Most market demand for automotive EV tube is for a few types. TPV dual-layer tube with yarn knit, for example, exhibit favorable density, flexibility, and low noise features.
Most of today’s market demand for automotive tube is concentrating around a few construction types and takes in consideration tubes for electric vehicles (e.g. battery cooling). Maillefer categorizes three types: smooth multi-layer, corrugated multi-layer, and reinforced dual layer. For the three types, we propose complete and fully integrated production systems.
The choice of materials is evolving for all three. Both smooth and corrugated multi-layer tubes range from one to six functional layers and are typically made of various grades of polyamide (PA), polyolefins (PE/ PP) and thermoplastic elastomers (TPV/TPE). Use of fluoropolymers (PVDF and EFTE) are currently on hold because of the environmental concerns surrounding long-lasting per- and polyfluoroalkyl substances (PFAS).
A five-layer co-extrusion group for smooth tube
The reinforced dual layer tube is composed of rubber domains in TPV with a yarn knit in between. This construction has specific attributes which respond especially well to today’s market, such as low density, flexibility, low noise propagation, etc.
Multi-layer co-extrusion solution
To produce the range of tubes we essentially suggest one of two line configurations to our customers, depending on the product. The solution for smooth and corrugated multi-layer products begins with the coextrusion group, where the maximum number of layers and desired performances (i.e. line speed) determine the number of extruders, the sizes of the crosshead and the exact design of the flow distributors.
Our automotive line PAL 032-5L serves as the foundation when configuring a line for multi-layer tube production. Typical configurations range from one to five layers, while a six-layer setup is not unusual. The layout is optimized for connecting multiple extruders into a single crosshead. The line is complete with downstream components fully integrated into modern controls (i.e. employing Profinet, OPC UA, etc.)
Flexible crosshead at the heart
Our unique crosshead design, subject to continuous polymer proving, is at the heart of multi-layer coextrusion. Short residence times, optimized flows, flexible layer attribution, and maintenance ease characterize the head. The result we seek is product quality, performance with repeatability and reproducibility.
In theory, customers have 120 layer combinations at their disposal with a five layer crosshead. This means that any extruder in the group can be mapped to one of the five layers (i.e. 5 x 4 x 3 x 2 x 1 combinations) with all extruders employed. The possibilities grow more when disabling some machines, like when switching down from a five-layer product to a triple layer one. Customers get high flexibility for manufacturing a wide range of multi-layer tube, for today and for the future, with an extrusion group that is the most appropriate for their requirements.
Even more with corrugation
The flexibility increases by having the capability to produce corrugated tube. The line configuration resembles the one for multi-layer smooth tube, but needs corrugating components positioned after the extrusion group. Specific crosshead and tooling are also required for the downstream equipment. Our turnkey solutions involve an expertise in the process and the ability to master quality and performance.
TPV tube after knit (right) and then with outer layer (left)
Reinforced TPV tandem solution
Interest is on the rise for processing ability in reinforced TPV tube, which represents the second line configuration available. Rubber-like qualities including light weight, noise absorption, and flexibility, explain why TPV tube is gaining traction in electric vehicle applications. This tandem PAL 032-2L line is composed of two single-layer extrusion groups separated by intermediate knitting equipment.
The vacuum calibration trough placed after the first extrusion group is essential for maintaining the inner tube in shape and within tolerance. Our experience with small diameter (up to 32 mm) tube applications, notably for demanding medical tube, has led us to develop appropriate calibration techniques to keep product in spec. The application know-how is augmented by our best of class line controls. Maintaining the quality standards is especially true with the inner layer TPV tube being cooled and about to enter the knitting step.
Tandem extrusion line for reinforced TPV tube
Partnering with the best
Partnerships give us the ability to follow the construction types and the material evolution. Long-established relationships with key material suppliers and leading manufacturers make our extrusion technology quite adaptable to change. Flow analysis specific to each material and tube specifications lead to evolving designs for crosshead, screw and barrel. Plus, our facility and those of key material suppliers are equipped with Maillefer platforms that help tube manufacturers accelerate their own tube developments and arrive at new solutions. Such testing capabilities have become a great tool for demonstrating innovation amongst industry players and fast-tracking towards a reduction of our carbon footprint.
Pascal Scaramuzzino, PhD