Other ink decorating processes, such as offset or flexo, cannot compare with the amount of bright opaque ink laydown that is achievable with screen printing. With screen printing, the tactile feel or the amount of ink wanted on the product can be controlled by increasing or decreasing the mesh count on the screen. In contrast, offset and flexo transfer ink to the product via an etched plate and roller, and have limited ink adjustments as a result.

Has labeling had a direct effect on screen printing as a decorating option?
For some years now, labeling (PS and shrink sleeve) has had its foot on screen printing’s neck, and it didn’t look as if this decorating process would survive. Since the 1990s, labeling has been the method of choice for mass marketed products and bottle blow molders by being faster to apply, more convenient in filling operations and requiring less initial capital outlay for production start-up. However, screen printing has hung in there with smaller production runs and contract decorators, outclassing its label competitors with high-end finishing results. This never-say-die effort, combined with drastic changes in today’s world economies, has led to changes in product production priorities.

Production volumes have gotten smaller, with regional decorating sourcing at a premium as overseas production comes back to US shores. Add in the green environmental movement and the impact of large retailers, such as Wal-Mart, requiring its suppliers to adhere to strict packaging environmental procedures, and packaging manufacturers have been forced to make changes.

Wal-Mart is pushing for sustainable packaging that leaves as little of an environmental impact as possible. Directly printed packaging, such as that found on bottles, jars and tubes, only needs to be formed, printed, filled, boxed and shipped. When labeling a package, a pressure-sensitive label must be created using multiple processes (materials, glue and inks), shipping and handling before it arrives to be placed on the package. Once the label is applied to the package, the majority of the label – its carrier – is wasted, contaminated scrap. Assigning an environmental score for these two decorating methods using Wal-Mart’s packaging requirements leaves screen printing as the hands-down winner. The mighty pendulum is swinging back, with the convenience of labeling losing ground to the more environmentally-friendly process of screen printing.

There are advantages to the decorator as well. Once a product or package has been tooled to be screen printed, additional set-ups can be done in a relatively short amount of time and with little additional expense. Other than inventorying ink and screens, a decorator can print as few (for sampling) or as many (for production) as needed. With labeling, the label inventory must be pre-ordered and, to save on the per piece price of a label, decorators sometimes will order and inventory more labels than needed for a short or small order. This can be very expensive and dangerous. The decorator’s customer may want small changes to the design of the package, making the inventory of labels unusable and creating more scrap.

How has bottle screen printing evolved?
In the early days of bottle screen printing, decorating was done by hand-feeding one bottle to a bottle fixture under a screen frame. The bottle was then pneumatically-driven and printed, and then hand stacked to air dry. Over time, innovation and automation were added to keep up with growing demand. With a chain indexing machine with automatic registration, production speeds climbed from the handfed 15ppm to the automatic screen printer’s 50ppm! This meant that solvent inks also had to improve to keep up with the new speed allowed by automating. Bottles had to dry fast, so decorators utilized drying conveyors and ovens that stretched 10 to 20 feet in length. Fortunately, with major advancement in Ultra Violet (UV) curable inks, the screen printer’s footprint was practically cut in half. Mechanical sorting and feeding of bottles, along with inline pre-treating, helped further the bottle screen printer’s value to the growing container market.

The automatic screen printer itself was a sizeable object. The number of print heads in the screen printing line would determine the length of the machine. Some printing machines were so long that a bridge had to be located in the middle of its 50ft. length. This led to designing the modular screen printer, which allows print heads to be added as needed, while still shortening the equipment’s overall length. This novel design sparked a mini revolution in bottle screen printing. Equipment affordability led to the opening of many small bottle contract decorators, and this lasted to the early 2000s. A decline in popularity followed, as mentioned earlier, with much of US manufacturing going overseas, public trading companies looking to squeeze every penny in profits, and labeling making giant strides with the no-label look. Screen printing popularity started to decline, and the process is just now climbing out.

What technology advancements have been seen in the screen printing process?
After listening to customer’s needs, machine manufactures went to work developing labor and time saving devices to their automatic screen printing lines. These advancements include quick change tooling (tool-less or hand push and twist) and set-up software, which has been an answer to many prayers. Once a job has been entered into the screen printing machine’s PLC, all of the jobs settings are now “saved” for the next production run of that particular job.

These devices upgraded screen printing’s capabilities and throughput. By adding other decorating processes such as labeling, decorators now can have label heads retrofitted over an existing print station to allow screen printing and registered labeling in one pass. Some of today’s container decorating now are being fed via high-speed robots, screen printed, labeled, inspected for print omissions, leak detected and then robotically handled for either packing or quality rejection.

Other leading edge technology currently offered or in development includes:

• production that is controlled completely via computer;
• precision servo-driven machine printing and movement;
• space-saving rotary designs with a machine footprint that is up to 80 percent smaller than older 6-color inline designs;
• energy-efficient UV curing systems, including LED UV that will save decorators between 80 – 90 percent of the cost of running today’s production equipment;
• inexpensive, quick change tooling that shortens average container changeover times by many hours; and
• modular print heads that allow the changing out of screen heads to label head to hot stamping head to offset head to digital inkjet heads.

In addition, by printing directly onto a bottle, the addition of multiple years to the life of breakdown of the plastic bottle can be eliminated. Shrink labels and pressure-sensitive labels print their message on a carrier. This carrier is made of plastic, paper or metal and will need to decompose in addition to the length of time required for the package or product to degrade. In addition to this, pressure-senstive labels are applied with contaminating adhesives and sometimes are multilayered. Direct screen printing has none of these problems, eliminating the many processes, handling, shipping and waste (some toxic) that are associated with making a label.

Tim Berenda serves with OMSO North America’s international sales and marketing department. He has 28 years of experience with decorating machines and systems for the plastics packaging industry, including screen printing, dry offset, flexo, pad printing, digital inkjet, hot stamping, heat transfer and related consumables. Berenda can be reached at 859.282.6676 or more information can be obtained at the OMSO website, www.omso.us.