Sheet metal fabrication is an important manufacturing process integral to modern industry. It is the method by which flat metal sheets are transformed into functional parts and structures, a technique essential to the production of a wide array of products across multiple industries.
What is Sheet Metal Fabrication?
Sheet metal fabrication is the process of shaping flat metal sheets into functional parts or structures. It's a key manufacturing process that transforms a raw, flat sheet into a product without removing material, unlike machining. The core of this technique lies in a variety of methods, including cutting, bending, and assembling, all performed on metal sheets that are typically 0.006 to 0.25 inches thick. This versatile process is a cornerstone of industries ranging from automotive and aerospace to electronics and construction.
Common Materials for Sheet Metal Fabrication
Selecting the right material is vital, as it depends on the product’s function and cost. Here are some of the most common materials used:
Cold rolled Steel (SPCC): This is a raw steel sheet rolled to a specific thickness. Without any protective coating, it oxidizes very easily, especially in humid environments, so it must be painted or plated before use.
Hot-rolled Steel (SHCC): Formed at high temperatures, this material has a surface layer of carbon that often requires removal before further processing or finishing.
Electro-galvanized Steel (SECC): An SPCC base sheet that has been electroplated with a zinc layer. It retains the mechanical properties and workability of SPCC while gaining excellent corrosion resistance and a decorative finish. It's widely used for computer cases and home appliances.
Hot-dipped Galvanized Steel (SGCC): This material is created by dipping hot or cold-rolled steel into a molten zinc bath. SGCC is harder than SECC, has less ductility, a thicker zinc layer, and better corrosion resistance, making it suitable for industrial equipment and construction with demanding weather resistance requirements.
SUS304: One of the most common types of stainless steel. With its high nickel content, it offers excellent corrosion and heat resistance and strong mechanical properties, but it has no elasticity and cannot be hardened by heat treatment.
SUS301: Lower in chromium than SUS304, it has less corrosion resistance. However, it gains excellent tensile strength and hardness through cold working, making it ideal for springs and EMI shields.
Copper: Including brass, red copper, and beryllium copper, chosen based on specific application needs.
Aluminum: Common grades include 6061, 5052, 1010, and 1060. They are prized for being lightweight, strong, and easy to machine, making them a popular choice for various products.
Key Fabrication Processes
Sheet metal fabrication is a complex, multi-stage process that includes several key techniques:
1. Cutting and Blanking
Laser cutting: Uses a focused laser beam to melt a localized area of the metal. A gas (like oxygen or nitrogen) then blows away the molten material. This technology is highly precise and fast, capable of cutting a wide range of metals.
Plasma cutting: A thermal cutting process that uses an ionized gas called plasma. While it provides a fast cut for conductive metals, it creates a large heat-affected zone, which can result in burrs and oxidation.
Waterjet cutting: This process uses a high-pressure stream of water mixed with an abrasive to cut metal. It's a "cold" cutting method, so it produces no thermal distortion. It can cut nearly any material with high precision and a smooth finish, often eliminating the need for secondary processing. It’s an excellent alternative to laser cutting, especially for heat-sensitive materials.
2. Forming
Sheet metal bending: A cost-effective process for
small-batch prototyping. A press brake applies force to the sheet to deform and bend it to the desired angle.
Rolling: A universal process that uses three rollers to continuously bend a metal sheet into shapes like cylinders or cones.
3. Welding
Welding is crucial for joining sheet metal parts. The main types include:
MIG welding (Metal Inert Gas): Uses a continuous solid wire electrode and a shielding gas to prevent atmospheric contamination. It is highly cost-effective and widely used in the automotive and home goods industries.
TIG welding (Tungsten Inert Gas): Uses a non-consumable tungsten electrode and an inert gas (argon or helium). It is ideal for non-ferrous metals like aluminum and titanium and is frequently used in the aerospace industry for high-quality, precise welds.
Plasma arc welding: Similar to TIG welding but uses a more focused plasma stream, offering higher speed and precision. It is common in the aviation and marine industries.
Laser/Electron beam welding: These high-energy beam processes offer extreme precision for complex tasks. They are suitable for various materials and produce clean, aesthetically pleasing welds that often require less post-processing.
Post-Processing & Finishing
Finishing is an essential step to enhance the part's appearance and functionality:
Brushing (Hairline Finish): Uses an abrasive belt to create fine, uniform lines on the metal surface. It is primarily used for aesthetics, especially on aluminum.
Sand blasting: High-speed abrasive particles are blasted onto the surface to create a matte texture. This removes surface dirt and increases adhesion, preparing the part for subsequent coatings.
Paint & powder coating: A layer of paint is applied and then cured in a high-temperature oven. This process beautifies the part and adds corrosion resistance. Powder coating is the most common method and does not conduct electricity.
Plating: A layer of another metal (like zinc, nickel, or chrome) is applied via an electrochemical reaction to improve corrosion resistance and appearance.
Anodizing: An electrochemical process primarily for aluminum that creates a dense, protective oxide layer on the surface. This layer significantly increases corrosion resistance and can be dyed to add color.
