Power cable stranding has evolved significantly over the decades, driven by the need for higher efficiency, improved cable quality, and cost reduction.
Traditionally, stranding was performed using rotating cages, where reels of wire were loaded onto a rotating structure, followed by a pulling capstan and a stationary take-up. This method has been widely used for both small and large power cables, ensuring a consistent and reliable production process. However, with advancements in technology, alternative stranding solutions have emerged, offering new benefits to cable manufacturers.
Pro and cons of rigid cage strangers
Rigid cage stranders have been the standard for power cable production for many years. Their key characteristics include:
- High mechanical stability due to the robust rotating cage structure.
- Capability to handle large cross-section conductors, making them suitable for medium and high-voltage cables.
- Traditional pulling system involving a capstan and a stationary take-up, ensuring controlled stranding tension.
- High precision in conductor positioning, which is crucial for maintaining electrical properties.
- Greater inertia and energy consumption, as the entire rotating cage must move during operation.
- Low efficiency, due to the significant loading time exceeding 50% efficiency requires skilled operators.
While rigid cage stranders remain a reliable choice, their operational constraints, such as higher energy consumption and fixed factory layout requirements, have led to the exploration of alternative technologies.
The rise of double twist stranders
Double twist stranding technology presents a modern, efficient alternative to the traditional rigid cage approach.
The key features of double twist stranders include:
- Non-stop coil Payoffs placed on the floor, allowing for greater flexibility in factory layout with a double position setup, minimizing production interruptions.
- Rotating light bow for stranding, reducing mechanical complexity and energy consumption.
- Take-up reel inside the cradle, simplifying the handling of stranded cables.
- Lower investment and maintenance costs, making them a cost-effective solution.
- Slip ring with carbon brushes for power and motor data signals and a Wi-Fi system for contactless data transfer & PLC signals.
- Conductor length limited to Take-up reel size.
- Double twist stranders can produce Unilay conductors only.
These advantages make double twist stranders an attractive choice for manufacturers seeking higher efficiency and operational flexibility.
Rigid cage stranders vs double twist stranders: what to choose?
Choosing between a rigid cage strander and a double twist strander depends on various factors, including production needs, budget, and factory layout.
Here’s a direct comparison:
| Double Twist | Rigid Cage Strander |
| Always running at the top available speed | Lower speeds for full reels |
| Seamless process | Stops for loading |
| Steams/baskets pay-offs with high capacity | Reels pay-offs |
| No downtime (double position steams/baskets) — Higher efficiency due to continuous operation and reduced downtime | Downtime due to pay-offs |
| Reduced initial investment and maintenance cost | More expensive machine requiring higher maintenance and higher investment cost |
| Flexible layout — Allows for a more adaptable factory setup | Reels pay-offs require specific positioning, limiting layout flexibility |
| Optimized power consumption | Higher installed power — Requires more energy due to rotating structure |
| Produces high-quality conductors with longer strand lengths and fewer cable joints | Produces high-quality conductors |
Given these factors, double twist stranders provide a clear competitive edge for manufacturers looking to improve productivity and reduce costs where the technical specifications do not dictate cross lay.
Optimizing power cable stranding process with the right machinery
MFL Group offers an extensive portfolio of machinery designed to meet the diverse needs of power cable manufacturers. Our double twist stranders deliver high speed and reliability for unilay copper and aluminum conductors, optimizing production efficiency.
Our portfolio now includes the DTO 2500, supporting bobbin sizes up to 2500 mm.
Key Features:
- Maximum cross-section: Aluminum or copper up to 500 mm², both compressed and compacted.
- High productivity: Capable of producing up to 30 km of strand per 8-hour shift with non-stop coil payoffs.
- Superior strand lengths: The large reel volume (DIN46395 [5.026 dm³]) reduces the number of conductor joints and saves space in production facilities.
- Automatic main bearing greasing unit, ensuring smooth and maintenance-free operation.
- Wireless or contactless data transfer, minimizing maintenance while increasing reliability.
- Automated reel extraction system, eliminating the need for manual intervention during reel changeovers.
- Energy Efficiency, thanks to the single bow design which reduces energy consumption and enhances mechanical reliability.
- High cable compaction degree
Whether you require just stranding equipment or a complete production line for power cables, MFL Group’s solutions are engineered to enhance productivity, optimize energy use, and improve overall cable quality.
To learn more about our machinery and find the best solution for your production needs, contact us today.