Stretch Film Machine Holiday Shutdown & Maintenance Guide

Properly shutting down an extrusion line for extended holidays is essential to ensure the longevity of mechanical parts and maintain high-grade film output upon restart. For facilities operating multi-layer stretch film machines, a standardized preservation routing prevents polymer thermal degradation and hardware damage.

Below is the technical procedure for executing a secure holiday shutdown on stretch film extrusion lines.

1. Controlled Purging of Extruder Barrels

The primary risk during a prolonged shutdown is the chemical degradation of stagnant resin inside the barrel.

• Purging Compound Application: Operators must use specialized high-stability purging agents to completely displace the production resin at standard operating temperatures.
• Co-Extrusion Isolation: For multi-layer lines—ranging from an economical 2-layer stretch film machine to a complex 5-layer stretch film machine—each independent feed throat, extruder barrel, and adapter block must be purged individually. This eliminates cross-layer material contamination.

2. Optimization of Thermal Profiles

Leaving the heating zones at production temperatures during a shutdown causes polymer charring, leading to black specks and gel formation when operations resume.

• Temperature Reduction: Lower the barrel heating zones to approximately 140–160°C and the die head zones to 130–150°C (subject to specific resin specifications).
• HMI Automation: On a fully automatic stretch film machine with integrated PLC controls, these exact thermal setpoints can be programmed directly into the HMI for synchronized, single-command temperature scaling. This automated reduction prevents localized overheating and extends the lifespan of both heater bands and thermocouples.

3. Residual Tension Clearance in Melt Pumps and Screen Changers

Trapped polymer tension within the melt pump and filtration systems can cause severe mechanical binding or component seizure once the line cools down completely.

• Melt Pump Drainage: Run the melt pump at a minimum frequency until material displacement through the die head stops entirely, then deactivate the pump drive.
• Screen Changer Maintenance: Open the breaker plates to clear out residual material. For a semi-automatic stretch film machine utilizing a manual screen changer, remove all mesh packs and clean the slide plate with copper scrapers. On a 3-layer stretch film machine equipped with a continuous screen changer, cycle the unit through two complete strokes to flush out hidden dead zones.

4. Depressurization of Pneumatic and Electrical Systems

Environmental moisture accumulation inside air lines can cause pneumatic valve corrosion over a multi-week holiday break.

• Pneumatic Isolate: Completely depressurize all pneumatic circuits, including nip roll loading systems, winding shaft clamps, and trim removal lines. Drain every Filter-Regulator-Lubricator (FRL) unit to eliminate condensed water, leaving all mechanical valves in a relaxed state.
• Electrical Discharge: For a fully automatic stretch film machine configuration featuring servo-driven winding units, discharge the DC bus capacitors according to the manufacturer’s technical guidelines to eliminate residual electrical stress.

5. Anti-Corrosion Surface Treatment for Rollers and Shafts

The mirror-finished, hard-chrome plated surfaces of chill rolls and winding shafts dictate the ultimate optical clarity and structural geometry of the stretch film.

• Chemical Protection: Apply a professional-grade, non-silicone anti-rust inhibitor to all polished surfaces using lint-free cloths.
• Multi-Roll Care: On a 5-layer stretch film machine where multiple chill rolls operate in sequence, apply the inhibitor meticulously to the primary contact rolls and rotating unions. Wrap the treated components with anti-static polyethylene sheeting to isolate them from ambient humidity.