Dimensioning Sheet Metal Bends

Extrude hole size position guidelines creating an extruded hole using a punching process requires extreme pressure force.

Dimensioning sheet metal bends. 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. Bends specified as angles may be toleranced at plus or minus one half degree at a location adjacent to the bends. Uncontrolled dimensions on the other hand refer to the sections of the part where the bend originated from. This is a common occurrence when manufacturers receive a sheet metal layout dimensioned in the flat pattern.

Uncontrolled dimensions contain two different categories of tolerances. When you figure flat pattern length you simple add up all the outside flanges and subtract the bend deductions. 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. As one who daily works with sheet metal design and fabrication use outside flange lengths for several reasons.

5 edge distortion an exaggerated example of edge deformation is pictured in figure a below. Form height to thickness ratio to determine the minimum form height for sheet metal use the following formula. 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. Bends in sheet metal are manufactured using sheet metal brakes.

Refer to the chart for values for folder as well as various press brake tooling combinations. Use the minimum bend dimension values in the charts below for your minimum closeness of cutout to a bend. No worries of forgetting a material thickness along the way 3. The diagram shows one such mechanism.

All of those tolerances are added together. A 1 degree tolerance on all bend angles. When designing parts for laser cutting one should not make holes smaller than the thickness of the material. D 2 5t r see below the height can be less but it required secondary operations and is far more costly.

Sheet metal parts with a minimum of 0 9mm to 20mm in thickness can be manufactured. Geometry of tooling imposes a minimum bend dimension. You only have to insert interior angle flange lengths k factor inside radius and material thickness. Cells on the right will output the desired values.

These dimensions may seem helpful but after your manufacturer makes bend deductions based on their capabilities and other bending factors your dimensions will become unusable. Relief height is generally kept greater than two times of sheet thickness plus bend radius.