Extruding Busbars for Our Future

Electric vehicles are powered by battery banks connected by busbars. What is a busbar? Maillefer assists producers in their move towards a sustainable extrusion future.

Electric vehicles are powered by battery banks interconnected with busbars. But, what is a busbar? What are the particularities for extruding the protective insulation sheath? Maillefer is providing initial systems to industry leaders dedicated to this application. Our R&D center is so equipped to encourage new and existing producers towards developing their products for a sustainable extrusion future.

A busbar is

A flat bar-shaped conductor of relatively short length is how we can describe a battery busbar. Either copper or aluminum, it is insulated with a PA sheath. Profile sizes range from 30 to 150 mm2. The advantages of a busbar over cable are related to its shape and composition. Higher current carrying capacity, more space savings, and the ability to take on tight angles are some.

Indeed, a flat shape requires little height within the confines of vehicle construction. A busbar fits snugly around car construction and components, as it is a pre-bent to take on those exact forms. The high current carrying capacity offers shorter charging times and improved heat dissipation. Overall, busbars clearly take the lead in meeting EV vehicle requirements.

The significant role of extrusion

Extrusion precision of automotive-grade polyamide (i.e. nylon) is a must. Knowledge of the material, extrusion design, and processing conditions play significant roles. PA is characterized by the high-temperature resistance required for the application. Colors, such as orange RAL 2003, are blended in with the polymer to fit regulations. Marking specific to lot, brand, and standards is also required.

The single-layer insulation thickness ranges from 0.5-0.7 mm. Planarity (i.e. flatness) and eccentricity have to be tightly controlled. The adhesion requirements are strict. Surface quality needs to be impeccable. When a busbar is bent into its final shape, the insulation layer must be wrinkle-free. Busbars undergo specific bending tests with tight radii to prove quality. Insulated bars are subject to spark testing to confirm the insulation properties.

Single source solution

A typical extrusion system includes a bar reel pay-off, caterpillar, conductor preheater, a single-screw air-cooled extruder for PA, a mono-layer crosshead including tooling for specified bar profiles, immersive water cooling, ink jet marking, caterpillar, take-up, control systems, and quality measurement and testing devices. By opting for a second payoff, accumulator, and additional take-up, the line is equipped to run continuously without speed ramping between reel changeovers and with improved efficiency.

The insulated busbar on reels is ready to be delivered to the next process step, which is usually automated. It includes cutting to the desired length, peeling off sections, and bending into shape.

Product traceability is an integral part of the system, along each process step. Tier-1 suppliers to the automotive industry require the ability to track each part back to its origin. Reporting and archiving are necessarily built into our control systems.

Visit and exchange

Our busbar extrusion capabilities are available for viewing and testing purposes. We welcome interested visitors to our R&D center, where we host product development initiatives and know-how exchanges. Maillefer is pleased to help introduce a high-value offering into a more sustainable future.


  • Harri Kiuru, Product Manager
  • harri.kiuru@maillefer.net


Topics: Elastomers, Maillefer, Extrusion, Wire & cable manufacturing, Digitalization, Pipe & tube manufacturing, Rubber, automotive, electric, battery

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