For the shell-like product shown in the image, with its uneven wall thickness, there is a risk of inward shrinkage and collapse after injection molding. We developed two solutions.
Solution 1: Valve gate hot runner gating on the product surface
The gate location has a wall thickness of 3.17 mm, which freezes while the side wall (7.75 mm thick) is still molten. This limits the process window for packing, leading to uneven shrinkage and significant deformation due to the large thickness difference between the main wall and the side wall.
Considering filling difficulties and deformation issues,
Solution 2：Open hot runner gate at the center of the product front mold
A 0.5 mm deep recess was applied at the gate location to prevent gate residue from protruding above the product surface during subsequent removal. The gate diameter is φ6 mm, and a 0.5 mm thick bump was added on the opposite side to serve as a cooling spot.
The advantage of this solution is that the larger gate size prevents early freezing, widening the packing process window and making it easier to adjust deformation.
The drawback is that the leftover gate stub from the open hot runner requires manual removal in post-processing, increasing labor costs.
After validation, the open hot tip was ultimately selected.