Adhesive and Sealant Applications & Tools
Experts in the tools used for specific applications. The tool may cost you very little, but it accounts for over 50% of the success in the application.
Wednesday, July 13, 2011
Why does my caulking gun drip?
• viscosity of the material—thicker material tends to drip less
• compressibility of the material—less compressible material tends to drip less
• swelling of the cartridge—rigid cartridges tend to drip less
• piston friction inside the cartridge—pistons that retract slightly after the pressure is released tend to drip less
• air bubbles in the material which occur during the filling process—material without any air bubbles tends to drip less
If any of these five factors are present, the gun is not to blame. You can prove this by removing a cartridge from a gun immediately after finishing a dispensing cycle. Some cartridges will continue to ooze while standing upright outside the gun!
Dispensing guns can be designed with certain non-drip features to help reduce the potential for run-on. Non-drip guns are useful for when a smooth bead is not required, as in filling small cracks in a number of different locations. Since no-drip guns tend to increase the number of starts and stops during the application, they come in handy when only one or two pumps of the gun at most will fill the crack. Continuous flow guns, on the other hand, should be used when a smooth bead is required over many pumps of the gun, as in filling long or continuous joints. On continuous flow tools, always remember to press the recoil plate with your thumb to release the pressure when you finish your application. Pressure on the rod is instantly removed by releasing this tension.
Albion gun models B1, H10D and H10XD have no-drip features. In addition:
- all of our cordless guns are no drip as the motors reverse whenever the trigger is released
- all our pneumatic guns are no drip as the air cylinder is exhausted when the trigger is released
- our Special Deluxe Drive guns (DL-45, DL-59) have a no-drip mode - just hook the recoil
A caulking gun with a full time non-drip feature is, by design, inefficient. The first 1/4 to 1/3 of each trigger stroke is wasted motion, as it is required to release the non-drip mechanism and reengage the gripping plates to the rod, thus repressurizing the material before new material flows out the nozzle. When comparing non-drip and continuous flow tools, you will notice that less material is dispensed per pump when using the non-drip tool.
The graph below displays pounds of force as a function of the distance traveled by the drive rod. As you can see, a major disadvantage of a dripless system is that force goes all the way back down to 0 after each pump. In addition, the standard drive system exerts force over a greater distance interval than the dripless system.
Finally, a quick historical note: Ratchet guns were the first caulking guns to hit the market and in theory they functioned as non-drip tools. In 1933, Albion Engineering Company patented the first smooth rod caulking gun to provide a more continuous flow of material. This is what launched smooth rod drive caulking guns into the marketplace. The first non-drip smooth rod design was introduced by Dripless, Inc. in 1992. Since then there have been many variations using this technology.
To conclude, dripping or run-on occurs primarily due to issues with the material or package used to contain the material. Dispensing tools can be designed in such a way to reduce run-on, but guns with a full-time non-drip feature are generally less efficient than continuous flow guns. In most cases, choosing the right tool for a particular application will ultimately come down to whether or not a long, smooth bead is required.