CMT Pin: for high-strength metal-plastic joints

A stable form-fit, drop by drop

Welded pieces of metal are highly resilient; however, only metals that conduct electricity can be electrically welded. For this reason, CMT Pin is a proven welding process for joining metals to non-metallic materials such as plastic. Fronius has succeeded in developing an innovative solution: the CMT PIN (CMT = Cold Metal Transfer) welding process relies on arc welding to join the different materials.

Form a positive joint between metal and plastic with CMT Pin

The Fronius CMT welding process welds pins with spherical heads that project beyond the shaft diameter of the pin – similar to a mushroom – onto a metal surface. The “burred surface” created in this way serves as the contact and bonding basis for the metal. This is then potted with plastic, for example, to cover the pins. The potted spherical heads give the joint additional resistance against the separation of the two types of material. The pins are approximately 0.8 mm thick and only 3 mm long. If the plastic has elasticity, the joint can be undone like a Velcro® fastener. An adhesive bond offers up to ten-fold the force transmission of a conventionally bonded metal-plastic joint.

A variety of possible applications

Additional solutions and types of joint are possible depending on the shape of the pins:

• A metal sheet can be joined to plastic or rubber. This combination exhibits the rigidity and strength of a metal structure coupled with the slip and corrosion resistance of the coating
• Sheet-metal sheaths with pins on the inside, strengthened with glass or textile fibres and plastic sprayed on in foam form, can produce finished parts for use in furniture or technical items
• Concrete can be poured around the outside to build bridges, structures or mobile plants
• Connections for CFRP (carbon fibre reinforced plastic) components can be incorporated in metal structures during the manufacturing process, resulting in a permanently joined monoblock rather than separate components that have to be screwed together
• CFRP-metal joints are suitable for aviation industry components that are subject to extreme stress
• For ceramic, metal or other thick wearing layers, the CMT pins will produce the most effective bonding system. Dry or glued wood joints are also possible