Xaar has launched the Xaar Nitrox inkjet printhead, for printing speeds of up to 100m/min.

Xaar’s TF Technology recirculation minimizes temperature changes within the printhead, virtually eliminating print density variations and controlling viscosity to provide consistent printing across the swathe throughout each job.

The Nitrox Core is designed for applications using oil-based inks, such as in ceramic tile decoration, while the Nitrox Pro can handle more demanding fluids including soluble salts and frit used for printing glass.

Backwards compatible with the Xaar 1003, there are three variants of the Xaar Nitrox - the Core, Pro and Elite.

If you thinking of purchasing a UV-curable inkjet printer, you might like to know what kind of technology is inside.

Digital printers, screen printers, offset press commercial printers, sign shops, and photo labs primarily want to produce images that satisfy their clients and thereby bring in a profit for everyone concerned. So the results of the printing are what count. It is rare that a print shop owner or manager has time to learn what is going on inside the machine, other than the obvious need to know enough to properly operate the printer.

But all kinds of interesting technology are inside a UV-curable flatbed printer. If you are seriously thinking of purchasing a UV-curable inkjet printer it is expected that you will visit trade shows and a manufacturer’s or distributor’s demo centers too. Before you make your actual purchase it is essential that you visit companies that have UV-curable inkjet printers at work.

So let’s look at a UV-curable printer from the point of view of what an end-user, who is thinking of buying this printer, needs to know.

What features and factors to look for when making your Short List of brands and models to consider buying

Printheads as one factor of Print Quality

There are subtle differences between some printheads; dramatic differences among others. So a printhead is a crucial component in a UV printer.

If you are a print shop owner, manager, or operator, it definitely helps to know the pros and cons of the printheads that are inside the printer(s) on your short list. You do not need to know whether it is a side-shooter or top-shooter or shared-wall (leave that to the engineers). What you need to know is how robust they are, how often will they fail, how long does it take to replace them, how long the warranty is.

What part of the Printer System Moves?

When you visit a major trade show you may notice that the relationship between the positions of the printhead and the media vary. There is no one single technology of media-feed that has become de-facto standard. Each printer integrator has done their best to maximize the benefits of whatever feeding mechanism they have decided on. There is no one system, which is perfect, and no system (so far), which has enough serious downsides so as to suggest that you should always avoid it.

Holding stationary materials or transporting moving substrates impacts on image quality. In a regular solvent or aqueous printer the printheads go back and forth on the X axis. The media is transported incrementally by being pushed or pulled along the Y axis. Most of these printers have optional settings for bi-directional printing (faster) or uni-directional printing (tends to be higher quality, but slower).

Anatomy of the flatbed feeding and take-up system

When you print with a water-based or solvent ink printer, the media or substrates are made for feeding through such a printer. The solvent printer manufactures know more or less what kinds of materials will be fed through their printers, so they can arrange the pinch rollers and all the rest of the feeding system to accommodate these materials.

But with a UV flatbed, people may run ceramic tiles, glass, or wooden doors through the printer. The manufacturer can’t be expected to design a special feeding system for each coefficient of friction of the surfaces of these often radically diverse materials. So some materials feed better than others

But even once the material is printed, it has to move all the way through the system and out the other end. A 9-foot length of wood, Styrene, Sintra, foamcore or whatever needs somewhere to go. This somewhere is the take-up table.

How is the Material Held Flat?

There are several ways to hold rigid material flat:

• A vacuum table
• Pinch rollers

Pinch rollers are as much for feeding the material as they are for holding it flat. Pinch rollers usually work in unison with a grit roller. The pinch roller is on top; the grit roller is at the bottom. But there are many variations and size differences of these roller systems.

Vacuum tables can be very expensive, as in five to fifteen thousand dollars, or more, depending on size. Vacuum tables are not as effective as you might wish; a vacuum table can keep a piece of foam-core from sliding, but a vacuum table can’t hold a warped foam-core totally flat. In other words, a vacuum table does not suck most materials totally flat; at best it holds them relatively flat, and keeps them from sliding around.

UV-cured Ink

UV-curable ink has been used for many years in the screen printing industry. But getting the ink to jet through a piezo printhead, accommodating the speed, and a host of other factors, was not easy.

When hit by UV radiation, UV-curable ink becomes a solid instantly. Once it is no longer a liquid, it can’t enter the pores of the material. Since the material usually is solid, and has no ink receptor layer, the ink stays on top of the material. Indeed you can run your fingers over the image and feel the ink.

LED and Mercury Arc Lamp on the field

Production expectations as much as the technology dictate the uptake of LED and the speed with which it replaces Mercury Arc curing.

But its just a matter of time before LED technology can match Mercury Arc curing’s performance. When it reaches that point it will cease to be viable, but that point is still on a far horizon.

Mercury Arc lamps are ideal light sources for applications that require high intensity spectral lines emitted in the deep UV to visible light regions. Their unique UV emission spectra make them popular for unique applications that need enhanced UV output such as UV spectroscopy, UV curing and other industrial processes, and environmental and medical applications.

LEDs are based on semiconductor technology. Specific wavelengths are directly emitted by the current input. The spectrum is a quasi-monochromatic radiation in defined wavelengths, e.g. 365nm, 385nm or 405nm.

Protecting against Static Electricity

When the material receives a static charge then the entire surface of the printer attracts ink. The ink is drawn to the entire surface of the material, even outside the area of the intended design.

Static charge will be worse in dry environments (such as during winter with central heating), or in an area with rugs, or if the material itself comes with static charge because it is rubbed (while cleaning, for example).

To protect against build-up of static charges on the material most printers are grounded and some printers have static bars.

Conclusions

Every aspect of UV-curable ink printers has advanced in the last years. Ink formulations and printhead engineering are leading the way. In other words, the ink used today is dramatically better than the ink first offered in 2001 and 2002. Manufacturers now see a growing market for their products and are willing to devote R&D dollars to make products tailored for the needs of inkjet printers, such as smaller size, drastically lower prices, and less heat emission.

There are a few technologies and methods to produce artificial UV light, the main purpose of this light radiation is to be used for UV Curing, which is a high speed curing process in which high intensity ultraviolet light is used to create a photochemical reaction that instantly cures or bonds inks, adhesives, resins, coatings and other materials.

The main advantage of curing with UV-light is the speed at which materials or products can be processed, this advantage is especially important since the positive effect it has on production costs, by helping reduce productions times, thus helping increase productivity and reduce costs. Decreasing the curing or drying step time in a process can help reduce flaws and errors, mainly reducing the time that an ink or coating spends wet, which is one of the most critical steps and the most likely to produce errors. This can increase the quality of a finished item, and potentially allow for greater consistency.

Types of UV radiation

Ultraviolet light is a particular portion of the light spectrum, there are different types of UV wavelengths and they have specific applications, commonly the most used ultraviolet radiation (UVR) is categorized from 200nm to 400nm for UV A, B and C; UVR can be more widely defined as light radiation between 10 and 400 nanometers as specified by a more comprehensive subdivision by the ISO Standard ISO-21348, in which the UV wavelength is categorized in 9 different ranges.

UVC is a lesser energetic UVR used for top surface curing that creates surface hardness and abrasion resistance

UVB is a medium energetic UVR capable of deep penetration curing that creates coating and adhesive toughness

UVA is a more energetic UVR used to cure the deepest layers

EUV or extreme UV, has a wavelength between 10 and 120nm, which is considered as ionizing radiation.

Types of UV curing lamps

There are two general types of UV lamps available, broad-spectrum metal arc UV lamps and LED-based UV curing lamps. In contrast, LED UV curing lamps have a consistent output, no bulbs to replace and no warm-up time, among other advantages.

The standard broad-spectrum metal UV lamp has been the norm within the industry for many years, and several sub-categories exist for specific applications.

LED-based UV lamps will have a quite narrow spectral output based around a single wavelength e.g., 280nm, 365nm, 385nm, 395nm, and higher.

High Pressure UV Curing lamps (HP-UV) (also known as Metal Halide lamps), typical HP-UV curing lamps (Mercury) have short wavelength outputs that peak at 254nm and 365nm. A basic mercury HP-UV lamp will emit energy in both these ranges, but its strongest emission is in the short wavelengths.

To alter the spectral output and access these additional radiation peaks – additive lamps are created by dosing the lamps with heavy metal compounds, this is called “doping”. Commonly used additives for HP-UV curing lamps are Gallium- doping (400 -450 nm) and Iron-doping (350 – 400 nm). Other additives are available dependent on the specific application.

Vacuum-sealed medium pressure UV lamps (MP-UV or MP-HO) lamps are mainly manufactured for disinfection applications. MP-UV lamps are used in a variety of applications from curing (UVA) to microbial disinfection (UVC).

MP-UV lamps are made from high-quality quartz crystal, hermetically sealed using molybdenum foil within the hard quartz capillary, later pure tungsten pin electrodes are added with an over-wind of throated tungsten, each lamp is pumped and filled with an inert Argon gas in a precise process ensuring total accuracy of fill pressure and mercury content. The lamp is then completed by the use of either a metal or ceramic base and suitable electrical termination.

Low Pressure UVC Amalgam Curing lamps (LPA-UV lamps) are perfectly suited for curing cationic based inks, cationic inks are generally an epoxy based resin that is cured by UV lamps. The wavelength of UV radiation is required to stimulate the photo initiator. The cure rate for these inks depend upon the specific ink’s formulation, light source and initiator contents.

UV Light-emitting diodes (LEDs) can be manufactured to emit radiation in a specific wavelength range. LED UV curing lamps offer many advantages over conventional UV curing systems including long-life, cool temperature cures, no warm up times, constant intensity and reduced power consumption.

Curing equipment based on LEDs can achieve uniform frequency and intensity output for consistent cures, facilitating superior process control, increased manufacturing throughput and lower operating costs. LED UV light curing offers several significant advantages over conventional arc UV sources, however LED UV curing lamps feature narrower wavelength spectrum emission than that of conventional equipment, so non-standard or special wavelength requirements may not be cheap to manufacture or sometimes even possible to find.

By having a clear understanding of the UV curing process and the technology already available, manufacturers can make educated selections to optimize their process.

The majority of UV curing inks begin curing when exposed to the correct light, and will stop if the light is removed, so it is important to ensure a full cure is achieved in the exposure process.

UV lamps can be specifically matched to special or "non-standard" inks or coatings with different photoinitiator sensitivities and activation wavelengths such as UV LED inks.

Safety standards for children’s products have been always in the eye of the consumers; the parents. As a parent I always find myself reaching for products without BPA o any chemical that can damage or put my child at risk. Obviously, there are many brands out there that consider these aspects as a priority. Roland DGA’s recently launched the new V-BOND Ink for VersaUV LEF2 Series for UV printers which can be a great option for many businesses manufacturing children-products related.

The V-BOND Ink is compatible with any VersaUV® LEF2 Series of flatbed UV printers and it meets key safety standards that allow it to be used for printing on items designed for children, such as lunch boxes and toys. Roland DGA is a California, U.S.-based brand, a leading provider of wide-format inkjet printers, cutters, graphic arts, signage, fine art, UV, engraving, 3D, among many others. Besides delivering great color results and well-adhering to multiple kinds of substrates, this new Ink is low-VOC Nickel-free and it meets the requirements of the CPSIA (Consumer Product Safety Improvement Act) and California Proposition 65. Fulfilling these standards led this product to expand its opportunities for LEF2 users which can also mean entering into the toy and other variety of kids products market.

“New V-BOND Ink is safe for indoor printing and it’s formulated to bring out the best in our LEF2 series printers,” said Jay Roberts, Roland DGA’s UV printer product manager. “But, most importantly, it expands the product personalization and customization universe for end-users significantly. Because this ink meets the most rigorous safety requirements, it’s unbeatable for customizing toys and other children’s products, creating braille signage, and much more.” Besides just considering toy brands and products, V-BOND ink could be perfectly used for direct printing on school supplies, stationery, fashion, jewelry, hygiene products, electronic accessories, kitchen and culinary products, pet products, among many more. It is available for CMYK and also Glossy and White. For a wider and richer color gamut, V-BOND ink can also be combined with Roland DF’s True Rich Color 2 profiles. Using the gloss one lets users incorporate dimensional effects as well as unique textures into the prints, while the white is perfect to print vibrant graphics and dense colors on clear substrates.

V-BOND ink has quick-drying properties and it’s a long-lasting ink, so users may consider it a great product considering its durability and scratch resistance. So, cost-effectiveness is a big yes for them. Using V-BOND ink together with Roland DF’s LEF2 printers makes it safely to print onto plastics, paper, ceramics, acrylics, brushed metal, etc.

So V-BOND promises a lot with this and we are definitely seeing more not only about this amazing ink but also from this huge brand as well.