Mold Concerns
| Cooling |
When designing cooling channels, pay special attention to the sections of the mold forming inside corners. Corners place a higher thermal load on this mold area than on the mold area in contact with the outside corner. The resulting heat buildup slows cooling and shifts the molten core toward the inside. As the shifted molten core shrinks and solidifies, it pulls disproportionately on the inside corner, leading to corner warpage and a reduction in corner angle. This phenomenon causes the classic hourglass distortion in box-shaped parts. There are several possible ways to correct heat buildup on inside corners including:
- Moving a cooling line closer to the hot corner area (see figure A) to more effectively remove heat;
- Rounding the corner or using corner coring to remove material from the corner and lessen heat buildup (see figure B);
- Direct cooling into corners with bubblers or baffles (see figure C);
- Using high-conductivity metal inserts or heat pipes to remove excess heat and reduce corner distortion; and
- Placing ejector pins away from the inside corners. The air-gap clearance surrounding ejector pins in corners acts as an insulator and hinders heat flow out of the corner.
