What Types of Heaters are used in Plastic Injection Molding?

Posted On December 06, 2023 by Melissa Lopez-Barnes


In plastic injection molding, various types of heaters are used to heat the molds and other components of the molding machine. These heaters play a critical role in maintaining the proper temperature of the mold and the plastic material.

Today we’re discussing several of the common types of heaters used in plastic injection molding.

Band Heaters

Band heaters are one of the most common types of heaters used in injection molding. They consist of a metal band or strip that wraps around the barrel of the injection molding machine. Band heaters are designed to provide uniform and consistent heating to the barrel, ensuring that the plastic material is properly melted and injected into the mold. The primary role of band heaters is to ensure uniform and consistent heating of the plastic resin within the barrel.

Importance: Proper barrel temperature is crucial for melting the plastic resin, allowing it to flow smoothly and fill the mold cavities accurately. Inconsistent heating can lead to defects in the molded parts.


Cartridge Heaters

Cartridge heaters are small, cylindrical heating elements that are inserted into holes drilled into the mold. They are often used for heating the nozzles and sprue bushings, where the plastic material enters the mold. Cartridge heaters are known for their fast-heating response and precise temperature control. They are responsible for localized heating and maintaining precise temperatures in critical areas of the injection molding process.

Importance: Cartridge heaters offer rapid response and temperature control. They ensure that the plastic material remains at the correct temperature as it enters the mold, promoting uniform filling and reducing the risk of defects.


Coil Heaters: Coil heaters are compact and flexible heating elements that are often used in hot runner systems, where they are placed directly in the runner channels or nozzle tips. They can be bent to fit the shape of the mold, providing efficient and even heating to the individual cavities of the mold. Their role is to provide focused and efficient heating to maintain the desired temperature of the molten plastic.

Importance: In hot runner systems, coil heaters prevent premature solidification of the plastic material in the runner channels. This ensures that the plastic flows smoothly into the mold cavities, reducing the chance of defects like flow lines.


Mica Strip Heaters

Strip heaters are flat, rectangular-shaped heating elements that are mounted to the mold or other components of the injection molding machine. They are commonly used for applications that require uniform heating across a larger surface area, such as the platens in the molding  machine.

Importance: Strip heaters are crucial for achieving consistent mold temperatures. They are often used to heat the platens that hold the mold halves together. Proper mold temperature control helps reduce warping, internal stress, and cycle time.


Ceramic Strip Heaters

Ceramic heaters are known for their high-temperature capabilities and durability. They are often used in applications that require extremely high mold temperatures, such as in the production of certain types of plastics or specialized processes. They can be inserted into the mold to ensure the plastic material remains at an elevated temperature.

Importance: For specific applications, maintaining high mold temperatures is critical to the quality and performance of the molded parts. Ceramic heaters ensure that the mold remains at the desired temperature throughout the injection molding cycle.


Efficient and Consistent Heat

These heaters collectively contribute to the efficiency and consistency of the plastic injection molding process. They play a vital role in ensuring that the plastic material is properly melted, injected into the mold, and solidified to produce high-quality molded parts. The precise control they offer helps reduce defects and ensures the final products meet the desired specifications.

The choice of heater type depends on the specific requirements of the injection molding process, including the type of plastic being used, the desired mold temperature, and the design of the mold and machine. Proper temperature control is essential in achieving high-quality and consistent results in plastic injection molding.


Backer Marathon Heating Solutions


Band Heaters

When heating is required around a nozzle or a pipe, a band heater is the optimal solution for your heating needs. Our current band products are separated in two types: mica band heaters and Starflex band heaters. Each type offers different temperature tolerances as well as flexibility and construction options.

Our band heaters are computer designed and manufactured to your specifications. Only the highest quality materials are used for optimal performance. Backer Marathon’s stock band heater inventory is constantly growing. We stock a wide variety of heaters right on the shelf that are available for same-day shipping.


Band Heater Features:

  • High-temperature oxidation-resistant metal sheath
  • Highest grade mica insulation provides excellent electrical insulation at high temperatures and is resistant to moisture
  • Clamping band is low thermal expansion stainless-steel construction designed to maintain clamping pressure at elevated temperatures
  • Nickel/chromium resistance wire evenly wound for uniform heat distribution and reliable accuracy
  • Standard 10” fiberglass leadwires are UL rated and provide protection up to 850°F
  • Approximately 1/8” thick


Starflex Band Heaters

Backer Marathon Starflex is the most rugged, reliable band heater available. Starflex band heaters are the original aluminum body band and are still the industry standard. These heaters are manufactured by hydraulically pressing a high-temperature heating element into a precision-grooved aluminum channel. The heaters are clamped in place with low-expansion stainless-steel straps for intimate contact with the part. The aluminum channel offers low-mass and high-thermal conductivity for fast heat up. These same characteristics provide excellent cool down properties as well. Starflex bands are also available with water cooling, both as a cool-only band and a heat/cool band.

They are used on extruders, injection molding barrels, blown film dies, and other applications requiring rugged, long-life heaters. Heaters open completely, allowing easy installation and eliminating the need to remove other items from the barrel. You get the durability of a cast-in heater at a fraction of the cost. They are replaceable, unlike cast in heaters that require replacement of the whole heater.


Starflex Band Heater Specifications:

•   Maximum operating temperature: 650°F

•   Maximum voltage: 277 volts per half

•   Maximum amps: 30 amps

•   Wattage Tolerance: +5%, -10%

•   Maximum recommended watt density: 40 watts per square inch

•   Maximum diameter: 10 feet

We offer prompt service at competitive prices, a three-day expedited service on custom designs, and there is never a minimum order requirement.


Cartridge Heaters

Backer Marathon is a leading manufacturer of American made high-watt density cartridge heaters. Our HotRod stainless-steel heaters are the industry standard and offer quality construction, superior heat transfer, and long-life heating solutions up to 1600°F—typically exceeding the performance and durability of others in the market.

Through refinements in the swaging process, specially designed cores, careful selection of magnesium oxide fill, nickel chromium resistance wire, stainless-steel tubing, and carefully controlled production processes, HotRods routinely outperform other cartridge heaters in difficult applications. They are available in a wide variety of diameters and configurations. In addition to our swaged heaters, we offer non-swaged heaters for applications up to 800°F, as well as square heaters for milled slot solutions.

Choose from our thousands of in-stock heaters for immediate delivery or let the engineers at Backer Marathon design a custom heater for your unique application. Standard manufacturing times are normally less than two weeks.


Cartridge Heater Features:

  • High-temperature lead wires for temperatures up to 550°C
  • High-impact ceramic cap retards contamination and is suitable for high-vibration applications
  • Deep holes in cap prevent fraying of leads when bent
  • Nickel/chromium-resistance wire for maximum heater life, evenly wound for even heat distribution
  • High purity magnesium oxide fill selected for maximum dielectric strength and thermal conductivity; highly compacted for maximum heat transfer
  • 304 stainless-steel sheath for oxidation resistance in a wide variety of environments; 316 stainless steel and Incoloy® are also available
  • TIG-welded end disc to prevent contamination and moisture absorption
  • HotRods are UL recognized, File #E202904; and RoHS compliant

If you have questions about OEM cartridge or replacement cartridge heaters, please contact us.


Coil Heaters

When highly focused heat is required, and a very low profile is imperative, coil heaters are the best cost-effective option. Coil heaters may be used to concentrate the heat on specific segments, or the coil may be spread to equalize the temperature across the object to be heated. Heaters can normally be coiled and shipped in one working day.


Standard Coil Heater Features Include:

  • Internal Type J and Type K thermocouples are available for precise temperature control
  • .130 square cross section is standard
  • Other lead arrangements are available
  • Teflon power leads
  • Stainless-steel braid with ground wire
  • Stainless-steel sheath
  • Nickel chromium resistance wire with highly compacted MgO fill
  • Seal-welded end

Coil lengths are based on a closed coil. Coils can be stretched for distributed wattage and/or much longer coil lengths.

  • Sizes are based on a 1.18” extension length
  • All heaters are 240V
  • All heaters have 36” leads with stainless-steel overbraid and a ground wire
  • Heaters are available with and without thermocouple
  • All heaters are .13” x .13” square cross section


Strip Heaters

Backer Marathon strip heaters are manufactured to your custom specifications. Mica strip heaters offer a low-profile option for applications of up to 1200°F. Our mica strip heaters are only .156” thick and ideal for plate heating applications. Backer Marathon strip heaters will operate up 900°F or to 1200°F with an optional stainless-steel sheath. This thin, low-mass construction provides fast heat up times.


Mica Strip Heater Specifications:

  • Minimum length: 2.5” (consult sales department for maximum)
  • Minimum width: 3/4”
  • Standard thickness: .156”
  • Fold Over: 1/4”
  • Maximum sheath temperature: 900°F/482°C
  • Mounting Slot: 9/32” x 3/8”
  • Terminals: 10-24 x 5/8” post terminals; or 10” high-temperature fiberglass leads
  • Recommended maximum wattage: 40 watts/square inch
  • Voltage: 480 VAC maximum
  • Installation: optimize heater performance by following these heater installation guidelines


Backer Marathon ceramic strip heaters (sometimes called channel strip heaters) are ideal for rugged, high-temperature performance applications. They are available with a contamination-resistant stainless-steel sheath (for temperatures up to 1200°F), with or without mounting tabs, and can be manufactured with post terminals or a variety of lead options. They are bolt-in replacements for many of the Chromalox, GE, Watlow, and other strip heaters.


Ceramic Strip Heater Specifications:

  • Maximum temperature: 1200°F
  • Maximum watt density: 75 W/linear inch. 120 if two sides in contact with heated part
  • Maximum wattage: 120 Watts per inch of heated length; 75 if only one side is contacting the surface
  • 1.5” wide, 5/16” or 3/8” thick, up to 72” long
  • 5/16” x 1⁄2” mounting slots (center to center = overall length - 3/4)
  • Maximum voltage: 300V standard, 480V special
  • Maximum amperage (leads): 12 amps
  • Maximum amperage (terminals): 20 amps
  • Wattage tolerance: +5%, -10%
  • Resistance tolerance: +10%, -5%


Helping OEMs Heat Up

Backer Marathon is the industry leader in production speed and reliable, quality heaters for plastics and packaging, serving OEMs with durable, customized solutions for unique heating needs. Backer Marathon designs, manufactures, and stocks industrial-grade heating elements and temperature sensors.

Engineers have direct access to our trained technical experts who have been pioneers in this sector for decades. Our vast array of heaters serves diverse industries and applications—from food and beverage packaging to industrial platens used in compression molders.

We believe in hard work, creative engineering, and excellent customer service. Whether you need one piece or one thousand, Backer Marathon is committed to providing you with exactly what you need when you need it. As we innovate and lead the industry with unparalleled engineering and customer service, we look forward to helping you continue to grow with us. Let’s talk about your next project. Contact us now or call us today at 1 (830) 775-1417. We’re excited to collaborate with you.