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Oven Amperage Draw

Take the total number of heaters times the watts per heater, will give you the watts per oven, divide this number by the voltage, will give you the single phase amperage, divide this number by the phase factor (1.73) to get three phase amperage.

Heat requirements for materials will vary depending on its ability to absorb infrared waves.

Tubular

Tough, long lasting, used on many types of machinery. Thermocouple can be either welded or, we suggest, clamped to an individual rod for control. Cal rods are normally placed on 2, 3 or 4 inch centers. Rod identity (watts, volts) are stamped into each rod, look near the end, its sometimes hard to see.
Heated length starts about 2 to 3 inches from the end of each rod. Screws to hold wire ends, and the wire ends themselves, are of a high temperature material. Elements can be bent but use gentle curves.

Ceramic
Flat or Curved

Normally:
15 to 17 watts per square inch is required for thermoforming most plastic sheets.
650 watts per heater, 3 heaters per square foot.
Oven size should be one foot larger than mold.

To figure number of heaters required:
Oven size in square inches, times, the watts per square inch required, divide by the wattage of the heaters to be used, this will equal the number of heaters required.
(30x36 = 1080 x 16 watts per square inch = 17,280 divided by 400 watt heater = 43.2 elements required

Flat elements evenly distribute heat at a distance of 1 to 4 inches and are usually used when even heat patterns are required. Thin plastics and drying or curing applications where an uneven pattern may exhibit streaking.
Curved elements are usually the choice for all types of plastic heating applications. Normally placed at a distance of 4 to 8 inches away from most sheet. Their parabolic curved surface adds strength to the element while providing a very suitable heat profile.

Heaters come in a variety of colors, Black, Yellow, White and Coral or Rose, except for Black which is "not" recommended for use in thermoforming, color is a customer preference, there is no efficiency difference. Wire leads come in 3", 6" and 9" lengths. We stock mostly the 6" but have some 9" as well. Wires are terminated with "Pin" connectors but rings can be added if required.
Elements come in 9.65 and 4.80 lengths x 2.36 wide. Cast in thermocouple is available in K or J style.
Color changing heaters come in Coral and Yellow and change to Brown or Grey when hot.

Panel

Infrared heat given off similar to ceramic with cloth or glass face. infrared wave length is most efficient at 7 to 8 inches from sheet line.
Panel heaters with a metal face are slightly more efficient than cal rod heaters. Cloth face heaters are typically used on top and glass or metal faced are used on the bottom.
Panel heaters are better than ceramic heaters in that the heater can be easily cleaned in case of a dropped sheet of plastic, however, replacement of a burned out heater is often expensive and the larger area that panel heaters occupy does not allow for as tight of profile as ceramic.

Quartz

Quartz heaters include medium wave infrared emitters. Infrared emissions are similar to ceramic or panel heaters. Start up or heat up time is much quicker than ceramic. Emitters can be small diameter array in a reflective housing  similar in size to ceramic 3x9 or 3x5 in 5/8  or 3/4 inch tubes.
Newer to thermoforming are the short wave tungsten quartz tubes and the white light halogen quartz. These short wave quartz tubes should be built into a panel with reflectors and cooling units due to their extreme heat output and their fragile nature. Their connectors tend to burn out quickly if not cooled.
Although the medium wave quartz is suitable to most types of thermoforming its draw back is the fragile nature of the quartz glass. The short wave quartz are becoming widely used in some heavy gauge applications but are not suited to all types of plastic.

Thermocouples

"J" type thermocouple measure 0 - 900 degree F. and are coded with red and white wires.
"K" type thermocouple measure 0 - 2000 degree F. and are coded with red and Yellow wires.

TPS inc.
ph 800-722-2997    989-435-3800
fax 989-435-3825
email:  tps@ejourney.com
www.thermoformerparts.com

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