by Jeff Peterson
Decorating an entire surface of a three dimensional part with indentions or curves has always developed a challenge for the designer and the decorator. In today’s decorating marketplace, technologies have emerged that are allowing all types of plastic parts to be decorated completely with patterns or other printed information. In addition, the continued growth of in-mold decorating has contributed to the increase in technology, as have other processes as well.
Although in-mold decorating is not a completely new process, there have been new approaches and innovations that have allowed more and more three-dimensional plastic parts to be decorated in the mold. Kurz Transfer Products IMD process combines the mold and hot stamping technology into a single process developed in the foil manufacturing and design of the parts. It uses specially modified hot stamping foils that are guided through the mold in the open position. During injection of the part, the pressure and heat of the molten material transfer the printed layers from the polyester carrier and bond it to the plastic substrate. A foil feeding and positioning device is used along with specially modified foil with registration marks for positioning of the film. The foil-feeding device is attached to the moveable platen of the injection-molding machine. The hot molten plastic material being injected against the film transfers the printed layers of the IMD film. Unlike insert molds, there is no diecutting or trimming necessary with this process.
IMD foils are specially modified hot stamping foils on a 23 to 75 micron thick polyester carrier film. The thickness of the carrier depends on the decoration depth and geometric shape, the size of the part, the position and the types of gating, and the type of plastic material. Kurz IMD foils are available in a variety of effects, including metallized colors, brushed silvers and golds, wood grains, marble effects, continuous patterns, and more. Even multi-color pictures or images printed in up to 7 to 9 colors are available.
When utilizing this type of IMD process for decorating three-dimensional surfaces, it must not result in excessive elongation of the IMD foil. This can distort the foil and create undesirable results. When designing the surface to be decorated, overstretching of the foil can be prevented making provisions for a sufficiently large radius, chamfers, and a soft transition. The parting line of the decorated part must also be taken into account.
When a plastic part has multiple curves or dips, and the entire part needs to be decorated, spray painting has been the logical answer. Serigraph, Inc. has recently developed a new, multi-layered in-mold decorating technology called Gemini that can replace spray painting for many applications. It is said to decrease decorating costs and eliminate any environmental concerns with spray painting. The desired image or pattern is screen or offset printed on a sheet of clear material, which is then laminated to another sheet or sheets of material. The colors are actually viewed through the clear material, making it virtually scratch resistant.
The color possibilities offered by Gemini are nearly endless, and include popular metallic effects. Coupled with Serigraph’s high-tech forming technologies, Gemini in-mold decorating eliminates the need for spray painting in many applications. The combination of forming, coating, and adhesive sets it apart from other similar processes.
Water Transfer Printing
A process that seems to be continuing to gain momentum for decorating three-dimensional parts is water transfer printing. There are several types of this process on the market currently – all with some variations to them. The Alsa Corporation version of the process is called Hydrographics. The process allows the decorator to take various ink patterns and apply them to a water-soluble roll of film. The pattern is then released on the surface of a tank of water. The part is dipped into the water and the pattern is transferred to the part. This type of decorating allows 3D parts like car dashes, computer housing, phones, electronic parts, etc. to be completely decorated. Every curve and angle is covered with the desired finish. A variety of finishes are available, including everything from wood-grained and high-gloss European looks to marble effects and low gloss lacquers. Even specially designed patterns are available for this type of process.
Fiberlok, located in Fort Collins, CO, has been manufacturing multi-color, electrostatic fiber-coated heat transfers for over 20 years. The company owns several patents on the process that is marketed as Lextra Graphics. Lextra Graphics are currently used in a variety of industries for both decorative and functional purposes, including apparel, automotive, and general industry. It offers a unique combination of precision graphics, fast application, brilliant colors, durability, and a soft textured surface.
Recently, Fiberlok has been involved with a great deal of research and development to apply Lextra Graphics through an in-mold decorating process. Tests were first run by placing a Lextra transfer inside the mold of a plastic coffee cup. The results were very encouraging. Since those initial tests, further research has been conducted and an entirely new technology has been developed (patents pending) called the LextraFilm Transfer. The scope has continued to expand with a common denominator being that it is all created with a fiber coating process combined with injection molding.
Unlike other in-mold decoration, LextraFilm’s primary advantage is its use of fiber coating instead of ink as a media. Rather than ink, high voltage electricity and fibers are used to decorate the part. One of the most innovative applications for LextraFilm to date is referred to as DigitalDenim. It is a scanned and digitized, realistic-looking reproduction of an actual stonewashed denim textile. This denim material can be formed in-mold to create the stunning visual and textural illusion of a denim plastic part. The textile-like surface is made up of individual fibers along with a continuous base film. An example of a functional application for LextraFilm in-mold decoration is its use for computer laptop surfaces where a persons hand would rest. Unlike smooth non-porous plastics, LextraFilm allows the surface to breathe to prevent it from becoming hot or sticky, as well as serving to insulate the users hands from the heat of the computer.
As one can see, there is a great deal happening with full decoration of 3-D curved plastic parts. In many instances, these processes are combined with more conventional decorating methods as well, including pad printing, hot stamping, or screen printing. As the sophistication of in-mold and other processes increases, the plastic part designer and decorator will continue to have more options in the future.
Plastics Decorating would like to thank Roy Bomberger of Kurz Transfer Products (800-333-2306), Michael Terlizzi of Serigraph (800-279-6060), Ike Banoun of The Alsa Corporation (323-581-5200), and Brown Abrams of Fiberlok (970-221-1200) for their contributions to this article.