C21 · Rectangular funnel · centered or offset

Measure the two openings

Upper length and width describe the rectangular opening at the top of the transition. Lower length and width describe the actual lower opening; use clear, consistent reference faces. Height is the perpendicular distance between the opening planes, not a slant length. Both openings are parallel and their edges are aligned with the same X/Z axes.

Offsets move the upper opening center relative to the lower opening: positive X follows the opening length; positive Z follows its width. Zero offsets give a centered transition. Offset panels generally have different side-edge lengths; read each panel separately.

How the flat patterns are calculated

For a centered shape, dx = (upper length − lower length) / 2 and dz = (upper width − lower width) / 2. True face heights are √(H² + dz²) for the length-edge panels and √(H² + dx²) for the width-edge panels. A corner edge is √(H² + dx² + dz²). With offsets, each panel uses its own perpendicular setback and along-edge shift.

Each four-corner panel is unfolded by an isometry: all four edges and both diagonals match the 3D panel. The assembly animation rotates each panel rigidly about a reference edge. It does not interpolate or stretch the sheet.

Default example

800 × 600 mm → 400 × 300 mm · H 500 mm True face height: 514.20 mm / 559.02 mm / 531.41 mm / 522.02 mm.

Fabrication and assembly method

1. Inspect the four rectangular panel blanks. These are separate panels, not a continuous tray blank.
2. Mark each true trapezoid outline on its blank. Red lines are the panel cut boundaries.
3. Cut the four panels to the marked outlines; the separated panels show their finished boundaries.
4. Assemble the panels about their lower reference edges and join the corner seams. These edges locate assembly; they do not imply a retained material hinge.

Ideal sharp, zero-thickness panel geometry. Panel dimensions exclude kerf, bend allowance, seams, overlap tabs, fasteners and the openings cut in the parent tray. The assembly is a separate-panel method; confirm the actual joining detail.

Independent TrayNeo panel-development method. Reference-product correspondence remains under review.

Geometry references

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