In recent years there has been a sea change in fastening methods, and
probably the greatest change has come in the use of tapes and adhesives
to replace welding and mechanical fastenings. Bonding is today's fastest
growing assembly method
Bonding might employ tapes and adhesives as the enabling products, but
the complexity of today's chemistry emphasises that individual parts are
no longer simply held together by adhesive, but are bonded into a fully
integrated component. This takes joining far beyond many engineers'
prejudiced views of tapes and adhesives as a last resort. Bonding can now
provide a stronger, more versatile fixing than many mechanical options.
Indeed, today's bonds are even stronger than the materials they join.
Bonding agents are quicker to apply, less costly, are lighter than
mechanical fastenings, enable use of lighter gauge metals and can both
join and seal in one operation. Materials are not distorted by the heat
of welding or brazing, while bonding offers higher fatigue and impact
resistance. It also eliminates drilling, punching and finishing, not to
mention the weaknesses that can be created in materials as a result of
these operations, and helps damp vibrations.
Industries that are leading the field in the adoption of bonding in
favour of more traditional jointing methods, include aerospace and
automotive. Double-sided tapes, for example, are used by Airbus to bond
stainless steel scuff strips to aircraft wings. Previously, rivets were
used but these caused scoring as the flaps were deployed. In this
application, the tape has to accommodate expansion and contraction over a
very wide temperature range.
For rail, car and commercial vehicle manufactures, bonding helps to
reduce weight and thus improve the fuel consumption of their products.
Again, tapes are widely used as a rivet replacement for fastening panels
on trucks, buses and trains, and like the previous aerospace example,
they easily compensate for differences in thermal expansion between the
different metals they bond together.
Among recent innovations are laminating adhesives - low surface energy
products that simplify the bonding of 'difficult' substrates, such as
polyethylene and polypropylene; water-based spray adhesives with instant
tack for high-strength bonding of laminates; and fast, structural
adhesives for plastics bonding and furniture making that avoid the need
for pins and jigging.
When manufacturers are faced with the stark requirements to cut their
manufacturing costs, and develop and market new products faster and with
greater frequency, they could do worse than take a look at what's on
offer in the area of bonding - a technology that has come of age. All of
the product types mentioned in this article are available from 3M, who
can provide general advice on specific applications. Alternatively,
contact Chiltern Adhesive Products (www.chilternadhesives.co.uk), a
recently appointed converter of 3M's technical bonding systems.