Traction System
Essential component in the extruder line for precise film handling and processing
Overview of the Traction System in Extruder Line
In the modern extruder line, the traction system plays a critical role in transforming molten plastic into high-quality films. The process begins as the shaped film tube is drawn upward at a constant speed by a pair of traction rollers mounted on the traction frame. This precisely controlled movement ensures uniform thickness and proper formation of the film throughout the extruder line.
As the film travels through the extruder line, it passes through a flattening board assembly positioned below the traction rollers on the traction frame. This specialized component, known as the herringbone board, serves multiple purposes in preparing the film for its final form. After being flattened, the film enters the nip of the traction rollers where it is compressed, forming a continuous double-layer film that proceeds to the winding device.
A complete traction system within an extruder line typically consists of several key components: the traction frame, herringbone board, traction device drive system, and a pair of traction rollers. Each element works in harmony to ensure the proper formation, handling, and processing of the film as it moves through the extruder line. This page focuses specifically on the herringbone board and traction device, two critical elements that significantly impact the quality of the final product in any extruder line.
1. Herringbone Board
The herringbone board is a vital component in the extruder line, performing three essential functions that contribute to the quality and consistency of the film product. First and foremost, it stabilizes the film tube as it emerges from the die, preventing irregularities that could compromise the final product. This stabilization is crucial in maintaining the integrity of the extrusion process within the extruder line.
Secondly, the herringbone board gradually transforms the cylindrical film into a flat sheet through a carefully designed folding process. This transformation is essential for converting the tube into a usable flat film format within the extruder line. Finally, the herringbone board provides additional cooling to the film, ensuring proper solidification and maintaining dimensional stability as the product moves through the extruder line.
Several types of herringbone boards are commonly utilized in the extruder line, each with its own set of advantages and applications. The most prevalent designs include the guide roller type, polished hardwood夹板式, and polished stainless steel夹板式. These different configurations offer varying levels of performance in terms of friction, cooling efficiency, and durability within the extruder line.
The guide roller type herringbone board, composed of copper or steel rollers, minimizes friction against the film surface while providing efficient heat dissipation – both important factors in maintaining film quality in the extruder line. However, this design presents certain challenges, including the potential for film wrinkling due to internal air pressure causing the film to bulge between rollers. Additionally, the guide roller configuration features a more complex structure and higher manufacturing cost compared to other options in the extruder line.
Figure 3-18: Herringbone Board Types
Guide roller type (left) and夹板式 (right) herringbone boards used in modern extruder line systems
Hardwood夹板式 herringbone boards, while cost-effective, present limitations in terms of heat dissipation – a critical factor in maintaining optimal film properties in the extruder line. In contrast, stainless steel夹板式 designs offer superior thermal performance, making them better suited for high-speed or high-temperature extruder line operations.
To further enhance cooling efficiency in the extruder line, metal夹板式 herringbone boards can be equipped with water cooling systems. This active cooling mechanism allows for precise temperature control, ensuring the film maintains proper characteristics throughout the extrusion process. The integration of such cooling systems represents an important advancement in extruder line technology, enabling higher production speeds and improved film quality.
The selection of an appropriate herringbone board design depends on various factors in the extruder line, including the type of plastic being processed, desired production speed, and quality requirements. Each design offers distinct advantages that must be carefully considered to optimize the extruder line performance for specific applications.
Maintenance of the herringbone board is also a critical aspect of extruder line upkeep. Regular inspection for wear, proper alignment checks, and cleaning are essential to ensure consistent performance. In the case of water-cooled systems, checking for leaks and ensuring proper water flow are additional maintenance requirements that contribute to the overall efficiency of the extruder line.
2. Traction Device
The traction device serves as a critical component in the extruder line, responsible for compressing the flattened film from the herringbone board and conveying it to the winding unit. This device plays a pivotal role in maintaining the integrity of the extrusion process by preventing air leakage from the bubble, ensuring consistent bubble shape and dimensions throughout the extruder line.
Beyond simple conveyance, the traction device in the extruder line provides controlled stretching of the film, establishing a precise ratio between the extrusion speed and traction speed – known as the draw ratio. This ratio directly influences the longitudinal strength of the plastic film, making it a key parameter in determining final product quality in the extruder line. By adjusting the traction speed, operators can precisely control the thickness of the film, ensuring it meets strict dimensional specifications.
A typical traction roller configuration in the extruder line consists of one rubber roller (or a steel roller covered with rubber) and one chrome-plated steel roller. The chrome-plated steel roller functions as the drive roller, connected to a continuously variable speed drive system that allows for precise speed adjustments in the extruder line. This variable speed capability is essential for fine-tuning the draw ratio and accommodating different film thickness requirements.
Traction Roller Assembly
Precision-engineered traction rollers ensuring proper film handling in the extruder line
Alignment and Pressure Considerations
Proper alignment within the extruder line is crucial for optimal performance of the traction system. The center of the contact line between the traction rollers must be precisely aligned with both the center of the herringbone board and the center of the die head. This alignment ensures stable, non-skewed movement of the film tube through the extruder line, minimizing the risk of wrinkling caused by uneven distances from different points on the tube to the traction rollers.
The application of appropriate pressure between the two traction rollers is another critical factor in extruder line performance. This pressure must be sufficient to ensure proper traction and stretching of the film while preventing air leakage from the bubble. In most extruder line configurations, this pressure is applied using springs or pneumatic cylinders, with adjustment screws allowing for precise control of compression to accommodate films of varying thicknesses.
Optimizing roller pressure is a balancing act in the extruder line. While sufficient pressure is necessary for proper film handling and to prevent air leakage, excessive pressure can cause problems. High pressure leads to greater deformation of the rubber roller, particularly in the center, resulting in uneven compression where the edges of the film may be over-compressed while the center receives insufficient pressure. Additionally, lower pressure settings help reduce the risk of edge cracking, especially in thicker films where the folded edges are more susceptible to damage in the extruder line.
Key Insight for Extruder Line Optimization
The pressure between traction rollers should be the minimum necessary to achieve proper film traction and prevent air leakage. This approach minimizes rubber roller deformation, ensures uniform compression across the film width, and reduces the likelihood of edge damage – all contributing to higher quality output and extended component life in the extruder line.
Cooling and Material Specifications
To enhance cooling efficiency in the extruder line, the traction rollers (specifically the smooth steel roller) can be equipped with internal water cooling systems. This additional cooling stage ensures the film is sufficiently cooled before winding, reducing the risk of dimensional changes or surface defects in the final product.
The construction of the traction rollers in the extruder line is carefully engineered to meet the demands of film processing. The smooth roller is typically manufactured from seamless steel tubing, finished with a chrome plating 0.03~0.05mm thick, followed by precision polishing to achieve a surface roughness of Ra≤0.80μm. This smooth surface finish is essential for preventing film damage and ensuring uniform contact pressure in the extruder line.
The rubber roller in the extruder line is equally critical, with the hardness of the rubber layer carefully specified to ensure optimal performance. The rubber should have a hardness of 60~70 Shore A. Hardness values above this range result in insufficient elasticity, while values below this range lead to excessive wear. Over time, the rubber surface will naturally wear, potentially developing a saddle-like shape. When this occurs, the roller can be reconditioned through resurfacing or grinding, extending its service life in the extruder line.
Maintenance and Performance Monitoring
Regular maintenance of the traction device is essential for maintaining consistent performance in the extruder line. This includes periodic inspection of roller alignment, checking for wear on both the rubber and chrome-plated surfaces, and verifying proper pressure settings. Operators should also monitor the temperature of cooled rollers to ensure the cooling system is functioning effectively in the extruder line.
Performance monitoring in the extruder line should include regular checks of film thickness uniformity, which can indicate traction system issues. Variations in thickness may signal improper roller pressure, misalignment, or worn components. By addressing these issues promptly, operators can maintain product quality and minimize waste in the extruder line.
In conclusion, the traction device represents a critical component in the extruder line, directly influencing film quality, production efficiency, and overall process stability. Through careful design, precise alignment, appropriate pressure settings, and regular maintenance, the traction system can consistently deliver high-quality films meeting the demanding specifications of modern manufacturing in the extruder line.
Conclusion
The traction system, comprising the herringbone board and traction device, represents a critical component in the modern extruder line, directly impacting film quality, production efficiency, and process stability. By precisely controlling the transformation of the film tube from its cylindrical form to a flat sheet, these components ensure consistent thickness, proper cooling, and optimal mechanical properties in the final product. Understanding the design principles, operational parameters, and maintenance requirements of these systems is essential for maximizing the performance of any extruder line.