Powder filling systems film unwinding and film tension : overview

1. Introduction

What is a film unwinder ?

The packaging material used in bulk powder filling operation with VFFS or HFFS fillers is delivered in rolls (or reels), that usually make several hundred meters. In order to be able to use this film, it must be unrolled. It is the operation done in the film unwinding section (or unwinder) of a form, film and seal (FFS) filling machine.

The unwinding has also as a function to ensure a proper tension of the film so that it can be used to form a proper bag. The film tension is very important, if the tension is too low, the shape of the packaging will not be satisfactory, if it is too high there is a risk of film breakage when the packing machine is pulling it.

2. Film unwinding

2.1 Film unwinding components

A filling machine is made of the following sections :

• Film rollstock
• (Power unwind)
• Film tension / dancer
• (Printing)

Figure 1 : Components of a film unwinding section of a bulk powder filling machine (form fill seal)

2.2 Film unwinding principle of operation

STEP 1 : Rollstock handling

The packaging material, delivered in rollstocks (or reels), has 1st to be mounted on a shaft at the back of the machine. It allows to rotate it automatically when the machine is pulling the film to use it.

In some packaging machines, the pulling of the film is not enough and a powered wheel is added to help rotate the rollstock, especially if it is very heavy.

STEP 2 : Tensionning

The film must have the right tension to be used further down the process. To enable this, a tensioning arm is pushing on the film and the film is tensioned further thanks to dancers (rollers). The film tension is critical for having a good packaging and for the machine to perform optimally without stoppages.

STEP 3 : Printing

An ink or laser printing machine can be added once the film is well tensioned in order, for example, to print a code on the packaging material.

2.3 Film unwind problem troubleshooting

It may happen that the packing machine is not operating well, with frequent stoppages, due to an issue with the film unwind operation. Here is a list of common problems and possible remedy :

Issue observed	Cause and possible action
The reel is not rotating on the unwinder	Too heavy, would need a powered wheel Too much friction Splicing table is clamped Film unwind brake is too much
Film tension is not correct at exit of unwind	Tension roll and dancer not properly set Issue with the packaging material Film unwind brake to fine tune

3. Best Practices for unwinder optimization

Proper setup and calibration of unwinders are very important to ensuring optimal performance and reliability in filling machine operations. Here are some best practices to consider:

• Proper Installation: Begin by ensuring the unwinder is installed correctly according to manufacturer specifications. This includes securely mounting the roll holder or shaft, aligning it with the feeding mechanism of the filling machine, and verifying that all connections are tight and properly fitted.

• Calibration of Tension Control: Calibration of the tension control system is crucial for maintaining consistent tension levels in the packaging material. This involves adjusting tension settings based on the type and properties of the material being used. Conduct thorough testing to ensure that the tension is uniform throughout the unwinding process.

• Regular Maintenance: Implement a proactive maintenance schedule for the unwinder to prevent issues and prolong its lifespan. This may include routine inspections, cleaning of components, lubrication of moving parts, and replacement of worn-out or damaged elements. Adhering to a maintenance regimen can mitigate the risk of unexpected downtime and costly repairs.

• Monitoring and Adjustment: Utilize monitoring devices and sensors integrated into the unwinder to track parameters such as tension levels, material speed, and any deviations from normal operation. Establish protocols for operators to regularly monitor these metrics and promptly address any anomalies or alerts that arise. Additionally, provide training to operators on how to make necessary adjustments to maintain optimal performance.

• Material Handling Procedures: Develop standardized procedures for handling and loading packaging materials onto the unwinder. Ensure that operators are trained to handle materials with care to prevent damage or contamination. Proper material handling practices can minimize waste, reduce the risk of defects, and contribute to overall efficiency.

• Documentation and Record-Keeping: Maintain detailed records of maintenance activities, calibration adjustments, and any troubleshooting or repairs conducted on the unwinder. This documentation serves as a valuable reference for tracking performance trends, identifying recurring issues, and informing future maintenance tasks.

4. Issues and remedies for unwinder operation

Despite their critical role in filling machine operations, unwinders are not without challenges. Addressing these challenges effectively requires a thorough understanding of the underlying issues and the implementation of appropriate solutions. Here are some common challenges faced with unwinders and strategies to overcome them:

• Material Compatibility: One of the primary challenges with unwinders is handling a diverse range of packaging materials, each with unique properties and characteristics. Different materials may have varying degrees of elasticity, thickness, and surface friction, which can affect the unwinding process. To mitigate this challenge, engineers can implement unwinders with adjustable tension control mechanisms and material handling features tailored to specific material types. Additionally, conducting material compatibility tests and optimizing unwinder settings accordingly can help ensure smooth and consistent material feeding.

• Monitoring and Maintenance: Unwinders require regular monitoring and maintenance to prevent issues such as material jams, breakages, or deviations in tension. However, inadequate monitoring and maintenance practices can lead to unexpected downtime and production delays. To address this challenge, food production facilities should establish comprehensive maintenance schedules for unwinders, including routine inspections, cleaning, and lubrication of components. Additionally, integrating advanced monitoring systems with real-time alerts can provide early detection of potential issues, allowing operators to take proactive measures to prevent disruptions.

• Tension Control: Maintaining optimal tension levels in the packaging material is essential for ensuring uniformity and preventing issues such as wrinkling, tearing, or misalignment. However, achieving consistent tension control can be challenging, especially when working with flexible or stretchable materials. Engineers can address this challenge by implementing unwinders equipped with advanced tension control systems, such as pneumatic or servo-driven mechanisms, capable of precise adjustment and monitoring. Additionally, conducting regular calibration of tension settings and providing operator training on proper tension control techniques can help optimize unwinder performance.