Modules used for the application of hot melt are valves that allow adhesive to flow through nozzle tips and onto substrates.
Modules are attached to heated blocks called guns or applicators. These modules are actuated pneumatically into “On” position by a high speed solenoid or magnetic coil. This lifts the internal needle valve off the needle seat and high pressure hot melt flows.
These modules are turned “OFF” by pneumatic solenoid or internal spring forcing the needle valve against the needle seat stemming the flow of hot melt.
The module is the wear component – where the internal seals separate the fluid and compressed air chambers. As these seals wear the needle valve can slow or seize in its operation. Usually these pneumatic modules have “weep holes” that allow adhesive that moves past the internal seals to be easily recognized for maintenance.
Most electrically actuated modules have few internal seals to fail. Rather, the internal spring used to shut off the valves tend to fatigue over time with high temperatures or the magnetic coils simply fail to lift the needle.
Modules are available in many shapes and sizes. Adhesives, filtration, application temperatures and tank cleanliness can dramatically affect the modules short and long term performance.
Most modules will offer millions of cycles before needing replacement. Some newer precision modules have been documented to offer in excess of 200 million cycles.