5-axis Machined Thruster Impeller for Surfboard Propulsion

Background

For electric surfboards, the propulsion unit works in a harsh environment: salt water, sand, repeated impacts, and sudden load changes. The thruster impeller is the core rotating part. If its geometry or balance is not stable, the rider feels vibration, noise, and power loss.

In early prototyping, the machining process for this impeller was not mature, so we needed higher precision equipment to verify the design before scaling up. Mastars applies ISO 9001 and IATF 13485 quality systems to control every step, from individual metal components to the final assembled propulsion module, and utilizes the Hermle 5-axis center we own in-house, to manufacture the client's design from draft to prototype and to production.

5-axis machined surfboard thruster impeller with integrated spline and blades in one solid piece.

The Challenge

During prototyping, we had to keep the underwater thruster highly accurate while the design was still evolving. Blade profiles, hub features, and threaded interfaces all needed tight positional control and smooth surfaces. At the same time, the impeller had to be stiff and consistent as a single integrated part, not a loose stack of components.

Conventional 3-axis machining, plus multiple setups, introduced alignment error and made it hard to hold tolerances on the blades and internal spline. The result was variation in balance and performance that was not acceptable for a premium surfboard experience.

Complete surfboard propulsion module assembly, from shroud to 5-axis machined impeller and rear cap.

Mastars Solution

We moved the impeller to 5-axis machining on Hermle C-series centers. By cutting the hub, spline, and blades in one clamping, we kept geometry in a single coordinate system and removed stack-up from multiple setups. Simultaneous 5-axis toolpaths generate the curved blades and transitions with stable surface quality and controllable edge breaks. This reduced process complexity and uncertainty, especially in early design iterations.

For later small and medium-volume production, we transferred part of the work to other suitable machining centers and standardized fixtures to reduce piece cost while keeping key features referenced to the 5-axis master process. The same one-stop service also covers surface finishing, dynamic balance, assembly of the full propulsion module, and functional checks before shipment.

Hermle C-series 62UMT 5-axis center we owned in-house.

Benefits

The project demonstrates how we use 5-axis resources to secure critical features, then optimizes cost for volume.

✅ Hermle C-series 5-axis centers (such as C22, C32, C42, C62) provide high rigidity and thermal stability for complex impeller geometry.

✅ Single-setup machining improves positional accuracy between spline, hub, and blades for better balance and efficiency.

✅ Curved blades and tight fillets can be cut directly, reducing manual blending, rework, and variation between parts.

✅ The working envelope supports both compact impellers and larger propulsion housings within one machine family.

✅ ISO 9001 and IATF 13485-based control plans keep dimensions and balance consistent from prototype to batch builds.

Multiple Hermle 5-axis machines running in parallel to hold tight tolerances.

Use Cases

The same 5-axis machining capability supports other demanding rotating or free-form parts.

• Energy and fluid components: small turbines, pump impellers, flow-control rotors, and mixing elements with complex blade shapes.
• Mobility and industrial systems: steering knuckles, lightweight structural brackets, and multi-face housings that need accurate datums in one setup.
• Consumer and professional equipment: camera gimbals, robotic joints, and ergonomic housings with multi-angle features and smooth transitions.

Rows of high-speed CNC machining centers supporting small and medium-volume metal components.

Mastars, to be the most trusted and reliable one-stop services partner for low-volume digital manufacturing worldwide!