Igloo - Thermoforming Retrofit

 Igloo, a leading Igloo of deep-draw ice chest liners recently converted to catalytic heating with two retrofits from Vulcan Catalytic Systems of Portsmouth, Rl.

Igloo's interest in Vulcan arose after a succession of fires caused by  dropped plastic sheets resulted in the evacuation of the thermoforming department. The company's manufacturing manager had read an article in a plastics magazine about the safety features of flameless catalytic heating, and passed the information on to the engineering department and the plant maintenance manager.

While the catalytic heating system's fire prevention benefits and potential energy savings sounded attractive, the company's process people had questions about how the heaters would work with ice chest liners—thin‑walled, deep‑draw products that are pre‑blown during the plug‑assist forming cycle.

Because the emission characteristics of the catalytic heaters closely matched the broader long‑wave absorption range of the plastic sheet, the sheet would be heated to the core. As a result, there would be less temperature difference between the two sheet surfaces and the core, resulting in even material distribution during the forming process.

In the preheat oven, the company uses a four‑station Brown rotary with bottom heat only. For the main oven, it uses full heaters, that is, top and bottom. There are 15 zones to control all the heaters in the system. The degree of infrared is determined by the gas pressure for a particular heater. The maximum pressure is 3‑1/2 inches W.C., with the lowest being 3/4 inch W.C. The operator typically adjusts the pressure settings from a setup sheet. Minimal adjustments are required once a machine is operating.

The two initial installations became the thermoformers of choice for the operators of the difficult‑to‑mold ice chest liners. Cost considerations required that the liners be formed with the thinnest sheet possible.

Approximate sheet size on the chest liners is  27 inches by 50 inches, with a thickness of .187 inches. The sheet receives its heat from a total of twelve zones. The inner zones operate at about the mid‑range of pressure control, while the perimeter zones operate at a higher output.

Immediately after the two installations, Igloo achieved a 20 percent increase in production from each thermoformer. On one machine, the catalyst replaced pre-heat elements with variable reflectors. On the other, it replaced ceramic heaters.

Typically, operators perform the majority of secondary trimming and attachment operations. Because of the faster cycle times, operators became overburdened and the post-finishing operations have required greater automation. To ease this crunch, the company is planning to install automated trimming equipment. Once this equipment is installed, the heaters will be turned up higher to produce even faster cycle times.

Meanwhile, Igloo’s experience with natural gas-fired catalytic heating has led to some additional investment.

“Two more retrofits are on order, a clear indication of a convinced customer,” says Mike Chapman, managing director of Vulcan. “This company has demonstrated over the past twelve months that catalyltic heaters have positively impacted their bottom line.”

 This article was reprinted with the permission from the American Gas Association (A.G.A.) Arlington, VA. It first appeared in the “Process Equipment for the Plastics/Polymer Industry” special issue of Gas Technology, an educational
supplement which has been inserted in Modern Plastics and other publications.

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