By Melissa Donovan
UV ink formulations continue to evolve. Many vendors offer products that not only work with traditional wide format flatbed devices for graphics printing, but also thermoforming applications. The process of thermoforming involves a plastic sheet placed in a thermoforming device—a vacuum forming heat machine—that stretches and molds to a desired shape when heated.
Thermoforming is used to create signage, but it is gaining popularity in industrial markets like building and construction, automotive/transportation, and medical. Part of this evolution involves some of the newest UV ink sets, which can be used for both traditional and specialty applications. Essentially, these inks are now flexible or stretchy enough to be placed in a thermoforming device after being digitally printed to the plastic sheet. Cracking or distortion is minimized, if not eliminated, ensuring a quality finished product.
The signage industry is no stranger to thermoforming techniques. According to research conducted by analyst firm I.T. Strategies and published in its 2013 report Research on Emerging Print Markets: Thermoform Signage Markets, a sign is sometimes screenprinted before thermoforming, but usually painted or vinyl graphics applied after the process is completed.
While screenprinting inks used in this capacity have been available for quite some time, the ability to eliminate distortion and the high costs associated with this trial-and-error process prohibit many from decorating prior to thermoforming. Decorating after thermoforming also presents its challenges, for example exact replicas of a product are difficult to achieve.
Digital changes this. “If thermoform manufacturers digitally print a sheet with the distortion precisely measured, then vacuum form the sheet, they eliminate the time consuming second step of painting or the application of vinyl graphics. Digital printing also allows for more customization and photographic images, which is not possible with painting,” says the I.T. Strategies report.
Ken Hanulec, VP, inkjet, EFI, provides an example of how inkjet-printed thermoforming saves time. “Using a conventional thermoforming process, it might take seven and a half hours of labor to produce two 13.5×4-foot vacuum formed signs. Using digitally printed thermoforming technology, 34 of the same signs can be produced in the same seven and a half hours,” he explains. This is a reduction of 93 percent in labor costs and a productivity increase of 95 percent. With conventional processes, the same 34 signs would take three and a half weeks to produce, according to Hanulec.
Approximately four years ago, sign makers began testing the ability of UV printers with thermoforming plastics, states Jay Roberts, product manager, UV printers, Roland DGA Corporation. “That’s when it was discovered that these inkjets were capable of printing full-color, high-fidelity images onto plastic to create beautifully formed objects used in signage, advertising, and directional signage,” he continues.
UV ink for digital inkjet technologies offer “improved adhesion, better abrasion and chemical resistance, and superior consistency and reliability. UV curing also conveniently eliminates the need for solvent evaporation or any special layers upon printing substrates and it does not involve volatile organic compound emission,” explains Mario Villanueva, applications project manager, Agfa Graphics.
“The availability of inkjet inks suitable for thermoforming allows for the development of short runs with high quality at affordable prices. These days, it is becoming popular, especially in the Americas, for point of purchase (POP) applications and vending machines, where new effects are achieved,” says Pedro Martinez, CEO, Afford Inks.
According to Josh Hope, senior manager, industrial printing, Mimaki USA, Inc., digital UV ink influences thermoforming by giving users the flexibility to produce short-run and one-off custom designs while maintaining profitability. “This opens up a new niche for advertising that can be versioned and personalized to any market or region. It also enables low-cost prototyping that shows both design and form.”
These characteristics help other industries realize the opportunity. The potential to create digitally printed thermoform pieces in industrial markets is large and could be even bigger than signs and displays, according to I.T. Strategies, especially in regards to parts related to decorative functions—vehicle dashboards or overhead automobile storage.
“The concept of beginning with a sheet of plastic and ending with a thermoformed, three-dimensional printed product is remarkable. As a result, this dynamic partnership between thermoforming and UV inkjet has begun to thrive, and will likely continue trending in a positive direction moving forward. It is also important to acknowledge that thermoforming is not limited to automotive, construction, and decorative retail applications, but it also serves a functional purpose within the food and medical industries as well,” shares Stephen Buchanan, research and development chemist – energy curable inkjet, Kao Collins Inc.
Multi-Purpose Ink Demand
Digital UV ink created for acceptable use in thermoforming applications more often than not can also be utilized for more conventional signage. Many print service providers (PSPs) look for consumables with multi-application usage.
“The demand for a multi-purpose UV ink comes from the emergence of diversified applications that customers are discovering are achievable with UV inkjet printing. Print shops need to be able to exploit different characteristics of their UV inks to produce traditional and non-traditional applications alike,” suggests Villanueva.
Buchanan agrees, citing efficiency as the driving force. “It makes a lot of sense for print providers to prefer multi-purpose UV inks to satisfy their unique customer printing demands when possible.”
Packaging and sign manufacturers are one of the largest groups demanding a multi-purpose ink, based on Roberts’ experience with Roland customers. “However, we are also seeing significant demand from advertising and marketing agencies exploring new avenues for POP and unique signage. Marketing agencies love to employ different methods and unique advertising looks, so having thermoforming capabilities can be useful for these firms.”
For PSPs hesitant to invest in a dual-action ink set, “a multi-purpose UV ink offers print providers the undisputed convenience of confidently taking on both conventional and specialty jobs without changing out the ink. In terms of actual production, the switch over between the two kinds of jobs is seamless and can be done on one printer,” says Villanueva.
“Frequent ink changeovers can be a time consuming process, and within printing, extended periods of downtime cut into profits. Providing multi-purpose ink solutions effectively minimizes downtime through negating the time needed to complete unnecessary ink changeovers,” shares Buchanan.
According to Martinez, “the major benefit comes from the versatility of offering a unique process that renders higher profits. The ink is also ideal for those applications necessitating folding, such as POP and rigid board-based furniture.”
Price shouldn’t be a deterrent. The cost of a UV ink designed for both thermoforming and traditional applications versus one just recommended for conventional graphics projects doesn’t differ greatly, if at all. For example, Mimaki’s thermoforming ink is the same price as its traditional UV ink.
Heather Roden, product marketing manager, Fujifilm North America Corporation, Graphic Systems Division, says that Fujifilm’s thermoforming ink’s price point is also the same as its general purpose ink. The one difference is the additional cost associated to white ink in the thermoforming offering.
Roland’s thermoforming ink is priced closely to the company’s traditional UV ink, according to Roberts. Per cartridge, it costs less than ten percent more than traditional UV ink.
“In general, the cost of UV inks designed for thermoforming applications should be relatively similar to traditional UV inks used only for standard graphics applications. Ultimately, the resulting cost of the final ink product always fluctuates in accordance with the printing application requirements and the respective raw materials used within the ink formulation,” says Buchanan.
Stretch and Release
UV ink contains certain features making it ideal for thermoforming. These include resistance to scratching/cracking, elongation, and substrate adhesion.
During the thermoforming process, according to Villanueva, the ink and plastic are “married” to each other. “Both the ink and plastic endures aggressive forces such as stress, compression, bending, shear, and torsion. The UV ink must withstand all of these forces with no instances of cracking.”
A high elongation factor is necessary. “During the forming process the UV ink becomes thermoplastic, elongates, and finally cools to its original properties. It needs to tolerate the necessary amount of heat for the media to form without any cracking, flaking, or whitening,” shares Roden.
“With any UV ink, adhesion is the key. The substrates range from PETG and acrylics, to CPVC and polycarbonates. Thermoforming inks tend to be somewhat softer before forming, but are very durable after forming due to the heat working as a final curing process,” explains Hope.
At EFI, the company focuses on color pigmentation by “augmenting inks to develop process colors that don’t change under heat and don’t fade or thin when stretched,” shares Hanulec.
Buchanan points out that in traditional graphic arts applications, the final printed product is not exposed to elevated pressures and temperatures, therefore the chemistry of traditional UV ink does not need to withstand these conditions.
“For thermoforming producers, printing to thicker plastics and creating signs with heavy curves, bends, and bulges without cracking the ink is imperative. Without this stretchability, cracking or elongating can greatly distort graphics and text,” advises Roberts.
Thanks to advancements in the chemical composition of UV ink, the characteristics of certain ink sets enable high levels of flexibility and adhesion, making them suitable for thermoforming a digitally printed piece of plastic. This not only opens the door for new ways to create thermoformed signage, but also introduces digital print to industrial markets. Digital technologies continue to be used for new applications, with thermoforming being one of many.
Jan2017, Digital Output