Uneven filling of multi-cavities

The filling amount of each cavity of the multi-cavity mold is inconsistent. When filling is insufficient, the product shows obvious material missing at the end of the cavity or at the thinnest wall, and the edge of the shortage is smooth or irregularly shaped. Similar to the short shot of '2079851475616104452, but in compression molding and transfer molding, insufficient filling may also be directly related to the feeding position and feeding method——if the material is unevenly distributed in the mold, local material shortage will occur even if the total amount is sufficient. Products with insufficient filling cannot be used, and their local unfilled areas of the mold will cause the flow pattern of the next molding to change.

1. Mold design factors: different runner lengths to each cavity, inconsistent gate sizes, uneven mold temperature distribution, uneven venting. 2. Feeding factor: The volume of the feeding chamber, the feeding amount and the preheating state of the material directly determine the transfer pressure and filling effect, and are key variables unique to transfer molding.

1. Process parameter optimization and adjustment: balance the runner design to make the runners to each cavity equal in length, unify the gate sizes, make the mold temperature uniform, improve the venting of each cavity. 2. Systematic troubleshooting method: Troubleshooting of transfer molding problems follows the order of 'runner -> feeding -> parameters -> mold'. First check whether the runners and gates are blocked or worn, then verify the feeding amount and material preheating, then adjust the transfer pressure and speed, and finally check the mold venting and temperature uniformity. 3. Preventive management: Establish standardized process parameter cards and quality control limits for each set of mold/product, and regularly conduct process capability index (CPK) evaluations. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify the countermeasures as PFMEA control points.

This problem is a typical manifestation of uneven filling of multi-cavities in transfer molding; the core of the solution lies in the rational design of the runner and gate system, the effective transmission of transfer pressure, and the uniform control of mold temperature. It is recommended to start troubleshooting from the runner system and transfer parameters.