Even the smallest of drawing errors can cause major problems when a project is in full flow in the workshop.
Bend Radii Too Tight for the Material
The smallest error on a drawing can lead to serious problems when your work reaches the workshop. These problems are mainly caused by bend radii that are too tight for the material. The internal bend radius should be at least equal to the sheet thickness. Bending with too small a radius can lead to cracking in the part.
Holes Placed Too Close to Bend Lines
Most significant damage will be to holes near to bend lines of up to 1.5 times material thickness. These need to be moved to further parts of the drawing or in some instances drilled after the part has been formed to the required shape.
Ignoring Grain Direction
Forming the sheet metal against the grain can cause cracking, especially in harder grade metals. Noting the required grain direction on the drawing for such parts will ensure the sheet metal is formed correctly.
Vague or Mismatched Tolerances
Tolerances that are too tight and even contradict each other on a drawing are the main reason for delays. Only apply very tight tolerances where there is a real functional reason for them. On the rest of the drawing, apply the same tolerances. There is more on Sheet Metal Fabrication at dkmsheetmetal.co.uk.
Missing Flat-Pattern Information
Make sure that the CAD file includes an unfolded view or a flat-pattern for the required work. For the K-factor or bend allowance, specify the required values on the drawing so that there is no confusion or need for additional inquiry.
Use these 5 drawing issues to catch major design drawing errors before they cause costly delays in your fabrication project.