Foaming A Seal

Foam-in-place gasket systems offers consistency and greater production.By Bill Shaw

Editor's Note: Bill Shaw is director of business development at Liquid Control Corp.

When it comes to gasketing, many manufacturers are turning toward foam-in-place systems to not only achieve greater mix consistency but also to eliminate costly downtime. Designed to replace die cut or other forms of gaskets, foam-in-place gasket systems form a weather seal to prevent the outside environment from getting in and to prevent what's inside from getting out. This technique requires the combination of precise metering (ratio and volume), controlled flow, and robotic dispense to form the exact seal profile.

Foam-in-place systems are perfect for electrical enclosures, vacuum cleaner filter gaskets, plastic pail lids, and anywhere a high-performance polyurethane gasket is required to seal products from the elements.

Reduced Downtime

The leading advantage with foam-in-place gasket systems is the reduction in production downtime. Using standard methods, gaskets are either preformed rubber rings that are hand-applied to a manufactured part, such as an electrical enclosure seal. Or, a gasket can be poured in place using polyurethane chemistry. The latter requires a meter, mix, and dispensing machine and an application vehicle – usually a robot.

The current meter, mix machine uses a dynamic mixer to mix two urethane chemicals. While a mechanical mixer provides an adequate mix, the mixer's design requires it to be flushed with a hazardous solvent after each use. Furthermore, the metering unit that accompanies the mixer uses an older control technology that requires engineering level personnel to operate.

Developing A System

To meet this challenge, Liquid Control Corp. set out to devise a system that would meet manufacturers' needs – something that would reduce downtime and also offer user-friendly controls.

The start of the solution began at Liquid Control Decker, the firm's polyurethane division. Decker introduced its patented ParaDyne mix head technology to the automotive air filter industry about three years ago. This technology is based on the ability to mix polyurethane foams with a disposable plastic dynamic/static mixer. Polyurethane foam is used to bond together the paper and metal elements of a filter.

The foam bonding application for filters is similar to the requirements for dispensing foam-in-place gaskets. Decker recognized that, by combining its ParaDyne technology and servo controlled Excell metering module with Liquid Control's C-500 automation platform, we could offer a convenient and efficient foam-in-place work cell to pour gaskets.

The system is designed to answer the urethane markets' demand for adding automation to low-pressure foam meter, mix, and dispense applications. Combining the C-500 with a Decker Excell machine fitted with a Paradyne mix head, this innovative combination delivers a turnkey process designed for applications such as gasketing, sealing, bonding, filling, and other automated dispensing needs. Offered as a complete system, the Excell 500 FIPG Work Cell eliminates the frustration engineers often experience when sourcing components individually.

Designing A Work Cell

When designing the work cell, it was important to focus on the reduction in production downtime. That's where all the pieces of the Excell 500 come together. The ParaDyne mix head does not require flushing with solvents and can continuously pour gaskets for hours before the inexpensive plastic mixer is disposed of and replaced. The older systems require going "off line" to flush the mixer. This may take 30 seconds or so about every four minutes. Assuming continuous production – with four gaskets dispensed each minute – this would relate to a production loss of 60 parts per hour or 480 parts lost per day – a significant number.

Easy-to-use controls are also essential. Since the Excell metering unit is servo controlled, it is a simple matter for the operator to set the process parameters. The C-500 is PC controlled with specially developed programming designed by Liquid Control and operates easily on the Windows format. During a recent trade show, a visitor was trained in minutes to program a profile on the C-500 robot. It's really simple.

Additionally, several profiles can be stored in the system's memory when needed. This eliminates the need to reconfigure metrics for various applications. A new profile program can be called up instantly or a new profile developed in minutes.