Лако-красочные материалы — производство

On hundred percent solids, solvent-free-aerobic acrylic adhesives are often customized to the needs of the assembly and the process. They produce permanent, structural strength bonded assemblies, pottings, and (electronic) coatings within seconds. Productivity is increased; assembly automation processes are made more efficient because the curing technology can be customized to fit the requirements of the process. The several curing methodologies are completed in seconds and can be installed at the time and place most convenient to the manufacturing process. Table 3 summarizes the advantages of using aerobic acrylic adhesive technologies.

Examples of how aerobic acrylics’ formulation flexibility allows tailoring the adhe­sive to the process to maximize efficiency include the following:

1. A manufacturer of high-speed printers also requires 5 min of assembly time before fixture occurs in a 10 mil shimmed bondline gap. In this application, a number of ferrite magnets are bonded to metal frames and assembled in the proper geometrical arrangement in one step. This adhesive process replaces a combination of mechanical clamps, spacers, and holding screws.

2. A manufacturer of restaurant appliances fastens a stainless steel top to a com­bined counter/refrigerator/stove unit. The standard attachment technique included both welding and the use of self-tapping screws. An aerobic acrylic adhesive has replaced these techniques resulting in a lower cost assembly requiring less skilled labor.

3. Aerobic acrylics also show enhanced cure speed, tensile strength, moisture resistance, and the ability to resist automotive bake cycles, which can be as high as 450° F. The operation also requires fixturing through a variable 10 to 20 mil gap in less than 30 s. Thixotropic adhesive is applied to the area to be bonded and activator sprayed directly on top of the adhesive. The metal is immediately folded to form a ‘‘hem’’ joint.

4. A fuse manufacturer replaced a 30 min epoxy used in a heat cure process to assemble stainless steel inserts into phenolic holders. By utilizing an aerobic adhesive bonding process, the assembly was complete in 30 s at room temperature. The resulting increase in productivity more than offset the higher adhesive cost. A cyanoacrylate bonding process was even faster, but did not resist aging in a moist atmospheric environment or pass a drop test for impact resistance.

5. Many kinds of adhesives are utilized in the bonding of loudspeaker magnets, DC motor assemblies, and other types of magnet bonding. Some manufacturers still prefer to use mechanical clamps. The factors that contribute to the choice of a joining process include the cost of the adhesive, labor rates, speed of adhesive fixture, acceptability of odor level, and energy costs. Aerobic acrylic adhesives have been used primarily for their rapid fixture (as little as 12 s) resulting in faster assembly rates. Table 4 compares cure speed and other simple considerations used when choosing an adhesive for attachment of ferrite. The above applications are illustrated in Fig. 2.

The most familiar automotive use of activator curing types of aerobic acrylics is in DC motor assembly. This end use is particularly illustrative of the process streamlining and cost savings opportunities offered by this unique technology. An epoxy method is shown in Fig. 3.

First used commercially in 1982, to bond ferrite magnets, cold bonding processes have increased in utility and sophistication, as indicated in Fig. 4. Productivity enhancing and quality improving uses are limited only by the imagination of the design engineer.

Table 5 shows the difference in labor, time, and by extension, cost between using an epoxy and an aerobic acrylic adhesive.