Modern industrial systems increasingly demand that pneumatic, electrical, and optical functions operate in close proximity. Running separate lines for each function consumes space, adds weight, and multiplies potential failure points. A combined cable assembly brings pneumatic tubes, electrical cables, and fibre optics together inside a single jacket, delivering all three functions through one compact, routable profile. This approach is gaining traction across industries where reliability, space efficiency, and simplified installation matter most. Explore Toppi’s range of specialty tubes to see how multi-element designs translate into real products.
Whether the application involves robotics, subsea equipment, medical devices, or factory automation, the engineering challenge is the same: how to combine mechanically different elements without compromising any single function. This article walks through the co-extrusion techniques that make multi-element assemblies possible, the design considerations that keep them reliable, the industries driving demand, and the development process from first concept to finished product.
How Co-Extrusion Makes Multi-Element Assemblies Possible
Co-extrusion is the simultaneous extrusion of two or more materials to form a single continuous profile. In a multi-element assembly, this technique creates separate channels, or lumens, within one structure. Each lumen can carry a different medium: compressed air, electrical conductors, or optical fibre. The result is a unified profile that replaces what would otherwise require three or more individual cable runs.
The process works by feeding different polymer compounds through a shared extrusion die. Each material occupies a distinct zone within the cross-section, and the layers bond during cooling to form an integrated structure. Manufacturers can combine materials with very different properties in the same profile. For example, a rigid inner wall might protect a fibre optic strand from micro-bending, while a flexible outer layer allows the entire assembly to route through tight spaces. Material layers in co-extruded profiles can be extremely thin, enabling precise control over each element’s environment without inflating the overall diameter.
Multi-lumen tubing takes this further by creating multiple parallel channels within a single extruded profile. Each lumen is sized and shaped for its specific payload. A pneumatic channel needs smooth bore walls and pressure resistance. An electrical channel requires adequate insulation and, in some configurations, shielding. An optical channel must maintain the fibre’s minimum bend radius and protect against shear forces. Co-extrusion handles all of these requirements in a single manufacturing pass, which reduces assembly steps and eliminates the need to thread individual elements through a pre-formed conduit after the fact.
The choice of polymers is critical. Common materials include polyurethane, polyethylene, nylon (PA), and high-performance fluoropolymers. Each brings specific advantages: chemical resistance, flexibility at low temperatures, flame retardancy, or halogen-free composition. The ability to pair these materials in a single profile is what makes co-extrusion the enabling technology behind modern combined cable assemblies.
Key Design Considerations for Hybrid Assemblies
Combining pneumatic tubes, electrical cables, and fibre optics in one assembly introduces engineering challenges that do not exist when each element runs independently. The most important design decisions involve electromagnetic compatibility, mechanical behaviour, thermal management, and connector integration.
Electromagnetic Interference and Signal Integrity
Power conductors generate electromagnetic fields that can introduce noise into adjacent signal cables and degrade optical performance indirectly through connector electronics. Proper shielding and physical separation between power and signal elements are essential. Grounding strategies must be planned from the outset, not added as an afterthought. In assemblies that carry both high-current power and sensitive data signals, conductor separation and shielding prevent interference without requiring an oversized outer diameter.
Bend Radius and Mechanical Compatibility
Each element in a hybrid assembly has its own minimum bend radius. Electrical cables typically follow the IPC-620 guideline of three times the cable outside diameter. Fibre optics are more sensitive: bending beyond the minimum radius causes measurable increases in optical attenuation, and unlike copper conductors, optical fibres can be damaged by relatively small shear forces. Pneumatic tubes, depending on wall thickness and material, have their own bending limits. All internal components must share compatible bend radii so that the assembly can be routed as a single unit without damaging any element.
For applications involving constant motion, torsion, or drag-chain routing, mechanical compatibility becomes even more critical. Every element must tolerate repeated flexing over the assembly’s service life. Material selection, lumen geometry, and internal reinforcement all play a role in achieving this.
Connector Design and Maintainability
A hybrid assembly is only as reliable as its termination points. Hybrid connectors must establish pneumatic, electrical, and optical connections simultaneously, and each connection must be accurate every time. Misconnection risks are higher when multiple media types share a single interface. Well-designed hybrid connectors incorporate keying, colour coding, or mechanical interlocks to prevent errors.
Long-term maintainability is another factor. If one element fails, the repair or replacement process should not require disassembling the entire assembly. Modular connector designs and accessible breakout points help keep maintenance practical. Relevant standards for hybrid assemblies include IEC 60794 for optical fibre cables and IPC/WHMA-A-620F for cable and wire harness assembly, which was updated in 2025 to strengthen guidance on inspection, process control, and testing.
Industries That Benefit From Combined Assemblies
Multi-element assemblies solve a common problem across many sectors: the need to deliver power, data, and fluid or gas through constrained spaces with high reliability. The industries driving adoption share a few characteristics: demanding environments, limited routing space, and a low tolerance for failure.
Medical Devices and Surgical Robotics
Surgical robotic systems require simultaneous delivery of electrical power, high-speed data (including 4K video), and pneumatic actuation through compact, flexible cable assemblies. Combined assemblies reduce the number of cables entering the sterile field and simplify the connection process for clinical staff. In this sector, compliance with standards such as EN ISO 5359 and strict creepage and clearance requirements add complexity but also make the integrated approach more attractive, since fewer separate cables mean fewer individual compliance challenges.
Oil, Gas, and Subsea Applications
In subsea environments, hybrid umbilical cables support simultaneous data transmission, electrical power, hydraulic fluid, and chemical injection. Running separate cable systems at depth multiplies weight, deployment complexity, and the number of pressure hull penetrators required. A single ruggedised assembly that handles all functions is not just convenient; it is often the only practical option. Similar logic applies to onshore oil and gas installations, where harsh conditions and remote locations make simplified cabling a reliability advantage.
Factory Automation and Robotics
Industrial robots and automated production lines increasingly combine power delivery, Ethernet communication, and pneumatic control in a single cable assembly. This reduces cable tray congestion, simplifies robot arm routing, and cuts installation time. In drag-chain applications, a single hybrid cable withstands repetitive motion more predictably than a bundle of separate cables that can abrade against each other.
Energy and Telecommunications
Wind turbines, power converters, and telecommunications infrastructure all benefit from assemblies that combine fibre optics with electrical conductors. In these applications, the fibre optic element typically handles high-speed monitoring data, while copper conductors carry power or control signals. Halogen-free and flame-retardant materials are often mandatory, adding another reason to design the assembly as a single, purpose-built product rather than bundling off-the-shelf cables.
Comparing Single-Function Runs to Integrated Solutions
The traditional approach to routing pneumatic, electrical, and optical lines is straightforward: run each one separately. This works well in simple installations with ample space and few connection points. As system complexity grows, however, the disadvantages of separate runs accumulate quickly.
The table below summarises the key differences:
- Installation space: Hybrid cables can save up to 60% of installation space compared to running separate cables, according to industry analysis. Fewer cables mean smaller cable trays, tighter routing paths, and cleaner layouts.
- Installation time and labour: One cable to pull, one set of connectors to terminate. In large-scale automation projects, labour often represents a major portion of total cost, making this a significant advantage.
- Reliability: Fewer connection points reduce the risk of mechanical failure, signal loss, and long-term electrical issues. A single organised assembly is easier to inspect and replace than multiple separate cables.
- Troubleshooting: When all functions run through one assembly, identifying and isolating faults is simpler. There is one cable path to trace, not three.
- Upfront design effort: Custom hybrid assemblies require more engineering time at the design stage. Material selection, shielding, bend radius compatibility, and connector design all need careful specification.
- Total cost of ownership: Although the per-metre cost of a hybrid assembly is higher than a single-function cable, the total system cost often decreases when factoring in reduced labour, fewer connectors, smaller cable management infrastructure, and lower maintenance burden.
Separate cable runs remain practical for small, static installations where routing space is not constrained. For complex systems, especially those involving motion, harsh environments, or space-limited enclosures, integrated assemblies deliver measurable advantages in reliability, installation efficiency, and long-term maintainability.
It is worth noting the terminology: industry standards define a hybrid cable as one containing both optical fibre and current-carrying conductors. A composite cable combines different varieties of a single transmission medium. When pneumatic tubes are added to the mix, the result is often called a multi-element or multi-function assembly, reflecting the broader scope of what the product delivers.
From Concept to Finished Product: The Development Process
Developing a multi-element assembly that combines pneumatic tubes, electrical cables, and fibre optics follows a structured process. Each stage builds on the previous one, and catching design issues early prevents costly corrections later.
Requirements Analysis and Design
The process begins with a detailed understanding of the application. What pressures will the pneumatic channels carry? What voltage and current ratings do the electrical conductors need? What data rates and attenuation limits apply to the optical fibres? What is the minimum bend radius the assembly must tolerate? Will it be static, or will it undergo repeated flexing? What environmental conditions will it face: temperature range, chemical exposure, UV, moisture?
With these parameters defined, designers select materials for each element and for the overall jacket. CAD modelling establishes the cross-sectional geometry, lumen placement, and wall thicknesses. At this stage, shielding strategies, connector interfaces, and breakout configurations are also specified.
Prototyping and Validation
A physical prototype validates the design before committing to production tooling. Modern prototyping often incorporates 3D-printed connector housings and custom brackets, enabling rapid design iterations without tooling delays. The prototype undergoes testing that covers electrical continuity, mechanical fit, pressure integrity, optical performance, and environmental resistance under realistic operating conditions.
Prototype validation is where design flaws surface at manageable cost. Industry experience suggests that resolving issues at the prototype stage is far less expensive than correcting them after production tooling has been manufactured. Once the prototype is approved, documentation including work instructions, fixture specifications, and quality control plans is finalised for volume production.
Production and Quality Assurance
Production shifts the focus from design validation to repeatability, consistency, and efficiency. Co-extrusion lines produce the multi-lumen profile continuously, with in-line monitoring of dimensions, wall thickness, and material integrity. Electrical testing, optical attenuation measurement, pneumatic pressure testing, and visual inspection are performed according to the quality control plan. Standards such as IPC/WHMA-A-620F define three product classes, ranging from general-purpose assemblies to high-performance products where failure is not acceptable.
Throughout production, traceability of materials and process parameters ensures that every metre of finished assembly can be linked back to its raw materials and manufacturing conditions. This traceability is increasingly important for customers in regulated industries who need to demonstrate compliance throughout their supply chain.
How Toppi Builds ToppMulti™ Cables That Integrate Multiple Functions in One Jacket
Toppi Oy is a Finnish manufacturer founded in 1953, specialising in plastic extrusion at its production facility in Espoo. With over 70 years of experience in co-extrusion, in-house toolmaking, and CAD-based product design, Toppi manufactures custom-tailored hoses, tubes, profiles, and cables for industrial customers across multiple sectors. The company holds ISO 14001 certification, runs on 100% fossil-free electricity, and carries the Avainlippu symbol for Finnish-made products.
The ToppMulti™ product line applies Toppi’s co-extrusion expertise directly to the challenge of multi-element assemblies. These cables integrate pneumatic tubes, electrical conductors, and signal lines within a single halogen-free jacket. The development process follows the full design-to-production workflow described above: CAD design, 3D-printed prototyping, in-house tooling, and volume production with documented quality control.
ToppMulti™ Product Comparison
- ToppMulti™ (PA12P40/HFFR): A multi-element assembly combining pneumatic tubes in a halogen-free, flame-retardant (HFFR) jacket with PA12 pneumatic tubing. Designed for applications requiring pneumatic control without electrical signal integration.
- ToppMulti™ with signal cable (KJAAM-HF): Integrates pneumatic tubes with KJAAM-HF signal cables in a single jacket. Suitable for automation and control systems that need both pneumatic actuation and electrical signal transmission in one routable assembly.
- ToppMulti™ with signal cable (NOVAK-HF): Combines pneumatic tubes with NOVAK-HF signal cables, offering an alternative signal cable specification for applications with different electrical or environmental requirements.
Toppi’s capabilities that support ToppMulti™ production include:
- In-house CAD design and 3D-printed prototyping for rapid validation
- Custom extrusion tooling manufactured in Toppi’s own tool shop
- Co-extrusion technology for combining different materials and functions in a single profile
- ISO 14001-certified environmental management with full material traceability
- Documented quality control throughout the production process
Whether the requirement is a standard ToppMulti™ configuration or a fully custom multi-element assembly tailored to a specific application, Toppi’s team works from initial concept through to finished product. Browse the ToppMulti™ range to see available configurations, or contact Toppi’s design team to discuss a custom combined cable assembly for your application.
