Researchers at BASF Aktiengesellschaft AG (Ludwigshafen, Germany) have developed a new way of joining molded plastic and sheet metal. The parts are attached by mechanically pressing a collar protruding from the metal component into the plastic component.

Collar joining is a two-step process: first, the collar is formed in sheet metal and then it’s pressed into a sheet of plastic. The base of the collar features an undercut, which anchors it firmly in the plastic.

"The process involves no heat and is suitable for both unreinforced and reinforced polymers," claims Ulrich Endemann, head of research for hybrid parts and one of the system’s inventors.

"Our new assembly system is simple, reliable and cost-effective," Endemann points out. "Even if you take into account the investment cost for a press or assembly robot, collar joining for large volume production is cheaper than current assembly methods."

According to Endemann, the new collar joining system has a number of advantages. For instance, he says it gives engineers more freedom to optimize the strength of the plastic component, which is particularly important for high-stress applications. "As a result, hybrid parts can be made smaller and lighter, while delivering the same functionality," claims Endemann.

"Another advantage is that parts are less prone to warpage than ones produced in an over-molded assembly," adds Endemann. "The mold tool is easier and cheaper to build, and higher production rates are possible.

"The success of hybridization lies in the ability to combine the advantages of two materials in a single part to achieve both technical and economic advantages not obtainable from a single material alone," concludes Endemann. "Hybrid components offer great cost-reduction potential, making their use attractive in highly competitive industries, such as automobile manufacturing."