AirFree® Liquid Dispensing vs. Air
How does AirFree® fluid dispense technology compare to air pressure as the driving force (drive system) used to dispense assembly fluids?
Syringe Based Systems
AirFree® liquid dispense technology features the Linear Drive System (LDS) for dispensing assembly fluids in a manufactruing process. The LDS and air both have to displace fluid volume from a cylinder (syringe).
The LDS™ is connected to firmware that converts volume (cc’s), inputted by the operator into the firmware, using length and innear diameter into forward steps. This allows the precision stepper motor to move the same distance every time, holding the piston in place, forcing the dispense fluid out the tip. No adjustments are required once a dispense program is set.
Air pressure drive systems are connected to an air solenoid and adjustable timing circuit. Guessing via trail and error are the only way to set your dispense volume. Immediately after the solenoid closes, the air in the syringe dissipates and the pressurized fluid has a choice as to direction of flow: out the small dispense tip or back up the depressurized syringe. It always follows the path of least resistance, up the depressurized syringe (piston bounce) and never bounces the same from one dispense to the next. A portion of your desired fluid dispense volume stays in the syringe resulting in very poor repeatability from one fluid deposit to the next. As the syringe reservoir empties the space between the piston and the top of the syringe increases requiring solenoid open time to increase. This scientific fact, volumetric displacement, causes multiple operator adjustments to the dispense program during the production day. Air pressure variables require each syringe air system be set up independently and adjusted constantly all day long.
Furthermore, when the air solenoid opens, air speeds into the syringe and violently slaps the piston. Over the course of a production day the repeated violent slapping of the piston stresses and heats the fluid changing the formulation and effecting bonding properties. The LDS system uses a patented controlled ramping of the motor from start to full speed protecting fluid properties and maintaining bonding strength.
Air pressure systems repeatability range between +/-30% to +/-15% whereas air free liquid dispense systems repeatability ranges between +/-5 to +/-2%.
Valve systems
Tank reservoirs use air pressure as a drive system to move fluid from the tank to the valve. Air pressure variables such as: Air compressor size, length of production facility air plumbing, number of production machines drawing off the air plumbing and length of fluid plumbing to the valve cause constant changes to fluid supply pressure. Dispense valves are often opened by these air supply lines and closed by spring. As springs wear, coupled with the aforementioned air supply variables, repeatability from one dispense to the next, for some valves, is inferior to the AirFree® Technology featuring the LDS. The discussed variables requires each valve air system be set up independently and adjusted daily. Air pressure systems repeatability ranges between +/- 10% to +/-2%.
