Improved Sealing with Liquid Gaskets

Pre-molded or die cut peel and stick gaskets have long been used in manufacturing applications. However, the dispensing of liquid gaskets is a technology that has been gaining strength. Manufacturers now see it as an viable alternative for automotive, medical, appliance and electronics applications. 

Liquid gasketing includes the following processes:

Also called "dispensed-in-place gasketing," this process involves the dispensing of the liquid gasket and curing it "in-place". This product will become a permanent seal on one or both mating surfaces. 

Similar to CIPG, the liquid gasket is applied to one side of the mating surface and cured in place before the final assembly of the product.

This process injects another material, usually a gas into the liquid gasket polymer at the application point. The result is that the gasket obtains a foam-like structure after cure.

The mating parts create a mold into which the liquid gasket is injected. The result is usually a semi-to permanent gasket.

The growth of liquid gasketing techniques is spawned by needs for increased productivity and cost reduction. The established reasons for using liquid gasketing include improved seal integrity, inventory reductions, reduced assembly and handling costs, and a higher product quality. In one case, the actual cost per part savings has been well over 20% versus the use of die cut gaskets. 

Typical applications for liquid gasketing include the following:

• Automotive transmissions, oil pans, window seals, front engine plates, cam covers and noise reduction for windows, alternators, etc.
  
• Electrical or electronic module assemblies, transformer sound deadening, motor housing and computer hard drive assemblies. 
• Appliance refrigerator seals, water and steam assemblies for irons, vacuum cleaner sole plates and coffee warming plate assemblies. 

The use of single and plural component dispensing equipment combined with X-Y-Z motion systems play a critical part in liquid gasketing applications. 

Their importance is directly related to the precision in size, placement and thorough mixing of the two component material used to create the gasket.

Typical two component liquid gaskets will usually have mix ratios ranging from 1:1 to 10:1. However, ratios up to 46:1 have been accomplished. When wide mix ratios are combined with bead diameters as low as 0.0625", it is critical that precise, positive displacement meter, mix and dispense equipment be considered.

The use of true positive displacement dispense valves for single component materials is also important when accurate beads are required. These systems will typically use stepper or servo motor drives and linear actuators that insure the dispensed bead holds true to size while working in direct link with the X-Y-Z motion system. 

With common dispensing speeds of 2 to 6 inches per second, a standard X-Y or three-axis X-Y-Z motion system must be designed with a high degree of precision. Some of the best systems use AC servo motor drives with precision ball screws that hold position repeatability to within 0.0008 inches. 

A good example of this effective dispensing technology involves a recent liquid gasketing (CIPG) application for the front engine plate of off-road vehicles. The application required a 0.0050" diameter liquid gasket that was 40.6" in length with a total dispense time of 20 seconds. The combination of the precision dispensing and motion systems described above made this application possible.