By ICOMold by Fathom
Hot stamping is a secondary process to injection molding that is used to add logos, color accents or instructional information to plastic parts. Hot stamping plastic parts also can be done to achieve a specific color, texture or metallic finish. The process can be done with a press (hot stamping) or without a press (tipping).
Plastic stamping process
Hot stamping plastic is a dry process that uses a film or foil. The film is actually a thin sheet of plastic comprised of several layers. The simplest film has three layers. The bottom layer is the adhesive. The middle layer contains the coloring for the logo. The top layer is a protective finish. The logo itself is machined onto a metal die. The film is pressed between the heated die and the plastic piece. The heat and the pressure of the die adhere the logo to the plastic. The heat from the die will activate certain layers of the film, causing it to stick to the plastic part. The film is not punched out of the plastic sheet; rather, the logo is essentially fused to the plastic, making hot stamping one of the most durable and cost-effective secondary processes. Unlike spray paint, the color, image or logo only appears where the die touches the plastic part.
Hot stamping dies: Hard vs. soft
Hot stamping is usually done with a heated die and a press. Die materials are termed either hard or soft. Hard dies are made of metal like copper, brass, magnesium or steel. Soft dies are made of flexible silicone. Hot stamping on flat surfaces with a press is typically done with hard dies. Soft silicone dies are more versatile and can be used on curved or unconventionally shaped surfaces. Silicone dies also require less pressure, making it easier to hot stamp odd-shaped plastic parts. However, silicone dies do require more heat. The excess heat will eventually render the silicone die useless as it stiffens and begins to lose its flexibility. Hard dies require more pressure but less heat. Silicone dies can be used without a press in a process called tipping.
Hot stamping vs. tipping
Tipping is a hot stamping process that does not need a press. Instead, the part itself is used as the die. This process works well for plastic items that have raised lettering or a raised logo. Only the raised lettering or logo will receive coloring while the rest of the plastic part remains untouched. A large soft die is used to administer the film to the plastic part. A silicone die that is larger than the part is heated. It then presses the film over the entire part. Only the raised sections of the part will come away with color. Tipping also is used to apply texture to a large flat surface. Faux wood grain is a popular texture that can be applied with the tipping method.
Hot stamping process on unconventional plastic parts
Hot stamping plastic is not limited to flat surfaces. As noted above, silicone dies can be used to hot stamp irregularly shaped plastic parts. There also are hot stamping presses that can accommodate curved items. In this instance, the plastic part is placed in the press and brought to the heated die. The plastic part is then rotated against the stationary die while the film is applied.
What materials are used for hot stamping?
Custom hot stamp dies are machined from copper, brass, magnesium, steel or silicone. Hot stamping uses a dry ink or metallic foil. Material choice is determined by the detail of the artwork and the expected part production volume. Hot stamping plastic is a way to achieve high-end decorative results. Hot stamping foils are available in a wide array of colors and finishes, from matte to high gloss, including specialty foils that are holographic or metallic.
Is hot stamping durable?
Hot stamping plastic parts is one of the most durable post-processing options available. Hot stamping plastic is more durable than paint. Paint is applied to the surface of the plastic part. Hot stamping fuses the color, design or logo into the plastic itself. The hot stamp film or foil effectively becomes part of the plastic. Hot stamping will not chip or melt away. Hot stamping is resistant to most chemicals that would remove paint. Extra layers of protection can be added to the film and applied to parts that will encounter harsh conditions.
The benefits of hot stamping
Hot stamping plastic is a dry process so there are no unpredictable chemicals, no need for specialized venting equipment and no drying time to slow down production. The hot stamping process tends to decrease packaging and handling costs because the decorated parts can be volume packed without need for spacer material. There will be no damage to the decorated part surfaces since the hot stamping process effectively fuses the logo into the plastic, making it a piece of the plastic instead of just a surface treatment. This makes hot stamping a cost-effective choice for adding color or logos.
Thinking ahead about secondary processes
It is essential to plan for secondary processes in the design phase. Talk to your engineer about the finishes as soon in the process as possible. Early planning will help speed production and lower costs, and it also can help minimize delays down the line. Some plastics are more receptive to hot stamping than others. Be sure to discuss the part’s intended end-use and part decoration during the design phase.
Preparing injection-molded parts for hot stamping
Proper surface preparation is the key for successful post-processing with any plastic part. Hot stamping plastic is no different – making surface preparation a crucial step in the process. A good bond can be achieved by understanding the many chemical- and molding-process factors involved in the part design.
Surface preparation starts before the injection-molding process. The potential for contamination in the mold or on the part is always present in any injection-molding process.
Another consideration is the surface energy of the plastics. Many plastics used in injection molding generate electrostatic surface charges. The electrostatic charges tend to attract contamination. ICOMold’s decades of combined experience help its customers avoid paint defects and maximize hot stamp foil and film bonding. The experts at ICOMold are continually analyzing the entire process, from mold design to material options, to mold prep and part surface preparation.
- Designing with as few cutouts as possible helps provide a better painting process.
- Rounded part edges can be more easily covered with paint than sharp ones.
- Residual burrs can lead to contamination all the way into the painting booth.
ICOMold has developed proprietary systems for keeping tools extremely clean. Clean tools avoid excessive buildup of the materials used in the injection-molding process while minimizing contamination.
Hot stamping plastic parts requires surface energy
The plastics used in injection-molding processes do not carry much surface energy. This can make the adhesion of paints, inks, foils and films difficult to ensure. Cleaning and some pretreatments can go a long way toward preparing the surface for secondary processes. ICOMold by Fathom often pretreats plastics that are going to be painted or stamped. This increases the surface energy of the part and improves the quality of the finish.
ICOMold by Fathom is headquartered in Hartland, Wisconsin. ICOMold is home to one of the world’s only 30-second injection-molding cost calculators. Learn more at www.icomold.com.
