Meter/Mix/Dispense System Meets Critical Mix Ratios in Abrasive Urethane Application

October 10, 2000
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The right tool for a task not only gets the job done – it gets it done better and faster. It is no different with dispensing equipment. The right dispense system can turn ideas into product and productivity into profit.

Dispensing two-part polyurethanes is a key element in Pleatco’s production. Pleatco, located in New York, is a leading manufacturer of replacement water filters for use in spas, pools and Jacuzzi® whirlpools. Pleatco’s replacement cartridges are available for over 60 different manufacturers. All in all, there are over 200 different models.

Making the filters to meet demanding specifications, yet cost effectively, is a manufacturing necessity. Pleatco relies on its chief operating officer, Lenny Kott, to produce top-quality, uniquely designed filters to satisfy demanding manufacturing requirements while controlling production costs. Kott is in charge of production and filter design. His experience has positioned Pleatco at the forefront of spa filter manufacturers.

In production, reliability is a must. You can’t make a filter if the dispense machine is down. To Kott, the See-Flo 7 meter/mix/dispense system from Sealant Equipment & Engineering is a “beautiful thing” because its reliability, coupled with its flexibility, gives him the tool to make the Pleatco filters.

The Polyurethane Formulations

The different polyurethane formulations that Pleatco uses to produce end caps for filters are chlorine-resistant and color-coded. The polyurethane curing systems require different mix ratios (6:1 to 2:1) to produce end caps with different physical properties. The polyurethane ratio is changed to match the filter properties and to maximize curability.

The Manufacturing Process

The filters are made in a variety of sizes from a pleated media – a thick, polyester-type fabric. At each end of the pleated material is the base. The base fixes the pleating in position and allows the unit to become a filter. While other filters have a separate metal or plastic end cap into which the polyurethane and pleating are placed, Pleatco molds the entire end cap from polyurethane. The polymer seals each end cap and becomes a permanent part of the filter. And into the molded cap Pleatco includes several other user-friendly features.

Filter Design and Manufacturing

For some models, Pleatco’s patented design incorporates threads and a handle into the end cap, making it easy for the customer to replace the reusable core or to attach the filter to his or her water-purification system. Some of the filters include disinfectants in the cartridge core.

To manufacture the filter, the mixed urethane is dispensed into a mold and the pleating is inserted. The uncured urethane wicks up the pleating as it hardens to form a tight seal to all parts of the pleating. After a short cure time, the hardened end cap is formed from the urethane, sealing the end of the filter while providing support for the pleating. A release agent allows the assembly to be quickly separated from the mold.

Processing the urethane with a short cure time to achieve the rugged properties of the end cap is the result of years of research and work by Kott, a self-taught expert on dispensing urethanes. “Different filters demand different urethanes,” he notes. “To achieve various degrees of hardness, you use different mix ratios. And the filters have a complex design,” he says, referring to Pleatco’s patent on the filter. The precisely mixed urethane allows Pleatco to mold the versatile and unique end caps.

The Dispensing Equipment

Pleatco exclusively uses See-Flo 7 systems to meter, mix and dispense the urethane formulations. “One of the beautiful things about the machine,” says Kott, “is its flexibility. I bought the machine to process entirely different ratios. But since we no longer use that formulation, all we had to do to retool was change the position of the isocyanate volumetric cylinder.”

High-Volume Use

The dispense systems earn their keep since Pleatco manufactures thousands of filters. With two shifts a day during the peak season, the two See-Flo 7 systems in production provide around-the-clock reliability. In terms of volume, Pleatco estimates it uses 4,500 pounds of polyurethane each week.

Easy Ratio Adjustment

Going from one ratio to another is an easy manual adjustment. To change the mix ratio, one of the metering cylinders is simply repositioned and locked in position. With a couple of checks to verify the mix ratio, the system is ready to begin dispensing a different formula.

Kott says, “Using these machines, I can run six or seven different formulations without having to purchase a new machine. This means the least amount of capital outlay without having to go to the expense of buying new machines.”

Different Shot Sizes

Different filters require different amounts of mixed polyurethane. In order to remain consistent, controls on Pleatco’s See-Flo 7 units permit them to dispense exactly the same amount – or shot – of mixed material each time the system is actuated. Changing the shot size is another simple adjustment.

Because all changes are manual (locked with physical hard stops), there in no need to tweak a drive motor, check a digital readout or make speed/motor compensations for wear. The position of the metering pump determines the ratio, and it is consistent and precise. The system’s off-line ratio check verifies the mix ratio. The ratio check can be done at any time without interrupting production.

Past Experience

The See-Flo 7 was not Pleatco’s first dispensing system. Problems with prior equipment limited production and required lengthy downtime in order to change ratios. That, coupled with the abrasive nature of the filled urethanes, meant considerable maintenance and little flexibility. Pleatco’s first dispense systems were single-acting. “That,” says Kott, “limits production. The double-acting cylinders of the See-Flo 7 eliminate a reload pause between one end cap and the next. With the See-Flo 7, dispensing is continuous. You can move from one part to another as quickly as you can dispense.”

Exact Mix Ratios

“The See-Flo 7 system precisely dispenses the two components I need to make a polyurethane end cap to the filter,” Kott explains. “In my case, it’s critical that the mix is to the exact ratio or it’s no good. The See-Flo 7 also provides me with good cures from low (volume) to large shot sizes. Generally, with variable ratio you’re not able to do this, but I can with this piece of equipment.”

Dispensing is flexible. It can be used for either large or small filters because the See-Flo 7 is a double-acting system – there is no reload necessary. With production of filters increasing each day, Pleatco would have needed several of the single-acting systems to meet production.

Maintenance and downtime are day-to-day issues with a filled material. Wear on internal components results in a poor mix ratio that can turn the filters into pure scrap. With the metering pump design of the See-Flo 7, the exact mix ratio is assured. The hardened internal components minimize the wear from a filled formulation. The meter cylinder includes dual sets of multiple adjustable packing, thereby reducing the abrasive effect of filled material. This, in turn, translates into higher productivity.

Another positive feature of the See-Flo 7 is that it is not affected by temperature. If the viscosity of the urethane rises in the cooler months, the system will still dispense the same exact volume. The positive displacement and balanced design of the metering cylinders assure accuracy all the time.

System Versatility

The system’s versatility extends even further. Chris Schultz, service manager for Sealant Equipment, notes, “By using different metering pumps, you can easily hit ratios from 1:1 to over 20:1 with no other changes, just the pump.” With over seven different positive-displacement pumps, the See-Flo 7 is capable of handling an extremely broad range of volumetric mix ratios and viscosities.

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