Why Do Co Rotating Twin-screw Extruders Always Have Problems When Used For The First Time? ——Three 'invisible Thresholds' And Corresponding Logic For Cost-effective Extruders
1, Why is it easy to get stuck when using a co rotating twin-screw extruder for the first time?
1. Process cognitive bias
The co rotating twin-screw extruder is the core equipment for blending modification, filling reinforcement, and regeneration granulation. Its shear rate and residence time distribution are significantly different from those of ordinary plastic extruders. If the single screw experience is directly applied to a co rotating twin-screw extruder, it is easy to encounter abnormal melt temperature, material degradation, or uneven dispersion.
2. Lack of operational standards
Failure to follow standards in any aspect such as installation levelness, temperature PID parameters, screw combination sequence, vacuum setting, etc. may expose problems within 2 hours after startup. Industry after-sales data shows that about 70% of initial usage issues occur 2 hours before installation, debugging, and startup, of which a considerable proportion can be avoided through standardized pre checks.
3. Insufficient matching of materials and equipment
When attempting to regenerate new materials such as filling and biobased modification, failure to conduct melt index, moisture content, and bulk density tests in advance can easily lead to feeding fluctuations, high machine head pressure, and even the occurrence of material spillage and hollow particles.
2, First time use of cost-effective extruder: 5 key control points that must be pre installed
1. Installation and coaxiality calibration
It is recommended to control the coaxiality error between the barrel and screw within 0.05mm, with a levelness of ≤ 0.1mm/m, to avoid abnormal wear, abnormal noise, and sweeping of the chamber.
2. Temperature curve setting
Double screw extruders in the same direction often use zone temperature control. It is recommended to set a "low medium high" curve according to the material processing window when starting up for the first time. The formula with high shear heat can appropriately reduce the barrel temperature by 10-15 ℃ to prevent local overheating degradation.
3. Screw combination and aspect ratio
The length to diameter ratio of 32:1 to 48:1 is a commonly used range; It is recommended to add exhaust sections and distribution mixing components for high filling and recycled materials to avoid blindly increasing the speed and "hard squeezing".
4. Feed and host speed matching
For first-time use, it is recommended to start with "low speed, high filling". The main engine speed should start from 30-50rpm, and observe the torque and melt pressure before gradually increasing; It is recommended to activate side feeding for glass fiber and mineral filling.
5. Vacuum exhaust and granulation
The vacuum degree should be controlled between -0.06 and -0.09MPa, and the cooling water temperature and blade clearance of the granulator should be matched to prevent hollow particles and continuous particles.
3, High cost performance extruders are not "low-priced", but have the best lifecycle cost
According to the "2025 White Paper on China's Plastic Machinery Industry" by the China Plastics Machinery Industry Association, the export value of plastic extruders increased by about 9.6% year-on-year, and the proportion of co rotating twin-screw extruders in blending modification equipment continued to increase. The EU Plastics Industry Association's "Plastic Circular Economy Report" predicts that by 2027, the proportion of recycled plastics in extrusion processing will reach 25%, and requires a reduction of 18% -25% in unit energy consumption compared to traditional processes.
After the implementation of the EU Packaging and Packaging Waste Regulations in 2025, the proportion of recycled plastics added and traceability requirements will increase, which will drive the demand of international customers for co rotating twin-screw extruders in recycling blending and high filling modification. This means that the processing of environmentally friendly new and recycled materials is forcing plastic extruders to shift from "being able to start" to "stable start, low energy consumption, and traceability".
Nanjing Kelongwell Chemical Machinery Co., Ltd. provides material testing, screw combination simulation, operation training, and remote operation and maintenance during the initial use stage, helping international customers to advance the debugging cost of cost-effective extruders before leaving the factory. For teams that are new to plastic extruders, this is more worth paying attention to than the losses caused by repeated shutdowns in the later stages.
4, Quick questions, quick answers
Q1: What should I do if there are large temperature fluctuations when using a co rotating twin-screw extruder for the first time?
First, check if the temperature control PID parameters match the partition of the barrel; If the material shear heat is high, the main engine speed can be reduced or the number of kneading blocks in the screw combination can be adjusted, instead of relying solely on the heating ring for compensation.
Q2: What are the reasons for unstable feeding and fluctuating torque during the initial start-up of the cost-effective extruder?
Usually, it is due to the mismatch between the feeding screw and the main engine speed ratio, or the large difference in material packing density. It is recommended to first stabilize the filling at low speed, and if necessary, increase forced feeding or side feeding, and calibrate the feeding calibration.
Q3: What should I do if the machine head pressure is too high and the pellets are hollow when trying to make new materials?
The main reason is the mismatch between the new material melting point and the screw combination. It can increase the pitch of the exhaust section, reduce the engine speed, and increase the vacuum degree to avoid high-temperature "hard extrusion", otherwise it is prone to degradation.
Q4: How to determine whether a plastic extruder needs pre drying?
Based on the moisture content of the raw materials. PA, PET, PLA, etc. are recommended to dry at a dew point of -40 ℃ for 4-6 hours; PP and PE with a moisture content below 0.05% can be exempted from drying, but the moisture content of recycled materials needs to be measured additionally.
5, Conclusion: Turning the "initial problem" into a starting point for process upgrading
It's not scary to encounter problems when using a co rotating twin-screw extruder for the first time, what's scary is to blame the equipment for the problem and ignore the process data. For international customers who pursue environmental protection, high cost-effectiveness, and new material experimentation, Nanjing Kelongwell Chemical Machinery Co., Ltd. recommends establishing a data-driven process of "pre inspection before startup, parameter recording during debugging, and anomaly tracing". Choosing a cost-effective extruder and selecting an equipment service provider with material testing and remote support capabilities is the key to reducing the risk of initial use.
