UV Spot Curing Systems Overview

The process of ultraviolet or UV curing is defined as hardening (a photochemical process by which monomers harden or cure (polymerize or cross-link) upon exposure to ultraviolet radiation), of a liquid film of material when exposed to ultraviolet light. The particular substance to be processed may vary widely depending upon its application and final use, but basically is composed of base polymers, non-solvent diluents and photo initiators. Specially formulated monomer will polymerize when exposed to ultraviolet light. This UV "curable" monomer includes a chemical that absorbs UV energy and initiates a polymerizing reaction in the monomer.

Materials to be cured by exposure to UV energy are specially formulated to polymerize in a certain way. This system of curing is used on numerous products and in many industrial processes. While the list below indicates the more widely used, others are being added as the technology becomes more widespread.

While each application is unique, they share a common concern - efficient and effective curing of UV sensitive materials. UV technology provides many advantages compared with other drying procedures. The foremost is instant, uniform curing that allows for immediate processing and fast turn-around. That means post press operations can be performed immediately reducing work in process storage, and thus improving productivity and profit. UV technology helps in production of eye-appealing products that are economically competitive with other forms of curing and protection. Product will have increased life and dependability because substrates cured with UV systems exceed most specifications for rub and wear resistance. Three standard systems are available.

A UV Spot Curing system consists of a Light Source and a Power Supply. Most units on the market combine these two functions into one housing. The heart of the system is a lamp that produces UV light of sufficient intensity. The light source has an ellipsoidal reflector that surrounds the lamp and collects most of the lamp output. The radiation from the lamp is focused onto a spot and piped through a light guide (quartz or liquid) for delivery to the desired curing location. Special filters are placed in the path of light beam and the inlet of light guide to deliver light of various spectra to suitable for particular UV Spot curing application. Systems with two different lamp power ratings are offered; 100W, High Pressure Mercury Vapor Short Arc Lamp and 200W, High Pressure Mercury Xenon Lamp.

The power supply unit provides constant electrical power to the lamp. Some of the control features are discussed here.

EXPOSURE CONTROL
Each UV Spot Curing System has a built in shutter that can be operated manually from a switch on the front panel or remotely with a foot pedal. The shutter can also be programmed to open from 0.1 second to 999 seconds with a built in timer control.

SAFETY INTERLOCKS
The Light Source unit has safety interlocks. The housing door for replacement of lamp has an electrical interlock to shut down the system if the door is opened without turning the system power off. This prevents access to the lamp when the system power is on thus preventing operator exposure to the radiation and protects against inadvertent contact with the hot lamp. There is a thermal interlock that turns the lamp off in the event the temperature within the housing exceeds safe operating level.

LAMP AGING
The lamp should be replaced every 1,000 hours to ensure spectral fidelity and proper level of intensity. There is an hour meter that monitors and displays the lamp age. It serves as a convenient reminder of when the lamp should be replaced.