by Mike Richards, TWN Industries, Inc.
Water Transfer Printing Technology
You’ve heard it by many names: hydrographic printing, 3D printing, fluid imaging, immersion printing, or simply water transfer printing. Whatever the name, the processes are the same. Using the water transfer printing process, you can transfer high-definition 4-color graphic patterns to many complex three-dimensional shapes. In most cases, you can transfer the film’s inks to steel, aluminum, plastic, wood, and many other substrates. Common patterns are wood grain, carbon fiber, and camouflage. For years, the automotive industry has embraced this technology and process to apply decorative trim throughout vehicle interiors. Early on, the sporting goods industry found that water transfer printing was ideal to apply camouflage patterns to gun stocks and bows.
Today, applications are showing up in many new categories of manufacturing including medical, marine, computer, and general industrial. Some of the more common questions that arise regarding the transfer printing process are addressed below.
Are there licensing fees involved with water transfer printing?
Dating back to issuance of the original process patents, anyone wanting to enter the water transfer processing arena had to pay substantial fees to licensee the technology. Even then, the licenses granted were very restrictive and limiting. This is not the case anymore. The technology finally is available on the free market and available to anyone, with no licensing fees or restrictive agreements.
How does the water transfer printing process work?
Water transfer printing starts with pre-printed high-definition patterns on a water-soluble transfer film. From there, several important steps must be followed to develop a successful print:
Step 1: Preparation. Depending on the substrate, some or all of the following steps may be necessary: chemical pretreatment, fill and sanding, masking, application of spray chemical adhesion promoters, plasma treatment, or corona flame treating.
Step 2: Tooling and Fixtures. Parts are attached to a specific fixture, which holds the parts during the dip process. Generic fixtures can host many different parts but occasionally, engineers have to design custom fixtures to host unique parts.
Step 3: Primer Painting. A coat of primer paint is applied to the part. This paint serves as a bonding agent between the part and the transferred inks. The paint color typically becomes part of the background contrast color as well.
Step 4: Ink Transfer or Dipping. The fixtured part is now dipped through the inks, which are floated on water in a specialized processing tank. As the parts are immersed through the inks into the water, displacement of the water carries the inks around the three-dimensional shape of the part.
Step 5: Wash and Rinse Process. Parts travel through a conveyorized hot water wash line to remove excess processing chemicals. The last stage of the wash line dries the part.
Step 6: QC Inspection. A detailed inspection of the ink transfer and adhesion is completed. On occasion, parts with extremely complex geometry may require manual touch-up using the transfer inks.
Step 7: Sealing Top Coat. Based on the customers specifications, either a high gloss, satin, or flat top coat of clear Urethane finish is applied to seal the inks. One or more coats may be applied and in some cases, buffing and polishing is required between coats.
Step 8: Final QC and Packing. A thorough inspection is conducted by a trained professional. Once complete, the parts then are packed according to the customers specifications and prepared for shipment or final assembly.
How do I get started with water transfer printing?
Several companies exist that can guide you through the processing options. Companies offering water transfer films should offer hundreds of stock or custom patterns and can supply you with the technology, equipment, supplies, and training to decorate components in your facility. Make sure that proper training is included with any decision to purchase water transfer printing equipment. This is very important to develop a consistent and reliable system.
If in-house processing is not your preference, there are many master decorators located throughout the U.S. and around the world that offer this custom decorating process.
Plastics Decorating would like to thank Mike Richards, business development manager for TWN Industries, Inc., for his assistance with this “Ask the Expert” article. For more information, call (913) 449-4879 or e-mail [email protected].