Warning – High Voltage!

After much success providing production volumes of engine and gearbox parts to the powertrains industry, Graphite’s latest growth area coincides with the rise in electric vehicles (EVs) and hybridisation.

As ever, design engineers are pushing the Additive Manufacturing (AM) industry for even more capable materials to solve challenging problems. In this case, Graphite’s ceramic-filled epoxy-resin-based material, Ceramic SLA, has come up trumps. This time as a material suitable for high voltage (HV) isolation.

Engineers working on HV electrical installations must adhere to various design rules with their component designs. The need for air gaps (clearance) and the insulating properties of materials may seem obvious, but for limited packaging space and high voltages, the phenomenon of creepage can also be useful. This is the shortest distance along a surface to make a connection between conductors.

3D printing in the Ceramic SLA material, not only provides good insulating performance for the required components, it also allows far more design freedom than conventional manufacturing methods. For example, specially designed features to maximise creepage distances allow tighter packaging where air gaps (clearance) alone would not be sufficient for the voltages. Although the material is dense, the process also allows engineers many options to include lightweighting features in designs.

Unlike conventional machining and injection moulding, pockets, holes, ribs, radii and complex forms can all be considered ‘free’ or may even reduce cost of the basic part outline. As the raw resin is a large part of the component cost, reducing part mass and resin usage is a true win-win. Reduced component cost, faster build times and vehicle mass reduction can all be achieved.

The featured component provides a solution to an EV technical challenge. The selected high voltage, high current (200-400A) connectors satisfy the cost and performance requirements, but have a freedom of rotation when installed. This 3d printed Ceramic SLA mounting block provides both electrical isolation and positional control of the otherwise free-to-rotate HV busbars. This ensures dynamic safety of the vehicle by preventing a short that could lock-up the drive motor at speed. It also helps to prevent any of the bolted connections working loose through movement or vibration.

Graphite’s Ceramic SLA material has a Dielectric Strength of 26kV/mm which outperforms the 16.5kV/mm of Acetal – a regularly-used material – and 18.9kV/mm of PEEK – a high cost alternative for niche projects.

For more information about the Ceramic SLA material and design guidance for manufacture please contact Graphite – 01296 482673.


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