Analysis of the causes of weight instability in the production of bottle blowing machines


Analysis of the causes of weight instability in the pro […]

Analysis of the causes of weight instability in the production of bottle blowing machines

The blow molding machine is a device that makes plastic particles into hollow containers through a blow molding process. The more common models include a one-shot hollow extrusion blower using PP and PE, and two-shot molding using PET, PC or PP. Injection stretch blow molding machine, and the newly developed multilayer blow extrusion and stretch blow molding.

Most bottle blowing machines are still two-step bottle blowing machines, that is, plastic raw materials must be made into preforms before blowing. Nowadays, the commonly used environmentally friendly plastic is made of PET. Blow molding machine: After the liquid plastic is sprayed out, the plastic body is blown to the mold cavity of a certain shape by using the wind force blown by the machine to make a product. This machine is called a blow molding machine. It is also a kind of bottle blowing machine, namely hydraulic bottle blowing machine.

Usually in the production of automatic blow molding machine, it is often encountered that the weight of the product is unstable, and the weight of the product exceeds the prescribed deviation. The characteristic of the unstable weight is that the nozzle material at the bottom of the bottle has different lengths. In serious cases, the product is not formed due to the insufficient length of the material tube. The main reasons for the unstable weight are the following conditions:

1. In production, the temperature control is inaccurate or the temperature deviation is large. The installation position of the temperature measurement point (thermocouple) is unreasonable, which causes a periodic deviation in temperature. As the temperature deviation increases, the deviation affecting the weight also increases. When the temperature rises, the extrusion barrel stretches more. In the same operation cycle, the nozzle material at the bottom of the bottle increases, and the product weight decreases. When the temperature is low, the weight of the product increases. When the thermocouple is in poor contact, there is a similar failure. If the thermocouple is broken, the amount of extrusion decreases, and when the temperature is below the melting point of the plastic, the motor current increases. It cannot be extruded below the melting point of plastic. Whether the installation position of the thermocouple is reasonable and the size of the temperature control area of ​​the thermocouple measurement 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 material pipe flows downward at a constant speed, when the time difference between the left and right mold bases is large, the weight on both sides will be unstable. The faster the die frame is, the heavier the weight, and the slower the die frame is, the lighter the weight is due to stretching. The solution is to adjust the mold base on both sides to make the running time close.

3. The amount of extrusion is unstable, and the amount of extrusion is unstable due to the unstable rotation speed of the motor and the inappropriateness of the lightness of the belt.

4. The reason for the plastic raw materials is different due to the different plastic raw materials or the mixing ratio changes. The amount (percentage) of the added water nozzle material often changes the amount of extrusion.