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February 1, 2000

2 Min Read
Mold Temperature Controller Design Prevents 'O' Ring Leaks

Mold Temperature Controller Design Prevents 'O' Ring Leaks

The design of Logic Corp.'s Merlinopen-loop, negative-pressure moldtemperature controller is said toprevent leaks from developing in 'O' rings. It is a step up from the manufacturer's Logic Seal product, which was designed to prevent leaks fromoccurring only after a leak had developed from 'O' rings or from a break in the mold.

The Merlin has a patented flow circuit that not only controls temperature up to 180 F with ± 1° F accuracy but also controls the pressure on the mold. This is said to prevent mold leaks caused by other mold heaters that put high and fluctuating pressure on molds and leads to mold downtime and repair.

Logic Corp.'s Paul Allen explains: "Look at a typical open-loop temperature control unit and follow the flow. If you have a drain of 20 psi and a supply of 80 psi, the pressure going into the pump is 80 psi. If the pump adds 50 psi, the pressure going to the mold becomes 130 psi and the pressure coming back is 80 psi. When cooling takes place, the pressure coming back from the mold drops to the drain pressure of 20 psi.

"With the Merlin, the supply pressure does not go to the pump, it goes to the drain and you adjust the drain with a pressure-relief valve. Let's look at 80 psi supply and 20 psi drain. You want a 50 psi differential across the mold, so you set the pressure relief valve to add 20 psi, the drain will equal 40 psi, the 40 psi becomes the output of the pump and the pressure from the mold is -10 psi or about 20 HG."

The Merlin is said to be ideal for all molds that have 'O' rings, particularly unscrewing molds. The water pressure on the 'O' ring is set as low as the drain pressure and because it does not fluctuate between heating and cooling, leaks can't occur, Allen says.

There are nine models currently available, with capacities from 7 to 52 gal/min. Allen says the company will build custom units, as well. The models come with 3.4 kw heater elements and pressure differentials from 50 to 150 psi. A 10 gal/min Merlin is priced at $3450.

Logic Corp.
Sandy Hook, CT

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