By Jeff Peterson, editor-in-chief, Plastics Decorating

Choosing the correct ink and pad for a particular pad printing application is the first step in job preparation. What sometimes can be overlooked are the other consumables and components that must be analyzed carefully before beginning a new job. Plastics Decorating spoke with Brad Parker, vice president of Operations for AutoTran, Inc. (www.autotran.net), who provided direction for selecting the correct consumables and components for each pad printing application.

What are the different types of pad printing clichés (plates), and what are the advantages of each?
Multiple types of pad printing clichés (plates) are available in the market today, including laser, polymerplastic and steel.

The most recent addition to the print plate market, and the most frequently used, is laser plates. There are laser plates made for both CO2 and fiber lasers, so choosing the correct material is critical based on which laser is on hand. There are many advantages to using a laser print plate over polymer and steel plates, but the most important would be the accuracy, consistency, repeatability, speed and cost of the plates.

Using lasers removes human error in the etching process. Lasers provide an accurate location of the etch on the print plate, which helps with setup time on the machine, not only for single-color print applications but also for multi-color pad printing.

To have artwork digitally registered color-to-color, it allows for limited adjustments when setting up a print job once the ink and plate are on the machine. This can be a significant cost savings in the labor time required to set up each print job.

The consistency of not only the location of the etch but also the uniform depth helps eliminate poorly or inconsistently etched print plates and increases the quality of the print on the end product. This relates to repeatability as well, where the etched print plates can be set to each operator’s preferred settings and repeated from job to job without variations in print quality. This eliminates a variable in the process, which is the major barrier in pad printing.

Speed also is a significant factor in converting to the laser etching process. While CO2 plates take longer to etch than fiber, it is a considerable time savings to etch a print plate vs. the polymer and steel options. A standard 2 inch x 2 inch etched plate may take close to two minutes with a CO2 laser and 30 seconds with a fiber print plate. With polymer and steel, it usually will take closer to 30 to 40 minutes to produce an etched print plate.

Finally, cost savings can be significant when comparing laser vs. polymer and steel plates. When pairing labor costs, time and higher-quality etched plates, laser plates are the current and future of the pad printing clichés.

Polymer and steel plates also are more durable than typical laser print plates. When printing long-run jobs with upwards of 50,000 impressions or more with the same artwork, one may want to consider using polymer or steel plates. The durability of these options allows for less changeover on the machine, and the plates can be used in situations where machines are dedicated to one product / artwork typically in a manufacturing process. This is an advantage with the polymer or steel printing plates. The polymer and steel print plates usually are thicker than laser plates, which allows for deeper etches for artwork requirements.

What are the advantages of producing clichés in-house?
Advantages include price, time and control. It is more cost-effective to buy blank plates and etch in-house vs. outsourcing the production of the clichés. The upfront cost includes the purchase of the equipment, whether it is a laser or an exposure unit.

Time also is a major factor, as the process usually requires artwork to be sent to the supplier, with an artwork approval created and sent back to the customer and then approved. After that, the supplier typically will get the print plate etched and sent out within a couple of days. The transit time also will need to be factored in before it arrives at the customer’s facility to start printing the job, including shipping costs tiered by transit speed. If there are any mistakes along the way, the process can start all over again, further delaying the start of the printing process. The lead time of outsourcing the print etching process can be anywhere from five to 10 days or more, from first contact to receiving the plate at the print facility.

Finally, control is critical in the process. Having control of the job’s turnaround time is important for keeping satisfied customers. Having the flexibility to change etch depths and settings also can be important. Having control in the process and being able to produce etched plates in-house can save time and money, while allowing the flexibility to cater to the customers’ needs and requests.

What are the key differences between a closed ink cup and an open ink cup system? Why choose one over the other?
The closed ink cup system is an upgraded version of the open ink cup system. An open ink cup system utilizes doctor blades that scrape the ink back and forth, allowing the printing process to occur. The disadvantage of this system is that the ink is out in the open and constantly is inhaled by the operator. The enclosed cup system mitigates this by trapping the odor within the cup, preventing it from affecting the operator.

Also, the closed cup system provides an advantage due to its doctoring abilities on the print plate. Closed cup systems have magnets that work with the steel backing on the print plate to keep it air-tight. The ceramic or steel rings enable clean doctoring of the ink, allowing ink to remain only in the engraved portion of the plate where the artwork is etched, so it can be picked up and transferred onto the product. The doctor blades can be more difficult to work with than the ink cups.

Tooling also is important when producing consistent printed parts. What tips help create quality tooling (nests)?
Tooling is essential to achieving repeatability and consistency with quality prints. Tooling can be made of a host of different materials, but it is recommended that the tooling be non-solvent-sensitive so that the components of the inks and additives do not have any affect on the tooling, such as melting.A good fit can be achieved in many ways. 3D printing has been used to recreate the cavity to match difficult-shaped products. By having a 3D drawing of the product, the cavity can be reproduced to match up accurately with the product for proper nesting. In earlier days, everything from wood to car bondo was used to achieve the same result, but it required a little more effort to create a quality tool.

What recommendations are there for maintaining auxiliary equipment involved in the pad printing process?
Additional components and supplies for etching equipment are critical to helping the lifecycle of the equipment and producing the highest-quality, consistent etch for a quality print. With laser systems, a good exhaust and vacuum system is crucial for removing debris as dust can find its way onto the lens, creating weak points in the etch. Frequently cleaning the lens of debris also is recommended to allow the laser to operate at a high level. It always is recommended to review the status of the lens from time to time to make sure it has no imperfections or scratches, which can affect etching quality.

Components and supplies for the exposure unit process for polymer plates are important as well, including the frequent replacement of bulbs to assist in consistent etching. Bulb strength can decline over time and increase the amount of time a plate has to harden.Also, utilization of a heating pad underneath the bath of solution, whether it be denatured alcohol or water (depending on the print plate chosen), is paramount to the process. Using a warm solution helps etch and process the print plate faster, and neutralizing the temperature is key. When the elements change from season to season, using a heating pad underneath the solution can help achieve a more effective temperature to etch print plates.

Finally, change out the film within the exposure unit regularly. Over time, the film can gather marks, dust and other contaminants that will alter the ability to properly etch the print plate.