Optimize UV Lamp Life
Although the overall cost of UV curing lamps is only a small percentage of the overall production cost, they are not insignificant. Proper lamp maintenance and replacing lamps when necessary can avoid potentially costly production problems.
Monitor Operating Hours
Under normal production conditions, a UV curing lamp will give around 1,000 hours of full UV output and maximum performance. After 1,000 hours UV output decreases to around 70% and gradually declines thereafter. At this time there is a risk of uneven cure which can spoil a production run. It is recommended that lamps are replaced at 1000 hours or before the drop off of UV begins to adversely affect the cure.
Keep Lamps Clean
All lamps attract dust and contaminants during normal operation. Lamps should be cleaned at least once a month using a lint-free cloth soaked in IPA (isopropyl alcohol) or methylated spirits. Never touch quartz lamps with bare hands. Natural oily deposits left by fingers and palms create an opaque mark on the lamp thereby reducing UV transmission. These marks also cause the quartz to break down, causing premature lamp failure. Use caution when cleaning near the ends of the lamps excessive pressure may remove or smear the coating protecting the lamp electrodes.
To retain maximum UV output over longer periods, rotate the lamp 90 degrees after each cleaning. This prevents the lamp from sagging and extends its useful life. Caution: If your lamp has wire connectors, do not rotate beyond 360 degrees in one direction. Constant rotation in the same direction can cause excessive strain on the wire, and premature failure due to a dislocated connection.
When routinely rotating the lamp, make sure that the wire leads are in good condition. Check insulation on leads to be sure that it has not become brittle. If using metal-ended lamps, make sure the spring-loaded socket has sufficient tension to hold the lamp securely in place. Electrical arcs at the lamp end can cause damage to lamps, holders, and reflectors.
Another way to keep lamp efficiency at its optimum is to clean the reflectors regularly; the surface should be bright and shiny. The curing efficiency of UV lamps can be reduced by as much as 50% by dull, corroded reflectors. Check reflectors and replace them once they become dull or distorted. Many UV reflectors are designed to focus light onto the substrate; a reflector that is out of shape may focus the light unevenly, creating the potential for uneven curing.
The cooling and air exhaust system can affect efficient UV curing. Check and clean intake filters as they may become clogged with dust; which can cause the lamp to overheat and fail prematurely. Overheating can be detected by lamp bowing. As a UV curing lamp gets too hot the middle begins to bow and it will eventually shatter. When a lamp shows signs of bowing check that the cooling fans are operating correctly and that the impeller blades are not impeded by dust. If your system has a water-cooled reflector, check for scale or blockage in the cooling system tubes.
Overcooling can cause just as many problems as overheating. The temperature of the quartz body should be at or around 600-800 degrees Celsius. If the temperature drops below this, the vaporized mercury will begin to condense to its liquid state and the lamp will lose efficiency. The most obvious sign of overcooling is a long warm-up time at start-up. The lamp may also extinguish if a low-power setting is selected. You will also notice the lamp is not as brilliant as normal and the ends blacken early. To solve overcooling you may have to reset the cooling system to reduce airflow to the lamp.
If you have any questions or for advice on troubleshooting lamp/curing problems please contact us at (352) 624-3026.