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How can I add seam allowances in duct designs without collisions?
william_brooks158
Member Posts: 6 ✭
I am designing a bunch of ductwork parts for 24ga sheet metal for hand assembly (not welded), and I can't figure out how to add seam allowances for something like a Pittsburgh seam. In a flat layout, I'd just add 1" on one side of the rip joint for the pitt and 1/4" on the other side of the rip for the flange. But when the duct is designed in 3D, I can't add these allowances because it will cause collisions.
For example, in this model, the seam highlighted in yellow is a rip. They are free ends when flattened and will be joined after folding. I need to add 1/4" 90 deg. flange on one vertex and a 1" allowance for the pittsburgh on the mating vertex. Similar for the slip & drive seam between the light blue lofted taper and the dark blue enclosure faces.
Any suggestions?

Answers
Add the allowance as flanges in the 3d but position them so they don't collide with the neighbor by aligning them to the inside face or outside face of the cube.
Derek Van Allen | Engineering Consultant | Meddler