Uncontrolled dimensions contain two different categories of tolerances.
Dimensioning sheet metal bends.
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.
Bends in sheet metal are manufactured using sheet metal brakes.
Bend relief is provided at the end of bending edge in sheet metal design to avoid any crack tearing in the corner.
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.
Extrude hole size position guidelines creating an extruded hole using a punching process requires extreme pressure force.
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.
Form height to thickness ratio to determine the minimum form height for sheet metal use the following formula.
Avoid large sheet metal parts with small bent flanges.
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 designing parts for laser cutting one should not make holes smaller than the thickness of the material.
Uncontrolled dimensions on the other hand refer to the sections of the part where the bend originated from.
5 edge distortion an exaggerated example of edge deformation is pictured in figure a below.
No worries of forgetting a material thickness along the way 3.
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.
When you figure flat pattern length you simple add up all the outside flanges and subtract the bend deductions.
All of those tolerances are added together.
This is a common occurrence when manufacturers receive a sheet metal layout dimensioned in the flat pattern.
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.
As one who daily works with sheet metal design and fabrication use outside flange lengths for several reasons.
The diagram shows one such mechanism.
A 1 degree tolerance on all bend angles.
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.
Refer to the chart for values for folder as well as various press brake tooling combinations.
