Extrusion.

New extrusion developments that didn't appear in the pre-show coverage include products for twin-screw PVC extrusion, blown film, and foam sheet, as well as new controls and gear pumps for a range of uses.

PIPE EXTRUSION NEWS

One example of next-generation pipe tooling came from American Maplan Corp. of McPherson, Kans. The company showed a prototype dual-spider pipe head that was roughly half as long as existing models--down from about 40 in. long for a 10-in.-diam. die set to just over 20 in. long. According to sales manager Jim Griggs, the key to maintaining a smooth ID in a such a small die is packing a "big spider volume in a small area." What's more, the spiders are interrupted or offset to reduce knit lines and thereby increase impact strength. Commercial availability is slated for the end of the year.

For conical twin-screw pipe extruders, Cincinnati Milacron showed a new pre-heating system that sits atop the main extruder. This CM-140 unit is itself a corotating twin-screw device; however, it preheats material without melting it. It's said to provide 25-30% increases in extrusion of powder, pellets, or regrind at rates from 50 to 3000 lb/hr. Price is in the range of $35,000-50,000.

Also new for conical twin-screw machines, Conforma Clad of Melbourne, Fla., announced a new line of aftermarket barrels. In particular, the company is reportedly the first to offer aftermarket conical barrels with tungsten carbide liners. Marketing director Pat Bhave says these bimetallic barrels will last up to three times longer than conventional nitrided barrels while costing about twice as much.

FROST-LINE CONTROL

In blown film, two new systems aim at maintaining a constant frost-line height in order to achieve consistent film properties. One of them is a prototype of a patent-pending "mass air-flow sensor" from D.R. Joseph Inc. of Arlington, Texas. According to Dan Joseph, the device not only measures flow but also senses the density of the air. In doing so, it takes into account temperature, humidity, and barometric pressure--environmental conditions that can cause shifts in frost-line height during the processing day. Joseph's bell-shaped sensor samples the air just before its entry through the air-ring or IBC distribution system. Depending on how the blown film line is outfitted, the system triggers adjustments in chilled-air systems, changes in blower speed, or water injection to cool and densify the air.

Joseph envisions the system in both laboratory and production settings as a repeatable set-up tool. At the beginning of a run, operators pick an optimum cooling rate, as revealed by the frost line, and punch the numbers into the system's computer. After that, "the system holds the frost line," Joseph claims. Commercial availability is slated for the end of the year.

Second, Alpine American of Natick, Mass, showed off its new Frost Line Control System. This system uses an ultrasonic sensor to detect changes in bubble shape--and, by extension, the frost line--from distance measurements. It, too, is a set-up tool. Users manually set conditions to produce a desired bubble at the beginning of the run. The system then maintains that "shape" by controlling IBC air.

For foam sheet, Sencorp Systems Inc. of Hyannis, Mass., showed a new die that permits on-the-fly adjustments of the die gap. Thanks to a crank-driven reduction gear, the inner die lip can be changed while the system is running without disturbing the process. The die also allows concentricity adjustment though a radial set of thermally actuated bolts.

Davis-Standard of Pawcatuck, Conn., introduced a new way to control temperature with its Epic II and System 501 controllers. Employing a rule-based approach to eliminating temperature overshoot and undershoot, this Adaptive Reset feature works by first "memorizing" each barrel zone's load compensation at various screw speeds. Or, as technical director William Kramer explains, Adaptive Reset creates a reset model for the range of screw speeds. During subsequent runs, the system retunes itself, applying appropriate resets without any delay--unlike earlier controllers that wait for stability before applying a correction. The bottom line, according to Kramer, is the ability to reach temperature stability about a third faster.

Among the auxiliary equipment news, LCI Corp. of Charlotte, N.C., introduced a new mounting arrangement for its gear pumps. The new configuration couples the pump directly to its drive, and both components hang on the end of a retractable three-hinged arm. This way, users can pull the pump off-line for maintenance without disturbing any upstream or downstream equipment.