The sealing method of polypropylene film paper cup packaging machine mainly adopts the heat sealing technology and combines with automatic control to achieve efficient sealing. Specific features and implementation methods are as follows:
I.Core Sealing Technology: Thermal Pressure Sealing Principle
The seal is formed by heating the PP film to a molten state using a heating heating devices,such as an electric heating plate, roller or high frequency electrode, and then applying mechanical pressure to fuse the film layers together. Polypropylene material can be softened and bonded quickly after heating, solidified and maintain sealable after cooling due to its excellent thermoplastic properties.
It's a common form of heat seal.
Plate-type heat sealing: Plate Thermal Seal Direct Pressure Film, suitable for polyethylene and polypropylene composite film, simple structure and fast sealing speed.
Roller Hot Seal: A pair of heating rollers continuous rolling film, suitable for high-speed production line, such as paper cup popcorn packaging machine.
Ring type heat seal: Ring type heat seal sandwiched between moving ring type steel belts, heating blocks inside the steel belts provides heat, while cooling block forms seal, suitable for polypropylene film prone to thermal deformation.
Pulse heat sealing: A nickel-chromium alloy strip briefly electrified, producing a high temperature that melts and binds the film, freezes and releases it, suitable for situations requiring high sealing strength (e.g. liquid packaging).
II. Automatic control and Sealing Accuracy PLC control system
Modern paper-cup packaging machines (such as paper-cup popcorn packaging machine) adopts multifunctional PLC control system. The temperature, pressure, speed and other parameters can be set through the touch screen to ensure the consistency of the seal. For example:
Temperature control: polypropylene films are usually sealed at temperatures between 160 and180 degrees Celsius. PLC can precisely regulate the temperature of the heating block to prevent the film from contracting or gelatinizing due to overheating.
Pressure adjustment: The pneumatic device provides stable pressure (e.g. 0.65-1.2 Mpa) to ensure sealing strength and prevent paper cups damage.
Cursor positioning: The photoelectric sensor automatically identify the color mark on the packaging film, accurately locate the sealing position, and control the error to ±1mm.
Mold adaptability
All-aluminium moulds (CNC precision engraving) are up to 0.001mm in accuracy and support a wide range of specifications from "1/ 1" to "6/ 1." The moulds can be quickly changed depending on the shape of the cup (e.g. round, square, alien paper cups).
III. Sealing Materials and Processes
Properties of PP films
PP (polypropylene) film has the advantages of high temperature resistance, puncture resistance and high transparency. However, it should be noted that:
Single-component polypropylene film: Pulse heat sealing or low-temperature long-time sealing is required because it is easy to melt and thin when overheated.
PP composite film: such as PP/PE composite film, the low melting point of PE layer can be utilized to achieve low low-temperature sealing, reducing the risk of PP layer deformation.
Sealing Process Optimization
Cooling and setting: after sealing The ring band type sealing machine through the cooling block to quickly cool, preventing the film shrinkage.
Anti-adhesion treatment: heating plate or heating roller surface coated with polytetrafluoroethylene (PTFE), to avoid film adhesion, extending the equipment lifespan.
