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Question and Answer

Foil and Embossing Engravings

by Staff

November-December, 2011

Selecting and ordering foil stamping and/or embossing engravings may be one of the more routine portions of a job, but there still are many questions that must be answered to make sure everything runs properly. InsideFinishing called upon several experts in the field of engraving to answer commonly asked questions on the subject.

How is a refractive die constructed? Are refractive dies more expensive?
Refractive dies are manufactured with intricate line patterns to impart depth, light and a sense of movement within a design, image or type. This effect is a perfect choice when looking to create a memorable impression and add impact, with minimal cost. Refractive dies are an ideal and cost-effective solution that easily can be incorporated into almost any foil stamping job.

Manufactured most often from copper, refractive dies are typically photoengraved. While other engraved die metals may be suitable, copper offers the best heat conductivity properties for aiding in the transfer of the hot stamping foil. Refractive-engraved dies are typically stamped with a metallic foil to maximize the reflective nature of the linear patterns; however, refractive dies also can be used with blind stamping on a laminated foil board to gain similar reflective features.

Most refractive dies incorporate a stock or standard pattern from the engraver’s library of patterns, but some engravers offer a service to custom design a refractive pattern within a customer’s image. It is recommended to contact your engraver of choice to determine the available patterns and types of refractive dies offered.

Pay close attention to the size of the refractive image. Refractive dies, on average, require about two tons of stamping pressure per square inch of image area, compared to the requirement of one ton of pressure for a standard flat foil stamped image. Ensure that your press has the available tonnage required to efficiently reproduce the refractive effects that are engraved within the die.

Storing dies for job re-runs is more important than ever as companies try to keep costs down. What recommendations are there for cleaning and storing dies to keep them in a quality state and for easy access for job re-runs?
Dies can be scratched or nicked easily, so it is a good idea to store dies in either a large foam envelope or in bubble wrap. The layout or cut sheet from the job, original PO information and a proof of the final also can be kept in this envelope, essentially storing the dies and keeping all of the job information in one place – what a novel thought! If film was used with the job, filing this also is a good idea. The film can be useful when registering the die to print or foil if the job is repeated. In addition, it is always a good idea to make sure you have a die number from the manufacturer in the envelope or file if it is not included on the die. It is much easier for the die manufacturer to help you make new dies, counters or even counter masters from old combination dies if they can reference this number.

In addition, dies should be stored on end (vertical) v. stacking them on top of one another. Some type of filing system, such as a filing cabinet with drawers, is preferred, rather than stacking the dies in a box or on a shelf. The following details outline recommended cleaning storage for each die type.

Copper Dies
Copper dies can be cleaned by using a soft fiber brush on the die face. Acetone is a good cleanser for copper dies as it will remove foil residue from the face of the die. It also works great for removing die mounting tape and other adhesives with little effort. Cleaning the back of the die is very important as it will aid in assuring a good makeready the next time the die is used. Prior to storage, cut a sheet of corrugated or other heavy paper to the same size as the die. Place the paper over the die face and tape it down. This helps to protect the face of the die.

Counters Dies
For embossing/debossing dies that also have a pre-cast counter, it is recommended to re-pin the counters to the dies before storage. Do not simply tape the counter to the die – the die and counter can shift, causing wear on both the die and the counter. The resulting abrasion marks will certainly appear on press if the dies are not properly stored.

Prior to storage, gently clean the face of the counter with alcohol or acetone. Short-term exposure of the counter to acetone will not cause any detrimental effect to the cleaning of the counter. Long-term exposure, however, may cause damage to the counter die. Cured epoxy-based plastics are generally unaffected by the use of acetones.

Brass Dies
Brass dies can be cleaned and prepared for storage in the same manner as copper dies.

Magnesium Dies
A soft bristle fiber brush can be used gently to thoroughly clean a magnesium die, but great care should be taken as magnesium dies are softer than brass or copper. Most any soap or detergent can be used to clean the dies, as long as all of the chemicals are removed from the die and the die is dry when stored. The number one goal is to remove or reduce oxygen to the die, as it contains moisture, which will start the oxidizing process. A light coating of food-grade oil (i.e., PAM cooking spray) will aid in the protection of magnesium dies. The dies should then be packaged in a re-sealable plastic bag. Another option is to place a Silica gel packet or cube in the re-sealable bag with the die. Silica gel is a highly porous silicon dioxide that binds water materials and draws them away from any material.

What applications work best for magnesium dies?
Magnesium is an extremely user-friendly metal and can be used for a variety of applications, including hot stamping, embossing, debossing, letterpress printing, thermal kisscutting, membrane switch overlay embossing, signage, plaques, rubber stamp master, mold masters and more.

Many people think that magnesium has a limited use because of its hardness, and they would be partially correct. Of the three most common metals used in our industry (brass, copper and magnesium), magnesium is the softest. However, magnesium has advantages over the other metals:

  • Magnesium is a cost-effective material for any of the applications mentioned previously.
  • Magnesium dies can be etched, machined or sculpted much faster than copper and brass dies. If you were to hand engrave a brass embossing die, you could hand engrave that same image in magnesium 20-percent faster and get the same results.
  • Magnesium dies can be etched to any depth an application requires, with many being etched .180" deep or deeper. On 3/8" thick magnesium, it is common to etch away a 1/4" and still leave a 1/8" base.
  • Magnesium is durable. Converters have embossed 250,000 aluminum license plates using a male/female die set, CNC machined out of magnesium, with the last impression being as clean as the first.

When is it best to consider a CNC-cut die versus an etched die for flat foil stamping? Are CNC dies more expensive?
If the highest quality and precision are required, there is no other choice than CNC engraving. It offers the following advantages:

  • CNC engraving provides higher definition in the stamping image due to optimization of the engraving relief angle, which is particularly beneficial for fine text.
  • It allows the chance to optimize the image to achieve the required result of the hot stamping. For example, opening small letters to improve chances that the foil will reverse out.
  • There are negligible tolerance variations between multiple-up dies.

Apart from the quality issue, the use of CNC engraved dies considerably reduces the set-up time on press, as all dies are absolutely identical regarding frame size and centered position of the image. All factors considered, this streamlines the production process and increases productivity.

In general, the cost difference is more negligible than ever before. Copper pricing on the world market has risen considerably these last years, more so than brass. And, with today’s technology, CNC mills are running at faster speeds compared to just a few short years ago. These factors naturally reduce CNC milling costs.

A pure comparison of the die price itself is not convincing. It always is important to make a total cost calculation, taking into consideration the life span of the dies, set-up time on press and other productivity comparisons. Only then can you ascertain which choice has the lowest total costs.

InsideFinishing would like to thank h+m USA (888.387.4226, www.hmusadies.com), Metal Magic (866.593.6500, www.metalmagic.com), Owosso Graphic Arts, Inc. (800.444.5552, www.owossogrpahic.com) and Universal Engraving, Inc. (800.221.9059, www.ueigroup.com) for their assistance with this article.