Application Process

(Courtesy Nordson Corp.)

A wide range of equipment is available to help you apply virtually any adhesive or sealant during the manufacturing process. If your operation calls for sealing, gluing, bonding or molding, five application methods are typically used to deposit material to the part – dots/beads, spray, web coating, wheel or brush. The right material application method is based on your specific production requirements and the type of material being used.

Dots/Beads

There are a variety of options available for achieving precise, consistent dot and bead patterns.

  1. Hand Gun

    Typical handgun systems can be cartridge-based or hose fed. Cartridge-based systems are portable, but require frequent refilling and costly cartridges. In addition, product quality is dependent on operator skill. However, these manual dispensers a versatile, inexpensive option for touchups, low-volume assembly and field work. They provide a clean, comfortable alternative to squeeze bottles and hand syringes, also have mechanical leverage that makes it easy to dispense thick materials like greases and silicones without hand fatigue.

    Hose fed handgun systems minimize physical stress and fatigue when manually applying hot melt adhesives. They are ideal for horizontal gluing applications on flat panels, with select nozzles for producing bead or spiral spray patterns. The hose fed handgun has spray patterns that range from 0.25 to 6 inches wide (6 to 152 mm), offering more consistent output than cartridge-based systems to optimize productivity. Many handguns are also designed with ergonomic configurations that allow operators to maintain a neutral wrist position and cool-touch handles for added safety.

  2. Automatic Pneumatic Gun

    Air-driven guns provide accurate timing and are insensitive to material viscosity and system pressure. Today’s most innovative automatic pneumatic guns deliver reliable, long-life operation, which reduce actuation module replacement costs. In addition, many incorporate design features – like color-coding to identify actuation (AO/AC and AO/SC), easy-on features for faster installation and special configurators to help you determine the right gun for your application. Highly reliable and accurate, automatic pneumatic guns can run at speeds that exceed 3500 cycles per minute.

  3. Automatic Electric Gun

    Automatic electric guns can accommodate very fast cycle times (in excess of 3000 per hour). Typically incorporating an all-electric driver to optimize performance, these guns can achieve greater pattern control and consistency. In addition, by eliminating the used of compressed air and dynamic seals, automatic electric guns lower operating costs and minimize module maintenance. They also have longer service life compared to pneumatic guns, reducing replacement costs.

  4. Jetting

    A non-contact application method used to apply dots of material only. It is used quite often in electronics applications because it is known for dispensing material in small spaces – as tight as 175 micrometers at speeds up to 400 mg/second. In operation, the jet "flies" over the part or substrate, and using a patented high-speed mechanism, shoots precise volumes of fluid in dots, lines and patterns. The result is very fast, very accurate material application. In addition, jet dispensers are easy and quick to clean in 10 minutes or less with no tools required.

Spray

When considering spray application methods, manufacturers must consider material viscosity, overspray issues and pattern control requirements.

  1. Air Spray

    Low Volume Low Pressure (LVLP) spray systems provide consistent coating of low viscosity fluids. Here, microliter to milliliter amounts can be reliably dispensed in round patterns with diameters ranging from 4.3 to 50.8 mm (0.17" to 2.0") and in fan patterns with widths up to 165.1 mm (6.5"). The combination of adjustable fluid flow, adjustable nozzle air and post-air cutoff provides good spray control, but often, the challenge of overspray must be addressed.

  2. Airless Spray

    Automatic airless spray guns are designed to deliver maximum reliability in high-production airless painting, sealant and adhesive applications. They are suitable for moderate viscosity materials, and can provide fine atomization and controlled deposition with minimal overspray. Air-actuated guns provide fast response times (30 to 40 milliseconds) and high-speed cycling capability (up to 2500 cycles per minute), and are ideal for coating situations requiring precise material application.

  3. Fiberized Spray

    Continuous fibers provide very accurate pattern control and minimize overspray. Typically fiberization forms an open, netlike pattern that is a swirl, meltblown or random fiber.

    Swirl spray nozzles improve bond strength and product quality in hot melt adhesive nonwovens and product assembly laminating applications. Many applicators allow you to control adhesive fiber size, density and pattern width for better bond performance. Typically, you can produce low-density, large-fiber patterns for maximum bond strength; open patterns for absorbency; or highly dense fine-fiber patterns for heat-sensitive substrates.

    Meltblown spray nozzles enhance high-speed production with random hot melt adhesive coatings for continuous applications. Ideal for wide-web lamination, meltblown spray coatings improve appearance and hand-on personal hygiene products and produce excellent fine-fiber coatings in high-speed tissue plybonding.

    There are also nozzles available to produce random hot melt adhesive coatings for continuous high-speed lamination of roll-based materials. These are typically used in nonwovens, wide and narrow web coating, and general manufacturing and assembly applications. Random fiber nozzles help achieve dense, uniform coverage with tight edge control and patterns that can yield consistent bonding, tolerate process parameter changes, and help improve product quality.

Web Coating

There are a variety of options available for web coating applications.

  1. Slot Applicator (On- or Off-Roll)

    High-performance slot applicators deliver precise intermittent and continuous hot melt adhesive coatings. Slot applicators provide accurate thickness control, with a closed system that minimizes premature drying or curing. Most can offer clean adhesive cut-off, and can accommodate cycle rates of 4,000 and 5,000 per minute depending on their design specifics. Slot applicators are available in a range of application widths, with other options that include several options, including anti-stick coating, low-volume output and additional shim plates and slots.

  2. Fiberized Spray

    A continuous fiber spray provides very accurate pattern control and minimal overspray. This non-contact application method is excellent for textured webs, forming an open, netlike pattern.

    Typically used in hot melt adhesive nonwovens and product assembly laminating applications, fiberized spray nozzles improve bond strength and product quality. Many applicators allow you to control adhesive fiber size, density and pattern width for better bond performance. You can also produce low-density, large-fiber patterns for maximum bond strength; open patterns for absorbency; or highly dense fine-fiber patterns for heat-sensitive substrates.

  3. Wheel/Roller

    Wheel and roller applicators provide a variety of pattern options, but may require frequent cleaning if the adhesive cures on it. These applicators apply hot melt adhesive from the top, the bottom or side, and patterns can be tailored to meet specific production needs.

  4. Dip

    Dip application methods are suitable for thick coatings of low viscosity adhesive.

Wheel

Wheel applicators provide a variety of pattern options, but may require frequent cleaning if the adhesive cures on it. These applicators apply hot melt adhesive from the top, the bottom or side, and patterns can be tailored to meet specific production needs.




Brush

The brush application method is the least consistent and reliable of all. Here, product quality is dependent on operator skill.