How to judge whether the power of infrared heating lamp is adjusted appropriately?
Observe the heating effect of preform
Temperature distribution uniformity:
Use infrared thermal imager to detect the temperature distribution on the surface of preform. Under appropriate power, the temperature difference between the circumferential direction and the axial direction of the preform should be controlled within a small range. For high-quality blow molding requirements, this temperature difference usually does not exceed ±5℃.
Time to reach target temperature:
Depending on the material of the preform and the requirements of the blow molding process, each material has its appropriate blow molding temperature range. For example, the blow molding temperature of PET preforms is generally between 100-180℃. Within the given heating time (this time is determined by the production speed of the blow molding machine), if the preform can stably reach this temperature range, it means that the power adjustment is appropriate. For example, when the production speed of the blow molding machine is 60 preforms per minute and the heating time of each preform is set to 10 seconds, if the infrared heating lamp can make the preform reach 100-180℃ within 10 seconds, the power meets the requirements.
If the preform takes too long to reach the target temperature, the power may be too low; conversely, if the preform exceeds the target temperature range too quickly, the power may be too high. In both cases, the power needs to be readjusted.
Appearance quality:
Observe whether the appearance of the bottle is defective. Inappropriate power may cause defects on the bottle surface. For example, too high power may cause local overheating of the preform, resulting in bubbles, scorch marks or discoloration on the surface of the bottle. For colored bottles, discoloration may be more obvious; for transparent bottles, bubbles and scorch marks will affect the transparency and appearance of the bottle.
When the power is insufficient, the bottle may appear wrinkled and uneven because the material is not fully softened, especially in the bottom and shoulders of the bottle where the shape changes greatly.
