While UV curing offers many advantages over other drying methods, it has its own requirements for maintaining process control. In particular, UV lamps and irradiators deteriorate over time. Depending on several variables, lamps may last less than 250 hours or over 3,000 hours. The only way to accurately monitor UV output is by measuring with a radiometer.

Using a UV radiometer can save time and money in the following areas:

• Reduce setup time


• Reduce cost of spoiled materials


• Replace lamps only when necessary


• Replace reflectors only when necessary


• Avoid costly downtime


• Avoid production of unsatisfactory product leading to unhappy/lost customers.

A radiometer is used to quantify the dosage and intensity necessary to result in a proper cure, both in the lab before going to the production floor, and while in a production environment.

Take a radiometer measurement after a test product is determined to be at optimal cure. This becomes the benchmark value for "good" product. Then, continually monitor the curing characteristics as you increase line speed. When you are just beginning to undercure, note the line speed, the number of lamps you are running, the lamp settings, the peak intensity values, and/or UV dosage. Once you've identified the threshold of failure, multiply the UV dosage reading by 1.2 to give yourself a 20% cushion. Then slow the line speed down while monitoring the cure properties to measure for overcuring. Once overcuring is observed, multiply UV dosage by 0.8 to give yourself a 20% cushion on the down side. You now have your benchmark value, your minimum, and your maximum "cure window" value.

Radiometer functions range from measuring simple intensity and dosage to sophisticated mapping and graphing devices. Most UV radiometers on the market measure in the UVA spectrum (320 nm-390 nm), because the majority of the chemistry responds to this band of energy.

It is possible to fully analyze the entire curing system using a mapping device. It measures and stores the UV intensity and temperature data it encounters. The data is then captured and displayed on a computer.

A pass-through radiometer can be sent on a conveyor through your UV curing system. They accurately reflect how much UV energy your material to be cured is actually receiving.

Sometimes a pass-through radiometer cannot physically fit into and travel through the curing machine. For these circumstances, specially designed radiometers apply.

There are miniature sensors that can travel through nearly any type of unit. Generally coin sized, after retrieval these sensors are connected to a base unit that downloads the readings.

A new style of pass-through radiometer is the ultra-thin unit. With an ultra-thin profile of only ¼ in., the whole unit (not just a small sensor) can pass through the narrowest of curing environments.

When even the smallest sensor can't fit, there are flexible, pass-through options that can safely travel through rollers. One option has 5 thermally stable color changing zones on a flexible test strip. The other option also uses a flexible test strip. After exposing the test strip, it is measured by a dosimeter which produces a numerical value reflecting UV energy received.

Online monitoring is used when continuous monitoring is desired (not just spot-checking). While the overall cost of using online monitors is generally more than using one portable radiometer, if continuous measurements are required or if using a portable radiometer is not an option, online monitoring is desirable, effective, and reliable.