AA Dispenser Rebuild

To prepare your AA dispenser for maintenance, you need to turn off the power, the supply pressure, and the pump. Disconnect the hoses, and if the dispenser contains adhesive material, apply a solvent to prevent it from curing. Additionally, disconnect the airlines and the sensor. Finally, use hex keys to dismount the double AA dispenser.

Once the dispense chamber has been removed from the machine and placed on a work surface, start by removing the fittings. This step ensures the internal passages are clean, especially if adhesive materials or RTV have caused cured material to accumulate in the ports or under the valves. Fittings often become clogged and may need replacement. If the material has dried on the threads, lubricate the ports with grease, oil, or solvent to prevent further curing and proceed to remove the cartridge valves.

For grease dispensers, it may not be necessary to remove the cartridge valves if no issues have occurred. However, with RTV or adhesive systems, it is recommended to remove and inspect them to ensure they are free-flowing. Loosen the valves using an adjustable wrench or a one-inch open-end wrench. In some cases, material may have dried around the valve, requiring the application of solvent to keep it from further drying out. Remove all three cartridge valves, inspect them, and set them aside. If any valves are clogged, rebuild kits are available. Severely clogged valves may need to be replaced, so keeping spares on hand is a good practice.

Continue applying solvent to the ports, threads, and valves to prevent the material from setting or drying out. Once the valves are loosened, they can often be unscrewed by hand. However, adhesive systems may cause threads and bases to stick, making manual removal more difficult.

The next step is to remove the flange block from the dispense chamber, which is typically secured with four socket head screws. Loosen the screws, and the flange block should come off easily. If it doesn’t, dowels between the blocks may require additional effort to separate them.

Inspect the screw threads for any RTV or adhesive residue, as this can make reassembly difficult. Clean off any residue to ensure smooth operation. On this unit, the side of the flange block facing the chamber contains the rod seals, which are small and require careful handling. Remove and inspect the seals, replacing them as necessary. Remove the O-ring between the flange block and the dispense chamber, being careful not to damage the aluminum. Clean off any residue to ensure the two blocks fit together flush and straight during reassembly.

Clean the threads on the material ports to ensure they are in good condition before reassembly. Under the rod seal in the flange block, there is usually a bushing, and sometimes two seals. After removing the metering rod, slide it through the bushing to ensure there is no extra resistance. Use solvent to clean the bushing and the rod surface, ensuring no residue remains. Clean out the pocket for the rod seal before installing a new seal.

The dispense chamber itself has three ports for the cartridge valves, three ports for the hoses used in dispensing and purging, and the rod entry point. Use a pick and solvent if needed to clear the passageway for the rod. When the rod is inserted, you can observe it passing through each port where the valves are installed. Debris pushed by the rod will collect in the middle of the block and can be removed through the top holes. Be careful not to push the rod in at an angle or damage its edges, as leftover material can clog downstream components like dispense valves or end-of-arm tooling.

Remove debris with a pick or solvent and a cotton swab. Use soft tools, such as swabs, brass, or plastic picks, to avoid scratching the aluminum dispense chamber. Many dispensers feature dual seals, with the first acting as a rod wiper or scraper. This seal, along with the energizing O-ring, should be installed carefully. In this machine, the orange rod seal without the O-ring serves as the scraper and is installed first, followed by the main rod seal closest to the dispense chamber.

Apply grease to the O-rings to help them stay in place in their grooves. Add solvent to the seal pockets to eliminate air and allow the seals to compress and seat properly.

After both blocks are cleaned and the seals installed, bolt them together. Ensure the rod seal is in place and the rod is well-lubricated before inserting it. Once everything is assembled, tighten the first cartridge valve while access for the wrench is still easy. Lubricate the threads and seals before inserting each valve.

When tightening the last valve, work it back and forth to avoid binding, especially in tight spaces. The orientation of the cartridge valves does not matter, but ensure there is enough room for the vent holes to breathe. Inspect and clean the fittings, ensuring the threads and mounting surfaces are in good condition. The O-ring on each fitting must seat properly in the angled hole to form a seal. Ensure the O-rings are undamaged and not pinched during installation.

With all components reassembled, the chamber is ready to be mounted back onto the machine. If you have additional questions about maintenance, repairs, or reassembly, feel free to contact us.