How to produce disposable plastic cups?

The production of disposable plastic cups is a highly automated and continuous process, primarily using polypropylene as the raw material.

Characteristics of this material:

• Polypropylene Cups: Usually opaque or semi-transparent, with good heat resistance (up to 100°C), suitable for holding hot water or hot beverages, and have a relatively hard feel.

The core production process is thermoforming, with the specific steps detailed below:

Production Flow Detailed Explanation

Step 1: Raw Material Preparation and Batching

1. Plastic Pellets: The main plastic raw material (PP pellets) is poured into a storage hopper.
2. Adding Masterbatch: Depending on product requirements, auxiliary materials such as color masterbatch (to impart color), toughening agents, or clarifying agents can be added.
3. Mixing: The primary material and additives are automatically proportioned and mixed uniformly via an automatic feeding system, then sent to the next stage—the extruder.

Step 2: Plastic Sheet Extrusion

1. Melting and Plasticizing: The mixed raw materials are fed into an extruder. Inside the extruder, equipped with heaters and a screw, the materials melt into a viscous fluid under high temperature (approximately 200°C) and the shear force of the screw.
2. Filtration and Flattening: The molten plastic passes through a fine filter to remove impurities, and is then extruded through a flat T-die, forming a continuous, uniform plastic film.
3. Cooling and Sizing: This hot thermoplastic film is immediately fed into a set of cooling rollers (typically three large rollers) where      it is rapidly cooled, calendared, and sized into a plastic sheet with precise thickness and a smooth surface.

Step 3: Sheet Conveying and Heating
The formed plastic sheet is conveyed via a belt into the thermoforming machine. Before entering the mold area, the sheet passes through a heating zone, typically using far-infrared heaters, which heats the sheet precisely above its glass transition temperature, making it soft and easy to stretch without melting or dripping.

Step 4: Thermoforming (Core Step)
The heated and softened sheet is quickly transferred into the closing molding station.

Molding Method: Positive Mold Forming (Plug-Assist Forming)

• A raised "plug" (positive mold)      first moves downward, pre-stretching the sheet into the cavity of the      negative mold.
• Then, compressed air is injected between the      mold and the sheet, pressing the sheet tightly against the positive mold      to replicate the cup's shape.
• Advantage: The cup wall thickness is more uniform, especially suitable for deep-draw products.

During this process, multiple cups are formed simultaneously on a single sheet to improve efficiency.

Step 5: Punching and Trimming
The molded sheet now consists of interconnected "cup trees." It then enters the punching station:

• A punching die with sharp blades stamps down, cutting the individual formed cups from the sheet and simultaneously trimming the cup rim.
• The cut-out cups are the finished products, while the remaining scrap material (skeleton) is collected by a dedicated recycling system (e.g., a crusher).

Step 6: Scrap Recycling
The collected scrap material is crushed into small granules. These are mixed into the new raw material at a certain ratio (typically 30%-40%) and fed back into the extruder for reuse. 

This significantly reduces production costs and material waste.

Step 7: Post-Processing and Packaging

1. Stacking: The individually punched cups are neatly stacked by an automatic cup stacking machine.
2. Packaging: The stacked cups are packaged in plastic bags or shrink film, placed into cartons, and are ready for dispatch.

Key Equipment List

• Plastic Extruder: Used for melting raw materials and extruding the sheet.
• Thermoforming Machine: The core equipment, performing sheet heating, forming, and punching.

Quality Control Points
Throughout the production process, the following parameters must be strictly controlled to ensure product quality:

• Raw Material Quality: Ensure plastic pellets are pure and free of impurities.
• Processing Temperature: Extrusion and heating temperatures must be precise; too low causes poor plasticization, too high causes material degradation.
• Sheet Thickness: Uniform thickness is crucial for consistent cup strength and appearance.
• Mold Precision: The mold's finish and dimensions directly determine the cup's shape, capacity, and appearance.
• Punching Quality: Ensure the cup rim is smooth and free of burrs.

In summary, the production of disposable plastic cups is a process that transforms plastic pellets into standardized products rapidly and on a large scale through steps like melting, forming, and cutting.It is a technologically mature and highly efficient process.