Effect of screw speed on plastic blow molding machine

How much does the screw speed affect the plastic blow molding machine? The level of screw speed directly affects the output and product quality of the blow molding machine. Screw speed depends on the size and shape of the screw, the extruded product, and the type of raw material.

Increasing the screw speed can significantly increase the output of the blow molding machine. But energy consumption also increases accordingly. From the point of view of increasing production, it is beneficial to adopt a higher rotational speed. At the same time, due to the enhanced shearing effect of the screw on the material, increasing the screw speed can also improve the plasticizing effect of the material and improve the quality of the product.

However, the increase in screw speed should be limited.

When the rotation speed is too high, the plastic stays in the cylinder for a short time, which may cause uneven melt temperature and reduce the surface quality of the parison. Especially the increase in shear rate leads to melt fracture of HDPE plastic. In addition, when the rotation speed increases, a large amount of frictional heat is generated, causing the plastic to degrade instantaneously.

Therefore, the screw speed should be adjusted according to the actual situation.

In the past, the main method of increasing the output of blow molding machines was to increase the screw diameter. Although the amount of material extruded per unit time increases with the diameter of the screw, the blow molding machine is not a screw conveyor. In addition to extruding material, the screw extrudes, agitates and shears plastic to plasticize it. Under the premise of the same screw speed, the screw speed of the ordinary blow molding machine is 60~90 revolutions (per minute) for the traditional blow molding machine. Now it has generally increased to 100~120 rpm. High-speed blow molding machines reach 150 to 180 rpm.

When the diameter of the screw is constant and the rotational speed of the screw increases, the torque on the screw increases. When the torque reaches a certain level, the screw may twist. However, through the improvement of the material and production process of the screw, the screw structure is reasonably designed, the length of the feeding section is shortened, the flow rate of the material is increased, and the extrusion resistance is reduced, thereby reducing the torque and increasing the bearing capacity ability. screw capacity. How to design a reasonable screw to maximize the screw speed under the premise that the screw can withstand it requires a lot of experiments.

For a blow molding machine with the same screw diameter, a high-speed blow molding machine consumes more than a traditional blow molding machine and needs to increase the power of the motor.

Blow molding machines with the same screw diameter are equipped with larger motors, which seems to be a waste of electricity, but if calculated by production, high-speed blow molding machines are more energy-efficient than traditional blow molding machines. Also, this is just a comparison of motor energy consumption. The difference in energy consumption is even greater when considering the power consumption of heaters and fans on blow molding machines.

Blow molding machines with large screw diameters require larger heaters and increased heat dissipation area. Therefore, for two blow molding machines with the same capacity, the barrel of the new blow molding machine is smaller, and the energy consumption of the heater is lower than that of the traditional large screw blow molding machine, which saves a lot of electric energy during the heating process.

In terms of heater power, compared with conventional blow molding machines with the same screw diameter, high-speed blow molding machines will not increase heater power due to capacity increase. Since the power consumption of the heater of the blow molding machine is mainly in the preheating stage, in the normal production process, the melting heat of the material is mainly converted by the electric energy consumption of the motor. The conduction rate of the heater is very low, and the power consumption is not large, which is more obvious in the high-speed blow molding machine.

With the development of science and technology, plastic machinery adopts more energy-saving induction heaters.

The above is the influence of the screw speed on the plastic blow molding machine shared with you today.