Introduction: Controlling Internal Defects in Aluminum Die Castings

Die casting shrinkage porosity is one of the most common internal quality challenges in aluminum die casting, especially for OEM components requiring high strength, pressure tightness, and long-term reliability.achieving a good surface finish is only One of the most critical internal quality challenges in OEM manufacturing is die casting shrinkage porosity.

For many OEM applications, internal quality can be equally important, especially when components require:

• Pressure tightness
• Structural strength
• Long-term durability
• Stable performance under vibration or mechanical loads

One of the common internal defects in aluminum die castings is shrinkage porosity.

Unlike surface defects, internal shrinkage may remain invisible during visual inspection and only become apparent after:

• CNC machining
• Air leakage testing
• Hydraulic pressure testing
• Final assembly

For components with thick-wall sections or localized heat accumulation areas, local squeeze technology (hydraulic squeeze pin technology) can be an effective method to reduce shrinkage risks in critical areas.

However, squeeze pin technology is not a universal solution for all casting problems. Its effectiveness depends on part geometry, alloy characteristics, mold design, and overall process control.

1. Understanding Die Casting Shrinkage Porosity in Aluminum Components

During the high-pressure die casting process, molten aluminum fills the mold cavity at high speed and rapidly solidifies.

As the aluminum alloy changes from liquid to solid state, material naturally contracts.

Under normal conditions, the feeding effect from the remaining molten metal can compensate for this shrinkage.

However, problems may occur in areas with:

• Thick wall sections
• Large material accumulation
• Sudden changes in wall thickness
• Poor feeding conditions
• Local hot spots during solidification

In these areas, solidification may happen before sufficient liquid metal reaches the shrinking zone, resulting in internal voids.

These defects are commonly known as:

Shrinkage porosity

Why Internal Porosity Matters for OEM Components

Reduced Mechanical Performance

Internal voids can create stress concentration points, reducing the ability of components to withstand repeated loading or impact.

Pressure Leakage Risk

For components requiring sealing performance, internal porosity may cause leakage during:

• Air tightness testing
• Hydraulic pressure testing
• System operation

Machining-Related Quality Issues

Some internal defects remain hidden until machining removes the surface material.

This can lead to:

• Unexpected rejection
• Additional processing costs
• Production delays

Therefore, controlling internal casting quality is critical for demanding OEM applications.

Internal Structure Comparison: Conventional Die Casting vs. Local Squeeze Optimization

 

2. How Local Squeeze Pin Technology Works

Applying Additional Pressure to Targeted Areas During Solidification

Local squeeze technology uses hydraulic squeeze pins integrated into the die casting mold to provide additional pressure in specific areas where shrinkage risk exists.

During the semi-solidification stage, the squeeze pin applies localized pressure to directly prevent die casting shrinkage porosity in critical thick sections.

This additional pressure helps:

• Compensate for local solidification shrinkage
• Improve material density in critical areas
• Reduce the formation of shrinkage cavities
• Improve casting consistency

 

• 
• Unlike general injection pressure, squeeze pin technology provides localized pressure compensation rather than applying additional pressure throughout the entire casting.

When Is Local Squeeze Technology Suitable?

Local squeeze technology is commonly considered when:

• A specific area has a high risk of shrinkage
• The component contains thick sections
• Local mechanical performance is critical
• Pressure tightness is required in certain areas
• CNC machining may expose internal defects

The technology is usually applied selectively based on part requirements.

Local squeeze pin technology is one of the most effective solutions to reduce die casting shrinkage porosity in thick-wall sections.

3. Local Squeeze Technology Is Part of a Complete Die Casting Solution

Squeeze pins alone cannot solve every casting issue.

Before applying local squeeze technology, engineers must first evaluate the overall casting process, including:

• Part design
• Alloy selection
• Mold structure
• Filling behavior
• Cooling conditions

Some common defects require different solutions.

For example:

Casting Issue	Typical Solution
Shrinkage porosity in local thick areas	Local squeeze technology
Poor filling / misrun	Runner and gate optimization
Cold shut defects	Filling temperature and flow adjustment
Gas porosity	Improved venting and process control
Dimensional instability	Mold and cooling optimization

A successful die casting project requires selecting the right solution for the actual defect mechanism.

4. Key Process Factors in Controlling Die Casting Shrinkage Porosity

Squeeze Pin Location Design

The position of the squeeze pin is one of the most important factors.

Engineers need to identify potential shrinkage areas through:

• Part structure analysis
• Mold flow simulation
• Solidification analysis

The squeeze pin should be placed where additional pressure can effectively improve local feeding conditions.

Pressure and Timing Control

Important parameters include:

• Squeeze pressure
• Delay time
• Holding time

The timing must match the solidification behavior of the aluminum alloy.

Applying pressure too early or too late may reduce the expected improvement.

Integration with Filling and Cooling Optimization

Local squeeze technology works best when combined with:

• Optimized runner design
• Proper gate location
• Injection parameter control
• Mold temperature management
• Cooling system optimization

The goal is not only to add a squeeze pin, but to create a balanced and stable casting process.

5. Manufacturing Benefits of Properly Applied Local Squeeze Technology

Proper application of squeeze pins directly addresses die casting shrinkage porosity and improves structural integrity.

Proper implementation of squeeze pins directly reduces die casting shrinkage porosity, yielding measurable quality improvements:

Typical improvements include:

Performance Area	Conventional Process	With Local Squeeze Applied to Critical Areas
Local shrinkage risk	Higher risk in thick sections	Reduced risk in targeted areas
Internal density	Possible localized defects	Improved local structure consistency
Pressure tightness	Potential leakage issues	Improved reliability
Mechanical performance	Limited by internal defects	Better consistency

Actual results depend on:

• Aluminum alloy type
• Part design
• Wall thickness
• Mold design
• Process parameters

Engineering validation is required for each OEM project.

6. Supporting Manufacturing Controls for Reliable Die Cast Components

Local squeeze technology is only one element of a complete die casting quality system.

RuiYu supports OEM projects through integrated aluminum die casting services, including mold development, die casting production, machining, and surface finishing.

Engineering and Mold Development

A reliable die casting process starts with proper die casting mold development.

Before production, engineers evaluate:

• Part design feasibility
• Filling behavior
• Solidification patterns
• Potential hot spots
• Mold structure optimization

Through DFM analysis and mold flow simulation, potential casting risks can be identified and reduced before tooling production.

Die Casting Process Optimization

Including:

• Filling parameter adjustment
• Mold temperature control
• Cooling optimization
• Defect analysis

Secondary Processing and Quality Control

Including:

• CNC machining
• Surface finishing
• Assembly
• Dimensional inspection
• Functional testing

This integrated approach helps customers achieve stable quality from prototype development to mass production.

7. Applications Where Local Squeeze Technology Can Provide Benefits

Local squeeze technology is most valuable for aluminum die cast components where specific areas require improved density or reliability.

Typical examples include:

Electric Motor Components

Examples:

• Motor housings
• End covers
• Structural supports

Requirements:

• Dimensional stability
• Heat dissipation
• Long-term operating reliability

Industrial Equipment Components

Examples:

• Pump housings
• Valve bodies
• Mechanical housings
• Structural brackets

Requirements:

• Pressure resistance
• Mechanical strength
• Consistent production quality

Complex OEM Aluminum Components

Applications requiring:

• Lightweight design
• High rigidity
• Complex geometry
• Reduced machining defects

may benefit from optimized die casting solutions.

Why Choose RuiYu for Complex Die Casting Projects?

Reliable die casting requires more than equipment capability.

RuiYu helps OEM customers develop metal components through:

• Engineering support
• Mold development coordination
• Die casting process optimization
• CNC machining
• Surface finishing
• Assembly solutions

With more than 20 years of die casting experience, RuiYu focuses on solving manufacturing challenges and delivering reliable OEM components.

Frequently Asked Questions

Facing die casting shrinkage porosity or pressure leakage challenges in your aluminum components? Contact RuiYu’s engineering team today.

If your aluminum die cast parts experience:

• Internal shrinkage issues
• Pressure leakage problems
• Machining defects
• Strength limitations

RuiYu can help evaluate your design and recommend suitable manufacturing solutions.

Send your CAD drawings (STEP/IGES files) to RuiYu engineering team for DFM review and die casting process recommendations.