How Does stamping metal parts Work?

A stamping press is a metalworking machine tool used to shape or cut metal by deforming it with a die. A stamping press uses precision-made male and female dies to shape the final product. It is a modern-day counterpart to the hammer and anvil.

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Components

A press has a bolster plate, and a ram.[1] Presses come in various types of frame configurations, C-Frame where the front & left and right sides are open, straight-side, or H-Frame for stronger higher tonnage applications. It is very important to size the press and tonnage based on the type of applications, blanking, forming, progressive, or transfer. Strong consideration should be given to avoiding off-center load conditions to prevent premature wear to the press.

Bolster Plate

The bolster plate is mounted on top of the press bed and is a large block of metal upon which the bottom portion of a die is clamped; the bolster plate is stationary. Large presses (like the ones used in the automotive industry) may be equipped with die cushions integrated in the bolster plate to apply blank holder or counter draw forces. This is necessary when a single acting press is used for deep drawing. The ram / slide is the moving or reciprocating member that the upper die is mounted to. Ram or Slide guidance is a critical element to assure long die life between die maintenance. Different types of slide guides are available, 4 point V-Gibs or 6 point square gibs on smaller presses and 8 point full length slide guides on larger straight side frame presses. The dies and material are fed into the press between the bolster and slide. Good press designs must account for plastic deformation, otherwise known as deflection when frame design and loads are considered.[2]

Ram / Slide

The vertical motion of the slide acts like a hammer to an anvil. The most common Mechanical Presses use an eccentric drive to move the press's ram slide, length of stroke or slide travel depends on the crankshaft or eccentric, whereas hydraulic cylinders are used in hydraulic presses. The nature of drive system determines the force progression during the ram's stroke. Mechanical presses have a full tonnage rating point above BDC / Bottom Dead Center, normal full tonnage rating points are .187", .25" & .5". Hence a mechanical press has a tonnage curve and should be operated within the press capacity limits. Link Motion mechanical is yet another option, this provides a slide slow down near BDC / bottom dead center for soft touch tooling. This link feature can improve die life and reduce reverse-snap thru tonnage for blanking operations.[3]

On the contrary, Hydraulic Presses do not have a tonnage curve and can produce full tonnage at any point in the stroke. The trade-off is speed, a mechanical press is much faster when compared to hydraulic. On the other hand, Hydraulic Presses are much more practical for deep forming or drawing or parts or when dwell time at the bottom is desired.

Another classification is single-acting presses versus double- (seldom triple) acting presses. Single-acting presses have one single ram. Double-acting presses have a subdivided ram, to manage, for example, blank holding (to avoid wrinkles) with one ram segment and the forming operation with the second ram segment.[4]

Other Components & Controls

Typically, presses are electronically linked (with a programmable logic controller) to an automatic feeder which feeds metal raw material through the die. The raw material is fed into the automatic feeder after it has been unrolled from a coil and put through a straightener. A tonnage monitor may be provided to observe the amount of force used for each stroke. [5]

References

Types of Metal Stamping

There are three major types of metal stamping techniques: progressive, fourslide and deep draw.

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 onto 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 a 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

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.

Fourslide 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 fourslide 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 fourslide, it is bent in quick succession by each shaft that is equipped with a tool.

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.

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