Many different ink systems have been developed over the years to optimize the
adhesion, transfer, and print quality for decorating applications on a variety of
substrate materials. Understanding how to best select and utilize the different
components of these systems is a critical part of improving and maintaining the
quality of any pad printing operation. Broadly speaking, these components fall into
three categories: inks, hardeners/catalysts, and thinners.
It is often best to start the process of ink selection by understanding the substrate material and adhesion requirements. While there are some options for effective general purpose pad printing inks, certain substrates require specialized formulations or pre-treatment methods to meet adherence requirements (ex. polypropylene, polyethylene, glass, silicone, TPE and other “soft-touch” materials). Certain industries or locations may also have compliance requirements that
influence what inks can be considered. Decorators that constantly struggle with
adhesion or compliance issues would likely benefit from submitting their material
samples to our ink lab for no-cost evaluation and testing to ensure that the best ink
is being used for the application.
Hardeners and adhesion promoters are added to certain inks at a prescribed
percentage by weight of the ink in the batch. As these catalysts are mixed with the
ink, they react together, and sometimes with the surface, to improve abrasion and
chemical resistance of the printed image. Depending on the ink series being used,
the percentage use can be anywhere between 2%-50%, so it is important to have a
scale available for use in ink mixing and establish a repeatable and documented
process. The use of these solvents will shorten the pot life of the ink as the
chemicals react over a 6-8 hour period, so changeovers may need to be made more
frequently to maintain quality.
Thinners also play an important role in achieving good print quality. These solvents facilitate the transfer of the ink from the plate to the pad and from the pad to the part. Even UV ink systems developed for pad printing still rely on thinners in this way. Most ink series have 3-5 different evaporation speeds of thinner available to help decorators optimize their process depending on their environment (temperature, humidity, etc) and factors related to their equipment setup (closed cup vs open well, multi-color, sideways cup movement, high speed automation, etc). Without the proper speed and amount of thinner it is common for there to be voids, uneven application, or insufficient opacity in the resulting print. As with the other components, it is important to test different mixtures to find the best results.
Improving pad printing starts with selecting the correct ink series for the application
and establishing a documented and repeatable process for ink mixing to maintain
good adhesion, transfer, and print quality over the life of the project.
Diversified Printing Techniques is happy to help figure out what ink works for your product. Contact us by calling the number at the top of the page or by filling out the contact form at the bottom. We will likely request some parts to be sent to our facility and will happily run adhesion tests to figure out an ink system that works for your part.