Process Requirements and Equipment Selection for 3D Hot Stamping
Because the cylinder-to-cylinder (rotary) method uses line contact, it can completely avoid the bubbling issues that may occur in flat-bed hot stamping, while also offering higher speed and better quality. However, since both the stamping plate and the counter-die are cylindrical, the machining difficulty and cost are high, and the heat-transfer efficiency of cylindrical plates is not ideal. Therefore, this method is not widely used and is generally applied only for long-run jobs requiring high quality, such as cigarette packaging, liquor packaging, and health-care product packaging.I. Process Requirements of 3D Hot Stamping
1. Hot Stamping Foil (Metallic Foil)
Hot stamping foil is usually composed of 4–5 layers of different materials, such as:base film (PET), release layer, color layer (silver foils have no color layer), aluminum-plated layer, and adhesive layer.
Functions of each layer:
- Base film layer – Provides structural support for the other layers.
- Release layer – Allows the aluminum layer to separate from the carrier film; it determines the transferability of the foil.
- Color layer – Provides color and protects the underlying layer. Common colors include gold, silver, maroon, light blue, black, bright red, green, etc. Gold and silver are the most widely used.
- Aluminum-plated layer – Provides the metallic luster.
- Adhesive layer – Bonds the foil to the substrate during hot stamping.
Hot stamping speed and quality are mainly affected by the release layer and adhesive layer. If these layers are not thermally sensitive enough, stamping speed must be reduced. In the past, heat-transfer limitations restricted flat-bed hot stamping to under 5000 sheets/hour. Today, leading global foil suppliers offer foils that meet modern high-speed requirements. The Swiss Bobst hot stamping machine, for example, can reach 7500 sheets/hour.
Since 3D hot stamping forms an embossed (relief) effect, the requirements for temperature, pressure, and speed differ from ordinary flat hot stamping. Therefore, special 3D hot stamping foils must be used, and regular flat foils should not be substituted, otherwise poor stamping quality or unexpected issues may occur.
2. Temperature, Pressure, and Speed
These three factors are the core parameters of hot stamping technology. Only by controlling their relationship can high-quality stamping be achieved, including 3D hot stamping.Temperature
3D hot stamping requires higher temperature because it completes hot stamping and embossing in a single pass.
- Ordinary hot stamping: 70–90°C
- 3D hot stamping: around 150°C
If the temperature is too low, the foil’s adhesive and release layers cannot melt adequately, resulting in incomplete transfer, missing areas, or exposed substrate.
If the temperature is too high, problems may include substrate deformation, blurred images, unclear characters, foil discoloration, or plate expansion causing misalignment with the counter-die.
Thus, temperature is the most critical factor.
Pressure
Pressure is applied instantly during stamping. After melting, the adhesive layer relies on pressure to bond the foil to the substrate. In 3D hot stamping, the pressure must also create a sculpted relief pattern, so it must be higher than in regular hot stamping.
Foil strength must therefore be higher to withstand the additional pressure.
Too much pressure may tear the foil, damage the counter-die, or deform the printed sheet.
Too little pressure results in incomplete foil transfer or insufficient embossing depth.
Thus, proper pressure control is essential.
Speed
Speed determines the contact time between the foil and the heated die.
- Too fast → insufficient heating → poor adhesion
- Too slow → excessive heating → possible defects from overheating
II. Equipment for 3D Hot Stamping
3D hot stamping equipment mainly includes flat-bed (flat-to-flat) and rotary (cylinder-to-cylinder) systems. The cylinder-to-flat method is not suitable for 3D hot stamping.1. Flat-to-Flat 3D Hot Stamping Machines
Represented by Swiss Bobst, these machines are evolving toward high speed, high precision, and easy operation.Bobst equipment can achieve:
- Up to 7500 sheets/hour
- Precision within ±0.1 mm
2. Cylinder-to-Cylinder (Rotary) Hot Stamping
Mostly used in web-fed, inline production.Advantages:
- Line contact eliminates potential bubbling issues found in flat-bed stamping
- Higher speed and better quality
- Both stamping plate and counter-die are cylindrical → difficult and costly to manufacture
- Heat transfer is less efficient
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