Operational reference for Shell Rolling Master.
Calculate the flat plate blank required to roll an open-seam cylindrical or conical shell, accounting for:
- Outer (OD) or inner (ID) diameter specification
- Plate thickness and K-factor (neutral-axis position)
- Welding / seam gap
- Optional bend / roll guide lines
Inspect results as a 3D solid or 2D pattern, then export PDF, DXF, or STEP.
| Region | Role |
|---|---|
| Left sidebar | Mode, dimensions, K-factor, gap, bend lines, results, export actions |
| Main viewport | Toggle between 3D Model and 2D Pattern |
On narrow screens the sidebar stacks above the viewport.
- Select Cylinder or Cone.
- Choose OD or ID as the diameter basis.
- Enter dimensions (all values in millimetres):
- D1 — primary / top diameter
- D2 — bottom diameter (cone only)
- H — axial height (also the blank width for cylinders)
- Thickness — plate thickness
- K-factor — neutral fibre position in the thickness (typical steel ~0.3–0.5)
- Gap — open seam / weld gap along the developed length
- Optionally enable bend lines and set the count of guide lines. With bend lines on, Dimension bend-line spacing adds an aligned dimension run between the guides — on one edge for a cylinder blank (both edges are parallel, so the numbers would repeat) and on both edges for a cone, where the two arcs have different chord lengths. Dimension offset controls how far the dimension lines sit outside the blank.
- Review the results card (required sheet size; for cones also sector angle and radii).
- Switch view modes as needed; export PDF / DXF / STEP when ready.
Every input change recalculates immediately. Invalid combinations show an error instead of numeric results.
| Field | Unit | Constraints | Notes |
|---|---|---|---|
| Mode | — | cylinder | cone |
Switches development algorithm |
| Spec type | — | OD | ID |
Which surface the diameters describe |
| D1 | mm | Finite, > 0 | Top / main diameter |
| D2 | mm | Finite, > 0 (cone) | Bottom diameter; ignored for cylinder |
| H | mm | Finite, > 0 | Shell height / cylinder blank width |
| Thickness | mm | Finite, > 0; must be < neutral radius | Plate thickness |
| K-factor | — | > 0 and ≤ 1 | Neutral-axis fraction through thickness |
| Gap | mm | Finite, ≥ 0 | Deducted from developed blank length / sector |
| Bend lines | — | Optional; count ≥ 1 when enabled | Equally spaced roll guides |
| Dimension bend-line spacing | — | Requires bend lines | Spacing between guides plus both seam edges |
| Dimension offset | mm | > 0 | Distance from the edge to the dimension line |
Cylinder · OD · D1 = 2000 · D2 = 1500 · H = 2500 · T = 15 · K = 0.44 · Gap = 2 mm.
| Output | Meaning |
|---|---|
| Neutral diameters | Diameters at the bending neutral fibre |
| Required sheet size | Axis-aligned blank envelope used for nesting / stock |
| Flat length / width | Developed blank extents (see calculations for cone bounding-box logic) |
| Output | Meaning |
|---|---|
| Sector angle | Development angle after gap deduction (degrees) |
| Outer / inner pattern radii | Annular-sector radii on the flat pattern |
| Pattern rotation | Orientation chosen to minimise bounding-box area (landscape-biased) |
Cone reported sheet dimensions include a 10 mm cutting margin on the bounding box. The DXF outline itself does not add that margin.
- Thick open-seam shell derived from neutral geometry and thickness / K-factor offsets
- Orbit / pan / zoom; auto-fit camera; grid and edge overlays
- Orientation cube for face / edge / corner viewpoints
- Cylinder: dimensioned rectangle
- Cone: dimensioned annular sector with dashed bounding rectangle
- Bend lines drawn when enabled, with their spacing dimensions when that option is on
| Format | Typical use |
|---|---|
| Shop fabrication report (inputs, neutrals, cutting data, pattern sketch) | |
| DXF | CNC / CAD blank outline (+ optional bend and dimension layers) |
| STEP | Thick open-seam solid for CAD (browser OpenCascade WASM) |
Filenames:
- PDF:
shell-pattern-{mode}.pdf - DXF:
shell-pattern-{mode}.dxf - STEP:
shell-rolling-{mode}_D…_H…_T….step
See export-formats.md for entity-level detail.
| Condition | Effect |
|---|---|
| Non-positive dimensions or invalid K-factor | Calculation marked invalid |
| Gap negative or non-finite | Invalid welding gap |
| Thickness ≥ neutral radius | Physically impossible shell |
| Cylinder gap ≥ neutral circumference | Gap too large |
| Cone | D1ₙ − D2ₙ |
| Cone gap yields non-positive sector angle | Gap too large for geometry |
| Cone angle > 360° | Allowed with console warning (overlapping pattern) |
- Prefer K-factor values from your shop / material standards; 0.44 is a reasonable steel default, not a universal constant.
- Specify diameters consistently as OD or ID for the finished shell after rolling.
- Use gap for the intended weld root opening or fit-up clearance on the developed length.
- For near-equal cone ends, switch to cylinder mode rather than forcing a tiny frustum.
- STEP export may take several seconds on first use while the CAD kernel loads.