What Is Stamping?
Stamping or pressing is a manufacturing process used to convert flat metal sheets into final shapes. In this process, a flat sheet of metal, either in the form of a blank or in the form of a coil, is placed in a stamping press where a tool and die surface forms the metal into a final shape.
Stamping encompasses a variety of sheet metal forming manufacturing processes, such as punching using a machine press or stamping press, blanking, embossing, bending, flanging, and coining.
This could be a one-step process where each stroke of the press creates the desired shape on the sheet metal part, or it could be done through a series of steps. The process is usually carried out on sheet metal, but can also be used on other materials such as polystyrene.
Progressive dies are commonly fed from a coil of steel, coil reel for an unwinding of the coil to a straightener to level the coil and then into a feeder which advances the material into the press and dies at a predetermined feed length. Depending on part complexity, the number of stations in the die can be determined.
Stamping is usually done on cold metal sheets. See Forging for hot metal forming operations.
A Brief History
It is believed that the first coins came from the 7th century BC. Were coined by the Lydians in what is modern-day Turkey. Coin hammering remained the most important method of coin production until 1550. Marx Schwab in Germany developed a new stamping process in which up to 12 men turned a large wheel to press metal into coins. The punching process was further innovated in the 1880s.
Stamped parts were used for mass-produced bicycles in the 1880s. Stamping replaced die forging and machining, resulting in greatly reduced costs. Although they weren’t as strong as die-forged parts, they were of sufficient quality.
In 1890, stamped bicycle parts were imported from Germany to the USA. US companies then began to have stamping machines made to measure by US machine tool manufacturers. Through research and development, Western Wheel was able to stamp most of the bicycle parts.
Several automobile manufacturers have adopted the stamping of parts. Henry Ford defied his engineers’ recommendations to use stamping parts, but when his company failed to meet demand with die forging, Ford was forced to use stamping parts.
In the history of metal stamping, forging, and deep drawing, presses of all kinds are the backbones of metal manufacturing. The processes are further improved by moving more metal in one press stroke. Press and interconnected automation devices increase production rates, reduce labor costs and provide more safety for workers.
In today’s metal stamping environment, controls such as I-PRESS with Connected Enterprise can record history, send reports, or the I-PRESS & Automation control can be viewed from remote or mobile devices. A new trend in gathering information about today’s production for historical data.
Types of Metal Stamping
There are three major types of metal stamping techniques: progressive, four-slide, and deep draw.
1. Progressive Die Stamping
Progressive die stamping features a number of stations, each with a unique function.
First, strip metal is feds through a progressive stamping press. The strip unrolls steadily from a coil and into the die press, where each station in the tool then performs a different cut, punch, or bend. The actions of each successive station add to the work of the previous stations, resulting in a completed part.
A manufacturer might have to repeatedly change the tool on a single press or occupy a number of presses, each performing one action required for a completed part. Even using multiple presses, secondary machining services were often required to truly complete part. For that reason, progressive die stamping is the ideal solution for metal parts with complex geometry to meet:
- Faster turnaround
- Lower labor cost
- Shorter run length
- Higher repeatability
2. Fourslide Stamping
Fourslide, or multi-slide, involves horizontal alignment and four different slides; in other words, four tools are used simultaneously to shape the workpiece. This process allows for intricate cuts and complex bends to develop even the most complex parts.
Four slide metal stamping can offer several advantages over traditional press stamping that make it an ideal choice for many applications. Some of these advantages include:
- Versatility for more complex parts
- More flexibility for design changes
As its name implies, a four-slide has four slides meaning that up to four different tools, one per slide, can be used to achieve multiple bends simultaneously. As material feeds into a four-slide, it is bent in quick succession by each shaft that is equipped with a tool.
3. Deep Draw Stamping
Deep drawing involves pulling a sheet metal blank into the die via a punch, forming it into a shape. The method is referred to as “deep drawing” when the depth of the drawn part exceeds its diameter.
This type of forming is ideal for creating components that need several series of diameters and is a cost-effective alternative to turning processes, which typically require using up more raw materials. Common applications and products made from deep drawing include:
- Automotive components
- Aircraft parts
- Electronic relays
- Utensils and cookware
Short Run Stamping
Short-run metal stamping requires minimal upfront tooling expenses and can be an ideal solution for prototypes or small projects. After the blank is created, manufacturers use a combination of custom tooling components and die inserts to bend, punch or drill the part.
The custom forming operations and smaller run size can result in a higher per-piece charge, but the absence of tooling costs can make short-run more cost-efficient for many projects, especially those requiring fast turnaround.
Stamping Operation
Stamping also called pressing involves placing flat sheet metal, in either coil or blank form, into a stamping press. In the press, a tool and die surface form the metal into the desired shape. Punching, blanking, bending, coining, embossing, and flanging are all stamping techniques used to shape the metal.
- Bending – the material is deformed or bent along a straight line.
- Flanging – the material is bent along a curved line.
- Embossing – the material is stretched into a shallow depression. Used primarily for adding decorative patterns. See also Repoussé and chasing.
- Blanking – a piece is cut out of a sheet of the material, usually to make a blank for further processing.
- Coining – a pattern is compressed or squeezed into the material. Traditionally used to make coins.
- Drawing – the surface area of a blank is stretched into an alternate shape via controlled material flow. See also deep drawing.
- Stretching – the surface area of a blank is increased by tension, with no inward movement of the blank edge. Often used to make smooth auto body parts.
- Ironing – the material is squeezed and reduced in thickness along a vertical wall. Used for beverage cans and ammunition cartridge cases.
- Reducing/Necking – used to gradually reduce the diameter of the open end of a vessel or tube.
- Curling – deforming material into a tubular profile. Door hinges are a common example.
- Hemming – folding an edge over onto itself to add thickness. The edges of automobile doors are usually hemmed.
Piercing and cutting can also be performed in stamping presses. Progressive stamping is a combination of the above methods done with a set of dies in a row through which a strip of the material passes one step at a time.
Benefits of Metal Stamping
If you need a metal part, component or product created, there are many advantages of partnering with a company that offers the services of metal stamping machines.
1. Precision
If your product needs to be cut with high accuracy, a stamping company will have the tools and processes in place to do so. Cutting a shape with such precision can be a large expense and it can be tempting to lower costs by lacking in this area of production. A stamping company allows for a higher quality product at a lesser price.
2. Consistency
Some businesses would tell you that consistent precision is only guaranteed by cutting pieces one-by-one, but most top metal companies agree that this isn’t true.
Consistency in mass production can be achieved by carefully controlling the entire process, starting with precise, computer-aided design (CAD), proper tooling, professionally operated metal stamping machines, as well as quality control to inspect each piece or part and to ensure uniformity in products.
3. Mass production
This one speaks for itself. Need a large number of quality products? Hire a company that has the machinery and tools to manage your project in a quick and efficient manner.
4. Workspace
If you outsource your stamping to a company outside of your own, then there is no need to allocate time and space in your own place of business to make those products.
Plus, it allows you to focus on the other aspects of your business and not get bogged down with the intricacies of production.
Application of Metal Stamping
Metal stamping can be applied to a variety of materials based on their unique metalworking qualities for a number of applications across a wide range of industries. Metal stamping may require the forming and processing of base common metals to rare alloys for their application-specific advantages.
Some industries require the electrical or thermal conductivity of beryllium copper in areas such as aerospace, electrical, and the defense industry, or the high-strength application of steel and its many alloys for the automotive industry.
The industries that employ metal stamping companies include (but are not limited to):
- Automotive
- Industrial Machinery
- Consumer Electronics
- Aerospace
- Electrical
- Telecommunication