System Provides Precision Foam-in-Place Gasketing

 

High-tech precision dispensing equipment and a new, two-component silicone material have teamed up to create cutting-edge gasketing techniques. High production rate applications in a variety of industries, including automotive, electronics, appliance, airframe/aerospace and packaging, are driving this new process.

Examples of FIPG components Nearly two years ago, Sealant Equipment & Engineering (SEE), identified a need created by Dow Corning to develop an automated dispensing system for their new Thixotropic 3-8186 silicone foam for Dispensing Foam Gasket (DFG) applications. Eighteen months later, the partnership has drastically improved the development and use of foamed-in-place gaskets.

DFG gasket material, coupled with the Program-A-Bead 995 meter/mix/dispensing system, will displace conventional, time-consuming, manual gasketing methods. Die-cut taped foam gaskets and preformed rubber gaskets cannot compare in cost or quality to the new silicone foam gaskets

DFG gasket material, coupled with the Program-A-Bead 995 meter/mix/dispensing system, will displace conventional, time-consuming, manual gasketing methods. Die-cut taped foam gaskets and preformed rubber gaskets cannot compare in cost or quality to the new silicone foam gasketsProgram-A-Bead 995 system showing two gear meters and hand held dispense valve

The silicone is transformed from its liquid state to the desired cell structure foam product by exacting proportioning and then thoroughly mixing the two components. The extruded silicone foam then expands and cures in 10 min at 75°C -- Ready for use or shipment.

The DFG silicone material must be dispensed at a precisely controlled, mixed material flow rate. A programmable robot or XYZ table will control the dispense valve nozzle / tip speed used to apply a predetermined bead of silicone foam around the surface for a subject work piece, and hence the foam gasket geometry being dispensed is solely generated by the programmable motion control equipment in a non-synchronized manner.

Challenges and Solutions

Precisely metering and mixing the 1:1 parts by weight material to create the proper foam cell structure was one requirement in developing this dispensing process. Another factor during the design stages was that the mixed material must be dispensed at a constant flow rate. The silicone gasket must be dispensed quickly, accurately and continuously to meet the most demanding product applications.

These application requirements were SEE's primary challenges. They needed to design and manufacture equipment that would, at aggressive productions rates, precisely meter, mix and dispense the silicone to ensure the foaming property and control the dispense rate to vary the size of the foamed-in-place gasket without interruption. SeeFoam Multi-Path Static Mixing Dispense ValveThe Program-A-Bead 995 emerged as the system able to respond to the multiple demands of the material and application process.

At the heart of the system are the two positive displacement, precision gear metering pumps with integrated electronic controls. The variable ratio, servo-driven, gear-metering pumps can be controlled separately and jointly, providing flexibility. The independent control allows the silicone to be metered at ratios other than the standard 1:1 (for use with other materials).

While exact ratio proportion is essential, thorough and efficient mixing is critical to ensure the even cell structure of the silicone foam. The equipment's mixing is accomplished with the SeeFoam, a compact, motionless, multi-path, static mixing system that guarantees that the two material components are thoroughly blended. The dispense valve and multipath mixer eliminate the need for a costly and high-maintenance dynamic-style power mixer.

An integrated base purge feature eliminates the need for solvent flushing and eliminates the disposal of hazardous waste materials. The No-Drip® / Snuf-Bak™ design of the dispense valve assures that the material will not drip or leak from the outlet when it is shut off.

The SeeFoam Dispense Valve is commonly fixtured in a wrist of a multi-axis robot and then positioned over the work piece. The robot controller is programmed to send an output signal to the Program-A-Bead dispense system to control the on/off of the dispense valve nozzle / tip. By using the positive displacement, servo-driven, gear metering pumps, the dispense process is surge- and pulse-free, which ensures that the foam gasket is consistentlyGear Meter from Program-A-Bead 995 sized throughout the desired bead path.

System Advantages

There are numerous benefits from this marriage between the DFG material and the Program-A-Bead 995. First, the completely automated process ensures exactly proportioned mixing while meeting aggressive manufacturing schedules. In addition, the system provided precision dispensing that eliminates any quality assurance concerns, and because the dispensing process is program controlled, consistency is ensured. Furthermore, since the process drastically reduces waste, labour and other related costs, these savings are realised.