User login

UV Curing

(November 2000) posted on Tue Nov 14, 2000

Bron Wolff discusses how you can assess and improve your UV-dryer performance by learning from his company's experience.


By Bron Wolff

We wanted to see the effect of using a lower wattage setting on temperature and cure. So we cut the lamp power to 200 watts/in. and adjusted belt speed so that the printed substrate received the same energy dosage as it had at 300 watt/in. What we discovered was that the ink cured just fine and heat was also reduced. At that point, the metaphorical light bulb went off in my head! I though that if it worked at 200 watts/in., why not at 125 watts/in.? The fact that most printers use this power setting as "standby" mode when they break for lunch was far from my mind.

Initially, our 125 watt/in. setting was really delivering only around 84 watts/in. And when we tried to run the system at this power level, the lamps turned black at the ends--too little power was available to excite the mercury gas. So, we returned to our lamp manufacturers and asked them if the could increase the amount of mercury halide in the lamps. The amount they added was based on the electrical parameters of our equipment and the average power level our shop could supply to the equipment--these values differ from plant to plant.

Despite the increased mercury halide, the modified lamps still didn't produce enough energy to cure the inks, although they did keep heat down. So we began to consider other ways we could change them. In our next round with the lamp manufacturer, we asked the company to change the diameter of the lamp and the thickness of the quartz envelope. Because the heat is generated in the quartz around the lamp, the theory was that a smaller lamp diameter and thinner quartz wall would require less power and let more UV energy through. After several revisions, we received the modified lamp, which finally provided the irradiance we needed to get a successful cure without the heat.


Terms:

Did you enjoy this article? Click here to subscribe to the magazine.