No matter the situation, it’s difficult to watch your hard work go to waste. 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. To avoid wasting time on incorrect measurements, always dimension to the formed view, and here’s why:
Bending Factors Affect the Flat Pattern
Dimensions given on a flat pattern are affected by several bending factors, like k-factor and bend radius, during the 3D modeling stage. The flat pattern drawing doesn’t always list these factors. However to match the other dimensions that are included, it would require your manufacturer to work with incorrect or unachievable sheet metal forming factors. This makes matching these dimensions during the modeling stage difficult and time-consuming.
Fabricator Tooling and Equipment Limitations
Your manufacturer may not be able to match dimensions when creating the actual sheet metal part due to tooling and equipment limitations. Since each metal fabricator has its own tooling, bend factors, and equipment to develop the flat blank, it is better to fully dimension to formed views for that manufacturer. This allows your fabricator to develop their flat blank to meet your finished part dimensional requirements.
Bend Angles Influence the Overall Flat Length of the Part
As you can see in the example below, the 1st 45o bend from the origin varies by only .004.” However, once you expand over all four bends that number increases to a difference of .130” on the overall flat length of the part. The variation becomes larger as the bend angle increases, and the part will no longer pass inspection.
These factors all play a role in why most manufacturers don’t want you to dimension parts in the flat pattern. They want to save your project time in unnecessary backtracking. All your manufacturer needs is the formed view with the required dimensions, they’ll determine the bend factors from that point on.
If you have any questions about dimensioning, or if you would like to start your own industrial project, please contact us today.