Cheap Lens cause IP Failures
Why do we need Lens? To concentrate the light, offer a required light distribution, or decorate the light to be cooler and look advanced?
Actually, there is another function for the lens: protect the LED against the water. This is very easy to be understood: for many outdoor lights and UFO high bay lights, the lens is the only material between the LED and water.
Let's assume that the "lamp IP failure" happens like this:
- In the outdoor lights factory, QC did IP testing after all the lens be assembled on the lights, the testing result shows very good---No IP failures.
- After the lights been used for months. Because of heat, the lens’ shape changed, the edge becomes bending.-- Normally this bending or deformation won’t happen, but it happens if the lens material is not a good PC.
Now, Let’s do some experiments in BackMorning’s LED Lighting laboratory, to check the above image.
Step 1. Select 2 new street lights:
- Use good PC Lens
- Use cheap lens
Step 2. Let’s do IPX5 testing on Sample A & B, according to IEC 60598. Result: Pass
Step 3: Put A&B in the oven for 7 days.
Step 4. After the oven testing, let’s check the lens’ shape and do IP testing. We get below important findings:
- B’s lens’ shape change. A is the same as before.
- B failed at the IP testing, A pass.
Based on the above, we recommend the buyer and factories to pay attention to the lens material: select good suppliers, and do enough verification for the material.