A crosshead is one of the most critical components in any cable extrusion line. It is the tooling assembly that guides molten polymer material around a moving wire or conductor, forming a uniform layer of insulation or sheathing on the outside.
Without a well-designed crosshead, you cannot achieve consistent insulation thickness — and inconsistent insulation means rejected cable, wasted material, and failed quality checks.
How a Crosshead Works
In a cable extrusion line, the extruder screw melts and pressurises the polymer compound. This molten material is then channelled into the crosshead, which is mounted at a right angle (hence the name “cross”) to the direction of the wire being fed through.
Inside the crosshead, the molten polymer is directed through a die and tip assembly that shapes it around the conductor as it passes through. The geometry of the die and tip controls:
- Insulation thickness — how thick the coating is
- Concentricity — how centred the insulation is around the conductor
- Surface quality — smoothness and consistency of the outer surface
The coated cable then exits the crosshead and enters a cooling trough where the insulation solidifies.
Types of Crossheads
Not all crossheads are the same. The right type depends on your cable specification, production speed, and material being processed.
1. Fixed Centre Crosshead
In a fixed centre crosshead, the die and tip are in a fixed position relative to each other. The concentricity is set during installation and cannot be adjusted during production.
Best for: High-volume production of a single cable type where setup time is acceptable and specifications are consistent.
Advantage: Simpler design, lower cost, very stable once set up correctly.
Limitation: Any eccentricity requires a production stop to readjust.
2. Manual Centre Crosshead
A manual centre crosshead allows the operator to adjust the position of the tip while the line is running — without stopping production. Adjusting screws on the body of the crosshead shift the tip position to correct concentricity in real time.
Best for: Production lines running multiple cable types, or where conductor diameter varies, requiring frequent concentricity corrections.
Advantage: Flexibility during production without downtime.
Limitation: Requires a skilled operator who can read concentricity measurements and make accurate adjustments.
3. Triple Layer / Multi-Layer Crosshead
A triple layer crosshead feeds three separate polymer streams — inner layer, insulation, and outer sheath — through a single crosshead assembly. Each layer is applied in one pass.
Best for: High-specification cables requiring multiple material layers such as XLPE insulated cables, LSZH sheathed cables, and EV charging cables.
Advantage: Single pass for a multi-layer product — dramatically increases line efficiency.
Limitation: Higher cost, more complex setup, requires precise control of each melt stream.
4. Skin Layer Crosshead (60–80%)
A skin layer crosshead applies a thin outer coating — typically 60–80% of the total insulation wall — over an existing insulation layer. Common in tandem extrusion setups.
Best for: Dual-material cable constructions where the bulk insulation and outer skin are different compounds.
How to Select the Right Crosshead
Choosing the correct crosshead for your line depends on four factors:
1. Cable type and specification
What type of cable are you producing? A power cable, building wire, solar cable, and optical fiber cable all have different insulation requirements and will need different crosshead geometries.
2. Conductor diameter range
If your line runs multiple conductor sizes, a manual centre crosshead gives you flexibility. If you run a single size at high volume, a fixed centre crosshead may be more appropriate.
3. Number of layers
If you need dual or triple layer insulation in a single pass, you need a multi-layer crosshead. Running two separate lines in tandem is the alternative but requires more floor space and capital.
4. Production speed
Higher line speeds require crossheads designed for low pressure drop and even flow distribution. At very high speeds, uneven flow in the crosshead manifests as surface defects and eccentricity.
Common Crosshead Problems and How to Fix Them
Problem: Eccentric insulation (insulation thicker on one side)
Cause: Die and tip are not concentric. In a fixed centre crosshead, stop the line and adjust. In a manual centre crosshead, use the adjustment screws while the line is running.
Problem: Surface roughness or sharkskin appearance
Cause: Melt temperature too low, or the crosshead is not up to processing temperature. Allow more warm-up time, or increase melt temperature slightly.
Problem: Insulation thickness variation along the length
Cause: Inconsistent extruder output (surging), or conductor tension variation. Check the extruder screw wear and haul-off speed consistency.
Problem: Carbon or degraded material in the crosshead
Cause: Stagnation zones in the flow path, or material left in the crosshead during shutdown. Purge thoroughly before shutdown and clean the crosshead regularly.
Crossheads from Sai Extrumech
Sai Extrumech manufactures fixed centre, manual centre, and triple layer crossheads for wire and cable extrusion lines. All crossheads are precision machined to tight tolerances and designed for long service life with minimal maintenance.
We also manufacture the complete die and tip sets, guide tubes, and tooling accessories that work with our crossheads — and we supply replacement tooling for lines from other manufacturers.
If you are unsure which crosshead is right for your application, contact our engineering team. We will review your cable specification and recommend the correct tooling configuration.
👉 View our Crosshead Range
👉 Contact our Engineering Team
Frequently Asked Questions
Q: What is the difference between a die and a tip in a crosshead?
A: The tip (also called a guide or core tube) supports the conductor as it passes through the crosshead and determines the inner diameter of the insulation. The die determines the outer diameter and shape of the insulation. Together, the die-tip gap controls insulation wall thickness.
Q: Can I use the same crosshead for different cable types?
A: The crosshead body can often be reused, but the die and tip sets are specific to the conductor size and insulation diameter. You will need a different die-tip set for each cable specification.
Q: How often should a crosshead be cleaned and serviced?
A: For continuous production, a full crosshead strip-down and inspection is recommended every 3–6 months depending on the material being processed. Crossheads running abrasive compounds like filled XLPE may need more frequent inspection.
Q: What materials are crossheads made from?
A: Crosshead bodies are typically made from hardened tool steel. Die and tip components are often made from tungsten carbide or hardened steel with chrome or nickel plating for corrosion resistance and surface quality.
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