Hot stamping foil
What is hot stamping?
Hot stamping is a lithography printing process that uses heated image molds or stamping dies to transfer metal foils or pre-dried inks onto a surface.
Typically, the process works as follows: the hot stamping machine heats an engraved mold or die, which then presses marking foil onto the surface. The foil is deposited only where the hot stamp comes in contact with the product material, allowing engineers to create elegant, embossed designs on parts and assemblies in post-production. Hot stamping foils have three layers: a color layer (which can be pigment or metallic), an adherence base, and a release layer. Innovations in digital printing even enable hot stamping three-dimensional images with holographic foil.
Hot stamping is a versatile, precise, and efficient method for printing on surfaces, and is often used to personalize or decorate products. Here’s a quick rundown on some of the key benefits of the hot stamping process, as well as key considerations to keep in mind.
Four key benefits of hot stamping
One of the most significant advantages of hot stamping is that it can be used to treat a wide range of common product materials — including plastics, rubbers, and metals — in addition to more specialized materials like wood, leather, and glass. Hot stamping foil can even be applied to coated objects without damaging the coating. As such, it can be effectively applied to parts ranging from pencils and book bindings to cosmetic packaging and cable ties.
BENEFIT #1
Hot stamping is also a clean and incredibly effective process. Because hot foil stamping machines work with rolls of metal foil or pre-dried inks, engineers can avoid mixing liquid inks and cleaning up messy spills.
BENEFIT #2
Hot stamping also consistently produces high-quality results — regardless of the pigment or metallic coloration of the foil, adherence bases are created to have a strong grip on product surfaces. However, some materials — such as leather — require specialty foils in order to properly adhere, which is important for product managers to keep in mind.
BENEFIT #3
While marking foils are designed to be durable, environmental conditions can cause them to fade over time. In instances when a metal die is pressed into plastic or wood parts, the die can actually brand the material, ensuring that a mark remains even if the foil wears away.
BENEFIT #4
Though primarily used as a finishing process, the hot stamping method has other applications, as well. For instance, in automotive manufacturing, hot stamping can be used to maximize steel malleability. The process is similar to warm forming; however, the dies are cold when pressed into the heated steel, which creates Martensite microstructures in the steel that give the part exceptional strength. This makes hot stamping useful in the production of strong vehicle cabins and safety cages, among other parts.
Hot stamping limitations and considerations
The one significant limitation of the hot stamping foil manufacturing process is that it does not allow for printing extremely small letters without losing definition. Otherwise, so long as the design can be made into a mold or die, it can generally be used to transfer stamping foil without issue. If high-definition small lettering is required, pad printing or screen printing may be more suitable options.
Another key consideration is the choice of material for the die that presses the stamping foil. Metals like brass, copper, magnesium, and steel are commonly used. Magnesium dies are easiest and least expensive to make but are less durable. Copper and brass offer greater durability and require greater costs to produce, while hardened steel dies are virtually indestructible and provide the best foil transfers. Steel dies are expensive to produce, but due to their durability, become incredibly cost-effective when used in high-volume production runs.
Hot stamping products that feature complex shapes or surfaces that aren’t perfectly flat presents a challenge. However, manufacturers often overcome this hurdle by using silicone-based stamping dies. Because they are inherently softer than metal stamps, silicone dies conform better to irregular surfaces or shapes, which enables more precise transfers.
Structure of the metallic hot stamping foil
The hot stamping foil is composed of few laminated layers with specific funcionalities :
Polyester foil is the carrier of the decorating element, this layer remains as waste after the printing process
Release layer : this layer is a fuse to separate the printind layers from the carrier
Protective varnish : this layer protect the decoration onto the object for both mechanical and chemical agression
Replicate layer : optional (usually for pre-printer transfer foil) or added functionality
Metallization layer : made from vacum metalizing equipment (give the metallic aspect fo the decoration)
Adhesive layer : This layer is commonly called the glue, this is the layer defining on which kind of substrates the foil can be used.
IMPORTANT :
Note that only the carrier foil (polyester) is remaining on the machine after the printing
The release layer is melted
The remaining layers stay on the printed project, the glue being chemically sealed with the plastic.
