1. Influence of forming quality
Dimensional accuracy and shape stability
When the cooling time is insufficient, the material is not completely solidified, and residual heat may cause shrinkage deformation or dimensional deviation after demolding. Properly extending the cooling time can reduce deformation caused by thermal shrinkage and ensure that the product conforms to the mold contour.
Surface quality
Cooling too quickly may cause atomization, orange peel or local stress marks on the surface; while uniform cooling can obtain a smooth surface. For example, if thick-walled products are cooled unevenly, the temperature difference between the inner and outer layers will cause shrinkage differences, forming depressions or warping.
Internal stress and warping
Uneven cooling will cause imbalanced stress distribution inside the material, and stress release after demolding will cause warping. Especially for products with complex geometries, shrinkage needs to be balanced by adjusting the cooling time or mold temperature gradient.
2. Adaptation of material properties
Material type
Different plastics (such as PETG, ABS, HIPS) have different glass transition temperatures (Tg). For example, PETG requires a longer cooling time to ensure full solidification, while PS may be fixed in a shorter time.
Sheet thickness
Thick sheets (such as those above 5mm) require longer heat dissipation time, otherwise the center layer may not be fully cured, resulting in inconsistent overall shrinkage after demolding.
3. Synergy of mold design
Thermal conductivity of mold material
Aluminum molds have fast thermal conductivity and can shorten cooling time; resin or wood molds have poor thermal conductivity and require extended cooling or additional auxiliary cooling measures (such as water cooling channels).
Cooling system design
The built-in cooling pipeline in the mold can accelerate heat exchange, achieve local precise temperature control, reduce cooling time and avoid defects.
4. Trade-off of production efficiency
Production cycle
Excessive cooling time will reduce production capacity and increase costs. It is necessary to find the critical point through experiments: shorten the cooling time as much as possible while ensuring quality. For example, thin-walled products may only take 10-20 seconds, while thick-walled products may take more than 60 seconds.
Automated production line optimization
In high-volume production, multi-station parallel cooling or air cooling/water cooling systems can be used to improve efficiency.
5. Environment and process control
Ambient temperature and humidity
High temperature and high humidity environment will prolong the natural cooling time, which needs to be compensated by forced cooling (such as fans and sprays).
Process parameter linkage
Cooling time needs to be optimized in coordination with parameters such as heating temperature and vacuum pressure. For example, too high a heating temperature may cause the material to soften excessively, requiring longer cooling time to set.
