except for frames fitted with spring hinges, which require more than light finger pressure to open and close the temples.
- for frames that are not fitted with spring hinges, have a temple that closes under its own weight at any point in the opening/closing cycle, or for temples fitted with spring hinges, the temples shall still support its weight in the open position (i.e. opened to the fullest natural extent without activating the spring mechanism).
