How are motor laminations made? Key technical requirements for motor lamination include material selection, manufacturing methods, and various technical processes such as pressing and bonding.
These processes directly influence the motor’s magnetic properties and performance, especially in high-frequency environments where core loss and stability are critical.
What Is The Motor Core?
A motor core consists mainly of the stator core and the rotor core. The stator core is the key part of the motor’s magnetic circuit and is usually made from silicon steel sheets to house the windings. The rotor core, separated from the stator core by an air gap, completes the motor’s magnetic circuit.
How is the motor core manufactured?
Manufacturing Motor Laminations Process
Material Preparation
Silicon Steel
Silicon steel is commonly used for the production of motor stators and rotors, with silicon content ranging from 1.0% to 6.5%. Based on crystal orientation, electrical steel is divided into oriented and non-oriented grades.
Where are oriented and non-oriented electrical steels used in motor cores?
Oriented electrical steel is most commonly used for transformer cores. The common lamination thicknesses are 0.1mm, 0.18mm, 0.23mm, 0.27mm, 0.3mm, and 0.35mm.
Non-oriented silicon steel sheets are mainly used in motor and generator cores. The common lamination thicknesses are 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.27mm, 0.3mm, 0.35mm, and 0.5mm.
| 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 |
In addition to lamination thickness, customers also consider core loss and lamination factors when selecting silicon steel materials. Generally, thinner laminations result in lower core loss and eddy currents, and better motor performance.
For example, Xiaomi’s HyperEngine V8s electric motor uses 0.2mm thick stator laminations and 0.35mm thick rotor laminations to improve performance. Tesla’s Model 3D6 uses 0.28mm laminations.
Besides silicon steel, emerging amorphous alloys are increasingly used in motor cores. What are their characteristics?
Amorphous Alloys
Amorphous alloys typically have lamination thicknesses of 0.025mm. Compared to silicon steel, amorphous alloys have lower density, thinner thickness, smaller size, and lighter weight. They also feature high magnetic permeability, high resistivity, low loss, and low coercivity.
Common silicon steel grades include 2605HB1M and 1K101. Amorphous materials can reduce motor core loss by 80%-93%. Let’s compare amorphous cores with 0.28mm silicon steel cores.
| Material | Loss（W/kg） | |||
| P(50hz,1.4T) | P(400hz,1.4T) | P(800hz,1.4T) | P(1200hz,1.4T) | |
| Silicon Steel Core | 2.04 | 33.7 | 104.4 | 206.3 |
| Amorphous Alloy Core | 0.37 | 3.67 | 8.4 | 14 |
Cobalt Alloys
Iron-cobalt alloys are used for applications requiring corrosion resistance, wear resistance, and heat resistance. Common grades include 1J22, Vacodur 49, Hiperco 50, and IMPHY AFK 502. Their thickness range is from 0.1mm to 0.5mm.
Nickel Alloys
Iron-nickel laminations maintain consistent magnetic permeability in low to medium induction environments, with minimal core loss. Common grades include 1J85, HyMu80, HiPerm 49, ULTRAVAC 80, Permenorm 5000 V5, VDM MAG 7940, and VDM MAG 50. The thickness range is from 0.1mm to 0.5mm.
Soft Magnetic Composite Materials
Soft magnetic composite (SMC) materials consist of both magnetic and non-magnetic components. The magnetic materials mainly include ferrite, iron-fluorine, and iron-silicon-aluminum, which have high permeability and hysteresis loss. Non-magnetic components, like oxides, calcium carbonate, and resins, enhance strength, reduce hysteresis loss, and control permeability.
Common SMC materials include Somaloy® 700HR 1P, Somaloy® 700HR 3P, and Somaloy® 700HR 5P. Currently, soft magnetic composite materials are primarily used in axial flux stator cores and transformer cores.
Prototype Lamination- Cut the Lamination Techniques
For prototype creation and small batch production, laser cutting and wire cutting processes are commonly used. These methods save on mold costs compared to stamping. The lead time is 15-35 days.
How does laser cutting design cut silicon steel sheets?
Laser Cutting
Laser cutting technology has become a key method for achieving high-precision, high-efficiency processing. It can reach micron-level precision. The lamination thickness typically ranges from 0.1mm to 0.5mm.
the CAD file is sent to the laser cutting machine, which uses a high-powered laser to cut the desired shape and size from the metal sheet. Like stamping, this process is repeated, and eventually, all the rotor laminations are bonded together to form the electric motor core.
Wire Cutting (Fast, Medium, Slow)
The process is used to produce motor laminations due to its ability to manufacture precise and intricate designs accurately and consistently. it can achieve a high accuracy tolerance of +/- 0.05mm.
This process generates electrical sparks between the wire and the workpiece (motor core), eroding the material for precise cutting. It typically cuts thicker (stacked) motor cores rather than single sheets.
Wire cutting is usually divided into three speeds: high, medium, and low. High-speed wire cutting has the lowest precision, while low-speed wire cutting provides higher accuracy. The lamination thickness for stator and rotor cutting typically ranges from 0.1mm to 0.5mm, and the maximum core outer diameter can reach 500mm.
Motor Lamination Stamping Die Manufacturing
The die is the core component of the stamping process and determines the quality of the stamped parts. Controlling burrs is crucial.
How are stamping dies designed and manufactured?
(1) Design the stamping die using CAD or 3D software based on customer drawings. This includes the structural design of the die and the design of its components.
(2) Select the materials for manufacturing the stamping die. Common materials for die working parts include carbon tool steel, low alloy tool steel, high-speed steel, stainless steel, and others.
(3) The die manufacturing process includes electrical discharge wire cutting, machining, and heat treatment. Wire cutting mainly handles more complex parts of the die. Machining typically handles the flat surfaces, slopes, grooves, and shafts of the die. Heat treatment improves the die’s hardness, wear resistance, and toughness.
(4) Assembly and debugging: Assemble the parts according to the design drawings in sequence.
What are the differences between stamping dies? Below is a comparison of stamping molds of progressive dies, compound dies, and soft dies.
| Tooling Type | Tooling Material | Stamp steps | Tooling cost | Stamping speed(/Minutes) | Life | Burrs | Tolerance | Concentricity | Lamination thickness |
| Progressive die | SKD11 | 4-20 | $2k-$6k | 200-600 strikes | 50-200 Million | <0.02 | ±0.01 | 0.02mm | 0.1-0.5mm |
| Compound die | SKD11 | 2-5 | $4k-$12k | 50-60 strikes | 300-500K | <0.05 | ±0.03 | 0.05mm | 0.2-0.5mm |
| Single soft die | Tungsten Steel | 1 | >$10k | 50-60 strikes | 300-500K | <0.06 | ±0.01 | 0.05mm | 0.2-0.5mm |
Stamping Motor Laminations
For stators and rotors with high-volume production, stamping technology is commonly used. This process significantly reduces costs. What stamping processes are used for motor cores, and what are the differences between them?
Progressive Stamping
In progressive stamping, silicon steel coils are cut to the required width and then fed directly into a high-speed press. Unlike other stamping methods, this tool has a complex internal structure with multiple tools, each completing a different step. so that it can meet the desired specifications of the stator lamination.
The progressive die has an interlocking area to connect each lamination together, forming a complete core.
This process is ideal for small diameter but large volume stator and rotor laminations. Progressive dies can be single or multi-column, capable of producing large quantities in a short time, making it highly suitable for mass production.
Compound Stamping
Compound stamping produces complete stator or rotor laminations in one step. This process uses automated feeding and stamping equipment, greatly improving production efficiency. Laminations produced with compound stamping have good flatness and concentricity. It is a cost-effective choice for mass production of medium to large motor laminations.
Axial Stamping
Axial stamping motor core technology differs from traditional stamping. This process only requires stamping the shape and size of the axial magnetic flux stator slots with a stamping die. The rolling machine system operates synchronously with the stamping die through a PLC computer system. The stator core is then formed by winding.
To learn more about “How to Produce Axial Flux Stator Lamination” click the link to read further.
Helical Stamping
This process is used for manufacturing stator cores and reduces material waste. It mainly involves stamping the slot shape and size of the stator with a stamping die, then spirally winding strip laminations and integrating them to form the complete stator core.
Single Slot Stamping (Rotary Stamping)
For large motor laminations, single-slot stamping is typically used. This method employs a CNC rotary slotting machine with a high-precision positioning system and indexer. The die precisely cuts each slot on circular silicon steel sheets. Compared to compound stamping, this is also a good choice for stamping.
Motor Lamination Stacking Technology
How is laminate formed into a complete motor core using compound stamping, laser cutting, and wire cutting?
Interlocking
This process is the most common method for mass-producing stator and rotor cores. It allows stacking inside progressive dies, greatly improving production efficiency. The interlocking points can be rectangular or circular.
Welding
This technique is typically used for custom prototype samples and large laminations with high torque. Welding methods include laser welding, TIG welding, MIG welding, and spot welding. Laser welding motor stator laminations is the most commonly used because it provides a narrow welding area.
Bonding
This process mainly includes two methods: adhesive bonding and self-bonding thin metal sheet. The key difference is whether the bonding agent is pre-applied. The adhesive bonding process involves cutting and shaping the laminations, then applying adhesive for curing. The self-bonding method uses silicon steel sheets with pre-applied bonding agents, curing the cut stator or rotor laminations. This method does not require interlocking or welding, minimizing core loss.
Riveting
This process uses rivets to secure motor laminations. Its cost is higher than that of laser welding.
Cleating
This technique uses long strips of silicon steel to stack and shape the stator core. It is mainly used for large motor laminations and ventilation plate laminations.
If you want to learn more about stacking technologies, read “Several Methods of Motor Core Lamination Stacking.“
Motor Iron Core Insulation Technology
When it comes to stator core lamiantion insulation technology, it is truly an art. How should you choose between epoxy coating, insulation paper, and injection molding?
Epoxy Coating
The epoxy coating process for stators includes manual coating and automated electrostatic coating. Manual coating thickness ranges from 0.25mm to 0.7mm, while automated electrostatic coating achieves thicknesses from 0.1mm to 0.4mm.
Materials used in this process include 3M series and JY231, with temperature ratings of B, F, and H. Coating colors include green and blue.
Insulation Paper
The commonly used insulation paper in China is the AMA series. This insulation paper is a soft composite material with a polyester film coated with imported adhesive that withstands up to 200°C. Both sides are made of fire-resistant fiber insulation paper, forming a three-layer insulation sheet. Its insulation grade is Class C, with a temperature resistance of 200°C. The thickness ranges from 0.14mm to 0.45mm.
Injection Molding Insulation
Injection molding insulation is not the best choice during the sample production phase. However, it works well for mass production of small brushless motor stator cores.
This process involves injecting molten material (typically thermoplastic plastic) into a precisely designed mold cavity under high pressure. The mold is carefully made to form the desired stator core lamination shape, and the plastic cools and solidifies inside the mold.
For prototype designs, 3D-printed skeletons are typically used for insulation. 3D printing is widely applied to axial stator core designs.
Stator Winding Technology
Winding technology is the final step in stator production, and it includes manual winding and automated winding. Winding types include concentrated winding, distributed winding, and flat wire winding.
Concentrated Winding
This technique means each coil (or part of the winding) is concentrated in a specific stator slot or tooth. In this method, each coil typically surrounds one stator tooth or occupies one stator slot.
Concentrated winding is most commonly used in brushless stator cores and hub motor stator cores.
Distributed Winding
This process distributes coils across multiple stator teeth. These windings span at least two teeth, called coil pitch or step, and can span three, four, five, or more teeth.
Distributed winding is mainly used in induction motor stators and permanent magnet synchronous motor stators.
Flat Wire Winding
This technique is a new winding method that has gained popularity in recent years, primarily used in new energy electric vehicle motor cores. Flat wire winding includes hairpin, I-shaped, X-shaped, and S-shaped configurations. Compared to traditional round wire winding, this method greatly improves slot filling, achieving a slot filling rate of 94%.
If you want to learn more about winding, read the article “Stator Winding.”
Rotor die casting
Speaking of rotor die casting, the most commonly used is aluminum die casting. Due to production cost issues, copper die casting is rarely used at present.
There are two most commonly used manufacturing processes for die casting. One is to melt aluminum or copper and inject it into a mold with a rotor core. The other is to install and weld aluminum or copper end rings and aluminum conductive bars to the rotor.
We can customize die casting according to customer drawings. The main shapes are ring, balance column, fan blade, and can also be freely combined.
Annealing And Heat Treatment Process
The annealing and heat treatment process of the motor core plays a vital role in the motor manufacturing process. Main purpose is to improve the performance of the material and eliminate stress. The core is to change the microstructure of the silicon steel sheet material in the core through high-temperature heating, thereby optimizing the magnetic properties.
Each manufacturing process will affect the performance of the motor. Therefore, the manufacturing process of the stator and rotor core should be selected according to the motor design.
Producing Motor Laminations – Choose Lamnow
Lamnow has many years of experience in manufacturing core lamination for electric motors and generators. Whether it is prototype or mass production, we can provide suitable processes according to customer needs.
We can provide a full range of production processes, wire cutting, laser cutting, stamping, gluing, laser welding, interlocking, insulation, winding, and die casting.
Our lamination stacks are widely used EV motors, pump motors, drone motors, industrial machinery motors, and wind power motors. If you need custom rotor and stator lamination, please contact us today.
