“Easy.

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Refitting a 40-mm twin-screw lab extruder with 15 zones of temperature control and data acquisition was greatly simplified with new control architecture that eliminated hundreds of wiring terminations. (Photo: RTP)

“Easy. That was the key word to describe the difference. It meant time savings and greater convenience.” The difference Matt Burt is talking about is the dramatically simplified task of refurbishing a laboratory twin-screw compounding extruder with 15 zones of temperature control and data acquisition. Major savings in time and labor were afforded by a new type of integrated control architecture that cuts down on wiring and discrete electronic components.

“We refurbish our own extruder controls a lot, but not with this kind of sophisticated capabilities,” says Burt, electrical operations manager for RTP Co., a specialty thermoplastics compounder. Last year, RTP expanded its R&D center and needed to add a new control panel to a 40-mm extruder that had no data-acquisition capabilities. Under a tight deadline to complete this project, RTP became one of the first users of a new style of temperature controls brought out last spring by Watlow under the name EZ-Zone ST (see Learn More box).

 

Snap-together controls

Unlike conventional temperature controls, for which every process loop requires six separate components that must be specified and purchased separately, EZ-Zone ST is a modular package of PID temperature controller (with continuous adaptive self-tuning standard) already connected to a 40-amp solid-state relay (SSR) power switch, plus a heat sink, current-measuring device, limit control for over-temperature protection, and mechanical contactor for safety shutdown. All these components snap together, making the package very compact and eliminating about half the usual wiring terminations. And all the components communicate with each other, making diagnostics much easier.

“We had several hundred fewer wiring connections to make,” says Burt. “Just one digital communications wire per zone, instead of 15, to the PLC touchscreen display and one to the emergency stop. It usually takes one of my technicians almost a week to wire the door for an extruder control cabinet. With these controls, we don’t have to wire a door, so we’ve saved that week. And we saved money on hardware, too, since there are fewer components to buy.”

Unlike many temperature controls, EZ-Zone systems can be purchased without the optional display. Since RTP planned to use the PLC’s display, it benefited from the EZ-Zone philosophy of “Buy only what you need.”