by Cassandra Balentine
One niche segment within UV printing is thermoforming. Many industries look to this process including building and construction, automotive/transportation, medical, and signage.
Select UV LED ink sets enable thermoforming. The properties of the inks used in the process are of particular concern, as they require flexibility and the ability to withstand high temperatures.
Ink Feature Sets
Adhesion, flexibility, and durability are among the many features necessary for inks used in manufacturing thermoformed goods.
Phil Jackman, global product manager, digital, Sun Chemical, points out five aspects that manufacturers should look for in terms of UV LED ink sets for thermoforming. The first is a good backing white. “This is important in the case of clear substrates, especially when backlit,” he offers.
Second are highly lightfast pigments, as thermoforming applications are often used outdoors in challenging conditions.
Third is adhesion. “These inks need to have good adhesion to traditionally challenging materials, such as acrylic and polycarbonate,” says Jackman.
He says the fourth is surface resistance, as the inks need to be stackable following printing. “Inks must exhibit the resistance to the heat in the forming process and be stackable after forming during the transportation process.
And finally, the fifth aspect is long-term flexibility, which is needed to ensure the print’s performance over time. Jackman says this is especially true in cases where the temperature is known to fluctuate.
It’s also worth noting the benefits of UV LED curing in thermoforming. “LED cure has advantages over mercury lamps as they run much cooler and therefore do not warp heat-sensitive substrates before they are formed. However, it is important to consider the stretch needs prior to deciding on the best solution. Inks with more than 500 percent elongation are possible, but they tend to be too soft for many surface print applications and therefore are not particularly suitable for applications other than reverse print thermoforming,” explains Jackman.
Ink Sets
There are inks specifically produced for thermoforming as well as those with multiple functions. In any event, UV LED inks that are utilized for thermoforming applications must be able to withstand high temperatures and feature high elasticity.
Jackman says thermoforming with digital print technology is used by manufacturers handling a wide range of product substrates, including vinyl, ABS, acrylic, polyester, polycarbonate, and polypropylene. “UV LED ink sets designed specifically for thermoforming are the mainstay of this segment. No matter the market or customer, the benefit from digital’s relationship with thermoforming is the ability to deliver products and designs quickly and easily, thereby getting the process closer to the consumers. The substrate handling and productivity of the machine are key factors in the choice of hardware.”
There are also multifunctional thermoforming inks. For instance, Jay Roberts, product manager, UV printers, Roland DGA Corporation, says some customers use Roland’s ECO-UV S ink for both thermoforming and graphics printing. “ECO-UV S inks have no gloss functionality, but the businesses using them are typically not creating signage that requires gloss. UV printers make it simple to print onto plastics under the bends and temperatures of thermoforming without great distortion or color shifts, making them ideal for prototyping and short-run production.”
Special Features
The thermoforming process requires substrates and inks to bend and stretch in a controlled, predictable manner.
“Some UV printers have specially formulated ink sets, which allow for both the bending and stretching needed in thermoforming. Roland developed ECO-UVS inks for both packaging and thermoforming. Developed in early 2012, they were first used with the company’s VersaUV LEC series inkjets for printing and cutting applications. The ability to print to thermoforming material was adapted quickly. Thermoform producers took notice of Roland’s ECO-UVS capabilities, employing the functionality of these inks to print onto plastics for thermoforming signs, graphics, and point of purchase (POP) displays. Many of our customers are currently using Roland printers with the ECO-UVS inks for such applications,” shares Roberts.
He says Roland’s ECO-UVS inks can be thermoformed up to 220 degrees. This bending property allows companies to print to thicker plastics and create signs with heavy curves, bends, and bulges without cracking the ink.
“Without this ability to stretch, cracking or elongating can occur, greatly distorting the graphics as well as any text, where it’s even more noticeable,” shares Roberts. “The ability of Roland’s ECO-UVS inks to hold up to heat and accommodate even extreme bends is what makes them so effective for these types of applications.”
Roberts believes that while mass production of thermoform applications remains primarily with screen printing, smaller companies shifted to digital printers, like Roland’s VersaUV series inkjets for their point of purchase and high-quality signage needs. “The ability of these devices to print images, and more importantly, text, onto thermoforming materials with outstanding detail greatly influenced the advertising market. While most of the demand comes from packaging and sign manufacturers, we are also seeing significant demand from advertising agencies exploring new avenues for POP displays and unique signage. Such agencies love to employ different methods and looks for their advertising/promotional materials, so having thermoforming capabilities can be extremely useful for these firms.”
Sun Chemical’s Crystal UVG LED inks are designed to balance the requirements to give the best possible performance in a range of thermoforming applications. They are available through OEM partners.
“The print reliability and excellent drop formation ensures superb print quality in demanding applications on difficult substrates where the adhesion, flexibility, stretch, and scuff resistance are all balanced to provide the enduring performance characteristics required for thermoforming,” notes Jackman.
Thermoforming Inks
Thermoforming is a manufacturing method that utilizes the digital print process to meet evolving demands like customization and short runs. Inks designed for use in these applications must be durable, flexible, and able to withstand high temperatures.
Oct2021, DPS Magazine