Selecting a Die for Flexographic Printing

Have you ever stopped and thought about how our industry of converting roll-fed material into product has changed?

Over the last decade, substrates have evolved to include thin films and multi-layered webs. With these changes, tighter registration demands have continued to challenge converters. These changes have tasked the equipment available to be well maintained and necessitated that the cutting die be specifically manufactured to meet the requirements of completing the job.

Production is the key. Maintenance and inspection are essential. Simply put, the quality expectations of converted product require both a well-maintained machine and a quality cutting die—be it rotary or flexible. Following the simple formula guarantees better, faster and smarter printruns.

Overcoming Today’s Challenges

The diecutting challenges of today demand cleaner cutting along with cut depth control, or liner impression quality after material burst, more than ever before.

Solid-engraved cutting dies are still playing an important role in rotary diecut converting. Quality machined dies offer consistent, reliable results. Solid dies also offer deep blades for thicker substrates and offer long life for both controlled depth and metal-to-metal die cutting.

Flexible cutting dies have become a specialized product as well.

Every converter’s goal is constant: be efficient, productive, on time and deliver product that meets or exceeds the need. The quality of the flexible die needs to match expectations in cut, life and inspection. It is important to share these expectations with your supplier’s customer service contacts. They can help you make the right choice for the job.

With rotary converting machine automation and the rise in the developments of digital semi-rotary presses, hiring and training new operators is a challenge with which the entire industry is struggling.

New quick die change features and adjustable anvil offerings, such as the new RotoMetrics Accu-Adjust Anvil, allow for die strike adjustment on the fly. It is easy to use and train on. With all the things going on press-side, the die should be the easy part.

Flexible dies are easy to change (with proper training to minimize damage), and mount and storage is as easy as a coat rack. Pressure can be controlled with the fine-tuned control feature on an adjustable anvil. Changes are immediate and will reduce setup time and training aimed at trying to acquire the “perfect touch” on a pressure screw-on top. Again, the goal is to have the operator up and producing better product smarter and faster, with reduced waste.

All flexible dies are coated and each coating fills a specific need. From simple rust prevention to extended life, it’s important to utilize the best product for the job. Nonstick coatings, like RotoRepel from RotoMetrics, promote less adhesive buildup, reduced stripping issues and unparallel ability to minimize adhesive whip. Given those noted advantages, RotoRepel is now expand­ing into idler rolls and shear slitting blades for ink release and nonstick coatings.

Technology, and the voice and feedback of customers, together identify and develop the best solutions to drive up production, reduce waste and ease the shortage of operators.

Purchasing Points

Purchasing a die is simple. Purchasing the right die may be a little more detailed. Ask:

1. What are you cutting?
2. What is the length of run or possibility of the repeat total?
3. What is the liner strike expectation?

The answers to these questions will help lead you to the right die for the job. It’s simple: Don’t buy more or less than what you need. Some suppliers offer a price quote calculator on their website—like the one found at myroto.com—and will ask guiding questions to lead to the best die for the job. It is easy and worth the time. Receive simple quotes in only minutes from your estimator’s desk. Time is money, right?

While these questions seem simple, they are important. What you are cutting leads to blade angle and profile. Quality flexible cutting dies should be machine-finished to exact standards of controlling blade angle on both sides of the cavity.

All materials have slightly different burst strengths required to cut. Intentionally manufacturing a cutting die to force this burst to happen cleanly, while controlling depth of liner impression, can ensure faster speeds and reduced waste.

As face stocks change, the carrier liner plays a larger role in the process. Blade profile plays a significant role in the burst quality of each combination. This combination of specifications built for the application ensures the best quality.

One die does not fit all, so be sure to communicate what you are cutting. If a cutting die is not specific to the material, any changes or variances will affect cut quality and die life. At times, an adjustable anvil may get you through the job—They are an effective tool in controlling variables in material thickness.

Care & Maintenance

Flexible cutting dies require a magnetic cylinder to mount. Care and maintenance on your cylinder inventory are very important:

• Dies are made to an exact blade height to ensure clean cuts of face stocks and adhesives
• Magnetic cylinders are made to the same high standards

It is important to know and understand how the TBH (total blade height) built into the flexible die and the “diff” or “drop” in your cylinder work together to create clearance for the diecut depth.

Monitor your inventory for wear and surface condition. Each should be measured and inspected yearly. The ability to plan and identify which cylinder you will be running die on ensures the best results.