In the field of sheet metal fabrication, one of the biggest challenges for CAD\/CAM design engineers is accurately calculating the dimensions of the flat pattern before feeding it into the bending machine. When bent, the material expands on the outside and compresses on the inside, resulting in a change in finished product dimensions compared to the original workpiece. To solve this problem, a thorough understanding and correct application of the K Factor in sheet metal bending, combined with tolerance standards, is essential.<\/p>\n
In the article below, the Metaltech 1 technical team will share detailed instructions on how to calculate bending blanks and provide the most accurate K-Factor lookup table.<\/p>\n
When a metal sheet is bent, the cross-section of the sheet at the bending point is divided into three different load-bearing zones:<\/span><\/p>\n K-Factor (K-Factor)<\/b> This is the ratio between the distance from the inner surface of the bending angle to the neutral axis (denoted as ). <\/span>t<\/span><\/i>) compared to the total thickness of the metal plate (denoted as <\/span>T<\/span><\/i>).<\/span><\/p>\n Formula: K = t \/ T<\/b><\/p>\n In practice, the K-Factor typically ranges from 0.25 to 0.5. This coefficient is influenced by many factors:<\/span><\/p>\n For convenience in setting parameters in software such as SolidWorks, AutoCAD, or Inventor, engineers can refer to the following table of empirical K-Factor values \u200b\u200b(commonly applied to the air bending method on CNC machines):<\/span><\/p>\n (Note: The table above is for reference only. In actual machining, to achieve absolute accuracy, workshop engineers need to perform test bends to determine the precise K-Factor and Bend Deduction values \u200b\u200bfor each specific batch of material and die system.)<\/span><\/i><\/p>\n Even if you have applied it correctly <\/span>calculate the impact workpiece<\/b>In practice, achieving 100% accuracy is virtually impossible due to measurement equipment errors, material springback, and the thickness tolerance of the steel workpiece itself.<\/span><\/p>\n Therefore, technical drawings must always include requirements regarding... <\/span>bending tolerance<\/b>At machining plants using modern CNC hydraulic bending machines like Metaltech 1, tolerance standards are typically controlled as follows:<\/span><\/p>\n The calculation of the flat pattern becomes meaningless if the initial workpiece cutting process is inaccurate in terms of dimensions. If you use plasma cutting with beveled edges, or stamping with protruding burrs, the CNC bending machine will not be able to accurately press the workpiece onto the die, resulting in incorrect bending angles.<\/span><\/p>\n\n
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2. Reference K-Factor table for common materials<\/b><\/h2>\n
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\n Material Type<\/b><\/td>\n Bending radius (R) and thickness (T) conditions<\/b><\/td>\n K-Factor<\/b><\/td>\n<\/tr>\n \n Mild Steel (SPCC \/ SS400)<\/b><\/td>\n R < 2T<\/span><\/td>\n 0.38 \u2013 0.42<\/span><\/td>\n<\/tr>\n \n <\/td>\n R = 2T to 4T<\/span><\/td>\n 0.43 \u2013 0.46<\/span><\/td>\n<\/tr>\n \n <\/td>\n R > 4T<\/span><\/td>\n 0.50<\/span><\/td>\n<\/tr>\n \n Stainless steel (304\/316)<\/b><\/td>\n R < 2T<\/span><\/td>\n 0.35 \u2013 0.40<\/span><\/td>\n<\/tr>\n \n <\/td>\n R = 2T to 4T<\/span><\/td>\n 0.40 \u2013 0.45<\/span><\/td>\n<\/tr>\n \n <\/td>\n R > 4T<\/span><\/td>\n 0.50<\/span><\/td>\n<\/tr>\n \n Aluminum & Aluminum Alloys<\/b><\/td>\n R < 2T<\/span><\/td>\n 0.40 \u2013 0.44<\/span><\/td>\n<\/tr>\n \n <\/td>\n R = 2T to 4T<\/span><\/td>\n 0.45 \u2013 0.48<\/span><\/td>\n<\/tr>\n \n <\/td>\n R > 4T<\/span><\/td>\n 0.50<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n 3. Standard bending tolerances in mechanical machining.<\/b><\/h2>\n
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4. Why should design engineers collaborate with a closed-loop manufacturing process?<\/b><\/h2>\n