5 Methods to Quickly Assess Surface Quality Defects of Aluminum Extrusion Billets
Due to the special nature of the manufacturing process of hot-extruded aluminum profiles, surface defects of aluminum profiles directly or indirectly caused by mold polishing quality or process conditions during the hot extrusion process are as follows: coarse texture, color differentiation, dark bands, bright bands, scratches, pitting (concave or convex), and poor surface finish.
Causes of Surface Rough Defects in Extruded Aluminum Profiles: In the extrusion production of aluminum profiles, common defects are relatively intuitive, such as bending, twisting, deformation, and slag inclusion.
Aluminum profiles coming off the extrusion production line are called raw material or billet, white material.
The initial judgment of surface quality is generally made after the mold is set up and 2-3 rods are extruded. During the first inspection, samples are taken to preliminarily determine whether the surface quality is acceptable. Once the surface is deemed acceptable, other items are then inspected.
5 Methods to Quickly Determine Surface Quality Defects of Aluminum Profiles
1. Tactile Touch: Touch the surface of the substrate with your hand, or use your fingernail to feel for scratches or grooves, and assess whether there are obvious tactile irregularities such as depressions or protrusions. This is applicable for evaluating various surface treatments.
2. Pencil Scratch: During the extrusion of aluminum profiles, use a pencil to scratch the surface of the aluminum profile. Assess the roughness or continuity of scratches based on touch and pencil marks. This method is suitable for surface inspection of anodized materials.
3. Spray Paint Test: During the first inspection sampling, use automatic spraying to coat the surface of the substrate, simulating the spraying effect. After 1-2 minutes of surface drying, observe for defects such as scratches, depressions, or protrusions. This is suitable for surface evaluation of coated materials.
4. Alkali Washing Test: During the first inspection sampling, take a 300mm sample segment from the third stick, and soak it in the baking mold tank for 30-40 seconds. (Note: Pay attention to the alkali concentration and tank temperature. If the concentration or temperature is too low, extend the soaking time appropriately, generally not exceeding 60 seconds.) After alkali washing, the surface of the substrate can be inspected for defects such as color separation, scratches, or mold welding lines. This is suitable for anodized materials with high surface requirements.
In addition to the four common methods mentioned above, there is another method below for everyone to refer to and learn from.
5. Surface Polishing: During the initial inspection sampling, take a 300mm sample section and use an industrial white clean cloth to polish the substrate surface transversely. After polishing, fine defects on the substrate surface become easier to observe. This method is used to identify surface defects such as fine scratches, concave and convex areas, and other defects that are difficult to detect by the above four methods. It is applicable to surface assessment for coatings, oxidation materials, and fluorocarbon materials.
The first step is to quickly determine whether the surface quality of the first inspection is qualified. Even if the first piece is qualified, abnormal situations may still occur during the extrusion process. Therefore, in actual production, it is necessary to formulate a reasonable inspection frequency according to the severity of the base material defects and the type of surface treatment, in combination with the order and customer quality requirements, following the instructions in the operating manual, to select the appropriate method for judgment; timely and accurate judgments should be made, with the principle of avoiding misjudgment and missed judgment.
