Structural bonding is replacing mechanical fastening-bolt, screw, clip or weld-throughout the assembly process. Structural adhesives cover the entire bond area, often creating a stronger bond than traditional, intermittently spaced fasteners.

Structural adhesives are designed to bond metal to metal or to plastic, fiberglass or other substrates. Typical adhesives include two-component epoxies or modified acrylics. In many cases, these high-viscosity adhesives have various mix-ratios, a rapid cure time, and require special handling for optimum performance.

Structural bonding is particularly appealing for replacing welds-no more bubbles or extra work to repair areas for cosmetic reasons.

Some structural adhesives can be used on clean or painted surfaces, while others are effective on oily metal.

Metering, mixing, dispensing

The equipment and method of metering, mixing and dispensing the structural adhesive are as important as the adhesive itself.

Sealant Equipment & Engineering, Inc., Plymouth, Mich., offers meter/mix/dispense systems that are ideally suited for structural bonding.

Its Program-A-BeadR 692 system is a robotic-integrated system that meters, mixes and dispenses precisely sized beads of two-component adhesives or sealants for high-volume robot or automated structural bonding applications.

Servomotor powered, the advanced system's positive displacement meter electronically controls the flow rate of the mixed material through all facets of the dispense process. With its servo drive and Device Net controls interface, the dispense rate is varied in conjunction with the robot tool tip speed. This is especially useful in making corner beads consistently sized with straight bead paths for a constant bead profile regardless of contour.

Mounted on the end of the robotic system's arm, a Snuf-BakT No-FlushT dispense valve with disposable mixer/applicator nozzle assures thorough material mixing and eliminates the need for solvent flushing.

Constant flow

Sealant's SEE-FLOR 494 system is a bead- dispensing system for precisely proportioned two-component structural adhesives, ideal for applications where a constant flow rate is preferred.

A reliable, versatile and durable dispense system, SEE-FLO 494 is designed to robotically or manually dispense a high-quality, mixed, uniform bead of two-component structural adhesive (epoxy, polyurethane, or acrylic) onto galvanized sheet metal, fiberglass-reinforced plastic, or sheet-molded compound parts.

The system accurately controls the flow rate of mixed material at a preset rate, thereby dispensing a precise uniform bead of adhesive throughout the specified bead path. The system's positive-displacement volumetric-metering pumps feature abrasion-resistant seals and a "quick service" seal cartridge.

SEE-FLO 494 provides consistent flow capability. Its Snuf-Bak No-Flush dual-component dispense gun features a disposable, no-moving-parts mixer nozzle.