The entire process of mold inspection and certification: A quality control guideline from mold testing to acceptance inspection

2026年4月8日

Component Inspection (Prototype Testing)
The sample provided by the last trial molding can most comprehensively reflect the level of the mold. Usually, this sample is sent to the customer for inspection, and the inspection results are regarded as an important basis for mold acceptance. The correctness of the basic dimensions of the sample reflects the manufacturing accuracy of the mold. Therefore, during the acceptance process, component inspection must be carried out first.
Receiving environmental conditions
The inspection of the components should be conducted at least 16 hours after the plastic part has been formed or the required post-processing has been completed.
Standard environment: Temperature 23 ± 2℃, relative humidity 50 ± 6%, dew point temperature 21℃, atmospheric pressure 890 - 1060 hPa, air flow rate ≤ 1 m/s.
If the actual environment is not standard, it can be adjusted through negotiation between the two parties, or the measured values can be corrected using the length expansion coefficient.
2. Inspection of Basic Dimensions of the Product
After obtaining the sample, first check whether the overall shape is correct and whether the basic form conforms to the product design concept; then conduct an inspection of the basic dimensions of the product.
3. Dimensional Inspection of Products
The dimensional fit refers to the fitting dimensions between products or between products and related components, including local fitting dimensions and overall relative position dimensions. It must be strictly inspected according to the drawings.
4. Trial Assembly Inspection
After the checks on basic dimensions, external dimensions, and mating dimensions are completed and basically meet the design requirements, a trial assembly inspection is carried out. This is an important method for inspecting the products and can verify the mating dimensions and spatial surfaces.
5. Inspection of Product Appearance Quality
After pre-installation meets the requirements, a comprehensive inspection of the appearance quality of the product is necessary. Appearance quality refers to whether the product meets the requirements without common defects (such as dimples, flash, bubbles, etc.).
6. Dynamic and Static Balance Tests
For components operating at high speeds, dynamic and static balance tests must be conducted; for parts with high strength requirements, impact resistance tests, strength tests, and high-temperature tests, etc. are necessary. These tests are important bases for product certification.
II. Mold Acceptance
After the finished parts have undergone comprehensive acceptance, the mold itself also needs to be inspected. If a mold can provide complete samples, it can be regarded as having a basically reasonable overall structure. However, other parts of the mold still require careful examination. The processing accuracy of the mold structure parts, the method of inserts, and the heat treatment methods all directly affect the service life of the mold.
1. Mold appearance quality
Observe the mechanical processing level of the mold: The mold should be straight, with both the top and bottom surfaces being formed by grinding; the external dimensions should be uniform, and there should be (2-5)mm × 45° chamfers on all four sides. Mold with rough appearance and inconsistent lengths, even if they do not affect the internal quality, often indicate insufficient manufacturing level. The inspector should conduct strict inspection of the appearance quality.
2. Inspection of main mold component dimensions
After the plastic parts have been accepted as qualified, the accuracy of the mold cavity dimensions has been basically confirmed. However, the tolerances of other mold dimensions still need to be further inspected to ensure compliance with the drawings and certification requirements.
3. Condition of main structural components
Ensure that the moving parts (such as sliders and inclined dies) in the mold structure, mold inserts, inserts, and wear-prone parts, etc., are functioning properly. Check for any jamming, wear, or other defects.
4. Mold Materials and Heat Treatment
When designing the mold, users can specify special requirements for the mold materials. The heat treatment of standard mold components should follow national standards. During inspection, the material certificates and heat treatment reports need to be verified.
5. Wearable Parts and Spare Parts
Each set of molds has its own wear-prone parts. Spare parts should be provided before the molds are delivered. For non-standard parts, the mold factory can be requested to produce two copies at the same time, in case the production factory needs to replace them. During the factory inspection, the spare parts list and management situation should be checked.
III. Mold Testing and Quality Control of Molds
The number of mold tests is an important indicator for evaluating the technical level of the mold factory. Reducing the number of mold tests can shorten the mold manufacturing cycle and lower costs. Therefore, during the factory inspection, the following aspects should be given particular attention:
Did the mold design take into account manufacturability and mold-testability?
Processing equipment precision and operator skills;
Mold material heat treatment and assembly quality.
By establishing a complete inspection process, conducting systematic inspections on each prototype part, and ultimately completing the mold certification, the quality of mold delivery can be effectively improved.