Why Is The Material Contact Part Defined As A Vulnerable Part in Twin-screw Extruders? Reasons For Wear And Tear Under Different Materials And Their Actual Lifespan
1, First, let's draw a conclusion: vulnerability is a "protective consumable", not an equipment defect
The co rotating twin-screw extruder relies on two interlocking screws to complete conveying, plasticizing, and mixing. The material is forcibly sheared between the screw element and the barrel liner, and the contact surface is subjected to friction, corrosion, and alternating stress for a long time. If the contact surface is made into an irreplaceable high hardness integral structure, once worn, the accuracy and output of the whole machine will decrease. Therefore, the industry generally designs mechanical parts such as screw components, barrel liners, and threaded sleeves as replaceable and vulnerable parts, in exchange for the long life of gearboxes and core shafts at a lower cost.
2, How can different material systems accelerate losses?
1. Fiberglass/mineral reinforced materials: primarily subject to abrasive wear and tear
In systems such as 30% fiberglass reinforced PP and PA, the fiberglass continuously scratches the contact surface like small "sand particles". According to the 2024 Industry White Paper of China Plastics Machinery Industry Association, glass fiber/mineral reinforced modified plastics account for about 35% and are a common source of wear and tear. Ordinary nitride steel screw components can usually only be used for about 3000-5000 hours under this working condition; After switching to powder metallurgy or bimetallic barrel liners, it can be extended to 7000-9000 hours.
2. Recycling recycled materials: combined impact and abrasive wear
The United Nations Environment Programme's Global Plastic Outlook 2024 report shows that the global use of recycled plastics continues to rise; Although the final text of the United Nations negotiations on plastic pollution control by the end of 2024 has not been reached, many countries have clearly increased the proportion of recycled plastic use. The packaging and packaging waste regulations implemented by the European Union in 2025 further require an increase in the recycled content of packaging plastics. The sand, metal debris, and unmelted impurities in recycled materials can form impact pits and deep scratches on the contact surface. Under high impurity recycled materials, the lifespan of these contact components may be shortened to 1500-3000 hours. Environmentally friendly recycled materials do not necessarily harm equipment, the key lies in pre-treatment and material matching.
3. Flame retardants, PVC and polyester: corrosion and wear
Halogen containing flame retardants, PVC, and other materials release acidic gases at high temperatures, which first form pitting corrosion on the metal surface and then peel off during shearing. The COLOWE technical team found through experiments that under flame-retardant ABS or PVC formulations, the service life of ordinary contact surfaces is shortened by 30% to 50% compared to unfilled plastics. It is recommended to use corrosion-resistant nickel based alloys or surface coatings.
4. High viscosity engineering plastics and carbon fiber reinforcement: torque fatigue and surface fatigue
PC, PPS, Melts such as carbon fiber reinforced nylon have high viscosity, and the core shaft and threaded sleeve are subjected to alternating stress, which can easily cause microcracks; Carbon fiber has high hardness and exacerbates the wear of the cylinder liner. This type of working condition requires simultaneous attention to surface wear and core axis straightness.
3, Real service life: a set of industry data that can be referenced
Based on the comprehensive after-sales data and industry public reports from COLOWE the reference lifespan for different materials is as follows:
·Unfilled universal plastic: approximately 8000-12000 hours;
·30% fiberglass/mineral reinforcement: approximately 3000-5000 hours;
·High filling/mixed raw materials: about 1500-3000 hours;
·Flame retardant/corrosive formula: approximately 2000-4000 hours;
·Carbon fiber reinforcement: approximately 2500-4500 hours.
The above data is affected by speed, temperature, filling amount, and maintenance, and can be used as a spare parts budget benchmark for customers who are new to co rotating twin-screw extruders.
4, How does COLOWE turn 'vulnerable' into controllable costs?
Nanjing Kelongwell Chemical Machinery Co., Ltd. adheres to the "one material, one solution" policy: recommending twin-screw extruder accessories of different materials based on new materials, recycled materials, fuel blocking materials, and reinforcing materials; The whole machine adopts a modular design, and worn screw components and barrel liners can be replaced separately to reduce downtime. For customers who are trying to produce new materials, COLOWE can provide small batch samples and wear testing. By recording changes in current and melting pressure, it helps customers estimate replacement cycles, while balancing environmental protection and high cost-effectiveness.
5, Key Questions and Answers
Q: Why do new devices also classify screws as vulnerable parts?
A: During the operation of a co rotating twin-screw extruder, the material contact surface will inevitably experience progressive wear. Using contact parts such as screw components and barrel liners as replaceable consumables can protect core components such as gearboxes and core shafts, and extend the lifespan of the entire machine.
Q: How to estimate the lifespan of plastic extruder accessories when trying to make new materials for the first time?
A: First, make a small batch sample and observe the fluctuation of melt pressure, current rise, and black spots on the product. COLOWE can provide a preliminary lifespan range based on the formula composition and correct it through actual wear measurements.
Q: Is environmentally friendly recycled material necessarily more damaging to the screw?
A: Not necessarily. Recycled materials that have been well sorted and filtered have a wear rate close to that of new materials; The ones that truly accelerate wear are sand and gravel, metal shavings, and unmelted impurities. Strengthening pre-treatment and selecting wear-resistant mechanical components can significantly reduce wear and tear.
Conclusion
The wear of the parts in contact with materials is a physical law, not an equipment defect. Understanding the wear mechanisms of different materials and selecting the right materials for co rotating twin-screw extruders and mechanical components is essential to ensure that vulnerable parts can be easily and cost effectively replaced. If you need to calculate the service life and spare parts plan of twin-screw extruder accessories based on your formula, you can contact Nanjing Kelongwell Chemical Machinery Co., Ltd.
