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Question and Answer

Working with In-line Registered Embossing

by Jeff Peterson

May-June, 2007
Although adding foil stamping in-line on a narrow-web flexo press has continued to grow in popularity, embossing the foil stamped image or embossing a printed image has become an important part of many label and carton designs as well. End-users have realized that embossing can enhance the visibility of a label on the shelf and create movement where the highlighted edges of the embossed label vary as the viewing angle changes. It is this motion that attracts the eye and makes embossed labels so effective on the store shelf.

There are, as with any process, challenges to face and decisions that must be made when working with in-line registered embossing. InsideFinishing called upon experts in the field of manufacturing embossing rolls/dies to answer a few questions on the subject.

What choices do I have when determining the type of embossing rolls/dies for specific applications?
The most common type of die used for embossing is solid, hardened steel tooling. Steel can be photo engraved or CNC milled. As can be imagined, steel tooling is very hard and will last several hundred thousands of impressions or more. It also is impervious to damage, allowing the tooling to be used over and over again.

In addition to steel, embossing die sets also can be made of brass. Although it is not as hard as steel, brass can be less costly and does have sufficient strength for many applications. Brass is easily CNC milled and provides the opportunity to provide detailed, sculptured images into the brass cylinder roll.

The complexity of the image helps determine how the male-female die sets will be produced, whether it is steel or brass. CNC engraved dies provide greater depth and economical high quality, while a photoengraved die delivers exceptionally fine detail and textures.

What steps should be taken to ensure proper registration of the embossing to the foil or printed image?
The first order of business is to make sure the cylinders are manufactured to the right tooth size and that the images have been stepped off correctly. This seems simple, but any variance in this can make registering the embossing male/female dies to the image impossible. In addition, the artwork must be 100 percent to size. The engraver will then take the “flat artwork” and manipulate it to fit correctly on the cylinder for cutting in the round. Most all in-line embossing is done cold, so there is no need to change the size of the image to compensate for heat. When possible, the engraver should receive a 100 percent stepped file to ensure that the software itself does not “round values” differently in a one up file, which could result in a misalignment with the print or foil stamped file.

When beginning the job on press, the operator should align all the print stations with the first row in each station. It is imperative that all of the cylinders are timed correctly so that they meet at exactly the right time at the nip. It is also important to take steps to minimize the stretch in the paper or plastic substrate, which can happen through improper tension settings on the machine.

Some male/female tooling includes a set screw in the gears to advance or retard the rolls if there is any cutting or cracking on the trailing or leading edge of the embossing. It is also recommended to utilize bearers on the press that are ground to the specific thickness of the substrate being embossed to achieve maximum depth and definition without cutting or cracking. The bearers also will help protect the rolls from damage.

Are detailed sculptured embossed images achievable with in-line rotary embossing?
Although sculptured or multi-level embossing has been available for rotary applications for several years, only in more recent years has it become a feasible option for many applications.

Improvements in the speed and simplicity of the 3D software packages that work with the CNC milling equipment have enabled engravers to provide printers with detailed embossed male/female tooling at a fraction of the cost and time of just ten years ago. Technology has allowed engravers to provide the same sculptured detail in a rotary die image that has been available in flat dies for decades.

Detailed sculptured images can be achieved through proper communication. However, the engraver must have some leeway to utilize its experience to create the correct depth and detail of the image.

Foil stamping and embossing in-line has become commonplace on many narrow-web flexographic presses for labels and smaller folding cartons. What was once only utilized for specialized applications or very long runs (foil stamping and embossing in-line) now is being done on all types of jobs and all sizes of runs. A label today can be printed in four colors or more, coated, foil stamped, embossed, and kiss cut in one pass from beginning to end.

InsideFinishing would like to provide a special thanks to Gary Smith of RotoMetrics (636-587-3600 – www.rotometrics.com) for his input on this article. Also, thanks to Peter Spector of Eastern Engraving (908-647-3300 – www.easternengraving.com) and David Polkinghorne of DMS, Inc. (847-726-2828 – www.dmsdies.com) for their assistance.