By Melissa Donovan
Part 2 of 2
Common surface treatments include corona, flame, and plasma. They are primarily used to enhance adhesion of ink, paint, or primer to a low-energy surface—such as plastic. Found in a number of industries from automotive to packaging, their usefulness increases as digital printing technologies present even more types of printable surfaces.
Surface Treatment Equipment
Here we share available surface treatment equipment used in digital printing processes found in manufacturing environments.
Enercon Industries Corporation offers corona, plasma, and flame technology. For digital printing on roll-to-roll webs, the company offers a system that produces high-definition corona. This technology provides a uniform and powerful corona treatment across the entire width of the film. Corona treaters integrate with OEM printing equipment for a seamless process. Enercon flame treaters may be used for either roll-to-roll web applications or for treating dimensional objects and sheets. In addition, Enercon offers plasma technologies with unique discharge capabilities for specific applications. Blown arc plasma is ideal for non-conductive surfaces in need of treatment prior to digital printing. Blown ion plasma treaters are effective on both conductive and nonconductive surfaces.
Lectro Engineering Company Inc. designed the Lectro-Treat process of plastic surface treatment, which treats the surface of 3D plastic objects yielding an even, consistent surface treatment to the plastic part. Considered a suppressed spark system, Lectro-Treat equipment consists of a dielectric tunnel that the parts to be surface treated pass though. Plates are situated parallel and covered with perforated polyethylene shield that distributes directional plasma in the air evenly throughout the air gap. The surface of a plastic object passing between the plates is bombarded by positively and negatively charged particles creating a treated surface. While the electrical operating parameters are factory set, the variable is the conveyor speed. This enables optimized surface treatment for each user.
Plasmatreat GmbH offers Openair-Plasma technology, which creates the ideal conditions for UV digital printing with-out the need for additional adhesion promoters—even with water-based inks. The company also developed the Plas-maPlus Print coating process specifically for printing uncoated float glass with water-soluble inks and solvent-free UV ink systems. The functional, transparent nanocoating does not impair the transparency of the glass, but improves the adhesion, scratch resistance, and moisture resistance of UV inks in digital printing.
QC Electronics, Inc. recommends its corona sheet treaters, which provide superior surface treatment. They are available as standalone models in any sheet width or inline on coating, pretreat, and printing lines. Equipment is available for treatment of one- or two-sided sheets. New to the sheet treaters is PLC technology, which allows for easy operation and monitoring of the device. Features include autonomous watt density control, line speed display, controlled motor speed, and touch panel control.
Vetaphone’s corona pretreatment systems standout thanks to monitoring and measurement features. Essential to the success of the corona treatment is the high-frequency electrical discharge that is directed to the surface in question. During the process, an air gap appears between the electrodes and the substrate that is passing underneath. If the gap is too large, the discharge won’t jump the gap and if it is too small, it burns the material. An optimum gap is 1.5 millimeters, however each material treated has a different optimum frequency. When power is supplied by the generator to the transformer and then on to Vetaphone’s corona treating unit, each cycle is measured to ensure the system performs at maximum efficiency. Each transformer is matched to the electrodes supplying the discharge. Vetaphone also offers plasma surface treatment systems.
Working with surface treatment equipment in house enhances adhesion of ink, paint, or primer to surfaces such as glass, plastic, or metal. It is especially beneficial as digital printing technology allows for printing to even more low-surface energy substrates than ever before. An added step—whether corona, flame, or plasma—ensures a durable finished product.
Apr2019, Industrial Print Magazine