Whether you are installing trailer graphics or doing a full wrap of a car or van, surface preparation involves a three-step process of detergent washing, solvent cleaning and a final wipe down with IPA. Read more
Thermal Die Cutting Tips
In the thermal die cutting process, a magnesium die is heated and pressed against a pressure-sensitive vinyl, such as RTapeVinylefx® films. Aided by the pressure of the die, the heat melts the film. Typically the film shrinks away from the cut line, which makes the process of weeding the unwanted film much easier and faster than when films are computer cut.
In making a thermal magnesium die, a photosensitive metal plate is exposed to light and then chemically etched in an acid bath. After etching is complete, all that remains are the very fine beveled cutting edges of the die.
In making a thermal die a magnesium plate is etched. To “kiss cut” vinyl graphics, the heated die is pressed against the pressure-sensitive vinyl film. To prevent sticking, dies are available with a release coating. Photo courtesy of Earl Mich Co.
Although thermal die cutting is a much slower process than steel rule die cutting, the cost of the tooling is significantly less, especially if the die has many lines of small type and intricate shapes. In many cases, achieving the same fine detail by bending steel cutting blades is either impossible or cost prohibitive.
The thermal die is attached to the bottom of the heated platen using a thermal bonding tape. Photo courtesy of Earl Mich Co.
In thermal die cutting, the two most important variables are heat setting and the dwell time. Heat settings will vary from one type of vinyl to another. A two mil cast vinyl will generally cut at 275°F or 135° C. Calendered vinyl usually requires higher cutting temperature of approximately 300° F or 149°C, which is the same recommended heating setting for Vinylefx® films. The typical temperature for cutting reflective sheeting is about 325° F or 163°C.
Please note that I qualified my statements with the modifiers: generally, typical and usually. These temperature settings should be regarded as starting points, when you are setting up for production. Temperatures and dwell times will vary depending on the die cutting press and the material that you are cutting. Adjusting the temperature and dwell times in many cases is a matter of trial and error.
Careful inspection of the cut vinyl is important not only during the set up stage but also throughout the production run. The press operator should periodically inspect the material that he is cutting to ensure that he is getting the desired results, regardless of what type of material he is cutting. Some printers will spot check their work every twenty to forty sheets. Printed sheets and sheets with intricate copy and designs should be inspected more frequently.
The rule of thumb is that as the thickness of the vinyl increases, so does the require cutting temperatures and dwell times. Here’s another rule. Your settings will vary depending on whether or not the vinyl is printed and clear coated and what type of ink is used.
Dwell is the time that the press is closed. Dwell time can vary greatly depending on your cutting temperature and the composition of the material that you are trying to cut. Dwell times can vary from a half of a second to as long as six seconds. If you are cutting a two mil cast vinyl at a temperature of 275° F, the typical dwell time can be between a half of a second to one second. At 300° F, calendered vinyl will require about a second. At 325° F, reflective sheeting can take two seconds. The dwell time and temperatures for cutting Vinylefx™ films varies from one machine to another. At 300° F, cutting time can be as short as a half of a second. Other machines can require temperatures as high as 325° F for three seconds.
Common sense should be employed when adjusting temperatures and dwell time. For example, if the material starts to burn around the edges, lower the heat or decrease the dwell time.
Vinyl materials can release differently from different liners. Some printers claim that the release from a 90lb. poly-coated liner is tighter than a 78lb. clay coated liner. For that reason, these printers believe that film on a clay liner weeds easier. While some printer swear by clay liners, others swear at it, claiming that the liner curls in humid weather.
Sometimes, when cutting at high temperatures, vinyl films and reflective sheeting can stick to the thermal die. Printed and clear coated films are more likely, to stick to the die than unprinted material. To prevent sticking, dies are available with a release coating.
To prevent damage to dies, try taping a rubber mat on the bottom bed of the press. Using a rubber mat or 20 pt. board will provide some cushioning for the die.
In thermal die cutting, the film shrinks away from the cut line, which makes the process of weeding the unwanted film much easier and faster than when films are computer cut.
Photo courtesy of Earl Mich Co.
Transferring thermal die cut graphics can be problematic. The melting process creates a noticeable lip on the edge of the vinyl, which is referred to as a burled edge. The pressure of the die against the release liner will usually break through the siliconization layer, exposing the fibers of the liner’s paper base. Over time the adhesive of the vinyl flows into the cutline, bonding with the paper fibers.
The burled edge and the adhesive flow into the cutlines can make transferring of the film difficult. To aid transfer of thermal die cut graphics, RTape (www.rtape.com) developed its 4885 heavyweight paper premask. 4885 is a super high tack tape with 20+ oz of adhesion.