The core method to assess aluminum plate flatness lies in "visual inspection + tool measurement + standard comparison", combined with application requirements for rapid and accurate judgment. Detailed approaches are as follows:
Select a well-lit environment and place the aluminum plate on a horizontal surface (e.g., marble table, level workbench).
Irradiate the surface with side light from the side or obliquely above, observing for unevenness, waviness, or warpage. A surface with no obvious light and shadow fluctuations is initially deemed flat.
For splicing scenarios (e.g., curtain walls, roofing), align the edges of two aluminum plates and check for gaps or height differences at the joint—no gaps indicate qualified flatness.
Steel Straightedge + Feeler Gauge Combination: Use a steel straightedge with precision ≥0.02mm (length not less than the aluminum plate’s short side) to fit tightly against the surface along the longitudinal, transverse, and diagonal directions. Measure the maximum gap between the straightedge and the plate with a feeler gauge.
General purposes (e.g., decorative plates): Gap ≤0.3mm/m is qualified.
High-precision scenarios (e.g., printing, precision machining): Gap ≤0.1mm/m.
String Pulling Method: Stretch inelastic fine steel wire across both ends of the aluminum plate, measuring the maximum vertical distance between the wire and the surface. The smaller the distance, the better the flatness—generally requiring ≤0.5mm/2m.
Laser Flatness Detector: Rapidly obtain 3D data of the aluminum plate surface through laser scanning, automatically calculating flatness error with precision up to 0.001mm. Suitable for mass quality inspection.
Dial Indicator/Metric Dial Indicator: Fix the aluminum plate on a horizontal platform, move the indicator needle evenly along the surface, and record the pointer fluctuation range. Fluctuation ≤0.05mm meets high-precision standards.
| Application Scenario | Flatness Requirement | Reference Standard |
| General industrial use | ≤3mm/m (ordinary grade); ≤1.5mm/m (high-precision grade) | GB/T 3880《General Industrial Aluminum and Aluminum Alloy Plates and Strips》 |
| Curtain walls/printing | ≤0.5mm/m | Industry default requirement |
| Roofing | ≤1mm/m | Industry default requirement (adjustable on-site) |
| Customized products | Subject to contract agreement (e.g., ≤0.2mm/m) | Custom technical specifications |
GB/T 3880 is the core national standard for aluminum plate flatness, applicable to most general industrial scenarios.
For high-end applications (e.g., precision electronic components), stricter enterprise or international standards (e.g., ASTM B209) may apply.
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