How to evaluate the quality of the screw and barrel of the injection molding machine?
How to evaluate the quality of the screw? Like other things, the criteria for evaluating the quality of the screw have gradually become clear and perfect as the understanding of the extrusion process deepens. From the previous analysis of the extrusion process, it can be seen that the screw should at least be evaluated from the following aspects:
(1) Plasticizing quality
A screw must first be able to produce products that meet the quality requirements.
The so-called compliance with quality requirements means that the products produced should meet the following requirements:
1. It has various properties that meet the requirements. Have the required physical, chemical, mechanical and electrical properties;
2. It has the required apparent quality. If it can meet the user’s requirements for bubbles, crystal points, and uniformity of dyeing dispersion.
3. The plasticizing quality of the screw meets the requirements:
1) Whether the temperature of the melt extruded by the screw is uniform, what is the axial fluctuation and radial temperature difference?
2) Whether there is the lowest melt temperature that can be formed.
3) Whether the extruded melt has pressure fluctuations.
4) Whether the dispersion of dyeing and other additives is even.
It should be pointed out that low-temperature extrusion is a current development trend, which can improve the quality of extruded products (such as reducing internal stress, etc.), prevent heat-sensitive materials from overheating and decomposition, reduce energy consumption, reduce the burden on the cooling system of the main and auxiliary machines, and increase productivity .
The so-called output refers to the output or extrusion volume through a given head under the premise of ensuring the quality of plasticization. As mentioned earlier, output is generally expressed in kilograms/hour or kilograms/revolution.
A good screw should have a high plasticizing ability. (Production capacity)
(3) Unit consumption
The so-called unit consumption refers to the energy consumed per kilogram of plastic (rubber) extruded, generally expressed by N. Where N is power (kW) and Q is output (kg/h).
The larger the value, the more energy is needed to plasticize the same weight of plastic (rubber), which means the more heating power is consumed, and the more mechanical work done by the motor enters the material through shear and frictional heat. many. vice versa.
A good screw, under the premise of ensuring the quality of plasticization, the unit consumption should be as low as possible.
The so-called adaptability of the screw refers to the adaptability of the screw to process different plastics, match different heads and different products. Generally speaking, the stronger the adaptability, the lower the plasticizing efficiency.
Therefore, we always hope that a good screw has both adaptability and high plasticizing efficiency.
(5) The difficulty of manufacturing
A good screw must be easy to manufacture and low cost.
The above criteria must be considered together, only emphasizing that one aspect is one-sided. Of course, it is also allowed to focus on ensuring that a certain standard is met for different requirements.