Local carbonization and blackening of the product

Black carbonized areas appear locally on the product. When this defect occurs in products of Process No. 3, it is usually related to a specific process parameter range or equipment status. If it persists, it will directly affect the product qualification rate and production cycle, increasing material loss and rework costs. Timely diagnosis and elimination is a basic requirement to ensure stable production.

1. Mold design factor: The local mold temperature is too high, the material residence time is too long, the reaction exotherm is concentrated and cannot be dissipated, and material accumulates in mold dead corners. 2. Preheating factor: The preheating temperature and time of the material (especially thermosetting molding compounds) directly affect its flowability and curing behavior; improper preheating can lead to poor filling or uneven curing, which is a key control point unique to compression molding. 3. Molding pressure factor: In compression molding, pressure is not only used to overcome flow resistance, but also directly affects the compactness of the product and the degree of fiber wetting; insufficient pressure is an important cause of loose products and insufficient strength.

1. Process parameter optimization and adjustment: Check the mold temperature uniformity, reduce material residence, enhance heat dissipation, and eliminate mold dead corners. 2. Systematic troubleshooting method: Compression molding problem troubleshooting follows the order of "material -> temperature -> pressure -> mold". First check the preheating and flowability of the material, then verify the mold temperature distribution and curing time, next adjust the molding pressure and mold closing speed, and finally check the mold venting and demolding conditions. 3. Preventive management: Establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) assessments. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify countermeasures as PFMEA control points.

This problem is a typical manifestation of local carbonization and blackening of the product in compression molding, and the core of the solution lies in the reasonable preheating of the material and the guarantee of flowability, as well as the precise matching of mold temperature and molding pressure. It is recommended to make coordinated adjustments from both the material state and process parameters.