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Sealing machines (sometimes called heat sealers, bag sealers, or package heat sealers) are devices that create airtight bonds in packaging materials. They operate by applying a controlled burst of heat and pressure to the open edge of a thermoplastic bag or pouch. For example, an automated form-fill-seal machine (shown above) will fill a pouch with product and then activate its sealing bar to fuse the bag closed. In this process, the heat causes the plastic layers to melt and intermingle; under pressure, the molten layers bond together. When the plastic cools, it forms a durable, leak-proof seal. This heat-and-seal method is essential in many industries: foods, medical supplies, and electronics are often sealed in plastic to protect them from air and moisture. An airtight, heat-sealed package keeps contents fresh longer (for example, heat-sealed cookies or snacks stay crisp) and shows any tampering (the seal marks if broken).
How a Sealing Machine Works (Fully Automatic Aluminum‑Foil Sealer)
A fully automatic foil sealing machine streamlines the entire sealing cycle on a continuous production line:
Automatic feeding & positioning
Containers (cups, trays or pouches) are loaded onto an infeed conveyor. Photo‑electric sensors detect each container’s presence and precisely position it beneath the sealing head.
Foil liner application
A roll of pre‑printed aluminum foil is unwound and indexed by servo‐driven rollers. Just before each container arrives, the machine’s liner applicator cuts and places a foil disc over the open mouth.
Sealing head activation
Once a container and foil are aligned, the pneumatic sealing head descends. Heated die plates—set to a precise temperature—press the foil against the container rim under calibrated force.
Heat fusion & dwell
For a predefined dwell time, the heat and pressure melt the foil’s heat‑seal lacquer and bond it uniformly to the container flange, forming an airtight, tamper‐evident seal.
Cooling & release
After the dwell interval, the head retracts and the seal cools under gentle air flow or in an integrated cooling tunnel. A discharge conveyor then carries the sealed containers away for labeling or boxing.
Continuous monitoring
An onboard PLC monitors temperature, pressure and cycle count. Alarms or automatic shutdowns engage if any parameter drifts outside set limits, ensuring consistent, leak‑proof seals at high throughput (up to hundreds of containers per minute).
This fully automatic heat‑and‑seal process—feeding, foil placement, heated press, dwell cooling and ejection—delivers fast, reliable sealing with minimal operator intervention.
Types of Sealing Machines
Various sealing machine designs exist to suit different packaging needs. A simple impulse heat sealer is a common bag sealer in small-scale operations. An impulse sealer heats the wire only during the sealing cycle: when you clamp the bar down, it sends a quick electrical pulse through the wire, which heats, melts the film, and then cools immediately. Because it uses power only in short bursts and cools right away, an impulse bag sealer requires no warm-up and is very safe to use. (Operators are unlikely to burn themselves, since the heated element is only hot when clamped on the bag.) Impulse sealers are ideal for everyday poly bags and lightweight thermoplastic films; they are compact, easy to operate, and energy-efficient.
In contrast, larger or high-volume lines often use continuous heat sealing machines. These use a constant-temperature heated bar or band. For example, a continuous band sealer feeds bags on a conveyor belt while a long heated bar presses them shut. Such machines run continuous heat along the sealing path, making them suitable for sealing heavy-duty or multilayer films and for very fast throughput. They allow rapid, on-the-fly sealing of dozens of packages per minute. Continuous-band or automatic heat-and-seal machines are common in industrial settings where speed and consistency matter.
Other specialized sealers exist as well. For example, induction sealers use electromagnetic heating to bond foil liners on bottle caps (tamper-evident seals), and vacuum sealers first remove air before sealing. Hot bar sealers melt films by passing current through metal bars. But for simple bag and pouch sealing, the key categories are impulse (burst-heating) versus constant heat, and manual versus fully automatic machines. (Sometimes the device is simply called a sealing machine or seal machine interchangeably with “heat sealer.”)
Summary
A sealing machine works by applying heat and pressure to melt together the edges of thermoplastic packaging. Whether it’s a simple handheld bag sealer or a fully automatic heat-and-seal machine on a factory line, the principle is the same: two layers of plastic are clamped together, a heater melts them, then they cool to form a permanent, airtight bond. Different designs (impulse vs. continuous, manual vs. automatic) optimize this process for various products and volumes. In every case, the result is a sealed package that locks out air and moisture, keeps contents fresh (even heat-sealed cookies stay crisp), and provides a clean, tamper-evident finish. By understanding these steps and machine types, professionals can choose the right sealing equipment to meet their packaging needs, ensuring consistent, high-quality seals on their products.
How do sealing machines work FAQ
Transparency is the cornerstone of our Yundu team. That’s why below, you can find the most common questions and answers we receive surrounding our sealing machines.
Sealing machines fuse thermoplastic packaging by applying controlled heat and pressure. A heated element melts the bag’s open edge while jaws press the layers together. After a brief dwell, the seal cools to form a permanent, airtight bond.
Most sealing machines use a heating element (wire or bar) and a heat‑resistant pad. When the jaws close, current passes through the element, melting the film. Pressure holds the layers together until cooling solidifies the fusion.
Sealing equipment creates leak‑proof, tamper‑evident closures on flexible packaging. It protects contents from moisture, oxygen, and contaminants, extends shelf life, and ensures product integrity during storage and transport.
A sealer clamps packaging between heated jaws and a backing pad. The heating element melts the film, and pressure bonds the layers. Once cooled, the sealed package is released, leaving a durable, airtight seam.
Sealcoating typically refers to asphalt protection: a slurry of binder and fine aggregate is spread over pavement, then dries to shield against water, UV, and chemical damage—unrelated to heat sealing plastics.
A vacuum sealer removes air from the package before heat‑sealing the open edge. The absence of oxygen prevents spoilage and freezer burn, and the heat seal ensures the bag remains airtight.
An impulse heat sealer delivers a short electrical pulse to a heating wire only during sealing. It requires no warm‑up, uses power in bursts, and cools immediately when the jaws open, making it energy‑efficient and safe.
Impulse sealers pulse-heat only during sealing cycles, ideal for low volumes and thin films. Continuous sealers maintain a constant-temperature bar or band, suited for high-speed lines and heavier or multilayer materials.
Yes—by adjusting temperature, dwell time, and pressure, most machines can seal polyethylene, polypropylene, laminates, foil films, and even laminated foil pouches, accommodating varying thicknesses and barrier properties.
Regularly clean the heating element and pad, check electrical connections, and replace worn Teflon covers or gaskets. Calibrate temperature and pressure settings per manufacturer guidelines, and verify seal integrity with periodic strength tests.
