“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.
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.