Hot foil stamping process

Hot stamping and holographic foils are made up of several layers. These include a polyester carrier, a release layer, a number of lacquer, image and metal layers, and an outer adhesive sizing layer. During the hot foil stamping process a heated die forces the foil against the substrate, which is supported by a counterplate or counter cylinder. A combination of this pressure and the activation of the adhesive sizing makes the foil attach itself to the substrate, a process that is aided by the melting of the release layer. The dies used in hot foil stamping are predominantly made from brass and are produced by etching or by engraving using hand work or CNC systems.

A hot foil stamper may be an offline, stand-alone machine, or may be inline with a printing press and/or other units. While mainly sheet-fed, some high speed hot foil stampers are web-fed. Whether sheet or web-fed, sophisticated handling systems are needed to position the substrate and foil between the plate or cylinder that holds the dies and that supplying the counter pressure.

There are three differing operating principles found among foil stamping machines, commonly called flat-flat, round-flat, and round-round.

• Flat-flat foil stamping machines operate on similar principles to those of flat bed die-cutters, with some presses being able to swap between both functions and others being fully dedicated foil stamping presses. In flat-flat foiling, the foiling dies are either attached to a flat honeycomb chase allowing for variable positioning, or in fixed positions on a flat metal plate, for repeat jobs. Whichever type of die carrier is used, the sheet and foil will be brought into position between it and the lower counter plate. This is either completely flat, for flat foiling, or mounted with counterparts to the dies, for embossed foiling. The press then brings the upper and lower elements together, delivering uniform pressure across the entire sheet
• In round-flat hot foil stamping, the flat counterplate is replaced by a rotating cylinder. The die chase moves horizontally in synchronization with this to deliver a narrow linear zone of pressure where the die, foil, substrate, and cylinder meet
• The round-round principle of hot-foil stamping is based on a rotary principle similar to that used by printing presses. Here, the dies are mounted on a cylinder that rotates in synchronization with a counter cylinder. The substrate and foil are brought together between the two in the narrow nip point

Each principle has its advantages:

• Flat-flat hot foil stamping offers ease of set up and readily available tooling.
• Round-flat hot foil stampers are ideal for smaller runs and limited series.
• Foil stamping machines using the round-round principle deliver very high production speeds and allow for the application of extremely fine details next to large solids.