LESUN Releases New Whitepaper, Advocating a Processing-Condition-Based Approach to Twin-Screw Extruder Screw Material Selection

Why Screw Material Selection Should Start from Processing Conditions, Not Material Grades

In twin-screw extrusion, screw elements are among the most critical components influencing production stability and service life. However, when selecting replacement screw elements, many companies still evaluate performance primarily based on material grades — for example, by specifying higher hardness or more advanced steel grades. In practice, screw service life is not determined by material grade alone.

The same material can deliver significantly different service-life performance under different processing conditions. For example, standard polypropylene compounding and glass-fiber-reinforced polypropylene processing may use the same base polymer, but they create completely different wear conditions. Similarly, unfilled engineering plastics and highly reinforced grades such as PA GF30 or PA GF50 impose very different requirements on screw materials.

The actual performance of screw elements depends on the complete processing environment, including:

· Polymer system and processing temperature;

· Fillers, reinforcements, and functional additives;

· Wear and corrosion risks;

· Torque level and mechanical loading;

· Production continuity and the impact of downtime.

Therefore, scientific screw material selection is not about choosing the most expensive material. It is about selecting the material system that best matches the actual processing conditions.

Why Can the Same Polymer Result in Completely Different Screw Lifetimes?

In the plastic compounding industry, the base polymer represents only one part of the overall processing environment. Glass fiber, carbon fiber, mineral fillers, flame retardants, pigments, and other functional additives can significantly change the wear and corrosion conditions inside the extruder.

For example:

In general polyolefin processing, screw elements mainly experience conventional mechanical wear, and nitrided steel can often provide a reliable and cost-effective solution. However, when processing highly filled masterbatches, glass-fiber-reinforced compounds, or high-performance engineering plastics, large amounts of hard particles continuously interact with the screw surface. Under these conditions, higher-performance materials such as high-speed tool steel or powder metallurgy materials can provide significantly improved wear resistance and longer service intervals.

Selecting screw materials only according to polymer type may result in either insufficient performance or unnecessary material costs.

The Key to Material Selection: Understanding Failure Mechanisms

Different processing environments create different requirements for screw materials.

Applications involving severe abrasive wear require high wear resistance and excellent dimensional stability. High-temperature processing requires materials that can maintain hardness, strength, and structural stability during long-term operation. Processing systems involving aggressive additives or chemically reactive formulations require improved corrosion resistance. High-torque continuous production requires materials that combine wear resistance with sufficient toughness and fatigue resistance.

Therefore, screw material selection is fundamentally an engineering matching process:

Understand the processing environment → Identify the dominant failure mechanism → Select the appropriate material system → Evaluate long-term production value.

Why Material Upgrades Do Not Always Mean Higher Costs

Many companies focus primarily on the purchase price of screw elements. However, in continuous production environments, the actual cost is determined by the complete service lifecycle. The initial purchase price represents only one part of the total cost. Wear-related issues may lead to:

· Reduced extrusion efficiency;

· Process instability and product quality fluctuations;

· More frequent maintenance;

· Unplanned production downtime.

For high-value materials, continuous production lines, and demanding processing environments, upgrading to a higher-performance screw material may not increase overall operating costs. Instead, it can reduce production risks and improve long-term manufacturing efficiency. This is why more manufacturers are evaluating screw materials based on Total Cost of Ownership (TCO) rather than initial purchase price alone.

Download the Screw Material Selection Whitepaper for Twin-Screw Extruders

To help engineers and technical teams better understand screw material selection, LESUN has developed the Screw Material Selection Whitepaper for Twin-Screw Extruders. This whitepaper explains screw material selection from an application-oriented perspective, covering:

· Material requirements for different plastic processing environments;

· Key failure mechanisms including wear, corrosion, high temperature, and fatigue;

· Application characteristics of nitrided steel, high-speed tool steel, and powder metallurgy materials;

· When screw material upgrades are necessary;

· How to evaluate material value from a Total Cost of Ownership perspective.

Whether you are optimizing an existing production line or developing new material formulations, this whitepaper provides a practical framework for selecting screw materials based on actual processing conditions. Download the complete Screw Material Selection Whitepaper and learn how to select the right screw material for your extrusion applications.