Bag food packaging machines are primarily classified into two types. The first type is the form-fill-seal (FFS) machine, which uses roll-stock material—such as polyethylene film or composite plastic film—to form bags, fill them with measured quantities of powdered, granular, or liquid products, and optionally perform degassing (including re-inflation) before sealing and cutting. The second type includes pre-made pouch sealing machines, which perform the filling, degassing (with the possibility of re-inflation), and sealing, or just sealing, of pre-formed pouches.
Thermal Sealing Method for Plastic Film
Both form-fill-seal machines and pre-made pouch sealers rely on heat-sealing mechanisms to thermally bond packaging materials. As illustrated in Figure 11-37, common heat-sealing techniques include flat plates, rollers, belts, sliding clamps, and the melt-cut method. Table 11-5 summarizes the principles and characteristics of these sealing types. By adjusting control parameters such as temperature, pressure, and time, the sealing process can be optimized to suit different packaging materials and container types.
Form-Fill-Seal Packaging Machine
The automatic form-fill-seal packaging machine uses pre-wound packaging film to autonomously form bags, fill them, seal them, and cut them. This packaging style is suitable for powders, granules, blocks, liquids, and colloidal materials, and is typically used for small food items, granular beverages, and fast food. The film used can be plastic or composite material. Depending on the machine, bags are formed from either a single roll of film or two rolls of film, with single-roll machines being more commonly used.
This machine produces various types of bags, the most common being center-seam back-seal, four-side seal, and three-side seal (see Figure 11-38). Although specific machine configurations vary depending on the bag type, the core components and operating principles remain generally consistent. Figure 11-39 illustrates the typical packaging process of a form-fill-seal machine. Variations in structure and process exist depending on the model, but the basic packaging methodology remains the same.
Form-filling sealing machines are categorized by layout—vertical or horizontal—and by motion type—continuous or intermittent bag making.
Composition and Structure of the Form Remover Machine
Although there is diversity in models adapted for different materials and bag styles, form-sealing machines share basic components. For example, a typical vertical continuous form-fill-seal machine (Figure 11-40) consists of a drive system, a film feed mechanism, a bag-forming and sealing unit, a material dosing device, and an electronic control and detection system. Power and drive devices inside the machine cabinet drive the vertical and cross-sealing rollers as well as the volumetric fillers. The film reel on the idle stand rotates smoothly, and the film is guided through rollers that provide tension, straighten, and align the film precisely.
Bag forming and sealing include the bag holder along with vertical and horizontal sealing devices. Different combinations allow for the formation of various bag shapes and sealing styles, often serving to distinguish between machine types.
Material feeding is carried out by volumetric feeders, most commonly adjustable volumetric cups for powders and granules. In the rotating-disc feeder illustrated, material moves from the hopper into the volumetric cups arranged around the circumference of the disc, then fills the film tubes that form automatically.
The electronic control system is at the heart of the machine, allowing parameter settings for vertical and cross-seal temperatures, as well as color-mark detection data on printed film, thereby ensuring consistent packaging quality.
Principles of Forming, Filling, and Sealing
Horizontal Forming, Filling and Sealing
a. Three-Side Sealing Bag: As shown in Figure 11-41, the plastic film from the reel enters the container where it is formed into a U-shape and opened by the dispenser. When the filler descends to the filling position, the cross seal is closed during filling of the material; then both the cross seal and the filler are reset. Next, the vertical seal is closed against the heat seal and the film is advanced by one bag length, followed by cutting the sealed bag.
b. Horizontal Pillow Bag: Figure 11-42 illustrates a horizontal pillow-type wrapping machine. This continuous-operation machine automatically wraps, crimps, and cuts products such as cookies and instant noodles. Film from a roll is guided into the hopper and formed into a tube around the items conveyed by the food chain. The film advances under tension, with the center seam sealed by a sealing wheel. Cross-sealing and cutting produce the final pillow-shaped package, which is released by the conveyor. When colored marking tape is used, the optoelectronic detection system adjusts the paper length in real time to ensure precise positioning.
Vertical Form, Fill, and Seal
a. Formation of an Intermittent Pouch with a Center Seam Sealant: As shown in Figure 11-43, the plastic film from the reel is guided into the container to form a cylindrical shape with a center seam overlap. The filling tube serves as the bag container externally and as a material feeder internally. A vertical sealer presses against the overlapping film to heat-seal it vertically, then retracts. Next, a horizontal sealer performs a crisscross seal while pulling the film downward by one bag length, then sealing and cutting the bag. Each simultaneous cross seal closes the bottom of the upper bag and the top of the lower bag, while filling occurs as the film advances.
b. Formation of Four Seal Bags: The machine that produces four-side-sealed bags can use two film rolls arranged symmetrically and longitudinally sealed before cross-sealing and cutting after filling. The single-roll four-side-sealing machine (Figure 11-44) splits the film in the middle and rejoins the halves during bag formation.
c. Formation of a Single-Wound Three-Side Sealing Bag: Using a single film roll, this method forms either a three-side-sealed bag or a four-side "false-sealed" bag (Figure 11-45). Pillow packaging (Figure 11-46) involves sealing longitudinally after forming the container, then cross-sealing and cutting, producing a center-seamed folded bag with sealed ends.
Prabuation Bag Sealing Machine
This machine handles pre-sealed plastic bags and includes standard sealers, vacuum packaging machines, and vacuum-inflation packaging machines. Standard sealers with simple heat-sealing devices are not discussed in detail.
Vacuum packaging machines typically combine vacuuming and inflation functions and are available in intermittent and continuous models.
Intermittent Vacuum Inflation Packaging Machine
This uses composite film pouches, which are filled and manually placed onto a vacuum-chamber heat-sealing bar, then automatically evacuated, inflated, and sealed. The size and number of bags per operation vary. Suitable for solids, granules, semi-liquids, and liquids, this method is common in food production due to its flexibility and ease of use.
Alternating Vacuum Inflation Machine Type
Figure 11-47 shows the common types: tabletop models, single-chamber, dual-chamber (single or dual lids), and tilting (conveyor belt). The vacuum level reaches an absolute pressure of 1–2 kPa, with a production speed of 2–4 cycles per minute.
The single-station, benchtop machine features a single short heat-sealing bar, suitable for laboratory or small-group use. The two-station machine shares a vacuum and inflation system between its two stations, increasing efficiency by allowing one station to evacuate while the other is being loaded or unloaded.
The flat bottom surface of the vacuum chamber makes it difficult to seal products with high liquid content, because the sealing lip must rest on the chamber floor to prevent leaks, limiting its suitability for highly liquid products.
The conveyor belt vacuum inflation machine (tilting) automatically feeds products into the chamber, increasing automation and processing capacity. The inclined bottom of the chamber prevents liquid spillage during sealing.
Working Principle of the Intermittent Vacuum Infusion Machine
Excluding the conveyor belt model, this machine consists of a main body, a vacuum chamber, a thermal sealing device, a lid lifting mechanism, a vacuum system, and electronic controls.
The vacuum space (Figure 11-48) is where sealing takes place. Figure 11-49 illustrates the vacuum inflation sealing cycle, which consists of:
a. Vacuum pump: Evacuate the vacuum chamber and the lower air film chamber to equalize pressure, prevent the film from bulging, and avoid vacuum loss. Vacuum level target: –0.097 to –0.0987 MPa.
b. Inflation: After closing vents A and B, inert gas is introduced at 3–6 kPa to expand the package, controlled by a timer. The vacuum in the chamber is maintained between –0.097 and –0.094 MPa. Inflation is skipped for cooked products that undergo subsequent sterilization.
c. Sealing and Heat Dissipation: With B-ventilation hole open, atmospheric pressure presses the film onto the sealing pad while the sealing bar is heated to prevent sticking. After sealing, power is cut to allow cooling while pressure is maintained, ensuring a strong seal.
d. Vent Air fills the vacuum space, equalizing the pressure to open the lid and remove the sealed package.
Rotary Vacuum Packaging Machine
Figure 11-51 depicts a rotary vacuum packaging machine with a filling station and a vacuum turntable. Mechanical arms transfer the filled bags between stations.
The filling rotary table includes six stations for bag supply, printing, opening, solid filling, and liquid injection. The vacuum rotary table has 12 vacuum chambers where vacuum pumping, heat sealing, cooling, and unloading occur in sequence, achieving up to 40 bags per minute. The solid dosage must correspond to the filling station.
Thermoforming Packaging Machine
Thermoforming packaging uses thermoplastic sheets to form containers, which are then filled and sealed with film or sheets. Common forms include trays, blister packs, skin packs, and soft-film formed packaging (Figure 11-52). Table 11-6 compares their characteristics.
Thermoforming equipment ranges from manual to fully automatic. The process involves clamping, heating, pressing/vacuuming, cooling, and unloading. This machine produces packaging containers only; filling and sealing require separate equipment.
The fully automatic thermoforming machine integrates forming, filling, and sealing, using a wound thermoplastic film for the bottom forming and top sealing. This integration eliminates the need for pre-formed trays, streamlining production for food manufacturers. This versatile machine supports a variety of packaging formats shown in Figure 11-52.
Figure 11-53 shows a fully automatic thermoforming machine with components including a film feeder, film guide, lower film preheater, forming, filling, heat sealing, cutting, and control system.
Figure 11-54 outlines the packaging flow: the bottom film is drawn through the heating and forming zone (air pressure, vacuum, or piercing), filled in the filling area, then sealed by the top film. Vacuum or protective gas treatment can be applied before heat sealing. Finally, the package is formed by cross-cutting, longitudinal cutting, and corner trimming. The residual edges are collected by suction or rolling.
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