by Jeff Peterson
Not long ago, the only real choice for creating a pad printing cliché was to chemically etch a steel plate. However, new innovations and advancements with photopolymer technology and laser-based CTP systems have created more choices for pad printing operations to consider.
Steel clichés for pad printing continue to be the mainstay for very large runs, especially for automotive, medical, or consumer electronic applications. Steel clichés are chemically etched and are available in either 10 mm (3/8″) or 0.5 mm (0.02″) thickness. Thinner plates are used for runs up to 500,000 and the thicker plates are most commonly used for runs over 500,000.
The number one advantage of properly manufactured steel clichés is that they can last as long as one million impressions or more. Again, this can be important for very long runs, where eliminating machine downtime to change out the cliché can make a substantial difference in production efficiency.
The disadvantage of steel clichés is the high cost and extended lead times to manufacture them. Because steel clichés are chemically etched, most are not manufactured in-house and are created by a supplier specializing in this service. In addition, the chemicals create an environmental issue to consider. However, it is important to keep in mind that the most common applications for steel clichés involve very large runs where pre-planning is necessary so lead times and overall costs are not main factors.
Laser-etched Computer-to-plate Systems
Computer-to-plate (CTP) laser systems are the newest technology on the market for creating pad printing clichés. “This technology provides a great advantage for pad printing companies who want to improve efficiencies, reduce plate making time, and standardize the pad printing process,” stated Ben Adner, president of Inkcups Now. “It can be an excellent choice for manufacturing clichés for both short-run and long-run applications.”
Many potential advantages exist when considering a CTP laser system. Because it is computer-to-plate, graphics are first generation, with no loss of resolution – unlike photopolymer or steel clichés where film is first needed to create the image. There are no film, developing, or etching material costs. And, a main advantage is time. Laser-etched clichés can be made in three to five minutes.
The disadvantage of a CTP laser system is the upfront costs involved with setting up the system. A laser etching system can run several times the cost of setting up photopolymer cliché exposure, development, and post-exposure/drying equipment. Another issue to consider is that it is imperative to have a capable operator to laser-etch the clichés. Although the software is not overly difficult to understand, knowledge in the area of computer graphic software is necessary to properly create laser-etched plates. “The key to creating consistent, laser-etched clichés is having proper training and a good operator running the system,” stated Michael Chaney, vice president of Diversified Printing Techniques. “It is important that the supplier of the laser system provides training and service at the time of purchase.”
YAG laser systems were the first generation of CTP laser systems on the market and are more expensive systems. However, one large advantage of a YAG laser system is the potential ability to perform industrial laser marking as well. There are now CO2-based laser plate making systems that have been recently introduced which sell for as little as $10,000 – $25,000. With these new systems, the start-up cost can be much more affordable.
YAG laser technology uses aluminun-based plates while the newer C02 laser plates are made of a steel-backed coated polymer.
When using the YAG laser technology, aluminum-based plates are used. The advantage of the aluminum plates is that they are double-sided, so an image can be etched in both sides of the plate. However, they are non-magnetic, so additional sub-plates are typically used to properly seal the magnetic cup with the plate. The CO2 system plates are a steel-backed coated plate made of a special polymer. This provides the ability for the cliché to work with magnetic ink cups and provides a more durable plate.
A growing trend in pad printing is to utilize photopolymer clichés exclusively instead of metal clichés. “Many of the European pad print machine manufacturers have almost totally gone to using photopolymer clichés,” stated Innovative Marking Systems National Sales Manager John Kaverman. “Cost of manufacturing, environmental ramifications, and overall costs have all contributed to this trend.”
Photopolymer clichés are an excellent choice for short to medium-sized runs – from several hundred to several thousand. The advantage to photopolymer is the relatively low cost and ability to have the clichés produced in-house with a relatively small investment. Quality images can be produced by using a film positive where the image is exposed and developed with a water or alcohol wash. Several types of photopolymer cliché materials exist. There are single exposure materials that are only exposed once, using the image film; and there are double exposure materials that are exposed once with the image film, and a second time with a line screen film. Additionally, there are water wash and alcohol wash clichés, and different levels of quality are available in all the types. The key is to find the right combination of price and quality for the specific application.
Photopolymer clichés can be produced at a relatively low cost with a small investment to manufacture in-house.
The drawback to photopolymer clichés is their overall durability. They are wonderful for short to medium-sized runs, but would not be the best choice for runs of hundreds of thousands or over a million. The other concern with photopolymer clichés is the number of steps involved in producing a plate. The more steps involved, the more opportunity for error and for producing a low quality cliché. As with laser-etched clichés, having the proper training and equipment is essential in producing consistent, quality clichés.
Before choosing the type of cliché for a particular application, contact your supplier and explain the types of work and images you are printing. For example, is the image small with a lot of detail, large with bold areas, or a combination of fine detail and large, bold areas? Also, sending samples of the artwork you are working with is recommended. Finally, discuss with your supplier the run lengths and turnaround times under which you most commonly are working. All of these questions and scenarios can help determine which type of cliché and/or processing equipment is best suited for your operation. In addition, if you are considering manufacturing clichés in-house, either laser-etched or photopolymer, make sure that proper training and service is available from the supplier. This will help ensure quality clichés no matter what process is used.
As technology continues to grow and processes are perfected, what might be the best choice for manufacturing your clichés at present may not be the best choice two years from now. Therefore, it is wise to keep a continual pulse on what is happening with cliché manufacturing – today and in the future.