EDI: Fast die-gap changes

The FastGap (R) system widely used by extrusion processors to change sheet or film thickness without stopping production now yields even more extruder uptime, it was announced today by Extrusion Dies Industries, LLC (EDI).

Although the patented single-point adjustment mechanism in the standard FastGap system eliminates the need to reset the flexible-lip bolts or install an alternate lower lip with each change in product thickness, processors still must shut down lines periodically to disassemble, clean, and lubricate the FastGap mechanism. Now the new Toggle FastGap (TM) system, for which EDI last month secured another U.S. Patent (No. 6,663,375 B1), ends even this downtime.

Both standard and Toggle FastGap systems effect changes in die gap by applying force at regular intervals along the lower lip of the die in order to bend the lip. To actuate either system, the operator uses a special wrench supplied by EDI to turn an adjusting nut at one end of the die.

In standard FastGap equipment, the gap-changing mechanism consists of a stationary and a moving bar with arrays of male and female keys, respectively, set at an angle to one another so that the keys slide against one another, under considerable pressure, during gap adjustment. “The repeated metal-on-metal contact is what has made lubrication necessary,” said John A. Ulcej, executive vice president of engineering and technology. “To eliminate lubrication, we’ve replaced the old mechanism with an array of toggles along the width of the die; instead of the sliding motion of the keys, there is the rotary motion of the pins and bushings at the ends of the toggle shafts. In addition, the toggles provide greater mechanical advantage in translating the adjusting torque applied by the operator into the bending force exerted upon the lower lip.”

FastGap (R) System Triples Range of Available Die Gap Settings

Conventional dies have a fixed lower lip and a movable or flexible upper lip. The upper lip is called upon both to control the transverse thickness profile and to change the operating gap—functions which often work at cross purposes, noted Ulcej.

\’Until we developed FastGap technology, changing the operating gap required an interruption of production so that the operator could carry out a very careful manual resetting of the flex-lip bolts. If the desired new gap was outside the flex-lip range, the lower lip had to be changed to one with a larger opening.\’

A die equipped with a FastGap system on its lower lip operates on the principle of “separate lip responsibilities,” with gap adjustment carried out on the lower lip. But since adjustment of the flexible upper lip also affects the die opening, the combination of the two lip functions actually triples the available range of gap settings in comparison with a conventional die, Ulcej said. “With adjustment of the lower lip only, the die opening can be varied over a range of 0.200 in. (5.1 mm). An additional 0.100 in. (2.5 mm) is available with the top lip of the die, which controls the transverse gauge profile. Together, these capabilities increase the range of gap adjustment from the previous maximum of 0.100 in. (2.5 mm) to 0.300 in. (7.6 mm).”

The adjusting device used by the extrusion-line operator to activate the FastGap system is equipped with a micrometer-like gauge which precisely indicates gap settings. \’Selecting a specific setting is easy,” Ulcej said, “as is returning to that setting after opening the gap to clean out the die or perform other maintenance.”

The ability to make substantial changes in product thickness without stopping production is a major advantage for custom processors and other manufacturers that carry out frequent product changeovers. Companies running film and thin sheet also benefit because the FastGap system permits purging to be carried out quickly, without having to stop the line. Special FastGap systems with reduced ranges of gap settings are available for producers of thin film.

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