Have you ever wondered how those seemingly ordinary silicon steel sheets are transformed step by step into tightly packed, stable lamination stacks? Using progressive die stamping, manufacturers can produce thousands of stator and rotor laminations in a short time.
Before explaining the stamping process, let’s first look at what a progressive die-stamped motor core looks like.
What Is a Motor Core?
The motor core is the heart of an electric motor. It consists of a stator and a rotor and primarily functions to enhance the magnetic flux of the inductive coil, enabling efficient electromagnetic energy conversion.
Motor cores made by progressive stamping usually include interlocking features, which can be round or rectangular.
So how exactly are these stamped motor cores manufactured? What are the steps in the process?
Progressive Stamping Motor Lamination Process
Material Preparation
The first step in progressive stamping is preparing high-quality silicon steel strips. Common thicknesses we use include 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.27 mm, 0.3 mm, 0.35 mm, and 0.5 mm cold-rolled non-oriented electrical steel. The commonly used steel grades are listed in the table below.
| Sura Cogent-Sweden | JFE Steel-Japan | Steel-China | China Steel-Taiwan | |
| 0.1mm | NO10 | ST-100；10JNEX900 | ESW1020 | |
| 0.15mm | NO15 | ST-150 | B15AT1200/B15AV1000; 15SW1200 | 15CS1200 |
| 0.2mm | NO20/NO20-1200 | 20JNEH1200/20JNEH1500 | B20AV1200/B20AV1300; 20SW1200; 20TWV1200 | 20CS1200/1500 |
| 0.25mm | NO25-1350H | 25SW1250/1300; 25TWV1300 | ||
| 0.27mm | NO27-1400H | B27AV1400; 27SW1400; 27TWV1400 | ||
| 0.3mm | NO30-1500H | 30JNE230 | 30SW1500 | |
| 0.35mm | M270-35A | 35JNE250 | B35A210/230/250/270; 35SW270/35SWH1900/35SWYS5000 ； 35TW250 | 35CS210/230/250/270 |
| 0.5mm | 50JNE470 | B50A270/290/350/470/600/800； 50SW400； 50TW400 |
We also use nickel alloys and cobalt alloys to manufacture the motor rotor and stator laminations.
Progressive Stamping Die Design and Manufacture
The progressive die is the core of the entire stamping process. Without a high-quality die set, it is impossible to mass-produce precision laminations stably and efficiently.
We use high-speed steel materials such as SKD11 or DC53 for punches and dies to ensure the tooling lasts for hundreds of thousands or even millions of strokes.
Besides the die set, we design specialized mold bases, guide pillars, and locating pins to ensure precise operation on high-speed presses.
To improve productivity and reduce manual handling, we also design matching automatic feeding systems and lamination collection units for different product types.
In the diagram below, we show the progressive die structure we designed for Φ72.4 mm stator core. It uses a “step punching + automatic stacking” approach, forming the product in a single operation with ±0.02 mm tolerance. The laminations are flat and burr-free.
Fixture Design and Fabrication
We ensure accurate axial and radial positioning of the cores using locating pins, limit blocks, and V-shaped grooves. Both center-alignment and outer-diameter clamping methods are available. We use cylinders, hydraulic jacks, or screw clamps to ensure firm pressure between stator and rotor laminations without loosening.
Silicon Steel Stript Slitting
Silicon steel materials usually come in large coils, 500 mm to 1000 mm wide. Based on the die width, we slit the coils to the required dimensions.
For example, a die for a Φ30 mm stator may require a strip 45 mm wide. We use longitudinal shearing equipment to cut precisely and control the tight tolerance within ±0.1 mm to ensure smooth feeding without jamming the die.
During slitting, we also inspect the edges to prevent excessive burrs or warping that could affect stamping quality.
Progressive Stamping Process
Once slitting is complete, the strip enters a high-speed press, passing through multiple stations—blanking, punching, trimming, orienting, and stacking. This process completes motor stator and rotor laminations punching in a single pass. We commonly use high-speed presses like the JM36-400 and JDM MCP 400-330A, which can reach speeds of 600 strokes per minute.
For instance, when producing Φ145 mm stator laminations for a BLDC motor, our die stamps six pieces at a time, producing up to 3600 pieces per minute. The efficiency is remarkable. To reduce core loss, we include tooth-separating structures in the die design to optimize magnetic flux paths.
Would you like to see how fast this high-speed press works? Visit our factory to experience the “motor core lamination storm” in person.
Stator Rotor Core Lamination Forming
After stamping, we proceed with core forming based on customer requirements. Common stacking methods include:
Automatic stacking within the die (completed during stamping)
Self-locking structures (tooth-slot interlocks, typically used in small motors)
Laser welding
Bonding (self-adhesive or dipped bonding)
For example, in a recent European robot project, the customer requested self-bonded laminations. We applied adhesive automatically at the end of the stamping line, then heated and cured the stack. This process ensured strong bonding and achieved a stacking factor of over 96%.
Compression Forming
For motors that require high precision and high torque, we compress the laminated core after stacking. We use precision hydraulic presses to apply vertical pressure. This ensures tight bonding between layers, reduces magnetic circuit air gaps, and enhances motor performance.
Grinding
After compression, we lightly grind the end faces and outer diameter to remove burrs. This ensures smooth assembly and avoids interference during fitting.
Quality Inspection
Incoming Material Inspection:
We inspect the steel grade, coating thickness, and surface defects to ensure reliable raw material sources. We also perform Epstein testing on the silicon steel.
First Article Inspection:
For each batch, we inspect the first part thoroughly before mass production. We verify mold and machine parameters using appearance checks, CMM measurements, and 2D projectors.
In-Process Inspection:
During production, we sample parts at fixed intervals to check dimensions, burrs, and flatness. This ensures consistent batch quality.
Hardness Testing:
We conduct Rockwell or Vickers hardness tests on the die steel and motor cores to verify tool life and lamination performance.
Salt Spray Testing:
For export or special-use parts, we test corrosion resistance through salt spray tests that simulate marine or humid environments.
Final Inspection:
We perform comprehensive checks on the finished products, including appearance, dimensions, weight, and stacking height. Only qualified products go into inventory or get packed for shipment.
Documentation and Reports
For every batch of motor laminations, we establish a complete production and quality control record. This includes raw material batch numbers, mold numbers, equipment IDs, inspection data, and photo records. Upon request, we provide dimensional reports, inspection certificates, and material certifications to customers.
Progressive die stamping is a process that demands both technical precision and hands-on expertise. Every step reflects the dedication of engineers and technicians. Only by perfecting every silicon steel lamination can we deliver truly stable and high-performance motor core solutions to our customers.
Motor Lamination Stamping – Choose Lamnow
Lamnow specializes in providing a wide range of stamping services, including progressive die stamping, compound stamping, and rotary slotting. Our advanced facilities use cutting-edge technologies and precision tooling to produce high-quality motor laminations.
With deep expertise in various stamping techniques, we meet unique design requirements and help motors achieve optimal performance and efficiency.
Are you looking for a professional, reliable, and efficient motor, generator, and transformer lamination manufacturing partner? Feel free to contact us. Send us your drawings—we offer motor compound stamping, progressive stamping services and expert recommendations.
FAQ
What are the advantages of motor lamination progressive stamping?
High Production Efficiency:
Progressive dies complete multiple operations within a single press stroke. In contrast, single-station dies usually handle only one step, making progressive dies much more efficient.
Enhanced Operator Safety:
Since progressive stamping doesn’t require manual interaction with the die area, it significantly improves safety during operation.
Greater Tool Strength and Longer Die Life:
Progressive die design distributes tasks across stations, avoiding issues like “minimum wall thickness” in single dies. This results in stronger, longer-lasting tooling.
Higher Processing Accuracy:
Progressive dies eliminate manual feeding errors, improving overall part accuracy.
Automation-Friendly:
Progressive die setups are well-suited for automation, which reduces labor costs and enhances production consistency and stability.
Better Material Utilization:
The stepwise layout of progressive dies minimizes material waste and improves raw material efficiency.
Ideal for Complex Part Production:
Progressive dies are perfect for small to medium-sized parts with complex shapes and large volumes. A single die can handle multiple processes to ensure precision and part complexity.
What are the applications of progressive stamping stator rotor stacks?
BLDC Motor
Fan Motor
EV Motor
Segmented stator lamination for hub motor
Robotic Motor
Drone Motor
Industry Motor
