THERMOFORMING - Polyjohn Enterprises

CATALYTIC HEATERS ELIMINATE PRE-HEATING OVENS AND ENHANCE UNIFORMITY FOR POLYETHYLENE THERMOFORMER

PORTSMOUTH, RI -- PolyJohn Enterprises Corporation, Whiting, IN, recently converted its thermoforming operations from calrod electric heaters to Vulcan catalytic heating systems to reduce energy costs and enhance uniformity of its heating process. Vulcan's heaters have also allowed PolyJohn to eliminate the pre-heating oven on the rotary machine, providing further energy cost reductions.

PolyJohn manufactures a complete line of portable toilets for on-site sanitation services all over the world. The modular toilets, which typically measure 4' x 4' x 7', consist of three sides, roof, and door, all made of thermoformed polyethylene and riveted together.

To produce the required parts for each toilet, PolyJohn uses two different types of thermoforming machines. A double-end machine consists of a workstation on each side of the oven, one side to be used for forming, the other for heating. In addition, a rotary-fed machine consists of three rotating workstations: heating, forming, and unloading.

Conversion from the electric calrod heat source to the longwave infrared energy of Vulcan's heaters is expected to reduce the company's utility costs considerably, since Natural gas is more abundant and cost-effective in the Midwest than electricity. Vulcan's Catalytic heaters have also allowed PolyJohn to eliminate the pre-heating oven from the Rotary machine, for further reductions in energy costs.

The ideal heating temperature for polyethylene is 300°F. Even though the previous Calrod systems were equipped with sophisticated control components and percentage Timers, heating temperatures would still fluctuate within the 325° - 3500° range on a regular basis. According to PolyJohn, the Vulcan heaters rarely fluctuate at all.

In addition to increased part quality, tighter control options of the Vulcan heaters have actually simplified PolyJohn's thermoforming process. According to PolyJohn's John Camphouse, "Vulcan controls consist of nothing more than a simple gauge and ball valve. Typically, our operators just start up the system and leave it for the rest of the day - it's that simple. There's no need for the constant adjustments we had to make with the calrod heaters."

PolyJohn had also experienced environmental problems with the calrod heaters. For example, breezes or air flow from opened doors would frequently diminish the heat transfer from the calrods, causing spotting and marking of the finished parts. PolyJohn claims the flameless Vulcan heaters have been unaffected by air flow on the plant floor, thus minimizing the level of rejects and system downtime.

An additional benefit with the Vulcan heaters is that machine components are kept much cooler, and the operator workspace is more comfortable.

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