Electrical Stamping Explained: Metal Stamping

Stamping is cutting or forming thin sheet workpieces into parts of various shapes and sizes.

Electrical stamping is a metal stamping process in which thin sheets of steel, brass, or copper undergoes cutting operations like punching, blanking, coining, etc. The cut-out metal laminates from the sheets are stacked and glued by specialized tool dies to form the core of electrical components like motors.

But why is it called electrical stamping? Is it only used in the electrical industry?

This article discusses the process, techniques, and applications of electrical stamping.

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Electrical Stamping: Why is it Done?

Electrical stamping is similar to die punches and is used to produce parts with desired cut sections and bends.

It is a special sheet metal tool that is used to cut thin workpieces with extremely high accuracy.

The performance of an electric motor depends on its rotor and stator cores. These cores are built from thin layers of high-conductive electrical steel laminates bonded together.

They help minimize eddy current loss and are vital parts in the electrical and automotive industries.

Eddy current loss is the amount of heat energy lost or dissipated when an electric current passes through the core.

The laminates used in industrial motors are complex in shape. They have many intricate features which play a crucial role in cooling the cores.

The electrical stamping process is an ideal technique to make such complex cuts on sheet metals.

Electrical Stamping Process Explained

Stamping machines used in the electrical stamping process are equipped with progressive dies that can cut intricate and complex shapes of the motor laminates.

Progressive Stamping

The progressive die consists of sequentially arranged dies that perform different cutting and forming operations.

Here, the sheet workpieces pass through a series of dies placed on a common press.

As the name indicates, the process involves progressive steps of pressing the sheet to obtain the desired shape.

The press carrying these dies performs specific operations like cutting, bending, stacking, and interlocking/gluing the metal laminates.

The key advantage of using a progressive die is it reduces material wastage and boosts production.

Operations

The commonly adopted metal-cutting or metal-forming operations used in electrical stamping jobs are blanking, piercing, coining, punching, flanging, and laminating.

Blanking and Piercing

Blanking is cutting the required shape of the workpiece out of the base material.

Piercing is the process of cutting the base material, thus leaving behind a hole in the workpiece. The cut-out part is considered scrap material.

Both these processes involve sheet metal shearing to perform a clean cut in the workpiece.

Coining

Coining is a metal stamping process in which the metal under the high pressure of the punch undergoes a plastic flow, thereby taking the shape of the die.

Flanging

Flanging is a process of creating a right-angled bend over the edge of a part.

Laminating

Laminating is when two or more metal laminates are bonded using a bonding resin.

Motor Stamping Process

Making motor laminations is a major part of electrical stamping jobs.

Here, thin sheets of electrical steel are passed from one die/stage to another, wherein each die performs a specified operation.

In the initial stages, the die performs metal-cutting operations such as piercing, coining, punching, etc.

Before the laminate is cut out from the base sheet, it is passed through an adhesive-coated stamping die that glues and interlocks the laminates.

Once the laminates are cut out, they are stacked and thermally bonded by applying heat. This further hardens the bond, forming a stable core.

This technique allows thin gauge laminates to be bonded with tight tolerance, thereby retaining the magnetic properties of the base metal.

It also improves the part's quality and reduces machining costs, allowing the production of huge volumes of mechanically stable laminate parts that do not slip against each other.

Many manufacturers employ numerical control systems to change the stacking height of the laminates without bringing the machine to a halt.

It also lets you make metal laminate layers that are skewed or rotated based on the need.

Unfortunately, making unique dies for such jobs is a complex task. Strong and precise dies play a vital role in producing such laminates.

Applications of Electrical Stamping

Electrical stamping has applications in many different electrical components, but its major use is making rotor and stator cores.

Fields such as the automotive sector, aerospace, windmill industry, and household appliances largely use stamped electrical components.

For example, the motors used on fans and mixer grinders have stamped and laminated electrical parts as their integral components.

Pole shoe stampings, armature stampings, alternators, and submersible motor stampings are made using electrical stamping as it offers good strength and reduced magnetic induction.

The electrical stamping process has a major role in making components for data communications, medical devices, and telecommunications.

Final Thoughts

Electrical stamping, commonly referred to as motor stamping, is a unique process specially designed to make rotor and stator cores for motors.

Besides the regular cutting and forming operations performed in a stamping process, electrical stamping incorporates additional operations like stacking and laminating.

The progressive dies can perform all the required motor stamping operations.

Also, with the integration of numerical control, manufacturers can efficiently make cores of different stacking heights.

Frequently Asked Questions (FAQ)

What are the materials commonly used in metal laminates?

Cobalt, silicon steel, and nickel alloy are common materials used in metal laminates. A metal alloy of 50% cobalt with 2% vanadium is ideal for making laminates as it offers high flux density and tensile strength.

Are stamped laminates used in a transformer?

Yes, stamped laminates are used in making a transformer as it requires high strength and magnetic saturation for its proper working. Precisely cut and tightly bonded metal laminates can provide such properties.

What is the size range of electrical stamped products?

Parts with a wide range of sizes can be stamped using electrical stamping. Commercial electrical stamping jobs usually range between 30mm and 1300mm.