Eccentric Rectangular Funnel with a 100 mm Lower Offset

Define the opening centers and setbacks

The upper opening is 800 by 600 mm and the lower opening is 400 by 300 mm, separated by 500 mm vertically. The lower center moves 100 mm in positive X relative to the upper center. Its Z offset is zero. Identify this direction using the opening centers before laying out the individual panels.

The tool accepts the lower opening offset relative to the upper opening. Follow those named references when entering positive or negative values. The drawing can position the lower opening at its local origin while representing the same relative displacement by moving the upper opening in the opposite direction.

The half differences of opening sizes are 200 mm along X and 150 mm along Z. The 100 mm lower offset changes the two X-side setbacks to 200 − 100 = 100 mm and 200 + 100 = 300 mm. The Z-side setbacks remain 150 mm.

Calculate each face and corner

For each panel use the vertical height and the setback perpendicular to that panel. The two faces parallel to X have slant heights √(500² + 150²) = 522.02 mm. The other two faces have slant heights √(500² + 100²) = 509.90 mm and √(500² + 300²) = 583.10 mm.

The true corner lines combine both horizontal movements with the vertical rise. At one X side the corner length is √(500² + 300² + 150²) = 602.08 mm. At the other it is √(500² + 100² + 150²) = 531.51 mm. Each occurs at two corners because the Z offset is zero.

Each long face connects an 800 mm edge to a 400 mm edge. Its area is 600 times its slant height. Each short face connects 600 to 300 mm and has area 450 times its own slant height. The sum is 1118267.10 mm². Keep each face associated with its own perpendicular setback and corner pair.

Worked example dimensions

Lay out and identify all four panels

Draw panel 1 with lower edge from 0 to 400 mm. Its upper edge runs from −300 to 500 mm at height 522.02 mm. Panel 3 uses an upper edge from −100 to 700 mm above the same lower-edge coordinates. These two developed long panels have opposite sideways shifts.

Panels 2 and 4 each have a 300 mm lower edge and a 600 mm upper edge centered above it. Their perpendicular face heights differ, at 509.90 and 583.10 mm. Label all four panel numbers before separating the pieces so the short face on each side joins the correct long-panel corner.

Use Original, Mark, Cut and Form to inspect the finished outlines and assembly. The model preserves the true panel edges while placing the four faces around their opening boundaries. Rotate the completed funnel and follow the displaced lower center through all seams. Check material and joining allowances before workshop cutting.

Review the fabrication detail

This layout develops ideal separate panels. Add the selected seam details and material allowances after reviewing the actual fabrication method.