Table of Contents

Advanced Stamping Technology for
Motor Stator & Rotor Cores

Increase magnetic flux density – reduce core loss – ensure stable mass production. Integrating high-speed stamping presses + progressive dies + automatic interlocking to create a competitive advantage for your factory.

200–400 SPM Fully Automated Process Die Life > 120 Million Strokes

1. Overview & Benefits

Motor cores (static stator & rotating rotor) are the foundation of electro-magnetic energy conversion. The core's efficiency determines the entire motor's performance. Optimization requires the right materials, optimal magnetic permeability, and controlled core loss.

Strengths of advanced stamping technology
High automation • Stable dimensions • Long die life • Ideal for mass production • Optimized cost per cycle.

Automated Process on a High-Speed Press

✓Feeding → stamping → forming → interlocking → finished core output
✓Multi-station progressive die, made of carbide alloy
✓Controlled one-way burr, standard stacking height

Stamping and automatic interlocking process of a stator core on a high-speed press

2. High-Speed Stamping Equipment

Technical requirements: 200–400 strokes/minute for stator & rotor cores. High precision at the bottom dead center (BDC) of the ram/slide is crucial to ensure quality during in-die automatic core stacking.

Machine Characteristics

✓High speed, superior precision & rigidity
✓Optimized structure for carbide progressive dies → increased die life
✓Integrated uncoiler & leveler

Safety & Control

✓Electronic control, real-time fault monitoring
✓Malfunction → signal sent → immediate press stop to protect the die

Leading Brands

GUANGDUAN (China) AIDA (Japan) DOBBY (Japan) ISIS (Japan) MINSTER (USA) SCHULER (Germany)

The above press brands are known for their feeding accuracy, rigidity, and safety systems – suitable for automatic stator/rotor core stacking.

Structural diagram of a GRT series high-speed press for motor core stamping

GRC high-speed press with a rigid frame, suitable for progressive dies

3. Modern Die Technology for Stator & Rotor Cores

Multi-station progressive dies replace the method of separate stamping and manual assembly, delivering superior precision and efficiency.

3.1. Progressive Die Overview

Punch & Die Material: carbide alloy • Grinding cycle > 1.5 million strokes/time • Total lifespan > 120 million strokes (depending on operating conditions).

✓Integrated rotation, counting/separation, and safety mechanisms
✓High manufacturing precision, complex yet stable structure

3.2. Automatic Riveting/Stacking

Principle: Stamping rivet points with a specific geometry. The protrusion on one lamination fits into the recess of the next, creating a natural interference fit → tight bond, compact stack, and unidirectional burrs.

Lamination Count Control Custom Stack Height Automatic Core Separation

A mechanism of strip puller + cylinder + solenoid valve creates a counting hole or skips the rivet point on the last lamination to separate one core from the next.

Close-up of rivet points created in a progressive die to interlock stator laminations

Full Interlock Type

The bonding force is formed directly within the die, no external pressing needed.

Semi-Interlock Type

A very small gap remains after exiting the die → requires additional pressing to achieve the required bonding force.

Rivet Point Design: Symmetrical and uniform layout; optimized according to lamination shape & electromagnetic requirements; avoids collisions within the die.

4. Automatic Assembly Methods

Direct Stacking

Stamping & stacking directly, with no rotation between laminations.

Skewed Stacking

Each lamination is rotated by a small angle before interlocking – common for AC rotors. A small rotation mechanism is integrated into the die.

Rotational Stacking

Each lamination rotates by a large, defined angle (e.g., 45°, 60°, 90°) to compensate for thickness variations and improve magnetic properties. Driven by a stepper/servo motor or mechanically by the press's motion.

Combined Rotational + Skewed Stacking

Simultaneously compensates for material variations and optimizes AC motor performance based on application requirements.

5. Current Status & Development Trends

History: The US & Japan developed core stacking technology in the 1970s; China accelerated from the mid-1980s and is now approaching international standards in design & manufacturing.

Die Structure Innovation Ultra-Precision & High-Tech Large Angle + Skewed Rotation Multi-Layout Material Usage Adaptation to Higher SPMs

Operational Implications: Standardizing SPM/die data, monitoring punch-die lifespan, and planning grinding/replacement schedules based on real (shot-based) data.

6. Conclusion

Advanced stamping technology for stator/rotor cores is elevating motor manufacturing capabilities – especially for automotive motors, precision stepper motors, and small AC/DC series. To succeed, in addition to investing in precision die machining equipment, an experienced design and manufacturing team with practical expertise is the key factor.

Implementation Strategy: Standardize processes – localize component sourcing – align with international standards – specialize by product group for sustainable scaling.

A completed motor rotor core after the automatic skewed stacking process

Comprehensive Solution Consulting

PRESTEC is committed to partnering with factories to standardize stamping processes, optimize dies, and increase SPM rates to shorten cycle times, stabilize quality, and achieve sustainable production growth.