Dimensioning Sheet Metal Bends

Remember if you do outside dimensions the fabricator has to deduct the material thicknesses and bend allowances whereas with inside dimensioning he she merely has to add the bend allowances however if you give an acute bend a dimension to a theoretical intersection of the two outside faces this is easier to inspect by laying two rules on the outside faces this is better than trying to measure the center point of a radius on the inside of the part.

Dimensioning sheet metal bends.

Bends specified as angles may be toleranced at plus or minus one half degree at a location adjacent to the bends. Cells on the right will output the desired values. You only have to insert interior angle flange lengths k factor inside radius and material thickness. Uncontrolled dimensions on the other hand refer to the sections of the part where the bend originated from.

Relief height is generally kept greater than two times of sheet thickness plus bend radius. A 1 degree tolerance on all bend angles. Bend relief is provided at the end of bending edge in sheet metal design to avoid any crack tearing in the corner. 1 all manufacturing tolerances used up to that point such as laser cutting tolerances welding tolerances and more 2 all bend tolerances for the entire part added together we call this an uncontrolled dimensions because there are additional tolerances to consider.

Uncontrolled dimensions contain two different categories of tolerances. In low carbon steel sheet metal the minimum radius of a bend should be one half the material thickness or 0 80 mm 0 03 inch whichever is larger. Use the minimum bend dimension values in the charts below for your minimum closeness of cutout to a bend. Avoid large sheet metal parts with small bent flanges.

This is a common occurrence when manufacturers receive a sheet metal layout dimensioned in the flat pattern. Form height to thickness ratio to determine the minimum form height for sheet metal use the following formula. Geometry of tooling imposes a minimum bend dimension. D 2 5t r see below the height can be less but it required secondary operations and is far more costly.

When you figure flat pattern length you simple add up all the outside flanges and subtract the bend deductions. As one who daily works with sheet metal design and fabrication use outside flange lengths for several reasons. Bends in sheet metal are manufactured using sheet metal brakes. Sheet metal parts with a minimum of 0 9mm to 20mm in thickness can be manufactured.

With this free online tool we quickly get the sheet metal bend deduction and therefore the sheet metal blank initial flat length from the finished part measurements. No worries of forgetting a material thickness along the way 3. When designing parts for laser cutting one should not make holes smaller than the thickness of the material. The diagram shows one such mechanism.

Refer to the chart for values for folder as well as various press brake tooling combinations. 5 edge distortion an exaggerated example of edge deformation is pictured in figure a below.