Metal Stamping: An Overview

Metal stamping transforms flat metal sheets into intricate forms through a detailed process, involving multiple metal shaping techniques such as cutting, punching, bending, and drilling.

This guide sheds light on typical methods and formulas used in metal stamping design, offering insights into cost-effective strategies for part fabrication.

Fundamentals of Stamping

The stamping process, also known as pressing, starts with placing flat metal sheets, either as coils or blanks, into a stamping press. Here, a combination of tools and dies shapes the metal into the desired form. Techniques like punching, cutting, bending, shaping, imprinting, and curving are employed to manipulate the metal.

Designing the tooling, using CAD/CAM engineering technology, is a prerequisite for shaping the material. Accuracy in these designs is crucial for maintaining precise clearances and ensuring high-quality output. Tool 3D models can be intricate, often comprising hundreds of components, making the design stage particularly intricate and labor-intensive.

After finalizing the tool design, manufacturers employ various methods like machining, grinding, wire EDM, among others, to complete the production process.

Metal Stamping Varieties

Metal stamping encompasses three primary techniques: progressive, fourslide, and deep draw stamping.

Progressive Die Stamping:

This method involves several stages, each performing a distinct function. Metal strips unroll from a coil into a press, where each station executes a unique cut, punch, or bend. These progressive actions cumulatively craft the final component.

Fourslide Stamping:

Fourslide stamping, also known as multi-slide, uses horizontal alignment with four distinct slides, each equipped with a tool for simultaneous shaping. This method is known for its intricate cutting and bending capabilities, ideal for complex designs. Its benefits include:

  • Enhanced design versatility
  • Flexible adaptation to design modifications
  • The capability of employing up to four tools for concurrent bending

Deep Draw Stamping:

Deep draw stamping pulls a metal blank into a die via a punch, shaping it. This technique is termed “deep drawing” when the depth of the part surpasses its diameter. It’s particularly suitable for components needing multiple diameters. Typical applications include:

  • Automotive and aircraft parts
  • Electronic components
  • Kitchen utensils and cookware

Short Run Stamping:

Optimal for prototypes or smaller projects, short run stamping minimizes initial tooling costs. The process involves using custom tooling components and die inserts for bending, punching, or drilling. While the per-piece cost may be higher due to the custom operations, the lower tooling expenses can make it a cost-effective choice for projects needing swift completion.

Stamping Production Tools

In the arena of metal stamping, a stamping parts manufacturer undertakes various steps. The initial phase is the design and creation of the tool necessary for product development.

This journey commences with the Stock Strip Layout & Design. Here, designers utilize their expertise to determine the strip’s dimensions, tolerances, feed direction, and focus on minimizing scrap.

Following this, Tool Steel and Die Set Machining takes center stage. CNC machining plays a crucial role in this process, ensuring a high level of precision and repeatability, especially for complex dies. Equipment like 5-axis CNC mills and wire EDM machines are employed to cut through hardened tool steels with tight tolerances.

The process then moves to Secondary Processing. This includes heat treating to enhance the strength and durability of metal parts for their intended application. Grinding is also used to achieve high surface quality and dimensional accuracy in parts.

Finally, Wire EDM (Wire Electrical Discharge Machining) is used. This process involves shaping metal materials with an electrically-charged strand of brass wire. Wire EDM is adept at cutting intricate shapes, including small angles and fine contours, which are essential in the manufacturing of stamping parts.

Metal Stamping Design Techniques

Metal stamping integrates several metal forming processes like blanking, punching, bending, and piercing. Here’s an overview of key aspects:

Blanking:

This initial stage involves cutting the basic shape of the product, with a focus on minimizing burrs, which can increase costs and lead times. Decisions made here include hole diameter, geometry, taper, and the spacing between edges and holes.

Bending:

Designing bends in metal stamping requires adequate material provision. Key considerations include:

  • Avoiding bends near holes to prevent deformation.
  • Ensuring notches, tabs, and slots are at least 1.5 times the material’s thickness to avoid punch breakage.
  • Incorporating a radius in each corner of the blank, at least half the material thickness, to reduce burr severity.

Coining:

This process flattens or breaks the burr edges, enhancing smoothness and strength in localized areas, potentially reducing the need for secondary processes like deburring and grinding. Remember to consider:

  • Material plasticity and grain direction, vital for high-strength materials to prevent cracking along bends.

Bend Distortion/Bulge:

Bend distortion can cause bulging up to half the material thickness. The effect intensifies with thicker materials and smaller bend radii.

Carrying Web and ‘Mismatch’ Cut:

This involves slight alterations (about 0.005” deep) in the part’s shape, essential in progressive die tooling but not in compound or transfer tooling.

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