The difference between negative pressure thermoforming machines and positive/negative pressure thermoforming machines

A positive and negative pressure integrated molding machine consists of two independent systems: a positive pressure system and a negative pressure system. These two systems can be controlled independently. A negative pressure integrated molding machine, however, only has a negative pressure system and no positive pressure system.

The differences between these two types of machines are:

1. Different specific concepts

Positive and negative pressure vacuum forming refers to the process of using positive and negative gas forces to blow thermoplastic material into a mold at a certain temperature to form the desired shape. Generally, in addition to negative pressure, there is also positive pressure. When the machine is running, pressure is drawn from the bottom to the top (i.e., a vacuum is created at the bottom), and pressure is added at the top, thus creating positive and negative pressure.

Negative pressure molding involves pumping the raw material into a specific mold, and then using a vacuum and pressurization mechanism to solidify and preserve the material within the mold to obtain the desired shape. A negative pressure molding machine only creates a vacuum at the bottom; there is no pressure at the top, hence the name "negative pressure machine."

2. Different Driving Methods

Positive and negative pressure molding machines use a hydraulic drive, meaning the thrust of a hydraulic cylinder drives the pressure in the mold, controlling the pressure and duration to achieve the molding process.

Negative pressure molding machines, on the other hand, use a vacuum adsorption method, using the suction force of a vacuum adsorber to hold the mold in place. A vacuum pump then removes air from the vacuum adsorber, creating a vacuum that allows for molding.

3. Different Working Principles

Positive and negative pressure molding machines work by using a mold with an inner and outer shell structure. Positive and negative pressures are applied simultaneously within the mold. When these pressures act on the plastic material inside the mold, the material stretches and contracts, achieving the molding process.

Negative pressure molding machines work by using the pressure within the mold to control the shrinkage of the plastic material, thus achieving the molding process. Negative pressure molding machines do not require positive pressure; only negative pressure is applied. The plastic material shrinks in response to changes in the applied pressure, achieving the molding process.

4. Different Specific Applications

Positive and negative pressure molding machines are multi-functional plastic molding machines that can perform both positive and negative pressure molding simultaneously. Positive and negative pressure integrated molding machines are mainly used in the electronics industry for the production of electronic components and high-precision parts, while negative pressure integrated molding machines are mainly used for the production of general-purpose plastic parts.

5. Different Demolding Degrees

Positive and negative pressure vacuum forming machines use positive pressure heating airflow to transfer heat to every part of the workpiece. The airflow carries heat during pressurization, ensuring thorough heat transfer and making the workpiece less prone to demolding.

Negative pressure vacuum forming machines, on the other hand, only transfer heat to the surface of the workpiece. The heat transfer to the sides and grooves is less comprehensive compared to positive and negative pressure machines, resulting in relatively weaker adhesion. Products are more prone to edge peeling after 2-3 years.

6. Different Functions

Positive and negative pressure integrated molding machines can be used not only for plasticizing but also for composite and thermoforming, while negative pressure integrated molding machines are only for plasticizing.

The emergence of positive and negative pressure integrated molding machines and negative pressure integrated molding machines has greatly improved the efficiency of plasticizing and broadened the application scope of the plastics processing field. These two types of molding machines can operate through automatic control systems, significantly improving the efficiency of plastic processing and making outstanding contributions to the development of the plastics industry.