Ultraviolet light is found in three different light spectrums – UVA, UVB and UVC. The wavelengths vary from 100 to 400 nanometers, just between the visible and x-ray light frequencies, UVA (315-400 nm), UVB (280-315 nm) and UVC (100-280 nm). Generally, the majority of the sunlight’s Ultraviolet Radiation (95%) that reaches earth is of the longer wavelengths known as UVA. However, the other 5% is the shorter length UVB and it’s UVB light that causes sunburn.
Fortunately, all the UVC light and 95% of the UVB light from our sun is absorbed by our atmosphere… which is a very good thing because UVC light can cause Cellular and DNA damage. The short wave length of the UVC light makes it quite effective in combating bacteria and viruses due to its ability to breakdown cells. Adept has had the opportunity to develop these typed of “germicidal” lamps but here we are going to discuss the use of a UVA light in manufacturing.
Often in manufacturing environments there are gels and adhesives used that require curing during an assembly line processes. Specifically, we were task with the replacement of an older fluorescent technology with UVA LEDs to cure a specific gel in an manufacture operation. The gel in order to be dispensed required the addition of salicylic acid. Salicylic acid is commonly used to combat acne, however our product was not being used in that capacity and therefore the FDA required that the remaining amount of salicylic acid needed to be below a certain level. Fortunately, UVA light had the ability to evaporate the acid without disturbing the final product.
Previously, our client was using large banks of black light fluorescent bulbs, specifically 16 bulbs in total per assembly line, with 11 lines running at capacity of 2 x 10 hour shifts per day. Therefore, a sizable expense was the bulb management, maintenance and replacement. This process was a perfect target to take advantage of the low cost and high reliability of UVA LEDs.
- Selection of the correct UV LED is critical for a project of this nature. LEDs of the same color can often emit different frequencies and intensity. Therefore, the use of BIN’s is necessary to assure the LED selections are similar and will produce the correct frequency light for curing as well as the proper intensity for a completed curing cycle.
- Brand and specific style LED was also a consideration. Assurances from the LED manufacturer
- In addition, custom LED drivers were necessary as well as the ability to tune each subsystem to assure full system conformity.
- LED performance and life also is a function of LED junction temperature; therefore, a thorough heat transfer analysis was required to assure junction temperatures remain within acceptable limits. For this case the high intensity, large quantity of LED’s and narrow band of frequencies necessary required forced convection cooling and large heatsinks for success.
- Finally, the system had the requirement to retrofit into the existing assembly line. Therefore, the design envelope was fixed and well defined, an asset in some regard a hindrance in another.
To date our client has enjoyed 7 years of trouble-free operation unhindered by fluorescent bulb management, maintenance, and replacement. Just recently we were contacted by our client because one of the 132 power supplies had reached its end of life. Seven years has passed since this particular power supply was available and was no longer in production, but a replacement was easily discovered and downtime was minimal. This is (and continues to be) one of many LED light success stories saving time, money, and energy.