Very small-section tubular heaters with high watt density that can be formed —straight, helical or in custom geometries— to the exact part to be heated: injection nozzles, hot runner manifolds, molds, blades and pipes.
A formable coil heater is a sheathed electric heating element with a circular, square or rectangular section, built from annealed stainless steel tube so it can be cold-bent and adapted to the exact geometry of the part to be heated without losing electrical performance.
In international technical terminology these elements are known as coil heaters, formable tubular heaters or, when mounted on injection nozzles, hot runner nozzle heaters. The smallest-diameter version (1.8 mm) is known as a micro coil heater.
Its construction —NiCr 80/20 resistance wire embedded in compacted magnesium oxide (MgO) inside a TIG-welded stainless steel sheath— improves heat transfer, extends service life and allows working temperatures up to 750 °C.
For blades, folding bars and flat surfaces where heat is applied in a line.
Wound onto pipes, injection nozzles and hot runner manifolds, maximizing the contact surface.
Flat spirals, ovals, serpentines or any routing defined by the customer's drawing.
| Spanish | Resistencia helicoidal conformable · resistencia conformable · resistencia moldeable |
| English | Coil heater · formable tubular heater · hot runner nozzle heater · micro coil heater (Ø 1.8 mm) |
| German | Wendel-Rohrheizkörper · Düsenheizkörper · Heißkanal-Düsenheizung |
| Italian | Resistenza a spirale conformabile · riscaldatore per ugelli a canale caldo |
The program ranges from micro-sections of 1.8 mm up to sections of 8.5 mm, in rigid versions formed at the factory and flexible versions for on-site forming. Every series can be built to custom length, power, voltage and forming geometry.
| Series | Standard sections | Distinguishing feature |
|---|---|---|
| Standard formable | 3 Ø · 4 Ø · 3×3 · 6×6 · 2.2×4.2 · 5×7 mm | Formed at the factory to drawing; tangential, axial or radial outlet |
| Mini formable | 1.8 Ø · 1.8×1.8 mm | Micro-section for very small-diameter nozzles |
| Formable CL | 5 Ø · 6.4 Ø · 8 Ø · 8.5 Ø · 6×6 mm | Connection at each end; annealed tube |
| Flexible CL | 6.5 Ø · 8 Ø · 8.5 Ø · 6×6 · 8×8 mm | Annealed corrugated tube, formable on-site; connection at each end; 40 mm inactive per side |
| Flexible ML | 6.5 Ø · 8 Ø · 8.5 Ø · 6×6 · 8×8 mm | Connection at one end only (1,000 mm); designed to be embedded in molds; lengths from 200 to 3,000 mm (4,000 mm on special order) |
| Bronze-encapsulated | To nozzle | Formable core with stainless steel sheath encapsulated in bronze: maximum thermal uniformity and corrosion protection |
| Nozzle electrification (zamak) | To customer's nozzle | The customer's own nozzle is electrified directly |
The rigid versions are delivered already formed to drawing (repeatability in series production). The flexible versions, with an annealed corrugated tube, let the customer perform the final bend in-house while respecting the minimum radius of the section — which simplifies inventory when several mold geometries coexist.
The lead outlet direction is defined at the order stage and determines the machine mounting. The three standard outlets are tangential, axial and radial. Standard connection leads are 1,000 mm long.
The lead exits tangent to the last coil.
The lead exits parallel to the axis of the helical form.
The lead exits perpendicular, outward from the helix.
Each heater includes cold zones (sections with no resistance wire) at the ends, from 5 to 15 mm depending on length and diameter. In the flexible versions the inactive zone is 30 mm on the lead side.
There is also a 35 mm non-formable zone next to the outlet that must not be bent, so as not to damage the electrical transition. The actual heated length is the total length minus the cold zones: accounting for it avoids temperature gradients and errors in the watt density calculation.
Send us the geometry of your nozzle or mold. We'll come back with section, power and forming. Surisa's technical team defines the element from your drawing or a sample of the part to be heated, and proposes the right series, section and lead outlet.
| Parameter | Value |
|---|---|
| Resistance wire | NiCr 80/20 |
| Insulation | Compacted MgO (magnesium oxide) |
| Sheath | Stainless steel (annealed in on-site formable versions) · TIG welding |
| Max. working temperature | 750 °C at the sheath surface |
| Recommended watt density | ≤ 4 W/cm² (standard) · up to 10 W/cm² (flexible Ø 6.5) · up to 15 W/cm² (flexible Ø 8–8.5) |
| Maximum current (flexible) | 5.45 A (Ø 6.5 and 6×6) · 9.10 A (Ø 8, Ø 8.5 and 8×8) |
| Dielectric strength | 1,500 V / 1 s (standard) · 1,000–1,250 V depending on section (flexible) |
| Cold insulation resistance | ≥ 5 MΩ at 500 V DC |
| Cold leakage current | ≤ 0.1 mA at 242 V |
| Length tolerance | ± 2.5 % (standard) · ± 1.5 % (flexible) |
| Diameter tolerance | ± 0.1 mm |
| Power tolerance | ± 10 % |
| Integrated thermocouple | Optional · type J (Fe-CuNi) or type K (NiCr-Ni), depending on section |
Formable coil heaters are used in any thermal process where electric heating must be concentrated in very tight spaces: plastic injection, molds, non-ferrous metal casting, packaging machinery and fluid processes.
Heating of injection nozzles and hot runner manifolds (hot runner systems), including very small-diameter nozzles with 1.8 mm micro-sections.
Flexible heaters embedded in machined channels of the mold, for uniform temperature control of injection, blow and PET preform molds.
Heating of nozzles and feed channels in zamak and aluminum casting, including direct electrification of the nozzle.
Hot-cutting blades, welding jaws and film folders in packaging machinery.
Heat tracing and localized heating of pipes, fittings and distribution blocks.
The bronze-encapsulated version improves the fit on the nozzle and the heat distribution. Get in touch.
The rigid version is formed at the factory to drawing and delivered with its final geometry, guaranteeing dimensional repeatability in series production. The flexible version is made with annealed corrugated stainless steel tube, which lets the customer bend it on-site and adapt it to the mold or nozzle in their own shop, respecting the 35 mm non-formable zone next to the lead outlet. The flexible version simplifies inventory when several mold geometries coexist.
The maximum working temperature is 750 °C at the sheath surface. To operate reliably in that range, good mechanical contact with the part to be heated is essential, along with respecting the recommended watt density: up to 4 W/cm² in the standard series and up to 10–15 W/cm² in the flexible versions, depending on section.
The standard program covers round sections of 1.8 — 3 — 4 — 5 — 6.4 — 6.5 — 8 and 8.5 mm in diameter, square sections of 1.8×1.8 — 3×3 — 6×6 and 8×8 mm, and rectangular sections of 2.2×4.2 and 5×7 mm. The choice of section depends on the diameter of the nozzle or channel, the power required and the minimum admissible bend radius.
Yes. Formable coil heaters can be built with an integrated thermocouple, type J (Fe-CuNi) or type K (NiCr-Ni), depending on the section of the element. The thermocouple measures the temperature directly in the body of the heater, enabling precise closed-loop control on injection nozzles and hot runner manifolds.
The cold zone is the section at the ends with no resistance wire, from 5 to 15 mm depending on length and diameter (30 mm in flexible versions). It must be taken into account when sizing the heater: the actual heated length is the total length minus the cold zones. Ignoring it causes temperature gradients at the ends of the part and errors in the watt density calculation.
Yes. The single-end connection flexible versions are specifically designed to be embedded in machined channels of the mold, with lengths from 200 to 3,000 mm (4,000 mm on special order) and loads up to 15 W/cm². By adapting to the channel routing, the heat is distributed uniformly across the area of the mold that requires it.
Yes. In addition to the standard program, heaters are made to custom length, power, voltage, section and forming geometry, with tangential, axial or radial lead outlets and four types of lead protection. Surisa's technical team advises on defining the element from the drawing or a sample of the part to be heated.
Tell us the geometry and the target temperature. We'll come back with the right configuration. Standard and custom formable coil heaters, with in-house engineering support since 1974.
