Paying attention to the smallest details can make a big difference in the world of flexographic printing. Flat top dots profiles are one minor detail that requires attention (or shapes). It appears simple enough to overlook, but the experienced flexo printing professional understands that the implications of using different image carrier dot profiles can have a significant impact on the quality of the finished prints.
It’s all about the Dot with Flexo Plates
Flexographic printing now rivals both offset and gravure in terms of quality. There are numerous reasons for this, but one important reason is that flexographic printers are now more effectively optimizing their processes with innovations such as flat-top dot plates, UV LED exposure, and screening technology. The proper plate, exposure, and screening combination makes the job easier, more consistent, of higher quality, and ultimately more profitable.
Choosing the Right Plate
There are four major market segments in the flexographic packaging market:
- Tag & label,
- Folding carton,
- And Flexibles.
Each market segment has its own set of challenges that may necessitate the use of various durometer plates. Label printers, for example, have traditionally used a medium durometer plate. This requirement was partly motivated by the need to wrap a very small plate around a very small cylinder, and — here’s the important part — it must remain in place and not lift from the cylinder.
Certainly, the mounting tape helps to keep the plate in place on the cylinder. The softer the plate, however, the more flexibility it requires to properly lay down on the print cylinder and mounting tape. Printing plates for this market segment must also be capable of printing extremely high-quality graphics and printing cleanly over long runs.
MacDermid has designed medium durometer LUX In-The-Plate (ITP) plates with very low tack, eliminating the dust and debris that can be associated with some paper stocks. These plates have a slightly firmer durometer than most medium durometer plates, allowing them to be optimized for wide-web applications while still retaining the flexibility required for smaller print cylinders.
Most printers use harder durometer plates for flexible film printing applications. Although the effective gauge durometer of these plates can be in the low 70s or even higher, they typically start around 60 shore A. Most wide-web printers require a harder plate to ensure the best dot reproduction on their substrates.
Slur or excessive dot gain can occur when a plate is too soft for the application. The LUX ITP 60 was the first inherently flat-top dot product to hit the market, earning the FTA Technical Innovation Award in 2016.
Why Are Flexo Flat Top Dots Profiles Important?
There are two types of dot profiles: flat and round, which affect the final printed product. Many factors influence the selection of a dot profile, including:
- Ink characteristics
- Desired color density
4 Important Considerations When Choosing a Dot Profile for Your Print:
Here are some things to talk about with your image carrier supplier so they can help you decide what’s best for you:
1. Impression levels
Depending on the printing pressure, roundtop dots will produce varying final print results. This can result in significant dot deformation or unpredictable dot gain if you don’t know what’s best for your print.
Because of the rounded contact point, roundtop dots can print a finer, smaller dot and are frequently used for highlighting or detail areas. A flat-top dot has a defined surface, resulting in less variability in dot gain based on pressure and increased benefits for solid, dense ink areas and reverse printing projects, particularly those involving flexible or corrugated substrates.
They also allow more ink to be transferred from the image carrier to the substrate. Even when the dots are close together in dense printing areas, the steep dot shoulders allow for greater image carrier floor depth.
2. Printing results
Roundtop dots are extremely sensitive to pressure changes, which can cause issues in certain print jobs. The color density can change quickly as the printing pressure increases.
Flat top dots are less affected by press pressure, allowing for greater image consistency throughout the press run. The flat-top dots maintain a much crisper edge and a more defined printing surface. They are well-known for their optimal dot structure, which results in improved color control and increased vibrancy.
3. The impact of image carrier stress
Flat-top dots are generally thought to be more durable than rounded dots, which can result in significantly longer image carrier life.
4. Cost considerations
Flat-top dot image carriers provide longer press life and more consistent prints, potentially increasing profitability.
The Future of Dot Profile: Exploring the Evolving Trends and Advancements in Print Quality
Dot technology that is constantly improving will allow flexo printers to expand their printing capabilities into more products that are currently performed by offset or gravure printers. Flexographic printing can be used to print high-end labels, cartons, and flexible packaging. With a solid understanding of key aspects of the flexographic printing process such as ink selection, dot profile, image carrier, and ink transfer, printers have more opportunities than ever before to produce higher-quality images.
Image credit: iStock
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