Hot stamping

Hot stamping is a fast and easy process to provide parts with a decorative pattern or lettering. The image is transferred from a carrier foil to the part with the help of a heated stamping press as shown below. It is a dry process and the parts can be handled immediately after stamping.

In standard hot stamping, the stamping press is provided with a heated die with a raised pattern, as shown in the figure below, whereas dome printing uses a raised pattern on the part, as is shown in the next figure (II).

The difference with the hot transfer process is that the film does not contain the complete image in advance of the stamping process, whereas the hot transfer foil has already been pre-printed with the final image before it goes on the part. The hot transfer process is more expensive and is especially suited to complicated multi-color designs.

During the hot stamping process, the pressure on the part requires the part to be firmly supported and designed to withstand the stamping forces. The stamping die must be designed in such a way that no air is entrapped between the die and the part. For good adhesion, parts must be clean and free of oil, grease and mold release. Cleaning in a suitable soap solution or a solvent may be necessary.

A wide variety of stamping foils are available, with a color coating, a layer of metallic foil, or a combination of the two. They can be used to provide parts with a colored pattern or a thin metallic layer. Wood grain patterns are also possible.

The figure below shows an example of a stamping foil. The release coat allows the easy separation of the carrier and the color coat at the end of the stamping process, and the sizing provides the adhesion to the part.

The compatibility of the color coat, the binder and the sizing with the part material should be checked (e.g. environmental stress cracking of polycarbonate and polycarbonate blends). It is advisable to consult the stamping foil supplier on this issue and to perform prototype tests.