GlossaryKind of term: Manufacturing termAdhesive bonding (2K, UV)
What is adhesive bonding?
Adhesive bonding joins parts with an adhesive that cures, such as a two-part or UV-curing adhesive, instead of with bolts, welding or pressing.
The adhesive layer cures between the surfaces and carries the load there, without the parts themselves melting. Two-part adhesives such as epoxies, polyurethanes and methacrylates cure by a chemical reaction once mixed. UV adhesives cure under light of the right wavelength. Others include cyanoacrylates for small joints, anaerobic adhesives for thread locking and shaft retaining, and heat-curing one-part adhesives.
What does adhesive bonding depend on?
The strength of a bonded joint is limited by the adhesion to both surfaces, the strength of the adhesive itself and that of the parts. Adhesion depends on cleanliness, roughness and surface energy: degreasing, abrading or blasting and sometimes a primer, plasma or flame treatment belong to the preparation. Low-surface-energy plastics such as PE, PP and PTFE barely bond without pretreatment or an adhesive made for them. A bond line carries shear well and peel and cleavage poorly, so the joint design, with overlap and a controlled bond line thickness, helps set the strength. UV adhesive needs the light to reach it; for opaque parts there are adhesives with a secondary cure mechanism.
How does adhesive bonding work in practice?
Bonding consists of several steps: preparation, dispensing, positioning, holding during cure and checking. Between handling strength and full cure there can be a long time, depending on adhesive and temperature, and that time counts in the lead time. For batch work a simple bonding fixture can locate the parts and lower the time per part. Bonding is often costed as an item of its own, apart from the machining, because its time follows the number of joints and the cure time, not the machining time.
What is adhesive bonding often confused with?
Bonding is not welding: in welding the material of the parts itself melts, in bonding it stays intact and the adhesive layer carries the load. Plastic welding, ultrasonic included, counts as welding. Nor is bonding sealing: a sealant or liquid gasket seals a joint but is not primarily designed to carry load.
How do you see adhesive bonding in Blake?
In Blake you calculate an assembly as a single unit: the made parts, the bought parts and the assembly's own work as separate lines that roll up together. You enter the time for that own work, such as bonding, yourself. Every result is labelled as an estimate. More on estimating.
Frequently asked questions
Why does a bonded joint sometimes come apart?
Usually through poor preparation, a contaminated or too smooth surface, the wrong adhesive for the material, too short or too cold a cure, or a joint loaded in peel. PE, PP and PTFE need pretreatment or an adhesive made for them.
When do you choose UV adhesive over two-part adhesive?
When the light can reach the adhesive, as with a clear window, and you want to carry on quickly. For opaque parts or heavily loaded joints a two-part adhesive or one with a secondary cure is the more obvious choice.
How should adhesive bonding be costed?
As an item of its own with time for preparation, dispensing, positioning and checking, the adhesive as a consumable and the cure time in the lead time. A bonding fixture is a one-off item for the batch.