Understanding Metal Stamping

Understanding Metal Stamping
Posted by bnui4ui on 2021/09/02
Understanding Metal Stamping

    Understanding Metal Stamping

    Metal stamping is a cold-forming process that makes use of dies and stamping

presses to transform sheet metal into different shapes. Pieces of flat sheet metal, typically referred to as blanks, is fed

into a sheet metal stamping press that uses a tool and die surface to form the metal into a new shape. Production facilities

and metal fabricators offering stamping services will place the material to be stamped between die sections, where the use of

pressure will shape and shear the material into the desired final shape for the product or component.

    This article describes the metal stamping process and steps, presents the types of stamping presses typically employed,

looks at the advantages of stamping parts compared to other

fabrication processes, and explains the different types of stamping operations and their applications.

    Basic Concepts of Metal Stamping


    Metal stamping, also referred to as pressing, is a low-cost high-speed manufacturing process that can produce a high

volume of identical metal components. Stamping operations are suitable for both short or long production runs, and be

conducted with other metal forming operations, and may consist of one or more of a series of more specific processes or

techniques, such as:

    1. Punching


    2. Blanking


    3. Embossing


    4. Coining


    5. Bending


    6. Flanging

    Punching and blanking refer to the use of a die to cut the material into specific forms, such as

pole line hardware. In punching operations, a scrap piece of

material is removed as the punch enters the die, effectively leaving a hole in the workpiece. Blanking, on the other hand,

removes a workpiece from the primary material, making that removed component the desired workpiece or blank.

    Embossing is a process for creating either a raised or recessed design in sheet metal, by pressing the raw blank against

a die that contains the desired shape, or by passing the material blank through a roller die.

    Coining is a bending technique wherein the workpiece is stamped while placed between a die and the punch or press, such

as sheet metal fabrication. This action causes the punch

tip to penetrate the metal and results in accurate, repeatable bends. The deep penetration also relieves internal stresses in

the metal workpiece, resulting in no spring back effects.

    Bending refers to the general technique of forming metal into desired shapes such as L, U, or V-shaped profiles. The

bending process for metal results in a plastic deformation which stresses above the yield point but below the tensile

strength. Bending typically occurs around a single axis.

    Flanging is a process of introducing a flare or flange onto a metal workpiece through the use of dies, presses, or

specialized flanging machinery.

    Metal stamping machines may do more than just stamping; they can cast, punch, cut and shape metal sheets. Machines can be

programmed or computer numerically controlled (CNC) to offer high precision and repeatability for each stamped piece, and

this technology is widely used in furniture hardware. Electrical

discharge machining (EDM) and computer-aided design (CAD) programs ensure accuracy. Various tooling machines for the dies

used in the stampings are available. Progressive, forming, compound, and carbide tooling perform specific stamping needs.

Progressive dies can be used to create multiple pieces on a single piece simultaneously.

    Types of Stamping Operations


    Progressive die stamping


    Progressive die stamping uses a sequence of stamping stations. A metal coil is fed into a reciprocating stamping press

with progressive stamping dies. The die moves with the press, and when the press moves down the die closes to stamp the metal

and form the part. When the press moves up, the metal moves horizontally along to the next station. These movements must be

precisely aligned as the part is still connected to the metal strip. The final station separates the newly-fabricated part

from the rest of the metal. Progressive die stamping is ideal for long runs, because the dies last a long time without

becoming damaged, and the process is highly repeatable. Each step in the process performs a different cut, bend, or punching

operation on the metal, thus gradually achieving the desired end-product shape and design. It is also a faster process with a

limited amount of wasted scrap.   

    Transfer Die Stamping


    Transfer die stamping is similar to progressive die stamping, but the part is separated from the metal trip early on in

the process and is transferred from one stamping station to the next by another mechanical transport system, such as a

conveyor belt. This process is usually used on larger parts that may need to be transferred to different presses.

    Four-Slide Stamping


    Four-slide stamping is also called multi-slide or four-way stamping. This technique is best-suited for crafting complex

components that have numerous bends or twists. It uses four sliding tools, instead of one vertical slide, to shape the

workpiece through multiple deformations. Two slides, or rams, strike the workpiece horizontally to shape it, and no dies are

used. Multi-slide stamping can also have more than four moving slides.

    Four-slide stamping is a very versatile type of stamping, such as in electronics hardware, as different tools can be attached to each slide. It also has a relatively low cost,

and production is fast.

    Fine Blanking


    Fine blanking, also known as fine-edge blanking, is valuable for providing high accuracy and smooth edges. Usually done

on a hydraulic or mechanical press, or by a combination of the two, fine blanking operations consist of three distinct

movements:


    Clamping of the workpiece or work material in place


    Performance of the blanking operation


    Ejection of the finished part


    Fine blanking presses operate at higher pressures than those used in conventional stamping operations, hence tools and

machinery need to be designed with these higher operating pressures in mind.

    The edges that are produced from fine blanking avoid fractures as produced with conventional tooling and surface flatness

can exceed that available from other stamping methods. Since it is a cold extrusion technique, fine blanking is a single-step

process, reducing the overall costs of fabrication.

    Types of Stamping Presses


    The three common types of stamping presses include mechanical, hydraulic, and mechanical servo technologies. Usually,

presses are linked to an automatic feeder that sends sheet metal through the press either in coil or blank form. 

    Mechanical


    Mechanical presses use a motor connected to a mechanical flywheel to transfer and store energy. Their punches can range

in size from 5mm to 500mm, depending on the particular press. Mechanical pressing speed also varies, usually falling between

the range of twenty and 1,500 strokes per minute, but they tend to be faster than hydraulic presses. These presses can be

found in an array of sizes that stretch from twenty to 6,000 tons. They are well-suited for creating shallower and simpler

parts from coils of sheet metal. They’re usually used for progressive and transfer stamping with large production runs.

    Hydraulic


    Hydraulic presses use pressurized hydraulic fluid to apply force to the material, such as in

agricultural machinery parts. Hydraulic pistons

displace fluid with a force level proportional to the diameter of the piston head, allowing for an advanced degree of control

over the amount of pressure, and a more consistent pressure than a mechanical press. Additionally, they feature adjustable

stroke and speed capabilities, and can typically deliver full power during any point in the stroke. These presses usually

vary in size from twenty to 10,000 tons and offer stroke sizes from about 10mm to 800mm.

    Hydraulic presses are usually used for smaller production runs to create more complicated and deeper stampings than

mechanical presses, such as car spare parts. They allow for more

flexibility because of the adjustable stroke length and controlled pressure.


    Mechanical Servo


    Mechanical servo presses use high capacity motors instead of flywheels. They are used to create more complicated

stampings at a faster speed than hydraulic presses. The stroke, slide position and motion, and the speed are controlled and

programmable. They are powered by either a link-assisted drive system or a direct drive system. These presses are the most

expensive of the three types discussed.


   



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