What is a stenter machine? Parts, Functions, Working Process and Principle

The stenter machine, often the most expensive and crucial in fabric drying and finishing, is essential in textile manufacturing. Known as a ‘tenter’ in the woollen industry, the stenter’s primary purpose is to stretch or stenter fabrics. It plays a vital role in achieving precise length and width dimensions, heat setting, applying finishing chemicals, and adjusting shade variation.

Main Functions

• Stretching Fabric: The primary function of the stenter is to stretch the fabric widthwise and ensure uniform width.
• Heat Setting: It allows for heat setting of fabrics, crucial for maintaining fabric quality and characteristics.
• Finishing Chemical Application: The machine is used for the application of various finishing chemicals to enhance fabric properties.

Components and Working Process

• Driven Chains: The machine consists of two endless auto-lubricated driven chains, typically 40 to 60 meters long.
• Pins or Clips: These chains carry pins or clips to hold the fabric edges, allowing for precise stretching and handling.
• Hot-air Chambers: The fabric passes through several hot-air chambers (usually 3–5), each about 3 meters long. Hot air is directed onto the fabric from above and below.
• Overfeeding Provision: The stenter has an overfeeding feature to allow the required shrinkage during heat setting while simultaneously increasing the width.
• Speed Range: Stenter speed can vary from 10 m/min for heavyweight fabrics to 100 m/min for lightweight fabrics, depending on the process requirements.

Processes in Stenter

• Drying
• Heat setting
• Weft straightening
• Curing after finishes application

Control Parameters in Modern Stenter Modern stenters are equipped with controllers to monitor and adjust various parameters:

• Chamber temperatures
• Moisture retention
• Stretch/shrinkage (overfeed)
• Fabric width and weight
• Padder pressures
• Exhaust humidity

Types of Stenter Machines

Stenter machines, pivotal in textile manufacturing for their ability to transport and precisely control fabric width, come primarily in two types: pin stenters and clip stenters. The choice between these two depends on the method of holding the fabric onto the chains and the specific requirements of the fabric being processed.

1. Clip Stenters:
   • Utilize clips in two sections (upper and lower) to grip the fabric edges.
   • The upper jaw descends to grip the fabric at the entry and opens to release it at the delivery point.
   • Suited for fabrics with specific edges like selvedges and mainly used for woven fabrics.
2. Pin Stenters:
   • Feature pins about 5 mm long, mounted in rows on the base plate.
   • Designed to minimize direct fabric contact with the hot base plate.
   • Pin stenters are more common and can leave pinholes in selvedges, which are generally acceptable.

The stenter machine is indispensable in textile manufacturing for its versatility and precision in fabric handling. Its ability to control fabric dimensions, apply finishing chemicals, and perform heat setting makes it a cornerstone in the textile industry. Whether using clip or pin stenters, this machinery remains crucial for producing high-quality textile products.

1. Clip Stenters

• Mechanism: Clip stenters employ a two-section clip mechanism, comprising upper and lower sections. The upper section can be either open or closed.
• Operation: At the fabric’s entry point, the upper jaw of the clip descends to grip the fabric’s edge firmly. Upon reaching the delivery point, this jaw opens up to release the fabric.
• Fabric Suitability: Clip stenters are more suited for fabrics with a specific edge, typically a selvedge, and are generally used for woven fabrics.
• Advantage: They are preferred when there’s a need to avoid pin marks on the fabric, as clip stenters leave no pin marks on the selvedges.

2. Pin Stenters

• Mechanism: Pin stenters feature pins, about 5 mm long, mounted in two rows along the base plate. The density of these pins is around 3–4 pins per centimeter.
• Design Considerations: The pins are designed to be thicker near the base, which helps in preventing the fabric from directly contacting the hot base plate, thereby reducing the risk of damage or marking.
• Fabric Suitability: Pin stenters are more commonly used due to their versatility and are acceptable for a broader range of fabrics.
• Selvedge Marks: While clip stenters avoid leaving marks on the selvedges, pin stenters can leave pinholes. However, these pinholes in the selvedges are generally acceptable to customers.

Conclusion The choice between pin and clip stenters in textile manufacturing largely depends on the type of fabric being processed and the end-use requirements. Pin stenters offer greater versatility and are more commonly used, but clip stenters provide the advantage of leaving no marks on the selvedges, making them ideal for certain types of woven fabrics. Both systems play a crucial role in ensuring precise width control and quality finishing in fabric production.

Functions of a Stenter Machine in Textile Industry

The stenter machine, an indispensable apparatus in the textile industry, is known for its multifaceted capabilities. Its primary function is drying, but it extends far beyond just removing moisture. Here are the key functions it performs:

1. Mechanical Finishing: The stenter imparts a specific mechanical finish to fabrics, affecting their appearance and feel. This process, often referred to as the ‘stenter finish,’ enhances the aesthetic and tactile qualities of the fabric.
2. Heat Setting: Essential for fabrics like lycra, synthetic, and blended materials, the stenter machine performs heat setting. This process stabilizes the size and shape of the fabric, making it more resilient to subsequent processing and use.
3. Width Control: One of the unique capabilities of the stenter is controlling and adjusting the width of the fabric during drying. This ensures that the fabric meets precise dimensional specifications.
4. Finishing Agent Application: The stenter applies various finishing agents to the fabric, enhancing its properties and performance. This includes treatments for color, texture, and other functional attributes.
5. Control of Knit Loop: For knit fabrics, the stenter plays a crucial role in controlling the loop size and structure, impacting the fabric’s final texture and elasticity.
6. Moisture Control: Maintaining optimal moisture content in the fabric is another crucial function of the stenter, ensuring the fabric doesn’t become too dry or retain excessive moisture.
7. Control of Spirality: The stenter helps in controlling spirality in fabrics, which is essential to maintain the fabric’s shape and prevent twisting during subsequent processes or use.
8. GSM Control: GSM (Grams per Square Meter), an indicator of fabric weight, is controlled and standardized in the stentering process to meet specific requirements.
9. Drying: The stenter efficiently dries fabrics, a fundamental part of the textile finishing process.
10. Shrinkage Control: It plays a vital role in controlling the shrinkage properties of the fabric, ensuring dimensional stability after the manufacturing process.
11. Curing Treatments: The machine is used for curing treatments for specialized finishes like resin application and water repellent treatments, enhancing the fabric’s functional properties.

Components and Main Parts of a Stenter Machine

The stenter machine, integral to the textile industry, consists of various components and parts, each playing a critical role in its operation. Here’s a detailed overview:

Components of Stenter Machine:

1. Paders: These are used for applying chemicals to the fabric before it enters the main part of the machine.
2. Weft Straightener (Mahlo): Ensures the fabric is aligned correctly and straight.
3. Burners (10): Provide the necessary heat for drying and processing the fabric.
4. Heat Recovery: A system to reclaim and reuse heat, improving energy efficiency.
5. Attraction Rollers: Help in pulling the fabric through the machine.
6. Circulating Fans (10,8): Circulate air within the machine for uniform drying.
7. Exhaust Fans (2): Remove excess heat and moisture from the machine.
8. Winder (2): Used for rolling the processed fabric.
9. Clips and Pins: Hold the fabric in place while it moves through the machine.
10. I.R (Infrared Radiation): Provides additional heating.
11. Cooling Drums (2): Cool the fabric after processing.

Main Parts of Stenter Machine:

1. Feed Zone:
   • Centering device: Aligns the fabric correctly as it enters the machine.
2. Chemical Padding Zone:
   • Squeezing Roller: Removes excess chemical solution.
   • Chemical Tray: Holds the chemical solutions used on the fabric.
3. Bowing Control Zone:
   • Bowing Roller: Corrects fabric bowing.
   • Sensor: Monitors and adjusts the fabric feed.
   • Uncurling Roller: Removes curls from the fabric edges.
4. Chain Entry Zone:
   • Uncurling Device: Straightens the fabric before it attaches to the chain.
   • Brush Roller: Ensures the fabric attaches securely to the pins or clips.
5. Drying Zone:
   • Gas Rotamatic Burner (10): Provides the heat for drying.
6. Cooling Zone: Cools down the fabric after heat treatment.
7. Delivery Zone: Where the processed fabric exits the machine.

Utility Requirements: The stenter machine typically requires gas, electricity, compressed air, and steam for its operation.

Parameter Settings for Different Fabrics: Depending on the type of fabric being processed, parameters like GSM (Grams per Square Meter), fabric width (R, F, B), temperature, speed, and overfeed percentage are adjusted to achieve the desired quality and finish.

Heating Arrangement: In this particular stenter machine setup, there are seven heating chambers, each equipped with two burners. The maximum temperature can reach up to 250°C, but operating temperatures vary based on fabric requirements.

Heating Arrangement

Parameters used for different types of fabric:

Working Principle of a Stenter Machine

The stenter machine plays a crucial role in the textile industry, particularly in the finishing and drying processes. It is designed to stretch the fabric to its desired width and ensure uniformity in the final product. Here’s an overview of its working principle and process:

Feed Mechanism and Fabric Treatment

1. Fabric Entry: Fabric enters the stenter machine from a batcher or a trolley.
2. Guidance and Tensioning: The fabric is guided through rollers and tensioners to maintain consistent tension.
3. Solution Tank: Fabric passes through a solution tank containing various finishing auxiliaries.
4. Padding and Squeezing: After being soaked in the solution, the fabric is squeezed by rollers to achieve the desired moisture level.

Weft Straightening and Application of Finishes 5. Feeding Unit: Fabric is collected from the batcher/trolley to the scray.

6. Padders Application: Finishes are applied, and sometimes shade variation is corrected.
7. Weft Straightener (Mahlo): This device sets the bow and weave of the fabric.

Stretching and Stentering 8. Clips and Pins: Fabric is gripped by clips and pins attached to endless chains, which stretch the fabric widthwise.

9. Sensor Control: Sensors detect and correct faults in the weft.
10. Chambers with Burners: The machine typically contains 8 to 10 chambers, each with a burner. Filters separate dust from air.
11. Air Circulation and Exhaust: Circulating fans blow air from the base, and exhaust fans remove hot air from the chambers.

Final Processing and Control 12. Attraction Rollers: These rollers stretch the warp yarns.

13. Width Adjustment: The width of the fabric can be increased by 1.5-2 inches.
14. Speed and Temperature Control: The machine operates at speeds between 7-150 m/min. The fabric runs 3 meters in each chamber, with temperature settings adjusted according to fabric type (e.g., PC at 210°C, Cotton at 110-130°C, Post-dyeing at 160-170°C, and Post-print at 130-140°C).

Conclusion The stenter machine’s ability to precisely control fabric width, apply finishing treatments, and ensure uniform drying and heat setting makes it indispensable in textile production. Its complex mechanism, involving various rollers, chambers, and sensors, ensures the highest quality in fabric processing.

Controlling Parameters of a Stenter Machine

The stenter machine, a critical component in textile finishing, requires precise control of various parameters to ensure optimal fabric processing. Below are the key controlling parameters along with the methods of checking and necessary actions:

1. Nip Pressure
   • Checking: Examine liquor pick-up for uniformity across the width and length.
   • Action: Adjust pressure (pneumatically or hydrolytically) and check the surface of the padding mangle.
2. Bow and Heading (Skew) Controllers
   • Checking: Regular visual inspection to ensure no bow or heading in the fabric.
   • Action: Check synchronisation of photocell, heading, and bowing rollers. Verify the hardness and alignment of bowing rollers.
3. Chamber Temperature
   • Checking: Use a dial or digital thermometer.
   • Action: Regulate oil supply in the radiator and ensure proper functioning of solenoid valve and digital controls.
4. Dwell Time
   • Checking: Use a stopwatch during the finishing process.
   • Action: Regulate dwell time based on material quality and process requirements.
5. Overfeeding
   • Checking: Measure cloth length before and after heat setting to check % overfeed.
   • Action: Assess the required optimum overfeed for specific fabric types.
6. Underfeeding
   • Checking: Ensure the feed speed to the stenter is less than the output.
   • Action: Adjust to stretch the length of the fabric.
7. Expanders and Uncurlers
   • Checking: Verify the working condition of uncurlers.
   • Action: Check for smooth operation and revolution of expanders and uncurlers.
8. Blower
   • Checking: Ensure proper functioning during the finishing process.
   • Action: Clean air filters and check fan direction for optimal air circulation.
9. Width of the Fabric
   • Checking: Measure at the delivery end.
   • Action: Ensure proper working of the width adjusting shaft.
10. Leakages of Thermic Fluid
    • Checking: Look for brown spots on the fabric.
    • Action: Investigate and rectify any leakages.
11. Concentration of Chemicals
    • Checking: List chemicals and their concentrations.
    • Action: Maintain optimum concentrations to avoid issues like chalk marks.
12. Temperature and Viscosity of Finishing Bath
    • Checking: Keep temperature and viscosity constant.
    • Action: Regular monitoring and adjustments as needed.
13. Drying Efficiency
    • Checking: Use a conductometer with transducers.
    • Action: Aim for drying efficiency of 95–98% to avoid over-drying.
14. Temperature of Thermic Fluid Oil
    • Checking: Frequent checks with a digital thermometer.
    • Action: Regulate thermic fluid circulation for optimum temperature.
15. Clips and Pins
    • Checking: Random inspection before processing.
    • Action: Ensure proper functioning of pins and clips.

Comparison of Stenter 10F, Stenter 8F, and Knit Stenter Machines

Stenter 10F

• Flames: Features 10 flames (10F) in the stenter.
• Clips Usage: Utilizes 10F clips for stretching the fabric.
• Disadvantages: Leads to holes appearing on the selvedge due to clips, and may result in uneven dyeing.
• Fabric Handling: Generally used for a range of fabrics but with the mentioned limitations.

Stenter 8F

• Flames: Equipped with 8 flames.
• Versatility: Similar to 10F stenter in its basic function but offers additional capabilities.
• Dyeing Capabilities: Capable of dyeing, with an I.R system included. Suitable for pigment dyeing, heat setting, and controlling skew and bow problems.
• Advantage: Light shades can be dyed without leaving clip marks.

Knit Stenter

• Fabric Specialization: Specifically designed for knit fabric processing.
• Functions: Used for weft straightening, heat setting, dyeing, applying light shades, print, and knit finishing chemicals.
• Pin and Clip System: Equipped with pins alongside clips.
• Additional Features: Includes flat rollers, a brush for holding the pin, an L-guide for knit fabric, and a selvedge cutter with suction.

Specification of a Stenter Machine (Example: Bruckner)

• Brand Name: Bruckner
• Serial No: 72276-0463
• Origin: Germany
• Year of Manufacture: 1995
• Speed Range: 15-30 m/min
• Temperature Range: 50-250°C
• Utilities Used: Electricity, Gas, Compressed Air, Steam
• Production Capacity: 8 tons/day
• Number of Chambers: 3
• Maximum Fabric Width: 102 inches
• Minimum Fabric Width: 30 inches
• Steam Pressure: 2 bar
• Air Pressure: 10 bar
• Application: Open tube fabric
• Number of Ratamatic Burners: 6
• Extra Attachment: Mahlo weft straightener
• Machine Parts: Burner, Nozzle, Exhaust Air Fan, Overfeed Roller, Suction Fan, Chain Arrangement

Conclusion Each type of stenter machine offers unique features and functionalities tailored to specific fabric types and processing needs. The Stenter 10F and 8F are suitable for a variety of fabrics, with the 8F providing additional dyeing capabilities and better handling of light shades. The Knit Stenter is specifically designed for knit fabrics, offering specialized features for this fabric type. The example specification of the Bruckner stenter machine highlights the capabilities and features of a typical high-end stenter machine in the industry.

These sources are valuable for anyone looking to delve deeper into the technical aspects and operational principles of textile finishing, specifically concerning stenter machines and related processes in the textile industry.

1. “Principles of Textile Finishing” by Asim Kumar Roy Choudhury: An extensive resource covering the fundamental principles and methodologies involved in textile finishing.
2. “Process Control in Textile Manufacturing” Edited by Abhijit Majumdar, Apurba Das, R. Alagirusamy, and V. K. Kothari: A comprehensive guide focusing on process control aspects in textile manufacturing, offering insights into modern practices and technologies.
3. “Handbook of Value Addition Processes for Fabrics” by B. Purushothama: This handbook provides a detailed look at various processes that add value to fabrics, enhancing their appeal and functionality.

Additional Resources:

• “Dryer Machine in Textile | Drying Techniques in Textile Industry”: An article focusing on different drying methods and equipment used in the textile industry, including their impact on fabric quality.
• “Knit Fabric Turning Process | Features of Fabric Turning Machine”: A detailed exploration of the knit fabric turning process and the features of machines used for this purpose.
• “Sueding Finishing Process: Mechanism, Application and Benefits”: This resource delves into the sueding process, its mechanisms, applications in textile finishing, and the benefits it offers.
• “Methods of Heat Setting in Textile Industry”: A comparative analysis of various heat setting methods employed in the textile industry, discussing their applications and efficiency.
• “Comparative Study between Open Line & Tube Line Finishing Process”: This study compares two popular finishing processes in the textile industry, highlighting their differences and respective advantages.
• “Causes and Remedies of Spirality in Knitted Fabric”: An insightful piece on the common issue of spirality in knitted fabrics, including its causes and potential remedies.
• “Spirality Correction System (SCS) for Knitted Fabrics”: An exploration of systems and techniques used to correct spirality in knitted fabrics.
• “How to Control Fabric Shrinkage, GSM and Dia in Compactor Machine”: This article provides guidance on controlling key fabric parameters like shrinkage, GSM (Grams per Square Meter), and diameter during the compaction process.
• “How to Measure Fabric Shrinkage in Textile and Apparel Industry”: Offers techniques and tools for accurately measuring fabric shrinkage, a crucial quality parameter in the textile and apparel industry.

These references and additional resources provide a thorough understanding of various aspects of textile processing and finishing, offering valuable insights for industry professionals and students alike.