Two large pieces of industrial machinery and equipment. Their main body color is green. The front of the equipment has a red handwheel and some control switches. The sides of the machine have bearing sections for support and rotation. The top of the machine is equipped with a motor, which is blue in color. On the side of the machine, there is a control panel with some gauges and indicator lights. Both the devices are fitted with a base to ensure that they stand steadily. Overall, both of these machines look very sturdy and professional, and are likely to be critical equipment used in heavy industry or manufacturing.

EVA Foam Production Process Stage III – The Open Milling Stage

In the extensive manufacturing process of Ethylene Vinyl Acetate (EVA) foam, each stage plays a crucial role in determining the quality and properties of the final product. Among these stages, the third phase, known as the “open mixing phase” or the “open mill mixing phase,” is pivotal in further refining the material after the completion of the second phase – the closed mixing phase.

Understanding the Open Mixing Phase

Following the completion of the closed mixing phase, where the semi-finished material undergoes blending in enclosed mixing chambers, it progresses into the open mixing phase. In this stage, the semi-finished material, often in the form of dough-like compounds, is introduced into open mill mixing machines equipped with either two or multiple rolls.

EVA Foam Production Process Stage III – The Open Milling Stage
EVA Foam Production Process Stage III – The Open Milling Stage

The Process of Open Mixing

1. Introduction of Semi-Finished Material

The semi-finished material, having undergone preliminary mixing and blending in the closed mixing phase, is fed into the open mixing machines. This material typically consists of EVA resin compounded with various additives, such as fillers, plasticizers, and curing agents, depending on the desired properties of the final foam product.

2. Continuous Mixing and Shearing

Once inside the open mixing machine, the material undergoes a series of continuous mixing and shearing processes facilitated by the rotating rolls. These rolls can be set at different speeds and configurations to achieve specific mixing requirements. The rotational movement of the rolls continuously kneads, compresses, and stretches the material, ensuring thorough dispersion of additives and uniform distribution of components throughout the compound.

3. Achieving Homogeneity and Desired Patterns

The primary objective of the open mixing phase is to achieve homogeneity within the material, ensuring that all components are uniformly dispersed. Additionally, this phase allows for the creation of specific patterns or textures within the material, which may be desirable for aesthetic or functional purposes. By adjusting the parameters of the mixing process, such as roll speed, temperature, and pressure, manufacturers can control the appearance and properties of the final foam product.

4. Monitoring and Quality Control

Throughout the open mixing phase, operators closely monitor the process parameters and conduct quality control checks to ensure consistency and adherence to specifications. Parameters such as temperature, mixing time, and roll gap are meticulously controlled to optimize mixing efficiency and product quality. Any deviations or irregularities in the mixing process are promptly identified and addressed to maintain product integrity.


The open mixing phase of EVA foam production represents a critical stage where semi-finished materials are further refined to achieve the desired properties and characteristics of the final product. Through continuous mixing and shearing in open mill mixing machines, manufacturers can ensure homogeneity within the material and create specific patterns or textures as needed. By adhering to strict process controls and quality assurance measures, manufacturers can consistently produce high-quality EVA foam products that meet the diverse needs of various industries.

FAQ (Frequently Asked Questions)

Q: What is the open mixing phase in EVA foam production?

A: The open mixing phase is a crucial stage in the manufacturing process of Ethylene Vinyl Acetate (EVA) foam, where semi-finished materials are further refined in open mill mixing machines to achieve uniform dispersion of additives and desired material properties.

Q: What are the key objectives of the open mixing phase?

A: The primary objectives of the open mixing phase include achieving homogeneity within the material, creating specific patterns or textures, and ensuring consistency and quality control throughout the mixing process.

Q: How is quality control maintained during the open mixing phase?

A: Quality control during the open mixing phase involves closely monitoring process parameters such as temperature, mixing time, and roll gap, and promptly addressing any deviations or irregularities to maintain product integrity.

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