Forming is the process of achieving part shape by applying external forces to a metal material. This chapter covered different types of forming processes that can be used for bulk metal materials or sheet metal stock. Some of these processes are rolling, drawing, forging and extrusion. Each of these processes has its own advantages and limitations, and requires careful consideration of design for manufacturing (DFM) guidelines to ensure quality, efficiency and cost-effectiveness.

Design for Forming by Rolling and Drawing

• Choose a suitable material that can withstand the high compressive stresses and strains involved in these processes.
• Minimize the number of rolling or drawing passes to reduce the amount of material waste and energy consumption.
• Avoid sharp corners, abrupt changes in cross-section or complex shapes that can cause defects such as cracks, tears or wrinkles.
• Provide adequate lubrication and cooling to reduce friction, heat generation and tool wear.
• Control the rolling or drawing speed, temperature and pressure to achieve the desired dimensions, tolerances and surface finish.

For more information, see: Rolling and Drawing Manufacturing.

Design for Forming by Forging

• Choose a suitable material that has good ductility, strength and resistance to deformation at high temperatures.
• Design the part with uniform cross-sections, smooth transitions and generous fillets to avoid stress concentrations and cracking.
• Minimize the number of forging operations and use preforms or intermediate shapes to reduce the amount of material deformation and heating required.
• Provide sufficient draft angles, clearances and allowances to facilitate the removal of the part from the die and account for shrinkage and distortion.
• Use appropriate heating, cooling and quenching methods to control the microstructure, mechanical properties and residual stresses of the forged part.

For more information, see: Forging.

Design for Forming by Extrusion

• Choose a suitable material that has good extrudability, meaning it can flow easily through the die without cracking or breaking.
• Design the part with constant cross-sections, symmetrical shapes and balanced wall thicknesses to ensure uniform material flow and extrusion pressure.
• Avoid features that can cause die wear, such as sharp edges, deep grooves or small holes.
• Provide adequate lubrication and cooling to reduce friction, heat generation and tool wear.
• Control the extrusion speed, temperature and pressure to achieve the desired dimensions, tolerances and surface finish.

For more information, see: Extrusion.

Design for Forming with Sheet Metal

• Choose a suitable material that has good formability, meaning it can bend, stretch or shear without cracking or breaking.
• Design the part with simple shapes, large radii and gentle curves to avoid excessive deformation and springback.
• Minimize the number of bends, cuts or holes to reduce the amount of material waste and processing time.
• Provide adequate bend allowances, clearances and margins to account for the material thickness, bend radius and tooling dimensions.
• Use appropriate methods for joining, fastening or finishing the sheet metal part, such as welding, riveting or painting.

For more information, see: Sheet Metal Forming.

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