Input geometry
Triangulation development
Rectangle / Square-to-Round Transition Development
Use one combined tool for rectangular or square openings. Equal bottom width and depth are automatically treated as square-to-round.
Transition dimensions
All dimensions are in millimetres. Offsets are measured from the rectangle centre; positive X moves right and positive Y moves toward the back.
Flat pattern
Complete developed panel
All four sides are joined. The two outside edges form the single closing seam.
True-length table
Point numbers correspond to each quarter of the round edge.
| Side | Round point | Lower corner | True length |
|---|
Calculation basis and limits
The entered duct dimensions are inside sizes. Development is calculated at the centre of the plate thickness: centre-surface diameter = inside diameter + thickness, and centre-surface rectangular width/depth = corresponding inside size + thickness. The four sides are unfolded around their shared corner generators to produce one continuous plate with a single closing seam.
- The round opening may extend beyond the rectangular or square opening in plan because of its diameter or X/Y offset; the resulting eccentric transition is developed from the entered geometry.
- Plate thickness is included only for locating the development surface. Seam, flange, kerf, weld-shrinkage and trimming allowances are not yet added.
- Verify dimensions, allowances, material orientation and fit-up before cutting plate.