Manufacturers of silicone medical tubing have used gas convection ovens in the past to cure extruded silicone medical tubing. Problems often occurred during changeover from one size to another, which required moving the existing furnace to gain access to the extruding head. There were also problems with the slow response time of the furnace (over two hours) meaning excessive downtime when warming up or changing oven profiles. This long warmup/changeover time also created energy waste. In addition, the gas convection oven left manufacturers with quality issues due to limitations in the control of the existing oven.

An infrared chamber heater is the preferred solution for this process. The chamber heater mounts vertically, which means the oven does not need to be moved to access the extrusion head. The total chamber-heated length of 38" (0.9 m) is nearly one tenth as long as a gas convection oven, which opens up considerable floor space for the manufacturer.

The quality of the product also improves with the capability to add a pyrometer inline and rapidly adjust the chamber's temperature to provide consistent heating to the extrudate. Time and energy also are saved because the chamber heater's instant on/instant off feature means the warmup and changeover times are eliminated. A quartz liner option prevents out-gassed solids from collecting on the reflector. For easy cleaning, split-quartz liners that open with the chamber like a clamshell are available.

Manufacturers of braided hose have preheated the hose with low-density infrared resistance heaters. Some of the issues in this process include limited line speeds of 25 ft/min (7.6 m/min) due to the low heating density of the non-focused resistance heaters. This does not meet the required production throughput.

In addition, the heaters' high thermal mass cools slowly and continues to provide heat to the product even after the power shuts down or the product stops moving. This slow response may cause a fire when the line stops.

Many manufacturers prefer using six focused infrared chamber heaters, two of which are used prior to the extruder to preheat the raw braided silicone. Four units are mounted vertically after the extruder to cure the silicone. Manufacturers are able to increase line speeds to 80 ft/min (24.4 m/min). The line is controlled with a speed-detection system to immediately shut off the lamps in the event that the line stops. Best of all, the infrared chamber heater's even heating process and precise control improve the surface finish and reduce scrap.

Sidebar
At a Glance: IR Curing of Tubing, Hoses

An infrared chamber heater is the ideal solution to problems with preheating and curing extruded silicone medical tubing. The heater mounts vertically, so the oven does not need to be moved to access the extrusion head. Also, the total chamber-heated length is much shorter than a gas convection oven, which opens up floor space for the manufacturer.

Manufacturers of braided hose have preheated the hose with low-density infrared resistance heaters. The solution is to use six focused infrared chamber heaters, two of which are used prior to the extruder to preheat the raw braided silicone. Four units are mounted vertically after the extruder to cure the silicone. Line speeds increase with the system. The line is controlled with a speed-detection system to immediately shut off the IR lamps if the line stops. And the IR chamber heater's even heating and precise control improve surface finish.

For more information,

Contact Research Inc. Call (952) 941-3300 or visit www.researchinc.com.

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