Band heaters for injection moulding and extruder barrels

01

Choose the insulation type, watt density and temperature limit

Panshine divides band heaters by insulation into mica, ceramic and mineral types, each with a metal sheath around the insulation and a helical or sinuated resistance wire. [3] Tempsens' mica band heaters use nickel-chromium resistance strip wound on mica, with a stainless steel or galvanized iron sheath, a maximum sheath temperature of 425 °C and watt density up to 45 W/in². [1] Omega's MB-2 two-piece mica bands are rated 21–40 W/in², up to 900 °F sheath and 750 °F barrel temperature, for 3½–10½ in barrels at 500–2,000 W. [2]

Panshine's band heater technical data give working voltage 120–480 V AC, operating temperature 1400 °F (760 °C) and watt densities of 120 W/in², and list extruders, blow moulding and injection moulding among applications. [3]

Editorial calculation: 1 in² = 6.4516 cm², so 45 W/in² ≈ 7.0 W/cm², 40 W/in² ≈ 6.2 W/cm² and 120 W/in² ≈ 18.6 W/cm². As a check on a published rating, Omega's 500 W MB3J1J2P1 for a 3½ in barrel and 1½ in width covers π × 3.5 × 1.5 ≈ 16.5 in², giving about 30 W/in², matching its listed 30 W/in². [2]

Give the supplier the barrel or nozzle outside diameter, available heated width, number of zones, wattage per zone, supply voltage and phase, barrel set-point temperature, holes or cut-outs needed for thermocouples or mounting, and the terminal and lead style.

02

Check the clamping fit, terminals and leads

Tempsens says its clamping band maintains clamping pressure and firm contact with the cylinder, eliminating air gaps at the contact; Omega attributes a uniform fit to ±1/16 in to its low-expansion stainless clamping band. [1] [2] Omega's two-piece heaters are each rated 240 V and are connected in series for 480 V or in parallel for 240 V. [2]

Tempsens notes that expandable mica heaters can be opened to the barrel diameter for installation but should only be opened all the way once (minimum ID 3 in), that custom holes need at least ½ in from the hole to the heater edge, that built-in type J or K thermocouples are available, and that terminal boxes help prevent electrical shock or shorts. Its high-temperature fibreglass leads are rated to 455 °C with a standard length of 10 in. [1]

Stated tolerances match across these sources: Tempsens gives wattage +5%/−10% and resistance +10%/−5%; Panshine gives resistance −5% to +10% and wattage −10% to +5%. [1] [3]

03

Check ceramic band limits and size tolerances

Tempco, a US heater maker, publishes the limits for its ceramic band heaters: maximum temperature 1,400 °F (760 °C), nominal watt density 20–45 W/in² with 45 W/in² maximum, a stainless steel sheath over ceramic fibre blanket insulation (1/4 in standard, 1/2 in double), and up to 480 V AC per termination at 12.5 A for lead-wire terminations or 25 A for screw terminations. Resistance tolerance is +10%/−5% and wattage tolerance +5%/−10%. It also notes that exposed electrical wiring on band heater installations violates electrical safety codes including OSHA. [4]

Size limits are set by construction: one-piece bands from 2 in to 21 in ID, two-piece and reverse bands up to 44 in ID (two-piece from 4 in, reverse from 5-1/2 in), minimum width 1 in, maximum width-to-diameter ratio 3:1 and 15 in maximum width at 5 in ID or more, with a nominal clamping gap of 3/8 in that should be stated larger when ordering if probes or thermocouples pass through. Width tolerance is ±1/16 in for 1–3-1/2 in widths, ±1/8 in for 4–6-1/2 in and ±1/4 in above. [4]

Editorial calculation: at 480 V and the 12.5 A lead-wire limit, one termination carries up to 6,000 W; at 240 V the same limit is 3,000 W. Tempco's 45 W/in² ceramic maximum matches the 45 W/in² Tempsens gives for mica bands, while its 760 °C maximum temperature is 335 °C above Tempsens' 425 °C mica sheath limit. [4] [1]

04

Compare what suppliers offer

The supplier linked to this page lists band heaters with drum heaters and other heating elements; its card links to the page reviewed.

Ask any supplier for the insulation type, sheath material, wattage and watt density, voltage, maximum sheath temperature, clamping construction, terminal type, lead material and length, tolerances, and insulation resistance and dielectric test values.

05

Trace the band heater parts

This is a functional reference built from the sources cited; it is not one maker's specification.

06

Fill the specification fields with values for your barrel

A band heater quotation needs values for your machine. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

07

Send the barrel, power and wiring data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Barrel: [outside diameter; heated width; zones]
Power: [watts per zone; voltage; phase]
Temperature: [set point; sheath limit]
Type: [mica; ceramic; mineral; one- or two-piece]
Features: [holes; thermocouple; terminal box]
Leads: [type; length; protection]

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