by Dianna Brodine, Plastics Decorating
Screen printing and dry offset printing are two of the traditional methods of container decorating for the plastics industry. These traditional processes, however, have been updated for today’s market requirements.
FlexApex improves dry offset ink laydown
Apex Machine Company has developed a new printing process – FlexApex – to address common problem areas existent in the marking and decorating of three-dimensional products. The process utilizes modified flexographic printing technologies and UV-cured inks in combination with the dry offset printing process to provide multicolor decoration at higher speeds. This provides the capability of transferring large volumes of ink for the printing of dense artwork and solids. It also can be combined with conventional dry offset printing in one machine, offering additional flexibility.
“The primary advantage of FlexApex over traditional dry offset is the ink laydown and/or the opacity of the print,” explained Bob Coningsby, CEO for Apex. “Via dry offset, you are limited to about one micron of ink and with FlexApex, you can apply up to five or six microns of ink. That provides a heavier laydown and/or a silkscreen-type print quality with multiple colors at very high speeds.”
“The second primary advantage,” he said, “is with regards to print consistency. With offset, an operator is needed in order to control and monitor the ink, but the color head does the work with FlexApex to ensure consistently high print quality.”
Up to six colors can be printed at the same time with this UV-based print technology. Low cost print plates are utilized, and millions of impressions can be realized per plate, which significantly lowers unit costs. Some of the best applications for FlexApex exist in the medical, automotive, cosmetic and packing industries where high speeds, low unit costs and high-quality print are required on dark colored parts, Coningsby explained, while offering that the process is not ideal for small-volume print applications or for parts of an unusual shape.
“FlexApex technology was designed for long-run orders that require high-quality print without the skill of a printer or operator,” he said.
Reproducing photographic images with dry offset at Carey Color
At Carey Color, the goal is to give dry offset printers the ability to reproduce photographic images on plastic. A patented process called Stealth Screening nests ink dots within dots, eliminating overprinting that can lead to contamination. “This process redefines the limits of dry offset print quality,” said Tim Murphy, national sales manager, Carey Color. “Our unique screening enables printers to achieve continuous-tone results even when using coarse line screening by eliminating the wet-trapping of inks.”
In addition, the company’s laser ablated plates contain dots on three planes (3D), which allow the true highlight effect necessary for photographic image reproduction. The plates provide the ability to three-dimensionally control the dot height, shape, surface size, shoulder width and angle, and relief depth of both halftones and text. Taking the highlight dot subsurface controls dot gain while allowing more pressure latitude on press. “We use the same dry offset plate, but we pre-expose the plate to its finished position,” said Murphy. “Then, we use two Co2 lasers to craft every dot on that plate three-dimensionally. That’s what allows us to do the subsurface engraving.”
For container decorators using in-mold labels or shrinksleeves, there are significant cost savings and quality improvements. “We’ve done a lot of testing at our cost, working with printers on projects that range from yogurt containers and stadium cups to 10-color five-gallon buckets,” said Murphy. “This process competes very favorably, and we sometimes can show up to a one-third cost savings.”
When compared with traditional dry offset, the plate costs are a little higher since each dot is crafted to upgrade the image quality. Throughput speeds are the same as in a traditional dry offset process. Murphy acknowledged a bit of a learning curve, but the company provides free training, often going to the customer’s facility to ensure the graphics are set up and produced correctly.
Dubuit’s full servo screen printing machines
Dubuit America has continued to offer the latest technology with its screen printing machines in both semi-automatic and servo-driven formats. “Screen printing is both easy and economical to use,” said Jean-Marc Bourgeon, Dubuit America. “It can print on every type of material for which the shape is developable and drying between each application of color avoids dot gain.”
“Customer demand pushes the development of new machines,” said Bourgeon. “First, there was a change from solvent-based to UV inks for automatic machines, and then the demand for universal machines that could print shapes other than cylindrical. Now, the request is for quick changeovers because of marketing requirements and smaller runs. That makes this the era for servo-driven machines, particularly for high-end cosmetic companies with requirements for decorating complex shapes to not only make the product more attractive, but also more complicated to copy.”
Some customer requirements vary according to location. For instance, explained Bourgeon, screen printed tubes still are very popular in Japan, while promotional items commonly are screen printed in North America.
One piece of equipment that meets the needs of many customers is Dubuit’s 329 – or its larger version, the 972 – a completely servo-driven machine that allows screen printing decoration on any shape, such as cylinders, ovals, polygons and flat. With the flexibility of moving the printing head either across the transverse or longitudinally to fit the form of the bottle, these machines allow the squeegee pressure to be varied during the printing cycle to follow a slightly concave shape. The machine is programmable for the storage of job parameters, a distinction that Bourgeon explained is critical in the equipment purchase decision.
“Customers buy machines to meet the needs of a contract they have or are looking for,” he said. “An important parameter is the cost of manpower. The more expensive labor can be, the more interested a customer will be in purchasing servo-driven machines where all adjustments can be stored for future job runs.”
OMSO adds flexibility to screen printing
The ServoBottle and ServoTube screen printing machines have significantly reduced changeover times for OMSO customers, both in the US and in Europe. Changeovers that previously required two to three operators over a period of up to eight hours now can be accomplished in 30-60 minutes. Much of the shortened time frame comes from job parameters that are memorized by the machine itself. Rather than measuring and inputting job specifications, the ServoBottle and ServoTube machines recall the necessary data.
“With the older technology, operators had to run several bottles through to set the equipment,” said Tim Berenda, continental sales manager, OMSO North America, Inc. “The old technology is more of an art, where the new technology is driven by the computer. Now, a laser camera on the first station scans the bottle as it reaches the station and sets the parameters automatically. For customers who are facing shorter runs, there’s a significant savings in time and scrap.”
In addition, utilizing UV LED curing has several advantages. “With the older technology, we were using mercury vapor, and it had to be hot to cure, which softens or even melts the plastic,” said Berenda. “It also created ozone in the work environment, which meant it had to be piped out of the building. By using UV LED, there are workplace safety improvements, the heat generated is reduced and the chances of the container losing shape integrity are eliminated.”
OMSO’s patented “cure on the fly” technology means each station on the ServoBottle machine has its own UV light, which cures the bottle more quickly and makes for a smaller, more compact machine. It also reduces changeover time by eliminating extra UV stations.
Since not every decorating need can be addressed by one technology, the ServoBottle equipment allows stations to be removed and added as needed. “We can switch out label heads and hot stamping heads or add a pad printing station and a digital station,” explained Berenda. “It slows down the machine, but if the customer wanted to decorate all in one pass, he can do it. Each head is individually controlled by a computer, and it’s all portable.”
While the digital decorating market seems to be getting all the attention, the older technologies have received their own upgrades and still are the best choices for many decorating projects. “The price tag has gone up,” said Berenda, “but customers are realizing in one or two years they can justify the expenditure because they’ve expanded the capabilities of decorating for their customers and reduced the labor time needed for each machine. The new machines also help take some of the art out of decorating, turning it into a more technical process. With skilled labor shortages, it’s important to have processes that accurately can be reproduced by someone without decades of experience.”