Ordinarily, if you want to join metal and plastic items together, you have to use either adhesives or rivets. Engineers at Germany's Fraunhofer Institute for Material and Beam Technology, however, have developed a bonding "gun" that they claim makes for a much faster and cheaper joining process.
One of the problems with adhesives is the fact that the joined items have to be left alone while the adhesive sets, delaying further steps in the production process. Riveting, on the other hand, can damage plastic objects. Additionally, using either approach, manufacturers have to continually pay for more adhesives or rivets.
The Fraunhofer device gets around these problems, utilizing what is known as the HeatPressCool-Integrative (HPCI) process.
It starts by pinching metal and thermoplastic items together, at the spot where they need to be bonded. Targeted inductive heat is then applied to the metal, causing the plastic that it's in contact with to partially melt. This allows a surface layer of the plastic to penetrate into an array of tiny anchoring structures that were previously laser-etched into the surface of the metal at that spot.
Once the plastic cools and contracts, it forms a secure fit with those structures, thus bonding the two objects together. The whole process takes only a few seconds.
Fraunhofer states that the HPCI gun could be integrated into existing production lines, perhaps being mounted on robotic arms in place of spot-welding guns. Possible applications include the assembly of automobile bodies, or the bonding of stainless steel panels to dishwashers or refrigerators.
The device (incorporated into a larger assembly platform) can be seen in use, in the video below.
Source: Fraunhofer