While spot welding has for long been seen as the technology of choice for joining car components, particularly parts making up bodies in white, rapid bonding using adhesives is increasing its penetration of automotive as well as other markets, not least because it allows the very rapid bonding of plastic and composite parts, which cannot be spot welded.
We first heard just how fast bonding has become when we happened to encounter Julian Bond, R&D engineering manager for Parafix at the end of last month’s Manufacturing Summit and asked if it was possible to bond parts together as fast or faster than using spot welding. He responded by saying they could bond parts, “In seconds” using adhesive tapes.
These provide vastly stronger bonds that the kinds of sticky tapes used round the average home or office, so they can have failure modes in which substrates fail before bonded joints. As regards time, Steve Barwick from Parafix described a recent job developing the technology to bond charcoal cloth onto a microporous PTFE vent where cloth die-cuts are spread out and bonded to the vents robotically, requiring less than a second for the whole operation, including bonding.
The company works with a range of suppliers of adhesive systems and machinery, including 3M, Tesa, Nitto Denko, Scapa, Advance Adhesive Tapes, Rogers, Laird Technologies, Accuplace and Adhesives Research. A lot of the leading edge development in structural bonding films, he said, is being undertaken by 3M, which he said, is “Developing all manner of technologies”, including tapes for bonding composites.
These generally give a tack strength but have to be heat cured to achieve full strength. Pick and place robotic handling copes with the problems of handling thin, flexible adhesive tape components. In automotive applications, final cure can often be achieved in the paint curing oven. Barwick says that while designers of cars and mobile phones tend to be well aware of the advantages to be had from adhesive tape bonding: reduced assembly time, stronger bonds and the absence of stress concentrations or bosses to accept screws, smaller companies tend to be less aware.