How to make a good packing tension for the orbital stretch wrapper

Mastering Packing Tension: A Deep Dive into Orbital Stretch Wrapper Performance

In the demanding world of logistics and manufacturing, ensuring product integrity during transit is paramount. Damaged goods not only lead to financial losses but also erode customer trust. A critical factor in achieving secure and stable loads, especially for long or unconventional profiles, is the correct application of stretch film using an orbital stretch wrapper. While these machines offer significant advantages in speed and efficiency, mastering the packing tension is key to unlocking their full potential. This guide delves into the technical nuances, operational best practices, and critical components involved in achieving optimal tension for superior load containment.

1. Understanding the Orbital Stretch Wrapper: Beyond the Basics

Unlike traditional turntable wrappers that rotate the pallet, an orbital (or horizontal) stretch wrapper passes a ring carrying the stretch film roll around a stationary load. This design makes them ideal for long, heavy, or unstable products like timber, pipes, extrusions, doors, windows, and bundled materials.

Key Design & Structural Aspects:

• Wrapping Ring: The core component, available in various diameters to accommodate different product cross-sections. It houses the film carriage and rotates at high speeds.
• Film Carriage: Mounted on the ring, this holds the stretch film roll and incorporates the pre-stretch and tension control mechanisms.
• Conveyor System: Infeed and outfeed conveyors (often powered rollers or belts) transport the product smoothly through the wrapping ring.
• Clamping & Cutting Unit: Automated systems securely clamp the film at the start and cut it cleanly at the end of the cycle.
• Control System (PLC/HMI): The brain of the operation, allowing operators to set parameters like ring speed, conveyor speed, number of wraps, pre-stretch percentage, and crucially, wrapping tension.

2. The Critical Role of Tension: More Than Just Tightness

Achieving the right packing tension is a balancing act. It’s not simply about wrapping as tightly as possible. Optimal tension ensures:

• Load Stability: Prevents shifting, vibration damage, and collapse during handling and shipping.
• Film Economy: Utilizes the stretch film’s properties effectively, maximizing yield and minimizing material cost per load. Properly tensioned film with adequate pre-stretch covers more area.
• Product Protection: Shields goods from dust, moisture, and minor impacts without crushing or damaging sensitive items.
• Containment Force: This is the residual force holding the load together after the film has been applied and has attempted to relax. It’s the true measure of wrapping effectiveness, directly influenced by the initial wrapping tension and pre-stretch.

3. Key Factors Influencing Optimal Tension Settings

Setting the ideal tension isn’t a one-size-fits-all process. Several variables must be considered:

• Load Characteristics:
  • Weight & Density: Heavier loads generally require higher containment force.
  • Shape & Uniformity: Irregular shapes may need specific wrap patterns and potentially lower tension in certain areas to avoid film punctures.
  • Compressibility: Fragile or compressible items (e.g., insulation batts) require careful tension control to prevent damage.
• Stretch Film Specifications:
  • Type (Cast/Blown): Different manufacturing processes yield films with varying cling, tear resistance, and stretch capabilities.
  • Gauge (Thickness): Thicker films generally offer higher strength but may require different tension settings.
  • Pre-Stretch Capability: Films are designed to be stretched (typically 150%-300%). Exceeding this can weaken the film; under-stretching wastes material.
• Machine Settings & Calibration:
  • Pre-Stretch Ratio: Set on the film carriage, determines how much the film is elongated before application. Higher pre-stretch improves film economy.
  • Wrapping Tension (Containment Force Setting): Controls how tightly the pre-stretched film is applied to the load. This is often adjusted via electronic sensors, dancer arms, or magnetic brakes.
  • Ring & Conveyor Speed Synchronization: Affects the overlap and consistency of the wrap.
• Environmental Factors: Temperature can affect film properties; colder temperatures can make film stiffer.

  

  4. Achieving Optimal Tension: A Practical Step-by-Step Approach