DHL Bag Making Machine: Courier & Pre-Open Lines | OYANG

Q: What is a DHL bag making machine?

A DHL bag making machine is an industrial converting line engineered to produce courier, express, and e-commerce mailer bags from co-extruded polyethylene (LDPE/HDPE) film or kraft paper composites. It integrates inline hot-melt destructive adhesive applicators, silicone release liner laminators, and lip folding stations to manufacture tamper-evident logistics bags at speeds up to 180 bags/min.

Q: How does a tamper-evident destructive adhesive tape work on courier bags?

Tamper-evident closure relies on high-tack synthetic block copolymer hot-melt adhesive applied directly to the film lip. When the recipient seals the bag, the adhesive forms a molecular bond with the poly film within 30 seconds. Attempting to peel the seal forces the multi-layer polyethylene film to tear completely, providing unmistakable visual evidence of unauthorized package opening.

Q: What are roll-fed pre-opened bags and how are they produced?

Roll-fed pre-opened bags (commonly used on Autobag automated bagging systems) are continuous rolls of plastic pouches where the top face of each bag is pre-slit while the bottom remains connected by micro-perforations. They are manufactured using rotary perforation cylinders and slitters that maintain calibrated 8–12 N burst tensile limits, enabling warehouse packaging robots to rapidly feed, blow open, load, and seal products.

Q: How do OYANG machines prevent hot-melt adhesive from sticking to cutting knives?

OYANG lines utilize high-speed pneumatic cut-off valves synchronized via EtherCAT bus motion control. The adhesive applicator stops dispensing hot-melt glue precisely 8mm to 12mm before each bag edge, creating a dry perimeter margin that ensures side-sealing and cutting knives never touch wet adhesive, eliminating machine jamming and downtime.

Q: Can an eco-friendly kraft paper courier mailer be produced on these lines?

Yes. By fitting heated platen bars and cold-glue or double-sided peel-and-seal tape applicators, OYANG converting lines can process extrusion-coated or pure kraft paper (80–140 g/m²) into plastic-free e-commerce mailers, frequently incorporating dual adhesive lines to facilitate easy e-commerce consumer returns.

DHL Bag Making Machine: Engineering Tamper-Evident Courier & Roll-Fed Pre-Opened Packaging

An industrial DHL bag making machine (courier mailer and pre-opened bag line) converts co-extruded multi-layer polyethylene (LDPE/HDPE) film, kraft paper composites, and nonwoven hybrid substrates into secure logistics packaging at speeds up to 120–180 bags/min. Modern courier converting platforms integrate high-precision slot-die hot-melt adhesive coaters that apply permanent destructive tamper-evident adhesive strips (requiring > 100% film substrate tear upon opening), pneumatic lip folding boards with active 7 kV static de-ionizers, and optional servo rotary perforation cylinders to produce roll-fed pre-opened bags for automatic e-commerce packaging machines.

100% Tear

Substrate destruct test: hot-melt adhesive bonds permanently, tearing the poly film upon unauthorized opening.

120–180 /min

Continuous servo conversion speed for standard A4/A3 courier flyers with inline destructive tape application.

±0.5 mm

Lip folding and release liner tracking tolerance maintained across fluctuating web unwinding speeds.

8–12 N

Calibrated perforation burst tensile strength engineered for automated roll-fed e-commerce packaging machines.

Tamper-Evident Engineering: Adhesive Rheology & The Destructive Bond

Courier security packaging (standardized by international logistics carriers like DHL, FedEx, and UPS) requires complete integrity. The seal must guarantee immediate visual evidence of tampering under temperatures ranging from -20°C (freezer transport) to +65°C (summer tarmac storage):

1. Hot-Melt Adhesive Chemistry & Slot-Die Extrusion

Rather than using double-sided tape that can be picked off or heated open without trace, OYANG courier lines deploy inline hot-melt slot-die coating applicators. High-tack pressure-sensitive adhesive (PSA based on SIS/SBS synthetic block copolymers) is melted at 155°C–165°C and pumped through an air-actuated micro-slot nozzle directly onto the continuous film lip. Applying a coating weight of 25 to 35 g/m² ensures that when the end customer closes the bag, the adhesive forms a covalent molecular bond with the untreated poly film, making non-destructive peeling physically impossible.

2. Eliminating Adhesive Bleed & Cutter Contamination

The primary engineering bottleneck in high-speed courier bag production is adhesive “bleeding” onto side-weld flying knives. Standard machines suffer from glue accumulation, causing ragged side seams, plastic stringing, and line shutdowns every 2 hours. OYANG resolves this via a microsecond pneumatic glue cut-off valve synchronized with the main line virtual master axis. The adhesive application stops exactly 8mm to 12mm short of each side edge, ensuring clean, knife-contact-free side welding and non-stop 24/7 converting.

Substrate Processing Matrix: Co-Ex Poly vs. Paper Composites vs. Pre-Opened Rolls

Modern courier mailer conversion encompasses three dominant packaging formats, each requiring specific mechanical unwinding, folding, and cutting configurations:

Courier Bag Classification	Raw Web Substrate Structure	Inline Functional Units	Production Speed	Target Logistics Application
Standard Co-Ex Poly Mailer (DHL / Courier Flyer)	Black/White co-extruded LDPE/LLDPE (50–80 μm)	Corona treater, slot-die glue applicator, lip folder, flying hot-knife	120–180 bags/min	Global express freight, apparel shipping, document pouches
Gusset-Bottom Heavy Mailer	Virgin / Recycled LDPE + Metallocene (70–120 μm)	Inline bottom motorized gusset triangle, double-pass side sealing	80–120 bags/min	Heavy footwear, consumer electronics, bulk retail fulfillment
Eco-Friendly Paper Courier Bag	Extrusion-coated or barrier-laminated Kraft (80–140 g/m²)	Water-based cold glue / hot-melt line, dual-strip return tape folder	70–110 bags/min	Sustainable retail, plastic-free fashion logistics
Roll-Fed Pre-Opened Bag (Autobag Format)	Tubular poly film or composite barrier film	Servo rotary perforation knife, one-side slit, center-surface rewinder	100–150 m/min web travel	Automated fulfillment centers, high-speed warehouse packaging robots

Roll-Fed Pre-Opened Bags: The Automated Fulfillment Standard

In automated fulfillment hubs (such as Amazon and third-party logistics centers), manual bag loading is being replaced by automatic packaging machines (e.g., Autobag systems). These robotic lines require bags delivered on a continuous roll, with each bag pre-opened on one face and joined by micro-perforations:

Continuous Micro-Slitting of the Bag Face: Tubular poly film unwinds under closed-loop dancer tension. A precision ceramic razor slits the upper film web longitudinally along the center line, while the lower web remains continuous, creating an accessible mouth opening for automated product dropping.
Servo-Driven Rotary Perforation Tooling: The web enters a hardened rotary perforation cylinder. High-speed tool-steel teeth cut micro-ties across the width of the film. OYANG engineers calibrate the tie-to-cut ratio to maintain a burst strength of 8 N to 12 N. This precise tensile resistance allows packaging robots to advance the roll at high acceleration without premature tearing, while allowing clean separation when the robotic arm grips the finished pack.
Controlled Tension Surface Rewinding: The converted web is rewound onto paper or plastic cores using dual surface-driven winding drums. As the roll diameter grows up to 400mm, PLC software applies a logarithmic taper-tension decay curve (reducing torque from 100% to 65%), preventing inner-layer telescoping and core crushing.

Lip Folding, Anti-Static De-Ionization & Release Liner Tracking

Static electricity is the invisible enemy in high-speed thin-film converting. When co-extruded polyethylene film travels over rollers at 150 m/min, triboelectric charging generates electrostatic potentials exceeding 25,000 Volts:

1. Electrostatic Discharge (ESD) Neutralization

Static charges cause the thin film lip to flutter, cling to folding boards, and misalign relative to the adhesive line. Furthermore, when the siliconized protective release liner (covering the hot-melt glue) is pulled from its dispenser, extreme static sparks can ignite solvent vapors or deliver painful shocks to operators. OYANG integrates high-frequency AC ionizing bars (7.5 kV, 50 Hz) immediately preceding the lip folding board and at the release liner laminating nip, dissipating surface charges down to < 0.5 kV.

2. Optical Edge Guiding (EPC) for Release Film Placement

A skewed silicone release film results in exposed hot-melt glue, causing bags to stick together inside shipping cartons. OYANG lines deploy micro-ultrasonic edge sensor guiding systems (EPC) with a response frequency of 200 Hz. The release liner dispenser shifts laterally on precision linear ball slides, tracking the web edge to within ±0.5mm regardless of machine acceleration or master roll runout.

Featured OYANG Machinery Platforms for Logistics Packaging

Manufactured inside OYANG’s 130,000&mflat; CNC digital manufacturing base with Japanese MAZAK and OKUMA 5-axis machining centers, our specialized converting and slitting lines lead the flexible packaging sector:

OYANG 650S High-Speed Converting Line

The premier machine platform for 3-side seal barrier packaging, courier mailers, and document flyer envelopes. Equipped with multi-axis servo drives and digital thermal seal bars.

Converting Speed: Up to 180–220 CPM continuous
Sealing Control: Individual PID temperature regulation per head
Attachment Compatibility: Inline hot-melt glue slot dies & lip folders

View 650S Technical Specs

ONL-XE1800 Master Roll Slitter Rewinder

Precision web slitting and rewinding machine for wide co-extruded LDPE film, Kraft paper liners, and pre-opened bag stock with automated closed-loop taper tension.

Working Width: Up to 1,800mm master rolls
Operating Speed: Up to 300 m/min continuous web
Slitting Precision: Rotary shear knives with ±0.1mm tolerance

View ONL-XE1800 Technical Specs

OYANG 650Z Center-Seal Express Line

High-speed center-sealing machine engineered for tubular poly courier packaging, gusseted e-commerce bags, and heavy-duty shipping mailers.

Production Output: Up to 180 CPM
Gusset Forming: Continuous motorized side/bottom gusseters
Drive System: Full EtherCAT digital motion controller

View 650Z Technical Specs

Video Demonstration: High-Speed Multi-Function Flexible Converting

Frequently Asked Questions (FAQ)

What is a DHL bag making machine?

A DHL bag making machine is an industrial converting line engineered to produce courier, express, and e-commerce mailer bags from co-extruded polyethylene (LDPE/HDPE) film or kraft paper composites. It integrates inline hot-melt destructive adhesive applicators, silicone release liner laminators, and lip folding stations to manufacture tamper-evident logistics bags at speeds up to 180 bags/min.

How does a tamper-evident destructive adhesive tape work on courier bags?

Tamper-evident closure relies on high-tack synthetic block copolymer hot-melt adhesive applied directly to the film lip. When the recipient seals the bag, the adhesive forms a molecular bond with the poly film within 30 seconds. Attempting to peel the seal forces the multi-layer polyethylene film to tear completely, providing unmistakable visual evidence of unauthorized package opening.

What are roll-fed pre-opened bags and how are they produced?

Roll-fed pre-opened bags (commonly used on Autobag automated bagging systems) are continuous rolls of plastic pouches where the top face of each bag is pre-slit while the bottom remains connected by micro-perforations. They are manufactured using rotary perforation cylinders and slitters that maintain calibrated 8–12 N burst tensile limits, enabling warehouse packaging robots to rapidly feed, blow open, load, and seal products.

How do OYANG machines prevent hot-melt adhesive from sticking to cutting knives?

OYANG lines utilize high-speed pneumatic cut-off valves synchronized via EtherCAT bus motion control. The adhesive applicator stops dispensing hot-melt glue precisely 8mm to 12mm before each bag edge, creating a dry perimeter margin that ensures side-sealing and cutting knives never touch wet adhesive, eliminating machine jamming and downtime.

Can an eco-friendly kraft paper courier mailer be produced on these lines?

Yes. By fitting heated platen bars and cold-glue or double-sided peel-and-seal tape applicators, OYANG converting lines can process extrusion-coated or pure kraft paper (80–140 g/m²) into plastic-free e-commerce mailers, frequently incorporating dual adhesive lines to facilitate easy e-commerce consumer returns.

Upgrade Your Logistics & Courier Packaging Converting

Eliminate glue bleed downtime, improve bag security, and expand into high-growth automated pre-opened roll packaging. Consult with OYANG flexible packaging engineers to review machine layout schematics and formal equipment quotations.

Download Flexible Packaging Brochure (PDF)