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Learn how EVA midsoles and shoe soles are manufactured using CP, CMP, DP and IP processes. Compare production flow, product quality, efficiency, cost and suitable footwear applications.

What Is EVA and Why Is It Used in Footwear?

EVA, short for Ethylene-Vinyl Acetate, is one of the most widely used lightweight foam materials in the footwear industry.

Depending on the formulation and molding process, EVA can provide different levels of:

Density and product weight

Hardness and softness

Flexibility and rebound

Compression resistance

Shrinkage control

Surface appearance

EVA is commonly used in:

Sports shoe midsoles

Lightweight outsoles

Slippers and sandals

Insoles and footbeds

One-piece molded footwear

In footwear manufacturing, the term Phylon generally refers to EVA foam that has been compression-molded into a more refined and dimensionally controlled component.

However, not all EVA soles are manufactured in the same way. Different factories may use CP, CMP, DP or IP processes according to the required product structure, production volume, appearance and cost target.

Factory terminology may vary by country and manufacturer. In this article, CP, CMP, DP and IP are used as common production classifications.

Why Are There Different EVA Midsole Manufacturing Processes?

One EVA production method cannot meet every footwear requirement.

For example:

A premium sports midsole may require fine surface details and precise dimensions.

A mass-market slipper may prioritize lower cost and faster production.

A complex one-piece sole may require direct injection molding.

A lightweight, high-rebound product may require a more carefully balanced compound and molding route.

The selected EVA manufacturing process directly affects:

Production efficiency

Tooling requirements

Labor input

Dimensional accuracy

Surface quality

Material utilization

Final cost per pair

More importantly, each production method requires a suitable EVA compound formulation. A compound developed for compression molding may not deliver the same results in direct injection production.

1. Traditional Two-Stage Compression Molding — CP

CP is a traditional method used to manufacture compression-molded EVA or Phylon midsoles.

Typical CP Production Flow

EVA resin and functional additives are mixed.

The compound is prepared into sheets, slabs or preforms.

The material undergoes primary foaming.

The prefoamed material is cut according to the required weight and shape.

The preform is placed into the final mold.

Secondary compression molding controls the final dimensions, surface and structure.

The finished component is cooled, trimmed and inspected.

Advantages of the CP Process

Good dimensional accuracy

Refined surface appearance

Suitable for detailed textures and patterns

Better control of the final product shape

Appropriate for medium- and high-end footwear components

CP Production Considerations

Because CP involves several production stages, it normally requires:

More labor

Longer production time

Additional cutting and trimming

Higher processing cost than one-step methods

CP is therefore commonly selected when product quality, dimensional control and appearance are more important than achieving the lowest possible manufacturing cost.

2. Controlled Pre-Foaming and Secondary Compression — CMP

CMP is another two-stage EVA molding route. It generally uses a controlled pre-foaming stage followed by compression molding in the final product mold.

The objective is to establish a stable foam structure before refining the final dimensions and surface appearance.

Typical CMP Production Flow

EVA materials are mixed and compounded.

The compound undergoes controlled pre-foaming.

The prefoamed material is prepared according to the required product weight.

It is placed into the final compression mold.

Heat and pressure complete the final shaping process.

The product is cooled, finished and inspected.

Advantages of CMP

Stable product dimensions

Good foam-cell consistency

Flexible surface and structural design

Suitable for products with higher appearance requirements

Better control over final molded shape

CMP Production Considerations

CMP requires accurate matching between the pre-foaming and secondary compression stages.

An unsuitable EVA compound may cause:

Insufficient mold filling

Excessive shrinkage

Density variation

Poor surface definition

Inconsistent hardness

The formulation must therefore match the required pre-expansion ratio and final compression conditions.

3. One-Step Compression Molding — DP

The DP process simplifies production by completing foaming and compression molding in one main cycle.

Prepared EVA compound or accurately weighed preforms are placed directly into the mold, where the material expands and forms the finished component.

Typical DP Production Flow

EVA compound is prepared.

The required material weight is measured.

The material is placed directly into the mold.

Foaming and molding take place in one production cycle.

The finished component is cooled, trimmed and inspected.

Advantages of DP

Shorter production flow

Reduced labor requirements

Better material utilization

Lower overall processing cost

Suitable for high-volume manufacturing

DP Production Considerations

Compared with two-stage compression molding, DP may provide less flexibility in:

Complex surface design

Precise dimensional control

Detailed product structures

Multi-component product development

DP is often suitable for manufacturers seeking a practical balance between quality, production efficiency and cost.

4. Direct EVA Injection Molding — IP

IP refers to the direct injection molding of EVA compounds.

The prepared EVA material is plasticized, injected into the mold and foamed into the required footwear component. Depending on the equipment and product design, IP can be used for midsoles, outsoles, sandals, slippers and complete molded footwear products.

Typical IP Production Flow

A suitable EVA injection compound is prepared.

The compound is fed into the injection system.

The material is plasticized and injected into the mold.

Foaming and crosslinking take place inside the mold.

The mold opens and the expanded component is removed.

The product is stabilized, cooled and finished.

Advantages of IP

High production efficiency

Greater automation potential

Consistent material dosing

Suitable for large-volume orders

Reduced manual handling

Capable of producing integrated molded structures

IP Production Considerations

Direct injection molding places specific requirements on the EVA compound, including:

Suitable material flow

Controlled foaming and crosslinking timing

Stable expansion behavior

Predictable mold shrinkage

Consistent surface and color performance

Using a general compression-molding formulation in an injection process may lead to unstable production results.

CP vs CMP vs DP vs IP: Quick Comparison

Which EVA Manufacturing Process Is Better?

There is no single EVA process that is best for every footwear product.

The correct choice depends on:

Product structure

Target market

Required appearance

Order quantity

Production cost target

Hardness and density

Rebound requirements

Dimensional tolerance

Choose CP or CMP when:

Surface appearance is important

Precise dimensions are required

The design contains detailed textures or structures

The product is positioned in a medium- or high-end market

Choose DP when:

Production simplicity is a priority

The product structure is relatively straightforward

Cost control and material utilization are important

Large-volume output is required

Choose IP when:

Higher automation is required

Production volume is large

Integrated molding is preferred

The factory requires stable and repeatable material dosing

Why EVA Compound Formulation Must Match the Process

The manufacturing method is only one part of the final result.

EVA compound performance is also influenced by:

EVA resin grade and VA content

Foaming system

Crosslinking system

Fillers and polymer modifiers

Target hardness and density

Required expansion ratio

Color system

Shrinkage-control requirements

For example, a compound that performs well in a two-stage compression process may not have the correct flow or reaction balance for direct injection molding.

An unsuitable formulation can cause:

Incomplete mold filling

Excessive shrinkage

Surface defects

Uneven foam cells

Hardness fluctuations

Inconsistent product weight

The correct production process requires the correct EVA compound—not simply the same material used in a different machine.

Customized EVA Compounds for Different Production Routes

At RELYONTECH, EVA compounds can be developed according to the customer’s actual product and production requirements.

Customization may include:

CP, CMP, DP or IP manufacturing route

Target density

Required hardness

Expansion ratio

Rebound and flexibility

Color and appearance

Shrinkage requirements

Final product positioning

We do not believe that one EVA formulation can fit every sole, machine or market.

Tell us what product you want to manufacture, and we will match the material system to your target result.

Frequently Asked Questions

What is the difference between EVA and Phylon?

EVA is the polymer material. Phylon generally refers to EVA foam that has been compression-molded, often through pre-foaming and secondary compression.

Which process produces the best surface quality?

Two-stage compression routes such as CP and CMP generally provide better control over product dimensions, textures and surface appearance.

Which EVA process has the lowest production cost?

DP and IP can reduce manual processing and production stages. However, the actual cost depends on product design, production volume, tooling, labor and material formulation.

Can the same EVA compound be used for CP and IP?

Not necessarily. Compression molding and injection molding require different flow, foaming and crosslinking behavior. The compound should be matched to the production process.

Why do EVA midsoles shrink after molding?

Shrinkage can be influenced by the expansion ratio, crosslinking level, internal foam structure and overall formulation balance. A properly designed EVA compound can improve dimensional stability.

Can EVA color, hardness and density be customized?

Yes. Color, hardness, density, flexibility, rebound and expansion ratio can all be adjusted according to the customer’s product requirements.

Conclusion

CP, CMP, DP and IP each offer different advantages in EVA midsole and sole manufacturing.

The most suitable process depends on the required balance between:

Product quality

Manufacturing efficiency

Surface appearance

Investment

Cost per pair

However, the manufacturing process alone does not determine the final result.

A stable EVA footwear product requires the correct combination of:

Material formulation + production process + target product requirements

Work with RELYONTECH

RELYONTECH provides customized solutions for:

EVA injection compounds

Compression-molding EVA compounds

EVA chemical packages

Lightweight sole materials

Color-matching systems

Formulation and production support

Whether you manufacture sports midsoles, slippers, sandals or lightweight soles, we can develop a material solution according to your required process, hardness, density and performance.

📩 Contact us for samples, quotations or technical discussions:
salerelyon@gmail.com

🌐 www.relyon-tech.com

About RELYONTECH

RELYONTECH provides one-stop solutions for PVC & EVA compounding and footwear production, helping manufacturers improve product performance, reduce cost, and achieve more stable production.

E-mail: salerelyon@gmail.com

Phone/WhatsApp: +86 15759875789

Address: No;40 7th Qianshan District, Neikeng Town, Jinjiang City, Quanzhou,Fujian, China