Twin Screw Extrusion Granulation: The Key To Efficient Production Lies in Foresight And Maintenance
Are you facing the problem of black spots, broken bars, or unstable production on the granulation production line? With the global pursuit of sustainable production and high-performance materials, efficient extruders are not only production tools, but also core assets for enterprises to achieve environmental protection and economic benefits.
Data shows that the global extruder market size has reached 11.3 billion US dollars in 2024 and is expected to increase to 19.1 billion US dollars by 2034. In this wave of growth, co rotating twin screw extruders are becoming the preferred choice for high-end applications such as plastics, food, and pharmaceuticals due to their excellent mixing performance.
1. Industry Transformation: New Challenges and Opportunities for twin screw Extruders
The global manufacturing industry is undergoing a profound green and intelligent transformation. In the extruder market, this trend is manifested by a surge in demand for equipment with lower energy consumption, compatibility with recycled or biobased materials.
At the same time, Industry 4.0 technologies, such as real-time performance monitoring and predictive maintenance, are being integrated into plastic extruders with the aim of minimizing downtime and improving product quality stability.
The market drive for such efficient extruders comes from both increasingly strict environmental regulations and the urgent need for customized solutions from customers. Whether in the field of automotive lightweight materials or biodegradable packaging, co rotating twin screw extruders that can accurately control temperature, pressure, and shear play an indispensable role.
2. Anatomical problem: Five common causes of abnormalities in granulation production
To master complex production, one must first have a profound understanding of its underlying mechanisms. The working principle of an efficient twin screw granulator is to transport, compress, melt, and homogenize materials through the coordinated rotation of two main shafts inside the cylinder.
Any imbalance in any link may lead to the following typical problems, and accurate identification is the first step to solving them.
black dot
The black spot problem usually originates from the thermal degradation of materials. The reasons include: poor quality of the raw materials themselves; Local overheating or excessive shear of the screw leads to material carbonization; Excessive pressure on the machine head leads to an increase in reflux material, which prolongs the heating time of the material; The aging of the equipment leads to an increase in the gap between the screw and the barrel, which can easily accumulate carbonization materials; And the exhaust port is not cleaned in a timely manner.
Broken bar
A broken strip is the result of insufficient traction force to overcome the weak strength of the strip. The causes are complex, mainly including: external impurities mixed in; Carbonization generated internally due to improper manufacturing processes; Poor plasticization of materials, with unmelted "lumps" present; The physical properties of raw materials (such as melt index and viscosity) vary greatly from batch to batch; And the exhaust is not smooth, causing gas to be trapped in the material strip.
Hollow particles
The hollow inside the particles is essentially due to the ineffective elimination of gas. The primary reason is the insufficient efficiency of the exhaust system, whether it is natural exhaust or vacuum exhaust, resulting in blockages, leaks, or improper settings. Secondly, poor plasticization can also lead to insufficient melt strength, making it impossible to encapsulate the gas. In addition, for crystalline plastics, a low cooling water temperature may cause the material to shrink too quickly, forming shrinkage holes.
Material emission (natural exhaust port/vacuum port)
Material leakage is a direct manifestation of pressure imbalance in a specific section. At the natural exhaust outlet, it may be due to the mismatch between the feeding and the main engine speed, low or high temperature in the area (emitting raw materials), and ineffective reduction of the screw groove pressure by the screw combination. At the vacuum port, in addition to similar reasons, excessive vacuum pumping force and high head pressure leading to increased reflux are also common factors.
Bridge (hopper/discharge port)
Bridge construction affects continuous and stable feeding. At the hopper, it is often caused by the moisture absorption and agglomeration of the powder, increased friction, or clumping of the mixture. At the discharge port, it may be due to some low melting processing aids softening prematurely in the feeding section and sticking to the warehouse wall.
3. Prevention and Control: Building an Efficient Operating System with Maintenance as the Core
Prevention is far better than cure. Establishing scientific operation and maintenance procedures is the cornerstone of ensuring the long-term stable and efficient operation of co rotating twin screw extruders, and extending their service life. Standardized processes can maximize the performance potential of efficient extruders.
Before driving, a rigorous' health check 'must be conducted
For the co rotating twin screw extruder, manual turning is required after installation to confirm that the screw rotates easily and the combination is correct. At the same time, it is necessary to systematically check the circuit, cooling water circuit, lubricating oil level and oil circuit, metering and exhaust system, and ensure that the machine head bolts are tightened. After heating to the set temperature, it should be kept warm for at least 10 minutes to ensure uniform temperature.
Adhere to the principle of smooth operation during operation
Measurement feeding should be adopted, and the torque of the host should be closely monitored to avoid overload. At the beginning, the host runs at low speed. After the mouth mold discharges the material normally and guides it onto the traction equipment, slowly and synchronously increase the speed and feeding amount until the set value is reached. The entire process needs to maintain a balanced feeding.
Parking and cleaning, preparing for the next efficient start
When parking, stop feeding first and let the main engine run at low speed to exhaust the materials inside the machine. For co rotating twin screw extruders, if the screw configuration needs to be replaced in the next production, the screw components must be disassembled while they are still hot and thoroughly cleaned. The barrel and head of the machine also need to be cleaned thoroughly. Copper or wooden tools should be used for cleaning to avoid damaging the surface of the screw and barrel.
Daily and regular maintenance are the continuation of investment
It is strictly prohibited for the equipment to idle to prevent dry grinding between the screw and the barrel. If there is any abnormal sound or vibration during operation, the vehicle should be stopped immediately for inspection. It is necessary to prevent hard objects such as metals from falling into the hopper. For machine heads equipped with pressure sensors, careful maintenance is necessary to avoid collisions. Regular maintenance of the lubrication system and inspection of electrical components in accordance with the equipment manual is a guarantee of long-term reliability.
4. Practical Q&A: Quick Diagnosis and Emergency Response Guide
When problems suddenly arise, a calm and systematic investigation can often quickly restore production. The following are quick response strategies for common emergency situations.
How to quickly identify and address "black spot" issues?
Firstly, check whether there are impurities or degradation in the raw materials themselves. Secondly, observe whether the black spots appear periodically, which may indicate local overheating or wear points on the screw or barrel. Immediately inspect and clean the natural exhaust port and vacuum exhaust port, as these areas are prone to accumulation of carbonization. At the same time, review the temperature settings of each section to avoid local overheating.
What order should be used to troubleshoot "broken bars" in production?
Follow the order from outside to inside, from simple to complex. Firstly, immediately check for visible impurities in the material strip and investigate the feeding process. Secondly, observe the morphology of the fracture surface. If the material strip breaks after "bulging", it is likely due to poor exhaust and the vacuum system needs to be checked. Thirdly, if there is unplasticized "raw material" on the fracture surface, the processing temperature should be increased or the screw shear element should be checked for failure.
How to deal with sudden "material leakage" from the vacuum port urgently?
Firstly, you can try slightly reducing the vacuum degree or appropriately increasing the temperature of the vacuum section (to avoid excessive temperature causing screw slippage). Secondly, check if there is an abnormal increase in the pressure of the machine head, such as whether the filter screen is clogged. As a temporary measure, filter media (such as diatomaceous earth) can be added or replaced in the vacuum pipeline. But the fundamental solution requires optimizing the combination of screws in this section and adding reverse conveying elements to reduce the pressure in the screw groove.
What should I do if the material is "bridged" in the hopper and cannot be unloaded?
For bridging caused by moisture absorption of powder, it is possible to try adding a small amount of liquid lubricant (such as white oil) to reduce friction. If it is due to the softening and bonding of low melting point additives in the feeding section, the heating temperature of the first and second zones should be appropriately reduced. The long-term solution is to improve raw material pretreatment, such as drying materials with strong moisture absorption or adjusting the form and addition method of additives in the formula.
When the granulation production line resumed a smooth roar and evenly transparent particles flowed out like flowing water, an engineer gently brushed away the dust that did not exist on the control screen. The co rotating twin screw extruder behind him, under the protection of an intelligent monitoring system, is accurately converting recycled plastic into high-performance particles.
Market reports show that efficient extruders capable of handling complex formulas and renewable materials are defining the future of the industry. And on the nameplate of this equipment, it is engraved with the words' Nanjing Kelongwell Chemical Machinery Co., Ltd. '.
