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UV printing

LED UV curing

The hardening of the ink under UV light. A lamp directly next to the print head cures every printed pass immediately.

Explained in more detail

Hobby and small-business machines cure almost exclusively with UV LEDs, typically at a wavelength of 395 nm, less often 365 to 405 nm. Compared with older mercury vapour lamps, LEDs hardly get warm, need no warm-up time, produce no ozone and last much longer. If the lamp power is too low, the ink stays tacky and adheres worse. If it is too strong or scatters light towards the print head, ink cures onto the nozzle plate. Some machines first pin the ink lightly and then cure it fully, which gives smoother surfaces. UV light harms eyes and skin, so never look into the lamp unprotected.

Where does the term come from?

LED is the abbreviation for "Light Emitting Diode". Curing means that the ink cross-links chemically into a solid film; it does not dry in the strict sense.

In practice

  • If a print is still sticky, smeary or smells strongly after curing, it is not fully cured and not fit for sale.
  • Use only ink that is approved for your machine, because the photoinitiators must match the wavelength of the LED.
  • The lamp ages: for the lamps of its UV DTF devices, Procolored states a lifespan of about six months with normal use.
  • Check the filter or protective glass on the lamp regularly; ink mist on it weakens curing.
  • UVA light is only partly visible, so the lamp is stronger than it appears; never look into it without shielding.

Not to be confused

The smell during printing is not ozone. UV LEDs produce practically no ozone; the smell comes from the ink, so ventilate anyway.

Frequently asked questions

What wavelength does a UV lamp in a UV printer have?

Usually around 395 nm, overall in the range of 365 to 405 nm, that is in the UVA range. The datasheet of the device states exactly which.

Why is my UV print sticky?

Usually it was not fully cured, for example because the lamp has weakened, too much ink was laid down at once or the lamp filter is dirty. Check the lamp and print mode, and if necessary run the print under the lamp a second time if the software offers that.