What Is a Double Color Striped Film Extrusion Machine?
A double color striped film extrusion machine (also called a two-color blown film machine or bicolor PE film blowing extruder) uses two independently driven screws and barrels that converge into a single shared die head. Two differently colored PE resin feeds are co-extruded simultaneously, emerging through the die as a single layered bubble with a distinct, uniform stripe pattern.
The critical engineering insight is in the die geometry: the two melt streams are kept separated right up to the die exit, where they merge side-by-side rather than stacking in layers. This produces sharp, non-bleeding color boundaries — the defining quality criterion for high-grade striped vest bags and packaging film.
How the Two-Color Co-Extrusion Process Works
The two melt streams maintain distinct flow channels through the barrel assembly and merge only at the die orifice. Stripe width ratio can be adjusted by varying the relative screw speeds — a key production advantage not available with single-screw systems.
Six Engineering Advantages Over Conventional Blown Film Lines
Print-Free Color Production
Stripe pattern is formed during extrusion itself. No ink, no printing station, no drying tunnel — reducing per-unit cost by 15–25% versus post-print processes.
Shared Single Die Head
Unlike twin-die configurations, the single die head ensures stripe registration is mechanically fixed — immune to line-speed variation or operator error.
38CrMoAl Alloy Steel Screws
Precision-finished and nitrided (HRC 65+), these screws deliver high corrosion resistance, consistent output pressure, and service life exceeding 5 years under continuous operation.
Torque Motor Winding System
Constant-tension torque motor control maintains consistent roll hardness from core to outer layer, eliminating telescoping and enabling easy roll changeover.
Independent Speed Control
Each screw has separate variable-frequency drive (VFD) control. Adjust the relative feed rate to shift stripe width ratio without stopping production.
Vest Bag Plug-In Plate Mechanism
Integrated plug-in plate mechanism for direct vest bag (T-shirt bag) production. Switch between flat bag and vest bag format without die head replacement.
How This Machine Compares: Two-Color vs. Single-Color + Printing
| Criterion | Double Color Extrusion | Single-Color + Flexo Print |
|---|---|---|
| Color registration stability | ✓ Mechanically fixed at die | ✗ Print registration varies |
| Ink/coating required | ✓ None — no ink costs | ✗ Ink + solvents required |
| Additional machines needed | ✓ Self-contained system | ✗ Separate printing station |
| Per-unit color cost | ✓ Color from masterbatch only | ✗ Ink + labor + downtime |
| Color change time | Purge screw (15–30 min) | Clean print units + rerun (>60 min) |
| Stripe width adjustability | ✓ Via screw speed ratio | ✗ Requires new printing plate |
| Film recyclability | ✓ 100% PE — easy to recycle | Mixed material — harder to recycle |
Full Technical Specification
| Machine Type | Double-screw single-die PE blown film extruder |
| Raw Materials | LDPE, HDPE, LLDPE, recycled PE granules |
| Screw Diameter | Ø55mm × 2 (two independent screws) |
| Die Head Configuration | Single shared die head (one die, two melt channels) |
| Max Folded Film Width | 800 mm |
| Film Thickness Range | 0.008 – 0.080 mm (8–80 microns) |
| Screw Material | 38CrMoAl high-alloy steel, nitrided (HRC 65+) |
| Drive System | Independent VFD motors per screw |
| Temperature Control | PID auto-temperature control per zone, 0–300°C range |
| Winding System | Torque motor — constant tension, surface winding |
| Automation Level | Automatic (VFD + PID control panels) |
| Output Products | Striped vest bags, flat bags, roll film for packaging |
| Certifications | CE, ISO 9001 |
| Warranty | 1 year standard; lifetime spare parts support |
| Installation Service | On-site engineer installation & operator training available |
Application Areas
Retail Vest Bags
T-shirt bags for supermarkets, fashion retail, and takeaway food — two-color branding without printing costs.
Household Packaging
Colored flat bags for food, produce, dry goods, and general merchandise packaging.
Industrial Liners
Heavy-gauge striped film for bin liners, pallet covers, and protective sheeting.
Agricultural Film
Two-color mulch film with visible contrast stripe to indicate row alignment in fields.
Gift & Decorative Bags
High-clarity striped film for premium carry bags and gift packaging applications.
Recycled-Content Film
Compatible with recycled PE granules — supports circular economy commitments without sacrificing stripe quality.