A Casting Machine, commonly known as a film casting or cast film extrusion machine, is designed to produce high-quality plastic films with excellent clarity, precise thickness control, and stable mechanical performance. This technology is widely used for stretch films, protective films, food packaging films, adhesive films, and multi-layer functional materials. Understanding how a casting machine works is essential for manufacturers who want to optimize film performance, reduce production errors, and ensure consistent product quality. Modern systems such as SAIBANG’s Casting Machine combine advanced extrusion engineering with automated control systems to create films that meet the demanding requirements of today’s industrial applications.

The casting process seems simple on the surface—melting plastic and spreading it into a thin film—but achieving accurate thickness and excellent optical quality requires highly coordinated mechanical, thermal, and control systems.

1. Melting and Extrusion: How Raw Materials Enter the Casting Process

The casting process begins with raw materials, typically in the form of polymer pellets. These materials enter the hopper and feed into the extruder, where a rotating screw transports and melts the resin. The extruder is divided into multiple temperature zones, each designed to gradually heat the polymer to its melting point without degrading it.

As the polymer melts, the screw pressure and design ensure consistent mixing and elimination of air pockets. The goal is to achieve a homogeneous melt flow so that the film maintains stable properties throughout its width and length. Depending on production requirements, single-layer or multi-layer co-extrusion systems may be used, allowing different materials to feed into separate extruders.

SAIBANG’s Casting Machine features advanced screw design and precise temperature control to ensure stable plastification, even when processing multiple materials simultaneously.

Key Stages of Melting and Extrusion

1. Material Feeding – Resin enters the extruder through the hopper.

2. Heating and Compression – Temperature gradually increases across zones.

3. Melt Homogenization – Screw shearing action mixes materials thoroughly.

4. Pressure Build-Up – Melt is pressurized before entering the die.

5. Melt Transfer to the Die – Ensures a smooth, consistent flow.

Extrusion Zone Table

This controlled melting process forms the foundation for stable casting film quality.

2. Flat Die Distribution: Forming the Melt into a Thin Film

After reaching the correct melt state, the polymer enters the flat T-die, one of the most critical components of a casting machine. The die spreads the molten polymer into a thin, wide sheet. The geometry of the die manifold ensures even flow distribution so that the film thickness remains uniform across its width.

Film thickness accuracy depends heavily on die lip design, flow channel polishing, and precise temperature management. Multi-layer films use either feed-block dies or multi-manifold dies that allow different melt streams to form layered structures.

ROCKY’s systems—such as SAIBANG’s Casting Machine—use high-precision T-dies to maintain consistent layer ratios, even under high-speed production conditions.

Functions of the Flat Die

• Converts melt into a uniform sheet

• Controls initial film thickness

• Helps form multi-layer structures

• Maintains exact melt temperature

• Minimizes flow marks and optical defects

Die Performance Table

Once the melt exits the die, the film is ready for immediate cooling and shaping.

3. Rapid Cooling on the Chill Roll: Converting Melt into a Solid Film

The melt film flows from the die directly onto the chill roll—a highly polished, temperature-controlled cylinder. This step is crucial because the film must cool rapidly to achieve clarity, smoothness, and mechanical strength.

The chill roll rotates at controlled speed, pulling the film while instantly solidifying it. Proper cooling rate prevents crystallization issues, reduces haze, and ensures smooth surface appearance. A vacuum box or electrostatic pinning system may be used to ensure intimate contact between the hot melt and the cooling roller.

SAIBANG’s Casting Machine offers advanced chill roll systems engineered for fast heat dissipation and excellent film flatness.

Cooling Process Breakdown

• Melt film contacts chill roll

• Heat transfers out rapidly

• Film solidifies and stabilizes

• Cooling rollers adjust tension and thickness

Cooling System Components

Precise cooling ensures the film achieves its designed clarity, strength, and surface finish.

4. Stretching, Edge-Trimming, and Thickness Fine-Tuning

After cooling, the film travels through a series of rollers for thickness stabilization, edge control, and mechanical stretching. These rollers adjust tension and eliminate minor thickness variations caused during die flow. A thickness measurement system continuously scans the film and sends feedback to the die or automatic gauge control system.

Edge-trimming blades cut off uneven edges produced during cooling, making the final film width precise. The trimmed material is usually recycled back into the extrusion line.

What Happens During This Stage?

• Tension rollers stretch the film to achieve consistent thickness

• Edge trimmers remove excess film for accurate width

• Thickness gauges monitor output in real time

• Automatic adjustments ensure consistent film structure

Quality Control Table

This section of the machine ensures the final film meets customer specifications.

5. Winding: Producing Ready-to-Use Cast Film Rolls

The final stage of the casting machine is the winding system. Once the film has passed through stabilization and trimming, it is guided onto the winder. Modern winding systems use tension control, servo motors, and lay-on rollers to ensure tight, smooth, wrinkle-free rolls.

Depending on film type, winding can be surface winding, center winding, or automatic turret winding. Each method accommodates different film thicknesses and properties.

SAIBANG’s Casting Machine integrates intelligent winding systems designed to prevent telescoping, air entrapment, and roll deformation.

Functions of the Winding Section

• Maintains consistent roll tightness

• Prevents wrinkles and bubbles

• Enables automated roll changeovers

• Protects film surface quality

Winding Modes Table

A high-quality winding system ensures the film is ready for slitting, conversion, or packaging.

Summary

A casting machine works through a highly coordinated process that transforms raw polymer pellets into a precisely engineered film. The workflow includes melting and extruding the material, distributing it through a flat die, cooling it instantly on chill rolls, stabilizing its thickness, and winding it into finished rolls. Each stage plays a vital role in determining film quality, mechanical strength, and visual appearance.

Multi-layer casting systems enhance functionality by combining different materials, allowing manufacturers to tailor properties such as clarity, strength, sealing performance, and adhesion. Machines like SAIBANG’s Casting Machine are engineered to deliver precise temperature control, efficient cooling, accurate thickness regulation, and intelligent winding—all essential for producing high-performance casting films.

Understanding how each section of a casting machine operates helps manufacturers optimize production, reduce waste, maintain film stability, and ensure consistent output for various industrial applications.