Bhargav's Blog

Grafica's UV Curing Machine

Type and color of the substrate

There are substrates and colors that absorb UV more than other ones. They make curing slower. Curing may change depending on the grade of the substrates even though they are of the same kind.

Color of the ink (quality of pigment and influence of color-matching) The pigments that absorb more UV make curing slower. The more these pigments are contained, the slower curing becomes. Therefore, there is a limitation to the density and opacity of UV ink. Curing of matched colors may be poorer than each standard color which is used to make these matched colors. Printers must be careful of such matched colors as the mixture of opaque white plus other dark colors like black and blue.

Thickness of ink film
The thinner the ink film is 10-12 microns, the better curing is. Thicker ink film than 15 microns may result in poor adhesion due to insufficient curing. CLEAR INKS cure even if ink film is thicker than 100 microns.

UV power and integral light
There are two ways to measure curing: UV power and integral light, decided by lamp power and the type of the lamp. UV power plus curing time make the integral light. Integral light changes depending on the number of the lamps and curing time with different conveyor speed.

Although general curing efficiency is measured by the integral light, UV power has more effects to the thickness of the ink film stated in 3-d and inner curing. If UV power is not strong enough, inner curing cannot be improved even if the integral light is increased by more curing time. In this case, lower the height of the lamp or strengthen the lamp power.

Temperature of UV dryer and pre-heating
Environmental temperature of UV irradiation gives much influence to curing. The higher the temperature is, the better curing is. For this reason, pre-heating before UV irradiation improves curing, which leads to good adhesion.