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Meter Mix Dispensing Reduces Production Time and Cost
Dispensing epoxy potting on the production line.
By David Upton, Director of Marketing, FRC-Fluid Research Corporation, Tustin, CA
Precisely applying today's epoxy, silicone and urethane-based adhesives and sealants require the proper meter mix and dispensing process. Material manufacturers are constantly selling their formulations based on the benefits that they provide, and rely on their customers to properly identify and apply formulations, whether for potting/encapsulation or adhesion.
Key to the process — for contract manufacturers and OEMs alike — is reducing labor and material costs, as well as waste. This is accomplished by using a dispensing system that meets these criteria. It is important to replace the time-consuming manual-mixing procedures with equipment designed to precisely meter, mix and dispense materials. This provides manufacturers with an accurate, time-saving, and ultimately cost-saving dispensing method.
The reasons for potting and encapsulating are endless. Potting and encapsulation is frequently used to protect a proprietary technology by completely covering an assembly in black epoxy resin — making it impossible to reverse engineer without damaging the proprietary component.
The potting operation is performed by pouring a polymeric material into an electronic device, totally submersing and protecting the internal parts. The outer shell of the device holds the potting compound in place until it hardens.
A two-part formulation is used to protect circuit boards and components from harsh conditions, such as moisture, high/low temperatures, and physical or electrical stress.
Encapsulation requires a mold to hold the device that is to be protected. Then the polymeric material is injected to completely fill the mold. The device then takes on the shape of the mold after the compound hardens. Potting or encapsulating with a filler can modify dielectric strength, dissipate heat, allow the product to float in conjunction with waterproofing, and depending on the type of compound used, adds flexibility or rigidity to the product. Potting and encapsulating are two of the most popular applications for FRC's multi-component dispensing equipment. It is a common belief that everything in this world either contains a potted/encapsulated part or was made from a machine that contains a potted/encapsulated part. FRC Fluid Research Corporation has been at the forefront of this process for over 15 years, developing meter mix dispensing solutions to meet these often challenging requirements, specially designing systems to meet the needs of both customers and materials manufacturers.
Critical aspects of a two-part dispensing system are its shot-size accuracy and range, with a predictable adjustable flow rate and consistent ratios, to create a very repeatable process. When utilizing a precision two-part dispensing system from FRC, technicians can program the ratio, flow rate and quantity of the potting compound to be dispensed by using the system's LCD touch panel. The circuit board is then placed under the dispensing machine's static-mixing nozzle, and the technician simply depresses a foot switch to release the programmed amount. A computer-based system allows fast setup, and operators can adjust and store multiple flow rates, mix ratios and even entire dispensing cycles. The optically encoded servo drives and microprocessor-controlled hardware are driven by the company's programming technology that delivers extremely accurate and repeatable shots.
After components are mixed in a static mixer, the positive shutoff valves prevent cured material from clogging the lines. Further, because dynamic shaft seals are not required — because of FRC's use of a progressive-cavity design — valve wear, leakage and potential phasing errors that are common in piston-pump systems, are eliminated. This equipment replaces labor-intensive procedures that ordinarily require manual mixing and dispensing of the potting compound. Without an automated, precision meter mix dispensing system, companies must buy potting material in kits where the resin and catalyst must be mixed by hand. Operators then manually mix the material in the kits and then dispense into the units to be potted, generating a significant amount of additional waste. The cost of buying the material in kits, plus the labor involved, can also be very high.
N-2000 meters, mixes and applies potting mix.
It has been estimated that an automated precision dispensing system pays for itself in roughly one year for an average user. In addition, companies can purchase materials in larger 55-gallon kits, allowing the equipment to handle all mixing and metering chores, further reducing costs, and speeding ROI (return on investment).
The amount of material, dispense time, flow rate and ratio can all be adjusted from a keypad with LCD interface. A microprocessor is programmed, at ratio, to turn the pumps for the selected dispense volume and can save a number of programs of different parameter settings for quick transfer between applications requiring different volumes of material. Highly accurate signal-to-action timing enables consistent and repeatable deliveries of material. With the machine's shot-size accuracy and range, adjustable flow rate and predictable, consistent ratios, a very repeatable process can be expected in production. The dispense equipment should integrate into most commercially available robotic systems.
Flexible Digital Control
The addition of flexible digitally controlled meter mix systems, built around a workstation format, allows the user to utilize the positive displacement pump technology that is especially suitable for medium-to-high volume dispensing requirements, through proprietary microprocessor programming controls. These systems are capable of up to 40 stored dispense programs, and offer the lowest maintenance requirements available in the industry, resulting in a lower cost of ownership compared to competitive systems.
FRC's systems are specifically engineered to accurately meter plural-component adhesives and sealants, regardless of viscosity, and feature programmable ratio, dispense volume and flow rate. Traditionally dispense equipment is thought of as being configured with piston or metering rod displacement pumps or gear pumps. Each of these styles of pumps have been used because of their specific delivery capability however each of these designs have high wear rates when used to pump moderately to highly filled or abrasive materials.
The utilization of progressive cavity pumps provides an excellent vehicle for dispensing a wide variety of materials. Progressive cavity pumps have an internal helix-shaped rotating element called the
and a double-helix shaped stationary external element called the
. The interference fit between rotor and stator creates a series of sealed cavities. These cavities are continually filled with material at the pump assembly inlet, and gently move the material, relatively undisturbed, to the pump outlet. The effective result: solid materials that are smaller than the cavity size can be dispensed without damage either to the materials or the pump, making the PC pump the correct choice to be used with abrasive fillers without undue wear. The amount of wear, of course, is equal to the size, composition, and percentage of filler present in the material over the time span in which the pump is in use. Fillers as fragile as glass micro balloons, to as destructive as sand, are processed equally as successfully with the PC Pump. When wear occurs, ratios will drift slightly, but due to the technology driving the pumps, this wear can be compensated for by a simple recalibration of the system. This extends the life of the pump, providing continued uptime of the system in actual production. Conversely, in other systems that use pistons, if a seal on a piston or metering rod fails, the system is likely to go down and leak material into the production area.
Variety of Fluid Media
The use of progressive cavity metering pumps delivers precise, consistent and reliable dispensing of a wide variety of fluid media. Accurate precision dispensing is achieved independent of media viscosity. PC pumps exhibit exceptional resistance to abrasive/filled content and chemically aggressive fluids. Suitable for single or multi-component applications, PC pumps provide a multitude of operational advantages, including constant volume at variable speeds, continuous flow, few moving parts, low maintenance and no cycle time delays for cavity recharge. Specific design features of progressive cavity pumps provide additional functional benefits. The cavities taper down toward their ends and overlap with their neighbors, essentially eliminating flow pulsation. No flow meter or check valves are required due to the seal design of progressive cavity pumps.
Ultimately, the resulting performance of a meter mix dispense system is a driving factor in the success of any business that relies on accurate controlled dispensing. When considering the options available in meter mix dispense equipment, the benefits of advanced microprocessor controlled features, combined with PC pump technology, offer manufacturers a flexible and powerful material management solution.
Contact: FRC — Fluid Research Corporation, 15775 Gateway Circle, Tustin, CA 92780
714-258-2350 fax: 714-258-2352 firstname.lastname@example.org Web:
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