Sound Attenuator: flat pattern
The casing of a sound attenuator: rectangular with a row of splitters, or round with a pod on its axis. The casing of a sound attenuator and what stands in it: a rectangular casing with a row of splitters, or a round casing with a pod on its axis, each folded or rolled from sheet.
Open the sound attenuator in SheetMorphConfigurations
- Rectangular, with splitters. A rectangular casing with a row of splitters standing from its bottom to its top, half an airway from each wall.
- Round, with a pod. A round casing with a round pod on its axis.
A worked example
The rectangular, with splitters configuration with the sizes SheetMorph opens with, in mm. 4 plates: the casing and 3 splitters, alike: 16 parts, 8 seams.
| Blank of P1 | 3004.0 mm × 1500.0 mm |
| Blank of T1P1 | 1396.0 mm × 1500.0 mm |
| Blank of T2P1 | 1396.0 mm × 1500.0 mm |
| Blank of T3P1 | 1396.0 mm × 1500.0 mm |
| Length of cut, every outline and hole | 26384.0 mm |
| Bends (12) down, the pattern drawn outside face up | 90.0° |
| Casing width | 901.00 mm |
| Casing height | 601.00 mm |
| Length | 1500.00 mm |
| Open area, per cent of the inside | 67 |
| Girth of the blank | 3004.00 mm |
| Splitters | 3 |
| Thickness of each | 100.00 mm |
| Girth of each blank | 1396.00 mm |
| Airway between splitters | 200.00 mm |
| From the inside of the wall to the first splitter | 100.00 mm |
| P1 Casing, Side 1, -Y, long | 3004.00 mm |
| P1 Casing, Side 1, -Y, wide | 1500.00 mm |
| T1P1 Splitter 1, Side 1, -Y, long | 1396.00 mm |
| T1P1 Splitter 1, Side 1, -Y, wide | 1500.00 mm |
| Plates | 4 |
| Triangular facets | 32 |
| Pattern extent X | 3004.00 mm |
| Pattern extent Y | 7125.00 mm |
| Developed area | 10,788,000 mm² |
| Total cut length | 26384.00 mm |
| Longitudinal seam length | 6000.00 mm |
How it is developed
True-shape development of flat sides. This is an exact development: the surface unfolds without stretching, so the pattern closes exactly.
- The casing is folded and seamed at its corners as laid out under Pattern.
- Each splitter is one blank folded at three corners and seamed at the fourth: two broad sides of perforated sheet facing the airways, and two narrow sides against the top and the bottom of the casing.
- The airways between the splitters are equal, with half an airway between each wall and the splitter beside it.
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): 32 facets form a casing and 3 splitters in it: every edge inside a part joins exactly two facets, every open edge one (V - E + F = 0).
- Developed edges equal true 3D lengths (passed): 96 facet edges compared between the 3D surface and the flat pattern (max deviation 7.96e-13).
- Shared edges and seam closure (passed): 28 internal edges are shared vertex-for-vertex between adjacent facets; 4 seam(s) have mating edges of equal true length (max deviation 4.55e-13).
- 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 5.59e-9).
- Cut outlines closed and non-overlapping (passed): 4 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 noses and tails of the splitters and the pod are not drawn; the ends are left open for the nose and tail pieces made separately.
- The acoustic infill, its retaining mesh and the perforation pattern are not drawn: the perforated sides are named on the plates.
- Splitters are alike and stand the full height of the casing; the pod is held by struts that are not drawn.
- 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.
Casing. The casing runs along the Z axis from End A at Z = 0 to End B. A rectangular casing has its width along X and its height along Y; under Pattern it is made in one piece, two L-shaped pieces, a U and a flat side, or four sides. A round casing is cut along its bottom (-Y).
Splitters and pod. Splitters are thin rectangular boxes as long as the casing, standing against its inside from the bottom to the top. They are spaced across the width with equal airways between them and half an airway at each wall, so the air passes the same lining on every side. Each splitter is folded in one piece; its two broad sides face the airways and are cut from perforated sheet. A pod is a round tube on the axis of a round casing.
Sizes and thickness. The casing is entered as inside, mid-thickness or outside sizes, the splitters by their thickness overall and the pod by its outside diameter. Every part is developed on its mid-thickness surface.
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 sound attenuatorOther dampers, doors and attenuators
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