Sharing the Economic Factors of Extruder Screw Design

For any technical problem, it is totally wrong to ignore the economy of design. In some cases, the rationality of screw design must be analyzed more comprehensively, that is, from the perspective of economy.
The economy of extruder screw design is related to the whole extruder, which mainly includes the following aspects:
1. Energy consumption
If it decreases from 0.25 * kWHr/kg to 0.15 * kWHr/kg, for an extruder with an hourly output of 100kg, the annual electricity saved by each extruder is:
E=(0.25-0.15)*100*24*300=72000kWHr
If we calculate it at 0.088 yuan per degree point, we can save as much as 5976 yuan just for this one. Considering that the price of a medium-sized extruder is only tens of thousands yuan (the price at that time), it is obvious that this cost is considerable.
The capacity loss is not only related to the unit consumption value, but some unreasonable designs often bring more capacity loss.
For example, if the screw speed is too high, although the output is very high, the power consumption must be large at this time. If the cooling of the auxiliary engine can not keep up with it, the potential of the screw cannot be realized because the screw speed has to be reduced. In this way, the motor designed according to high speed and high productivity is far from reaching the rated load. The motor operates at low speed with low efficiency and poor economy. From this point of view, such a screw design idea is not comprehensive.
2. Service life of screw barrel system
If the corrosion effect of plastics is not considered and the machining accuracy is considered qualified, then the service life is obviously directly related to the screw speed and the pressure of molten material, and the wear of the parts with higher pressure of molten material will inevitably increase. Especially, the plastic in the feeding section is still in solid state. If high pressure is formed here, the screw and barrel will inevitably wear faster. When the screw of glass fiber reinforced plastic is directly added into the hopper, the reason why the glass fiber inlet should be designed in the middle of the barrel.
3. Processability
From the perspective of international development trend, the ratio of screw length to diameter has gradually increased. With the emergence of new screw, the structure of screw is increasingly complex. For this reason, in terms of design rationality, when it is unnecessary to use large length diameter ratio, small length diameter ratio should be selected as far as possible; When it is unnecessary to use complicated screw structure, the screw structure should be simplified as much as possible. The design of random selection of complex mixing elements without comparison and optimization is obviously unreasonable, and it is also obviously unscientific to arbitrarily increase the length diameter ratio.
In view of the importance of defining screw performance standards, we have systematically summarized this issue. Some important problems, such as fluctuation, wear and life, will be discussed in future articles.