Medium/Heavy-Duty Truck ERCB Dual-Worm Tandem High-Torque Output Solution

—Enabling Commercial Vehicle Electric Power Steering to Meet 450 Nm Peak Torque and Compact Packaging Challenges

1. Project Background & Customer Challenge

A leading China automotive steering system intergrator (with a full portfolio of C‑EPS, DP‑EPS, and R‑EPS products, and deep experience in commercial vehicle and heavy‑truck steering applications) faced three critical challenges when developing its next‑generation electric recirculating ball steering (ERCB) system for medium/heavy duty trucks and trailers:

•          Performance limits: The system needed a static torque of ≥450 Nm, along with an axial push‑out force ≥50 kN and radial pull‑off strength ≥12.5 N/mm².

•          Packaging constraints: At the same torque level, the package size had to be significantly reduced to fit the increasingly tight chassis layouts of heavy trucks.

•          Global climate adaptability: The solution had to operate reliably across a wide temperature range from –40°C to +120°C, and pass a full‑life durability test of 100,000 cycles.

Initial evaluations showed that most available solutions either met the torque target but were too bulky, or failed to meet the temperature requirements. The Customer needed a worm‑gear transmission that combined high torque density, high‑temperature stability, and long‑term durability.

2. Solution: Tandem Dual‑Worm High‑Torque Output

Nylacast Automotive collaborated with the Customer to develop a tandem dual‑worm high‑torque output design, achieving breakthrough performance within a compact envelope of <150 mm outer diameter and only 24 mm thickness:

Key technical enablers:

•          Polymer material: Made with Nylacast Casting Process (monomer in‑situ polymerisation), the ultra‑high molecular weight polymer exhibits very low internal stress, and high crystallinity, , ensuring excellent fatigue resistance, wear resistance at elevated temperatures and dimensional stability.

•          Polymer‑metal hybrid structure: An innovative bonding technology securely joins the polymer to the metal hub, providing the structural strength for 50 kN axial force and 12.5 N/mm² radial pull‑off, while also optimising heat dissipation.

•          Precision tooth optimisation: Using KISSsoft gear design software and FEA, the tooth geometry and width were fine tuned to maximise torque capacity within packaging requirement while delivering good NVH performance.

3. Performance Validation & Head‑to‑Head Benchmarking

Durability test conditions

•          Target cycles: 100,000 (full‑life design margin)

•          Early acceptance milestone: 30,000 cycles (60% progress acceptable)

•          Meshing point temperature: analysed and validated at ≤120°C per Customer requirement

•          Temperature range: –40°C to +120°C; laboratory completed 30,000 cycles

Side‑by‑side bench test against competitor

Our sample and a competitor’s sample was each tested under identical conditions. The results showed clear superiority of the Nylacast Automotive solution:

The Customer validated the design and successfully passed all DV (Design Verification) tests. Drawings have been formally approved.

4. Core Value & Achievements

✅ Torque and force requirements fully met: 300 Nm per worm, 600 Nm tandem output; axial/radial forces meet targets with margin.

✅ High‑temperature durability proven superior: At 120°C, actual test performance outperformed the competitor; full‑life design margin of 100,000 cycles.

✅ Compact size approved by Customer: Outer diameter <150 mm – one of the smallest in its torque class, offering greater freedom for vehicle packaging.

✅ Wide‑temperature reliability: Covers –40°C to +120°C, suitable for heavy‑truck global operating conditions.

This project has been established as a reliable benchmark for ERCB applications in medium/heavy‑duty trucks, providing a solid technical foundation for the Customer’s future platform expansion.

About Nylacast Automotive

Nylacast Automotive is a designer and manufacturer of safety‑critical polymer components with over 26 years of EPS worm‑gear innovation. Operating 6 global sites, the company has supplied worm gears to more than 300 million vehicles worldwide. With end‑to‑end capabilities in material formulation, casting, precision machining, and full in‑house validation, Nylacast Automotive’s products are widely used in C‑EPS, SP-EPS, DP‑EPS, and steer‑by‑wire (SbW) systems, and have been successfully extended to commercial vehicle EPS platforms.