Views: 0 Author: Wendy Liu Publish Time: 2026-05-11 Origin: Dongguan Jewshin Intelligent Machinery Co., Ltd.
If you've been researching shrink packaging equipment, you've almost certainly run into the terms "L sealer" and "shrink tunnel." And if they sound like they do the same thing — you're not alone. This is one of the most common areas of confusion for buyers in the packaging industry.
The short answer: they're two distinct pieces of equipment that work together as a system. Understanding how each one works, and why you need both, will save you from making a costly purchasing mistake.
Let's clear this up once and for all.
An L sealer (sometimes called an L-bar sealer) is a machine that seals film around a product using a heated sealing bar shaped like the letter "L." The film is wrapped around the product, and the L-shaped sealer cuts and heat-seals two perpendicular edges — creating an enclosed package.
The key word here is sealing. The L sealer doesn't shrink anything — it just wraps and seals.
Here's how it works in practice:
The operator or an automated feeder places the product onto a lay-on film bed or conveyor
The film is pulled over the product from a roll above
The L-bar sealer descends, sealing two edges of the film (forming an "L" shape)
The sealed package moves forward into the shrink tunnel
At Jewshin, we offer several L sealer configurations, including the Scissor L-Type Full Automatic Sealing Machine (JX-A5645) — a scissor-style sealer popular for daily chemical, electronics, food, medical, and toy industries — and the Vertical L-Type Sealing Machine (JX-A6345/6352), designed specifically for long objects like beverages, beer cans, glass bottles, and pipes.
A shrink tunnel is a heated chamber — essentially a conveyorized oven — that applies controlled heat to the sealed package, causing the shrink film to contract tightly around the product.
Without a shrink tunnel, your L-sealed package would have loose, baggy film hanging off it. The tunnel is what gives shrink packaging its clean, tight, professional appearance.
Typical shrink tunnel features include:
Adjustable conveyor speed and temperature controls
Consistent heat distribution for uniform shrink results
Tunnels sized to match production throughput requirements
Options for steam, air, or infrared heat sources
Here's the critical point: L sealers and shrink tunnels are designed to work together. Think of them as a two-step process:
Step 1 — Seal: The L sealer wraps and seals the film around your product.
Step 2 — Shrink: The package passes through the shrink tunnel, where heat causes the film to conform tightly to the product shape.
You can't skip either step. An L sealer alone gives you a loose, unsealed-looking package. A shrink tunnel alone is useless without a pre-sealed package to shrink.
This is why you often see these systems marketed as "L sealer and shrink tunnel" combos or as part of a complete heat shrink packaging line.
Aspect | L Sealer | Shrink Tunnel |
Primary function | Seal film around product | Apply heat to shrink film |
Heat application | Sealing bars (localized heat) | Full chamber heat (convection/conduction) |
What it creates | Enclosed, sealed package | Tight, conformal package finish |
Stand-alone use? | Partially (seals but doesn't shrink) | No (requires pre-sealed package) |
Controls | Seal temperature, dwell time, knife timing | Tunnel temperature, conveyor speed, air flow |
Film type | Polyolefin (POF), PVC, polyethene | Same films — but needs full heat exposure |
Not all L sealers are built the same. Here are the main variants:
Uses a scissor-action mechanism to pull film and create the seal. The scissor design provides even tension across the seal. Our JX-A5645 scissor L sealer is a full-automatic model widely used across industries.
Uses a straight horizontal bar that cuts and seals one side, while film is folded over manually on the other. More manual operation but simpler and cheaper. Good for low-volume operations.
The film is pulled vertically around a tall or cylindrical product (like long pipes, bottles, or multi-packs). The vertical orientation handles awkward shapes better. Our Vertical L-Type Sealing Machine is purpose-built for this.
The seal is applied on the side of the package rather than at the ends. Useful for certain display packaging or when the package needs to hang.
Similarly, shrink tunnels vary based on the application:
The most common type. Packages travel through on a conveyor belt. Temperature and speed are adjustable. Suitable for most production rates.
Uses steam for heat — provides very even, smooth shrink results, especially on complex product shapes. Common in food and pharmaceutical applications.
Non-continuous. Products are placed inside a heated chamber for a set time. Lower throughput but more precise control. Useful for very large or irregular items.
The choice of shrink film affects both the L sealer and tunnel performance:
POF (Polyolefin): The most versatile film. Works with both L sealers and tunnels. FDA-approved for food contact. Provides a crystal-clear finish.
PVC: Lower cost but limited temperature range. Can release harmful fumes when heated. Being phased out in many regions.
Polyethylene (PE): Thicker, more durable. Good for industrial or heavy products. Requires higher tunnel temperatures.
For most product types, we recommend POF film with our L sealer and tunnel systems.
L sealer + shrink tunnel combinations are ideal for:
Beverage multipacks: Cans, bottles, and cartons grouped together with a tight shrink overwrap
Card and printed products: Books, games, calendars wrapped in protective clear film
Cosmetics: Cream boxes, skincare sets, and fragrance bottles with a retail-ready overwrap
Electronics: Phone cases, accessories, and small devices protected in clear film
Food products: Baked goods, frozen foods, and confectionery
Hardware and tools: Multi-piece kits and tool sets
When selecting your L sealer and shrink tunnel setup, consider:
1. Product dimensions and shape
Long, cylindrical products → vertical L sealer
Flat, boxy products → scissor or I-bar L sealer
Irregular shapes → consider a 3D overwrapper like our JX-D650/D750/800 3D Overwrapping Machine
2. Production speed
Low to medium volume → pneumatic L sealer + standard tunnel
High volume → servo-driven L sealer + high-speed tunnel with variable conveyor
3. Film type and thickness
Thinner films (POF) → standard tunnel settings
Thicker films (PE) → higher temperature tunnel required
4. Space constraints
Compact facilities → look for a combined L sealer + tunnel unit where available
Larger facilities → separate units allow independent speed tuning
A well-maintained L sealer and tunnel system will deliver consistent results for years:
Clean the sealing jaws regularly — adhesive residue from film can weaken seal quality
Check and replace wear parts — seal knives, PTFE tapes, and conveyor belts wear out over time
Calibrate temperature controls seasonally — heat settings can drift with ambient temperature changes
Inspect film tensioners — uneven film feed causes seal wrinkles and poor shrink results
Keep the tunnel interior clean — dust and film debris accumulate and affect heat distribution
About the Author
Wendy Liu is the CEO of Dongguan Jewshin Intelligent Machinery Co., Ltd., a manufacturer and exporter of heat shrink packaging systems and automated packaging equipment serving clients in North America, Europe, Southeast Asia, the Middle East, South America, and Africa. Explore our full range of heat shrink packaging machines or reach out to our team for a consultation on your specific application.
