The temperature of the room where the blowing machines are located, is critical. The temperature of the preforms depends on the storage conditions. When it’s under 15°C, the preforms are too cold and may explode during blowing process. It is better to wait for a while for the suitable temperature. When it’s above 35°C, the mechanical properties of PET is weakening, there may be risks of bottle necks crack. Preform necks are very sensitive and fragile when the temperature is above 45°C.
Hot exhaust system is recommended in order to keep the room temperature as stable as possible. It is also necessary to place the preforms next to the machine for several days before use them. The temperature has big influence on heating and material distribution so we should try our best to avoid huge differences in temperature. The oven should be equipped with a durable venting system.
The IR camera is used to monitor the temperature of the preforms’ surface, so we can adjust the oven’s temperature during production. As we all know, the IR camera cannot read the internal temperature of the preform. We can use the radiation of the infrared lamps and the convection currents of the circulation fans to rise the inner temperature of the preforms in a way of heat conduction.
If the room temperature drop 10°C, the heat of the oven will increase in order to compensate the temperature loss of preforms’ surface. Thus, the inner temperature of the preforms will increase. The configuration of the infrared lamps is only regulated from the data of the IR camera, if the room temperature changes, it will also affect the material distribution. The area under preform necks is the most sensitive part to the temperature variations. The injection point of the preforms get heat up easier than other parts. Increase the material at the bottom of the bottle will decrease the material at the top or vice-versa. In order to keep the integrity of the blowing process, the room temperature shall be controlled in the range of 15°C-35°C.