Gutter Mitre: flat pattern
A box or half-round gutter cut on a mitre for an outside or an inside corner: the blank with its folds and the mitred end. A length of box or half-round gutter cut on a mitre at one end, for an outside or an inside corner: the blank with its fold lines and the mitred end.
Open the gutter mitre in SheetMorphConfigurations
- Box gutter, outside corner. A folded gutter with a flat sole; the front is the longer side, as where a gutter turns round the corner of a building.
- Box gutter, inside corner. A folded gutter with a flat sole; the back is the longer side, as in an internal angle or a valley.
- Half-round, outside corner. A half-round gutter; the front lip is the longer.
- Half-round, inside corner. A half-round gutter; the back lip is the longer.
A worked example
The box gutter, outside corner configuration with the sizes SheetMorph opens with, in mm. One blank: the back, the sole and the front, with 2 folds: 1 part, 1 seam.
| Blank, the rectangle the plate is cut from | 362.0 mm × 751.0 mm |
| Length of cut, every outline and hole | 2137.5 mm |
| Bends (2) down, the pattern drawn outside face up | 90.0° |
| Width of the sole | 151.00 mm |
| Height of the back | 120.50 mm |
| Height of the front | 90.50 mm |
| Girth of the profile | 362.00 mm |
| Length along the back | 600.00 mm |
| Length along the front | 751.00 mm |
| Folds | 2 |
| Mitre angle, from square | 45.00 ° |
| Angle the gutter turns through | 90.00 ° |
| Cut across the sole | 213.55 mm |
| P1 Gutter, long | 362.00 mm |
| P1 Gutter, wide | 751.00 mm |
| Plates | 1 |
| Triangular facets | 6 |
| Pattern extent X | 362.00 mm |
| Pattern extent Y | 751.00 mm |
| Developed area | 242,266 mm² |
| Total cut length | 2137.55 mm |
| Longitudinal seam length | 0.00 mm |
How it is developed
True-shape development of flat faces. This is an exact development: the surface unfolds without stretching, so the pattern closes exactly.
- Every face is flat, so the blank is exact. The back and the front are cut square, and the sole on the slant between them.
- On an outside corner the front is the longer side. The second piece of the corner is the same pattern turned over.
- The mitre is a butt joint between the two pieces. Add a lap under Fabrication if it is to be soldered or riveted.
Checked before it can be exported
Every pattern SheetMorph draws is checked against the 3D part it comes from. For this example:
- Surface connectivity (passed): 6 facets form one open sheet: every edge inside a part joins exactly two facets, every open edge one (V - E + F = 1).
- Developed edges equal true 3D lengths (passed): 18 facet edges compared between the 3D surface and the flat pattern (max deviation 2.84e-14).
- Shared edges and seam closure (passed): 5 internal edges are shared vertex-for-vertex between adjacent facets; 0 seam(s) have mating edges of equal true length (max deviation 0).
- Developed facets consistently oriented (passed): All developed facets are counter-clockwise (outside face up); none is mirrored or degenerate.
- Developed area equals surface area (passed): Facet area in 3D and in the flat pattern agree (difference 0).
- Cut outlines closed and non-overlapping (passed): 1 closed outline(s); no outline crosses itself or another outline.
Assumptions
- The pattern is developed on the mid-thickness surface; inside or outside sizes are converted to it by the thickness.
- Curves are chains of chords between division points.
- No seam, lap, weld-preparation or pressing allowance is added.
Limits of this module
- The profile is a plain box section or a plain half round: beads, hems, ogee and moulded fronts are not modelled.
- The mitre is cut square to the sole, for a corner in a level gutter; a mitre that also changes the fall is not modelled.
- No lap or soldering allowance is added at the mitre. Add a seam allowance under Fabrication.
- Folds are sharp lines on the mid-thickness surface. Use the bend deduction under Fabrication for the press brake.
- Curves are chains of straight chords between division points.
- No seam, lap, weld-preparation or pressing allowance is added, and plates are not nested onto stock sheets.
Conventions
Coordinate system. The part stands on the Z axis with End A at Z = 0. Angles round the axis are measured from +X toward +Y, counter-clockwise seen from +Z.
Divisions and thickness. A circle is divided into 4N equal chords. Sizes are inside, mid-thickness or outside sizes; the pattern is developed on the mid-thickness surface and the views show the sizes as entered.
Gutter. The gutter stands on end along the Z axis, its square end, End A, at Z = 0 and its mitre, End B, at the top. The back is on the -X side and the front on the +X side; the sole, or the bottom of a half-round gutter, is at Y = 0 and the lips are toward +Y. The length is measured along the back.
Mitre. The mitre is a flat cut square to the sole, turned from square by the mitre angle: half the angle the gutter turns through, so 45 degrees for a square corner. On an outside corner the front is longer than the back; on an inside corner it is shorter. Two pieces of opposite hand make the corner: turn the pattern over for the second.
Blank. The blank is one plate, drawn outside face up, as wide as the girth of the profile. A box gutter has two folds, at the heel and the toe of the sole; a half-round gutter is rolled.
Change the sizes to your own in SheetMorph, check the drawing, add seam and flange allowances, and export DXF, PDF, SVG, CSV or G-code. Check every pattern against your own standards before cutting.
Open the gutter mitreOther folded work
- Box or Tray: A box, tray or pan folded from one blank: a base with four sides turned up, with or without a flange round the top.
- Straight Duct: A straight length of rectangular duct: one blank wrapped round to one seam, two L-shaped pieces, a U and a flat side, or four sides.