Acceptance criteria for X-ray and CT testing of structural component molds

Acceptance criteria for X-ray and CT testing of structural component molds
Structural defects are judged according to ASTM E505, with acceptable levels 1-2 and level 3 repair. CT is used for wall thickness and porosity analysis.
First clarify the criteria for judgment, then discuss qualification
The criteria for X-ray detection should be specified in the drawings or technical agreements. Commonly cited is ASTM E505, and some customers also use custom enterprise standards.
ASTM E505 classifies aluminum alloy castings into grades 1-8, with smaller numbers indicating fewer defects. Structural components usually require 1-2 levels, with safety components being more stringent.
If the standards are not clearly stated, the interpretation of the same film by both the supply and demand sides may be completely different. This is the main source of acceptance disputes.
The applicability and limitations of X-rays
X-rays are suitable for detecting volumetric defects such as shrinkage, porosity, and inclusions. The detection rate of area type defects, such as cracks, is relatively low.
The detection thickness is limited. When the thickness of aluminum alloy parts exceeds 80mm, the penetration power of conventional X-ray machines is insufficient, and accelerators or CT scans need to be used instead.
The angle of filming will affect the detection rate. A single angle may miss detection, and it is recommended to have at least two directions for critical areas.
What can CT provide
CT can provide three-dimensional density distribution and locate the depth and volume of defects. Especially useful for wall thickness analysis, with an accuracy of up to 0.05mm.
Scanning costs are high, and single item inspection often takes several hours. Mostly used for new product development, failure analysis, and first article confirmation, not suitable for full inspection.
The equipment investment for CT is large, and most foundries adopt outsourced testing. The outsourcing cycle is usually 3-7 days and needs to be included in the project plan.
How to determine the sampling plan
The first piece must be inspected, covering all critical areas. At T0 stage, it is recommended to perform a CT scan to establish a baseline for defect distribution.
During the batch stage, sampling is conducted in batches, with a common ratio of 5% -10% per batch. Critical safety components can be increased to 20% or fully inspected.
The sampling location should be representative. Only inspecting parts that are easy to form is equivalent to not inspecting. The root of the spoke, the boundary between thickness and thickness, and the vicinity of the sprue must be covered.
Rules for handling defects
1-2 level defects are acceptable, but need to be evaluated for their location in critical stress areas. The tolerance of the same level varies in different positions.
Level 3 defects are usually repaired. Welding repair should be carried out according to the process evaluation, and retested after repair. The number of repairs generally does not exceed 2 times.
Defects exceeding level 3 or located on the sealing surface are recommended for disposal. The economics and risks of repair need to be evaluated separately.
The coordination method of Xinfeng mold
Mold factories usually do not undertake inspections, but they need to cooperate in providing defect location and cause analysis. The distribution of defects on X-ray images can be used to infer issues related to casting and cooling.
Xinfeng Mold will require customers to provide a first piece inspection report for the structural component mold project, in order to review whether the shrinkage and waterway design meet expectations.
The value of this closed loop for subsequent mold development is higher than the single acceptance itself.
Frequently Asked Questions
Q: What are the criteria for X-ray judgment?
Answer: Commonly used ASTM E505, grades 1-2 are acceptable.
Q: What is the difference between CT and X-ray?
Answer: CT provides three-dimensional distribution with an accuracy of 0.05mm, which is more expensive.
Question: What is the sampling ratio?
Answer: Batch production is common at 5% -10%, and safety components can be improved.
Q: How to deal with Level 3 defects?
Answer: Usually, it is repaired and retested after repair.
Q: Is there a limit on the number of repairs?
Answer: Generally not exceeding 2 times, process evaluation is required.
Q: Does the mold factory need to conduct testing?
Answer: Usually not responsible, but needs to cooperate with defect analysis.
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