Why is the weight of the blow molding machine unstable?

Update: 2022/04/21
Abstract:

Blow molding machine is a kind of empty container equip […]

Blow molding machine is a kind of empty container equipment. It mainly makes plastic pellets into containers through blow molding process. The more common machine types are hollow extrusion blow molding machines with PP and PE molding at one time, and secondary molding with PET, PC or PP. The injection stretch blow molding machine, as well as the newly developed multi-layer hollow extrusion blow molding and stretch blow molding.
At present, most of the blow molding machines are still two-step blow molding machines, that is, the plastic raw materials are first made into preforms and then blown. Nowadays, environmentally friendly plastics made of PET are commonly used, that is, blow molding machines. Blow molding machine is a kind of blow molding machine, which is a kind of blow molding machine, that is, a hydraulic blow molding machine.

Usually, when the automatic blow molding machine is produced, the weight of the product is unstable, and the weight of the product exceeds the specified deviation. The characteristic of weight instability is that the length of the nozzle material at the bottom of the bottle is different. In severe cases, due to the insufficient length of the material tube, the product cannot be formed by blowing, and the main reasons for the weight instability are as follows:
1. In production, the temperature control is inaccurate or the temperature deviation is large, and the installation position of the temperature measuring point (thermocouple) is unreasonable, which causes the temperature to produce periodic deviation. As the temperature deviation increases, the deviation affecting the weight also increases. When the temperature rises, the stretching of the extrusion barrel increases. In the same operation cycle, the nozzle material at the bottom of the bottle increases and the weight of the product is reduced. When the temperature is low, the weight of the product increases. When the thermocouple is in poor contact, there are similar failures. If the thermocouple is bad, the extrusion amount is reduced, and when the temperature is lower than the melting point of the plastic, the motor current increases. It cannot be extruded below the melting point of the plastic. Whether the installation position of the thermocouple is reasonable and the size of the temperature control area of ​​the measuring point will directly affect the extrusion stability.
2. The running time of the two mold bases is inconsistent (the difference is too large). If the downward flow of the material pipe is at a constant speed, when the time difference between the left and right mold bases is large, the weight of both sides will be unstable. The die set that runs faster is heavier, and the die set that runs slower is lighter due to stretching. The solution is to adjust the die set on both sides to approximate the run time.
3. The unstable extrusion volume is caused by the unstable rotation speed of the motor and the inappropriate belt tightness.
4. Because different plastic raw materials or mixing ratios change, the output is different, and the amount (percent) of the nozzle material added often changes, thus affecting the extrusion volume.

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