With flexibility in shapes and lightweight, sheet metal embraces wide applications in various industries. The process of fabricating sheet metal involves an array of techniques. This guide helps you understand sheet metals and the techniques of fabricating them.
Understanding Sheet Metal
A sheet of metal is a thin metal with a maximum thickness of 6mm. The commonly used sheet metal materials are stainless steel, galvanized steel, aluminum, brass, copper, etc. Sheet metal offers two major benefits:
Capability for processing complex shapes: Sheet metal fabrication can create intricate shapes and structures, such as curved surfaces, arcs, and indentations, with high precision to meet both aesthetic and functional requirements.
Lightweight design: Sheet metal manufacture allows lightweight component design through structural optimization and material selection, reducing weight while enhancing strength and performance. It is particularly beneficial in industries like automotive and aerospace, where it can lead to reduced energy consumption and improved efficiency.
Tools and Equipment for Sheet Metal Fabrication
The four most important steps in sheet metal fabrication are cutting, punching/shearing, bending/rolling, welding, and surface treatment. Essential tools for these processes include:
Cutting: Guillotine shear or shearing machine
Punching/Shearing: Numerical control machine (NC) or standard punch press
Laser Cutting: Laser cutting equipment
Forming: Bending machine, punch press
Welding: Spot welding machine, and more
Surface Treatment: Deburring machine, and others
Depending on the specific requirements, each step can be finished using a different technique.
Cutting Techniques for Sheet Metal
Cutting shapes metal sheets into required shapes and dimensions according to design specifications. Typical methods include shearing, laser cutting, and plasma cutting.
Shearing: Shearing is typically done by applying a strong force to a metal workpiece, causing it to separate along a line. It is suitable for cutting straight lines on flat metal stock and can handle various materials and thicknesses. Though shearing is generally faster than some other cutting methods, it is not ideal for intricate or curved cuts. Also, shearing may result in edge distortion and can produce burrs on the cut edge that require additional processing.
Laser cutting: The laser cutting machine utilizes a powerful laser enhanced by lenses or mirrors. It is a precise and energy-efficient way suitable for thin or medium-sized metal sheets but may struggle to penetrate the hardest materials.
Plasma cutting: The plasma cutting machine creates an ionized gas electrical channel, forming a hot plasma jet that can easily penetrate thick metal sheets. While not as precise as laser cutting machines, plasma cutting offers fast speed, powerful functionality, and lower setup costs.
Different sheet metal cutting techniques are suitable for different occasions and materials. Choosing the appropriate cutting method can improve processing efficiency and product quality while reducing costs and waste. Therefore, when manufacturing sheet metal, it is necessary to select the most suitable cutting method based on specific circumstances, and strictly adhere to safety operating procedures to ensure the safety of personnel and equipment.
Bending and Forming Sheet Metal
Forming is the process of fabricating sheet metals into specific forms, such as casings and housings, through methods like punching and bending. Bending, on the other hand, involves shaping metal sheets into desired angles and forms, commonly achieved through mechanical or hydraulic bending methods.
To select a bending method, the following factors need to be considered:
Firstly, it is necessary to analyze the structure of the part, including the material's thickness, hardness, dimensions, etc. These factors will all affect the bending process and the equipment required. For instance, thicker materials require a bending machine with a higher tonnage to overcome greater bending resistance.
The choice of material for the product also significantly impacts the effectiveness of the bending process. Generally, selecting materials with good bending performance, such as aluminum alloy, low carbon steel, etc., can facilitate the bending process. Additionally, it is important to consider the product's usage environment and functional requirements when choosing the appropriate material to meet these criteria.
Finally, it is essential to consider the intended application of the product. For instance, products designed for confined spaces require a compact bending machine to ensure operational convenience. Also, factors such as production cycle and manufacturing costs should be considered when choosing the appropriate bending processing.
After choosing the right bending method, to ensure achieving accurate bends and complex shapes, it is necessary to select suitable materials based on product requirements and production processes to avoid bending errors due to material issues. Choosing the appropriate pressure based on material thickness and product requirements helps avoid bending errors caused by insufficient or excessive pressure.
Joining Methods for Sheet Metal
The typical techniques for joining sheet metal parts together are welding, riveting, bolting, and snap-fitting.
Welding: Welding connects sheet metal components by melting them together through high-temperature heating, suitable for applications requiring high joint strength in structures such as mechanical equipment, bridges, and pressure vessels. Proper selection of welding processes, equipment, and control of welding parameters are crucial for quality welds.
Riveting: Riveted connection involves using riveting machines to connect rivets through sheet metal components, commonly used for sealing applications in industrial manufacturing. Selecting appropriate rivet specifications, riveting pressure, and ensuring precise component positioning and hole processing are essential for alignment and joint strength.
Bolting: Bolted connection is a common sheet metal joining method, using bolts to connect components. It is suitable for applications requiring component replacement or disassembly and provides high joint strength. Proper material and thread selection and adherence to specified torque standards during tightening are crucial for reliability.
Snap-fitting: Snap-fit connection joins sheet metal components using the shape of slots without additional connecting parts. It is a simple and quick method suitable for connecting small components. Material accuracy, slot design, and consideration of the lower strength of snap-fit connections are vital factors to note.
Finishing and Surface Treatment
After completing processes such as bending and riveting, the final step is surface treatment. The surface treatment of sheet metal parts is also a crucial part of the sheet metal processing process, as it prevents part rust and improves the appearance of the sheet metal part. Due to the lack of rust and corrosion resistance in the surfaces of certain sheet metal materials, effective surface treatment is essential. Surface treatment can also enhance the product's lifespan in harsh environments or achieve specific surface effects or functions.
The available finishing techniques for manufacturing sheet metal are deburring, sanding, bead blasting, brushing, powder coating, electroplating, anodizing, phosphating, etc.
Deburring is the process of removing burrs, which are unwanted rough edges or protrusions on the sheet metal after it has been fabricated. It is typically applied to improve the part's safety, functionality, and appearance.
Sanding smooths or polishes a surface using abrasive materials such as sandpaper. It is used to remove rough spots, scratches, or imperfections from the surface of sheet metal, resulting in a smoother and more uniform finish.
The purpose of bead blasting is to remove dirt and increase the adhesion of the sheet metal surface, preparing it for subsequent surface treatment methods.
Brushing creates a consistent directional pattern or texture on the surface of the sheet metal to achieve an aesthetic purpose.
Powder coatings in different colors improve the appearance and corrosion resistance of the sheet metal.
A layer of another metal created through chemical reactions is applied to the material surface to enhance its corrosion resistance and achieve aesthetic improvement. Electroplating includes processes like chrome plating, galvanizing, and nickel plating.
Anodizing is an electrochemical process that increases the thickness of the natural oxide layer on the surface of metal parts. This process enhances corrosion resistance and allows for the application of various decorative finishes.
The purpose of phosphating is to prevent corrosion of the sheet metal. It is used for painting before priming to improve the adhesion of the paint film layer and corrosion resistance. In the metal cold working process, phosphating plays the role of friction reduction lubrication.
Different types of sheet metal require varied surface treatments:
Stainless steel sheets: brushing, powder coating, etc.
Cold-rolled sheets: electroplating, phosphating, powder coating, etc.
Aluminum sheets: brushing, anodizing (usually in black or natural color), powder coating.