Dimensioning Sheet Metal Bends

Geometry of tooling imposes a minimum bend dimension.

Dimensioning sheet metal bends. Cells on the right will output the desired values. All of those tolerances are added together. Use the minimum bend dimension values in the charts below for your minimum closeness of cutout to a bend. Relief height is generally kept greater than two times of sheet thickness plus bend radius.

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. 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. Uncontrolled dimensions on the other hand refer to the sections of the part where the bend originated from. Refer to the chart for values for folder as well as various press brake tooling combinations.

The diagram shows one such mechanism. As one who daily works with sheet metal design and fabrication use outside flange lengths for several reasons. No worries of forgetting a material thickness along the way 3. Sheet metal parts with a minimum of 0 9mm to 20mm in thickness can be manufactured.

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

A 1 degree tolerance on all bend angles. Bends specified as angles may be toleranced at plus or minus one half degree at a location adjacent to the bends. Bends in sheet metal are manufactured using sheet metal brakes. Extrude hole size position guidelines creating an extruded hole using a punching process requires extreme pressure force.

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. When you figure flat pattern length you simple add up all the outside flanges and subtract the bend deductions. This is a common occurrence when manufacturers receive a sheet metal layout dimensioned in the flat pattern. Avoid large sheet metal parts with small bent flanges.

When designing parts for laser cutting one should not make holes smaller than the thickness of the material. You only have to insert interior angle flange lengths k factor inside radius and material thickness.