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UV LED Lamps – Frequently Asked Questions

UV LED TECHNOLOGY and APPLICATIONS

Which products can be polymerized with UV LED lamps?

Inks, varnishes, resins, adhesives and wood oils.

What is UV LED curing?

UV LED lamps, through intense UV rays, polymerize and cure the product instantly.

In which industrial processes are UV LED lamps used?

When it’s required to achieve high productivity, in different application fields:

• Silkscreen, flexographic & pad printing

• Dry offset printing

• Ink-Jet printing

• Labels printing

  • 3D printing

• Industrial ink-jet marking

• Printed Electronics

• Wood finishing

• UV Industrial painting

• UV grouting and resin filling

• Structural bonding with UV adhesives  and resins

• Medical and pharmaceutical

Can I always replace traditional UV lamps with UV LED lamps?

Before changing technology, it’s necessary to check the chemical formulations of the products to be polimerized, that might be not fully compatible with the radiation emitted by UV LED lamps.

How do inks/varnishes formulated for traditional UV lamps behave if they are used with UV LED lamps?

Products formulated to be used with traditional UV lamps contain mixtures of photo initiators tuned to the frequencies of Mercury UV lamps. UV LED lamps emit more selective frequencies that may not completely polymerize the products developed specifically for traditional UV lamps. It’s necessary to contact the product manufacturer (ink, varnish,..) to have more information and in case perform compatibility tests.

Which DROLED UV LED lamp best suits my needs?

You can choose your UV LED lamp depending on 4 main characteristics: radiation width, peak irradiance, UV dose and wavelength.

  • RADIATION WIDTH: maximum width (in millimetres) the lamp can reach and dry.
  • IPEAK IRRADIANCE: maximum irradiance (in W/cm2) from the lamp emitting window.
  • UV DOSE: quantity of energy emitted (in mJ/cm²) on exposed surface unit.
  • WAVELENGTH: maximum frequency peak (in nanometers) of the emitted spectrum.

UV LED lamps have a very tight and selective spectrum, so it’s indicated as a single frequency.

What if I need a complete system with DROLED UV LED lamps?

You can choose between different LED dryers, designed and produced internally, as: UV SAFE, CYL STATION and CONVEY CURE. The main functional features are: instant polymerization, programmable working cycle, touch screen settings management, operator safety, compact size and Plug & Play installation. Each system is equipped with DROLED UV LED lamps with specific wavelengths and optical systems.

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IRRADIANCE AND UV DOSE

Which peak irradiance rates are available?

UV LED lamps can have same dimensions but different maximum irradiance rates, depending on different UV curing needs.

Which wavelengths are available?

The main 2 available are: 365nm or 395nm. On request also 385 and 405nm

Which power and wavelength are the most suitable for my UV application?

Depending firstly on the product to be polymerized, then on the distance between the surface and the lamp and on the translation speed.

Which distance do I have to keep between UV LED lamp and the surface to polymerize?

Generally UV LED lamps have to be positioned quite close to the surface, but the working distance is different depending on the optical system of the lamp. Distance means the space from the lamp front glass and the support to be polymerized.

What happens if the lamp is too far from the support?

The product to be polymerized may not result properly cured, due to an insufficient energy peak, which does not complete the chemical reaction.

How can irregular and no-planar surfaces be cured with UV LED?

By adjusting the distance between the emitting window of the lamp and the surface to be polymerized, high radiant energy can still be obtained. Using multiple lamps in different positions, 3D objects can also be irradiated. Specific optical systems allow to dissipate less energy as the distance increases.

Can 3D objects be polymerized?

Yes, by using more lamps located in different positions and with specific optical systems, which allow less energy dispersion as the distance increases. DROLED UV LED lamps are also used in 3D printing for the immediate curing of the polymer.

Do UV LED lamps degrade or have performance drop during their life?

When they reach 20,000 working hours at full power, they have a slight decrease in performance of about 10%. The decay of traditional UV lamps is much higher, as after only 2,000 working hours it is about 80%.

What happens after reaching 20,000 working hours?

The lamp will continue to work even after 20,000 hours. The energy emitted will be slightly lower than a new lamp. This slight degrade in performance does not mean automatically to replace the lamp and can be compensated by adjusting the intensity of the lamp.

How frequent starts and stops impact on UV LED lamp lifetime?

Differently from traditional mercury UV lamps, frequent switching on/off of the UV LED lamp does not reduce its life indeed, its on/off frequency management extends its duration, since when the diodes are off, they do not work and therefore they do not degrade.

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DIMENSIONS AND MECHANICS

What size do UV LED lamps have?

DROLED UV LED lamps are available in various sizes to best suit the needs of the specific application. Refer to the single lamp data sheet to have detailed dimensions.

What is the “module” of the lamp?

The “module” is a portion of the lamp (base unit) that can be switched on/off individually.

If I have to dry a large width, should I use single lamps side by side or a whole lamp?

Three single lamps placed side by side have greater flexibility of use, compared to a whole lamp.

How can I radiate and cure correctly large widths?

Placing side by side more UV LED lamps with no width limit.

How can I fix mechanically the lamps?

Using the threaded holes, already present on the metal casing.

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POWER AND CONTROL

How are electrically powered the lamps?

By standard switching AC/DC power supplies, available on the market with many sizes and models.

Has power supply to be dimensioned and how?

The UV LED lamp manual contains all the detailed information needed.

Can I control UV LED lamps with PLC?

You can do it through direct analog and digital signals or through RS485 serial protocol.

How can I control UV LED lamp functions in easy mode?

Through analog and digital signals it is possible to: turn the lamp on/off, adjust the intensity, verify the lamp status and detect anomalies.

How can I control UV LED lamp functions in advanced mode?

Through a 2-wire RS485 serial link it is possible to control and query the lamp functions or the group of lamps, following the owner communication register available on the manual.

What is “Interlock” command needed for?

To connect a safety circuit (such as a limit switch actuated by a barrier), it has the priority over all other commands.

Can Interlock command be excluded? Yes, it can be by-passed with a connection bridge between two taps.

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OPERATING

Which instrument is necessary to check the irradiance emitted by the lamp?

A special UV-meter suitable for measuring UV LED sources. In detail:

  • the UV Meter (also called UV Radiometer) measures the UV intensity (in mW/cm²)
  • the UV Integrator (also called UV Dosimeter) measures the total amount of UV radiation during the exposure (in mJoule/cm²)

How are UV LED lamps cooled?

All the DROLED UV LED lamps have an air cooling integrated system.

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TECHNICAL SUPPORT

What happens in case of malfunction?

The intelligent internal electronic micro-processor constantly check the working lamp parameters and if it’s necessary, stops the working lamp, preventing failures.

How can I see if the lamp is not working properly?

When an alarm digital signal and LED signals are active.

How can I know the cause of the malfunction?

Most of the causes can be detected through LED signals flash number, corresponding to specific error codes quoted in the manual. You can also download the file LOG, depending on the lamp model.

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MAINTENANCE

What kind of maintenance do the lamps need?

The required intervention is very limited: simple cleaning of the emission window and of the air filters.

How can I clean the lamp if it gets dirty?

Debris and scales on the glass can be removed mechanically or with solvents.

How can I clean the air filters?

With a jet of compressed air. If they are very dirty remove them from the holder and wash them with water and a bit of detergent. Dry them after washing. Never use other liquids and/or solvents.

How often do I have to clean the filter?

Depending on the conditions of the working environment, on average every 2000 working hours.

What happens if I don’t clean the filters?

When filters are dirty, the air flow is reduced and the lamp stops automatically, signalling a malfunction.

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