Industrial + Specialty Printing

This overview describes how hot stamping works and identifies the ways in which it can add value to the printing processes you use and the products you manufacture.

By Ben P. Rosenfield

Industrial-imaging specialists always look for competitive edges in the varied and growing markets they serve. As such, they often rely on a wide range of printing technologies to meet customer demands for quality, durability, and turnaround time. Screen, digital, pad, offset, and flexo printing are important parts of the industrial imager’s arsenal, but opportunities abound to complement these technologies, expand areas of specialty, and create revenue streams.

Hot stamping is such a solution. It enables specialty printers to augment their production capabilities and pursue the kinds of jobs that can differentiate them from their competition. Hot-stamping machines can be used on their own or as parts of other printing workflows, and their functionality depends on three components: dies, foils, and presses. This article examines each, discusses the variables inherent to the process, and depicts a few of the applications that benefit from hot stamping.

Diemaking
Magnesium, brass, hardened steel, copper, and silicone rubber are the most common types of die materials. The content that will appear on the hot-stamped product is either engraved or chemically etched into metal die blanks. Diemakers who work with magnesium and copper apply a photosensitive coating to the metal plate’s surface. Emulsion that remains after the metal plate is developed acts as an acid-resistant barrier. The plates are then bathed in nitric acid and water (other additives may be used when etching copper plates).

The photoetching process is aggressive, which is why diemakers pay close attention to obtain the desired results. Diemakers can control a magnesium plate’s etch depth, shoulder slope, and other characteristics by changing the chemical bath’s temperature, compensating for bath age (the number of plates already bathed in the chemicals, and the amount of metallic residue from previous etchings), and controlling the speed of the paddles in the etching chamber. These paddles essentially lift etching chemicals and throw them onto the metal plates. Copper is treated in much the same way, but its etch depth and shoulder slope are controlled primarily by bath chemistry and the additives that are put into it.