As a precision functional component, the aluminum press cap of a spray pump head requires a comprehensive approach to defect detection, combining material properties and usage scenarios. This approach primarily utilizes non-destructive testing (NDT) techniques, supplemented by functional testing. Aluminum press caps are typically formed through die casting, which may result in internal defects such as porosity, shrinkage cavities, cracks, or inclusions. These defects directly affect the press life, sealing performance, and structural strength, necessitating early identification through targeted testing methods.
X-ray flaw detection is the core method for detecting volumetric defects within aluminum press caps. By penetrating the casting with X-rays, low-density areas such as porosity and shrinkage cavities will form dark spots in the image due to differences in X-ray absorption, thus accurately locating the defect's position and size. This method is particularly suitable for inspecting medium-thick-walled components (such as the main structure of the press cap), capable of identifying micropores with a diameter ≥0.5mm, ensuring that the internal density meets requirements. For complex curved surfaces or thin-walled areas, a digital detector is needed to improve image clarity and avoid missed defects.
Ultrasonic testing excels at detecting deep defects in thick-walled areas. Utilizing the reflection characteristics of high-frequency sound waves within aluminum, abnormal reflection waves are generated when the sound waves encounter cracks or shrinkage cavities. The depth and size of defects can be calculated by analyzing the reflection time and amplitude. This method is highly sensitive to planar defects (such as delamination and cracks), and the equipment is portable, making it suitable for rapid on-site screening. However, it should be noted that ultrasound is sensitive to defect direction; defects parallel to the sound wave propagation direction may be missed. Multi-angle detection is necessary to improve accuracy.
Pension joint testing is a specialized method for surface-open defects. A penetrant containing fluorescence or colorant is applied to the press cap surface. The penetrant penetrates into cracks or pinholes through capillary action. After removing excess penetrant, a developer is applied to visualize the defect traces (fluorescence requires UV light observation). This method is simple to operate and low in cost, especially suitable for detecting surface defects such as casting cracks and cold shuts. However, it cannot detect internally closed defects, and the surface must be thoroughly cleaned before testing to avoid interference.
Eddy current testing is suitable for rapid screening of surface and near-surface defects. Using the principle of electromagnetic induction, the probe induces eddy currents on the aluminum surface. If cracks or inclusions are present, the eddy currents will be distorted, and the presence of defects can be determined by detecting the distortion. This method has an extremely high detection speed (1-2 meters per second), making it suitable for integration into automated production lines. However, its detection depth is limited (≤5mm), and it is prone to missing tiny defects (<0.3mm), requiring verification in conjunction with other methods.
Computed tomography (CT) is the ultimate means of high-precision inspection. Through multi-angle X-ray scanning and 3D reconstruction, the morphology, location, and size of internal defects in the press cap can be visually displayed with micron-level accuracy. This method is particularly suitable for defect analysis of complex structures (such as internal flow channels and inserts), and can quantify parameters such as porosity and crack volume. However, the equipment cost is extremely high, and it is only used for critical components or fault analysis.
Functional testing is a crucial step in verifying the actual performance of the press cap. By simulating real-world usage scenarios, continuous pressing tests can assess the mechanical durability of the press cap, detecting any jamming, leakage, or flow reduction during pressing. Sealing performance tests verify its sealing effect under static and dynamic pressure through airtightness or liquid tightness checks. Material compatibility testing analyzes the chemical interaction between the press cap material and the liquid it contains, preventing corrosion or degradation that could lead to failure.
Internal defect detection of the aluminum press cap in the spray pump head requires a comprehensive approach combining non-destructive testing and functional testing. X-ray inspection, ultrasonic testing, and penetrant testing form the core combination for defect investigation, while eddy current testing and CT scans provide supplementary verification. Functional testing ensures performance in actual use. Through the synergy of multiple technologies, the quality and reliability of the press cap can be comprehensively evaluated, providing data support for product optimization and quality control.
