Louvers
Formed sheet-metal ventilation features: geometry, forming access, airflow area and boundaries of performance claims.
Tags: parts-and-design, sheet-metal, louvers, ventilation
On this page
Specify the formed louver direction, height and opening separately. Tool dimensions do not establish the free-flow area of the finished panel. TRUMPF tool 0699222
As a bounded example, TRUMPF identifies material number 0699222 as an upward single-louver tool, designated 12×5×60, with listed length 60 mm, width 12 mm and height 5 mm. The page describes cutting and forming in one stroke. These are that named tool's dimensions; 60×12 is not its certified free area, and 5 mm form height is not automatically a 5 mm clear throat. Machine compatibility, material and thickness suitability still need confirmation. TRUMPF product description
Specify the formed geometry
A flat slot description is insufficient for a louver. Preserve the opening direction and which face carries the projection, together with the geometry after forming.
| Field | Requirement to resolve |
|---|---|
| Profile | Length, width, height, radii and end shape |
| Opening | Throat geometry, opening direction and intended flow direction |
| Pattern | Quantity, pitch, rows, spacing and position from datums |
| Sheet | Alloy/grade, temper or condition, thickness and finish |
| Final envelope | Projection, surrounding clearance, panel form and edge condition |
Separate the outside form envelope from the unobstructed passage. State the relevant measurement locations on a section view when a dimension could refer to the blade, cut line or opening. Identify whether dimensions apply before or after coating and final assembly.
Tooling and forming sequence
Confirm the actual louver tool, forming direction and access before freezing the pattern. Nearby bends, fixtures, previously formed features and the punch/die envelope can limit the usable locations. A pattern that fits the flat blank can interfere after forming or during later handling.
Mate explains that consistent form height depends on punch-press stroke dynamics. Its forming guidance warns that downward forms can be flattened by subsequent operations, catch in dies or interfere with workholding; where form-down is necessary, it advises performing it last. Apply that advice to the selected machine and process rather than treating it as a complete routing instruction for every part. Mate forming guidance
Single-stroke and continuous-louver processes also differ. Mate describes a center-out incremental sequence for its continuous-louver tooling, illustrating that a long louver is not simply a scaled version of a short single-stroke feature. Obtain the tooling provider's current setup and material recommendations. This page establishes no universal minimum pitch, edge distance, material thickness, forming height or press tonnage. Mate continuous-louver guidance
Review cracks, tearing, burrs, local distortion and coating condition as acceptance questions for the actual material and manufacturing sequence. Establish whether cut edges or formed faces need additional protection or finishing. A successful forming stroke does not itself prove ventilation performance or an acceptable cosmetic surface.
Face area, free area and pressure drop
For a complete ventilation louver, face area describes the frontal envelope; free area concerns the unobstructed passage through its components. AMCA's introduction distinguishes these quantities and treats pressure drop and water penetration as separate performance criteria. Do not count the raised blade's plan area as open area. AMCA introduction to intake and exhaust louvers, June 2016
Free-area percentage is not necessarily constant with size. Greenheck's specific ESD-403 example gives 50% at 48×48 inches, 30% at 12×12 inches and 54% at 120×120 inches. These are examples for that model, not transferable percentages for a stamped panel. Its FAQ also explains that high free area does not necessarily imply low pressure drop: component aerodynamics matter. Greenheck free-area FAQ, Greenheck pressure-drop guidance
Original area and velocity example
Assume a hypothetical 100×100 mm ventilation region with ten independent openings. Each has an actual minimum clear section of 60×3 mm, measured normal to the local passage, with no end restriction, screen, overlap or other obstruction.
- Summed clear area =
10 × 60 × 3 = 1800 mm² = 0.0018 m². - Region face area =
100 × 100 = 10,000 mm² = 0.0100 m². - Geometric clear-area fraction =
1800 / 10,000 = 18%.
At an assumed volume flow of 0.0036 m³/s, average velocity based on face area is 0.0036 / 0.0100 = 0.36 m/s; based on the assumed clear area it is 0.0036 / 0.0018 = 2.0 m/s.
This is continuity arithmetic, not an AMCA free-area certification or a flow prediction. An actual formed profile may have changing area, curved flow, end restrictions or additional obstructions. The example supplies no pressure-drop coefficient, fan duty or cooling capacity. Use qualified geometry and performance data for the actual enclosure or assembly.
Performance claims need an applicable basis
Where weather exposure matters, blade direction alone is not evidence of water exclusion. Greenheck distinguishes ordinary water-penetration evaluation from wind-driven-rain testing and advises provisions to manage water infiltration. Preserve the actual model, orientation, airflow direction, test conditions and accessories when using published performance. Greenheck louver application FAQ
AMCA Publication 511-21, revision 12-22, limits its certification program to complete cataloged products within its scope. Its seal applies to the specifically certified device, not individual blades or frames. It also distinguishes certification types and requires identification when published ratings include an accessory's effect. A sheet-metal louver feature does not acquire a rain, sound or airflow rating merely because its shape resembles a certified product. AMCA 511-21 (Rev. 12-22), §§2 and 6
Similarly, do not infer an enclosure ingress rating, finger-access protection or acoustic attenuation from nominal opening dimensions alone. Define the required function and acceptance basis for the complete design, including screens, filters and surrounding construction where present.
Inspection and release
Inspect the formed profile and pattern from the specified datums, including opening direction, projection and agreed throat dimensions. Check the completed panel against its assembly clearances and acceptable distortion. Define burr, finish and cleanliness requirements at the relevant production stage.
Keep geometric inspection separate from functional verification. For a cooling application, assess the assembled flow path and relevant thermal performance; for an exterior intake, use the specified weather-performance basis. Preserve material/condition, tooling identity, drawing revision, final finish and test configuration so that later substitutions can be reviewed meaningfully.
Source versions
Reviewed 2026-11-01, America/Los_Angeles. AMCA's introduction prints June 2016. Publication 511 prints 511-21 (Rev. 12-22) and states adoption on 22 December 2022. Greenheck's individual free-area FAQ displays 26 January 2026. The cited TRUMPF, Mate and broader Greenheck live pages provide no independently verified technical revision date. Source editions and product examples are retained with those limits; calculations above are original assumptions, not catalog ratings.