Introduction and short technological overview
Wide-format inkjet printing has been available for some time, but it seems that recently this print technology is making more and more in-roads into print shops. This might be due to the fact that the technology has improved in the last few years and has become more stable and more affordable. Before I talk about wide-format inkjet printing, a brief introduction into the different print technologies used on a wide-format printer is in order. There are two different types of inkjet technologies available that can be used inside a wide-format inkjet printer.
One of them is the thermal inkjet technology (TIJ), which is based on a micro heating element in the print head. When heat is applied to the ink, a bubble forms and forces the ink out of the nozzle. Sometimes thermal inkjet is also called bubble jet. Due to the nature of this inkjet technology, the ink is most likely water-based and the ink has to be able to withstand the stress of the short super-heating that occurs in the print head. The ink can get heated for a very short period of time up to 300ºC. This means that the materials used in the ink need to be able to withstand this kind of thermal stress.
The other technology is the piezo-crystal based technology. In this type of inkjet, an electric pulse is applied to the piezo-crystal and it changes its shape. This creates a pressure inside the printhead which forces the ink out of the nozzle. There are many different types of piezo-crystal based inkjet print heads available. The type of designs used for these inkjet heads are: push/piston, bend, squeeze, shear and shared-wall shear. The name of the design implies what the piezo crystal will do in order to force the ink out of the nozzle. Since there is no heat involved in this type of technology, piezo-based printheads can be used with a wide variety of ink types. This includes water-based, solvent-based and UV curable inks and also includes special inks like opaque white and metallic inks. Today this is the more widely used technology, since a wide variety of inks can be printed.
Another inkjet technology that can be used is the so-called continuos inkjet (CIJ). With this technology a constant stream of inkjet droplets is produced from the print head. An electrical charge can be applied to the ink. When the charged ink passes through an electrostatic field, the charge of the field determines if the inkjet droplet falls into the gutter or onto the substrate. This type of technology is not used on wide-format inkjet printers, since it can use up quite a large amount of ink.
One of the latest developments uses so-called MEMS-technology. MEMS stands for microelectromechanical system and is used in printheads to achieve higher print resolution. These type of printheads are used more and more in single-pass printers, where an array of printheads is used across the width of the printer and applies the ink onto the substrate once. There is no back-and-forth traversing of the printhead assembly and so-called interweaving is used to achieve a high-quality print.
Inkjet inks for wide-format printing
For wide-format and super-wide format inkjet printers it is important to know what type of ink system is being used with the printer. One might wonder why this is important. It is important since no one ink can be used for all types of applications and substrates. There are solvent-based inks that can be used on a variety of substrates, but these inks require a good ventilation system in the print shop to remove the emitted VOC’s. In order to move away from harmful solvents, the so-called eco-solvent inks were developed. These inks are quite often glycol-based, which is derived from mineral oil. The eco-part of these inks stem from the fact there is less need for forced ventilation to remove harmful airborne substances. The substrate needs to be warmed up to become receptive for these inks and the solvent needs to be removed as well to achieve proper drying.
Water-based inks are another possibility for inkjet inks. Since it is necessary to remove the water from them after printing, either the media gets heated and/or forced air is applied to the media to remove the water, so the ink will be dry. Prints made with solvent- or water-based inks quite often require a lamination so the prints can be handled rather quickly and also extend the fade-resistance of these prints in an outdoor application. One might say, “well then, use UV-curable inks. The inks are almost instantly dry and the prints can be handled rather quickly. Quite often the prints are durable enough for an outdoor application where resistance to sunlight and weather is required.”
This answer is only partially correct. UV inkjet ink does adhere to many different substrates but not all of them. Certain substrates still need a corona-type pre-treatment or coating to make it receptive to this type of ink. The media also needs some kind of heat application during the print process to soften up certain type of plastic materials so they become receptive to the ink. With UV-curable inks there is always some curing after the initial print phase. This might lead to possible odour generation if the printed material is rolled up right away after printing.
Usually, UV-curable inkjet inks are cured (aka dried) using a mercury-vapour UV lamp that can be part of the scanning print head assembly or is built stationary into the machine and the media passes under the lamp array. One of the latest technological advancements in this area is the UV-LED technology. This technology uses small but powerful LED’s that emit the required UV rays. Their advantage is that the LEDs do not consume as much power as a conventional mercury-vapour lamp. The LEDs also do not get very hot, so they can be closer to the printed substrate. UV-curable inks made for use with mercury-vapour lamps cannot be used with UV-LED equipped printers.
This is due to the nature of the emitted UV spectrum. Mercury-vapour lamps emit a broader UV spectrum with some peaks in the 200 nm range of the 200 to 400 nm UV spectrum. UV-LEDs emit only a very narrow band of UV light, which is more towards the middle of the UV spectrum. The photoinitiators in the UV ink that are needed to start the curing process have be tuned for this different type of UV spectrum. Since this technology is still being developed and is not as widely used as mercury-vapour UV curing, the photoinitiators used for LED curing are more expensive and therefore make the ink also more expensive. One still has to take into consideration that a mercury-vapour UV curing system is drawing a lot more electrical power that a UV-LED system. You need to do the calculation which system will cost you more to operate and how do the cost of the consumables play an overall role.
The latest developments in the inkjet ink field are the latex inks and resin-based inks. Both ink systems use water as the main ingredient but the carrier for the pigments is either latex- or resin-based. Inkjet printers using these types of inks also need heaters built into the printer, so the media becomes receptive for the ink and the ink also dries properly. HP just introduced their new and improved latex inks. According to HP, these inks outperform eco-solvent inks in regard to fade-resistance and other properties. It is also said that a wide variety of substrates can be used with these new latex inks. Since the inks are water-based there is no need for extra ventilation to remove any harmful substances emanating from the printer.
Various reports on the internet suggest that there will be some quite interesting developments happening very shortly and they will be shown at drupa 2012.
drupa 2012, the inkjet drupa, again?
This leads me to my next segment. drupa 2008 was touted as the inkjet drupa. Many companies showed their advancements in inkjet technologies, but many products that were shown at the 2008 drupa never really made it into the marketplace or did not fare very well. The upcoming drupa will show the advancements that have been made and that inkjet will deliver on promises made in the past. It will be interesting to see what kind of developments have happened in this market segment.
What classifies a printer to be a wide-format printer?
Wide-format printing seems to encompass any inkjet printer that can print on substrate up to 2.5m in width and super-wide printers are those that are capable of printing onto substrates up to 5m in width. The ink and inkjet head technologies differ from manufacturer to manufacturer and each of the wide-format or super-wide printers cater to certain market segments.
Wide-format printing at Graphics Canada 2011
At the Graphics Canada trade show I spoke to a few suppliers and manufacturers of wide-format inkjet printers. It seems that the ability to also print in white greatly enhances the capabilities of the inkjet printer and what types of jobs can be printed. Back-lit displays are certainly one of the applications for this type of technology, but so are wide-format banners. The only restriction for printing a banner is the width of the machine, since the possible length is only determined by how much material is on the substrate roll.
Almost every manufacturer of wide-format inkjet printers emphasized the ability to print on both flat as well as rolled up substrates. These are called hybrid machines. All the wide-format inkjet printers that I saw on display used UV-curable inkjet inks. Interestingly enough none of the exhibitors had set up special ventilation for their machines. This is something worth looking into if a print shop decides to install one of these printers. I mention this since some people are (without knowing it) sensitive to the typical smell of UV-inks and some people might become sensitized to the chemistry used in UV-inks. This sensitization can range from skin rashes to severe allergic reactions. It is possible that some wide-format inkjet printers have a ventilation system built into the housing and that any air that is being vented passes through an activated charcoal filter that will eliminate any odours and harmful substances. Any ventilation requirements need to be checked with the manufacturer of the inkjet printer that you would like to purchase and install in your print shop.
Some of the wide-format inkjet printers used 5 colours (CMYK White) and others used up to 10 colours (CMYK, lc, lm, lk, white, 2). Some machines are able to add orange and violet or orange and green to the range of printable colours, so the colour gamut of the inkjet printer gets larger and more specialized and corporate colours can be printed.
The drop volume ranges from 8 pl (picolitres) up to 40 pl. This does not mean that the inkjet printer that uses a higher drop volume prints with lesser quality. The drop volume depends on the quality mode that is being used (draft, quality and high quality), but also the size of the print that is being produced and its viewing distance. A very large banner is usually not looked at from a short distance, but from a great distance. If you look at a very large banner up close you can see all the printed dots. Although this might remind some of a Roy Lichtenstein piece, it is not intended to be viewed like this.
Print speed is also something that one needs to look at. The Agfa :Jeti 3020 Titan printer that was shown at the trade show impressed me with its fast printing speed. Other companies also have products that can print fast. When making a decision what kind of wide-format inkjet printer you would like to purchase for your print shop you need to take into consideration the capabilities of the printer, the types of inks that can be used with this printer, the speed of the printer, the market you are going after and what are the costs of the consumables that are required to keep the printer operational.
There is one wide-format printer from Durst that can have three different rolls of substrate on it. This means that you can print three different jobs at the same time! Representatives from Durst also said that a scenario like this means that the three rolls of unprinted substrate can be loaded into the printer before the operator leaves for the night and that the job can be printed overnight. When the operator comes in the next morning the jobs are done and can be processed further. If there are any malfunctions overnight, the system can be set up to send you a text message to alert you to what went wrong or what needs the operator’s attention.
In my opinion a clear indication that wide-format inkjet is a technology that is here to stay is if a company like Heidelberg teams up with EFI/Vutek and shows wide-format printers at the trade show. Various types of machines were on display and the capabilities to print on various substrates was shown. The large Heidelberg banner hanging at the booth was printed on a printer that was five meters wide. Some might say that something similar happened in the past with the NexPress venture, but I think Heidelberg has learned from its mistakes.
Quite a few company representatives mentioned that wide-format inkjet printing will be taking business away from screen-printing companies. One might ask oneself why would that be? Let’s take the example of a four-colour back-lit display. For this job not only are stencils required for the process colours, but also for the opaque white, that is usually applied on the back of the process colours so the light from the light source is diffused and cannot be seen from the viewers standpoint.
The next issue with this job being done using screen-printing technology is accurate registration between the various print stations. Also, the size of the printed sheet is determined by the maximum size that can be used on that type of screen-printing equipment. With a wide-format inkjet printer, many of these issues disappear. The plastic-type substrate can be either be a sheet or come from a roll and all four colours plus white can be printed at once.
There are even different ways to apply to opaque white, as it was shown at the Heidelberg EFI/Vutek booth. This is not possible with the screen-printing process. Depending on the size of the back-lit display, it can be possible to print more than one display at the same time and it is also possible to do variations of the same display depending on the local market and language requirements.
A screen-printing company printing the same job would have to manufacture different stencils for all the various jobs around the same back-lit display, driving up the cost of the final product. With a wide-format inkjet printer, these types of jobs can be done in a more price-conscious fashion and repeatable quality can be delivered to the customer. Wide-format inkjet printing also allows you to produce low quantity runs at decent costs. The same job done with a screen-printing press would cost more, since the same stencils need to be made for 10 or 100 copies.
Don’t forget that most of the work done on wide-format inkjet printers is done in relation to signage.
Is wide-format inkjet printing the future of the printing industry?
This is a like asking if we will be driving flying cars 20 years from now or will they be powered by something other than fossil fuels. The future of the printing industry has become very unpredictable. Many new technologies are being developed in all areas of the industry, many of which we are currently not aware. Technologies like the iPad are very disruptive and who knows what will be developed in this area? Children who are currently growing up with these kinds of technologies have a very different approach to them than those who still remember 14.4k or 28.8k connection speeds to the Internet. Some time ago I read an article in the Globe and Mail about people who are developing children’s books for the iPad. The books are not just recreations of the printed versions, but are being developed to use the interactivity that the iPad can provide. Children that read a book like to think of it as an iPad that does not work. Disruptive technologies will always emerge and pose challenges to the print industry. The challenge is that it is necessary to react to them faster and faster.
What does that mean for a print company? The answer is obvious and I am probably repeating what many of you know already. You cannot stay in business by just offering print services alone. You have to diversify your business and offer many different services to your customers. There is no golden rule of what you should or should not do. You have to find out what kind of market you can serve, what equipment you need, and if you cannot offer all those services yourself, you need to partner with a company or a few companies that will enable you to offer a well-rounded set of services to your customers, while your customers deal only with you as the solution provider.
Wide-format and super-wide-format inkjet printing is part of the future for the printing industry. It will not replace current print technologies, but it is part of the services print companies can offer to their clients. Wide-format inkjet printing will take business away from screen-printing companies as I outlined above and this was mentioned by a few of companies that were displaying wide-format inkjet printers at the Graphics Canada 2011 trade show.
Wide-format inkjet printing can be used to print vehicle wraps, outdoor signage and banners etc. It is no problem to print unique, one-off products with a wide-format inkjet printer. Wide-format inkjet printing is and will be a part of the future of the printing industry.