How are cups produced using thermoforming molds?

The thermoforming mold is the core of the entire production process. 

Its task is to shape the heated and softened plastic sheet into a specific cup form.

Its working principle can be broken down into several key stages and the collaborative action of components.

Core Objective
To transform a flat plastic sheet into a three-dimensional cup shape through heating, stretching, and cooling.

Basic Types of Molds and Their Working Principles

In disposable plastic cup production, the "positive mold (plug-assist forming)" is most commonly used.

Positive Mold Forming - Mainly Used for Deep-Drawn Products (e.g., Cups)
This is the mainstream method for producing cups, as it ensures more uniform wall thickness, particularly at the bottom and corners.

Working Principle Steps:

1.Clamping and Heating: The plastic sheet is tightly clamped and fixed by the mold frame (clamping frame) and heated to a soft state.

2.Pre-Stretching (Key Step):

The positive mold (plug) above the mold—a convex mold resembling the inner wall of the cup—moves downward.

The positive mold first contacts and stretches the middle of the sheet, pre-stretching it to a position close to the final depth. This action pre-distributes the material, preventing the sheet from being over-stretched, thinning, or even tearing during subsequent blowing.

3.Air Pressure Forming:

Once the positive mold reaches the predetermined position, compressed air is introduced between the positive mold and the sheet.

The compressed air presses the pre-stretched sheet tightly against the surface of the positive mold, accurately replicating all the details of the positive mold (such as the cup's contour and reinforcing ribs).

In some designs, a vacuum may also be applied from the bottom of the negative mold simultaneously, using atmospheric pressure to assist the sheet in adhering closely to the mold.

4.Cooling and Demolding:

Once the sheet fully conforms to the mold, the cooling system activates immediately. The mold interior has cooling channels where circulating cold water rapidly removes heat, solidifying the plastic.

Then, the positive mold retracts upward, and reverse compressed air (demolding air) is blown in to help release the formed cup from the positive mold.

Finally, the sheet frame releases, and the sheet advances to the next station, entering the punching process.

Advantages:

• Uniform wall thickness distribution, especially at the bottom and side walls, which are less prone to thinning.
• Highly suitable for producing deep products, such as cups and instant noodle bowls.