“Cutting” might be a misleading word. Melting is actually more accurate. In order to melt the face of pressure-sensitive vinyls, thermal dies use a combination of three factors: heat, dwell time, and pressure. However, thermal dies just “kiss” the vinyl, leaving the paper liner, or carrier, intact. Please see Diagram #1.
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Of course, different combinations of heat, dwell, and pressure are necessary for crisp, sharp “cutting” of the various types of vinyls. With regards to heat, it is always best to start with lower temperatures, and work your way up gradually. For four-mil vinyl, your press temperature should be set at 275°F, and then gradually increased until a clean cut is achieved. Special attention has to be given when using layered screen printing and UV coatings. Higher temperatures are needed for reflective and screen-printed materials, ranging as high as 350°F.
Dwell times will vary according to the material and heat that you are using. One-half to two seconds is the norm for dwell time. Some people cut their dwell time down by using higher temperatures, using past experience as their guide.
The final factor, pressure, is greatly affected by the configuration of your die. Intricate details require relatively more pressure than large, open areas. Also, you may want to adjust the type of counter board underlay that is used depending on the image being cut. Commonly used counter board underlays are posterboard, chipboard, and polyurethane.
Keeping these three factors — heat, dwell, and pressure — in check will reduce the build-up of melted vinyl on the shoulders of your die, and give you a more stress-free cutting experience. It’s important to remember that it is the combination of these three factors that allows thermal dies to melt or “kiss-cut” vinyls.
Profile of a Good Thermal Kiss-Cut Die
Magnesium thermal dies are typically produced in two thicknesses. The most commonly used thickness for four-poster presses is 11 point (.153″). Then there is 18 point (.250″), typically used on clamshell presses. The size of thermal dies is only limited by your press size. Using our oversize die etching machine, OWOSSO can etch cutting images ranging from a single square inch to 10 feet long by 30 inches wide.
Obviously, the goal of using a thermal die is to precisely cut your customer’s artwork. It’s vital in matching this artwork to remember that heat (the thermal part of your die) expands all metals–including magnesium.
Magnesium expands approximately .25% at 290°F and .5% at 350°F. Higher temperatures will cause greater expansion. The Heat Expansion formula in Diagram #2 will help you, especially with critical registration.
If your job requires close registration, run a sample under actual conditions so that printing can be matched to the impression of the die registration. You can use carbon paper between the die and the counterboard underlay to create an impression of the expanded die.
Photoengraving demands craftsmanship. After the image is developed onto highly polished magnesium, every fine detail, every inch, must be inspected for broken lines, pinholes, or missing details. The magnesium is then etched in acid baths. Diluted nitric acid containing solvents and water is splashed against the image surface of the magnesium, etching away everything except the desired line image. The process has to be monitored for constantly changing acid concentrations, temperatures, and humidity, which all fluctuate depending on the amount of open areas of the image being etched.
All these factors influence the depth, shoulder angle, and cutting-edge width of a thermal die; whether it’s a steep, sharp shoulder or sloping and wide.
The cutting edge for 2 mil to 4 mil vinyl should have a surface of .002″ to .004″, depending on the boldness of the image, or if imprinted vinyl is being used. The regular etching depth is between .060″-.075″ for basic cutting needs. More depth can be achieved for special cutting requirements. Please note that only the first .010-.012 inches will actually do the cutting of your vinyl. The remainder of the die’s depth will help prevent scorching of your substrate and build up of melted vinyls. It will also help avoid slow downs in cutting speed, and will keep the vinyl away from the heated die.
We can help you get the best results if we know what you’re cutting. We can etch the dies deeper, or with steeper shoulders if necessary. Some examples of materials needing special attention are: preprinted, UV coated, static cling, and reflective vinyl.
Magnesium expands approximately .25% at 290°F and .5% at 350°F. Higher temperatures will cause greater expansion.
Cutting With Your Hot Kiss
Properly mounted dies on a well-maintained press hardly require make-ready since the surface of the die is of even height. An even counter board underlay, such as poster board, chip board or polyurethane will help in cutting, and it will also protect the edges of the die from dulling or smashing.
To prevent the melted vinyl from sticking and building up on die shoulders, use a release agent such as OWOSSO Release coating. This is an advanced Teflon-like release coating, which has better releasing properties than older spray-on types. Release coatings are most helpful on fine detail and difficult jobs. Even with the newer release agents you need to keep your heat settings in check. Too much heat will result in burned material, raised ridges on part edges, and, in some cases, cut parts that get heat-welded to their backing sheets.
By now you’re probably wondering how many cutting impressions are possible with magnesium dies. Just as for steel rule dies, the material substrate and temperature being used contribute to the longevity of a die. For reflective vinyl with beads, a die might only last for 300 to 500 strikes. Contrast this with a report we’ve received from Houston about a company getting over a million impressions, on 2-mil vinyl — and they’re still using that same die. Trust us, this isn’t just another tall tale from Texas!
Putting bearers around the die can prevent damage from too much pressure. When dies are mounted, they should be centered on the press plate as much as possible, so that even pressure is applied. If a die design has images that are lop-sided, off to one side, this creates an unbalanced load on the press. For more uniform cutting, place pressure bearers on the open side to compensate.
Please give OWOSSO a call when you are cutting unusual printed material or materials with heavy UV coatings. We can point out where you may experience trouble, and it will help you get a clean, sharp cut.
Thermal Die Maintenance
When finished cutting, it is best to remove the die from the press while it is still hot, gently prying it off (the hotter the die is, the easier it will come off). Take care not to let it fall face down. Before the die cools, use a natural-fiber brush to scrub off any residues. We recommend a tampico fiber brush, which can be found at most hardware stores. Dies are easier to clean while still at cutting temperature. To avoid magnesium corrosion, coat your die with an oil such as Pam™ cooking spray. Of course, this prevention is not necessary if your dies are already coated with OWOSSO Release Coating. Dies last longer when stored in a low-moisture, chemical-free atmosphere.
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Here are just a few more tips to remember: Magnesium is a soft metal; it is almost impossible to repair. A good method for storing thermal dies is to drill a hole at one end for hanging. Hanging your dies avoids warping, but you can just as effectively stack your dies by taping a protective sheet of chipboard over the face of the die. The die will stay straight and not be damaged when stacked. Although the cutting edges are not sharp, they need to be protected.
So Go Get a Hot Kiss!
Following these general guidelines will help make kiss-cutting a joy, rather than a job. Don’t forget OWOSSO is always available for troubleshooting and free estimates. Vinyl manufacturers are also a great source for questions. And remember — there’s nothing like a “hot kiss!”
Several important factors combine to determine the choice between brass, magnesium and copper for creating the best results with your foil stamping, embossing, and debossing dies. No single factor should be used alone to make the decision. Since all of the factors listed below interact with one another, their cumulative effect should be considered. Experience will help you make the best material choice, and your printer, press operator, and photoengraver can all provide valuable assistance.
Choosing magnesium, when appropriate, can yield cost savings for your customer and speed up turn-around, without sacrificing quality.
Brass dies are hand sculpted and machined therefore making them the most expensive of the three metal choices. Brass dies are the most durable and since they can be repaired, the life of the die is almost endless. Interpretation of the artwork is only possible with brass dies, including shapes, textures and edges.
Copper is a relatively harder metal used for the same applications as magnesium dies. If your job requires a more durable metal, copper is the best selection. Please consider the following:
Surface Area of Pressure
The amount of pressure required to achieve the best results depends on the size of the surface area being foil stamped, embossed or debossed. Equal foil stamping, embossing and debossing results for a one-inch square surface area require less pressure than that needed for five square inches. Depending on the other factors involved, magnesium is best used on smaller areas with smoother papers while copper is beneficial for larger areas, more heavily textured papers, and extremely long runs. Brass is generally used for combination foil and embossing dies.
Artwork Designs
Durability of your foil stamping, embossing and debossing dies under pressure should suit your artwork design. Relatively more pressure is needed for the best results in bold and uniformly spaced designs. For example, a solid square requires more pressure than an outlined square of the same size. Fine detail and unevenly distributed artwork designs require relatively less pressure and can be readily achieved with magnesium. However, bold and evenly spaced artwork to be printed in long runs may require pressure that copper can withstand best.
Length of Press Run
Generally longer press runs can cause erosion on magnesium foil stamping, embossing and debossing dies. For this reason, copper dies are recommended for long runs. However this is a relative guideline since many factors determine what is even considered a long run. For example, heat is a factor that can reduce the durability of metal. Magnesium has achieved runs in the upper tens of thousands. If you are using high heat and have a long run with your foil stamping, embossing and debossing, brass or copper might be better choices.
Substrates
Is your paper stock recycled, heavily textured, coated, or uncoated? Generally, the tougher the paper stock, the more durable the metal for your die should be. Smoother paper stocks don’t wear as much on your foil stamping, embossing and debossing dies, and magnesium can yield excellent results. Copper dies may be worth the extra cost when using heavily textured papers and for longer runs.
Handling & Maintenance
Press tolerances should be checked periodically. When adjusted accordingly, you can considerably increase the life of your foil stamping, embossing and debossing dies. Also, be careful in make-ready. Scratching and dents can be avoided with just a little attention. With proper handling in all of these areas, you will get more from your die. A good way to store your magnesium dies is to first coat them with a little cooking spray or oil such as Pam.™ When stored and handled properly you may find you are using magnesium again and again.
You’ll offer your customers the best cost, speed, and quality, when you balance all of the above factors. Paper houses have sample departments – use them to test your dies on different stock. Artwork designers should also consult with printers and finishers concerning stock choices and designs. When printers and finishers know ahead of time what they will be working with, it is much easier for them to evaluate the best metal for your foil stamping, embossing or debossing job.
Experienced Craftsmanship
OWOSSO welcomes any technical questions or inquiries. Just fax (989-723-) or your job specifics including artwork design, length of run, paper stock, and temperature and we can help!
Since , OWOSSO continues to set the industry standard for both craftsmanship and service. Our experienced staff has a thorough knowledge of the substrates, the die-making process, and the best production techniques that produce the highest quality dies.
Facing Floody Print
Finishers repeatedly face the challenge of producing a clean print without flooding (foil fill-in). The following suggestions could help solve this re-occurring problem.
Make-Ready
The correct make-ready preparation is a key step to your foil success. When stamping small type or an intricate design, hard make-ready board like epoxy glass board or phenolic board seems to work best. The result will be a crisp stamp without punch on the back side of the sheet.
Proper Foil
Make certain that you are using the proper foil. Foil is manufactured with different releases and adhesives for particular paper stock and applications. Working closely with your foil supplier will assure that you will find the best foil for fine-line stamping. Source-FSEA
Test It Out!
When stamping your foil to the substrates, make sure your foil adheres and bonds well. Here’s a simple test for adhesion: Put medium tack masking tape over the imprinted area, remove with a rapid jerking motion. If no pigment is visible on the tape, you have a good strong transfer and bond. Another test would be to moisten a cloth with rubbing alcohol, wipe the area back and forth at least five times without removing any pigment.
Smudge-Proofing
Often jobs may require stamping a solid panel of white foil on a dark background, e.g. duplex. Problems can arise if customers type on the white foil panel. Invariably, no matter what foil is used the typed letters will smudge or rub off. To overcome this, use a fine screened die for a white panel. This gives the same appearance as a solid panel and the smudging is eliminated. — Source FSEA
Trapped Gas
When foil stamping, gas can build up between the foil and the paper. If your image has many solid areas, the gas can get trapped and cause bubbles. To avoid this, we can use a fine screen that will not be noticeable, but will allow the gases to escape. If you think your job might require this, you can us your file and we’ll discuss your project.
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