Hot stamping and embossing are dry processes. They’re used to create decorative layers on many different materials. A metal tool presses the surface, leaving a negative image with foil or creating raised and recessed patterns.
| Processing Cost | Typical Application | Suitability |
| * Low mold cost * Low unit cost | * Consumer electronics * Packaging * Office supplies and printed materials | * Small- to large-batch production |
| Quality | Related Processes | Cycle Time |
| * High-quality, repeatable fine details | * Pad printing * Screen printing * Spot varnishing | * Short cycle, about 1000 cycles per hour |
Process Introduction
Hot stamping, also known as foil stamping, thermal printing, and gold stamping, is a pressing operation. It’s often used together with embossing.
A precisely made metal tool presses foil or embossed patterns onto the surface of materials. This is a quick and repeatable process, widely used in the packaging and printing industries for both small-batch and large-scale production.
Since the dies used in hot stamping and embossing are very similar, sometimes they are combined into one operation. However, surfaces with high-quality requirements need separate operations. Hot stamping uses square-edged dies on the material surface. To get the best results, embossing dies have a small radius and are pressed from the opposite direction into matching dies.
Typical Applications
The printing industry uses these processes a lot to decorate book covers, packaging, invitations, flyers, posters, CD cases, and company stationery.
Foil can be hot-stamped onto materials like paper, wood, plastic, and leather. It’s used to print logos and text directly on stationery and cosmetic packaging. Holographic hot – stamping foils are used for items that need security features, such as bank cards, driver’s licenses, concert tickets, and gift vouchers.
In in-mold decoration, hot stamping is used to print on films, mainly for consumer electronics.
Rotary hot stamping (continuous hot stamping) can apply imitation wood-grain surfaces to plastic building decorations. In this area, it overlaps with pad printing. Hot stamping isn’t usually suitable for uneven surfaces, but pad printing, which uses a semi-rigid silicone pad, solves this problem.
Related Processes
Hot stamping and embossing are effective and affordable processes. Other printing methods, except for spot varnishing, are limited to flat colors.
Spot varnishing is a coating technique used to decorate printed surfaces. It’s related to hot stamping but isn’t as opaque as foil. Its job is to enhance the colors on the material beneath it. It’s often used on printed materials to highlight logos, headings, and other design details. Spot varnishing is usually done by screen printing or digital printing, and the varnish cures instantly under UV light.
Transparent foils have been developed that can match the effect of spot varnishing. Using foil and the material in the same color can create a similar look, giving the impression of spot varnishing, like printing bright red on dark red.
Processing Quality
If the process is set up correctly and the machine is reliable, metal tools can create precise and repeatable impressions during long-term production. When using other printing methods, different colors don’t overlap. The advantage of foil is that it’s opaque, so aligning colors isn’t usually as crucial. Still, metal tools can be adjusted to meet precise requirements.
Hot stamping creates a slight indentation on the material surface by applying pressure. This is an aesthetic advantage and helps protect the foil from wear. The depth of the indentation depends on the hardness of the material. For thin materials, pressing can cause a bulge on the back, which isn’t ideal.
Design Opportunities
There are many types of foil, such as matte foil, high-gloss foil, metallic foil, holographic foil, patterned foil, and transparent foil. It also offers a wide range of colors, including those from the Pantone and RAL color systems. Foil can add value, like using gold foil to highlight design details or print fonts.
You can directly layer foils of different colors. That’s why multicolor designs often use solid colors on top of each other to avoid color-alignment problems.
Foil bonds well with most materials. For hot stamping, you don’t need to worry about the material’s thickness, as long as it can pass through the machine.
Hot stamping and embossing can be done at the same time. Although it’s not always the best choice, it can cut down processing time and costs.
Top left
This magnesium sheet is used for embossing thin sheet materials.
Top right
Embossing is used to create fine effects on printed surfaces. When it is used on non-printed materials, it is called “blind embossing.”
Middle left
This 6pt font is photochemically processed into the surface of the hot-stamped magnesium sheet. Laser-engraved copper is best suited for high-volume production and fine detail
Middle right
Hot stamping can reproduce fine lines as fine as 0.25 mm in multiple colors.
Hot stamping is not limited to flat parts; cylindrical cosmetic packaging is also often decorated in this way to increase added value.
Design Considerations
Hot stamping and embossing can handle very complex designs. But not all types of foil are good for printing fine details. There are many silver and gold foils, and some can print fonts as small as 1.5 mm high. Other colors like black, white, or red aren’t as suitable for such detailed printing. Printers should test if small-scale designs are possible.
Bold fonts are hard to hot-stamp because the spaces between letters are smaller than normal. Halftone graphics (light-colored) are also difficult due to varying dot sizes.
Hot stamping works only on flat and cylindrical surfaces. Flat-surface hot stamping is the most common and cheapest. Cylindrical hot stamping needs more specialized tools, costs more, and is usually used for large-scale production.
The maximum size of the die is limited by the printing plate. The largest plate size is A1, or 594 mm x 841 mm.
Suitable Materials
You can hot-stamp most materials, including leather, textiles, wood, paper, cards, and plastic.
The thickness depends on the material’s density and flexibility. Embossing is usually limited to paper and cards (up to 2 mm), plastic (up to 1 mm), and leather. You can create indentations (emboss one side) on materials of any thickness.
Processing Costs
The cost of dies for hot stamping and embossing is low, but rotary tools and matching dies are expensive.
The processing time is short, with a capacity of up to 1000 parts per hour.
Labor costs during production aren’t high, but they depend on the design’s complexity. Since the tools must align with existing printed materials, die – changing time can vary.
Environmental Impact
The environmental impact is very small. For some designs, like border decorations, all the foil within the design area may be wasted, but recycling used foil isn’t practical. Embossing doesn’t produce waste.
Hot Stamping and Embossing Processes
Technical Explanation
Hot stamping and embossing are basically the same process. The difference is that in hot stamping, there’s a layer of foil between the die and the material being printed on.
The dies are made of metal. They’re created using processes like laser cutting, photochemical machining, or CNC engraving. The raised parts of the die have an image engraved on them, which can print either a positive or negative image of the design.
Both processes need high heat and pressure. The metal die is usually heated to between 100 and 200°C. It can work in a linear or rotary way. Rotary operation is very fast and can be used for continuous production of flat sheets and cylindrical parts.
Metal foil is made of very thin aluminum sheets and is also used in vacuum plating. Non-metallic colored foils, printed foils, patterned foils, and transparent foils are plastic films. Both types are supported by a plastic base film. After printing, the foil keeps the film intact. There’s a thin layer of adhesive on the surface of the foil to bond it to the material.
During hot stamping, heat and pressure are applied to the material at the same time, pressing the foil into its surface. The hardness of the material and the pressure on the tool determine how deep the impression is. The tool has square edges, which create a sharp edge when it cuts into the material.
Embossing happens between matching tools. Making a depression only needs one set of die tools. For aesthetic and functional reasons, sharp edges can put stress on the fibers of the workpiece, so embossing tools have a small radius at the edges. When combining hot stamping and embossing with foil, the cut isn’t as clean as when doing each process separately.
Case Study: Hot Stamping on Paper
Different types of foil come in rolls (Figure 1). Each roll can supply foil that’s 640 mm wide and either 122 mm, 153 mm, or 305 mm long. Cut the foil from the roll to the right length and load it into the machine (Figure 2). The die is a chemically processed magnesium plate (Figure 3). It’s installed on a press behind the foil. A series of vacuum nozzles pick up the paper and place it on the printing plate (Figure 4). After pressing for less than a second, the paper can be removed (Figure 5).
After embossing, the foil (Figure 6) winds around a take-up reel and is now waste. On the finished hot-stamped paper, the gold foil catches the light, creating shiny and eye-catching design details (Figure 7).
About the Author: Gavin Xia
This article was written by engineers from the RAPID PROTOS team. Gavin Xia is a professional engineer and technical expert with 20 years of experience in rapid prototyping, metal parts, and plastic parts manufacturing.
